On-line measurements ofδ15N in biological fluids by a modified continuous-flow elemental analyzer with an isotope-ratio mass spectrometer
会议名称：《中国科学院地质与地球物理研究所2008学术年会》
会议日期：2009年
学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学]
基 金：supported by the National Natural Science Foundation of China(Grant No.40502019)
摘 要：A modified continuous-flow elemental analyzer coupled to an isotope-ratio mass spectrometer (modified EA-IRMS) was tested for on-lineδN measurement on urea solution and biological fluids (***).The elemental analyzer configuration was adapted by adding a U-shaped cold trap and an X-pattem four-way valve for on-line trapping/venting of water from the liquid *** indicate that theδN ratios show little variation(standard deviation(SD) = 0.05‰) with a sample size above the equivalent N yield of 0.2 mg urea(0.092 mg N) when the mass spectrometer conditions were carefully *** contrast,a significant logarithmic decrease inδN with sample size was observed but this can be offset by applying a linearity correction or blank correction when the sample size is between equivalent N yields of 0.05 and 0.2 mg *** blank correctedδN ratios give an overall precision of .16‰whereas the average precision forδN corrected using combined linearity and shift correction is 0.05‰.The relatively large variation in blank correctedδN values may be attributed to the variability of the blankδN in the ***,the blank correction should be carefully performed in routine *** a result,the linearity range of a modified EA-IRMS can be extended to a minimum sample size of 0.023 mg *** addition, the reproducibility of the new system is good,as indicated by the precision(0.2‰) for a set of standards and *** data show that fluids containing nitrogen can be successfully analyzed in the modified EA-IRMS.