Investigations on Freon-assisted atomization of refractory analytes (Cr,Mo,Ti,V) in multielement electrothermal atomic absorption spectrometry

摘要

Premixed ,1% Freon in argon inner gas of various composition (CC1_2F_2,CHC1F_2,CHF_3) was applied to graphite furnace atomizer to minimize unfavorable effects of carbide formation,such as signal tailing and memory effects in the simultaneous determination of Cr,Mo,Ti and V refractory analytes by electrothermal atomic absorption spectrometry using a multielement atomic absorption spectrometer.The effect of these gaseous additives was investigated when applied separately in atomization,pyrolysis and clean-out steps.The halogenation effects were analytically useful only under the precondition of using Ar-H_2 outer gas to the furnace to all heating steps,and also using this gas in the pre-atomization (drying,pyrolysis) steps.Optimum analytical performance was obtained when mixtures of 1% Freon in argon were applied just before and during the atomization step at a flow rate of 50 mL min~(-1) and 2% hydrogen was used as purge gas.Using optimum conditions,signal tailings and carry-over contamination were reduced effectively and good precision (relative standard deviation below 1%) could be attained.Applying 1% CHC1F2 and an atomization temperature of 2550 °C,the characteristic masses obtained for simple aqueous solutions were 8.8 pg for Cr,17 pg for Mo,160 pg for Ti,and 74 pg for V.The limits of detection were 0.05,0.2,2.3 and 0.5 mu g L~(-1) for Cr,Mo,Ti and V,respectively.The developed method was applied to the analysis of digests of advanced ceramics.The accuracy of the procedure was confirmed by analyzing the certified reference material ERM-ED 102 (Boron Carbide Powder) and a silicon nitride powder distributed in the inter-laboratory comparison CCQM-P74.