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DETERMINATION OF METALS IN COMPOSITE DIET SAMPLES BY ICP-MS
Citation:
Melnyk, L J., J N. Morgan, R. Fernando, O. Akinbo, AND E. D. Pellizzari. DETERMINATION OF METALS IN COMPOSITE DIET SAMPLES BY ICP-MS. JOURNAL OF AOAC INTERNATIONAL 86(2):439-447, (2003).
Impact/Purpose:
The overall objective of this research is to support NERL's human exposure measurement and exposure modeling efforts by reducing the amount of uncertainty in the dietary measurements critically needed for improved risk assessment. Specifically, the research provides the tools needed to collect and analyze food samples and to design and understand dietary measurements. The current specific objectives are:
1. to investigate more efficient methods for characterizing population exposures in dietary measurements studies (short-term subtask initiated in FY00; extramural);
2. to develop and improve analytical methods for contaminants in composite food samples collected in dietary measurements studies (long-term subtask; in-house);
3. to improve the model and food database system used in measurements studies for estimating dietary exposure and identifying sources (long-term subtask; extramural).
Description:
In order to assess an individual's total exposure to contaminants in the environment, it is essential that the contribution of dietary exposure be quantified. As a result, USEPA's National Exposure Research Laboratory has initiated a program to develop methods to measure chemical pollutants in dietary samples collected from individuals. Previous efforts have utilized inductively coupled plasma (ICP)-atomic emission spectrometry (AES) and graphite furnace atomic absorption spectroscopy (GFAAS) techniques for determination of metals in composite diets. However, there is often a trade-off between sensitivity and sample throughput with these techniques. ICP-mass spectrometry (MS) offers sensitvity comparable to or better than GFAAS while retaining sample throughput comparable to ICP-AES. This study evaluated the applicability of ICP-MS techniques for the determination of metals in composite diets. An ICP-MS method for the determination of aluminum, arsenic, barium, cadmium, chromium, copper, lead, manganese, nickel, vanadium, and zinc is presented. The procedure utilizes atmospheric pressure microwave digestion to solubilize analytes in homogenized composite diet samples followed by ICP-MS analysis. Recovery of certified elements from standard reference materials (SRMs) ranged from 92-119% with relative standard deviation (RSD) ranging from 0.4-1.9%. Recovery of elements from fortified composite diet samples ranged from 75-129% with RSDs ranging from 1-11.3%. LODs ranged from 1 - 1700 ng/g, with high values due to significant amounts of certain elements naturally present in composite diets. Results of this study demonstrate that low resolution ICP-MS provides precise and accurate measurements of the elements tested in composite diet samples.