Szentesi A, Gergely A, Horváth P, Szász G
Institute of Pharmaceutical Chemistry, Semmelweis University, Budapest, Hungary.
Fresenius J Anal Chem. 2000 Oct;368(4):384-8. doi: 10.1007/s002160000456.
delta4-3-Ketosteroids exhibit an intensive negative Cotton effect on the circular dichroism (CD) spectra in the wavelength range for the n-pi* electronic transition (270-350 nm). With hydroxylamine hydrochloride, delta4-3-ketosteroid compounds can be transformed into oxime derivatives. Following oxime formation, positive ellipticity with low intensity can be registered in this wavelength range. The quantitative determination of delta4-3-ketosteroids is based on the considerable difference between the ellipticities before and after oxime formation. The difference ellipticity for the six ketosteroids examined (norethisterone, levonorgestrel, levonorgestrel acetate, methyltestosterone, testosterone phenylpropionate, nortestosterone phenylpropionate) varies linearly with the concentration in the interval 6 x 10(-6)-3 x 10(-3) mol/L. The method can be well applied to determination of delta4-3-ketosteroid contamination of norgestimate [(+)-13-ethyl-17-hydroxy-18,19-dinor-17alpha-pregn4-en-20-yn-3-one oxime acetate]; 0.02-10% impurity can be measured.
Δ4-3-酮类固醇在n-π*电子跃迁（270 - 350 nm）的波长范围内，其圆二色性（CD）光谱呈现强烈的负科顿效应。与盐酸羟胺反应时，Δ4-3-酮类固醇化合物可转化为肟衍生物。形成肟后，在此波长范围内可记录到低强度的正椭圆率。Δ4-3-酮类固醇的定量测定基于形成肟前后椭圆率的显著差异。所检测的六种酮类固醇（炔诺酮、左炔诺孕酮、醋酸左炔诺孕酮、甲基睾酮、苯丙酸睾酮、苯丙酸诺龙）的差异椭圆率在6×10⁻⁶ - 3×10⁻³ mol/L的浓度区间内与浓度呈线性变化。该方法可很好地应用于测定诺孕酯[（+）-13-乙基-17-羟基-18,19-二去甲-17α-孕甾-4-烯-20-炔-3-酮肟醋酸酯]中的Δ4-3-酮类固醇杂质；可检测出0.02 - 10%的杂质。
