BY-PRODUCTS OF STEROID-SYNTHESIS - A CAUSE OF INTERFERENCES IN THIN-LAYER CHROMATOGRAPHY RESIDUE ANALYSIS

Since the late 1980s all of the laboratories involved in high-performa nce thin-layer chromatography (HPTLC) control of hormonal residues in kidney fat, have occasionally detected a green fluorescent spot with s imilar R(F) values and colour to those observed for methyltestosterone (MT). This spot (product) could lead to false positive results for MT and was thus named 'le faux methyl' (the false methyl) by a French-sp eaking colleague. All of the samples with a false methyl spot also con tained a relatively high concentration of progesterone. Differentiatio n of this product from methyltestosterone can be performed in three wa ys: firstly, extra HPTLC on reversed-phase plates, secondly, extra pur ification of the extract with HPLC prior to HPTLC and thirdly, gas chr omatography-mass spectrometry. This interference was identified as 20 beta-hydroxyprogesterone, a by-product of progesterone. The problem of the false methyl was not only linked with the TLC characteristics of MT but also to the progesterone used as standard. Some laboratories us ed an analytical-reagent grade standard and others used commercial pro gesterone powders as standards (e.g., obtained in crude form from phar maceutical companies), The commercial-grade progesterones showed two s pots in comparison with the analytical standard that showed just one s pot. As the false methyl was observed not only in kidney fat and meat samples, but also in illegal hormone cocktails, it was concluded that we had detected a by-product of an illegally used 'natural progesteron e'.