An online method using continuous flow isotope ratio mass spectrometry （CF-IRMS） interfaced with a Gasbench Ⅱ was presented to determine chlorine stable isotope composition. Silver chloride （AgCl） was quantitativ...An online method using continuous flow isotope ratio mass spectrometry （CF-IRMS） interfaced with a Gasbench Ⅱ was presented to determine chlorine stable isotope composition. Silver chloride （AgCl） was quantitatively derived from chloride by using silver nitrate （AgNO3）, and then was reacted with iodomethane （CH3Ⅰ） to produce methyl chloride （CH3Cl）. A GasBench Ⅱ equipped with a PoraPlot Q column was used to separate CH3Cl from any other gas species. Finally, chlorine stable isotope analysis was carried out on CH3Cl introduced to the IRMS in a helium stream via an active open split. The minimum amount of Cl used in this method is of the order of 1.4 μmol. Inter-laboratory and inter-technique comparisons show that the total uncertainty incorporating both the precision and accuracy of this method is better than 0.007%. Furthermore, ten seawaters sampled from different locations have a narrow δ37Cl value range from -0.008% to 0.010%, with a mean value of （0.000±0.006）%. This supports the assumption that any seawater can be representative of standard mean ocean chloride （SMOC） and used as an international reference material.展开更多
An accurate and sensitive method for the simultaneous determination of gibberellic acid（GA3）, gibberellin A4（GA4） and gibberellin A7（GA7） residues in tomato paste was developed by coupling solid phase extraction...An accurate and sensitive method for the simultaneous determination of gibberellic acid（GA3）, gibberellin A4（GA4） and gibberellin A7（GA7） residues in tomato paste was developed by coupling solid phase extraction to high performance liquid chromatography-tandem mass spectrometry（LC-MS/MS） with electrospray ionization based stable isotope dilution analysis（SIDA）. The isotope labeled internal standard can compensate for the losses during the extraction and cleanup steps and for discrimination due to ion suppression. After extraction from methanol, hydrophile lipophilic balance（HLB） solid phase extraction（SPE） column was tested for the capacity of the cleanup of the tomato paste in compared with C18 SPE column which is the common way to the detection of GAs, and the former gained better result. Spiked experiments were performed in the non-contaminated tomato pastes and the recoveries of GA3, GA4 and GA7 were 42.6%―75.0% in external standard method（ESM） and 91.1%―103.8% in internal standard method（ISM） respectively. The validities of this method were investigated and good analytical performance for the three GAs was obtained, including low limits of method detection（2 ng/g for GA3 and GA4, 0.3 ng/g for GA7）, excellent linear dynamic ranges（5―500 ng/g for GA3 and GA4, 1―100 ng/g for GA7） and good relative standard deviation ranges（4.8%―9.4% for the intra-day test and 3.5%―11.9% for the inter-day test）.展开更多
该研究建立了一种精准测定不同样品中氨基酸含量及其氮同位素组成的方法。首先利用N-新戊酰基-O-异丙酯(NPP)对氨基酸进行衍生化,使其更适用于气相色谱分析。随后,采用气相色谱-质谱(GCMS)对大豆、土壤以及标准样品中的15种氨基酸单体...该研究建立了一种精准测定不同样品中氨基酸含量及其氮同位素组成的方法。首先利用N-新戊酰基-O-异丙酯(NPP)对氨基酸进行衍生化,使其更适用于气相色谱分析。随后,采用气相色谱-质谱(GCMS)对大豆、土壤以及标准样品中的15种氨基酸单体进行定量分析,所有目标氨基酸均获得良好的分离效果,且在1.0~16.0μmol/L浓度范围内呈线性关系(r^(2)>0.98)。此外,利用气相色谱-燃烧-同位素比值质谱(GC-C-IRMS)对上述样品中氨基酸的氮同位素组成(δ~(15)N)进行了测定。结果表明,当进样量超过20 ng N([N_(2)^(+)]m/z 28信号强度约为150 mV)时,该方法可以获得稳定可靠的δ^(15)N值,平均精度可达0.36‰。通过与元素分析-同位素比值质谱(EA-IRMS)的结果进行比较,两种方法的测定结果高度一致(r^(2)=0.9954),表明NPP衍生化过程未引入明显的氮同位素分馏。最终测得大豆和土壤样品中各氨基酸的δ~(15)N值分别分布在10.90‰~22.32‰和-1.92‰~12.82‰之间,标准偏差分别为0.23‰~0.88‰和0.08‰~0.79‰,符合样品分析的精度要求。展开更多
New ionization and detection techniques in mass spectrometry have been successfully applied for efficient analyses of complex biological systems. It is, however, still difficult to trace structural changes of a specif...New ionization and detection techniques in mass spectrometry have been successfully applied for efficient analyses of complex biological systems. It is, however, still difficult to trace structural changes of a specific molecular species in such systems. In the present study, a molecular probe strategy in combination with tandem electrospray ionization mass spectrometry has been examined using synthetic deuterium-labeled phosphatidylcholine hydroperoxide (PC-OOH/D3) and ethyl-labeled phosphatidylcholine having docosahexaenoic acid side chain (DHA-PC/Et). Administration of a mixture of PC-OOH/D3 and DHA-PC/Et to human blood and human skin surface, followed by extraction and analysis with collision-induced tandem electrospray ionization mass spectrometry demonstrated that metabolites of both molecular probes can be detected simultaneously with strict selectivity. The present method is also found to be useful in tracing chemical changes of the unstable docosahexaenoyl group on the surface of processed fish. The activity of phospholipase A2 can also be assessed using a phospholipid molecular probe with a linoleoyl and a deuteriomethyl group via selective detection of the lyso-phospholipid product by mass spectrometry. The advantage of the present method is that no chromatographic separation is required and analysis can be performed under strictly the same condition for different molecular probes, affording multiple data by one experiment. The present strategy may be useful for tracing time-dependent phenomena in dynamic phospholipid biochemistry, and can be widely used for any biological and food systems.展开更多
该文建立液相色谱-稳定同位素比值质谱联用(liquid chromatography-stable isotope ratio mass spectrometry,LC-IRMS)检测抗坏血酸δ^(13)C值的分析方法,用于鉴别针叶樱桃粉中抗坏血酸天然来源的真实性。样品中抗坏血酸经液相色谱在线...该文建立液相色谱-稳定同位素比值质谱联用(liquid chromatography-stable isotope ratio mass spectrometry,LC-IRMS)检测抗坏血酸δ^(13)C值的分析方法,用于鉴别针叶樱桃粉中抗坏血酸天然来源的真实性。样品中抗坏血酸经液相色谱在线分离纯化,优化后色谱条件为:Syncronis C18(250 mm×4.6 mm,5μm)色谱柱,流动相为水-pH 2的硫酸溶液(90∶10,体积比),流速0.250 mL/min,色谱柱温度30℃,进样量10μL,通过LC-IsoLink实现目标物全部氧化为CO_(2)气体,最终以气态形式进入稳定同位素质谱仪,直接检测样品中抗坏血酸的δ^(13)C,该方法结果稳定、准确。分别测定了7个合成来源的维生素C片和19个针叶樱桃粉,结果表明,天然来源抗坏血酸δ^(13)C值为-25.00‰~-22.01‰,合成来源抗坏血酸δ^(13)C值为-11.74‰~-10.28‰,两者分布显著性差异,该方法可用于抗坏血酸产品标识的真实性鉴别研究。展开更多
基金Projects(40772156, 41072179) supported by the National Natural Science Foundation of China
文摘An online method using continuous flow isotope ratio mass spectrometry （CF-IRMS） interfaced with a Gasbench Ⅱ was presented to determine chlorine stable isotope composition. Silver chloride （AgCl） was quantitatively derived from chloride by using silver nitrate （AgNO3）, and then was reacted with iodomethane （CH3Ⅰ） to produce methyl chloride （CH3Cl）. A GasBench Ⅱ equipped with a PoraPlot Q column was used to separate CH3Cl from any other gas species. Finally, chlorine stable isotope analysis was carried out on CH3Cl introduced to the IRMS in a helium stream via an active open split. The minimum amount of Cl used in this method is of the order of 1.4 μmol. Inter-laboratory and inter-technique comparisons show that the total uncertainty incorporating both the precision and accuracy of this method is better than 0.007%. Furthermore, ten seawaters sampled from different locations have a narrow δ37Cl value range from -0.008% to 0.010%, with a mean value of （0.000±0.006）%. This supports the assumption that any seawater can be representative of standard mean ocean chloride （SMOC） and used as an international reference material.
基金Supported by the Project of Chinese Academy of Inspection and Quanrantine(No.2010JK001)the Project of Xinjiang Entry-exit Inspection and Quarantine Bureau, China(No.2010XK0033)
文摘An accurate and sensitive method for the simultaneous determination of gibberellic acid（GA3）, gibberellin A4（GA4） and gibberellin A7（GA7） residues in tomato paste was developed by coupling solid phase extraction to high performance liquid chromatography-tandem mass spectrometry（LC-MS/MS） with electrospray ionization based stable isotope dilution analysis（SIDA）. The isotope labeled internal standard can compensate for the losses during the extraction and cleanup steps and for discrimination due to ion suppression. After extraction from methanol, hydrophile lipophilic balance（HLB） solid phase extraction（SPE） column was tested for the capacity of the cleanup of the tomato paste in compared with C18 SPE column which is the common way to the detection of GAs, and the former gained better result. Spiked experiments were performed in the non-contaminated tomato pastes and the recoveries of GA3, GA4 and GA7 were 42.6%―75.0% in external standard method（ESM） and 91.1%―103.8% in internal standard method（ISM） respectively. The validities of this method were investigated and good analytical performance for the three GAs was obtained, including low limits of method detection（2 ng/g for GA3 and GA4, 0.3 ng/g for GA7）, excellent linear dynamic ranges（5―500 ng/g for GA3 and GA4, 1―100 ng/g for GA7） and good relative standard deviation ranges（4.8%―9.4% for the intra-day test and 3.5%―11.9% for the inter-day test）.
文摘该研究建立了一种精准测定不同样品中氨基酸含量及其氮同位素组成的方法。首先利用N-新戊酰基-O-异丙酯(NPP)对氨基酸进行衍生化,使其更适用于气相色谱分析。随后,采用气相色谱-质谱(GCMS)对大豆、土壤以及标准样品中的15种氨基酸单体进行定量分析,所有目标氨基酸均获得良好的分离效果,且在1.0~16.0μmol/L浓度范围内呈线性关系(r^(2)>0.98)。此外,利用气相色谱-燃烧-同位素比值质谱(GC-C-IRMS)对上述样品中氨基酸的氮同位素组成(δ~(15)N)进行了测定。结果表明,当进样量超过20 ng N([N_(2)^(+)]m/z 28信号强度约为150 mV)时,该方法可以获得稳定可靠的δ^(15)N值,平均精度可达0.36‰。通过与元素分析-同位素比值质谱(EA-IRMS)的结果进行比较,两种方法的测定结果高度一致(r^(2)=0.9954),表明NPP衍生化过程未引入明显的氮同位素分馏。最终测得大豆和土壤样品中各氨基酸的δ~(15)N值分别分布在10.90‰~22.32‰和-1.92‰~12.82‰之间,标准偏差分别为0.23‰~0.88‰和0.08‰~0.79‰,符合样品分析的精度要求。
文摘New ionization and detection techniques in mass spectrometry have been successfully applied for efficient analyses of complex biological systems. It is, however, still difficult to trace structural changes of a specific molecular species in such systems. In the present study, a molecular probe strategy in combination with tandem electrospray ionization mass spectrometry has been examined using synthetic deuterium-labeled phosphatidylcholine hydroperoxide (PC-OOH/D3) and ethyl-labeled phosphatidylcholine having docosahexaenoic acid side chain (DHA-PC/Et). Administration of a mixture of PC-OOH/D3 and DHA-PC/Et to human blood and human skin surface, followed by extraction and analysis with collision-induced tandem electrospray ionization mass spectrometry demonstrated that metabolites of both molecular probes can be detected simultaneously with strict selectivity. The present method is also found to be useful in tracing chemical changes of the unstable docosahexaenoyl group on the surface of processed fish. The activity of phospholipase A2 can also be assessed using a phospholipid molecular probe with a linoleoyl and a deuteriomethyl group via selective detection of the lyso-phospholipid product by mass spectrometry. The advantage of the present method is that no chromatographic separation is required and analysis can be performed under strictly the same condition for different molecular probes, affording multiple data by one experiment. The present strategy may be useful for tracing time-dependent phenomena in dynamic phospholipid biochemistry, and can be widely used for any biological and food systems.
