Derivatization method for sensitive determination of 3-hydroxybenzo[a]pyrene in human urine by liquid chromatography–electrospray tandem mass spectrometry

• Urinary 3-hydroxybenzo[a]pyrene (3-OHBaP) can indicate the internal exposure of carcinogenic BaP in human.
• A very sensitive method for analyzing 3-OHBaP in human urine by derivatization LC–MS/MS was developed.
• C18 enrichment, liquid–liquid extraction and silica cartridge cleanup were used for sample preparation.

While urinary 3-hydroxybenzo[a]pyrene (3-OHBaP) can indicate exposure to carcinogenic benzo[a]pyrene (BaP) in humans, most previous analytical methods could not detect it in the general population due to a lack of sufficient sensitivity. In this study, a new liquid chromatography–electrospray mass–mass spectrometry (LC–ESI-MS/MS) method was developed to analyze 3-OHBaP by employing an optimized derivatization reaction with dansyl chloride (DNS) in the aqueous phase. The instrument detection limit (IDL) of the newly developed method was 10 ng/L, which is 60-fold lower than without derivatization. The method was successfully applied to analyze 3-OHBaP and 1-hydroxypyrene (1-OHPy) in human urine combined with enzymatic hydrolysis, C18 enrichment, liquid–liquid extraction and silica cartridge cleanup. The overall method recoveries were 68.7 ± 5.47% for 3-OHBaP and 72.3 ± 4.96% for 1-OHPy, with matrix effects of <10%. The limits of quantification (LOQs) in urine were 0.3 ± 0.02 ng/L and 0.5 ± 0.02 ng/L (n = 3), respectively. The method was applied to analyze seven urine samples of volunteers, and 3-OHBaP was detected in five samples. The concentration of urinary 3-OHBaP ranged from