Stoichiometric determination of moisture in edible oils by Mid-FTIR spectroscopy

A simple and accurate method for the determination of moisture in edible oils by differential FTIR spectroscopy has been devised based on the stoichiometric reaction of the moisture in oil with toluenesulfonyl isocyanate (TSI) to produce CO2. Calibration standards were devised by gravimetrically spiking dry dioxane with water, followed by the addition of neat TSI and examination of the differential spectra relative to the dry dioxane. In the method, CO2 peak area changes are measured at 2335 cm−1 and were shown to be related to the amount of moisture added, with any CO2 inherent to residual moisture in the dry dioxane subtracted ratioed out. CO2 volatility issues were determined to be minimal, with the overall SD of dioxane calibrations being ∼18 ppm over a range of 0–1000 ppm. Gravimetrically blended dry and water-saturated oils analysed in a similar manner produced linear CO2 responses with SD's of