Factors and Artifacts in the Formation of the Trimethylsilyl Ethers of Steroids

Abstract

Lack of reproducibility in the conversion of steroids to trimethylsilyl ethers for gas chromatography when utilizing the conditions described for other compounds prompted a systematic investigation of the steps in the formation of this derivative specifically for steroids. Water alone did not interfere with the reaction as expected; rather, heat in the presence of water was the major factor in hydrolysis of the ethers. For reproducible results the reaction at 56°C required a minimum of 3 hours rather than the 1–2 hours previously reported. At room temperature the minimum incubation time for optimal results was 15 hours. The best catalyst was trimethylchlorosilane without the use of heat. Redistillation of solvents was necessary for optimal results. Under these conditions the derivatives were found to be stable for at least two weeks. Presaturation (loading effect) of the column did not appear to be necessary for quantification of these ethers.