| Mercury was one of the most toxic elements that were present naturally in the environment. It was widely used in our daily life. Mercury was easy to volatilize and it was harmful to human body. It was well known that the toxicity, biogeochemical behavior and transportation of mercury in the environment were heavily dependent on its chemical form. Total mercury did not convey well the real long-term pollution. so, it was essential to analyze mercury speciations qualitily and quantitatively. In this paper, we established a determination method of ultra-trace amount Hg(Ⅱ), MeHg and EtHg in products by HPLC-VG-AFS for the first time. The main results showed as follows.1 Compared with cloud-point extraction, whirlpool-mix extraction had the advantage of simple operation and higher extraction rate, was regard as the better pretreatment method.2 Optimize the equipment conditions, this part include there aspects:(1) Optimization of the separation condition.5% Acetonitrile (HPLC grade, v/v)-0.462% ammonium acetate (m/v)-0.12% L-Cys (m/v) was chose as mobile phase, flow rate 1.0 mL/min. The mercury compounds were separated on a C18 reverse phase column (Venusil MP C18,4.6mm×150mm,5μm). The there mercury species were baseline separated, and their peaks were all symmetrica.(2) Optimization of VG.1.0% K2S2O8 (m/v)+0.5% KOH (m/v) had been employed for oxidation, reducing agent was 1.5% KBH4 (m/v)+0.5% KOH (m/v), carrier solution was 7% HCl(v/v)and coupled with on-line UV, under these condition conveyed best S/N.(3) Optimization of detection system. The best conditions included that:the negative high voltage of photomultiplier tube was 310 V, lamp current was 30 mA, atomization's temperature was 200℃, atomization's hight was 10mm, carrier gas's flow rate was 400 mL/min, make up gas's flow rate was 600 mL/min.3 Method evaluation.Under the optimized conditions, the determination limits (D.L.) of Hg(Ⅱ), MeHg and EtHg were found as 0.14,0.05 and 0.12μg/L(as Hg), respectively. The relative standard deviations(R.S.D, 10μg/L, n=7) of Hg(Ⅱ), MeHg and EtHg were 3.43%/ 2.75%,2.24%/4.07% and 1.38%/3.28%(retention time/peak aera), respectively. The Seven relative standard deviations(R.S.D, n=7) of Hg(Ⅱ), MeHg and EtHg was 2.26%,2.23% and 3.06%, respectively. The spike-recovery is between 75%-110%,and a linear dynamic range between 0～10μg/L injected. 4 Method application.(1) Application in vegetable determination. The optimized method had been applied to the quantitative determination of mercury species in terrestrial vegetables and aquatic vegetables. It was showed that:among all the terrestrial vegetables we detected, only foliaceous vegetables contained with Hg(Ⅱ), then MeHg, EtHg was not detected. Mercury concentration was higher in aquatic vegetables, which only contained with Hg(Ⅱ).(2) Application in rice, Chinese herbal medicine and aquatic product determination. Change the concentration of HCl as 10% in extraction solution, other conditions was fixed. It was showed that, MeHg was the main speciation in rice, then Hg(Ⅱ), no EtHg was detected. There was no detectable mercury in Chinese medicinal materials. Mercury speciation in aquatic product was MeHg. |
