On-line preconcentration and determination of mercury by flow injection inductively coupled plasma atomic emission spectrometry

Abstract

An inductively coupled plasma atomic emission spectrometry (ICP-AES) flow injection method for the determination of trace levels of mercury in biological materials is described based on complexation of the metal ion with 1,5-bis(di-2-pyridyl)methylene thiocarbonohydrazide (DPTH) and its subsequent on-line extraction into isobutyl methyl ketone (IBMK). The organic phase (containing the complex) is mixed on-line with SnCl₂ in dimethylformamide. The optimum experimental conditions are evaluated for the continuous extraction of Hg^II, the direct generation of mercury vapour from the organic phase and the final determination of this element by ICP-AES. The detection limit for mercury is 0.002 µg ml^–1 and the calibration is linear from 0.01 to 5 µg ml^–1. The precision of the method (evaluated as the relative standard deviation obtained after analysing ten series of ten replicates) was ± 3.3% at the 0.25 µg ml^–1 level of Hg^II. The effect of various inorganic ions and some organic masking substances on the determination of mercury by the proposed method is examined under the optimum working conditions. The tolerance limits found show that mercury can be determined in the presence of a variety of ions including most of those that commonly occur with mercury in natural samples.