General reversed-phase high-performance liquid chromatography procedure for the analysis of oral contraceptive formulations

Development of a highly sensitive and specific assay for plasma ethinylestradiol using combined extraction, liquid chromatography and radioimmunoassay

A highly sensitive and specific assay for ethinylestradiol (EE2) in human plasma was developed. The assay procedure combined solid-phase extraction of plasma samples, isolation of extracted EE2 by liquid chromatography (LC), and radioimmunoassay. Samples were extracted to remove polar plasma constituents and steroid binding proteins. Chromatography was employed to separate EE2 from other steroids that were candidates for assay cross-reactivity. The radioimmunoassay was shown to be sensitive (lower limit of quantitation = 2 pg ml-1 EE2 in plasma) and accurate (mean accuracy = 102%). Recovery of EE2 through extraction and LC steps was 76.1 +/- 4.5% (mean +/- SD; n = 42). Overall assay intra- and inter-assay coefficients of variation were 3.6 and 8.9%, respectively. The analyte was stable in assay buffer and assay accuracy was influenced minimally by four sample freeze-thaw cycles. This assay protocol enables the precise monitoring of low circulating levels of EE2, a prominent and potent synthetic oestrogen.

Determination of norethindrone stability on red delicious apples

A stability-indicating assay procedure for the determination of norethindrone on the surface of Red Delicious apple slices was developed. The apple slice is homogenized in pH 10 borate buffer solution and norethindrone is then partitioned into chloroform using a diffusion chamber that has a membrane that is permeable to hydrophobic compounds separating the buffer and chloroform. An aliquot of the chloroform extract is then evaporated to dryness and reconstituted in tetrahydrofuran. The reconstituted sample is then chromatographed on a C18 reversed-phase column using a mobile phase consisting of water:tetrahydrofuran:methanol (63:26:11, v/v/v). Detection is in the UV range at 254 nm. The chromatographic system is specific for norethindrone in the presence of its autoxidation products. Stability data indicate that norethindrone is stable for up to 6 h on the surface of Red Delicious apples.

Dissolution testing of norethindrone:ethinyl estradiol, norethindrone:mestranol, and norethindrone acetate:ethinyl estradiol combination tablets

Dissolution of oral contraceptive combination products from six manufacturing firms was studied utilizing the rotating basket method at 100 rpm in 600 mL of 0.1 M HCl and 0.02% sodium lauryl sulfate (SLS). Most of the combination products of norethindrone (NE):ethinyl estradiol (EE) dissolved satisfactorily in water using the paddle method which was first proposed by U.S.P., whereas three of 18 tested products showed better dissolution in acidic aqueous medium containing SLS. Acidic medium with surfactant was also found to be suitable for combination products of norethindrone (NE):mestranol (ME) and norethindrone acetate (NEAc):ethinyl estradiol (EE). A modified U.S.P. assay procedure, a reversed-phase high-performance liquid chromatographic (HPLC) method with a mobile phase of acetonitrile and phosphate buffer, was used to analyze NE and EE concurrently. The NEAc and ME were analyzed separately in these combination products. The NEAc was found to hydrolyze to some extent (approximately 20% in 8 h) in acidic dissolution medium at room temperature, but less so at 4 degrees C. The NE was identified as the sole degradation product of NEAc hydrolysis and was also measured to account for the total amount of NEAc dissolved. A simple dissoluting testing method which utilizes a single dissolution medium was applicable for all oral contraceptive combination tablets surveyed.

Optimization of the reversed-phase high-performance liquid chromatographic separation of synthetic estrogenic and progestogenic steroids using the multi-criteria decision making method

The optimization of the reversed-phase high-performance liquid chromatographic separation of a mixture of ethynylestradiol, desogestrel and three related compounds is described. A procedure is used that allows the prediction of the capacity factors of each individual synthetic steroid, depending on the mobile phase composition. Therefore, complete chromatograms can be predicted and evaluated with the multi-criteria decision making method.