Method for analysis of methyltetrahydrophthalic acid in urine using gas chromatography and selected ion monitoring.
A method for the determination of methyltetrahydrophthalic acid (MTHP acid), a metabolite of methyltetrahydrophthalic anhydride (MTHPA) in human urine, was developed. The investigated MTHP acid was obtained by hydrolysis of a commercial MTHPA mixture, composed of three major isomers. These were synthesized and identified as 3-methyl-delta 4-tetrahydrophthalic anhydride, 4-methyl-delta 4-tetrahydrophthalic anhydride and 4-methyl-delta 3-tetrahydrophthalic anhydride. The urine was worked up by a liquid-solid extraction technique using C18 sorbent columns. Esterification was performed with methanol and boron trifluoride. The derivative in toluene was analyzed with capillary gas chromatography and selected ion monitoring. Deuterium-labeled MTHP acid was used as internal standard. The intra-assay precision for the overall method was between 4 and 8% in the range 3-110 ng/ml and the inter-assay precision was between 4 and 7% in the range 30-110 ng/ml. The total recoveries of the MTHP acid at 19 and 190 ng/ml were 94 and 97%, respectively. The total detection limit for the three isomers was < 6 ng/ml. Analysis of urine from a worker exposed to MTHPA makes it reasonable to assume that the method may be used for biological monitoring of MTHPA exposure.
Department of Occupational and Environmental Medicine, University Hospital, Lund, Sweden.
C H
CH
Lindh
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BA
Jönsson
D002617:Chemical Industry; D004784:Environmental Monitoring; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007536:Isomerism; D016273:Occupational Exposure; D010795:Phthalic Acids / Q000652:urine*; D010796:Phthalic Anhydrides / Q000652:urine*
D010795:Phthalic Acids; D010796:Phthalic Anhydrides; C088343:methyltetrahydrophthalic anhydride; C092122:methyltetrahydrophthalic acid