Spectrofluorimetric method for the determination of the total mercury content in sediment and soil

A spectrofluorimetric method based on fluorescence quenching of rhodamine B with Hg(II) in the presence of potassium iodide for the determination of the total mercury in sediment and soil is described. All forms of mercury are pre-oxidized to ionic mercury by acidic potassium permanganate and finally complete oxidation is achieved by potassium persulphate and heating. Hg(II) was reduced by tin(II) chloride and vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. Fluorescence quenching of rhodamine B is measured in the absorption solution at an excitation wavelength of 485 nm and an emission wavelength of 586 nm. The proposed method gives good recovery of added mercury (mean 98.0%), good repeatability (RSD 1.64%) and reproducibility (RSD 2.17%) and low detection limit (0.7 ng Hg ml−1 of measuring solution). No significant concentration of total mercury present in sediment and soil samples from the largest deposits of oil in Croatia have been found.