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

A novel method for the direct determination of trace Co and Ni in SiO2 powd er by slurry sampling ETAAS was developed. At high temperature of the graph ite furnace, a PTFE slurry in HNO3 was used as a fluorinating reagent to co nvert the silica matrix into high-volatility fluoride, which was subsequent ly evaporated by selective vaporization prior to the atomization of analyte s. 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 SiO2 powder with aqueous calibration and minimum chemical pre-tre atment. For the direct analysis of high purity SiO2 powder, the detect limi ts 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.