Preparation of the diphenylcarbazone-functionalized silica gel and its application to on-line selective solid-phase extraction and determination of mercury by flow-injection spectrophotometry

A new solid-phase extractor, diphenylcarbazone-functionalized silica gel has been synthesized and confirmed by IR and Raman spectrometry. The new solid-phase extractor is found to be stable in 1-6 mol L−1 HCl or H2SO4, and also in common organic solvents. It can be used to separate and enrich Hg(II) selectively from eight metal ions with similar characteristics such as Cd(II), Ni(II), Co(II), Mn(II), Pb(II), Zn(II), Cu(II) and Fe(III). The pre-concentration factor is as high as 500. The results show that this new solid extractor has a good stability and can be reused for many times without decreasing its extraction percentage. The micro-column packed with diphenylcarbazone-functionalized silica gel was used for on-line solid-phase extraction and determination of mercury in real samples by flow-injection spectrophotometry. At the optimal conditions, the linear range and the detection limit for the determination of Hg(II) is found to be 1-1500 and 0.90 ng mL−1, respectively. The relative standard deviation of 11 replicate measurements is less than 3%. The proposed method was demonstrated to be simple, fast, selective, low cost and less pollution.