Determination of trace metals in urine with an on-line ultrasound-assisted digestion system combined with a flow-injection preconcentration manifold coupled to flame atomic absorption spectrometry.

A flow analysis method with on-line sample digestion/minicolumn preconcentration/flame atomic absorption spectrometry is described for the determination of trace metals in urine. First, urine sample was on-line ultrasound-assisted digested exploiting the stopped-flow mode, and then the metals were preconcentrated passing the pre-treated sample through a minicolumn containing a chelating resin. A home-made minicolumn of commercially available imminodiacetic functional group resin, Chelite Che was used to preconcentrate trace metals (Cu, Fe, Mn and Ni) from urine. The proposed procedure allowed the determination of the metals with detection limits of 0.5, 1.1, 0.8 and 0.8microgL(-1), for Cu, Fe, Mn and Ni, respectively. The precision based on replicate analysis was less than +/-10.0%, and the enrichment factor obtained was between 21.3 (Mn) and 44.1 (Ni), for sample volumes between 2.5 and 5.0mL, and an eluent volume of 110microL. This procedure was applied for determination of metals in urine of workers exposed to welding fumes and urine of unexposed persons (urine control).

Flow injection determination of lead and cadmium in hair samples from workers exposed to welding fumes.

A flow injection procedure involving continuous acid leaching for lead and cadmium determination in hair samples of persons in permanent contact with a polluted workplace environment by flame atomic absorption spectrometry is proposed. Variables such as sonication time, nature and concentration of the acid solution used as leaching solution, leaching temperature, flow-rate of the continuous manifold, leaching solution volume and hair particle size were simultaneously studied by applying a Plackett-Burman design approach. Results showed that nitric acid concentration (leaching solution), leaching temperature and sonication time were statistically significant variables (confidence interval of 95%). These last two variables were finally optimised by using a central composite design. The proposed procedure allowed the determination of cadmium and lead with limits of detection 0.1 and 1.0 microgg(-1), respectively. The accuracy of the developed procedure was evaluated by the analysis of a certified reference material (CRM 397, human hair, from the BCR). The proposed method was applied with satisfactory results to the determination of Cd and Pb in human hair samples of workers exposed to welding fumes.

Fast ultrasound-assisted extraction of copper, iron, manganese and zinc from human hair samples prior to flow injection flame atomic absorption spectrometric detection.

A dynamic ultrasound-assisted extraction procedure utilizing diluted nitric acid was developed for the determination of copper, iron, manganese and zinc in human hair taken from workers in permanent contact with a polluted environment. The extraction unit of the dynamic ultrasound-assisted extraction system contains a minicolumn into which a specified amount of hair (5-50 mg) is placed. Once inserted into the continuous manifold, trace metals were extracted at 3 mL min(-1) with 3 mol L(-1) nitric acid under the action of ultrasound for 2 min for zinc and 3 min for copper, iron and manganese determination, and using an ultrasonic water-bath temperature of 70 degrees C for zinc and 80 degrees C for copper, iron and manganese determination. The system permits the direct analysis of hair and yields concentrations with relative standard deviations of <3% (n = 11). The applicability of the procedure was verified by analysing human hair samples from workers exposed to welding fumes, and its accuracy was assessed through comparison with a conventional sample dissolution procedure and the use of a certified reference material (BCR 397, human hair).