采用质子传递反应-飞行时间质谱仪(Proton Transfer Reaction-Time of Flight-Mass Spectrometry,PTR-TOFMS)与气相色谱-质谱联用技术(Gas Chromatography-Mass Spectrometer,GC-MS)对不同品种武夷岩茶(水仙、肉桂)香气成分进行分析,结...采用质子传递反应-飞行时间质谱仪(Proton Transfer Reaction-Time of Flight-Mass Spectrometry,PTR-TOFMS)与气相色谱-质谱联用技术(Gas Chromatography-Mass Spectrometer,GC-MS)对不同品种武夷岩茶(水仙、肉桂)香气成分进行分析,结果表明:武夷水仙以反式橙花叔醇、(E,E)-2,4-庚二烯醛、芳樟醇及其氧化物等为主;武夷肉桂是反式橙花叔醇、α-法尼烯、苯甲醛为主,且在武夷山肉桂中存在高浓度的m/z 207、223、281、291几个未知化合物。2种分析技术所检测到的香气成分和相对含量比例差异显著,两者各有优劣,相互补充,联合分析更加完整,更有利于准确地进行香气分析,同时发现PTR-TOF-MS法更能真实地反映茶叶香气的完整信息。展开更多
Green leaf volatiles（GLVs） emitted by plants after stress or damage induction are a major part of biogenic volatile organic compounds（BVOCs）. Proton transfer reaction time-of-flight mass spectrometry（PTR-TOF-MS）...Green leaf volatiles（GLVs） emitted by plants after stress or damage induction are a major part of biogenic volatile organic compounds（BVOCs）. Proton transfer reaction time-of-flight mass spectrometry（PTR-TOF-MS） is a high-resolution and sensitive technique for in situ GLV analyses, while its performance is dramatically influenced by humidity, electric field,etc. In this study the influence of gas humidity and the effect of reduced field（E/N） were examined in addition to measuring calibration curves for the GLVs. Calibration curves measured for seven of the GLVs in dry air were linear, with sensitivities ranging from 5 to10 ncps/ppbv（normalized counts per second/parts per billion by volume）. The sensitivities for most GLV analyses were found to increase by between 20% and 35% when the humidity of the sample gas was raised from 0% to 70% relative humidity（RH） at 21°C, with the exception of（E）-2-hexenol. Product ion branching ratios were also affected by humidity,with the relative abundance of the protonated molecular ions and higher mass fragment ions increasing with humidity. The effect of reduced field（E/N） on the fragmentation of GLVs was examined in the drift tube of the PTR-TOF-MS. The structurally similar GLVs are acutely susceptible to fragmentation following ionization and the fragmentation patterns are highly dependent on E/N. Overall the measured fragmentation patterns contain sufficient information to permit at least partial separation and identification of the isomeric GLVs by looking at differences in their fragmentation patterns at high and low E/N.展开更多
Organic acids are important contributors to the acidity of atmospheric precipitation,but their existence in the Chinese atmosphere is largely unclear.In this study,twelve atmospheric gaseous organic acids,including C_...Organic acids are important contributors to the acidity of atmospheric precipitation,but their existence in the Chinese atmosphere is largely unclear.In this study,twelve atmospheric gaseous organic acids,including C_(1)-C_(9) alkanoic acids,methacrylic acid,pyruvic acid,and benzoic acid,were observed in the suburb of Wangdu,Hebei Province,a typical rural site in the northern China plain from 16^(th) December,2018 to 22^(nd) January,2019,using a Vocus■ Proton-Transfer-Reaction time-of-flight mass spectrometer(Vocus PTR-ToF).The quantification of C_(2)-C_(4) alkanoic acids by the Vocus PTR-ToF was calibrated according to the titration of a NaOH solution by C_(2)-C_(4) alkanoic acids from home-made permeation sources,and the other organic acids except for formic acid were quantified based on the k_(cap)-sensitivity linearity in the Vocus PTR-ToF,whereas formic acid was not quantified because our instrument setting led to a significant underestimation in its concentration.The average total concentration of eleven gaseous organic acids was 6.96±5.20 ppbv(parts per billion by volume).The average concentration of acetic acid was the highest(3.86±3.00 ppbv),followed by propanoic acid,butyric acid,and methacrylic acid.Domestic straw burning was likely the dominant source of the observed gaseous organic acids according to the good correlations between acetonitrile and organic acids and between particulate K+and organic acids,and traffic emissions could also have contributed.During episodes with continuously high concentrations of organic acids,short-distance transport dominated in Wangdu according to the backward trajectory analysis.Baoding,Shijiazhuang,and Hengshui areas were the main source areas based on potential source contribution function and concentration weighing track analysis.展开更多
文摘采用质子传递反应-飞行时间质谱仪(Proton Transfer Reaction-Time of Flight-Mass Spectrometry,PTR-TOFMS)与气相色谱-质谱联用技术(Gas Chromatography-Mass Spectrometer,GC-MS)对不同品种武夷岩茶(水仙、肉桂)香气成分进行分析,结果表明:武夷水仙以反式橙花叔醇、(E,E)-2,4-庚二烯醛、芳樟醇及其氧化物等为主;武夷肉桂是反式橙花叔醇、α-法尼烯、苯甲醛为主,且在武夷山肉桂中存在高浓度的m/z 207、223、281、291几个未知化合物。2种分析技术所检测到的香气成分和相对含量比例差异显著,两者各有优劣,相互补充,联合分析更加完整,更有利于准确地进行香气分析,同时发现PTR-TOF-MS法更能真实地反映茶叶香气的完整信息。
基金supported by the Chinese National Natural Science Foundation (41175110)the funding for the Distinguished Professor of Jiangsu Province
文摘Green leaf volatiles（GLVs） emitted by plants after stress or damage induction are a major part of biogenic volatile organic compounds（BVOCs）. Proton transfer reaction time-of-flight mass spectrometry（PTR-TOF-MS） is a high-resolution and sensitive technique for in situ GLV analyses, while its performance is dramatically influenced by humidity, electric field,etc. In this study the influence of gas humidity and the effect of reduced field（E/N） were examined in addition to measuring calibration curves for the GLVs. Calibration curves measured for seven of the GLVs in dry air were linear, with sensitivities ranging from 5 to10 ncps/ppbv（normalized counts per second/parts per billion by volume）. The sensitivities for most GLV analyses were found to increase by between 20% and 35% when the humidity of the sample gas was raised from 0% to 70% relative humidity（RH） at 21°C, with the exception of（E）-2-hexenol. Product ion branching ratios were also affected by humidity,with the relative abundance of the protonated molecular ions and higher mass fragment ions increasing with humidity. The effect of reduced field（E/N） on the fragmentation of GLVs was examined in the drift tube of the PTR-TOF-MS. The structurally similar GLVs are acutely susceptible to fragmentation following ionization and the fragmentation patterns are highly dependent on E/N. Overall the measured fragmentation patterns contain sufficient information to permit at least partial separation and identification of the isomeric GLVs by looking at differences in their fragmentation patterns at high and low E/N.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21925601,91644213)the National Key R&D Program of China(No.2017YFC0209505).
文摘Organic acids are important contributors to the acidity of atmospheric precipitation,but their existence in the Chinese atmosphere is largely unclear.In this study,twelve atmospheric gaseous organic acids,including C_(1)-C_(9) alkanoic acids,methacrylic acid,pyruvic acid,and benzoic acid,were observed in the suburb of Wangdu,Hebei Province,a typical rural site in the northern China plain from 16^(th) December,2018 to 22^(nd) January,2019,using a Vocus■ Proton-Transfer-Reaction time-of-flight mass spectrometer(Vocus PTR-ToF).The quantification of C_(2)-C_(4) alkanoic acids by the Vocus PTR-ToF was calibrated according to the titration of a NaOH solution by C_(2)-C_(4) alkanoic acids from home-made permeation sources,and the other organic acids except for formic acid were quantified based on the k_(cap)-sensitivity linearity in the Vocus PTR-ToF,whereas formic acid was not quantified because our instrument setting led to a significant underestimation in its concentration.The average total concentration of eleven gaseous organic acids was 6.96±5.20 ppbv(parts per billion by volume).The average concentration of acetic acid was the highest(3.86±3.00 ppbv),followed by propanoic acid,butyric acid,and methacrylic acid.Domestic straw burning was likely the dominant source of the observed gaseous organic acids according to the good correlations between acetonitrile and organic acids and between particulate K+and organic acids,and traffic emissions could also have contributed.During episodes with continuously high concentrations of organic acids,short-distance transport dominated in Wangdu according to the backward trajectory analysis.Baoding,Shijiazhuang,and Hengshui areas were the main source areas based on potential source contribution function and concentration weighing track analysis.
