A poIarographic method has been developed for the assay of four progestogens as the pure drugs and their pharmaceutical dosage forms. The results obtained agreed reasonably well with the analytical data supplied by the manufacturers. The differential pulse mode was employed because it offers increased sensitivity and ease of measurement over conventional d.c. polarography.The reduction a t the dropping-mercury electrode for the four steroids was investigated and was confirmed to be a one electron per mole process for each substance. The peak potential was determined graphically and the diffusion coefficient calculated for each substance. Keywords ; Progestogen determination ; oral contraceptives ; diflerential pulse polarographyOral contraceptive preparations are now widely prescribed and as a result there has been considerable interest in their analyses. Over the years, a large number of papers have been published on the determination of these important substances. A recent report by Chatten et al.1 includes a survey of the various methods that have been proposed for the assay of one or both of the ingredients of these preparations. Studies in this laboratory involving infrared spectroscopy1 for the assay of the progestogens revealed that some excipients interfered in the analysis by causing a shift in the base-line. Consequently, for all of the progestogens, it was necessary to establish a correction for this anomaly. It was impossible to perform an analysis on some commercial products by infrared spectroscopy because certain unknown excipients interfered.In view of these problems, it was of interest to investigate other methods of analysis for these substances. The applicability of polarographic techniques to the analysis of pharmaceutical dosage forms is well recognised.2-6 In addition, the polarographic behaviour of the A4-3ketosteroids has been well documented.s-12 Accordingly, the purpose of this investigation was to examine the electroreduction of four progestogens, namely norethisterone (norethindrone), norethisterone acetate, dimethisterone and norgestrel, and t o determine the suitability of differential pulse polarography for their determination in pharmaceutical dosage forms. Experimental Apparatus and Conditions for Polarographlc AnalysisA PAR, Model 174, polarograph equipped with a drop timer was used in conjunction with a three-electrode polarographic cell consisting of a dropping-mercury electrode (D.M.E.), a saturated calomel electrode (S.C.E.) and a platinum wire as the auxiliary electrode. The entire cell was surrounded by a constant-temperature bath maintained at 25 & 1 "C. The drop time was 2 s and the flow-rate was 1.34 mg s-l. The scan rate was 2 mV s-1, the applied potential range was -1 .O to -1.95 V and the modulation amplitude was set at 50 mV. The cell was the conventional H-type with a saltagar bridge and an internal diameter of 2.3 cm. All of the polarograms were recorded on a Houston Omnigraphic, Model 2000, X -Y recorder. A Fisher, Model 320, pH meter fitted with a glasscalomel el...