Browsing by Subject "ICP-MS"

The aim of this Master’s Thesis was to develop a method for determining iodine from food. The method was developed and validated for the Finnish Food Safety Authority Evira. The literature review focused on the chemistry of iodine and its occurrence in nature and food as well as its physiological importance to humans. Different methods used in iodine analyses were also discussed with emphasis placed on ICP-MS. Sample matrices used in the experimental study were milks with different fat contents, egg, cheese and fish. Two different milk powders (BCR®-150 and BCR®-063R) and fish muscle (ERM BB®-422) were used as certified reference materials. Milk and cheese samples were dissolved in 0.5 % ammonium hydroxide, left overnight and shaked for two hours before the analysis. Cheese and fish samples were prepared using microwave digestion with ammonium hydroxide as the reagent. After both sample preparation methods the samples were in 0.5 % ammonium hydroxide which was also used as the rinsing solution of the ICP-MS-instrument. Tellurium was used as an internal standard. Validation parameters determined were method specificity, selectivity, repeatability, reproducibility, accuracy, measuring range, linearity, LOD and LOQ. Measurement uncertainty of the method was also estimated. The method was proven to be specific and selective to measure iodine. The accuracy of the method for egg and milk samples was 90.3% and the recovery of added iodine in these samples was 98.7%. For the fish and cheese sample method these results were 86.9% and 102.3%. Both sample preparation methods gave repeatable and reproducible results. LOQ for the milk and egg sample method was 0.02 mg kg-1 and for the fish and cheese method 0.06 mg kg-1. The expanded measurement uncertainty for all matrices was 10–29%. The validation proved the method to be fit for purpose and reliable. The method will be used for measuring the iodine content of actual food samples.