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 Et3O+BF4- 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).

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