Survey of total mercury in foods from Taiwan containing red mould rice (Monascus) using a direct mercury analyser (DMA)

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Total mercury concentrations in 69 red mould rice (Monascus) food samples purchased in Taipei, Taiwan, were determined using the direct mercury analyser (DMA) method. The highest mean levels of total mercury in these samples were observed in samples of canned roast eel (20 µg kg−1), soy fibrous product (14 µg kg−1), red mould rice (8.5 µg kg−1), cereal (7.6 µg kg−1), dried pork fibre (7.5 µg kg−1), and dietary supplement (7.2 µg kg−1). All samples analysed had mercury levels below the limit of 50 µg kg−1 for food standards in rice, edible oil, and fat of Taiwan. The mercury concentration in the Monascus foods differed widely between different food varieties, suggesting that external contamination and raw materials are the main sources of mercury. This study shows that DMA is a simple method proposed for the determination of total mercury in foods containing Monascus. The method requires no sample pre-treatment, and it minimizes potential sources of contamination. The data (42 ± 2 µg kg−1) obtained from five analyses of a standard reference material (apple leaves, NIST-1515) showed good agreement with the certified reference value (44 ± 4 µg kg−1) provided by the US National Institute of Standards and Technology (NIST). The precision based on the analysis of standard reference material was 4.1%; the average recovery was 95%.