微波消解-电感耦合等离子体质谱法测定蔬菜中铬、镉、砷、铅、汞的含量
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摘要
取经洗净、切成小段并用四分法取样和粉碎的蔬菜样品1.000g于PTFE消解容器中,加入硝酸7mL在消解仪中于120℃恒温保持30min。随后将容器移入微波消解仪中,在1 000 W功率下按设定程序消解25min。冷却后用硝酸(2+98)溶液将消解完全的溶液定容至25.0mL,用电感耦合等离子体质谱法测定样品中Cr、Cd、As、Pb、Hg的含量。对测定中遇到的同量异位素干扰,选取相应的原子丰度较高的同位素~(52)Cr,~(111)Cd,~(75)As,~(208)Pb及~(202)Hg作为被测元素,可在一定程序上降低此类干扰。此外,蔬菜中常含有C、H、O、N、Cl、S、Mo等元素,能与载气中的Ar结合产生多原子离子干扰。因此,在测定~(111)Cd,~(52)Cr,~(75)As时,采用DRC模式并以NH_3作为反应气可消除此类干扰。测定~(202)Hg及~(208)Pb时无此类干扰,故采用STD模式。对样品的基体干扰,采用在线内标加入法予以校正。在DRC模式下测定~(111)Cd,~(52)Cr及~(75)As时可能产生新干扰,采用设定RPq值可排除此类干扰。试验结果表明:所测定的5种元素的质量浓度在一定范围内与各元素的分析信号强度之间呈线性关系,其检出限(3s/k)在0.2～3.2μg·kg~(-1)之间。按标准加入法进行回收试验,测得回收率在92.9%～108%之间,测定值的相对标准偏差(n=5)在1.2%～5.8%之间。
Vegetable was collected from the growing area,washed with water,cut into segments and sampled by quartering;the sample was then crushed and 1.000 g of the crushed sample was treated with 7 mL of HNO_3 in a constant temperature digester at 120 ℃ for 30 min.The digested solution was then removed to a microwave digester to have a further digestion of the sample under 1 000 Wfor 25 min.After cooling,the digested solution was diluted with HNO_3(2+98)solution and its volume was made up to 25.0 mL,which was used for ICPMS determination of Cr,Cd,As,Pb and Hg.Isotopes having high relative abundance(i.e.~(52)Cr,~(111)Cd,~(75)As,~(208)Pb and ~(202)Hg)were selected as the species in the respective determinations to overcome effects of isobaric interferences to a definite extent.Besides,elements of C,H,O,N,Cl,S and Mo,which were existed in vegetables very often,might form polyatomic ions with Ar in the carrier gas,making interferences of polyatomic ions.DRC mode with gaseous NH_3 as reactant in the MS determinations of ~(111)Cd,~(52)Cr and ~(75)As was adopted to eliminate such interferences.STD mode was applied to the MS determinations of ~(202)Hg and ~(208)Pb,since no polyatomic ion interference was encountered in these cases.Moreover,to overcome some new interferences arised in the DRC mode of determinations,setting up to RPqvalues was found to be effective.It was shown by the testing results,linear relationships between values of intensities of analytical signals and the mass concentrations of the 5 related elements were found in the definite ranges,with their detection limits(3 s/k)ranging from 0.2 to 3.2μg·kg-1.Recovery was tested by standard addition method,giving results of recovery in the range from 92.9% to 108%,and RSDs(n=5)in the range of 1.2%-5.8%.
Vegetable was collected from the growing area,washed with water,cut into segments and sampled by quartering;the sample was then crushed and 1.000 g of the crushed sample was treated with 7 mL of HNO_3 in a constant temperature digester at 120 ℃ for 30 min.The digested solution was then removed to a microwave digester to have a further digestion of the sample under 1 000 Wfor 25 min.After cooling,the digested solution was diluted with HNO_3(2+98)solution and its volume was made up to 25.0 mL,which was used for ICPMS determination of Cr,Cd,As,Pb and Hg.Isotopes having high relative abundance(i.e.~(52)Cr,~(111)Cd,~(75)As,~(208)Pb and ~(202)Hg)were selected as the species in the respective determinations to overcome effects of isobaric interferences to a definite extent.Besides,elements of C,H,O,N,Cl,S and Mo,which were existed in vegetables very often,might form polyatomic ions with Ar in the carrier gas,making interferences of polyatomic ions.DRC mode with gaseous NH_3 as reactant in the MS determinations of ~(111)Cd,~(52)Cr and ~(75)As was adopted to eliminate such interferences.STD mode was applied to the MS determinations of ~(202)Hg and ~(208)Pb,since no polyatomic ion interference was encountered in these cases.Moreover,to overcome some new interferences arised in the DRC mode of determinations,setting up to RPqvalues was found to be effective.It was shown by the testing results,linear relationships between values of intensities of analytical signals and the mass concentrations of the 5 related elements were found in the definite ranges,with their detection limits(3 s/k)ranging from 0.2 to 3.2μg·kg-1.Recovery was tested by standard addition method,giving results of recovery in the range from 92.9% to 108%,and RSDs(n=5)in the range of 1.2%-5.8%.
引文
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[11]石杰,宋庆国,赵开楼,等.断续流动氢化物发生-原子荧光光谱法同时测定茶叶中的痕量铋、镉[J].食品科学,2005,26(7):163-165.
[12]李金英,石磊,鲁盛会,等.电感耦合等离子体质谱(ICP-MS)及其联用技术研究进展[J].中国无机分析化学,2012,2(2):1-5.
[13]王小如.电感耦合等离子体质谱应用实例[M].北京:化学工业出版社,2005.
[14]GB 5009.268-2016食品安全国家标准食品中多元素的测定[S].
[15]GB 2762-2017食品中污染物限量[S].
[2]IAVICOLI I,CARELLI G,STANEKIII E J,et al.Effects of per os lead acetate administration on mouse hepatocyte survival[J].Toxicology Letters,2002,129(1/2):143-149.
[3]RAI V,VAJPAYEE P,SINGH S N,et al.Effect of chromium accumulation on photosynthetic pigments,oxidative stress defense system,nitrate reduction,proline level and eugenol content of Ocimum tenuiflorum L[J].Plant Science,2004,167(5):1159-1169.
[4]胡曙光,苏祖俭,黄伟雄,等.食品中重金属元素痕量分析消解技术的进展与应用[J].食品安全质量检测学报,2014,5(5):1270-1278.
[5]张改荣,向志文.原子吸收光谱法测定龙须菜中7种微量元素含量[J].光谱实验室,2007,24(6):1005-1008.
[6]盛若虹.微波高压消解双道原子荧光法测定蔬菜总砷和汞[J].光谱实验室,2006,23(3):638-640.
[7]许萍,牟仁祥,曹赵云,等.密闭式微波消解方法综述[J].光谱实验室,2009,26(1):57-59.
[8]韩冷.快速测定几种痕量金属元素方法的研究[D].哈尔滨:哈尔滨师范大学,2010.
[9]KARIMA B,NATIVIDAD R M,BADREDINE S,et al.Characterization of trace metals in vegetables by graphite furnace atomic absorption spectrometry after closed vessel microwave digestion[J].Food Chemistry,2009,116(2):590-594.
[10]TOYAMA-KATO Y,YOSHIDA K,FUJIMORI E,et al.Analysis of metal elements of hydrangea sepals at various growing stages by ICP-AES[J].Biochemical Engineering Journal,2003,14(3):237-241.
[11]石杰,宋庆国,赵开楼,等.断续流动氢化物发生-原子荧光光谱法同时测定茶叶中的痕量铋、镉[J].食品科学,2005,26(7):163-165.
[12]李金英,石磊,鲁盛会,等.电感耦合等离子体质谱(ICP-MS)及其联用技术研究进展[J].中国无机分析化学,2012,2(2):1-5.
[13]王小如.电感耦合等离子体质谱应用实例[M].北京:化学工业出版社,2005.
[14]GB 5009.268-2016食品安全国家标准食品中多元素的测定[S].
[15]GB 2762-2017食品中污染物限量[S].