Kannamkumarath Sasi S, Wróbel Kazimierz, Wróbel Katarzyna, Caruso Joseph A
Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-1072, USA.
J Agric Food Chem. 2004 Mar 24;52(6):1458-63. doi: 10.1021/jf035180l.
In this work the quantitative determination and analytical speciation of arsenic were undertaken in different types of nuts, randomly purchased from local markets. The hardness of the whole nuts and high lipid content made the preparation of this material difficult for analysis. The lack of sample homogeneity caused irreproducible results. To improve the precision of analysis, arsenic was determined separately in nut oil and in the defatted sample. The lipids were extracted from the ground sample with the two portions of a mixture of chloroform and methanol (2:1). The defatted material was dried and ground again, yielding a fine powder. The nut oil was obtained by combining the two organic extracts and by evaporating the solvents. The two nut fractions were microwave digested, and total arsenic was determined by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained for oils from different types of nuts showed element concentration in the range 2.9-16.9 ng g(-)(1). Lower levels of arsenic were found in defatted material (<0.1 ng g(-)(1) with the exception of Brazil nuts purchased with and without shells, 3.0 and 2.8 ng g(-)(1) respectively). For speciation analysis of arsenic in nut oils, elemental species were extracted from 2 g of oil with 12 mL of chloroform/methanol (2:1) and 8 mL of deionized water. The aqueous layer, containing polar arsenic species, was evaporated and the residue dissolved and analyzed by ion chromatography-ICP-MS. The anion exchange chromatography enabled separation of As(III), dimethylarsinic acid (DMAs(V)), monomethylarsonic acid (MMAs(V)), and As(V) within 8 min. Several types of nuts were analyzed, including walnuts, Brazil nuts, almonds, cashews, pine nuts, peanuts, pistachio nuts, and sunflower seeds. The recovery for the speciation procedure was in the range 72.7-90.6%. The primary species found in the oil extracts were As(III) and As(V). The arsenic concentration levels in these two species were 0.7-12.7 and 0.5-4.3 ng g(-)(1), respectively. The contribution of As in DMAs(V) ranged from 0.1 +/- 0.1 ng g(-)(1) in walnuts to 1.3 +/- 0.3 ng g(-)(1) in pine nuts. MMAs(V) was not detected in almonds, peanuts, pine nuts, sunflower seeds, or walnuts, and the highest concentration was found in pistachio nuts (0.5 +/- 0.2 ng g(-)(1)).
在本研究中，对从当地市场随机购买的不同种类坚果中的砷进行了定量测定和分析形态研究。整个坚果的硬度和高脂肪含量使得该材料的制备难以用于分析。样品缺乏均匀性导致结果不可重现。为提高分析精度，分别对坚果油和脱脂样品中的砷进行了测定。用两份氯仿和甲醇的混合物（2:1）从磨碎的样品中提取脂质。将脱脂后的材料干燥并再次研磨，得到细粉。通过合并两份有机提取物并蒸发溶剂获得坚果油。对这两种坚果组分进行微波消解，并用电感耦合等离子体质谱法（ICP-MS）测定总砷。不同种类坚果油的测定结果表明元素浓度范围为2.9 - 16.9 ng g⁻¹。脱脂材料中砷的含量较低（<0.1 ng g⁻¹，但带壳和不带壳购买的巴西坚果除外，分别为3.0和2.8 ng g⁻¹）。对于坚果油中砷的形态分析，从2 g油中用12 mL氯仿/甲醇（2:1）和8 mL去离子水提取元素形态。含有极性砷形态的水层被蒸发，残留物溶解后用离子色谱 - ICP-MS分析。阴离子交换色谱能够在8分钟内分离出As(III)、二甲基砷酸（DMAs(V)）、一甲基砷酸（MMAs(V)）和As(V)。分析了几种类型的坚果，包括核桃、巴西坚果、杏仁、腰果、松子、花生、开心果和葵花籽。形态分析方法的回收率在72.7 - 90.6%范围内。油提取物中发现的主要形态是As(III)和As(V)。这两种形态中的砷浓度水平分别为0.7 - 12.7和0.5 - 4.3 ng g⁻¹。DMAs(V)中As的含量在核桃中为0.1 ± 0.1 ng g⁻¹，在松子中为1.3 ± 0.3 ng g⁻¹。在杏仁、花生、松子、葵花籽或核桃中未检测到MMAs(V)，在开心果中含量最高（0.5 ± 0.2 ng g⁻¹）。
