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A Sensitive HPLC Method for Determination of Mandelic Acid in Urine, and Its Application to Biological Monitoring of Ethylbenzene-exposed Chinese Workers
OSAMU INOUE, PHD, KAZUNORI SEIJI, MS, SElMlTSU KUDO, MS, CHUl JIN, MD, SHI-XIONG CAI, MD, SHI-JIE LIU, MD, TAKA0 WATANABE, PHD, HARUO NAKATSUKA, PHD,, MASAYUKI IKEDA, MD
Abstract
A highly sensitive high-pressure liquid chromatography
(HPLC) method was developed for determination of mandelic
acid (MA) in urine as a marker of exposure to ethylbenzene at
low concentrations. This was achieved by the use of a mobile
phase (acetonitrile: 60% perchloric acid: water = 50 ml: 100 ~ 1 : 950 ml) that has no absorption at 200 nm, the wavelength at
which MA shows intense absorption. The detection limit was
0.07 mg/L urine, and the recovery rate was 101% (CV: 2.7%)
when MA was added at 250 mg/L to ten urine samples from
nonexposed subjects. The method was applied for MA determination, in parallel to a method previously developed, to 641 urine samples (from 360 ethylbenzene exposed workers and 281 nonexposed subjects), and the results were analyzed by regression analysis to examine the relationship between ethylbenzene exposure concentrations and urinary MA concentrations. A smaller intercept on the axis (essentially zero) and a larger correlation coefficient (about 0.7) indicate that the present method is more sensitive and selective to MA than the previous method. Further analysis showed that smoking reduces MA excretion in urine, whereas the effect of drinking was not clear.
KPY r-d~:
(HPLC) method was developed for determination of mandelic
acid (MA) in urine as a marker of exposure to ethylbenzene at
low concentrations. This was achieved by the use of a mobile
phase (acetonitrile: 60% perchloric acid: water = 50 ml: 100 ~ 1 : 950 ml) that has no absorption at 200 nm, the wavelength at
which MA shows intense absorption. The detection limit was
0.07 mg/L urine, and the recovery rate was 101% (CV: 2.7%)
when MA was added at 250 mg/L to ten urine samples from
nonexposed subjects. The method was applied for MA determination, in parallel to a method previously developed, to 641 urine samples (from 360 ethylbenzene exposed workers and 281 nonexposed subjects), and the results were analyzed by regression analysis to examine the relationship between ethylbenzene exposure concentrations and urinary MA concentrations. A smaller intercept on the axis (essentially zero) and a larger correlation coefficient (about 0.7) indicate that the present method is more sensitive and selective to MA than the previous method. Further analysis showed that smoking reduces MA excretion in urine, whereas the effect of drinking was not clear.
KPY r-d~:
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