title: Tandem focused ultrasound (TFU) combined with fast furnace analysis as an improved methodology for total mercury determination in human urine by electrothermal-atomic absorption spectrometry.
abstract: A new sample preparation procedure based on tandem (that is, different diameter probe sonicators used in the same sample treatment) focused ultrasound (TFU) for mercury separation, preconcentration and back-extraction in aqueous solution from human urine has been developed. The urine is first oxidized with KMnO(4)/HCl/focused ultrasound (6mm probe). Secondly, the mercury is extracted and preconcentrated with dithizone and cyclohexane. Finally, the mercury is back-extracted and preconcentrated again with the aid of focused ultrasound (3mm probe). The procedure allows determining mercury by electrothermal atomic absorption spectrometry with fast furnace analysis and calibration against aqueous standards. Matrix modification is provided by the chemicals used in the sample treatment. The procedure is accomplished with low sample volume (8.5ml). Low volume and low concentration reagents are used. The sample treatment is rapid (less than 3min per sample) and avoids the use of organic phase in the graphite furnace. The preconcentration factor used in this work was 14. The limit of detection and the limit of quantification in urine were, respectively, 0.27 and 0.9mugl(-1). The relative standard deviation of aqueous standards (n=10) was 4% for a concentration of 100mugl(-1) and 5% for a concentration of 400mugl(-1). Recoveries from spiked urine with inorganic mercury, methyl-mercury, phenyl-mercury and diphenyl-mercury ranged from 86 to 98%.
authors.affiliation: Centro de Quimica Estrutural, Instituto Superior Técnico de Lisboa, Universidade Técnica de Lisboa, Torre Sul. 11 Andar. Avda. Rovisco Pais, 1049-001 Lisbon, Portugal.
authors.forename: J L
authors.initials: JL
authors.lastname: Capelo
authors.forename: C D
authors.initials: CD
authors.lastname: Dos Reis
authors.forename: C
authors.initials: C
authors.lastname: Maduro
authors.forename: A
authors.initials: A
authors.lastname: Mota