Determination of total mercury and methylmercury in human hair by graphite-furnace atomic absorption spectrophotometry using 2,3-dimercaptopropane-1-sulfonate as a complexing agent.
For the determination of total mercury in hair, an amount (25.0 mg) of hair sample was digested with conc. HNO3 (400 microl) at 90 degrees C for 10 min in a 7-ml teflon microreaction vessel. After digestion, the pH of the acidic hair mixture was adjusted to 5.0-6.0 by NaOH and was then passed through a clean-up Sep-Pak C18 cartridge. To the eluate, 2,3-dimercaptopropane-1-sulfonate (DMPS) and sodium acetate buffer (pH = 6.0) were added to form a mercury-DMPS complex. This complex was preconcentrated on two Sep-Pak C18 cartridges in series, and each cartridge was eluted with methanol and adjusted to 2.00 ml. A portion (50 microl) was introduced into a graphite cuvette and then atomized according to a temperature program. The method detection limit (MDL, 3sigma) was 0.064 (microg g(-1)); the calibration graph was linear up to 7.52 microg g(-1). Good accuracies were obtained when testing two human hair certified reference materials (GBW 09101 and BCR-397). Six real samples were analyzed, and the recoveries were 95.8 - 98.2% with a relative standard deviation (RSD, n = 3) < 2.1%. For the determination of methylmercury (CH3Hg+), 25.0 mg of hair sample was extracted with 2.0 mol dm(-3) HCl (1.0 ml) by ultrasonicating for 1 h. The supernatant solution was used for CH3Hg+ analysis and the hair residue was used for the analysis of inorganic mercury (Hg2+). The MDL of CH3Hg+ was 0.068 microg g(-1); the calibration graph was linear up to 6.00 microg g(-1). Six real samples were analyzed, and the recoveries were 96.0-99.2% with RSD (n = 3) < 2.3%. The sum of the concentrations of CH3Hg+ and Hg2+ was very close to that of the total mercury measured with a relative error within 3.6%. The proposed method can be accurately applied to the measurement of CH3Hg+, Hg2+, and total mercury in hair samples.
Chen
Wen-Yi
WY
Department of Environmental Science, Tunghai University, Taichung, Taiwan, Republic of China.
Wang
Yu-Chun
YC
Kuo
Mao-Sung
MS
D006197:Hair / Q000737:chemistry*; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry*; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis*; D015203:Reproducibility of Results; D013054:Spectrophotometry, Atomic / Q000379:methods*; D014494:Unithiol / Q000737:chemistry*
D007202:Indicators and Reagents; D008767:Methylmercury Compounds; D014494:Unithiol; D008628:Mercury