Vapor Generation Accessory VGA–77 Operation manual

VGA–774.4.7 TinThe best results for tin will generally be obtained from solutionsprepared in 1% tartaric acid. Also, a study (2) has shown that theaddition of L-cysteine greatly improves tin determination by hydridegeneration. The L-cysteine reduces metal interferences and improvesprecision and sensitivity. Some improvement in calibration linearityhas also been noted.The concentration of acid pumped into the VGA-77 is also critical intin determinations, and the analytical signal will be severely depressedat concentrations higher than 0.5 M. (Refer to section 4.2.1 ‘Acidconcentration’.)When determining tin using the AA technique, it is essential todetermine tin at the 286.3 nm wavelength and 0.2 nm slit since thiswill provide the best combination of analytical sensitivity anddynamic range. The 235.5 nm line commonly used for flame andfurnace AA gives very poor sensitivity and the 224.6 nm line showsvery little increase in analytical response above approximately 0.3absorbance.Reductant container: NaBH 40.6%NaOH 0.5%Acid container: 0.5 M HClSample1% Tartaric acidcontrolled pH (2.0 to 3.0)Alternative method 2Reductant container: NaBH 40.5%NaOH 0.1%Acid container: D.I. H 2OSample1% Tartaric acid1% L-cysteine4.4.8 Additional notes1. If arsenic and selenium are both to be determined from the samesample, determine selenium first and avoid KI in samples orstandards. You can then determine arsenic after the KI reductionstep and any other appropriate treatment (such as the addition ofurea if excess nitric acid is present).Publication date: May 2004 4-11