A new method for quantifying iodine in a starch-iodine matrix

A rapid and sensitive method for quantifying iodine in intact starch granules using gas chromatography is described with detection limits as low as 0.2% (w/w) iodine in starch. Sample preparation includes NaBH₄ reduction of the various iodine species associated with starch to the colorless soluble iodide ion, followed by its quantitative derivatization to EtI using in CH₂Cl₂. Identification and quantification of EtI is carried out by extraction and injection of the EtI so generated in CH₂Cl₂ into a gas chromatography-mass spectrometer (GC-MS). Routine quantification of EtI was then performed using GC with a flame ionization detector (GC-FID). Results for different iodine:potassium iodide ratios of the initially bound iodine and for seven different starch matrices showed that in all cases regression coefficients for the standards were high (R² >0.96).