Simultaneous Determination of Ethinylestradiol and Gestodene in Oral Contraceptives by Derivative Spectrophotometry

Stability-indicating high-performance thin-layer chromatographic determination of levonorgestrel and ethinyloestradiol in bulk drug and in low-dosage oral contraceptives

A stability-indicating high-performance thin-layer chromatography (HPTLC) method was developed and validated for simultaneous determination of steroidal hormones levonorgestrel and ethinyloestradiol both in bulk drug and in low-dosage oral contraceptives. Optimization of conditions for the spectrodensitometric procedure was reached by eluting HPTLC silica gel plates in a 10 cm x 10 cm horizontal chamber. The solvent system consisted of hexane-chloroform-methanol (1.0:3.0:0.25, v/v/v). This system was found to give compact, dense and typical peaks for both levonorgestrel (R(f)=0.65+/-0.03) and ethinyloestradiol (R(f)=0.43+/-0.02). Densitometric analysis of the drugs was carried out in the reflectance mode at 225 nm by using a computer controlled densitometric scanner. The calibration curves of levonorgestrel and ethinyloestradiol were linear in the range of 200-800 and 40-160 ng per spot, respectively. The method was validated for precision, robustness and recovery. As the proposed method can effectively separate the drugs from their degradation products, it can be employed as a stability-indicating method.

Adsorptive cathodic stripping voltammetric assay of the estrogen drug ethinylestradiol in pharmaceutical formulation and human plasma at a mercury electrode

The electroreduction of ethinylestradiol at the hanging mercury drop electrode in the Britton-Robinson universal buffer of pH 2-11 was studied and its interfacial adsorptive character onto the mercury electrode surface was identified. A validated simple, rapid, sensitive, specific, precise and inexpensive square-wave voltammetric procedure is described for the determination of ethinylestradiol following its accumulation onto a hanging mercury drop electrode in a Britton-Robinson universal buffer of pH 7. The optimal procedural conditions were: accumulation potential E(acc)=-0.7 V versus Ag/AgCl/KCl(s), accumulation duration=60s, pulse-amplitude=70 mV, scan increment=10 mV and frequency=120 Hz. Limits of detection (LOD) and quantification (LOQ) of 5.9x10(-10)M and 1.9x10(-9)M bulk ethinylestradiol, respectively, were achieved. The proposed procedure was successfully applied to the quantification of ethinylestradiol in pharmaceutical formulation (Ethinyl-oestradiol tablets) and in human serum and plasma without the necessity for sample pretreatments and/or time-consuming extraction or evaporation steps prior to the analysis. LOD of 8.7x10(-10)M and 3x10(-9)M and LOQ of 2.9x10(-9)M and 1x10(-8)M of ethinylestradiol were achieved in human serum and plasma, respectively.

Recent Advances in the Analysis of Steroid Hormones and Related Drugs

The development during the last 15 years and the state-of-the-art in the analysis of bulk steroid hormone drugs and hormone-like structures and pharmaceutical formulations made thereof are summarized. Other steroids (sterols, bile acids, cardiac glycosides, vitamins D) as well as biological-clinical aspects and pharmacokinetic and metabolic studies are excluded from this review. The state-of-the-art is summarized based on comparisons of monographs in the latest editions of the European Pharmacopoeia, United States Pharmacopoeia and the Japanese Pharmacopoeia. This is followed by sections dealing with new developments in the methodology for the fields of spectroscopic and spectrophotometric, chromatographic, electrophoretic and hyphenated techniques as well electroanalytical methods. The review is terminated by two problem-oriented sections: examples on impurity and degradation profiling as well as enantiomeric analysis.

Two derivative spectrophotometric methods for the simultaneous determination of lovastatin combined with three antioxidants

A zero crossing and an algorithm bivariate calibration derivative method for the simultaneous determination of lovastatin combined separately with three antioxidants (ascorbic acid, quercetin and gallic acid) in synthetic mixtures are described. The aqueous or methanolic solutions obeyed Beer's law in the concentration ranges of 3.20-17.36 microg/ml for lovastatin, 1.76-8.80 microg/ml for ascorbic acid, 1.41-7.04 microg/ml for gallic acid and 1.84-9.20 microg/ml for quercetin, for both methods, respectively. In the second derivative (2D) zero crossing method measurements were carried out at 238.4 nm for lovastatin and 265.6 nm for ascorbic acid, 247.7 nm for lovastatin and 281.1 nm for quercetin, 251.8 nm for lovastatin and 267.6 nm for gallic acid. In the first derivative (1D) bivariate spectrophotometric method an optimum pair of wavelengths was chosen for the determination of different binary mixtures. The proposed procedures were successfully applied to the simultaneous determination of lovastatin and different antioxidants in mixtures with high percentage of recovery, 98.3-100.4% for lovastatin, 98.3-98.6% for ascorbic acid, 99.0-99.8% for quercetin and 100.5-101.1% for gallic acid and good precision. In addition, the results from the above procedures were verified by using partial least-squares (PLS) multivariate calibration method.