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Abstract
Experimentos físico-químicos en las areas de análisis, formación compleja, electroquímico, cinética, fotoquímica, espectroscopía, termodinámica y otras.
... Reactions of amines with fluorescamine were found to be pH-dependent [10]. It was also found that fluorescence was developed only in alkaline medium and completely disappeared in acidic medium [10]. ...
... Reactions of amines with fluorescamine were found to be pH-dependent [10]. It was also found that fluorescence was developed only in alkaline medium and completely disappeared in acidic medium [10]. ...
... The stoichiometry of the reaction between OXY and fluorescamine was studied adopting the limiting logarithmic method [10]. The RFI of the product was alternatively measured in the presence of excess of either fluorescamine or OXY. ...
Simple and sensitive second derivative and synchronous spectrofluorimetric methods have been developed and validated for the quantitative determination of oxytocin and ergometrine maleate in their pure and combined dosage forms. The methods are based on the derivatization reaction of oxytocin with fluorescamine reagent, which yielded a highly fluorescent compound measured at 486 nm after excitation at 390 nm. Ergometrine was directly measured in combination with oxytocin, since it exhibits native fluorescence at 421 nm after excitation at 300 nm. Quantitation of oxytocin in presence of ergometrine was also successful at 482 and 477 nm using second derivative and synchronous spectrofluorimetry, respectively. Different experimental parameters were studied and optimized. The relative fluorescence intensity versus concentration plot was rectilinear over the range of 0.04-0.75 and 5-100 ng/mL for oxytocin and ergometrine, respectively. The methods were successfully applied for the determination of both drugs in their prepared combined ampoules. The methods were validated and compared with the reference chromatographic method; they revealed good accuracy and reproducible results. The proposed methods showed high accuracy and sensitivity, with no requirement of multiple steps or previous chemical separation.
... Earlier, we studied complexes of d-metals with the described ligands and showed the fundamental differences and advantages of this type of substitution [26,31]. It was shown that the presence of aromatic fragments led to compounds with good solubility in most organic solvents, and their massiveness was compensated for by the presence of oxygen bridges, which provided the molecules with flexibility in space, thereby contributing to aggregation stability. ...
... The fluorescence decay of phthalocyanines 4-7 upon the addition of benzoquinone (BQ) in chloroform, acetone, and DMF was found to obey Stern-Volmer kinetics, which was consistent with diffusion-controlled bimolecular reactions [31]. Benzoquinone is frequently used to determine the fluorescence quenching of phthalocyanine solutions due to its strong affinity for electrons, as well as the high energy of the lowest excited state (higher than the energy of the excited singlet state of metal phthalocyanines), which makes energy transfer from the complex to BQ extremely unlikely. ...
Novel metal-free and Mg(II) [3/4-(3,4-dicyanophenoxy)phenoxy]-substituted phthalocyanines were obtained and characterized using NMR, IR, UV-vis spectroscopy, and mass spectrometry. This substitution provided compounds with good solubility in organic media, and thus their spectroscopic and fluorescent properties were studied. The formation of the investigated phthalocyanine complexes with central magnesium ions led to the stabilization of macrocyclic molecules in solution, preventing aggregation through specific and universal solvation. From meta-substitution to para-substitution, insignificant spectroscopic changes were observed. The complexes exhibited higher values of molar light absorption coefficients and fluorescence quantum yields (up to 55%) compared to ligands. The efficiency of both the fluorescence-quenching and singlet oxygen generation processes in the case of magnesium [3/4-(3,4-dicyanophenoxy)phenoxy]phthalocyaninates was found to exceed that of the unsubstituted zinc phthalocyaninate, which suggests the potential applicability of these compounds as PDT sensitizers.
... It was done by applying by continuous variation method [7]. Aliquots (0.1, 0.2, 0.3…and 0.9 ml) of 7.57x10 M of NBD-Cl reagent were added, respectively, followed by addition of 2 ml buffer solution (pH 8.5 + 0.2). ...
... The color was stable for up to 90 minutes. The stoichiometry of the reaction was determined using continuous variation method [7], which revealed a 1:1 ratio of drug and NBD-Cl reagent upon using 7.57 x 10 -4 M solution of both. ...
Aims: To quantify pamidronate in a sensitive and accurate way either in bulk or dosage forms. Methodology: The quantification of this group of drugs is a challenging task as they lack the presence of chromophore groups in their structure. The proposed method depends on the derivatization of the studied drug by its reaction with 4-Chloro-7-nitro-2,1,3-benzoxazole and the product is measured spectrophotometrically at 470 nm. The conditions for the reaction are optimized regarding the volume of the reagent, the optimum pH for the reaction completion, the buffer volume, the optimum temperature for the reaction and the optimum heating time. Results: The studied drug can be determined in the range of 9-30 µg/mL after optimizing the reaction conditions. Method validation is performed according to ICH guidelines and different validation parameters like, linearity, accuracy, precision and robustness are calculated and found to be excellent. Conclusion: The proposed method is accurate, sensitive and can be applied for the routine analysis of pamidronate in quality control laboratories.
... Job's method 45 ...
... Using Job's method of continuous variation, 45 the molar ratio of iron (III) sulfate : diphenylamine was found to be 1:2 (Fig. 2). Therefore, this reagent was prepared in that ratio for subsequent work. ...
... The stoichiometry of the reactions in the two methods was studied adopting the limiting logarithmic method [28]. Plots of log absorbance versus log [reagent] and log [drug] gave straight lines. ...
... Moreover, the reproducibility as well as convenience makes the two proposed methods suitable for routine analysis in quality control laboratories. -The tabulated t and F values are 3.36 and 5.79 at p = 0.05, respectively [28]. J a n u a r y 2 4 , 2 0 1 4 * The tabulated t value is 2.57 at p = 0.05 [27]. ...
The study represents the first report on the development of spectrophotometric methods for determination of ethamsylate (EST) in the presence of hydroquinone as an impurity and/or acidic degradation product. The proposed methods are based on the reaction of EST through it,s secondary amino group either with 1,2-naphthoquinone-4-sulphonate sodium (NQS) at pH 10.7 or 2,4-dinitrofluorobenzene (DNFB) at pH 9.3 to form orange and yellow colored reaction products peaking at 478 and 387 nm for methods (I) and (II), respectively. The different experimental parameters affecting the development and stability of the reaction products in methods (I) and (II) were carefully studied and optimized. The absorbance-concentration plots were rectilinear over the concentration ranges of 2-30 and 2-14 µg mL−1 for methods (I) and (II), respectively. The lower detection limits were 0.13 and 0.19 µg mL−1 and the lower quantitation limits were 0.44 and 0.63 µg mL−1 for methods (I) and (II), respectively. Both methods were successfully applied to commercial ampoules and tablets.
... The limiting logarithmic method [34] was used to evaluate the stoichiometry of FVS-MBTH complex. Two sets of solutions were performed. ...
A selective kinetic spectrophotometric method has been described for the determination of fluvastatin sodium (FVS) in pure form and capsules. The developed method is based on the oxidative coupling reaction of FVS with 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) in the presence of Ce(IV) in an acidic medium to form colored product followed spectrophotometrically by measuring the increase in absorbance with time at 615 nm. The initial rates, rate constant, fixed absorbance and fixed time methods have been tested for constructing the calibration graphs, and are linear. The most suitable analytical methods were the initial rate and fixed time (at 15 min) methods for determination of FVS in the concentration range of 3.0-36.0 μg/mL with LOD is 0.44 and 0.23 μg/ mL, respectively. The activation energy (Ea), activation enthalpy (ΔH ‡), activation entropy (ΔS ‡) and Gibbs free energy (ΔG ‡) are estimated for the reaction and found to be 33.36 KJ/mol, 30.92 KJ/mol,-271.37 J/K mol and 111.79 KJ/ mol, respectively. The kinetic proposed methods have been further applied to the determination of FVS in capsule formulations and the results tallied well with the label claim. The results were statistically compared with those of a reference method by applying the Student's t-test and F-test. No interference was observed from the concomitant substances normally added to preparations.
... Using the limiting logarithmic method [39], the reaction stoichiometry between the studied drug and NBD-Cl (0.2%) was examined. Two straight lines were obtained from the plots of log [PRD] vs. log A and log [NBD-Cl] vs. log A, and slope values were 0.694 and 0.714 for the two plots, respectively (Fig. 12). ...
In addition to its pure form, three accurate, rapid, and simple methods have been established for determining perindopril (PRD) in its tablet form. At pH 9.0 using a borate buffer, developing the three designated methods was successful according to the reaction between PRD and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) and the formation of a chromogen (with a yellow color) measurable at 460 nm using the spectrophotometric method (Method I). In addition, the produced chromogen was assessed using the spectrofluorimetric method (Method II) at 535 nm following excitation at 461 nm. Afterward, the same reaction product was separated and determined using the HPLC method with fluorescence detection (Method III). A Promosil C18 stainless steel column (Q7 5 mm particle size, 250–4.6 mm) has proven suitable for separation. The mobile phase adjustment was made at pH 3.0, with a 1.0 mL min ⁻¹ flow rate; its composition was methanol-sodium dihydrogen phosphate, 0.02 M (60: 40, v/v). Through concentration ranges of 5.0–60.0, 0.5–6.0, and 1.0–10.0 μg mL⁻¹, the calibration curves were rectilinear for Methods I, II, and III, respectively, with limits of quantification (LOQ) of 1.08, 0.16 and 0.19 μg mL⁻¹ as well as limits of detection (LOD) of 0.36, 0.05 and 0.06 μg mL⁻¹. The developed methods were implemented to estimate PRD in tablets, and a comparison between the obtained outcomes utilizing the developed methods as well as obtained from the official method revealed that they were comparable. The official BP method was based on dissolving PRD in anhydrous acetic acid and titrating with 0.1 M perchloric acid, then the potentiometric determination of the end-point. The designated methods were also implemented in content uniformity testing with satisfying results. The reaction pathway proposal was speculated, and according to ICH Guidelines, the statistical evaluation of the data was performed. The three proposed methods were confirmed to be green, eco-friendly and safe to environment using Green Analytical procedure index (GAPI) method.
Supplementary Information
The online version contains supplementary material available at 10.1186/s13065-023-00964-9.
... The Job's method of continuous variation [27][28][29] and mole ratio [30] were employed to evaluate the stoichiometric ratio of formation reaction. Master equimolar (5×10 -3 mol) aqueous solution of folic acid hydrochloride and NQS were prepared. ...
n this study, simple and sensitive spectrophotometric method for the determination of folic acid (VB9) in pharmaceutical formulations was reported. The proposed method was based on the reaction between folic acid and 1, 2-naphthoquine-4-sulphonate (NQS) at alkaline medium (pH 11) to form deep yellow product. Beer’s law was obeyed in the range of 0.75-10.5 μg/mL of folic acid at maximum wavelength of 436 nm. Under optimized reaction conditions, linear regression equation of the calibration curve was y = 0.048 x + 0.038 (μg/mL) with a linear correlation coefficient of 0.9988.
The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.159 μg/mL and 0.531 μg/mL, respectively. The method was successfully applied to the determination of folic acid in pharmaceutical formulations.
... The stoichiometry of the reaction was studied adopting the limiting logarithmic method [27]. The ratio of the reaction between FA and Fe(III) was calculated by dividing the slope of Fe(III) curve over the slope of the FA curve (Figures 7(a) and 7(b)). ...
A simple and sensitive kinetic spectrophotometric method has been developed for the determination of folic acid (FA) in bulk and pharmaceutical Formulations. The method is based on the oxidation of FA by Fe (III) in sulfuric acid medium. Fe (III) subsequently reduces to Fe (II) which is coupled with potassium ferricyanide to form Prussian blue. The reaction is followed spectrophotometrically by measuring the increase in absorbance at λmax 725 nm. The rate data and fixed time methods were adopted for constructing the calibration curves. The linearity range was found to be 1–20 μg mL ⁻¹ for each method. The correlation coefficient was 0.9978 and 0.9993, and LOD was found to be 0.91 and 0.09 μg mL ⁻¹ for rate data and fixed time methods, respectively. The proposed method has been successfully applied to the determination of FA in formulations with no interference from the excipients. Statical comparison of the results shows that there is no significant difference between the proposed and pharmacopoeial methods
... Job's method of continuous variation and molar ratio method were applied to study the stoichiometric ratio of the ion pair formed [23]. 1 × 10 -3 M of ZMT, 1 × 10 -2 M of MNP and 1 × 10 -3 M of DNP solutions were used. In the molar ratio method a constant volume of 1 × 10 -3 M ZMT solution was treated with varying volume of reagent to obtain a ratio for the ion pair complex (0:1, 0.1:0.9, ...
For the detection of zolmitriptan (ZMT) both in pure form and also in pharmaceutical preparations two simple, rapid and selective colorimetric methods were developed. These methods are completely established or based on the direct formation of charge-transfer complexes between ZMT and m-nitrophenol (MNP) in aqueous medium (ZMT:MNP, 1:1) and 2,4-dinitrophenol (DNP) in ethanol:water (80:20). The developed method involves formation of coloured complexes (1:1) of ZMT with MNP and DNP. The yellow formed complexes were quantitatively measured at 400 and 440 nm for ZMT-MNP and ZMT-DNP, respectively. Beer lambert’s law was followed in different ranges of concentration viz. 3.0–260 μg/mL for MNP and 3.5–120 μg/mL for DNP. Both the Limit of detection and quantitation for MNP were calculated as 0.58 and 1.75 μg/mL, respectively, and for DNP were 0.32 and 0.97 μg/mL, respectively. The procedure was then demonstrated w.r.t accuracy, robustness and selectivity. The procedure performed has been successfully applied for the detection of ZMT in tablets.
... Job's of continuous variation and molar ratio methods were applied to determine the reaction stoichiometry between IRB and dye [42]. In the irst method, a series of IRB−dye solutions was kept at 2.0 mL (0:2, 0. where C IRB +C dye =2×10 −4 M. The reagent was mixed in various proportions and then diluted to volume in a 10 mL calibrated lask with chloroform. ...
Irbesartan (IRB) is one of the drugs used for the treatment of hypertension. The present work develops and validates two methods for the evaluation of irbesartan in bulk and tablets. Sulfonephthalein acid dyes, bromophenol blue (BPB), and bromocresol purple (BCP) were used to produce stable yellow ion-association complexes with the basic drug IRB in dry chloroform. The colored products are quantified spectrophotometrically at their corresponding λmax. The relation between the absorbed signal and the drug concentration was linear up to 45.0 μg mL-1 (n = 6, r ≥ 0.9998). LOD reaches 40 ng mL-1. The composition of the ion associates was found 1:1 by Job’s and mole ratio methods. Application of the suggested methods to dosage forms is presented with percentage recoveries ranging from 99.33% to 101.67%. The results of the analysis were validated statistically and compared with the official method. No interference was observed from common pharmaceutical adjuvants.
... The fluorescence quenching experiment for ZnPcs (4a and 6a) was performed in DMF according to the literature. [67] The fluorescence spectra of Zn (II) Pcs were recorded in the presence of different BQ concentrations, and the changes in the fluorescence intensity of these Pcs were determined according to the Stern-Volmer equation, as shown in equation 1. [68] ...
In this study, two novel zinc–phthalocyanine complexes (4a, 6a), containing carbazol rings, were investigated. The first phthalocyanine 4a has been synthesized from 4‐(2‐(3‐acetyl‐9H‐carbazol‐9‐yl)ethoxy at the peripheral position. Likewise, the second phthalocyanine 6a has been synthesized from 4‐(2‐(3‐cinnamoyl‐9H‐carbazol‐9‐yl)ethoxy at the same position. The new phthalocyanines and their ligands are soluble in organic solvents such as DMF, DMSO, DCM, EtOAc, MeOH/EtOH. The Zn (II)–complexes were characterized by FT–IR, NMR (except 13C‐NMR for complexes), elemental analysis, mass spectrometry, and UV–Vis spectroscopy. Also, photophysical and photochemical properties and cyclic voltagram for the N–substituted carbazole zinc–phthalocyanines have been reported. Evaluation of carbazole Zn (II)–complexes (4a and 6a) and ligand (3, 4, 5 and 6) for in–vitro α–glucosidase inhibitory activities was performed compared to standard drugs acarbose and kinetic studies were also carried out to determine their inhibition modes. The inhibitory effects of these new phthalocyanines (4a and 6a) and their ligands (3, 4, 5 and 6) on human erythrocytes carbonic anhydrase I (hCA I) and II (hCA II) isoenzymes were investigated. Moreover, in silico studies were also carried out to better investigate the interactions of N–substituted carbazole containing zinc phthalocyanines with the active sites of hCA I, II isoforms.
... The stoichiometry of the reaction between Thiamine and NBD-Cl was studied utilizing the limiting logarithmic method. [34] Plots of log RFI versus log [NBD-Cl] and log [Thiamnine] gave straight lines, with the slopes of 0.913 and 0.932 respectively. Hence it was concluded that the reaction proceeds in the molar ratio of 1:1 which is consistent to what was found in the spectrophotometric method described previously. ...
ABSTRACT
Two simple and sensitive methods for determination of Thiamine in pharmaceutical formulations have been
reported. The first method was based on the reaction of Thiamine with 1,2-Naphthoquinone-4-sulphonate sodium
salt (NQS) in basic medium (pH = 11) giving a fluorescent product which shows excitation and emission maxima
at 390 and 460 nm respectively. The second method was based on the reaction of Thiamine with 7-chloro-4-nitro2,1,3-benzoxaldizole (NBD-Cl) in buffered medium (pH = 10.5) leading to the formation of highly fluorescent
adduct which is measured at 562 nm after excitation at 472 nm. All factors that affect the reaction was studied and
optimized, and under optimum conditions linear relationship with good correlation coefficient (0.999) relating to
both reagents was obtained in the concentration ranges 0.1 – 1.0 and 0.2 – 1.0 µg/mL for NQS and NBD-Cl methods respectively. The limit of detection was found to be 0.020 µg/mL for the two methods. The Precision of the methods were satisfactory with relative standard deviation (RSD) of less than 2. The proposed methods were
successfully applied to the analysis of Thiamine in pharmaceutical formulations with good accuracy; the recovery
percentages ranged from 98.90±0.49 –101.39±1.02 %. The results were in good agreements with those of the
reported methods.
... The stoichiometric ratio between the cited drugs and MER reagent was assessed by molar ratio methods [27] and Job's method. [28] An equimolar solution of each drug and reagent was prepared at one concentration (4 Â 10 À3 M). ...
Approved, straightforward, fast and delicate spectrofluorimetric strategy has been developed for the estimation of tepotinib (TEPO), sotorasib (SOTO) and darolutamide (DARO) as a new antineoplastic drugs. Spectrofluorimetric strategy was based on quantitative fluorescence quenching of MER at 538 nm after being excited at 350 nm by the addition of cited drugs in presence of acetate buffer (pH 3.5). The degree of fluorescence quenching is directly proportional to the concentrations of the cited drugs within the concentration range of 0.5-10.0, 0.2-10 and 0.4-10.0 μg mL-1 for TEPO, SOTO and DARO, respectively. Mean ± S.D. were calculated for the studied drugs as follows; 99.9±0.87, 99.72±1.08 and 100.21±1.44, for TEPO, SOTO and DARO, respectively. LOD values were 0.16, 0.05 and 0.11 μg mL-1 while LOQ values were 0.5, 0.15 and 0.36 μg mL-1 for TEPO, SOTO and DARO, respectively. Statistical comparison of comes about with those gotten by detailed strategies given great understanding and uncovered that there were no noteworthy contrasts in exactness and exactness between strategies. The proposed strategy was connected effectively to analyze measurement shapes containing the examined drugs. Moreover, the recommended fluorimetric strategy was connected for examination of TEPO, SOTO and DARO in human plasma and urine test.
... Job's method of continuous variation and molar ratio method were applied to study the stoichiometric ratio of the complex formed [50]. 1×10 -3 M of MD and 1×10 -2 M of MBTH solutions were used. ...
A new and direct colorimetric method has been established for the determination of catecholamine (methyldopa, MD) in both pure form and in pharmaceutical formulations. The method is based on the oxidative coupling reaction of MD with 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) and potassium ferricyanide at pH 10.4 in aqueous medium to form an orange product that has a maximum absorption at 460 nm. Beer's law plot showed good correlation in the concentration range of 1.0−56.0 µg mL-1, with detection limit of 0.31 µg mL-1. Molar absorptivity for the above method was found to be 6.56×103 L mol-1 cm-1. All the measurements were carried out at 25 ± 1.0 °C, the formation constant (logKf) value of colored species is 9.48 and the standard free energy (DG‡) is − 54.09 KJ mol-1. This method was applied successfully to determination of MD in tablets and the results were compared with the USP method. Common excipients used as additives in tablets do not interfere in the proposed method. The method is accurate, precise and highly reproducible, while being simple, cheap and less time consuming and hence can be suitably applied for routine analysis of MD in bulk and dosage forms.
... The emission plots recorded after adding different concentrations of BQ to compound 3 are given in Figure 2. As the concentration of the BQ increases, the intensity of the emission peak appears to decrease. In addition, as seen in Figure 3, as a result of the diffusioncontrolled quenching mechanism, the slope is linear, and the KSV value was calculated as 47.89 M -1 (32,33). kq (bimolecular quenching constant) value of compound 3 was calculated as 3.60x10 10 s -1 . ...
A novel unsymmetrically substituted zinc phthalocyanine (ZnPc) containing six hexylthio units and a morpholinoethoxy group was synthesized and characterized. Statistical condensation reaction of two different phthalonitriles was used for the preparation of unsymmetrical ZnPc. The novel compound was purified using chromatographic methods with the help of high solubility differences of phthalonitrile derivatives. Characterization of the compound was achieved by using NMR, FT-IR, UV-Vis, and mass spectroscopic methods. The photophysical measurements were made in tetrahydrofuran (THF). Fluorescent quantum yield (ΦF) and fluorescence lifetime (τF) of unsymmetrical ZnPc were determined. Fluorescent quenching experiments were done by adding benzoquinone (BQ) in THF, and Stern-Volmer constant (Ksv) and quenching constant (kq) values were calculated.
... To establish the mole ratio between CM or MF drug and the PT reagent, mole ratio method of continuous variations of equimolar solutions was employed [27,28]. The drug and the reagent were mixed in various proportions. ...
... To study the stoichiometry of the reaction, the molar ratio between thorium and nornicotine in equimolar solutions and in the presence of an excess amount of nornicotine was determined using Job's method. 41 It was found that the ratio was 1:3, as shown in Figure 3. ...
A rapid, sensitive, and selective method was developed for the quantitative determination of
thorium concentration which is an important natural-mineral based on the complex formed
with natural phytochemical nornicotine alkaloid at pH 4 – 6, the coloured complex was extracted
in chloroform with a linear relationship in a concentration range from 6-50 µgmL-1 with molar
absorptivity 1.8 x 104 (1 mol-1
cm
-1
), Sandell’s sensitivity (µgcm
-2
) 2.3 × 10ˉ2
, correlation
coefficient 0.9998, limit of detection 0.57 µg ml-1
and limit of quantification 1.88 µg ml-1
at
430 nm. The effects of pH, nornicotine concentration, temperature and time were also studied.
The method shows high selectivity for thorium and holds its accuracy and precision well.
Therefore, the method is useful when applied to the determination of thorium in synthetic
solution and in the monazite sample.
... Stoichiometry of the Reaction To study the stoichiometry of the reaction, the molar ratio between Mo(V) and each of the investigated drug in equimolar solutions and in the presence of an excess amount of ammonium thiocyanate was determined using job's method. 41) It was found that the ratio was 1 : 1 for the three drugs when using an enalapril base as shown in the proposed Chart 1, but when enalapril used as maleate the ratio was 1 : 2 (Figs. 3, 4). ...
The official drugs, ramipril: 4-[2-(1-ethoxycarbonyl-3-phenyl-propyl)aminopropionyl]-4-aza bicyclo[3.3.0]octane-3-carboxylic acid and enalapril maleate: 1-[2-(1-ethoxycar-bonyl-3-phenyl-propyl)aminopropionyl]pyrrolidine-2-car-boxylic acid and the non official fosinopril: 4-cyclohexyl-1-[2-[(2-methyl-1-propanoyloxy-propoxy)-(4-phenylbutyl)-phosphoryl]acetyl]-pyrrolidine-2-carboxylic acid are antihy-pertensive agents which their metabolites are active in-hibitors of angiotensin-converting enzyme (ACE); inhibition of ACE results in decreased plasma angiotensin II which leads to decreased vasopressor activity. 1) Ramipril and enalapril maleate are official in B.P. 2) and enalapril maleate is official in USP 24, 3) while fosinopril is unofficial in any phar-macopoeia. Various analytical methods have been reported for the assay of the cited drugs in their pure forms as well as in pharmaceutical formulations. They include for ramipril, a kinetic spectrophotometry, 4) spectrophotometry and atomic absorption , 5) fluorimetry, 6) HPLC, 7) bioavailability assessment of nanoemulsion, 8) reversed-phase HPLC, 9) and liquid chromatography mass spectrometry. 10) For enalapril, spectropho-tometry using chelate formation with palladium(II) chloride , 11) spectrophotometry in the presence of its photo degradation products, 12) quantitative 1 H-NMR spectroscopy, 13) second derivative ultraviolet spectrophotometry, 14) HPLC in the presence of the major active metabolite enalaprilate, 15) linear regression analysis and its application to multivariate chro-matographic calibration, 16) HPTLC, 17) radio-immunoassay, 18) potentiometric titration 19) and differential pulse polarography (DPP). 20) For fosinopril with H 2-receptor antagonists by derivative spectroscopy, 21) UV and third derivative spectropho-tometry, 22) microemulsion liquid chromatography, 23) HPLC in the presence of its degradation product fosinoprilate, 24) TLC procedures 25) and reversed-phase ion-pair liquid chromatography. 26) Several colorimetric methods for determination of some drugs in pharmaceutical preparations using molybdenum (V) (Mo(V)) thiocyanate reagent forming ion-pair complex were reported such as; chloroquine and pyrimethamine, 27) ampi-cillin, dicloxacillin, flucloxacillin and amoxacillin, 28) some piperazine derivatives, 29) trazodone, amineptine and amitriptyline hydrochloride, 30) metoclopramide and oxybup-rocaine, 31) and some H 1-antihistaminics. 32) Although the chromatographic methods are sensitive enough, they are expensive and not easily manageable. On the other hand; spectrophotometry is still the technique of Three different sensitive and accurate spectroscopic procedures were developed for the determination of three angiotensin-converting enzyme inhibitors, namely, ramipril, enalapril maleate and fosinopril. The first two spectrophotometric (extractive and non-extractive) procedures were based on ternary complex formation with molybdenum(V) thiocyanate. The formed complex can be determined by extraction with chloroform measured at l l max 517 nm Beer's law was obeyed in the concentration range from (10-90 m mg ml ؊1) for ramipril and fosino-pril and (4-36 m mg ml ؊1) for enalapril maleate with molar absorptivity 1.2؋10 4 , 2؋10 4 and 3.4؋10 4 l mol ؊1 cm ؊1 , respectively, or by direct measurement after addition of benzalkonium chloride as surfactant and measuring the formed ternary complex at l l max 545 nm with a linear relationship in the concentration range from (8-72 m mg ml ؊1), (3-27 m mg ml ؊1) and (8-72 m mg ml ؊1) for ramipril, enalapril maleate and fosinopril with molar ab-sorptivity 1.5؋10 4 , 5؋10 4 and 2.1؋10 4 l mol ؊1 cm ؊1 , respectively. The third procedure is atomic absorption measurement through the quantitative determination of molybdenum content of the complex. These methods hold their accuracy and precision well when applied to the determination of ramipril, enalapril maleate and fosinopril in their dosage forms.
... The stoichiometric ratio of the complexes formed was studied by continuous variation (Job's method) and molar ratio method [36]. Where A is the maximum observed absorbance and A m is the absorbance value when all the amount of drug is associated. ...
Two simple and rapid spectrophotometric methods by the application of oxidative coupling reactions in aqueous medium for the
determination of moxifloxacin hydrochloride (MOXF) and sildenafil citrate (SC) in either pure form or in its pharmaceutical preparations
have been carried out. MOXF and SC react with 4-aminoantipyrine in the presence of KIO4 to yield red colored products exhibit
maximum absorption at 530 and 526 nm for MOXF and SC, respectively. Beer’s law plot showed linear relationship in the concentration
ranges 2.65 - 230.0 and 1.66 - 98.0 μg/mL with detection limit of 0.55 and 0.44 μg/mL for MOXF and SC, respectively. Molar absorptivity
for the above two methods were found to be 4.40×103 and 8.25×103 L/mol cm, respectively. The developed methods were
applied to estimate MOXF and SC in tablets dosage form and the results compare favorably with those of pharmacopeial methods.
Both the methods are accurate, precise and highly reproducible, cheap, rapid and suitable applied for routine analysis of MOXF and
SC in bulk and formulations.
... The molar ratio of the product formed between the studied drug and the reagent used was investigated applying the molar ratio [34] and continuous variation (Job's) methods [35] using equimolar solutions of the drug and reagent. The results indicated that the product was formed in the ratio of 1:1 (Fig. 4). ...
... The Job's method of continuous variation (Rose, 1964) was employed to determine the optimum stoichiometric ratio for charge-transfer (CT) complexation. Into seven different test tubes, containing 0, 0.25, 0.33, 0.5, 0.67, 0.75 and 1.0 mL of the drug stock solution, appropriate quantities of the CAA solution were added to make up the volume to 1 mL. ...
... Job's method of continuous variation was employed to determine the stoichiometric ratio for maximum adduct generation (Rose, 1964). Increasing volumes of the diazonium solution (0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) were transferred separately into different test tubes. ...
In Nigeria, paracetamol is readily available in several retail outlets where the conditions of storage can be poor leading to elevated levels of para-aminophenol (PAP), which is known to be nephrotoxic and hepatotoxic. However, the routine analysis of PAP is mostly by chromatographic separation which requires expensive instrumentation not often available in developing countries. The objective of this research was to develop a sensitive colorimetric method for the quantification of PAP in paracetamol.
The method was based on the diazo coupling reaction between diazotised PAP and chromotropic acid. Various reaction parameters critical for optimal detector response were optimized. The validation of the new method was done following the determination of parameters including repeatability, reproducibility and selectivity using current ICH guidelines. The new method was also applied to the assay of PAP in 14 paracetamol tablet samples.
The calibration was linear between 0.0297 and 0.2229 µg/mL at 470 nm with limits of detection and quantification of 0.0061 and 0.0185 µg/mL, respectively. The recovery was in the range of 95.96 and 102.21 while intra- and inter-day precisions at three different concentrations did not exceed 4.03%. The new method was successfully applied to quantify PAP in paracetamol with percent content varying from 0.14 to 0.21%w/w.
A simple and reliable method for the quantification of PAP has been developed and successfully employed to report, for the first time, the presence of the degradation product at levels beyond the allowable limits in paracetamol dosage forms in Nigeria.
... Florescence quenching experiments on the non-peripheral and peripheral substituted zinc(II) phthalocyanines (3 and 7) were carried out by the addition of different concentrations of BQ to a fixed concentration of the complexes, and the concentration of BQ in the resulting mixtures were 0, 0.008, 0.016, 0.024, 0.032 and 0.040 M. The fluorescence spectra of substituted zinc(II) phthalocyanines (3 and 7) at each BQ concentration were recorded, and changes in fluorescence intensity related to BQ concentration by the Stern-Volmer (S-V) equation [40] as shown in Eq. (5): ...
In this study, the novel 3-(1H-benzo[d][1,2,3]triazol-1-yl)methoxy substituted novel phthalonitrile compounds (2 and 6) were synthesized. Their non-peripheral and peripheral zinc (II) (3 and 7), manganese (III) (4 and 8) and copper (II) (5 and 9) phthalocyanine complexes were synthesized for the first time. These novel compounds were characterized by elemental analysis and different spectroscopic techniques such as FT-IR, UV–Vis, ¹ H NMR, ¹³ C NMR and MALDI-TOF mass. Also, photochemical and photophysical properties of non-peripheral and peripheral substituted zinc (II) phthalocyanines (3 and 7) were investigated for determination of photodynamic therapy applications of these phthalocyanines.
... Job's plot for composition Metronidazole-Acridone complex at 502 nm Job's plot showing a 1:1 binding stoichiometry for a MetronidazoleAcridone complex this Indicated that only one sits is responsible for the formation of the complex[14]. ...
Simple and sensitive spectrophotometric method is described to estimate Metronidazole drug in pure form. The procedure for spectrophotometric determination of Metronidazole based on the reaction of Metronidazole drug with Acridone to forms a highly stable reddish-orange colored complex. As well as their physical thermodynamic functions, chemical kinetic and binding modes were determined. The wavelength of the maximum absorption max of the complex against reagent blank was 502nm compared to 313nm for Metronidazole and 295nm for Acridone alone. The complex formed was still stable for one week. Under the optimum reaction conditions, the complex obeyed Beer ' s law in the concentration range of (1×10-3 6×10-3 M) with fair correlation. The composition of the complex was determined using the job's method of continuous variation, results showed that stoichiometric ratio of Metronidazole-Acridone was 1:1.The binding of Metronidazole to Acridone is quite strong as indicated by its equilibrium binding constant K eq and showed a reduction with increase of temperature. Thermodynamic parameter including G , H and S were determined at various temperatures (298-313), the negative values of the standard free energyG indicate that the reaction of drug with Acridone is spontaneous. The van , t Hoff equation of 1/T versus lnK eq suggests that the Metronidazole drug binds exothermically to Acridone which is characterized by high negative value of the standard enthalpy change H as well as the negative values of S indicate reduce the freedom of motion in the transition state and relatively slow reaction. A chemical kinetics result shows that the reaction was pseudo-first order reaction. Moreover atomic force microscopy to explain other properties of precipitate formed is topographical information of nanostructure between Metronidazole and phosphotungstic acid.
... They formed an ion-association complex by electrostatic and hydrophobic interaction. The composition of the ion-association complex was determined by Job's method of continuous variation [45] . The results obtained are shown in figure 8 Analytical CHEMISTRY Analytical CHEMISTRY and indicated that the composition of the associates was equimolar (1:1) for the three drugs. ...
... Fluorescence quenching experiments on the substituted metal-free and zinc(II) phthalocyanines (3a and 3b) were carried out by the addition of different concentrations of BQ to a fixed concentration of the phthalocyanines, and the concentrations of BQ in the resulting mixtures were 0, 0.008, 0.016, 0.024, 0.032 and 0.040 M. The fluorescence spectra of substituted metal-free and zinc(II) phthalocyanines (3a and 3b) at each BQ concentration were recorded, and the changes in fluorescence intensity related to BQ concentration were determined by the Stern-Volmer (SV) Equation [33] (Equation (4)): ...
The syntheses of a novel 1,4,8,11,15,18,22,25-octahexyloxy-2,3,9,10,16,17,23,24-octa-(4-trifluoromethoxyphenyl) phthalocyanine (3a) and its zinc(II) phthalocyanine derivative (3b) have been described and characterized by elemental analysis,1H NMR, 13C NMR, 19F NMR, mass, UV-Vis and FT-IR. The newly prepared metal-free phthalocyanine and its zinc(II) counterpart are soluble in most organic solvents. The photophysical and photochemical properties such as aggregation, fluorescence, singlet oxygen generation and photodegradation under light irradiation of these phthalocyanines have been investigated in DMF. The hexadeca-substituted phthalocyanines (3a and 3b) showed longer absorption and emission wavelength values when compared to that of reported phthalocyanine derivatives due to substitution of the all possible positions in the phthalocyanine framework. The zinc(II) phthalocyanine derivative does not only have a good singlet oxygen generation but also has other photophysicochemical properties that enables this phthalocyanine to be useful as a photosensitizer for cancer treatment using photodynamic therapy.
... On oxidizing the MBTH (I) with ferric chloride, an oxidizing agent, an electrophilic intermediate (II) is formed by the loss of 2 electrons and a proton (Fig. 3). The so formed (II) acts as an active coupling species 9 . 1:1 (Selexipag:MBTH) stoichiometry (obtained from limiting logarithmic method 10 ) indicates mono substitution of (II) on selexipag. ...
The present study is a first report on development of a spectrophotometric method for determination of selexipag (used to cure pulmonary arterial hypertension) in bulk and tablet formulation and its validation. The basis of the proposed method is formation of a chromophore (of λ max 600 nm) in presence of acidic ferric chloride by oxidative coupling reaction between selexipag and MBTH (3-methylbenzo-thiazolin-2-one hydrazone) solution. Regression analysis (r > 0.999) shows that the plotted calibration curve exhibits good linearity in the studied range of concentration (5 – 30 μg mL-1). As per the existing guidelines of ICH, various parameters of the method were tested for validation. Low values of R.S.D. (< 2 %) were observed indicating that the proposed method is reproducible, accurate and precise.
... The stoichiometry of the reactions was studied adopting the limiting logarithmic method [22,23]. Two straight lines were obtained with slope values of 0.63 and 0.58 (Fig. 3). ...
The synthesis of new hybrides 1,3,4-oxadiazol-2-thione with acridine 9(10H)-one is carried out. Their structure is confirmed by LC-MS, IR-,¹H and¹³C NMR-spectroscopy. The thione-thiol equilibrium was investigated in eight solvents with different relative permittivity with the help of UV-spectroscopy and quantum chemistry methods using DFT/B3LYP and HF bases. The results of the experimental calculations are in agreement with theoretical ones and have shown the prevalence of the thione. There were established centers for reactions with the mechanism SE and AE, taking into account the electronic structural formulas and the results of calculating the atom charges of compounds.
... The stoichiometry of colored oxidative coupling product was studied adopting the limiting logarithmic method [52]. The ratio of the reaction between IRB and MBTH in acidic aqueous medium was calculated by dividing the slope of MBTH curve (0.7840) over the slope of the IRB curve (0.7865), as shown in Fig. 7a and b. ...
A novel-coupling reagent is used for the simple and sensitive kinetic spectrophotometric determination of irbesartan (IRB) in pure or pharmaceutical formulations. The method utilizes an oxidative coupling reaction based on oxidation of 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) with Ce(IV) in 2% sulfuric acid medium, followed by coupling the produced electrophilic intermediate (diazonium salt of the reagent) with IRB to give greenish-blue colored product (1:1, stoichiometry) having maximum absorption at 629 nm and the colored species is stable for more than 1 h. The initial rate and fixed time (at 35 min) methods are adopted for determination of IRB concentration. The linearity is in the ranges of 5.0–40.0 μg/mL and 2.0–45.0 μg/mL and the limit of detection is 0.46 and 0.40 μg/mL for initial rate and fixed time methods, respectively. Molar absorptivity for the method was found to be 1.50 × 10⁴ L/mol cm. The validated kinetic methods can be successfully applied to the analysis of IRB in bulk and tablet dosage form and in the routine quality control analysis. The percentage recoveries were above 100% for both methods. The excipients did not interfere in the analysis.
... Stoichiometry was established by molar ratio [30] and Job's method of continuous variation [31] using equimolar solutions ( and reagent, respectively). [26] Both methods followed the procedure previously described above in spectrophotometric method (I) for ...
Validated, simple, rapid and sensitive spectrophotometric and spectrofluorimetric methods were developed for the determination of dapoxetine HCl and dosulepin HCl. The spectrophotometric method (I) was based on a binary complex formation between each drug and mercurochrome (MER) in acetate buffer (pH 3.5) with maximum absorbance at 557 nm. Calibration graphs were linear over the range 2.0–20.0 and 2.0–24.0 μg/ml, detection limits were 0.23 and 0.41 μg/ml and quantitation limits were 0.71 and 1.26 μg/ml for dapoxetine HCl and dosulepin HCl, respectively. Spectrofluorimetric method (II) was based on the measurement of the quantitative quenching effect of each drug on the native fluorescence of MER at the same pH. Fluorescence quenching of MER was measured at 538 nm after excitation at 470 nm. Calibration graphs were linear over the range 0.5–10.0 and 0.4–10.0 μg/ml, detection limits were 0.17 and 0.12 μg/ml and quantitation limits were 0.5 and 0.36 μg/ml for dapoxetine HCl and dosulepin HCl, respectively. Statistical comparison of results with those obtained by reported methods provided good agreement and revealed that there were no significant differences in accuracy and precision between methods. The proposed methods were applied successfully to analyse commercial tablets and capsules containing the studied drugs.
... The Job's method of continuous variation was employed to determine the stoichiometric ratio that was optimal for colour development 30 . Into nine test tubes containing 0, 0.2, 0.25, 0.33, 0.5, 0.67, 0.75, 0.8 and 1.0 mL of the diazonium, appropriate quantities of CTA were added to make the volume 1.0 mL. ...
The purpose was to develop a colorimetric method for determining gabapentin. The method was based on the diazo coupling reaction between diazotized gabapentin and chromotropic acid. The method was validated using ICH guidelines before its application to generic brands of gabapentin. Coupling reaction generated an orange azo adduct whose absorbance was linearly correlated with concentration in the range of 1-6 µg/mL at 470 nm. The method was accurate and precise with recovery range of 97.6-103.1%; intra-and inter-day precisions (%RSD) were less than 0.65% and showed no statistical difference when compared with reference method in the analysis of the dosage forms. The 3D optimization of the adduct revealed an E-type configuration around the azo linkage which would contribute to its stability. The new method can serve as a reliable alternative to the official method for the routine analysis of gabapentin in bulk and dosage forms.
... Job's method of continuous variation [29] was used to determine the optimal stoichiometric ratio at which the diazotized GBP will combine with DMAB. Equimolar solutions (0.02011 M) of the reagent and the drug stock solution were prepared using the procedure described above. ...
A new simple, accurate and economic spectrophotometric method based on azo dye derivatization for the determination of gabapentin (GBP) was developed. Critical factors were optimized. The method was validated and assay of dosage forms was done. Spot tests and TLC confirmed the formation of azo adduct. A 0.3 M NaNO2 solution using 2 M HCl was used for diazotization. The optimal temperature and time were 30°C and 10 min. Azo adducts were determined at 430 nm. Methanol was found to be the best solvent. Gabapentin coupled at a ratio of 1:1 with DMAB. The assays of GBP were linear over the range 1–6 µg/mL (r = 0.9973) and LOD of 0.8322 µg/mL. The methods were accurate (error < 2%) and precise (RSD < 0.5%). The methods were successfully applied to the assay of GBP in dosage forms and compared favorably with reference method (p > .05). The successful diazotization of gabapentin and the azo adduct formation with DMAB is reported for the first time.
... For instance Fig.5 presents the fluorescence decrease in intensity (quenching) for the compound 4f in presence of increasing concentrations of BQ. The changes in the fluorescence intensity related to BQ concentration are expressed by Stern-Volmer (S-V) equation (3) (Rose, 1964;Lakowicz, 2006) were: F 0 = fluorescence intensity in the absence of quencher; F = fluorescence intensity in the presence of quencher; K SV = Stern-Volmer constant; [BQ] = concentration of the quencher (1,4-benzoquinone). ...
New pyrrolo[1,2-c]pyrimidines derivates having a biphenyl moiety at position 3 have been synthesized by 1,3-dipolar cycloaddition of their corresponding N-ylides with activated alkynes. FTIR, 1 H and 13 C NMR spectroscopy and elemental analysis have been used to characterize the structures of the new nine pyrrolo[1,2-c]pyrimidine derivates. Absorption and fluorescence spectra have been recorded. The appropriate solvent for the photoluminescence properties of the studied compounds has been found to be chloroform:acetonitrile mixture (1:1). The main spectral features such as molar extinction coefficients (e), Stokes shifts, quantum yields using quinine sulphate as standard, fluorescence quenching in the presence of benzoquinone and Stern-Volmer constants have been calculated. The substituent effects on intensity of absorption, maximum absorbance wavelengths and fluorescence parameters have been discussed. The highest quantum yield value was found for ethyl 3-(4-biphenylyl)-7-(3,4-dimethoxybenzoyl)pyrrolo[1,2-c]pyrimidine-5-carboxylate (0.55). The obtained results suggest that the studied compounds are promising candidates for future study in order to evaluate their use in practical applications in fluorescent chemical sensors. Ó 2016 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
... Fluorescence quenching experiments with the substituted zinc phthalocyanines (3, 6, and 7) were performed by adding a series of concentrations of benzoquinone to a constant concentration of the complex. The Stern-Volmer constants of the studied compounds were found by Equation (3) [26]. The I 0 /I ratios were calculated and are shown as a plot against [BQ] by using Equation (3), and K SV is determined from the slope. ...
We have synthesized a new phthalonitrile with different substituents in 4- and 5-positions (1). Cyclotetramerization of 1 yielded phthalocyanines with cobalt(II) (2), zinc(II) (3), gallium(III)chloride (4), and indium(III)chloride (5) containing diethylamino-phenoxy and hexylsulfanyl substituents on each benzene unit. Elemental analyses, Fourier transform infrared spectra, ¹H-nuclear magnetic resonance spectra, mass spectra, and ultraviolet-visible spectra were used for characterization of the phthalocyanines. The aggregation behavior of the zinc phthalocyanine derivative was studied in different concentrations. Also four chloro and four diethyllaminophenoxy substituted zinc phthalocyanine (6) and octa-diethylaminophenoxy substituted zinc phthalocyanine (7) were synthesized. These phthalocyanines (3, 6, and 7) were compared for electronic absorption spectra, fluorescence quantum yields, fluorescent lifetimes, and fluorescence quenching in the presence of benzoquinone. The fluorescence quantum yield gives the efficiency of the fluorescence process. The fluorescence lifetime is an important parameter for practical applications of fluorescence such as fluorescence resonance energy transfer and fluorescence-lifetime imaging microscopy.
... The stoichiometry of the complex between cefdinir and Pd(II) chloride was studied by applying Job's method of continuous variation [15] using an equimolar ( 5 × 10 -4 M) solutions of cefdinir and Pd(II) chloride . The total volume of drug and Pd(II) chloride was kept at 2 mL then the procedure was completed as under the above mentioned procedure. ...
Five Simple, accurate and rapid spectrophotometric and conductometric methods were developed for the determination of four third generation cephalosporins, namely, cefotaxime sodium (I) , cefoperazone sodium (II), ceftazidime pentahydrate (III) and cefdinir (IV) in pure active ingredient, pharmaceutical dosage forms and human urine. Method A: is based on the reaction of the sulphide ions produced from the alkaline hydrolysis of the cited four drugs with P- aminophenol (PAP). This reaction results in a thionine dye (phenothiazine derivative) formation which exhibits maximum absorbance at 545 nm. Method B: is based on oxidation of drug (I and III) with a known excess of n-bromosuccinimide (NBS) in acidic medium followed by the determination of unreacted amount of n-bromosuccinimide with metol and sulphanilic acid. The purple-red reaction product exhibits maximum absorbance at 520 nm. Method C: is based on the formation of yellow chelate between drug (IV) and palladium (II) chloride in buffered medium (pH 3.5) with an absorption maximum at 314 nm. Method D: is based on the reaction of drug (IV) with aqueous ninhydrin to give yellow colored product in the presence of bicarbonate with an absorption maximum at 433 nm . Method E: A conductometric method is based on the reaction of the four cited drugs with phosphotungstic acid (PTA) forming an ion associate in aqueous medium. Validation of the proposed methods was carried out. All proposed methods were successfully applied for the commercial dosage forms of the cited drugs. Method C was successfully applied for the determination of cefdinir in human urine.
... The stoichiometry of the reactions in the two methods was studied adopting the limiting logarithmic method [40]. Plots of log absorbance versus log [reagent] and log [drug] gave straight lines. ...
A simple, sensitive and rapid spectrophotometric methods were developed and validated for the determination of two antihypertensive drugs namely, carvedilol and nebivolol hydrochloride in pure form and pharmaceutical formulations. Method (I) is based on the formation of a binary complex between the studied drugs and eosin Y in presence of tween 80 at (pH 3.0).The formed complex exhibited maximum absorption at 545 nm for carvedilol and 543 nm for nebivolol. The concentration plots were rectilinear over concentration range of 0.5-5 and 1-7 µg/mL with lower detection limits of 0.09 and 0.11µg/mL and lower quantitation limits of 0.28 and 0 .34 µg/mL for carvedilol and nebivolol respectively. Method (II) is based on the reaction of studied drugs through their secondary amino groups with 2, 4-dinitrofluorobenzene (DNFB) at pH 8 to form yellow colored reaction products peaking at 383 nm and 390 nm for carvedilol and nebivolol, respectively. The absorbance-concentration plots were rectilinear over the concentration ranges of 5-30 and 4-28 µg/ mLwith the lower detection limits of 0.48 and 0.51 µg/mL and the lower quantitation limits of 1.45 and 1.54 µg/mL for cavredilol and nebivolol respectively. The different experimental parameters affecting the development and stability of the formed complex and reaction products were carefully studied and optimized for both methods. Both methods were successfully applied for determination of the studied drugs in their dosage forms.
... The stoichiometry of AZT-ARS complex was determined by Job's method of continuous variation and mole-ratio method in the neutral medium. 32 The plots in Figure 5a and 5b indicate formation of 1:1 and 1:2 AZT:ARS complexes using both the methods. A similar observation was reported for the complexation of AZT with 1,2-naphthoquinone-4-sulfonate in alkaline conditions. ...
A new approach based on a selective charge transfer reaction with alizarin red S is described for the simultaneous determination of azithromycin and levofloxacin in their binary mixtures using an absorption-factor spectrophotometric method. Native absorbance was used for the determination for levofloxacin, while a charge transfer complexation of alizarin red S served as the basis for the quantitation of azithromycin. The reaction of azithromycin with alizarin red S was possible in methanol under neutral conditions within 15 min at 25 ◦C. The conditions were suitably optimized for selective complexation of azithromycin with minimal interference from levofloxacin. The calibration curve was linear over the concentration range of 4.0–20 µg mL⁻¹ for azithromycin and levofloxacin and the correlation coefficients of the regression equations were consistently greater than 0.9970 for both the drugs. The limit of detection was 1.07 µg mL⁻¹ for azithromycin and 0.84 µg mL⁻¹ for levofloxacin. The developed method was highly reproducible with precision (RSD%) values in the range of 0.54%–0.95% for both the drugs. The method was successfully applied for the simultaneous determination of these antibacterial drugs from their synthetic mixtures and pharmaceutical formulations with no interference from excipients.
PurposeThe prevalence of type 2 diabetes mellitus is one of the global concerns and almost 80% of diabetic patients are treated with oral antidiabetic drugs. GLMP as a prescribed oral antidiabetic drug for diabetic patients enhanced its necessity. Therefore, it is essential to quantify it in several drug formulations and biological samples. Hence, a simple, eco-friendly, validated kinetic spectrophotometric method was developed for quantifying GLMP in commercial dosage forms.Methods
The method was based on the oxidation of the GLMP with potassium permanganate. The reaction was followed spectrophotometrically, measuring an increase in absorbance with time at 605 nm. RSM optimized the influence of preliminary experimental variables for the proposed procedure via BBD, a frequently used DoE. Under the optimized conditions, initial rate, fixed-time (at 6.0 min), and equilibrium method (25.0 min) were adopted for constructing the calibration graphs to determine the amount of GLMP. The robustness of the proposed method was performed, and the effect of selected analytical parameters was investigated with alternative conditions employing Youden and Steiner’s test.ResultsThe outcomes of the model were significant. Hence, the performance of the analytical method was validated statistically and through recovery studies using ICH guidelines. Calibration curves were linear in the concentration ranges of 4.0–36.0 µg/ml with a detection limit of 1.60, 1.02, and 1.13 µg/ml for the initial rate, fixed-time, and equilibrium method, respectively. The proposed method’s greenness profile was assessed using the analytical Eco-Scale and found greener in terms of using harmful reagents, energy consumption, and waste production. Statistical comparison of the results is shown in good agreement with the results found by the reference method, indicating no significant difference in accuracy and precision.Conclusion
The proposed validated kinetic method is simple, accurate, low cost, safe, and eco-friendly and might be used in research laboratories, hospitals, and pharmaceutical industries for the routine quality control analysis of GLMP in commercial dosage forms.
Simple, rapid, and sensitive spectroscopic methods have been proposed to determine the antifungal drug mebendazole. These methods adapted the reduction of ferric into ferrous in a 1,10 phenanthroline–iron complex in an acidic medium giving an orange–red ferroin complex. In the first method, the spectrofluorimetric assay was based on mebendazole quenching for the fluorescence of ferric–phenanthroline complex at pH 3.7. The fluorescence difference was quantitated at 409 nm after excitation at 254 nm. The second method involved the spectrophotometric measurement of the formed complex at 510 nm. A linear correlation was found over the concentrations 3.0–17.0 and 5.0–20.0 μg/mL, respectively, for methods I and II. The correlation coefficient (r) of the two methods is 0.9998. The two methods were successfully utilized for mebendazole determination in tablets. The mechanism of the reaction pathway is represented. Statistical comparison revealed no significant differences between the findings achieved by the proposed and comparison methods.
In this study, two novel metallophthalocyanines (ZnPc and CoPc) were synthesized using the corresponding metal salts 4‐(4‐(4‐[4‐chlorophenyl]‐5‐methylisoxazol‐3‐yl)phenoxy)‐phthalonitrile (11), prepared from the reaction of 4‐nitrophthalonitrile and 4‐(4‐[4‐chlorophenyl]‐5‐methylisoxazol‐3‐yl)phenol (9). These metallophthalocyanines (MPcs) showed quite solubility in organic solvents such as dichloromethane (DCM), tetrahydrofuran (THF), dimethyl formamide (DMF), and dimethylsulfoxide (DMSO). The novel compounds 11a and 11b have been characterized using their UV–Vis, FT–IR, 1H NMR, 13C NMR, X‐Ray, and MALDI–TOF mass spectra. Supporting information cocerning with the study has been supplied. Photochemical, photophysical, and cyclic voltagram properties of these novel 4‐(4‐(4‐[4‐chlorophenyl]‐5‐methylisoxazol‐3‐yl)phenoxy substituted metallophthalocyanines (11a and 11b) were determined in DMF. DNA binding, metal chelating effect assay, and DPPH [2,2‐diphenyl‐1‐picrylhydrazyl hydrate] radical scavenging assay and electrochemical studies of MPcs were investigated. Further, the inhibitory effects of the COX‐inhibitor based novel metallophthalocyanines (11a and 11b) and their ligands (10 and 11) were examined on human erythrocyte carbonic anhydrase I (hCA‐I) and II (hCA‐II) isoenzymes, and the synthesized molecules exhibited very strong inhibitory effects on both isoforms. In addition, the hCA‐I and hCA‐II inhibition potential of Zn (II) and Co (II) Phthalocyanine complexes was supported by molecular docking studies. The binding interaction of metallophthalocyanines complexes 11a, 11b enzymes were analyzed in detail.
A modern validated kinetic spectrophotometric method with a novel coupling reagent has been described for the determination of levofloxacin (LEV) in pure and tablets. The method involves an oxidative-coupling reaction between LEV and 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH), in the presence of Ce(IV) in H2SO4 medium, to gives greenish-blue product. The reaction is followed spectrophotometrically by measuring the increase in absorbance with time at 629 nm. The initial rate, rate constant, fixed absorbance and fixed time methods have been tested for constructing the calibration graphs, and are linear. The most suitable analytical methods were the initial rate and fixed time (at 20 min) methods for determination of LEV in the concentration ranges of 2.0–35.0 μg mL-1 and 0.65–35.0 μg mL-1 with LOD is 0.422 and 0.074 μg mL-1, respectively. The activation energy (Ea), activation enthalpy (H‡), activation entropy (S‡) and Gibbs free energy (G‡) are estimated for the reaction The kinetic proposed methods were further applied to the determination of LEV in tablet formulations with no interfere from the excipients.
Three accurate methods were developed for the quantitative determination of cefprozil in pure form and in its dosage forms. The first method was based upon the interaction of the drug with 3-methyl-benzothiazolinone-2-hydrazone (MBTH) in the presence of ceric ammonium sulfate or ferric chloride as an oxidizing agent, where the formed color was measured at λ 521 nm or 624 nm, respectively. The second inethod was based on the chelate formation with palladium (II) chloride (PdCl2) in the presence of buffered medium, where the formed complex was determined at λ 345 nm. The third method was based upon the reaction of the neutral solution of the hydrolysis product of drug with each of silver nitrate & lead acetate standard solutions, forming drug-metal complex and the metal ion contents were determined directly or indirectly by atomic absorption spectroscopy (AAS). The reaction conditions of the proposed methods were studied and optimized. The precision of the proposed methods was achieved by determining different samples of bulk powder and pharmaceutical dosage forms. The validity of the methods was assessed by applying the standard addition technique and the results were compared with those obtained by the reference method showing a great agreement
Novel metallophthalocyanines substituted with four peripheral 4-[3,4-bis(benzyloxy)benzylidene]aminophenoxy groups were prepared by Schiff base condensation of 4-aminophenoxy-substituted phthalocyanines with 3,4-bis(benzyloxy)benzaldehyde. The structures were elucidated with elemental analysis, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectrometry, and matrix assisted laser desorption ionization-time of flight spectrometry along with Ultraviolet–Visible spectrophotometry. In the studied concentration range of 1–10 × 10−6 M, no appreciable aggregation of the new species was detected. In tetrahydrofuran, the fluorescent quantum yield ΦF value of the zinc phthalocyanine was lower than the unsubstituted ZnPc (ΦF = 0.25) due to the peripheral [3,4-bis(benzyloxy)benzylidene]aminophenoxy substituents which surely caused fluorescence quenching. The zinc phthalocyanine showed fluorescent quenching by the addition of 1,4-benzoquinone in tetrahydrofuran with obedience to Stern–Volmer kinetics.
Objectives: cefazolin sodium and cefalothin sodium are the broad spectrum of antibiotics, are mainly used to control gram positive and gram negative bacterial infections. Cefepime is used to treat moderate-severe nosocomical pneumonia, infections caused by multi resistant microorganisms.(eg. pseudomonos aeruginosa) and empirical treatment of febrile neutropenia. The objective of our method is to develop an effective, simple and sensitive spectrophotometric method for the assay of the above mentioned drugs in both tablet and in pharmaceutical dosage forms. Methods: The method is based on the reaction of cephalosporin's with ninhydrin reagent in the presence of sodium molybdate by maintaining the pH (5.5) using citrate buffer. The reaction is carried out at a temperature of 100 0 Results: Beer's law is obeyed in the concentration range of (1-10 µg/ml) for cefepime, (2-20 µg/ml) for cefazolin sodium and (6-40 µg/ml) for cefalothin sodium respectively. The correlation coefficient's (r C for 10 min for CEPM, 15 min for both CFZS and CFLS. The resulting Ruhemann's purple product having the absorption maximum at 570 nm is measured against the reagent blank. 2 Conclusion: Recovery studies, optical parameters and statistical comparisons justify that the present proposed method can be applied to routine drug formulation in pure and dosage forms and can be recommended for routine analysis and also for quality control of these drugs.), molar absorptivity (€), Sandell's sensitivity (s), Limit of detection (LOD) and quantification limits (LOQ) for the studied drugs were calculated. Recovery studies shows that this method is accurate and can be successfully employed for the determination of the studied cephalosporin's.
The direct determination of alogliptin benzoate (ALO) using fluorescence has not yet been accomplished because ALO cannot fluoresce naturally. Accordingly, it should be derivatized first with a fluorogenic reagent to enhance the sensitivity required for its bioanalysis. This method is the first spectrofluorimetric assay for ALO quantification exploiting the nucleophilic nature of its amino group to react with 4‐chloro‐7‐nitrobenzofurazan (NBD‐Cl) in borate buffer at pH 8.5 to produce a strong fluorescent compound that is excited at and emits at wavelengths 470 and 527 nm, respectively. Experimental variables concerning the conditions of reaction and fluorogenic intensity were carefully investigated and optimized. Linearity was from 1–250 ng ml−1 with a lower detection limit of 0.29 ng ml−1 and a lower quantification limit of 0.88 ng ml−1. Validation of the current study was accomplished with mean per cent recovery of 100.62 ± 1.59 in tablets and 99.86 ± 0.82 in human plasma. Furthermore, the current method has been utilized in the bioanalysis of ALO in real rat plasma after oral administration with a simple specimen preparation. The developed method has proven to be a promising alternative method for ALO analysis in bioequivalence studies.
Simple, accurate, and precise spectrophotometric method has been developed and validated for the estimation of amlodipine besylate (AML) in tablets. The method is based on the condensation of AML with sodium 1,2-naphthoquinone-4-sulphonate in an alkaline medium when the reaction mixture was heated at 363 K for 1 min to form an orange-colored product. The spectrophotometric method involved the measurement of the colored product at 459 nm. The reaction conditions were studied and optimized. Beer’s law was obeyed in the concentration range of 10–20 µg·ml⁻¹ with RSD of 0.825 and 0.559 % and molar absorption of 2.54·10⁴, the range of methods application is 67–133 % of the nominal content of amlodipine besylate in the dosage forms. © Sulyma M., Vasyuk S., Zhuk Yu., Kaminskyy D., Chupashko O., Ogurtsov V., 2018.
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