An isotope dilution high-resolution mass spectrometry method for quantitative measurement of isomeric benzo[a]pyrene tetrol metabolites derived from albumin-bapde adducts as indicators of human exposure to polycyclic aromatic hydrocarbons

We evaluated in a pilot study a newly developed method of gas chromatography isotope dilution high-resolution mass spectrometry selected ion monitoring (GC-ID-HRMS-SIM). This method measures benzo[a]pyrene (B[a]P) tetrol metabolites released after albumin-BaPDE adduct hydrolysis. We isolated albumin adducts from the blood of a cohort of adult male and female smokers and nonsmokers randomly selected as exposed and nonexposed groups. Isomeric B[a]P tetrols released after adduct hydrolysis and silyl derivatization were quantified by GC-ID-HRMS-SIM using ¹³C₆-isotopically labeled BaP tetrol isomer standards (+/-)-BaP-r-7,t-8,t-9,c-10-tetrol (BPTI-1), (+/-)-BaP-r-7,t-8,t-9,t-10-tetrol (BPTI-2), (+/-)-BaP-r-7,t-8,c-9,t-10-tetrol (BPTII-1) and (+/-)-BaP-r-7,t-8,c-9,c-10-tetrol (BPTII-2). In all donor samples analyzed the method was sensitive enough to detect BPTII-1 and BPTI-1 in the low fmol range. In both smokers and nonsmokers BPTI-1 levels were higher than BPTII-1 levels. The mean levels of BPTII-1 and BPTI-1 in smokers were 0.16 ± 0.04 fmol/mg albumin (ranging from 0.09 to 0.28 fmol/mg albumin) and 0.40 ± 0.06 fmol/mg albumin (ranging from 0.25 to 0.75 fmol/mg albumin), respectively. The mean levels of BPTII-1 and BPTI-1 in nonsmokers were 0.22 ± 0.07 fmol/mg albumin (ranging from 0.09 to 0.41 fmol/mg albumin) and 0.47 ± 0.06 fmol/mg albumin (ranging from 0.30 to 0.75 fmol/mg albumin), respectively. The results from this study are the first reported quantitative levels of specific benzo[a]pyrene tetrol isomers detected by isotope dilution high-resolution mass spectrometry measurements of BaPDE-albumin adducts using 13C6-isotopically labeled BaP tetrol isomer standards.