The real and imaginary impedance versus frequency plot of CPE probe dipped in adulterated milk with 20% tap water for frequency range 5 kHz to 20 kHz given in (a) and (b). Fig. (c) shows complex plane plot for the same. 

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... experiment is performed using sample milk and 0 adulterated milk as an electrolyte at temperature 20 C and humidity 36%. The change of impedance for the PMMA coated electrode at different ionic media may be due to the anomalous diffusion which leads to the CPE behavior. It has been observed from table 1 that in the frequency ranges 5 kHz to 20 kHz, the probe shows constant phase angle (CPA). The data entered into the LEVM software for the frequency range where the probe is showing CPA behavior. The output graphs of the software are shown in Fig. 1, Fig. 2, Fig. 3 and Fig. 4. Fig. 1(a) and 1(b) shows the real impedance and the imaginary impedance versus frequency plot for sample milk. Fig. 2(a) and 2(b), Fig. 3(a) and 3(b), Fig. 4(a) and 4(b) shows the real impedance and the imaginary impedance versus frequency plots of different percentages of milk adulterated with tap water. All real impedances versus frequency plot for input data and fitting data shows good matching. But in case of imaginary impedance versus frequency plot for input data and fitting data shows slight deviation which means matching is not as good as real impedance plot. Fig. 1(c) shows the complex plane plot for sample milk. Fig. 2(c), Fig. 3(c) and Fig. 4(c) shows complex plane plot of different percentages of milk adulterated with tap water. All the graphs show a linear behavior which means a distributed element is present which is known as Constant Phase Element (CPE). The matching of input data and fitting data of complex plane plot of sample milk and milk adulterated with 10% tap water in Fig. 1(c) and Fig. 2(c) is good. This is because the fit quality factor (FQF) is very high. But in case of 20% and 30% adulteration, the complex plane plot as shown in Fig. 3(c) and Fig. 4(c) shows slight deviation. The FQF in those two cases are less than sample milk and milk adulterated with 10% tap water. The FQF is used to judge to compare which of two fits is most appropriate. So it is seen that FQF is very good in Fig. 1(c) and Fig. 2(c), but for Fig. 3(c) and Fig. 4(c) FQF is not as good as in previous case. The equivalent circuit of the probe for the best fit model obtained with sample milk and milk adulterated with different percentages of tap water is shown in Fig. 5. The equivalent circuit identified using LEVM software is same for all the ionizing medium. The values of the equivalent circuit parameters were evaluated by the estimation using this software. Though the equivalent circuit is same for all the observations but values of the fitting parameters are varying in different ionizing medium as shown in Table 1. Here R 1, R D and C P are lumped element whereas Q and α are distributed element. Q, α and R D values are considered as the impedance of the CPE. This circuit is derived from the generalized in-built circuit of LEVM software. Choosing circuit A, B, C and D the equivalent circuit obtained is as same as Fig. 5. And choosing circuit J, different circuit is obtained but comparing the FQF it is seen that the equivalent circuit shown in Fig. 5 is better. So the equivalent circuit obtained in all cases using LEVMW software is same but the values of the parameters are different. From Table 1 it is clear that R 1, R D and Q values decreases as the adulteration increases. C P value increases as adulteration increases but in case of 30% adulteration C P value decreases. Also it is clear from Table 1 that as the adulteration increases Constant Phase Angle (CPA) increases and α value ...