Objective To compare the validity of HPLC and LC/MS analysis of urinary S-phenylmercapturic acid (SPMA)so as to assess the feasibility of HPLC method in measuring SPMA.
Methods The urine samples were acidified by 50% sulfuric acid and pretreated by liquid-liquid extraction using chloroform : isopropyl alcohol(5 : 1, v/v). The residue dissolved with methanol was injected in ODS-3 column for SPMA separation, followed by ultraviolet detector and LC/ESI-NI/ MS analysis, respectively. Paired measurements were applied to the analysis of 86 urine samples from workers occupationally exposed to benzene. HPLC results were evaluated by comparison with the LC/MS analysis.
Results The limits of detection of HPLC and LC/MS were 40 μg/L and 5 μg/L, respectively. Retention time of SPMA peak appear at about 31 min and 7.8 min, respectively. 13 of 86 samples in HPLC analysis were assigned as false-positives. HPLC results compared with LC/MS data showed to overestimate SPMA concentrations of about 8%-21% and a correlation coefficient of 0.915 was calculated between the two methods.
Conclusion HPLC analytical method is suitable for preliminary screening of urinary SPMA in routine biomonitoring for benzene-exposed workers, while LC/MS could be an more accurate quantitative determination method for measuring urinary SPMA concentration.
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