Comparison of Strategies for the Determination of Sterol Sulfates via GC-MS Leading to a Novel Deconjugation-Derivatization Protocol

Abstract

Sulfoconjugates of sterols play important roles as neurosteroids, neurotransmitters, and ion channel ligands in health and disease. In most cases, sterol conjugate analysis is performed with liquid chromatography-mass spectrometry. This is a valuable tool for routine analytics with the advantage of direct sterol sulfates analysis without previous cleavage and/or derivatization. The complementary technique gas chromatography-mass spectrometry (GC-MS) is a preeminent discovery tool in the field of sterolomics, but the analysis of sterol sulfates is hampered by mandatory deconjugation and derivatization. Despite the difficulties in sample workup, GC-MS is an indispensable tool for untargeted analysis and steroid profiling. There are no general sample preparation protocols for sterol sulfate analysis using GC-MS. In this study we present a reinvestigation and evaluation of different deconjugation and derivatization procedures with a set of representative sterol sulfates. The advantages and disadvantages of trimethylsilyl (TMS), methyloxime-trimethylsilyl (MO-TMS), and trifluoroacetyl (TFA) derivatives were examined. Different published procedures of sterol sulfate deconjugation, including enzymatic and chemical cleavage, were reinvestigated and examined for diverse sterol sulfates. Finally, we present a new protocol for the chemical cleavage of sterol sulfates, allowing for simultaneous deconjugation and derivatization, simplifying GC-MS based sterol sulfate analysis.

Lipases as Effective Green Biocatalysts for Phytosterol Esters’ Production: A Review

“…In general, liquid chromatography (LC) has the advantage on sample preparation over gas chromatography (GC) [178]; in the former, sample extracts usually can be analyzed directly, in contrast to the latter that demands derivatization to block hydroxyls in free sterols and glucoside and phenolics' conjugates [179]. Most frequently, phytosterols and their derivatives are silylated, meaning that hydroxyl groups react with a silylation reagent, thus producing less polar and, consequently, more volatile and/or thermally resistant derivatives for GC analysis [180]. Although sample preparation for GC is time consuming and may be tricky, chromatographic peak resolution is generally higher than in LC.…”

Analysis of Organophosphorus-Based Nerve Agent Degradation Products by Gas Chromatography-Mass Spectrometry (GC-MS): Current Derivatization Reactions in the Analytical Chemist’s Toolbox

“…Silylation is one of the most widely employed derivatization techniques in the field of GC-MS analysis [ 55 , 56 , 57 ]. The installation of the silyl group or tag onto polar analytes convert it into derivatives that are suitable for the technique and in some cases these derivatives possess enhanced detection relative to the underivatized analyte.…”

Methyl Ether-Derivatized Sterols and Coprostanol Produced via Thermochemolysis Using Tetramethylammonium Hydroxide (TMAH)

“…Silylation is effective for various functional groups, including carboxylic acids, amides, and alcohols, and it is performed using silylation reagents, such as N , O -bis(trimethylsilyl)trifluoroacetamide (BSTFA) and N , O -bis(trimethylsilyl)acetamide (BSA). The mass spectra of sterols determined via these conventional derivatizations have been reported in earlier studies [12,13,14,15,16]; thus, the interpretation of the mass spectra of sterols has become common, which allows us to easily identify sterols. Sterol trimethylsilyl (TMS) ether spectra can be divided into two patterns: ions that are accompanied by the loss of the side chain (SC) and ions that are not accompanied by the loss of the side chain (Figure 1).…”