Zirconium-iridium coating as a permanent modifier for determination of tin in stream sediment, oyster tissue and total diet slurries by electrothermal atomic absorption spectrometry

A slurry atomization procedure has been developed for the determination of total tin in different types of environmental samples such as stream sediment, oyster tissue and total diet using a Zr-Ir permanent chemical modifier and transverse heated electrothermal atomic absorption spectrometry (THETAAS). Reference materials such as GBW07312 Stream Sediment, NIST SRM 1566a Oyster Tissue and NIST SRM 1548 Total Diet were used to validate the method. Slurries were prepared in a mixture of 1% v/v HNO3, 2% v/v HCl and 0.2% Triton X-100 solution by using magnetic stirring and ultrasonication. Addition of Triton X-100 after sonication of the slurries rather than before was found to improve the precision of measurement. With the Zr-Ir-coated tube the characteristics mass obtained was 38 +/- 2 pg, which is an improvement of nearly five times compared to using an uncoated tube. The tube lifetime using aqueous standards and slurries was nearly 500 atomization cycles. The Zr-Ir permanent chemical modifier was found to effectively reduce the interference effects from chloride, phosphate and silica, as nearly 90-100% recovery was obtained in the presence of 100 mg of the matrix. In the presence of 100 mg of sulfide, aluminum nitrate and sodium silicate, 30-60% recovery was obtained, indicating the presence of matrix interferences.