Solutions were delivered into the graphite tube by means of an AS-72 autosampler. For sample analyses, a 10-μL volume of a chemical modifier solution of 5 μg Pd and 3 μg Mg (solutions of 10 g L1 of Pd(NO3) and Mg(NO3)2, both from Merck) was co-injected into the graphite furnace with 10 μL of samples or analytical solutions. A Titrisol standard solution of 1000 mg L1 of Se (Merck) was used to prepare the reference analytical solutions in 0.14 M HNO3.