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  • Author or Editor: W. Ali x
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A validated, sensitive, and highly selective stability-indicating high-performance thin-layer chromatographic (HPTLC) method has been adopted for the quantitative determination of pyridostigmine bromide in the presence of its alkaline-induced degradation product and in pharmaceutical formulations. 3-hydroxy-N-methyl pyridinium bromide (3-OH NMP) is the metabolite, impurity, and alkaline-induced degradation product of pyridostigmine bromide (PB). Pyridostigmine bromide and its alkaline-induced degradation product were separated on silica gel HPTLC F254 plates using methanol–ethyl acetate–triethyl amine–glacial acetic acid (9:1:0.5:0.05 by volume) as the developing system followed by scanning of the separated bands at 270 nm over a concentration range of 2–10 μg band−1 with mean percentage recoveries of 99.84% (SD 1.384). The proposed method was successfully applied to the analysis of pyridostigmine bromide both in bulk powder and in pharmaceutical formulation without interference from other dosage form additives. The results obtained by the proposed method were statistically compared with those obtained by the reported HPLC method with no significant difference regarding both accuracy and precision, indicating the ability of the proposed method to be reliable and suitable for routine analysis of a drug product.

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Summary

Three simple, sensitive, and validated methods were developed for the quantitative determination of fosinopril sodium (FOS) and hydrochlorothiazide (HCZ) in the presence of an HCZ impurity, chlorothiazide (CZ). The first method (I) was the ratio difference spectrophotometric method (RD), in which a standard spectrum of 8 µg mL−1 HCZ was used as a divisor, and the difference in amplitude values at 204.6 and 231.2 nm and 290 and 302.6 nm was used for the determination of FOS and CZ, respectively. Meanwhile, for the determination of HCZ, a standard spectrum of 6 µg mL−1 CZ was the chosen divisor, and the amplitude difference at 275 nm and 293.6 nm was selected for the calculation of its concentrations. The second method (II) was mean centering of ratio spectra spectro-photometric method (MCR), which depended on the implementation of the mean-centered ratio spectra in two successive steps and the measurement of the amplitudes of the mean-centered second ratio spectra at 243.4 nm for CZ and peak-to-peak amplitudes at 215.6 and 215.8 nm for FOS and at 223.8 and 224 nm for HCZ. On the other hand, the third method (III) was thin-layer chromatography (TLC)-densitometry at which the chromatographic separation of this ternary mixture was performed using pre-activated silica gel 60 F254 TLC plates and a developing system mixture consisting of ethyl acetate-chloroform-methanol-formic acid (60:40:5:0.5, by volume) with ultraviolet (UV) scanning at 215 nm. The developed methods were validated according to the International Conference of Harmonization (ICH) guidelines and were successfully used for the determination of FOS and HCZ in their pharmaceutical formulations. Also, a statistical comparison between the developed methods and the reported HPLC method was attained. Using Student's t-test and F-test, the results confirmed that there was not any significant difference between them regarding accuracy and precision.

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