Head-space single drop microextraction combined with gas chromatography with an electron capture detector for determination of iodine in infant formulas

Abstract

Headspace single-drop microextraction (HS-SDME) coupled with gas chromatography with electron capture detection (GC-ECD) was used for quantification of total iodine in milk based samples of infant formula. In this procedure 3 μL of a mixture containing 1-octanol and 3-pentanone was exposed to the headspace of a 5 mL acidic (H₂SO₄, 2 mol L⁻¹) aqueous solution containing 1.5 mol L⁻¹ ZnSO₄ for 30 minutes followed by addition of 1 mL of 1 mol L⁻¹ H₂O₂ for in situ generation of iodine. Optimization of the microextraction system was carried out using the Taguchi experimental design method. The limit of detection was determined to be 250 ng L⁻¹ with an enrichment factor of 150. The repeatability, expressed as a relative standard deviation, was 1.9% (n = 6). The linear calibration working range was between 0.75 and 2000 μg L⁻¹ (r² = 0.998). The method was successfully applied for determination of iodine in milk based samples of infant formula.