电感耦合等离子体串联质谱法分析麻疯树油中的多元素
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摘要
工业化和现代化进程的加快消耗了大量能源,对能源的高度依赖性导致了全球化石能源需求的快速增长,随着非再生化石能源的日渐枯竭,迫切需要大力发展可再生能源以调整现有能源结构。作为国际上研究最多的生物柴油,麻疯树油是国内外公认的最有可能替代化石能源的再生能源,具有极大的开发潜力。麻疯树油中的微量元素在燃烧过程中会影响发动机的性能,并在尾气排放过程中决定了对环境所造成的污染程度。本文以获得麻疯树油中多元素的含量为目的,建立应用电感耦合等离子体串联质谱(ICP-MS/MS)法准确测定麻疯树油中低水平Na,Si,P,S,Cl,K,Ti,V,As含量的分析方法。采用微波密闭消解系统,依次向麻疯树油样品中加入硝酸和双氧水进行消解。详细地研究了各待测元素在不同分析模式下检出限(DL)和背景等效浓度(BEC)的变化情况,在MS/MS模式下,通过向碰撞/反应池(CRC)中加入反应气可以完全消除质谱干扰。选择O_2为反应气,P~+,S~+,Ti~+,V~+,As~+与O_2的反应均为放热过程,能发生质量转移自发生成PO~+,SO~+,TiO~+,VO~+,AsO~+,利用O_2质量转移法消除质谱干扰;选择H_2为反应气,Cl~+与H_2反应能自发生成ClH_2~+,利用H_2质量转移法消除质谱干扰,而Na~+,Si~+,K~+均不能与H_2发生质量转移反应,利用H_2原位质量法消除质谱干扰。选择Sc为内标元素校正了分析过程中的基体效应。通过考察不同反应气流速下各元素的BEC变化,优化了反应气流速,O_2的最佳流速为0.45mL·min~(-1),H_2的最佳流速为7.5mL·min~(-1)。在优化的实验条件下获得Na,Si,P,S,Cl,K,Ti,V,As的检出限分别为6.41,37.3,24.6,118,530,7.96,7.61,0.34,3.20ng·L~(-1),各元素在0~50μg·L~(-1)范围内的线性相关系数(R~2)≥0.999 8,方法具有良好的线性关系。采用三水平加标回收实验来验证方法的准确性和精密度,所有元素的加标回收率在91.2%~108%之间,相对标准偏差(RSD)为1.9%~4.6%,表明所建立的方法准确性好,精密度高。通过对来自中国不同地区的4个麻疯树油样品进行测定,结果显示,4个麻疯树油样品中P含量≤164ng·g~(-1),S含量≤2310ng·g~(-1),碱(Na~+K)含量≤1 690ng·g~(-1),三项指标均达到了中国生物柴油调和燃料国家标准,欧Ⅳ生物柴油标准,德国生物柴油标准和美国生物柴油标准。这项研究为麻疯树油中多种微量元素的准确分析提供了一种方便可行的新方法,为麻疯树油的质量控制和安全应用提供了科学的理论依据。
According to the development of industrialization and modernization,much more conventional fossil energy resource is excess consumed,with the depletion of non-renewable energy resource,the development of new renewable energy was urgently needed.As one of the hottest concerned biodiesel resources,Jatropha curcas L.oil was thought as the most possible renewable energy to replace conventional fossil energy resource.The trace elements in Jatropha oil might affect the performance of engine,and deteriorate environment.In order to obtain the contents of multi-elements in Jatropha curcas L.oil,an analytical method was established for accurately determination of Si,P,S,Cr and As in Jatropha curcas L.oil by using inductively coupled plasma tandem mass spectrometry(ICP-MS/MS).Jatropha oil was processed by using microwave-assisted acid-digested reaction with nitric acid and hydrogen peroxide.The changes of detection limit(DL)and background equivalent concentration(BEC)for multi-elements in different analysis modes were optimized in detail.In the MS/MS mode,O_2 was introduced into the collision reaction cell(CRC),then Si~+,P~+,S~+,Cr~+and As~+were reacted with O_2to generate SiO_2~+,PO~+,SO~+,CrO~+and AsO~+respectively;thus mass spectrometry interference can be eliminated by mass shift caused by reactions.As Cl~+can reaction with H_2to form ClH_2~+,while Na~+,Si~+,K~+elements cannot reaction with it,the mass shift caused by reaction with H_2 was selected to eliminate mass spectrum interference.Sc was selected as internal standard element to correct the matrix effects.The flow rates in the CRC of different reaction gas were optimized by considering the background equivalent concentration(BEC)of analytes,and the best gas flow rate for O_2and H_2 were 0.45mL·min~(-1),and 7.5mL·min~(-1),respectively.The DL for Na,Si,P,S,Cl,K,Ti,V,and As were 6.41,37.3,24.6,118,530,7.96,7.61,0.34,and 3.20ng·L~(-1),respectively,under the optimized conditions.The linear correlation coefficient(R~2)of analytes were≥0.999 8in the range 0~50μg·L~(-1).The recovery of all elements ranged from 91.2%to 108%,and the relative standard deviation(RSD)was ranged from 1.9%to 4.6%.These results showed that the proposed method was accuracy and precise.Analytical results obtained from different original Jatropha curcas L.oil showed that the contents of element P,S,and(Na+K)were≤164,2 310,and 1 690ng·g~(-1),respectively.These indexes were much lower than those of the contents in the conventional fossil energy resource,and reached the standards of Chinese national standard of biodiesel,European IV biodiesel standard,German biodiesel standard,and American biodiesel standard.This study proposed a new approach for the determination of multi-element in Jatropha curcas L.oil with convenience and feasibility,and provided a scientific basis for the quality control and safety application of Jatropha curcas L.oil.
According to the development of industrialization and modernization,much more conventional fossil energy resource is excess consumed,with the depletion of non-renewable energy resource,the development of new renewable energy was urgently needed.As one of the hottest concerned biodiesel resources,Jatropha curcas L.oil was thought as the most possible renewable energy to replace conventional fossil energy resource.The trace elements in Jatropha oil might affect the performance of engine,and deteriorate environment.In order to obtain the contents of multi-elements in Jatropha curcas L.oil,an analytical method was established for accurately determination of Si,P,S,Cr and As in Jatropha curcas L.oil by using inductively coupled plasma tandem mass spectrometry(ICP-MS/MS).Jatropha oil was processed by using microwave-assisted acid-digested reaction with nitric acid and hydrogen peroxide.The changes of detection limit(DL)and background equivalent concentration(BEC)for multi-elements in different analysis modes were optimized in detail.In the MS/MS mode,O_2 was introduced into the collision reaction cell(CRC),then Si~+,P~+,S~+,Cr~+and As~+were reacted with O_2to generate SiO_2~+,PO~+,SO~+,CrO~+and AsO~+respectively;thus mass spectrometry interference can be eliminated by mass shift caused by reactions.As Cl~+can reaction with H_2to form ClH_2~+,while Na~+,Si~+,K~+elements cannot reaction with it,the mass shift caused by reaction with H_2 was selected to eliminate mass spectrum interference.Sc was selected as internal standard element to correct the matrix effects.The flow rates in the CRC of different reaction gas were optimized by considering the background equivalent concentration(BEC)of analytes,and the best gas flow rate for O_2and H_2 were 0.45mL·min~(-1),and 7.5mL·min~(-1),respectively.The DL for Na,Si,P,S,Cl,K,Ti,V,and As were 6.41,37.3,24.6,118,530,7.96,7.61,0.34,and 3.20ng·L~(-1),respectively,under the optimized conditions.The linear correlation coefficient(R~2)of analytes were≥0.999 8in the range 0~50μg·L~(-1).The recovery of all elements ranged from 91.2%to 108%,and the relative standard deviation(RSD)was ranged from 1.9%to 4.6%.These results showed that the proposed method was accuracy and precise.Analytical results obtained from different original Jatropha curcas L.oil showed that the contents of element P,S,and(Na+K)were≤164,2 310,and 1 690ng·g~(-1),respectively.These indexes were much lower than those of the contents in the conventional fossil energy resource,and reached the standards of Chinese national standard of biodiesel,European IV biodiesel standard,German biodiesel standard,and American biodiesel standard.This study proposed a new approach for the determination of multi-element in Jatropha curcas L.oil with convenience and feasibility,and provided a scientific basis for the quality control and safety application of Jatropha curcas L.oil.
引文
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[3]King A J,He W,Cuevas J A,et al.J.Exp.Bot.,2009,60(10):2897.
[4]Fernandez C M,Fiori L,Ramos M J,et al.J.Supercrit.Fluid.,2015,97:100.
[5]HU Xue-ling,WEI Teng-you,MAO Ge-qing,et al(胡雪玲,韦藤幼,毛格清,等).Fine Chemicals(精细化工),2011,28(10):974.
[6]Aminul Islam A K M,Yaakob Z,Anuar N,et al.Energ.Source.Part A,2015,37(14):1550.
[7]Berchmans H J,Hirata S.Bioresource Technol.,2008,99(6):1716.
[8]Lyra F H,Brandao G P,Pessoa H M,et al.Microchem.J.,2010,96(1):180.
[9]Chaves E S,Santos E J D,Araujo R G O,et al.Microchem.J.,2010,96(1):71.
[10]Pillay A E,Elkadi M,Fok S C,et al.Fuel,2012,97(7):385.
[11]WANG Xiao-wei,LIU Jing-fu,GUAN Hong,et al(王晓伟,刘景富,关红,等).Spectroscopy and Spectral Analysis(光谱学与光谱分析),2016,36(2):527.
[12]Min S C,Ryu J S,Lee S W,et al.J.Anal.Atom.Spectrom.,2012,27(11):1955.
[13]Wysocka I,Vassileva E.Spectrochim.Acta B,2017,128:1.
[14]Fu L,Shi S Y,Chen X Q.Spectrochim.Acta B,2017,133:34.
[15]Bolea-Fernandez E,Phan K,Balcaen L,et al.Anal.Chim.Acta,2016,941:1.
[16]Fu L,Shi S Y,Chen X Q.Food Chem.,2018,245:692.
[17]Virgilio A,Amais R S,Amaral C D B,et al.Spectrochim.Acta B,2016,126:31.
[18]Fu L,Xie H L,Shi S Y,et al.Spectrochim.Acta B,2018,144:1.
[19]FU Liang,SHI Shu-yun(符靓,施树云).Chinese Journal of Analytical Chemistry(分析化学),2017,45(8):1222.
[20]Walkner C,Gratzer R,Meisel T,et al.Org.Geochem.,2017,103:22.