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334
ISSN 0326-2383
KEY WORDS: Ganciclovir, Inorganic oxidants, Spectrophotometry, Dosage forms.
* Author to whom correspondence should be addressed. E-mail: asamin2005@hotmail.com
Latin American Journal of Pharmacy
(formerly Acta Farmacéutica Bonaerense)
Lat. Am. J. Pharm. 30 (2): 334-41 (2011)
Original Article
Received: May 6, 2010
Revised version: June 30
Accepted: July 4, 2010
Utility of Inorganic Oxidants for the Spectrophotometric
Determination of Ganciclovir in Dosage Forms
Ayman A. GOUDA
1
, and Alaa S. AMIN
2
*
1
Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt.
2
Chemistry Department, Faculty of Science, Benha University, Benha, Egypt.
SUMMARY. Eight direct spectrophotometric methods for determination of ganciclovir has been developed
and validated. These methods were based on the oxidation of the drug by different inorganic oxidants:
ceric ammonium sulphate, potassium permanganate, ammonium molybdate, ammonium metavanadate,
chromium trioxide, potassium dichromate, potassium iodate and potassium periodate. The oxidation reac-
tion were performed in perchloric acid medium for ceric ammonium sulphate and in sulfuric acid medium
for the other reagents. Different variables affecting the reaction conditions were carefully studied and op-
timized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9987-
0.9993) were found between the reading and the corresponding concentration of the drug in the ranges of
2.0-1500 μg.mL
–1
. The limits of detection ranged from 0.26-18.25 μg mL
–1
. The precision of the methods
was satisfactory; the values of relative standard deviations did not exceed 2.0 %. The proposed methods
were successfully applied to the analysis of ganciclovir in dosage forms with good accuracy and precisions;
the label claim percentages ranged from 99.9–100.4 ± 0.62–1.05 %.
INTRODUCTION
Ganciclovir is 9-[[2-hydroxy-1-(hydroxymethyl)
ethoxy]methyl]guanine. Ganciclovir (GCV) is an
antiviral medication used to treat or prevent cy-
tomegalovirus (CMV) infections. Ganciclovir is
nucleoside analogues with antiviral activity for
prophylaxis and treatment against herpes sim-
plex virus or CMV
1
. The structure of this antivi-
ral drug is shown in Figure 1.
The quantitation of GCV in biological sam-
ples poses an important challenge because this
drug is structurally similar to endogenous sub-
stances. Hence, this complicates analysis and re-
quires using a highly selective analytical
method. Some analytical methods have been re-
ported for determination of GCV including
voltammetry
2
, chemiluminescence
3
, capillary
electrophoresis
4
, and HPLC
5-17
. Spectrophotom-
etry, being simple and available in most quality
control laboratories, is considered the most rec-
ommended technique for determination of the
drug in its bulk and dosage forms. Therefore,
our laboratory aimed to develop new simple
spectrophotometric methods for determination
of GCV in pharmaceutical dosage forms.
Oxidation-reduction reactions have been
used as the basis for the development of simple
and sensitive spectrophotometric methods for
the determination of many pharmaceutical com-
pounds
18-37
. Reactions were considered in the
present study. For these reasons, reactions were
attempted for use in the present study. In oxidi-
metric reactions, the most commonly used oxi-
dizing agents are ceric ammonium sulphate
18-21
,
potassium permanganate
22-26
, Ammonium
molybdate
27,28
, ammonium metavanadate
29-31
,
chromium trioxide, potassium dichromate
32,33
,
potassium iodate
34,35
and potassium periodate
36,37
. None of these reagents have been previ-
ously used for the spectrophotometric analysis
of GCV. For these reasons, the present study
was dedicated to investigate the application of
these reagents in the direct spectrophotometric
analysis of GCV in bulk drug and dosage forms.
Figure 1. Chemical structure of ganciclovir.
335
Latin American Journal of Pharmacy - 30 (2) - 2011
MATERIAL AND METHODS
Apparatus
All absorption spectra were obtained using
Kontron 930 (UV-Visible) spectrophotometer
(German) and Perkin Elmar Lambda 12, (New
York, USA) with a scanning speed of 200
nm/min and a band width of 2.0 nm, equipped
with 10 mm matched quartz cells. Thermostati-
cally controlled water bath (German) was used.
Materials and Reagents
All solvents, acids, and other chemicals used
throughout this study were of analytical grade.
Double distilled water was obtained and used
throughout the work. Pure grade ganciclovir
(GCV) and its pharmaceutical formulations were
obtained from Roche Pharm. Inc. (New
Zealand) and was used as working standard;
purity percentages were 99.70 ± 0.81 %. Ceric
ammonium sulphate (Sigma-Aldrich Co. Ltd.,
Gillingham-Dorst, Germany) was 0.15% (w/v) in
0.25 mol.L
–1
perchloric acid (El-Nasr Pharmaceu-
tical Chemical Co., Abo-Zaabal, Egypt). Potassi-
um permanganate (El-Nasr Pharmaceutical
Chemical Co., Abo-Zaabal, Egypt) was 0.06 %
(w/v) in bidistilled water. Ammonium meta-
vanadate (Veb Laborchemie Apolda, Germany)
and ammonium molybdate (El-Nasr Pharmaceu-
tical Chemical Co., Abo-Zaabal, Egypt) were 10
% (w/v) in 20 % (v/v) sulphuric acid (Sigma-
Aldrich Co. Ltd., Gillingham-Dorst, Germany).
Chromium trioxide (Mallinckrodt Chemical
Works Montreal, New York, USA) and potassi-
um dichromate (Cambrian Chemical Bedding
Farm Road, Croydon, England) were 5.0 %
(w/v) in bidistilled water. Potassium Iodate (Sig-
ma-Aldrich Co. Ltd., Gillingham-Dorst, Ger-
many) was 3.0 % (w/v) in 20 % (v/v) H
2
SO
4
.
Potassium periodate (Sigma-Aldrich Co. Ltd.,
Gillingham-Dorst, Germany) was 0.5 % (w/v) in
20 % (v/v) H
2
SO
4
.
Pharmaceutical Formulations
The commercial capsules used in the present
investigation was Cymevene capsules (Roche
Pharm. Inc., New Zealand), labeled to contain
250 mg GCV per capsule.
Preparation of standard solutions
An accurately weighed amount (100 mg) of
GCV was transferred into a 100-mL measuring
flask, and dissolved in about 4.0 mL of 0.05
mol.L
–1
sulphuric acid. The resulting solution
were completed to the mark with bidistilled wa-
ter to provide a stock standard solution contain-
ing 1.0 mg.mL
–1
. Different volumes of this stock
solution were then further diluted with bidis-
tilled water to obtain the working standard solu-
tions of concentrations suitable for analysis by
different oxidizing reagents.
Preparation of pharmaceutical dosage
forms
The contents of 10 capsules were weighed,
finely powdered, and weighed. An accurately
weighed quantity of the capsule contents equiv-
alent to 100 mg of the active ingredient was
transferred into a 100 mL measuring flask, and
dissolved in about 4.0 mL of 0.05 mol.L
–1
sul-
phuric acid. The contents of the flask were
swirled, sonicated for 5.0 min, and then com-
pleted to the volume with water. The mixtures
were mixed well, filtered and the first portion of
the filtrate was rejected. The prepared solution
was diluted quantitatively with bidistilled water
to obtain a suitable concentration for analysis by
each particular oxidant.
General assay procedures
Up to 1.5 mL of the standard or sample solu-
tion was transferred into 10 mL calibrated flask.
One mL of the oxidizing analytical reagent was
added. Optimum volumes of an acid were
added (Table 1). The acids were perchloric for
ceric ammonium sulphate and sulphuric acid for
the other reagents. The contents of the flasks
were mixed and the reactions were allowed to
proceed for different periods of time (Table 1)
at room temperature (25 ± 5 °C), except in us-
ing ceric ammonium sulphate solution, where
the reaction mixture was heated in water bath
adjusted to 80 °C, and then cooled to room tem-
perature. After completion of the reactions, the
solutions were completed to volume with water.
The absorbance of the resulting solutions was
measured at their corresponding λ
max
(Table 1)
against reagent blanks treated similarly. In case
of ceric ammonium sulphate and potassium per-
manganate, the positions of sample and blank
cuvettes were exchanged for direct getting the
difference in the absorbance values.
RESULTS AND DISCUSSIONS
Reactions involved and spectral
characteristics
Reactions with ceric ammonium sulphate and
potassium permanganate
Ceric ammonium sulphate is a strong oxidiz-
ing agent having a yellow color of λ
max
315 nm.
The reduction of Ce(IV) to the colorless Ce(III)
proceeds cleanly in acidic solution, and its po-
336
GOUDA A.A.& AMIN A.S.
tential is different according to the acid used.
This reaction has been used for the spectropho-
tometric determination of many compounds ei-
ther by direct measurement the decrease in its
yellow color
19,20
, or indirectly by measuring the
excess Ce(IV) with oxidizable color producing
reagents
21
.
Potassium permanganate is a strong oxidant,
as well, with an intense violet color of λ
max
525
nm. The oxidation of organic compounds with
potassium permanganate was found to be a pH
dependent. During the course of the reaction,
the balance of manganese changes and the in-
termediate ions have been suggested as partici-
pating oxidants. The species that are considered
as potential oxidants depend on the nature of
the substrate and the pH of the medium. In
strong acidic medium, potassium permanganate
(KMnO
4
) produces the Mn
2
+
for a net transfer of
five electrons
22
. In neutral or basic media man-
ganese dioxide (MnO
2
) is formed with corre-
sponding net transfer of three electrons
23
. In
strongly alkaline solution, a green manganate
ion (MnO
4
2
–
) is produced
24-26
.
Both ceric ammonium sulphate and potassi-
um permanganate were tested for their oxidiz-
ing effect on GCV, and it was found that GCV
was vulnerable by both reagents in acidic solu-
tions. This was evident from the decrease in the
yellow color of ceric ammonium sulphate at 315
nm, and the violet color of potassium perman-
ganate at 525 nm. This decrease in color was
used as a measure for the concentration of the
drug. It is worth to note that GCV have no ab-
sorption capabilities in region of measurements
of both reagents (at 315 and 525 nm for ceric
ammonium sulphate and potassium perman-
ganate solutions, respectively).
Oxidizing reagent
Concentration Acid volume Reaction λ
max
,
of reagent %, (w/v) (mL)
a
time (min)
b
(nm)
c
Ceric ammonium sulphate 0.15 3 15 315
Potassium permanganate 0.06 2 15 525
Ammonium molybdate 10 4 20 675
Ammonium metavanadate 10 4 5 780
Chromium trioxide 5 4 10 595
Potassium dichromate 5 4 10 595
Potassium iodate 3 4 5 475
Potassium periodate 0.05 2 5 475
Table 1. Experimental conditions for the spectrophotometric determination of GCV by the proposed oxidation-
based methods using different oxidants.
a
Acids were 0.25 mol.L
–1
perchloric acid, 20 % (v/v) sulphuric acid,
and concentrated sulphuric acid for ceric ammonium sulphate, potassium permanganate, and the other
reagents, respectively.
b
Reactions were carried out at 80 °C in water bath for ceric ammonium sulphate, and at
room temperature (25 ± 2 °C) for the other reagents.
c
Measurements were performed after diluting the reaction
mixtures with water.
Reactions with ammonium molybdate,
ammonium metavanadate, chromium trioxide
and potassium dichromate
The reactions of GCV with these reagents
were studied, and it was found that the reaction
proceeded by oxidation of GCV and conse-
quently the reduction of ammonium molybdate,
Mo(VI), and ammonium metavanadate, VO
3
–3
,
to the corresponding Mo(V) and VO
3
–4
, respec-
tively. These ions were blue, with λ
max
values
at 675 and 780 nm, respectively (Fig. 2). Ganci-
clovir was also found to be oxidizable by both
chromium trioxide and potassium dichromate
yielding the green Cr(III) ions of λ
max
595 nm
(Fig. 2).
Reactions with potassium iodate and potassium
periodate
Potassium iodate
33,35
and potassium perio-
date
36,37
are strong oxidizing agents that have
been used in spectrophotometric determination
of many pharmaceutical compounds. Potassium
periodate has been used as selective reagent for
cleavage of 1,2-dioles and related compounds
38
. The resulting dialdehydes of these com-
pounds were determined by proper signal-pro-
ducing chemical reactions. In the present study,
GCV was subjected to the oxidation by both
reagents, and it was found to produce a red-col-
ored chromogen with λ
max
475 nm (Fig. 2).
Optimization of reaction variables
Effect of oxidant concentration
According to the above-mentioned reactions,
ceric ammonium sulphate and potassium per-
manganate solutions should be added in excess
to react with GCV. By measuring the excess
reagent, the consumed reagent would corre-
337
Latin American Journal of Pharmacy - 30 (2) - 2011
spond to the amount of the drug. The highest
concentrations of either reagent which give the
highest absorption value within the practical
sensitivity range of absorption values (approxi-
mately 0.9) was found to be 1.0 cm
–3
of 0.15
and 0.06 % (w/v) for ceric ammonium sulphate
and potassium permanganate, respectively.
For the other oxidizing reagents, the effect of
their concentrations on the reactions was stud-
ied by carrying out the reactions using 1.0 mL of
different concentrations. It was observed that
the reactions increase by increasing the concen-
tration until maximum absorbance was ob-
tained. Further increase in the concentration of
the reagents had no effect on the reactions. The
optimum concentration selected for further ex-
periments was considered as the concentration
at which maximum absorbance was obtained
and in the plateau region of the concentration-
absorption curve. These concentrations were 10
% (w/v) for ammonium molybdate and ammo-
nium metavanadate; 5.0 % (w/v) for chromium
trioxide and potassium dichromate; 3.0 % (w/v)
for potassium iodate and 0.5% (w/v) for potassi-
um periodate.
Effect of acid type and concentration
The oxidation of GCV by different inorganic
oxidants were performed in acid medium. In or-
der to determine the most appropriate acid, dif-
Figure 2. Absorption spectra reaction mixtures of
GCV with 10 % (w/v) of ammonium molybdate (1),
10 % (w/v) of ammonium metavanidate (2), 5 %
(w/v) of chromium trioxide (2), 5% (w/v) of potassi-
um dichromate (3), 3 % (w/v) of potassium iodate (4)
and 0.06 % (w/v) potassium periodate. The concen-
trations of GCV were 40, 500, 800, 700, 300 and 400
µg.mL
–1
for reaction with ammonium molybdate, am-
monium metavanidate, chromium trioxide, potassium
dichromate, potassium iodate and potassium perio-
date, respectively.
ferent acids (sulphuric, hydrochloric, nitric, per-
chloric, phosphoric and acetic) were tested. Sul-
phuric acid gave the highest absorbance with all
oxidants, except with ceric ammonium sulphate
where perchloric acid gave the highest ab-
sorbance values. This was attributed to the fact
that the potential of Ce(IV) in perchloric acid
(E° = 1.7 V) is higher than that in sulphuric acid
(E° = 1.4 V). Therefore, sulphuric acid was se-
lected for further testing with all reagents except
ceric ammonium sulphate, where perchloric
acid was selected.
Preliminary experiments indicated that for
the oxidation of GCV with the oxidants required
high concentration of the acid. It was found that
all the reactions were dependent on the concen-
tration of the acid. In order to determine the
most appropriate concentration of the acid, the
reactions were performed using varying vol-
umes (0.5–6.0 mL) of 0.25 mol.L
–1
perchloric
acid for ceric ammonium sulphate, 20 % (v/v)
sulphuric acid for potassium permanganate, and
concentrated sulphuric acid for other reagents.
The absorption intensity increased as the con-
centration of the acid increased. After attaining
the maximum absorbance readings, different be-
haviors were attained (Fig. 3). The optimum
concentration of acid at which the maximum
absorbance readings was 3.0 mL for ceric am-
monium sulphate, 2.0 mL for potassium per-
manganate and potassium periodate and 4.0 mL
for ammonium molybdate, ammonium meta-
vanadate, chromium trioxide, potassium dichro-
mate and potassium iodate.
Effect of temperature and reaction time
The reaction of GCV with ceric ammonium
sulphate that was performed in perchloric acid,
required heating for its completion. The effect
of heating temperature on the oxidation of GCV
by ceric ammonium sulphate was studied by
carrying out the reaction in a thermostatically
controlled water bath at varying temperatures
(25-100 °C). It was found that the reaction in-
creased with increasing the temperature until
reach optimum in the range of 70-100 ºC. There-
fore, further experiments were performed at 80
°C.
The effect of time on the reaction was stud-
ied by carrying the reactions for different peri-
ods of time at 80 °C for ceric ammonium sul-
phate and at room temperature for all other
reagents. The reactions of GCV with ammonium
molybdate, ammonium metavanadate, chromi-
um trioxide, potassium dichromate, potassium
338
GOUDA A.A.& AMIN A.S.
iodate and potassium periodate were time af-
fecting. However for more precise results, the
reaction mixtures were allowed to stand for 5-50
min. For the reactions with ceric ammonium sul-
phate, the time required for completion of the
reactions was 15 min. For potassium perman-
ganate and ammonium molybdate 20 min was
sufficient to full color development, whereas for
chromium trioxide and potassium chromate 10
min was required. For ammonium metavana-
date, potassium iodate and potassium periodate
5 min only was required to full color develop-
ment. After attaining the maximum absorbance
readings, longer reaction time up to 50 min had
no effects.
Effect of time on stability of oxidation products
The effect of time on the stability of the ab-
sorbance readings after dilution was studied. It
Parameters
Range Intercept Slope Corr. ε × 103 S.S LOD LOQ
mg.mL
–1
(a) (b) Coeff. (r) L.mol
–1
.cm
–1
µg.cm
–2
µg. L
–1
µg.mL
–1
Ceric ammonium sulphate 2.0-12 - 0.025 0.0643 0.9991 15.05 0.017 0.26 0.87
Potassium permanganate 5.0-50 0.0388 0.0135 0.9992 4.08 0.063 0.84 2.80
Ammonium molybdate 5.0-50 - 0.0069 0.0123 0.9989 2.994 0.085 1.16 3.87
Ammonium metavanadate 100-600 - 0.0341 0.0011 0.9992 0.2353 0.108 12.55 41.83
Chromium trioxide 100-1500 0.0613 0.0005 0.9987 0.173 0.148 17.60 58.67
Potassium dichromate 100-1400 0.063 0.0004 0.9990 0.1563 0.163 18.25 60.83
Potassium iodate 50-450 0.0309 0.0012 0.9993 0.3695 0.069 4.85 16.17
Potassium periodate 100-600 - 0.016 0.0011 0.9991 0.2677 0.095 14.70 49.0
Table 2. Quantitative parameters and statistical data for the spectrophotometric determination of GCV with vari-
ous oxidants. S.S is the Sandell sensitivity.
Figure 3. Effect of acid concentration on the ab-
sorbance of the reaction mixture of 8.0, 40, 40, 500,
700, 300, 400 µg.mL
–1
GCV with the studied reagents.
Oxidizing reagent
was found that the reaction mixtures were sta-
ble for at least 3 h after diluting the reaction
mixtures. This gives the advantage of measuring
comfortably at any time within that period with-
out any changes in the readings values. This ad-
vantage is beneficial when processing of large
number of samples is necessary.
Validation of the proposed methods
Linearity, detection and quantitation limits
Under the optimum conditions mentioned
above (Table 1), the calibration graphs correlat-
ing the absorption intensity with the correspond-
ing concentration of GCV were constructed for
all the reagents used. The difference in the deter-
mination range is due to different oxidant used at
different conditions for each oxidant. Regression
analysis for the results were as carried out using
least-square method. In all cases, Beer’s law plots
(n = 6) were linear with very small intercepts (-
0.0341 - +0.0630) and good correlation coeffi-
cients (0.9987 - 0.9993) in the general concentra-
tion ranges of 2.0–1500 µg.mL
–1
(Table 2). The
limits of detection (LOD) and limits of quantita-
tion (LOQ) were determined
39
using the formu-
la: LOD or LOQ =
κ
SDa/b, where
κ
= 3 for LOD
and 10 for LOQ, SDa is the standard deviation of
the intercept, and b is the slope. The LOD and
LOQ values were ranged from 0.26-18.25 and
0.87-60.38 µg.mL
–1
. Results in Table 2 indicated
the reagents that have the lowest oxidation po-
tential, Eº (chromium trioxide and potassium
dichromate) gave the lowest sensitivities (lowest
ε values and highest LOD values), however
reagents that have the highest oxidation potential
(ceric ammonium sulphate and potassium per-
manganate) gave the highest sensitivities (highest
ε values and lowest LOD values). These results
indicated the correlation of the oxidation poten-
339
Latin American Journal of Pharmacy - 30 (2) - 2011
tial of the oxidants with the obtained ε values at
each particular oxidant.
Precision
The precision of the proposed methods was
determined
40
by replicate analysis of nine sepa-
rate solutions of the working standards at one
concentration level. The relative standard devia-
tions (RSD) values were less than 2.0 % with all
the tested reagents indicating the good repro-
ducibility of the proposed methods. This preci-
sion level is adequate for the precision and rou-
tine analysis of the investigated drug in quality
control laboratories (Table 3).
Interference liabilities
Before proceeding with the analysis of GCV
in its solid dosage forms, interference liabilities
were carried out to explore the effect of com-
mon excipients that might be added during for-
mulations. Samples were prepared by mixing
known amount (250 mg) with various amounts
of the common excipients: gum acacia (70 mg),
sucrose (100 mg), glucose (90 mg), lactose (80
mg), starch (10 mg), citric acid (5.0 mg), and
microcrystalline cellulose (6.0 mg), and the anal-
ysis was then performed. Good percentage re-
coveries 98.80-103.25 ± 0.36-1.30% were ob-
tained from the synthetic mixtures indicated the
absence of interference liabilities from these ex-
cipients. Although the methods are not selec-
tive, being based on oxidation reactions; how-
ever the good recoveries ensured its suitability
for the analysis of GCV without interference
from the common reducing excipients. This was
attributed to the sensitivity of the methods, and
the relatively high dosage of GCV that necessi-
tated the dilution of the sample, and conse-
quently the excipients beyond their interference
capabilities.
Absorbance of samples
Oxidizing reagent
123 456 789
Ceric ammonium sulphate (8) 0.439 0.547 0.623 0.656 0.485 0.573 0.495 0.531 0.439 0.445 1.46
Potassium permanganate (30) 0.450 0.553 0.618 0.650 0.479 0.58 0.510 0.524 0.450 0.5494 1.38
Ammonium molybdate (30) 0.449 0.542 0.605 0.664 0.473 0.576 0.493 0.527 0.449 0.6174 1.19
Ammonium metavanadate (300) 0.446 0.541 0.613 0.66 0.482 0.567 0.506 0.525 0.446 0.6576 0.81
Chromium trioxide (900) 0.438 0.55 0.629 0.659 0.476 0.584 0.508 0.53 0.438 0.4818 1.27
Potassium dichromate (900) 0.453 0.562 0.614 0.65 0.492 0.57 0.503 0.537 0.453 0.5743 1.00
Potassium iodate (400) 0.447 0.543 0.615 0.663 0.487 0.569 0.512 0.52 0.447 0.5054 1.59
Potassium periodate (400) 0.435 0.557 0.622 0.659 0.48 0.575 0.516 0.526 0.435 0.5275 0.98
Table 3. Precision of the spectrophotometric analysis of GCV by oxidation with different oxidants. Quantities in
parenthesis are the concentrations of the drug (in µg.mL
–1
) used in the study.
RSD
(%)
Mean
µg.mL
–1
Robustness and ruggedness
Robustness was examined by evaluating the
influence of small variation of method variables
including, concentration of oxidants, reaction
time, volume of acid (perchloric for ceric am-
monium sulphate and sulphuric for the other
reagents) and temperature on the performance
of the proposed methods. In these experiments,
one parameter was changed where as the others
were kept unchanged, and the recovery per-
centage was calculated each time. It was found
that none of these variables significantly affect
the method; the recovery values were 98.70-
100.30 ± 0.49-1.03% (Table 4). This provided an
actual indication for the reliability during routine
application of the proposed methods in the
analysis of GCV. The actual modifications that
demonstrated robustness in the method is the
lower values for standard deviation and relative
standard deviations obtained.
Ruggedness was tested by applying the pro-
posed methods to the assay of antiviral drug
(GCV) using the same operational conditions
but using two different instruments at two dif-
ferent laboratories and different elapsed time.
Results obtained from lab to-lab and day-to-day
variation were found to be reproducible, as RSD
did not exceed 2.0 % (Table 4).
Application of the proposed methods to
analysis of dosage forms
It is evident from the aforementioned results
that the proposed methods gave satisfactory re-
sults with the drug in bulk. Thus, the dosage
forms were subjected to the analysis for their
contents of the active drug material by the pro-
posed methods and HPLC method
6
. The label
claim, as percentages, ranged from 98.85–100.2
± 0.64-1.10 % (Table 5). These results were
compared with those obtained from the report-
340
GOUDA A.A.& AMIN A.S.
ed HPLC method
6
by statistical analysis with re-
spect to the accuracy (t-test) and precision (F-
test)
40
. No significant differences were found
between the calculated and theoretical values of
t and F-tests at 95 % confidence level proving
similar accuracy and precision in the analysis of
GCV in its dosage forms. It is evident from these
results that all the proposed methods are appli-
cable to the analysis of GCV in its bulk and
dosage forms with comparable analytical perfor-
mance. The critical recommendations of some
of these methods might be based on their rela-
tive sensitivities (that determines the amount of
specimen available for analysis) and experimen-
tal conditions (reaction time, temperature, dilut-
ing solvent, etc.). For example, the methods in-
volving ceric ammonium sulphate, and potassi-
Laboratory-to- Laboratory Day-to-Day
Oxidizing Reagent
Laboratory 1 Laboratory 2 Day 1 Day 2 Day 3
Ceric ammonium sulphate 99.70 ±0.63 100.05 ± 0.74 99.60 ± 0.77 99.45 ± 0.75 99.65 ± 1.10
Potassium permanganate 99.45 ± 0.82 99.70 ±0.68 100.10 ± 0.95 98.70 ± 0.63 99.80 ± 0.49
Ammonium molybdate 99.90 ± 0.67 99.65 ± 0.90 98.85 ± 1.10 100.10 ± 0.57 99.50 ± 0.78
Ammonium metavanadate 99.70 ± 0.55 99.35 ± 0.62 99.50 ± 0.72 98.95 ± 0.81 99.70 ± 0.82
Chromium trioxide 99.40 ± 0.65 98.90 ± 0.54 98.80 ± 0.56 99.90 ± 0.70 99.40 ± 0.74
Potassium dichromate 99.55 ± 0.71 99.60 ± 0.66 99.30 ± 0.49 99.70 ± 0.90 98.70 ± 0.54
Potassium iodate 100.25 ± 0.90 99.80 ± 0.80 99.55 ± 0.43 99.60 ± 0.76 100.15 ± 0.82
Potassium periodate 99.85 ± 0.69 99.60 ±0.50 99.25 ± 0.74 99.80 ± 0.83 99.65 ± 0.94
Table 4. Ruggedness of the proposed methods for analysis of GCV by various oxidizing reagents. Values are the
mean of three determinations ± RSD.The spectrophotometers used in laboratory 1 and laboratory 2 were UV-
Kontron 930 and Perkin-Elmer Lambda 12, respectively.
Parameter Method
6
Ceric ammonium Potassium Ammonium Ammonium
sulphate permanganate molybdate metavanadate
Mean
a
99.47 99.85 100.10 99.95 98.85
± SD 0.66 0.79 0.86 0.64 0.80
Number of experiments 6 6 6 6 6
Variance 0.44 0.62 0.74 0.41 0.64
t-test
b
0.83 1.30 1.17 1.33
F-ratio
b
1.41 1.68 1.07 1.45
Parameter Method
6
Chromium Potassium Potassium Potassium
trioxide dichromate iodate periodate
Mean
a
99.47 99.40 100.20 99.65 99.80
± SD 0.66 0.92 1.10 0.74 1.05
Number of experiments 6 6 6 6 6
Variance 0.44 0.85 1.21 0.55 1.10
t-test
b
0.14 1.27 0.40 0.59
F-ratio
b
1.93 2.75 1.25 2.51
Table 5. Determination of GCV in Cymevene
®
capsules (250 mg GCV/capsule ) by the proposed and reported
HPLC 6 methods.
a
Average values of six determinations were used for the reported and the proposed methods,
respectively.
b
Theoretical values for t and F at 95 % confidence limit are 2.57 and 5.05, respectively.
um permanganate gave more sensitive assays
than the other reagents. However, the assay in-
volving ceric solution needed an extra appara-
tus, water bath).
CONCLUSIONS
The present study described a simple and ac-
curate spectrophotometric method for the direct
analysis of GCV based on oxidation with some
inorganic oxidants. The proposed method in-
volved measurements in the visible region
which confer their selectivity and avoid the po-
tential interferences from UV-absorbing excipi-
ents that are encountered in the methods that
involve measurements in UV region. The range
of different sensitivities achieved with various
reagents give the opportunity for choosing from
341
Latin American Journal of Pharmacy - 30 (2) - 2011
these methods, based on the amount of speci-
men available for analysis. The wide linear dy-
namic range that has been achieved in the pro-
posed methods confers the ease in preparation
of the samples for analysis. From the economi-
cal point of view, all the analytical reagents are
inexpensive, have excellent shelf life, and are
available in any analytical laboratory. Therefore,
these methods can be recommended for the
routine analysis of GCV in quality control labo-
ratories.
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