Electron-capturing Derivatization of Neutral Steroids for Increasing Sensitivity in Liquid Chromatography/Negative Atmospheric Pressure Chemical Ionization-Mass Spectrometry

Abstract

Derivatization of neutral steroids for increasing sensitivity in liquid chromatography/negative atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) has been examined. Under APCI conditions, gas-phase electrons are provided by the corona discharge and captured by electron-affinitive compounds. In negative APCI-MS, therefore, ultrahigh sensitivity can be obtained by tagging neutral steroids, whose ionization efficiencies are low in the conventional APCI-MS, with electron-capturing moieties, such as a nitro group. We synthesized various boronic acid and hydrazine derivatives having electron-capturing moieties as derivatization reagents for 1,2-diol compounds and oxosteroids, respectively. Among reagents examined, those having the 2-nitro-4-trifluoromethylphenyl moiety were most effective in increasing sensitivity. That is, the detection responses of the derivatives with these reagents were increased by several to more than 200-fold over intact steroids, where limits of detection were some picograms. The developed derivatization procedures were applied to analyses of small amounts of steroids in human plasma and gave satisfactory results.

Detection of 6-(Methylsulfinyl)hexyl Isothiocyanate (6-MITC) and Its Conjugate with N-Acetyl-L-cysteine (NAC) by High Performance Liquid Chromatograpy-Atmospheric Pressure Chemical Ionization Mass Spectrometry (HPLC-MS/APCI)

“…In positive MS/APCI, the introduction of proton-affinitive atoms, such as oxygen and nitrogen, to the analyte is very effective in increasing the sensitivity of the resulting derivative. 22) In the present study, 6-MITC and NAC were analyzed by directflow injection to optimize the MS conditions, and thereafter, they were analyzed by HPLC-MS. First, HPLC-MS/ESI was conducted but the results were not preferable. Therefore, HPLC-MS/APCI was conducted as an alternative method.…”

Quantitation of lanosterol and its major metabolite FF-MAS in an inhibition assay of CYP51 by azoles with atmospheric pressure photoionization based LC-MS/MS

“…To improve ion formation in the ESI mode analytes have to be derivatized i.e., with electrophoric labels like pentafluorobenzyl chloride which generally requires sample work up comparable to the GC-MS procedure. Another possibility is the use of sources which allow the ionization of more lipophilic compounds like the atmospheric pressure chemical ionization (APCI) source [17,18].…”

Enhanced Detection and Structural Characterization of Flavonoids by Complexation with N,O-Bis(trimethysilyl)trifluoroacetamide Using Electrospray Ionization Mass Spectrometry

“…Many derivatization reagents, such as N,N-dimethylaminonaphtalenesulfonyl (Dansyl) chloride, 25,26 p-nitrobenzoyl chloride, 27,28 pentafluorobenzyl bromide, 29,30 and 2-fluoro-Nmethylpyridinium-p-toluenesulfonate 31,32 for hydroxyl groups of steroid and lipid, and Girard-P, 33,34 O-ethylhydroxylamine hydrochloride, 35 2-hydrizino-N-methylpyridine, 36,37 and 2-nitro-4-trifluoromethylhydrazine 38,39 for steroidal carbonyl groups are reported. Ding et al, 40 Ali et al, 41 and Elba et al 42 recently reported that derivatization with silylating agents, such as BSTFA with 1% trimethylchlorosilane (TMCS), significantly increased sensitivity and selectivity by GC-MS detection of phenolic compounds, including estrogenic chemicals.…”