Use of polytetrafluoroethylene slurry for silica matrix removal in ETAAS direct determination of trace cobalt and nickel in silicon dioxide powder

Abstract

A novel method for the direct determination of trace Co and Ni in SiO ₂ powder by slurry sampling ETAAS was developed. At high temperature of the graphite furnace, a PTFE slurry in HNO ₃ was used as a fluorinating reagent to convert the silica matrix into high-volatility fluoride, which was subsequently evaporated by selective vaporization prior to the atomization of analytes. In this case, the severe interference of the matrix on the vaporization and atomization of analytes was reduced significantly, and chemical attack of the excess of silica matrix on the graphite tube was also minimized. The proposed method was successfully applied to the determination of trace Co and Ni in SiO ₂ powder with aqueous calibration and minimum chemical pre-treatment. For the direct analysis of high purity SiO ₂ powder, the detect limits of Co and Ni were 18.8 and 35.0 ng g ^–1 , respectively. The analysis of NIES CRM2 Pond Sediment confirmed the reliability of the approach.