Preconcentration and speciation of mercury by solid phase extraction method and determination by cold vapor atomic absorption spectrometric method

In this study, Hg(II) and MeHg ions were preconcentrated by column solid phase extraction method using Amberlyst-36 as an adsorbent. Mercury species were determined by cold vapor atomic absorption spectrometry method mounted with MHS 15 cold vapor system. Optimum retention and elution parameters were determined for both mercury species separately. For this purpose, the effect of pH, flow rate and volume of sample solution, type and concentration of eluent on the recovery of mercury species were investigated. Effect of foreign ions was also studied. Optimum values of pH, flow rate and volume of sample solution were found as 4.0, 3 mL/min and 50 mL, respectively for both Hg(II) and MeHg ions. Although the both species were retained at pH 4, the elution of them could be performed only with different eluents. The speciation was achieved by using this behavior. While MeHg ions were eluted with 10 mL of 0.1 mol/L HCl solution, Hg(II) ions were eluted with 10 mL of 0.2 mol/L thiourea solution in 3 mol/L HCl. Under the optimum experimental conditions determined, limit of detections for Hg(II) and for MeHg were found as 0.44 µg/L and 0.56 µg/L, respectively. Because of the eluent volume is 10 mL and the sample volume is 50 mL, only 5 were obtained as preconcentration factor. To check the accuracy of the proposed speciation and preconcentration method certified reference material (ERM-CE464 Tuna Fish) was analyzed and MeHg could be determined with a relative error of 7.8%. Because Hg(II) concentration in certified reference material is lower than the detection limit of the method, it could not be determined. However, the accuracy was also checked by analyzing spiked water and fish samples for both species and total mercury. Relative error for spiked samples was also found below 10%. Relative standard deviation of recovery for both species was found below 3% for five replicates.Key Words : Preconcentration, speciation, mercury, adsorption, solid-phase extraction, atomic absorption spectrometry