Measurement of methyl tert-butyl ether and tert-butyl alcohol in human blood by purge-and-trap gas chromatography-mass spectrometry using an isotope-dilution method.

We developed an isotope-dilution method for measuring methyl tertbutyl ether (MTBE) and tert-butyl alcohol (TBA) in whole human blood using a purge-and-trap gas chromatographic-mass spectrometric method. The labeled analogues for MTBE and TBA were [~Ht2]methyl tert-butyl ether and [2Hg]-tert-butyl alcohol, respectively. Volatiles were removed from the blood by direct helium purging of the liquid; were trapped on a Tenax trap; and were desorbed, cryofocused, and cbromatograpbed on a DB-624 capillary column that was connected directly to the ion source of a mass spectrometer. Detection was by mass analysis using a doublefocusing magnetic-sector mass spectrometer operating in the fullscan mode at the medium mass resolution of 3000. For the isotopedilution method, the minimum detection limits in blood (5-10 mL) are 0.01 pg/L for MTBE and 0.06 pg/L for TBA. The isotope-dilution method proved to be a big improvement in recovery, reproducibility, and sensitivity over our previous analytical method, which used the labeled ketone, [4-2H3]-2-butanone, as the internal standard for both