进样量和信号强度对气相色谱-燃烧-同位素比值质谱测定δ^(13)C和δ^(15)N的影响  

Effect of Sample Size and Signal Intensity onδ^(13)C andδ^(15)N Measurements by GC-C-IRMS

作　　者：杜屹原 孟宪菁 杨斌 宋亮[1,4] 朱光旭[5] 周晓 张嫒萍 潘洁 江琳琳 DU Yi-yuan;MENG Xian-jing;YANG Bin;SONG Liang;ZHU Guang-xu;ZHOU Xiao;ZHANG Ai-ping;PAN Jie;JIANG Lin-lin(CAS Key Laboratory of Tropical Forest Ecology,Xishuangbanna Tropical Botanical Garden,Chinese Academy of Sciences,Menglun 666303,China;University of Chinese Academy of Sciences,Beijing 100049,China;Thermo Fisher Scientific,Shanghai 201206,China;Core Botanical Gardens,Chinese Academy of Sciences,Menglun 666303,China;College of Biotechnology and Environmental Engineering,Guiyang University,Guiyang 550005,China;Puer University,Puer 665000,China;Shenyang Agricultural University,Shenyang 110866,China)

机构地区：[1]中国科学院西双版纳热带植物园热带森林生态学重点实验室,云南勐仑666303 [2]中国科学院大学,北京100049 [3]赛默飞世尔科技(中国)有限公司,上海201206 [4]中国科学院核心植物园,云南勐仑666303 [5]贵阳学院生物与环境工程学院,贵州贵阳550005 [6]普洱学院,云南普洱665000 [7]沈阳农业大学,辽宁沈阳110866

出　　处：《质谱学报》2022年第4期512-521,I0006,共11页Journal of Chinese Mass Spectrometry Society

基　　金：国家自然科学基金(32171557,32171529,41803018);中国科学院“青年创新促进会”(2021397)项目。

摘　　要：采用气相色谱-燃烧-同位素比值质谱(GC-C-IRMS)法对咖啡因化合物和混合体系中特定氨基酸的δ^(13)C和δ^(15)N进行测定,在保证高测定精度和准确度的前提下,探讨GC-C-IRMS对进样量和信号强度变化的响应特征。分析结果表明,当C质量≥1 ng或m/z 44信号≥100 mV时,以及N质量≥5 ng或m/z 28信号≥100 mV时,咖啡因δ^(13)C和δ^(15)N测定结果的精度(<0.3‰)和准确度(<0.2‰)均能够满足实验室测试要求。针对混合体系中氨基酸δ^(13)C和δ^(15)N的测定,GC-C-IRMS可以在极少的进样量下实现对特定氨基酸色谱峰的有效分离。12种氨基酸δ^(13)C测定结果未表现出对m/z 44信号强度的依赖性(斜率接近0),其δ^(13)C平均测定精度为0.56‰;而δ^(15)N测定结果表现出良好的时间稳定性(4天),与元素分析-稳定同位素比值质谱(EA-IRMS)单独测定结果的平均偏差为0.77‰。Theδ^(13)C andδ^(15)N of specific compounds can be determined successfully by gas chromatography-combustion-isotope ratio mass spectrometer(GC-C-IRMS).Precision and accuracy of the measurement processes are two key indicators for evaluating the performance of GC-C-IRMS,which are also of great significance for defining the detection ability of GC-C-IRMS.However,the uncertainty of the detection capability of GC-C-IRMS limits the application of isotopic tracing technology for specific compounds.Therefore,there is an urgent need to comprehensively evaluate the effects of sample size and signal intensity on theδ^(13)C andδ^(15)N measurements by GC-C-IRMS.In this study,δ^(13)C andδ^(15)N of caffeine compounds and specific amino acids were analyzed under the premise of ensuring high determination precision and accuracy based on GC-C-IRMS.The results showed that GC-C-IRMS had good accuracy in determination ofδ^(13)C andδ^(15)N under the condition of extremely small sample size and extremely low signal intensity.Specifically,the carbon and nitrogen isotope compositions of caffeine could be determined successful when m/z 44 and m/z 28 signals were higher than 100 mV.The recommended sample size of GC-C-IRMS should be more than 1 ng C and 5 ng N for caffeineδ^(13)C andδ^(15)N measurements,respectively.The measurement precision and accuracy were better than 0.3‰and 0.2‰for both caffeineδ^(13)C andδ^(15)N,which could meet the practical demands in the laboratory.Meanwhile,GC-C-IRMS could ensure sufficient m/z 44 and m/z 28 signals for amino acids,and avoid peak-to-peak interference during the determination of amino acidsδ^(13)C andδ^(15)N in the mixed systems.For theδ^(13)C andδ^(15)N measurements of amino acids in a complex compound,the chromatographic peaks acquired by GC-C-IRMS were well separated and presented under minimal injection amounts.Theδ^(13)C measured values of 12 specific amino acids ranged from-29.56%to-6.89‰with a mean measurement accuracy of 0.56‰.For theδ^(15)N of specific amino acid

关 键 词：同位素比值质谱(IRMS) 咖啡因 氨基酸 进样量 信号强度 

分 类 号：O657.63[理学—分析化学]