Determination of mercury at a dithizone-modified glassy carbon electrode by anodic stripping voltammetry.

Abstract

Mercury is one of the most abundant heavy metals in the environment, and its toxic effects have been recognized for a long time. Due to its dangerous and harmful properties for the health of human being, the determination of mercury is very important for environmental protection. The typical methods for determining mercury are atomic absorption spectrophotometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and mass spectrophotometry (MS). Although these methods have good sensitivity, they require expensive instruments, well-controlled experimental conditions, and profound sample-making. Because of its advantages of easy fabrication, excellent sensitivity, fast response, good selectivity and low cost, chemically modified electrodes (CMEs) have drawn much attention in every field of analytical chemistry. CMEs have been widely used in analytical chemistry, especially in electroanalytical chemistry, and have been successfully used to determine trace levels of heavy metal. 1-5 Until now, various CMEs for determining mercury have been reported. Gao and his coworkers 6 determined mercury using a ferrocenylpolythia crown ether-Nafion modifeid GCE. Navratilova et al. 7 reported a humic acid-modified carbon paste electrode (CPE) for the determination of mercury. Cai et al. 8,9 have determined mercury using a liquid anion exchanger (Amberlite LA2) modified CPE and 2-mercapto-4(3H)-quinazolinone modified CPE, respectively. To our knowledge, the determination of mercury using a dithizone-modified glassy carbon electrode has not been reported. Dithizone contains azo and hydrosulfide groups, which are good electron donors. Dithizone is widely used in extraction spectrophotometry because it can form stable complexes with many metal ions under proper conditions. From this perspective, we fabricate a dithizone-modified glassy carbon electrode to improve the sensitivity of determining mercury. As expected, 1 x 10 -7 mol/L Hg 2+ had no voltammetric response at a bare glassy carbon electrdoe (GCE) after being accumulated at -0.80 V for 5 min. However, the peak current of 1 x 10 -7 mol/L Hg 2+ at a dithizone-modified GCE was greatly enhanced under the same conditions. In this work, dithizone-modified GCE was investigated to determine trace levels of mercury. Dithizone-modified GCE has the following advantages: easy fabrication, low detection limit, fast response and good selectivity. Using this dithizone-modified GCE, trace levels of meycury in seawater samples were determined and the average recovery was 100.96%.