Hamano-Nagaoka Megumi, Hanaoka Ken'ichi, Usui Masakatsu, Nishimura Tsutomu, Maitani Tamio
National Institute of Health Sciences, Tokyo, Japan.
Shokuhin Eiseigaku Zasshi. 2008 Apr;49(2):88-94. doi: 10.3358/shokueishi.49.88.
Because there is a great difference between the toxicity of inorganic arsenic (As) and organic As in food, the JECFA has set a PTWI value for inorganic As (iAs) rather than for total As. The difference in As toxicity makes it necessary to extract iAs completely from food samples for toxicological analysis, but complete extraction of As from most foods including seaweed has not been achieved to date. We developed a partial-digestion method that uses nitric acid as a solvent in order to extract almost all arsenicals from the solid matrix of hijiki (Hizikia fusiforme, a brown alga) samples. In this method, organic As species were not converted into iAs. HPLC/ICP-MS was then used to determine the concentration of iAs. Total As was measured by hydride generation-atomic absorption spectrometry. The adopted conditions for 0.1 g of ground fine powder sample were: 2 mL of 0.3 mol/L nitric acid; heating, 80 degrees C for 1 hr. Intra-laboratory validation of the method showed good precision and accuracy. The repeatability and intermediate precision for iAs were 1.5% and 1.5%, respectively. The LOD and LOQ for iAs were 0.14 and 0.46 mg/kg dry weight, respectively. Recovery studies performed by spiking 0.5 mg/kg dry weight as the LOQ level and by spiking 3 mg/kg dry weight as the iAs concentration of an un-spiked hijiki sample showed good accuracy. The method was applied to hijiki samples after a water soaking process and a water soaking and simmering process. The results suggested that the As concentration in hijiki after both processes was lower than that before the treatments and that the water soaking and simmering process reduced the iAs concentration much more effectively than the water soaking process.
由于食品中无机砷（As）和有机砷的毒性存在很大差异，因此食品添加剂联合专家委员会（JECFA）设定的是无机砷（iAs）的暂定每周耐受摄入量（PTWI）值，而非总砷的PTWI值。砷毒性的差异使得有必要从食品样品中完全提取iAs用于毒理学分析，但迄今为止，尚未实现从包括海藻在内的大多数食品中完全提取砷。我们开发了一种部分消化法，该方法使用硝酸作为溶剂，以便从羊栖菜（Hizikia fusiforme，一种褐藻）样品的固体基质中提取几乎所有的砷化合物。在该方法中，有机砷物种不会转化为iAs。然后使用高效液相色谱/电感耦合等离子体质谱法（HPLC/ICP-MS）测定iAs的浓度。总砷通过氢化物发生原子吸收光谱法进行测定。对于0.1 g磨碎的细粉样品，采用的条件为：2 mL 0.3 mol/L硝酸；加热，80℃ 1小时。该方法的实验室内部验证显示出良好的精密度和准确度。iAs的重复性和中间精密度分别为1.5%和1.5%。iAs的检测限（LOD）和定量限（LOQ）分别为0.14和0.46 mg/kg干重。通过添加0.5 mg/kg干重作为定量限水平以及添加3 mg/kg干重作为未添加砷的羊栖菜样品的iAs浓度进行的回收率研究显示出良好的准确度。该方法应用于经过水浸泡过程以及水浸泡和炖煮过程后的羊栖菜样品。结果表明，经过这两个过程后，羊栖菜中的砷浓度均低于处理前，并且水浸泡和炖煮过程比水浸泡过程更有效地降低了iAs浓度。
