头发氢稳定同位素比值检测的标准品选择研究
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摘要
人头发中稳定同位素比值可追溯人的生活时空信息,构建可供比对的中国人头发稳定同位素比值数据库,对法庭科学研究和公安侦查意义重大。稳定同位素比值检测常因各实验室对样本的预处理和测量值校正方法不同等原因,影响其精确度和真实性,以致数据重现性较低而难以建库比对。本研究利用元素分析-同位素质谱技术(EA-IRMS),以中国人头发氢稳定同位素比值(δ~2H)检测方法为例,系统论证了其标准品选择和真值校正算法。首先,选择具有固体氢同位素真值的6种国际标准品(USGS42、USGS43、CBS、KHS、EMAP1和EMAP2)进行适合性评估;依据现有所测和文献报道的中国人头发的δ~2H值范围(-55‰～-80‰),选取3种真值囊括待测样品极负值、极正值和中间值的标准品进行组合,比较不同组合的标准曲线系数和拟合度R~2;经对比6种标准品组合,论证可得USGS42、USGS43和CBS组合的标准校正曲线拟合度R~2和标准曲线系数最适合且稳定。同时,选择北京和上海的两家实验室,历时4个月,共进行35次重复验证。结果表明,该标准品组合的校正曲线拟合度高、稳定性好(R~2≥0.999 7),适合作为头发δ~2H的标准校正方法,可作为中国人头发δ~2H数据库构建的推荐方法。本实验甄选标准品和真值校正曲线的思路亦可为其他稳定同位素标准库的建立提供参考。
The stable isotope ratio in human hair can be used to trace back the spatial and temporal information of human life. The construction of a comparable database of stable isotope ratio in Chinese human hair has a great significance for forensic science research and public security investigation. However, the interference of sample pretreatment and the difference of normalization methods affected the accuracy and reproducibility of hydrogen isotope ratio measurement and made it difficult to make comparison between laboratories. This research were based on the elemental analysis-isotope ratio mass spectrometer technic(EA-IRMS), and it systematically demonstrate the selection of hydrogen isotopic reference materials and the normalization method of hydrogen isotopic compositions to isotope reference scales. Firstly, six international reference materials(USGS42, USGS43, CBS, KHS, EMAP1 and EMAP2) were selected to evaluate their suitability. Then, according to the range of δ~2H values(-55‰～-80‰) of Chinese human hair measured and reported in the literatures, three of them were selected, including the minimum, maximum and middle values of the samples. Finally, by comparing the six reference materials combinations(CBS/USGS42/USGS43, CBS/USGS42/EMA-P1, CBS/USGS42/KHS, EMA-P2/USGS42/USGS43, EMA-P2/USGS42/EMA-P1 and EMA-P2/USGS42/KHS), it is proved that the standard calibration curves fitting R~2(1.000 0±0.000 0, n=4) of USGS42, USGS43 and CBS combinations are the highest, and the coefficients(1.061 8±0.006 6, n=4) of them are the most stability than other combinations by utilizing linear regression of multiple-point normalization method. At the same time, two laboratories in Beijing and Shanghai were selected to carry out 35 repeated validations. The results show that the multiple-point normalization method of the standard combination has the highest fitting degree and good stability(R~2≥0.999 7, n=35). It is suitable for the normalization method of hair δ~2H and can be used as a recommended method for the construction of Chinese human hair δ~2H database. The idea of selecting isotopic reference materials and the normalization method of hydrogen isotopic compositions to isotope reference scales can also provide reference for the establishment of other stable isotope ratio database.
The stable isotope ratio in human hair can be used to trace back the spatial and temporal information of human life. The construction of a comparable database of stable isotope ratio in Chinese human hair has a great significance for forensic science research and public security investigation. However, the interference of sample pretreatment and the difference of normalization methods affected the accuracy and reproducibility of hydrogen isotope ratio measurement and made it difficult to make comparison between laboratories. This research were based on the elemental analysis-isotope ratio mass spectrometer technic(EA-IRMS), and it systematically demonstrate the selection of hydrogen isotopic reference materials and the normalization method of hydrogen isotopic compositions to isotope reference scales. Firstly, six international reference materials(USGS42, USGS43, CBS, KHS, EMAP1 and EMAP2) were selected to evaluate their suitability. Then, according to the range of δ~2H values(-55‰～-80‰) of Chinese human hair measured and reported in the literatures, three of them were selected, including the minimum, maximum and middle values of the samples. Finally, by comparing the six reference materials combinations(CBS/USGS42/USGS43, CBS/USGS42/EMA-P1, CBS/USGS42/KHS, EMA-P2/USGS42/USGS43, EMA-P2/USGS42/EMA-P1 and EMA-P2/USGS42/KHS), it is proved that the standard calibration curves fitting R~2(1.000 0±0.000 0, n=4) of USGS42, USGS43 and CBS combinations are the highest, and the coefficients(1.061 8±0.006 6, n=4) of them are the most stability than other combinations by utilizing linear regression of multiple-point normalization method. At the same time, two laboratories in Beijing and Shanghai were selected to carry out 35 repeated validations. The results show that the multiple-point normalization method of the standard combination has the highest fitting degree and good stability(R~2≥0.999 7, n=35). It is suitable for the normalization method of hair δ~2H and can be used as a recommended method for the construction of Chinese human hair δ~2H database. The idea of selecting isotopic reference materials and the normalization method of hydrogen isotopic compositions to isotope reference scales can also provide reference for the establishment of other stable isotope ratio database.
引文
[1] 郭波莉,魏益民,魏帅,孙倩倩,张磊,师振强.牦牛肉中稳定同位素指纹特征及影响因素[J].中国农业科学,2018,51(12):2 391-2 397.GUO Boli,WEI Yimin,WEI Shuai,SUN Qianqian,ZHANG Lei,SHI Zhenqiang.The characters and influence factors of stable isotope fingerprints in yak muscle[J].Scientia Agricultura Sinica,2018,51(12):2 391-2 397(in Chinese).
[2] 张蕊,赵钰,何红波,张旭东.基于稳定碳同位素技术研究大气CO2浓度升高对植物-土壤系统碳循环的影响[J].应用生态学报,2017,28(7):2 379-2 388.ZHANG Rui,ZHAO Yu,HE Hongbo,ZHANG Xudong.Investigation on effects of elevated atmospheric CO2 concentration on plant-soil system carbon cycling:based on stable isotopic technique[J].Chinese Journal of Applied Ecology,2017,28(7):2 379-2 388(in Chinese).
[3] 李平平,马倩倩,邹华耀,余新亚.团簇同位素的基本原理与地质应用[J].古地理学报,2017,19(4):713-728.LI Pingping,MA Qianqian,ZOU Huayao,YU Xinya.Basic principle of clumped isotopes and geological applications[J].Journal of Palaeogeography,2017,19(4):713-728(in Chinese).
[4] 梅宏成,朱军,权养科,王桂强.稳定同位素检验推断生物物证供体的生活时空信息[J].刑事技术,2016,41(2):87-92.MEI Hongcheng,ZHU Jun,QUAN Yangke,WANG Guiqiang.Inferring the Donor’s living spatial-temporal information by stable isotope analysis of the biological evidence[J].Forensic Science and Technology,2016,41(2):87-92(in Chinese).
[5] EHLERINGER J R,BOWEN G J,CHESSON L A,WEST A G,PODLESAK D W,CERLING T E.From the cover:hydrogen and oxygen isotope ratios in human hair are related to geography[J].Proceedings of the National Academy of Sciences of the United States of America,2008,105(8):2 788-2 793.
[6] PAUL D,SKRZYPEK G,FóRIZS I.Normalization of measured stable isotopic compositions to isotope reference scales-a review[J].Rapid Communications in Mass Spectrometry Rcm,2010,21(18):3 006-3 014.
[7] SKRZYPEK G.Normalization procedures and reference material selection in stable HCNOS isotope analyses:an overview[J].Analytical & Bioanalytical Chemistry,2013,405(9):2 815-2 823.
[8] BOWEN G J,CHESSON L,NIELSON K,CERLING T E,EHLERINGER J R.Treatment methods for the determination of δ2H and δ18O of hair keratin by continuous-flow isotope-ratio mass spectrometry[J].Rapid Communications in Mass Spectrometry,2010,19(17):2 371-2 378.
[9] COPLEN T B,QI H.USGS42 and USGS43:human-hair stable hydrogen and oxygen isotopic reference materials and analytical methods for forensic science and implications for published measurement results[J].Forensic Science International,2012,214(1):135-141.
[10] BOWEN G J,CHESSON L,NIELSON K,CERLING T E,EHLERINGER J R.Treatment methods for the determination of δ2H and δ18O of hair keratin by continuous-flow isotope-ratio mass spectrometry[J].Rapid Communications in Mass Spectrometry,2010,19(17):2 371-2 378.
[11] CARTER J F,FRY B.Ensuring the reliability of stable isotope ratio data-beyond the principle of identical treatment[J].Analytical & Bioanalytical Chemistry,2013,405(9):2 799-2 814.
[12] WERNER R A,BRAND W A.Referencing strategies and techniques in stable isotope ratio analysis[J].Rapid Communications in Mass Spectrometry,2010,15(7):501-519.
[13] ZANDEN H B V,REID A,KATZNER T,NELSON D M.Effect of heat and singeing on stable hydrogen isotope ratios of bird feathers and implications for their use in determining geographic origin[J].Rapid Communications in Mass Spectrometry,2018,32(21):1 859-1 866.
[14] COPLEN T B,QI H.A revision in hydrogen isotopic composition of USGS42 and USGS43 human-hair stable isotopic reference materials for forensic science[J].Forensic Science International,2016,266:222-225.
[15] SOTO D X,KOEHLER G,WASSENAAR L I,HOBSON K A.Re-evaluation of the hydrogen stable isotopic composition of keratin calibration standards for wildlife and forensic science applications[J].Rapid Communications in Mass Spectrometry Rcm,2017,31(14):1 193-1 203.
[16] OLSEN J,SEIERSTAD I,BO V,JOHNSEN S,HEINEMEIER J.Memory effect in deuterium analysis by continuous flow isotope ratio measurement[J].International Journal of Mass Spectrometry,2006,254(1):44-52.
[17] WASSENAAR L I,HOBSON K A.Two new keratin standards (δ2H,δ18O) for daily laboratory use in wildlife and forensic isotopic studies,poster[C].Fairbanks:Iso Ecol Ⅶ meeting,2010.
[2] 张蕊,赵钰,何红波,张旭东.基于稳定碳同位素技术研究大气CO2浓度升高对植物-土壤系统碳循环的影响[J].应用生态学报,2017,28(7):2 379-2 388.ZHANG Rui,ZHAO Yu,HE Hongbo,ZHANG Xudong.Investigation on effects of elevated atmospheric CO2 concentration on plant-soil system carbon cycling:based on stable isotopic technique[J].Chinese Journal of Applied Ecology,2017,28(7):2 379-2 388(in Chinese).
[3] 李平平,马倩倩,邹华耀,余新亚.团簇同位素的基本原理与地质应用[J].古地理学报,2017,19(4):713-728.LI Pingping,MA Qianqian,ZOU Huayao,YU Xinya.Basic principle of clumped isotopes and geological applications[J].Journal of Palaeogeography,2017,19(4):713-728(in Chinese).
[4] 梅宏成,朱军,权养科,王桂强.稳定同位素检验推断生物物证供体的生活时空信息[J].刑事技术,2016,41(2):87-92.MEI Hongcheng,ZHU Jun,QUAN Yangke,WANG Guiqiang.Inferring the Donor’s living spatial-temporal information by stable isotope analysis of the biological evidence[J].Forensic Science and Technology,2016,41(2):87-92(in Chinese).
[5] EHLERINGER J R,BOWEN G J,CHESSON L A,WEST A G,PODLESAK D W,CERLING T E.From the cover:hydrogen and oxygen isotope ratios in human hair are related to geography[J].Proceedings of the National Academy of Sciences of the United States of America,2008,105(8):2 788-2 793.
[6] PAUL D,SKRZYPEK G,FóRIZS I.Normalization of measured stable isotopic compositions to isotope reference scales-a review[J].Rapid Communications in Mass Spectrometry Rcm,2010,21(18):3 006-3 014.
[7] SKRZYPEK G.Normalization procedures and reference material selection in stable HCNOS isotope analyses:an overview[J].Analytical & Bioanalytical Chemistry,2013,405(9):2 815-2 823.
[8] BOWEN G J,CHESSON L,NIELSON K,CERLING T E,EHLERINGER J R.Treatment methods for the determination of δ2H and δ18O of hair keratin by continuous-flow isotope-ratio mass spectrometry[J].Rapid Communications in Mass Spectrometry,2010,19(17):2 371-2 378.
[9] COPLEN T B,QI H.USGS42 and USGS43:human-hair stable hydrogen and oxygen isotopic reference materials and analytical methods for forensic science and implications for published measurement results[J].Forensic Science International,2012,214(1):135-141.
[10] BOWEN G J,CHESSON L,NIELSON K,CERLING T E,EHLERINGER J R.Treatment methods for the determination of δ2H and δ18O of hair keratin by continuous-flow isotope-ratio mass spectrometry[J].Rapid Communications in Mass Spectrometry,2010,19(17):2 371-2 378.
[11] CARTER J F,FRY B.Ensuring the reliability of stable isotope ratio data-beyond the principle of identical treatment[J].Analytical & Bioanalytical Chemistry,2013,405(9):2 799-2 814.
[12] WERNER R A,BRAND W A.Referencing strategies and techniques in stable isotope ratio analysis[J].Rapid Communications in Mass Spectrometry,2010,15(7):501-519.
[13] ZANDEN H B V,REID A,KATZNER T,NELSON D M.Effect of heat and singeing on stable hydrogen isotope ratios of bird feathers and implications for their use in determining geographic origin[J].Rapid Communications in Mass Spectrometry,2018,32(21):1 859-1 866.
[14] COPLEN T B,QI H.A revision in hydrogen isotopic composition of USGS42 and USGS43 human-hair stable isotopic reference materials for forensic science[J].Forensic Science International,2016,266:222-225.
[15] SOTO D X,KOEHLER G,WASSENAAR L I,HOBSON K A.Re-evaluation of the hydrogen stable isotopic composition of keratin calibration standards for wildlife and forensic science applications[J].Rapid Communications in Mass Spectrometry Rcm,2017,31(14):1 193-1 203.
[16] OLSEN J,SEIERSTAD I,BO V,JOHNSEN S,HEINEMEIER J.Memory effect in deuterium analysis by continuous flow isotope ratio measurement[J].International Journal of Mass Spectrometry,2006,254(1):44-52.
[17] WASSENAAR L I,HOBSON K A.Two new keratin standards (δ2H,δ18O) for daily laboratory use in wildlife and forensic isotopic studies,poster[C].Fairbanks:Iso Ecol Ⅶ meeting,2010.
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