Selective gas chromatographic analysis of monohydroxysteroids as their cyanosyl derivatives

A new silylating reagent that forms cyanosyl (cyanoethyldimethylsilyl) derivatives with monohydroxysteroids is introduced and its usefulness for the gas chromatographic analysis of these compounds evaluated. The reactivity of the new reagent, N-methyl-N-cyanoethyldimethylsilyltrifluoroacetamide, has been studied using a series of monohydroxysteroids and compared to that of other reagents forming cyanosyl or alkylsilyl derivatives. The results obtained indicate that at room temperature, in polar solvents, the reagent reacts rapidly and selectively with most hydroxyl groups found in steroids. The cyanosyl derivatives formed have retention properties that are comparable to those of the corresponding alkylsilyl derivatives. However, the former offer advantageous properties for detection since they can be analyzed with a nitrogen-phosphorus detector, and they exhibit mass spectral features that are suitable for identification and quantitation at low levels using selected ion monitoring mass spectrometry. The detection limits for all the monohydroxysteroids studied in this work, as cyanosyl derivatives, are typically on the order of 30-50 pg and the relative response factors are unity within a range of 25 percent.