Determination of total selenium in food samples by d-CPE and HG-AFS

• A d-CPE method coupled with HG-AFS was firstly developed for determination of Se.
• The adverse effects of the surfactant on determination are eliminated.
• A mixture of 16% (v/v) HCl and 20% (v/v) H2O2 releases Se(IV) from Se-APDC complex.

A dual-cloud point extraction (d-CPE) procedure was developed for the simultaneous preconcentration and determination of trace level Se in food samples by hydride generation-atomic fluorescence spectrometry (HG-AFS). The Se(IV) was complexed with ammonium pyrrolidinedithiocarbamate (APDC) in a Triton X-114 surfactant-rich phase, which was then treated with a mixture of 16% (v/v) HCl and 20% (v/v) H2O2. This converted the Se(IV)-APDC into free Se(IV), which was back extracted into an aqueous phase at the second cloud point extraction stage. This aqueous phase was analyzed directly by HG-AFS. Optimization of the experimental conditions gave a limit of detection of 0.023 μg L−1 with an enhancement factor of 11.8 when 50 mL of sample solution was preconcentrated to 3 mL. The relative standard deviation was 4.04% (c = 6.0 μg L−1, n = 10). The proposed method was applied to determine the Se contents in twelve food samples with satisfactory recoveries of 95.6–105.2%.