Formation of iodoacetic acids during cooking: interaction of iodized table salt with chlorinated drinking water

Iodoacetic and chloroiodoacetic acids were formed when municipal chlorinated tap water was allowed to react with iodized (with potassium iodide) table salt or with potassium iodide itself. Iodoacetic acid was recently shown to be a potent cytotoxic and genotoxic agent. For analysis, samples were extracted with t-amyl methyl ether and converted to the corresponding methyl esters using methanol and sulfuric acid. The concentration of iodoacetic acid was determined by gas chromatography-mass spectrometry (GC-MS) using an authentic standard. The identities of iodoacetic and chloroiodoacetic acids were further confirmed by gas chromatography-high-resolution mass spectrometry (GC-HRMS). Certain influences of sodium hypochlorite and humic acid as well as the concentration of potassium iodide on the yields of these acids were investigated. The concentration of iodoacetic acid in tap water samples boiled with 2 g l-1 of iodized table salt was found to be in the 1.5 microg l-1 range, whilst the concentration of chloroiodoacetic acid was estimated to be three to five times lower.