The quantification of synthetic corticosteroids using isotope dilution gas chromatography negative chemical ionization mass spectrometry

Abstract

Prednisolone, dexamethasone and betamethasone were labelled with deuterium via a simple synthetic procedure and used as internal standards in the gas chromatographic/mass spectrometric analysis of the corresponding undeuterated compounds. The mass spectrometer was used in the negative chemical ionization mode, which gave fragmentation of the methoxime trimethylsilyl ether derivatives favourable for their quantification. The method was applicable to the quantification of synthetic corticosteroids contained in human aqueous humour in the 0.1-10-ng range.

Determination of endogenous and synthetic glucocorticoids in human urine by gas chromatography–mass spectrometry following microwave-assisted derivatization

“…The reaction is carried out at 60 • C for 15 min; the methoxime derivative on the -OH groups can then be converted to the corresponding TMS derivative by incubation with TMSim at T = 100 • C for 2 h [4,21]. In general, the rate determining step is always the silylation of the -OH group on C17: 3-13 h are usually necessary to obtain MO-TMS derivatives of synthetic glucocorticoids with substituents on C16 [22]. Also in this case the reaction does not occur on particularly hindered residues (e.g.…”

Simultaneous identification of prednisolone and its ten metabolites in human urine by high performance liquid chromatography‐tandem mass spectrometry

“…The gas chromatography‐mass spectrometry (GC‐MS) methods for the analysis of corticosteroids are not successful due to low volatility of these compounds as MO‐TMS or TMS derivatives, thermal instability, long analysis time, and time‐consuming derivatization . High performance liquid chromatography coupled with mass spectrometry (LC‐MS) presents the condition well suited for the separation of these compounds with good specificity and sensitivity …”

Stable Isotope Dilution Mass Spectrometry Analysis of Endogenous and Synthetic Corticosteroids for the Pharmacokinetic and in vivo Metabolic Investigations in Humans

“…However, considerable losses of label have been observed for prednisolone, dexamethasone, and betamethasone labeled with deuterium during methoxime-trimethylsilyl (MO-TMS) derivatization towards the GC-MS assays [41]. The difficulties encountered in the accurate and precise analysis of these compounds were apparently due to the fact that deuterium atoms had been originally incorporated into the labile positions at C-2, C-4, and C-6 in the steroidal skeleton by a simple hydrogen-deuterium exchange reaction.…”