绿茶中28种元素含量测定的消解条件比较
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摘要
前处理条件对准确测定样品中多矿质元素含量至关重要,本研究设置4种酸消解体系(HNO_3、HNO_3-H_2O_2、HNO_3-HF、HNO_3-HF-H_2O_2)及5组消解温度(100～120℃、100～120～140℃、100～130～150℃、100～130～160℃、100～120～140～160～180℃),探究不同消解条件对绿茶标准物质GBW10052中28种多元素浓度的影响。结果表明,不同酸消解体系及消解温度下的各元素浓度均有差异,相比Ca、K、Fe、Mg、Na等主量元素,As、Cr、Cs、Cd、Li、Ni、Se、Rb、Tb、Th、Tl、U、V、Y等微量及痕量元素浓度变化更显著。HNO_3中各元素浓度最低,14个元素的相对误差(Relative error,RE)大于25%;混合酸消解效果较好,相比于HNO_3,混合酸中大部分元素浓度更接近参考值。HNO_3-H_2O_2中,除Mo、U、Se、V、Si、Pb外,其余元素浓度增大,RE减小; HNO_3-HF中U、V、Si、Li、Zn、Sr、Cr等浓度继续增大,RE持续减小,As、Pb、Cd等浓度减小,RE增大; HNO_3-HF-H_2O_2中As、Pb、Cd等持续更减小,RE增大,其余元素浓度更接近参考值,与HNO_3-HF相比,HNO_3-HF-H_2O_2中各元素RE减小,但变化不显著。升温能促进溶液中部分多元素消解,以HNO_3-HF-H_2O_2为例,消解温度为100～140℃的体系对获取主量元素更有利;高温消解对微量及痕量元素影响较大,尤其是As、Pb、Cd、Cr等易挥发元素,当温度超过140℃时,As、Pb、Cd、Cr亏损严重,RE均高于25%。因此,应该根据目标元素选择相应的消解条件,从而提高分析结果的准确性。
Pretreatment conditions are of great importance to measure contents of mineral elements in samples precisely. This study employed four acid digestion systems of different acid reagents( HNO_3,HNO_3-H_2O_2,HNO_3-HF and HNO_3-HF-H_2O_2) and five digestion temperature setups( 100-120℃,100-120-140℃,100-130-150℃,100-130-160℃ and 100-120-140-160-180℃) to explore effects of different digestion conditions on test results of contents of 28 elements in a standard green tea substance( GBW10052). The results showed that measured contents of elements in the standard sample varied notably under different digestion systems or/and digestion temperatures,variations of minor elements,such as As,Cr,Cs,Cd,Li,Ni,Se,Rb,Tb,Th,Tl,U,V and Y,were more significant than those of major elements,such as Ca,K,Fe,Mg and Na. Briefly,measured concentrations for all elements were the lowest and relative errors of 14 elements were higher than 25% in the pure HNO_3 digestion system while measured element concentrations by mixed acid digestion systems were more closely equal to the reference values,implying mixed acid digestion systems provided better results than the single acid digestion system did. It was found that,compared to the single acid digestion system,the HNO_3-H_2O_2 mixed acid digestion system reduced relative errors of all elements except Mo,U,Se,V,Si and Pb; measured concentrations of U,V,Si,Li,Zn,Sr and Cr increased while corresponding relative errors decreased in the HNO_3-HF digestion system; the digestion system measured concentrations more closer to their reference values for all elements except volatile elements such as As,Pb and Cd. Rising digestion temperature promoted the digestion efficiency of target elements. Take the HNO_3-HF-H_2O_2 digestion system as the example,the digestion temperature range of 100-140℃ was optimum for major elements,when the temperature was set above 140℃,it impaired the results of minor and trace elements,especially the volatile elements such as As,Pb,Cd and Cr. In summary,we suggest that the appropriate digestion condition should be selected on comprehensively considerations of object elements to improve the analytical precision.
Pretreatment conditions are of great importance to measure contents of mineral elements in samples precisely. This study employed four acid digestion systems of different acid reagents( HNO_3,HNO_3-H_2O_2,HNO_3-HF and HNO_3-HF-H_2O_2) and five digestion temperature setups( 100-120℃,100-120-140℃,100-130-150℃,100-130-160℃ and 100-120-140-160-180℃) to explore effects of different digestion conditions on test results of contents of 28 elements in a standard green tea substance( GBW10052). The results showed that measured contents of elements in the standard sample varied notably under different digestion systems or/and digestion temperatures,variations of minor elements,such as As,Cr,Cs,Cd,Li,Ni,Se,Rb,Tb,Th,Tl,U,V and Y,were more significant than those of major elements,such as Ca,K,Fe,Mg and Na. Briefly,measured concentrations for all elements were the lowest and relative errors of 14 elements were higher than 25% in the pure HNO_3 digestion system while measured element concentrations by mixed acid digestion systems were more closely equal to the reference values,implying mixed acid digestion systems provided better results than the single acid digestion system did. It was found that,compared to the single acid digestion system,the HNO_3-H_2O_2 mixed acid digestion system reduced relative errors of all elements except Mo,U,Se,V,Si and Pb; measured concentrations of U,V,Si,Li,Zn,Sr and Cr increased while corresponding relative errors decreased in the HNO_3-HF digestion system; the digestion system measured concentrations more closer to their reference values for all elements except volatile elements such as As,Pb and Cd. Rising digestion temperature promoted the digestion efficiency of target elements. Take the HNO_3-HF-H_2O_2 digestion system as the example,the digestion temperature range of 100-140℃ was optimum for major elements,when the temperature was set above 140℃,it impaired the results of minor and trace elements,especially the volatile elements such as As,Pb,Cd and Cr. In summary,we suggest that the appropriate digestion condition should be selected on comprehensively considerations of object elements to improve the analytical precision.
引文
[1]童成英，何守阳，丁虎．茶叶产地与品质的元素、同位素鉴别技术研究进展[J]．生态学杂志，2018(5):1574-1583.
[2] Shen F M. Element composition of tea leaves and tea infusions and its impact on health[J]. Bulletin of Environmental Contamination and Toxicology,2008,80(3):300-304.
[3]谭和平，张苏敏，陈能武，等．茶叶中稀土元素的电感耦合等离子体质谱检测方法研究[J]．中国测试，2008,34(2):85-88.
[4]郭丽萍．微波消解-电感耦合等离子体发射光谱法测定茶叶中的微量元素[J]．食品科技，2013(5):303-307.
[5]刘藏吉良，李志伟，赵伟，等．风冷回流消解-电感耦合等离子体质谱法同时测定植物样品中46个元素[J]．岩矿测试，2012,31(2):247-252.
[6]韩恒斌，刘淑琴，张淑贞，等．环境标样茶叶、茶树叶的制备及均匀性测定[J]．环境化学，1988(6):17-23.
[7]唐爱玲．微波消解-四级杆电感耦合等离子体质谱法测定茶叶中有益和有害金属[J]．安徽农业科学，2017,45(31):91-93.
[8] Welna M. Comparison of samples preparation strategies in the multi-elemental analysis of tea by spectrometric methods[J]. Food Research International,2013,53(2):922-930.
[9] Gao Y,Oshita K,Lee P A,et al. Development of column-pretreatment chelating resins for matrix elimination/multi-element determination by inductively coupled plasma-mass spectrometry[J]. Analyst,2002,127(12):1713-1719.
[10] Isegawa J,Hayashi T,Matsuda A,et al. Study of a microwave digestion method(pretreatment for trace element-analysis)using biological standard reference materials[J]. Biomedical Research on Trace Elements,1998,9(3):175-176.
[11]石元值，马立锋，韩文炎，等．茶叶重金属元素检测中样品采集及其前处理[J]．中国茶叶，2008,30(1):6-7.
[12] Chen L,Lin D L,Gao Z P,et al. The distribution of rare earth elements in tea garden soil and oolong tea[J]. Journal of Fujian Agriculture&Forestry University,2011,40(6):595-601.
[13] Bian K,Ruilian Y U,Gongren H U,et al. Geochemical characteristics of rare earth elements in the vertical profile of soil of the tea garden in anxi area,China[J]. Earth&Environment,2017,2(45):145-150.
[14] Xu H Z,Chen Z W,Fang L. Study on the regional characteristics of the rare earth elements distribution in tea[J]. Hubei Agricultural Sciences,2007,46(5):779-781.
[15] Li F,Shan X,Zhang T,et al. Evaluation of plant availability of rare earth elements in soils by chemical fractionation and multiple regression analysis[J]. Environmental Pollution,1998,102(2-3):269-277.
[16] Lagad R A,Dasari K B,Alamelu D,et al. Evaluation of soil to tea plant elemental correlation using instrumental neutron activation analysis[J].Journal of Radioanalytical&Nuclear Chemistry,2014,302(3):1507-1512.
[17] Yabutani T,Ji S,Mouri F,et al. Multielement determination of trace elements in coastal seawater by inductively coupled plasma mass spectrometry with aid of chelating resin preconcentration[J]. Bulletin of the Chemical Society of Japan,1999,72(10):2253-2260.
[18] Costal M,Gouveia S T,Nóbrega J A. Comparison of heating extraction procedures for Al,Ca,Mg,and Mn in tea samples[J]. Analytical Sciences,2002,18(3):313-318.
[19] Yang Y. Application of high pressure hermetic seal technique for the digestion and analysis of salt scale in power plants[J]. Chinese Journal of Analytical Chemistry,2001,29(8):961-963.
[20] Lamble K. Determination of trace metals in tea using both microwave digestion at atmospheric pressure and inductively coupled plasma atomic emission spectrometry[J]. Analyst,1995,120(2):413-417.
[21] Gregory E,Filippo C,Andrea R,et al. Statistical analysis of drainage density from digital terrain data[J]. Geomorphology,2001,36(3):187-202.
[22] Adrian W J. A comparison of a wet pressure digestion method with other commonly used wet and dry-ashing methods[J]. Analyst,1973,98(1164):213-216.
[23]张雨桐，张文，周迎楠，等．全自动消解仪-电感耦合等离子体质谱法对食品生物成分中多种金属元素的分析[J]．食品安全导刊，2015(36):171-172.
[24]李国傲，何咏，陈雪，等．全自动消解测定土壤/沉积物中的有机碳[J]．环境工程，2016,34(5):152-155.
[25]高婧，刘利亚，李雪春，等．全自动消解-超声处理技术在测定谷物中总汞的应用[J]．中国卫生检验杂志，2015(18):3072-3074.
[26]张更宇，洪涛，薛健，等．全自动消解-电感耦合等离子体质谱法测定土壤16种元素[J]．化工环保，2018(54):428-432.
[27]国家食品质量安全监督检验中心．GB/T 23199-2008茶叶中稀土元素的测定-电感耦合等离子体发射光谱法和电感耦合等离子体质谱法[S]．北京:国家食品质量安全监督检验中心，2008.
[28]中国测试技术研究．GB/T 30376-2013茶叶中铁、锰、铜、锌、钙、镁、钾、钠、磷、硫的测定-电感耦合等离子体原子发射光谱法[S]．杭州:中华全国供销合作总社杭州茶叶研究院，2013.
[29]中华人民共和国浙江出入境检验检疫．SN/T 2056-2008进出口茶叶中铅、砷、镉、铜、铁含量的测定-电感耦合等离子体原子发射光谱法[S]．浙江:中华人民共和国浙江出入境检验检疫局，2008.
[30]唐尚明．污染植物的预处理—植物试样的消解[J]．农业环境科学学报，1982,(4):20-23.
[31]李刚，高明远，诸堃，等．微波消解-电感耦合等离子体质谱法测定植物样品中微量元素[J]．岩矿测试，2010,29(1):17-22.
[32]孙长霞，吴成亮，黄广远，等．预处理方法对可食牲植物样品中微量元素测定结果的影响[J]．食品工业科技，2009,(10):314-317.
[33] Donkoh A,Moughan P J,Smith W C. Comparison of the slaughter method and simple T-piece cannulation of the terminal ileum for determining ileal amino acid digestibility in meat and bone meal for the growing pig[J]. Animal Feed Science&Technology,1994,49(1-2):43-56.
[34]孟时贤，邓飞跃，杨远，等．电感耦合等离子体发射光谱法测定铅锌矿中15个主次量元素[J]．岩矿测试，2015,34(1):48-54.
[35]张玉玲，王松君，王璞珺，等．微波消解植物灰分与环境土壤中微量元素的ICP—AES方法研究[J]．光谱学与光谱分析，2009,29(8):2240-2243.
[36]孙德忠，安子怡，许春雪，等．四种前处理方法对电感耦合等离子体质谱测定植物样品中27种微量元素的影响[J]．岩矿测试，2012,31(6):961-966.
[37]马生凤，温宏利，巩爱华，等．大试管回流消解-等离子体发射光谱/质谱法测定植物样品中多元素[J]．岩矿测试，2007,26(3):183-187.
[38] Sastre J,Sahuquillo A,Vidal M,et al. Determination of Cd,Cu,Pb and Zn in environmental samples:microwave-assisted total digestion versus aqua regia and nitric acid extraction[J]. Analytica Chimica Acta,2002,462(1):59-72.
[39] Costal L M,Santos D C,Hatje V,et al. Focused-microwave-assisted acid digestion:evaluation of losses of volatile elements in marine invertebrate samples[J]. Journal of Food Composition&Analysis,2009,22(3):238-241.
[40] Liu L X. Determination of calcium,barium and zinc in lube additives by noncomplete digestion-flame atomic spectrometry[J]. Metallurgical Analysis,2005,25(4):10-17.
[2] Shen F M. Element composition of tea leaves and tea infusions and its impact on health[J]. Bulletin of Environmental Contamination and Toxicology,2008,80(3):300-304.
[3]谭和平，张苏敏，陈能武，等．茶叶中稀土元素的电感耦合等离子体质谱检测方法研究[J]．中国测试，2008,34(2):85-88.
[4]郭丽萍．微波消解-电感耦合等离子体发射光谱法测定茶叶中的微量元素[J]．食品科技，2013(5):303-307.
[5]刘藏吉良，李志伟，赵伟，等．风冷回流消解-电感耦合等离子体质谱法同时测定植物样品中46个元素[J]．岩矿测试，2012,31(2):247-252.
[6]韩恒斌，刘淑琴，张淑贞，等．环境标样茶叶、茶树叶的制备及均匀性测定[J]．环境化学，1988(6):17-23.
[7]唐爱玲．微波消解-四级杆电感耦合等离子体质谱法测定茶叶中有益和有害金属[J]．安徽农业科学，2017,45(31):91-93.
[8] Welna M. Comparison of samples preparation strategies in the multi-elemental analysis of tea by spectrometric methods[J]. Food Research International,2013,53(2):922-930.
[9] Gao Y,Oshita K,Lee P A,et al. Development of column-pretreatment chelating resins for matrix elimination/multi-element determination by inductively coupled plasma-mass spectrometry[J]. Analyst,2002,127(12):1713-1719.
[10] Isegawa J,Hayashi T,Matsuda A,et al. Study of a microwave digestion method(pretreatment for trace element-analysis)using biological standard reference materials[J]. Biomedical Research on Trace Elements,1998,9(3):175-176.
[11]石元值，马立锋，韩文炎，等．茶叶重金属元素检测中样品采集及其前处理[J]．中国茶叶，2008,30(1):6-7.
[12] Chen L,Lin D L,Gao Z P,et al. The distribution of rare earth elements in tea garden soil and oolong tea[J]. Journal of Fujian Agriculture&Forestry University,2011,40(6):595-601.
[13] Bian K,Ruilian Y U,Gongren H U,et al. Geochemical characteristics of rare earth elements in the vertical profile of soil of the tea garden in anxi area,China[J]. Earth&Environment,2017,2(45):145-150.
[14] Xu H Z,Chen Z W,Fang L. Study on the regional characteristics of the rare earth elements distribution in tea[J]. Hubei Agricultural Sciences,2007,46(5):779-781.
[15] Li F,Shan X,Zhang T,et al. Evaluation of plant availability of rare earth elements in soils by chemical fractionation and multiple regression analysis[J]. Environmental Pollution,1998,102(2-3):269-277.
[16] Lagad R A,Dasari K B,Alamelu D,et al. Evaluation of soil to tea plant elemental correlation using instrumental neutron activation analysis[J].Journal of Radioanalytical&Nuclear Chemistry,2014,302(3):1507-1512.
[17] Yabutani T,Ji S,Mouri F,et al. Multielement determination of trace elements in coastal seawater by inductively coupled plasma mass spectrometry with aid of chelating resin preconcentration[J]. Bulletin of the Chemical Society of Japan,1999,72(10):2253-2260.
[18] Costal M,Gouveia S T,Nóbrega J A. Comparison of heating extraction procedures for Al,Ca,Mg,and Mn in tea samples[J]. Analytical Sciences,2002,18(3):313-318.
[19] Yang Y. Application of high pressure hermetic seal technique for the digestion and analysis of salt scale in power plants[J]. Chinese Journal of Analytical Chemistry,2001,29(8):961-963.
[20] Lamble K. Determination of trace metals in tea using both microwave digestion at atmospheric pressure and inductively coupled plasma atomic emission spectrometry[J]. Analyst,1995,120(2):413-417.
[21] Gregory E,Filippo C,Andrea R,et al. Statistical analysis of drainage density from digital terrain data[J]. Geomorphology,2001,36(3):187-202.
[22] Adrian W J. A comparison of a wet pressure digestion method with other commonly used wet and dry-ashing methods[J]. Analyst,1973,98(1164):213-216.
[23]张雨桐，张文，周迎楠，等．全自动消解仪-电感耦合等离子体质谱法对食品生物成分中多种金属元素的分析[J]．食品安全导刊，2015(36):171-172.
[24]李国傲，何咏，陈雪，等．全自动消解测定土壤/沉积物中的有机碳[J]．环境工程，2016,34(5):152-155.
[25]高婧，刘利亚，李雪春，等．全自动消解-超声处理技术在测定谷物中总汞的应用[J]．中国卫生检验杂志，2015(18):3072-3074.
[26]张更宇，洪涛，薛健，等．全自动消解-电感耦合等离子体质谱法测定土壤16种元素[J]．化工环保，2018(54):428-432.
[27]国家食品质量安全监督检验中心．GB/T 23199-2008茶叶中稀土元素的测定-电感耦合等离子体发射光谱法和电感耦合等离子体质谱法[S]．北京:国家食品质量安全监督检验中心，2008.
[28]中国测试技术研究．GB/T 30376-2013茶叶中铁、锰、铜、锌、钙、镁、钾、钠、磷、硫的测定-电感耦合等离子体原子发射光谱法[S]．杭州:中华全国供销合作总社杭州茶叶研究院，2013.
[29]中华人民共和国浙江出入境检验检疫．SN/T 2056-2008进出口茶叶中铅、砷、镉、铜、铁含量的测定-电感耦合等离子体原子发射光谱法[S]．浙江:中华人民共和国浙江出入境检验检疫局，2008.
[30]唐尚明．污染植物的预处理—植物试样的消解[J]．农业环境科学学报，1982,(4):20-23.
[31]李刚，高明远，诸堃，等．微波消解-电感耦合等离子体质谱法测定植物样品中微量元素[J]．岩矿测试，2010,29(1):17-22.
[32]孙长霞，吴成亮，黄广远，等．预处理方法对可食牲植物样品中微量元素测定结果的影响[J]．食品工业科技，2009,(10):314-317.
[33] Donkoh A,Moughan P J,Smith W C. Comparison of the slaughter method and simple T-piece cannulation of the terminal ileum for determining ileal amino acid digestibility in meat and bone meal for the growing pig[J]. Animal Feed Science&Technology,1994,49(1-2):43-56.
[34]孟时贤，邓飞跃，杨远，等．电感耦合等离子体发射光谱法测定铅锌矿中15个主次量元素[J]．岩矿测试，2015,34(1):48-54.
[35]张玉玲，王松君，王璞珺，等．微波消解植物灰分与环境土壤中微量元素的ICP—AES方法研究[J]．光谱学与光谱分析，2009,29(8):2240-2243.
[36]孙德忠，安子怡，许春雪，等．四种前处理方法对电感耦合等离子体质谱测定植物样品中27种微量元素的影响[J]．岩矿测试，2012,31(6):961-966.
[37]马生凤，温宏利，巩爱华，等．大试管回流消解-等离子体发射光谱/质谱法测定植物样品中多元素[J]．岩矿测试，2007,26(3):183-187.
[38] Sastre J,Sahuquillo A,Vidal M,et al. Determination of Cd,Cu,Pb and Zn in environmental samples:microwave-assisted total digestion versus aqua regia and nitric acid extraction[J]. Analytica Chimica Acta,2002,462(1):59-72.
[39] Costal L M,Santos D C,Hatje V,et al. Focused-microwave-assisted acid digestion:evaluation of losses of volatile elements in marine invertebrate samples[J]. Journal of Food Composition&Analysis,2009,22(3):238-241.
[40] Liu L X. Determination of calcium,barium and zinc in lube additives by noncomplete digestion-flame atomic spectrometry[J]. Metallurgical Analysis,2005,25(4):10-17.
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