[Validation Study on an Improved Quantitative Method for Aflatoxins in Foods].

As an analytical method for aflatoxins in foods, the analytical method based on the notification by the director of the Food Safety Department, Pharmaceutical and Food Safety Bureau, Ministry of Health, Labour and Welfare (August 16, 2011) has been established. In order to improve the operability and analytical performance of the conventional method, this study aimed to construct an improved method that optimized selection of immunoaffinity column (IAC) and purifying condition, and omitted evaporation after the purification with IAC. In the recovery test performed by adding 2.5 ng/g of aflatoxin B1, B2, G1 and G2 standard solutions into 9 kinds of food samples, the improved method achieved the established target values: 77.0-99.7% of recovery, 1.7-5.6% of intra-assay coefficient of validation, and 0.9-3.6% of inter-assay of coefficient of variation, respectively. The improved method also achieved 4.3-10.5% greater recovery and 1.5 hours shorter preparation time than the conventional one. These results indicate applicability of the improved method for 9 kinds of foods and its efficacy as an analytical method for aflatoxins in foods.

[Nomenclature and Identification Method of Non-Permitted Dyes of Patent Blue Group].

Violation of the Food Sanitation Act regarding detection of Patent Blue V, which is one of the non-permitted dyes for food in Japan, in imported food occurs every year. With respect to the identification of dyes of Patent Blue group, in some cases, each dye has several different names, and in other cases, different dyes have the same name. Thus, there is a risk that the detected dye is misidentified with other dyes of Patent Blue group. In this study, nine commercial available dyes of Patent Blue group, including a reagent with unclear product information, were analyzed by TLC, HPLC and LC-MS/MS. The result showed that with all three methods, the dyes could be clearly identified into one of four types of blue dyes, i.e. Patent Blue V, Azure Blue VX, Isosulfan Blue and Alphazurine A. Unification of nomenclature would reduce the risk of misidentification of dyes of Patent Blue group.

Development and Validation of Simultaneous Analysis of Minerals and Toxic Elements in Foods by ICP-MS.

We have developed and validated an inductively coupled plasma-mass spectrometry (ICP-MS) method for the simultaneous analysis of minerals and toxic elements in foods. Food samples were digested by microwave irradiation to prepare solutions for measurement by ICP-MS. Optimal gas mode and internal standard for each element were selected as appropriate. The method was validated for eighteen elements in total using three certified standard reference materials, namely, Typical Japanese Diet, Rice Flour-Unpolished and Infant/Adult Nutritional Formula, according to the guidelines of the Ministry of Health, Labour and Welfare of Japan. The trueness and precision of the method were all within the acceptable limits, except for Na in Rice Flour-Unpolished.

[Determination of uranium in spinach].

After the severe accident at the Fukushima-1 Nuclear Power Plant in March 2011, radioactive contamination of food has become a matter of serious concern in Japan. There is considerable information about radioactive iodine and cesium, but little is known about uranium contamination. We determined uranium content in spinach by the Japanese official method (Manual on Radiation Measurement of Food in Emergency Situations). In the preliminary study, we confirmed that the use of a microwave digestion system for preparing the test solution of spinach could shorten the testing time and give acceptable results. The manual recommends the use of two elements (Tl and Bi) as internal standards for measurement of uranium by ICP-MS. We found that Tl was more suitable than Bi to quantify trace amounts of uranium in spinach. However, it was necessary to determine Tl or Bi concentrations in the sample before analysis, since some samples of spinach contained significant amounts of these elements. The uranium contents of 9 spinach samples bought in April and May 2011 were less than 10 µg/kg, which are very low compared to the provisional regulatory limit in Japan.