STUDIES ON LINEARTY AND ASSAY USING RP-HPLC AND UV-VISIBLE SPECTROSCOPY FOR THE DRUGS OXCARBAZEPINE AND PIOGLITAZONE BEFORE AND AFTER EXPIRY PERIOD

The standard for stability and quality of drugs for approval of marketing, are assured by testing and systematic evaluation using different analytical techniques. The drugs are tested in pharma analytical lab involving analysts associated spectra, chromatogram etc , and the results are analyzed leading to fixation of expiry dates. Once the drug crosses its expiry period, its potency is lost and it deteriorates, not only decreasing in therapeutic activity but also turning to be toxic.  In the present investigation RP-HPLC and UV-Visible spectroscopic methods are employed for estimation of drugs oxcarbazepine and pioglitazone in tablet dosage form before expiry period and 10-12 months after its expiry. Chromatography was carried out on a C-18 column using a mobile phase of 0.05M KH₂PO₄ and 0.5 ml Triethylamine buffer solution: methanol: acetonitrile (60:20:20 v/v) for oxcarbazepine. The flow rate was 1ml/min with detection at 254nm. For pioglitazone a mobile phase of 0.02 M  KH₂PO₄ buffer: acetonitrile (50:50v/v) was used. The flow rate was 2ml/min with detection at 270nm.The calibration curves obtained using HPLC method was linear in the range 160 – 240μgml^-1 for oxcarbazepine and 170-280 μgml^-1 for pioglitazone. The calibration curves obtained using UV-Visible spectroscopy was linear in the range 10-30 μgml^-1 for oxcarbazepine and 10-34 μgml^-1 for pioglitazone.  Assays of oxcarbazepine found using HPLC technique before expiry was 152.05mg/tablet and after expiry were 138.50mg/tablet. For pioglitazone, before expiry it was 30.85mg/tablet and after expiry 27.60mg/tablet. This was substantiated using UV-Visible spectroscopy.