Use of Flow Injection Cold Vapour Generation and Preconcentration on Coated Graphite Tubes for the Determination of Mercury in Polluted Seawaters by Electrothermal Atomic Absorption Spectrometry

Abstract

Methods have been developed for the trace determination of total and inorganic mercury in natural waters by cold vapour generation–trapping and atomization in a graphite furnace by selective reduction with NaBH ₄ and SnCl ₂ . Iridium, tungstate and zirconium coated graphite tubes were investigated for the preconcentration of the mercury vapour. The carrier solution was 0.4 m of HCl, and 0.2% NaBH ₄ and 1.0% SnCl ₂ were used as reducing solutions for total and inorganic mercury, respectively. Using iridium coated graphite tubes characteristic masses of 300 and 240 pg for total and inorganic mercury, respectively, and detection limits of 90 and 60 ng l ^-1 for total and inorganic mercury were obtained for a 1500 µl sample volume. The precision was between 0.7 and 2.1%. Accuracy of method was confirmed by the analysis of IAEA/W-4 fresh water reference material.