Ricci M P, Merritt D A, Freeman K H, Hayes J M
Department of Geological Sciences, Indiana University, Bloomington 47405, USA.
Org Geochem. 1994;21(6-7):561-71. doi: 10.1016/0146-6380(94)90002-7.
Methods are described for continuous monitoring of signals required for precise analyses of 13C, 18O, and 15N in gas streams containing varying quantities of CO2 and N2. The quantitative resolution (i.e. maximum performance in the absence of random errors) of these methods is adequate for determination of isotope ratios with an uncertainty of one part in 10(5); the precision actually obtained is often better than one part in 10(4). This report describes data-processing operations including definition of beginning and ending points of chromatographic peaks and quantitation of background levels, allowance for effects of chromatographic separation of isotopically substituted species, integration of signals related to specific masses, correction for effects of mass discrimination, recognition of drifts in mass spectrometer performance, and calculation of isotopic delta values. Characteristics of a system allowing off-line revision of parameters used in data reduction are described and an algorithm for identification of background levels in complex chromatograms is outlined. Effects of imperfect chromatographic resolution are demonstrated and discussed and an approach to deconvolution of signals from coeluting substances described.
本文描述了用于连续监测气流中13C、18O和15N精确分析所需信号的方法，该气流含有不同量的二氧化碳和氮气。这些方法的定量分辨率（即在无随机误差情况下的最大性能）足以测定同位素比率，其不确定度为十万分之一；实际获得的精度通常优于万分之一。本报告描述了数据处理操作，包括色谱峰起点和终点的定义、背景水平的定量、同位素取代物种色谱分离效应的考虑、与特定质量相关信号的积分、质量歧视效应的校正、质谱仪性能漂移的识别以及同位素δ值的计算。描述了一种允许离线修订数据处理中使用参数的系统的特性，并概述了一种识别复杂色谱图中背景水平的算法。展示并讨论了不完美色谱分辨率的影响，并描述了一种从共洗脱物质中解卷积信号的方法。
