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Analysis of foods for iodine: interlaboratory study
Journal - Association of Official Analytical Chemists
|September 1, 1979
Summary
Accurate iodine analysis in food is crucial for nutritional labeling. A study revealed significant discrepancies among laboratories using various methods, highlighting the need for improved food iodine testing techniques.
Area of Science:
- Analytical Chemistry
- Food Science
- Nutritional Analysis
Background:
- Accurate quantification of iodine in foods at low levels (≤1 ppm) is essential for nutritional labeling.
- Existing analytical methods for food iodine determination lack sufficient accuracy and reproducibility.
Purpose of the Study:
- To assess the current status of iodine analysis in diverse food matrices.
- To identify discrepancies in iodine determination across multiple laboratories and methodologies.
Main Methods:
- Seven food samples from different classes were analyzed by eight laboratories.
- Six laboratories employed variations of the cerium-arsenic-iodine (Ce-As-I) catalytic method with alkaline dry ashing.
- Two laboratories utilized neutron activation analysis (NAA) with distinct radiochemical separations.
Main Results:
- Wide discrepancies in analytical results were observed between laboratories, with a mean inter-laboratory relative standard deviation of 77.9%.
- Intra-laboratory precision was better (19.1% RSD), but overall results varied significantly.
- Neutron activation analysis (NAA) showed only marginally better precision than the chemical method.
- Reported iodine levels varied widely, from 0.0089 to 0.65 ppm across laboratories and samples.
- Methodological differences, specifically NAA and manual colorimetry, potentially correlated with obtained iodine levels.
Conclusions:
- Current methods for determining iodine in foods, including NAA and chemical methods, exhibit significant variability and lack the required accuracy for nutritional labeling.
- There is a critical need for the development and validation of a precise and reproducible method for low-level iodine determination in food products.