Determination of thallium in cement dust and sediment samples by differential-pulse anodic stripping voltammetry: a chemometric approach to linear calibration

Abstract

Differential-pulse anodic stripping voltammetry (DPASV) was used to determine TI in cement kiln dust and sediment samples. The separation of TI from the sample matrix was achieved by the extraction of Tl³⁺ into diethyl ether from an HBr—Br₂ medium. Initially, a mixture of HNO₃ and HF was used to digest the cement dust samples to cause volatilization of silica as SiF₄. The TI³⁺ was then reduced to TI⁺ using hydrazine sulfate prior to determination by DPASV. A calibration graph based on a deterministic relationship between the measured response y and the analyte concentration x(so that y=β₀+β_x+r) is also discussed using classical (or reverse) regression. The precision of parameter estimates of the model (b₀ and b: ŷ=b₀+bx) can be achieved by display of the diagonal elements of the hat matrix. Methods for computing the standard uncertainty in the predicted response s²_ŷn and in the concentration s²_x are also provided. Thallium concentrations of 700 ± 3.07, 395 ± 2.91 and 850 ± 2.59 ng g^–1 were found in the cement dust and sediment samples, respectively.