Pieter Scheelings

Determination of iodine in selected foods and diets by inductively coupled plasma-mass spectrometry*

Iodine is an essential trace element, and its deficiency has caused concern in many countries. Foods are the principal source of iodine, and its levels are generally low. In this study, selected food items were obtained from food market outlets in Brisbane, Australia. Food samples of dietary intakes of selected healthy children in Brisbane, Australia, were also collected for analysis and assessment of iodine nutritional status. In Australia, there has been little study on iodine dietary intakes, particularly in young children. The aims of this study were to provide further information on iodine levels in foods for Australian food composition data, and to estimate the iodine daily intakes of selected healthy children. Food samples were analyzed for iodine concentrations using inductively coupled plasma-mass spectrometry (ICP-MS) after alkaline digestion with tetramethylammonium hydroxide (TMAH), and the method was validated using a certified reference material of nonfat milk (NIST, SRM 1549). The results of this study indicated a wide variation of iodine in foodstuffs, which ranged from <0.02 to 0.101 mg/kg for cereals, 87 to 299 μg/kg for milk, and 86 to 271 μg/kg for cheese products. The study also showed that the daily intakes of iodine in these children (n = 15) varied widely and ranged from 36.9 to 288.1 μg/day (mean ± s.d, 93.1 ± 76.7 μg/day).

Arsenic in rice and diets of children

Levels of arsenic in Australian and imported rice (n = 36) were evaluated using inductively coupled plasma mass spectrometry (ICP-MS) for total arsenic and a hyphenated high-performance liquid chromatography ICP-MS system for arsenic species. The study also assessed the daily intake of total As from diets of healthy children (n = 15), collected over three consecutive days. A wide variation of total As levels (range: <0.05–0.42 mg/kg) in Australian and imported rice was found. The mean level of total As (0.24 ± 0.09 mg/kg, n = 10) in the Australian rice was relatively higher than imported rice from other countries (0.09 ± 0.04 mg/kg, n = 26). The mean level (0.25 ± 0.08 mg/kg, n = 7) of dimethylarsenic acid was considerably higher than that of inorganic As (III) (0.07 ± 0.03 mg/kg, n = 7) in the Australian rice. Children’s daily intakes of total As varied widely, ranging from 1.7 to 31.2 (11.5 ± 8.9 µg/day), which was comparable to other countries.

Quality Control and Assurance Issues Relating to Sampling and Analysis in a Total Diet Study

The integrity of TDS data is a function of food representativeness, laboratory competence, analytical validation and critical evaluation of laboratory data. This chapter deals with the analytical quality control and quality assurance procedures for handling total diet study samples and discusses the relevance of measurement uncertainties associated with evaluating the analytical data.