Different reactivities of amphetamines with N-methyl-bis(trifluoroacetamide) in heated gas chromatographic injectors.
A fast gas chromatographic mass spectrometric method has been developed earlier for the determination of amphetamine derivatives in human serum and urine. For derivatization, N-methyl-bis(trifluoroacetamide) (MBTFA) was used. Derivatization was performed using an on-line mode, since 1 microl of MBTFA and 1 microl sample extract, dissolved in toluene were injected simultaneously. In this study, the reactivity of the several amphetamine type analytes with MBTFA was investigated. MBTFA used for flash derivatization was applied undiluted on the one hand and diluted 4--4096-fold with acetonitrile on the other hand. Studying several amphetamines in the test sample spiked at the same concentrations we found that they could be divided into 3 groups based on relative target ion peak areas as a function of MBTFA dilution. Group 1, containing only primary amines showed an early increase of the relative peak areas if we increased MBTFA concentration, where group 2 (mainly N-methyl secondary amines) showed that relative peak areas started to increase intensively at higher MBTFA concentrations. Finally, MDEA as an N-ethyl secondary amine, representing group 3, showed significant increase if only slightly diluted MBTFA was used as a flash reagent. This phenomenon can be explained mainly with the less and less reactivity of amine groups in the case of groups 2 and 3, compared to group 1. These findings could help to optimise analytical methods involving flash derivatization processes.
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National Institute of Forensic Toxicology, Budapest, Hungary. hidvegi.elod@toxikologia.hu
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D000081:Acetamides; D000107:Acetylation; D000662:Amphetamines / Q000737:chemistry*; D005463:Fluoroacetates; D008401:Gas Chromatography-Mass Spectrometry; D007202:Indicators and Reagents; D014269:Trifluoroacetic Acid / Q000737:chemistry
D000081:Acetamides; D000662:Amphetamines; D005463:Fluoroacetates; D007202:Indicators and Reagents; C014666:N-methyl-bis(trifluoroacetamide); D014269:Trifluoroacetic Acid