Our previous research showed that humic substances may affect spectrophotometric analysis of environmental samples of Hg(II) using dithizone, which has thio-groups of high affinity for Hg(II). We did a follow-up study to quantify this effect using Acros humic acid (ACHA) and Aldrich humic acid (ADHA) and model organic acids (oxalate and cysteine). Our study shows that both ACHA and ADHA can decrease the sensitivity of the Hg(II) analysis (Hg(II) calibration curve slopes) linearly within 20-80 ppm of the HAs, but at 100 ppm, ADHA causes more decrease than ACHA. Oxalate shows a very mild effect over 20-100 ppm. Cysteine shows no effect below 1 ppm, but significantly decreases the Hg(II) calibration curve slopes linearly at 1-3 ppm and completely inhibits binding of dithizone to Hg(II) above 3 ppm. These results further indicate that the thio-groups in the HAs are responsible for the effect of the HAs on the Hg(II) analysis.

Quantitative study of the effect of humic acids on spectrophotometric analysis of Hg(II) using dithizone

245th National Meeting (2013)

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