The accurate measurement of concentration is the basis for determining emission sources and sinks of nitrous oxide （N2O）. The detection of N2O showed that the presence of carbon dioxide （CO2） biased the N2O respon...The accurate measurement of concentration is the basis for determining emission sources and sinks of nitrous oxide （N2O）. The detection of N2O showed that the presence of carbon dioxide （CO2） biased the N2O response when pure nitrogen （N2） was used as a carrier gas for gas chromatography （GC） equipped with an electron capture detector （GC-ECD）. In this study, laboratory experiments were carried out to explore how the presence of CO2 interferes with the accurate determination of N2O. The aims were to address the extent of the influence to try and explain the underlying mechanism, and to uncover technical options for solving the problem. Three GC carrier gases are discussed： pure nitrogen （DN）; a mixture of argon and methane （AM）; and a high concentration CO2, which was introduced into the ECD cell with a low flow rate based on DN （DN-CO2）. The results show that when DN was used, the existence of CO2 in the ECD cell greatly enhanced the response of N2O, which increased with CO2 content and remained constant when the content reached a limit. Comparisons between the three methods show that the DN method is defective for the accurate determination of N2O. The bias is caused by different electron capture mechanisms of CO2 and N2O and depends heavily on the detector temperature. New GC carrier gas types with make-up gases that can remove the CO2-induced influence, such as the DN-CO2 and DN-CH4 methods reported in this paper, are recommended for the accurate measurement of N2O.展开更多
为了有效监测环境水体中的有机氯农药(OCPs)残留,本研究开发了一种低消耗、弱基质效应、经济便捷的固相微萃取技术测定水中13种OCPs残留的方法。应用具有强选择性的硅橡胶(SR)薄膜为固相吸附材料,制备了简便易操作的固相萃取瓶,通过优...为了有效监测环境水体中的有机氯农药(OCPs)残留,本研究开发了一种低消耗、弱基质效应、经济便捷的固相微萃取技术测定水中13种OCPs残留的方法。应用具有强选择性的硅橡胶(SR)薄膜为固相吸附材料,制备了简便易操作的固相萃取瓶,通过优化萃取方式、萃取时间、洗脱溶剂以及洗脱方式等条件,选择涡旋10 min进行SR薄膜对目标物的萃取,利用5 mL V_(正己烷):V_(乙酸乙酯)=1:1溶液洗脱SR薄膜上目标物,采用气相色谱仪进行检测。结果表明:方法检出限在0.001~0.132μg/L之间,定量限为0.2μg/L;决定系数(R^(2))>0.9973;在0.2、1、20μg/L 3个添加水平下,13种农药在水中OCPs的平均回收率在73%~109%之间,相对标准偏差在0.5%~13%之间(n=5)。利用该方法对巢湖、南淝河等合肥市内主要河流进行了13种OCPs残留的检测,结果发现13种OCPs的最高检出质量浓度为3.64μg/L。与已所报道的方法相比,该方法具有灵敏度高、操作简便、成本低等特点,在环境水体OCPs多残留痕量监测领域具有良好的应用前景。展开更多
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-204)the National Basic Research Program of China (No.2007CB407303)
文摘The accurate measurement of concentration is the basis for determining emission sources and sinks of nitrous oxide （N2O）. The detection of N2O showed that the presence of carbon dioxide （CO2） biased the N2O response when pure nitrogen （N2） was used as a carrier gas for gas chromatography （GC） equipped with an electron capture detector （GC-ECD）. In this study, laboratory experiments were carried out to explore how the presence of CO2 interferes with the accurate determination of N2O. The aims were to address the extent of the influence to try and explain the underlying mechanism, and to uncover technical options for solving the problem. Three GC carrier gases are discussed： pure nitrogen （DN）; a mixture of argon and methane （AM）; and a high concentration CO2, which was introduced into the ECD cell with a low flow rate based on DN （DN-CO2）. The results show that when DN was used, the existence of CO2 in the ECD cell greatly enhanced the response of N2O, which increased with CO2 content and remained constant when the content reached a limit. Comparisons between the three methods show that the DN method is defective for the accurate determination of N2O. The bias is caused by different electron capture mechanisms of CO2 and N2O and depends heavily on the detector temperature. New GC carrier gas types with make-up gases that can remove the CO2-induced influence, such as the DN-CO2 and DN-CH4 methods reported in this paper, are recommended for the accurate measurement of N2O.
文摘为了有效监测环境水体中的有机氯农药(OCPs)残留,本研究开发了一种低消耗、弱基质效应、经济便捷的固相微萃取技术测定水中13种OCPs残留的方法。应用具有强选择性的硅橡胶(SR)薄膜为固相吸附材料,制备了简便易操作的固相萃取瓶,通过优化萃取方式、萃取时间、洗脱溶剂以及洗脱方式等条件,选择涡旋10 min进行SR薄膜对目标物的萃取,利用5 mL V_(正己烷):V_(乙酸乙酯)=1:1溶液洗脱SR薄膜上目标物,采用气相色谱仪进行检测。结果表明:方法检出限在0.001~0.132μg/L之间,定量限为0.2μg/L;决定系数(R^(2))>0.9973;在0.2、1、20μg/L 3个添加水平下,13种农药在水中OCPs的平均回收率在73%~109%之间,相对标准偏差在0.5%~13%之间(n=5)。利用该方法对巢湖、南淝河等合肥市内主要河流进行了13种OCPs残留的检测,结果发现13种OCPs的最高检出质量浓度为3.64μg/L。与已所报道的方法相比,该方法具有灵敏度高、操作简便、成本低等特点,在环境水体OCPs多残留痕量监测领域具有良好的应用前景。
