On-line monitoring of biotechnological processes by gas chromatographic-mass spectrometric analysis of fermentation suspensions

An on-line monitoring system has been developed for the control of a biorreactor for the anaerobic pretreatment of an industrial waste water. The monitoring system is based on a process mass spectrometer with a temperature controlled membrane inlet. The membrane introduction mass spectrometer (MIMS) is coupled with a resistively heated metal gas chromatography capillary column, which serves as a transfer line between the bioreactor and the MIMS. Sampling and injection is performed by means of a pneumatically driven membrane probe, which enables monitoring of soluted and gaseous substances in the fermentation broth. The system can also be coupled to other processes.     

Applications of evolved gas analysis Part 2: EGA by mass spectrometry

The analytical applications of the evolved gas analysis (EGA) performed by mass spectrometry, for the period extending from 2001 to 2004, are collected in this review. By this technique, the nature of volatile products released by a substance subjected to a controlled temperature program is on-line determined, with the possibility to prove a supposed reaction, either under isothermal or under heating conditions.     

On-line analysis of polymer melt processes

Molten polymer process streams are difficult to analyze either in- or on-line because of sampling problems due to the high temperature and viscosity of the molten state. Real-time monitoring of chemical compositions in these processes can significantly improve safety and product quality and minimize process costs and waste. The information content of the mid-infrared spectrum combined with the recent development of rugged process Fourier transform (FT) IR spectrometers is stimulating the application of process FT-IR to industrial polymer melt processes. Sampling considerations for polymer melts are reviewed. Also, the use of FT-IR spectrometry for on-line measurements of the polymer composition for polymer blends and copolymers in the melt, and the question of how this information could be used to monitor and control the quality of the product given by the process are discussed.     

溶剂转移-气相色谱-质谱法和选择洗脱-气相色谱法测定大蒜中289种农药多残留

以溶剂转移净化为核心步骤,建立了一种适用于大蒜样品中农药多残留分析的前处理方法(方法I),配以一个辅助方法(方法II),构成大蒜中常见289种农药多残留的分析体系(方法I283种,方法II6种)。方法I中,样品用乙腈-水溶液提取,盐析分配,溶剂转移和固相萃取(SPE)净化后进行气相色谱-质谱(GC-MS)分析;方法II中,样品用无水Na2SO4配合乙酸乙酯均质研磨,超声波辅助提取,提取液经Primary Secondary Amine (PSA)粉末分散固相萃取和LC-Si柱选择洗脱净化后进行GC分析。GC-MS采用选择离子监测(SIM)方式,GC采用火焰光度检测器(FPD)检测,外标法定量。方法简便、快速,通过优化前处理和上机条件,在最优条件下进行测试,方法的定量限(S/N≥10)为0.01～0.05 mg/kg。方法I中,在加标水平为0.02、0.20 mg/kg时,回收率为52%～163%,其中回收率在70%～120%之间的占88%,相对标准偏差为2.4%～18%;方法II中,在加标水平为0.01、0.02、0.10、0.20 mg/kg时,回收率为70%～111%,相对标准偏差为3.2%～9.3%。详细描述了实验模型的构建,并对GC-MS灵敏度的提高提出了新的见解。该方法准确、灵敏、快速,可满足大蒜中多种农药残留的检测要求。     

Quantitative analysis of phthalates using a pyrolyzer gas chromatography/mass spectrometry method

A pyrolyzer gas chromatography/mass spectrometry (GC/MS) method eliminates toxic solvents that burden our environment and can address the crucial problem of the solvent extraction GC/MS method. The purpose of this study is to establish an efficient quantitative analysis method for 10 phthalates that are regulated by the several governments. A change of concentrations over time for phthalates and internal standards was measured to verify the feasibility of using an auto sampler that facilitates analyzing multiple samples. Both standards maintained constant concentrations over the appropriate time for analysis. A certified reference material under the auspices of the Korea Research Institute of Standards and Science was used to verify the calibration curve obtained by the pyrolyzer GC/MS method, and a deviation was considered similar to the solvent extraction GC/MS method. Then, the limit of detection and limit of quantitation values were confirmed for various consumer products. To verify the reliability of the method, a comparative test with several accredited testing institutes was conducted, and the results were within the standard deviations of the results provided by the institutes. These results indicate that the pyrolyzer GC/MS method can be used in not only screening but also in accurate quantitative analysis.     

Quantitative gas chromatography/time-of-flight mass spectrometry: a review

Time-of-flight (TOF) instruments have recently gained popularity in quantitative analyses. Normally, TOF mass spectrometers are used for accurate mass measurements for empirical formula verification. However, over the past decade, they have been used quantitatively as well. Because of the fast separations and narrow peaks that result from gas chromatography separations, scanning mass spectrometers are not ideal detectors. TOF mass spectrometers, however, have the ability to collect spectra at a faster rate. Two-dimensional gas chromatography has also been introduced to further resolve peaks from complex matrices. Two-dimensional gas chromatography results in a faster separation as well as narrower peaks. This paper reviews the methods currently in the literature for the quantitation of compounds using one- and two-dimensional gas chromatography and TOF mass spectrometry detection.     

Multicapillary gas chromatography coupled to inductively coupled plasma-time-of-flight mass spectrometry for rapid mercury speciation analysis

A simple, rapid and accurate method on the basis of multicapillary gas chromatography (MCGC) combined with inductively coupled plasma-time-of-flight mass spectrometry (ICP-TOFMS) was developed for speciation analysis of methylmercury (MeHg⁺) and inorganic mercury (Hg²⁺). The potential of the ICP-TOFMS for transient multi-isotope detection of very short signals (peak width of 0.4 s at half peak height) was evaluated. Two injection systems (purge-and-trap (PTI) and split (SI) injections) were compared in terms of species separation resolution and transient signal profile. Using purge-and-trap injection, after in situ derivatization of the ionic mercury species with sodium tetraethylborate, a baseline separation of MeHg⁺ and Hg²⁺ was achieved within a chromatographic run of <35 s. To correct for matrix-induced ion signal variation and instrumental drift, propylmercury (PrHg⁺) was used as internal standard. Detection limits of 16 and 257 fg g⁻¹ for MeHg⁺ (as Hg) and Hg²⁺, respectively, were achieved. The analytical precision (R.S.D. (%)) for 10 successive injections of a standard mixture containing 10 pg MeHg⁺ (as Hg) and Hg²⁺ was 1.2% for MeHg⁺ and 4.1% for Hg²⁺. The method was validated by analysis of two biological certified reference materials (CRM): a dogfish muscle (DORM-2) and a freeze-dried tuna fish (CRM 464).     

Solid phase microextraction and gas chromatography mass spectrometry analysis of Zingiber officinale and Curcuma longa

SPME analysis of Zingiber officinale Roscoe and Curcuma longa L. were performed by using a DVB/CARB/PDMS fiber. The SPME analysis of Zingiber officinale showed that the main components found were camphene (7.27%), geranial (8.37%), α-zingiberene (14.50%), α-farnesene (9.14%), β-bisabolene (6.52%), and β-sesquiphellandrene (9.92%). The SPME analysis of Curcuma longa showed that main components were p-cymene (12.96%) and ar-turmerone (12.08%). Other components were β-phellandrene (7.86%), terpinolene (6.97%), ar-curcumene (8.53%), α-zingiberene (8.46%), and β-sesquiphellandrene (7.37%).     

High speed analysis of underivatized drugs by gas chromatography–mass spectrometry

The technique of choice for many types of forensic drug confirmations is gas chromatography/mass spectrometry (GC/MS). Significant amounts of analytical time can be involved in a GC/MS run. The use of a 0.1 mm i.d. fused silica capillary column with hydrogen carrier gas can significantly increase the speed of an analysis without sacrificing resolution. Nanogram levels of underivatized drugs, from amphetamine to strychnine, can be eluted in less than twelve minutes. The multitasking system permits data acquisition, while performing data reduction on the previous run.     

基于气相色谱-质谱联用技术的高通量细胞表型分析方法

研究开发了一种基于96孔板培养和气相色谱-质谱联用(GC-MS)技术的高通量细胞表型分析方法。该方法分别以48种物质作为唯一能源对大肠杆菌进行培养,利用GC-MS研究野生型和yfcC基因改造大肠杆菌对各物质的分解代谢情况,实现高通量的细胞表型分析。结果显示,野生型和yfcC基因过表达大肠杆菌对14种物质的代谢能力有显著差异,yfcC基因过表达大肠杆菌对甘氨酸和柠檬酸的代谢能力明显强于野生型大肠杆菌,而对其他物质的代谢能力较弱,我们推测可能是由于yfcC基因促进乙醛酸代谢,导致yfcC过表达菌株对甘氨酸的代谢能力较强;野生型和yfcC基因敲除大肠杆菌间分解有显著差异的共16种物质,其中yfcC基因敲除大肠杆菌对丙氨酸、乳糖、肌醇和柠檬酸的代谢能力较强。该方法简单、高效,可以为未知基因功能研究提供更多代谢功能相关的参考数据。     

Direct analysis of ultra-trace semiconductor gas by inductively coupled plasma mass spectrometry coupled with gas to particle conversion-gas exchange technique

An inductively coupled plasma mass spectrometry (ICPMS) coupled with gas to particle conversion-gas exchange technique was applied to the direct analysis of ultra-trace semiconductor gas in ambient air. The ultra-trace semiconductor gases such as arsine (AsH₃) and phosphine (PH₃) were converted to particles by reaction with ozone (O₃) and ammonia (NH₃) gases within a gas to particle conversion device (GPD). The converted particles were directly introduced and measured by ICPMS through a gas exchange device (GED), which could penetrate the particles as well as exchange to Ar from either non-reacted gases such as an air or remaining gases of O₃ and NH₃. The particle size distribution of converted particles was measured by scanning mobility particle sizer (SMPS) and the results supported the elucidation of particle agglomeration between the particle converted from semiconductor gas and the particle of ammonium nitrate (NH₄NO₃) which was produced as major particle in GPD. Stable time-resolved signals from AsH₃ and PH₃ in air were obtained by GPD-GED-ICPMS with continuous gas introduction; however, the slightly larger fluctuation, which could be due to the ionization fluctuation of particles in ICP, was observed compared to that of metal carbonyl gas in Ar introduced directly into ICPMS. The linear regression lines were obtained and the limits of detection (LODs) of 1.5 pL L⁻¹ and 2.4 nL L⁻¹ for AsH₃ and PH₃, respectively, were estimated. Since these LODs revealed sufficiently lower values than the measurement concentrations required from semiconductor industry such as 0.5 nL L⁻¹ and 30 nL L⁻¹ for AsH₃ and PH₃, respectively, the GPD-GED-ICPMS could be useful for direct and high sensitive analysis of ultra-trace semiconductor gas in air.     

Potential of fermentation profiling via rapid measurement of amino acid metabolism by liquid chromatography-tandem mass spectrometry

Monitoring amino acid metabolism during fermentation has significant potential from the standpoint of strain selection, optimizing growth and production in host strains, and profiling microbial metabolism and growth state. A method has been developed based on rapid quantification of underivatized amino acids using liquid chromatography-electrospray tandem mass spectrometry (LC-MS-MS) to monitor the metabolism of 20 amino acids during microbial fermentation. The use of a teicoplanin-based chiral stationary phase coupled with electrospray tandem mass spectrometry allows complete amino acid analyses in less than 4 min. Quantification is accomplished using five isotopically labeled amino acids as internal standards. Because comprehensive chromatographic separation and derivatization are not required, analysis time is significantly less than traditional reversed- or normal-phase LC-based amino acid assays. Intra-sample precisions for amino acid measurements in fermentation supernatants using this method average 4.9% (R.S.D.). Inter-day (inter-fermentation) precisions for individual amino acid measurements range from 4.2 to 129% (R.S.D.). Calibration curves are linear over the range 0-300 microg/ml, and detection limits are estimated at 50-450 ng/ml. Data visualization techniques for constructing semi-quantitative fermentation profiles of nitrogen source utilization have also been developed and implemented, and demonstrate that amino acid profiles generally correlate with observed growth profiles. Further, cellular growth events, such as lag-time and cell lysis can be detected using this methodology. Correlation coefficients for the time profiles of each amino acid measured illustrate that while several amino acids are differentially metabolized in similar fermentations, a select group of amino acids display strong correlations in these samples, indicating a sub-population of analytes that may be most useful for fermentation profiling.     

Fast, low-pressure gas chromatography triple quadrupole tandem mass spectrometry for analysis of 150 pesticide residues in fruits and vegetables

We developed and evaluated a new method of low-pressure gas chromatography-tandem mass spectrometry (LP-GC/MS-MS) using a triple quadrupole instrument for fast analysis of 150 relevant pesticides in four representative fruits and vegetables. This LP-GC (vacuum outlet) approach entails coupling a 10 m, 0.53 mm i.d., 1 μm film analytical column between the MS transfer line and a 3 m, 0.15 mm i.d. capillary at the inlet. The MS creates a vacuum in the 10 m analytical column, which reduces the viscosity of the He carrier gas and thereby shifts the optimal flow rate to greater velocity. By taking advantage of the H(2)-like properties of He under vacuum, the short analytical column, a rapid oven temperature ramp rate, and the high selectivity and sensitivity of MS/MS, 150 pesticides were separated in <6.5 min. The 2.5 ms dwell time and 1 ms interscan delay of the MS/MS instrument were critical for achieving >8 data points across the 2-3 s wide peaks. To keep dwell and cycle times constant across all peaks, each segment consisted of 30 analytes (60 transitions). For assessment, we injected extracts of spiked broccoli, cantaloupe, lemon, and sweet potato from the updated QuEChERS sample preparation method. Average recoveries (n=72) were 70-120% for 144 of the pesticides, and reproducibilities were <20% RSD for all but 4 analytes. Also, detection limits were <5 ng/g for all but a few pesticides, depending on the matrix. In addition to high quality performance, the method gave excellent reliability and high sample throughput, including easy peak integration to obtain rapid results.     

Recent applications of gas chromatography with high‐resolution mass spectrometry

Gas chromatography coupled to high‐resolution mass spectrometry is a powerful analytical method that combines excellent separation power of gas chromatography with improved identification based on an accurate mass measurement. These features designate gas chromatography with high‐resolution mass spectrometry as the first choice for identification and structure elucidation of unknown volatile and semi‐volatile organic compounds. Gas chromatography with high‐resolution mass spectrometry quantitative analyses was previously focused on the determination of dioxins and related compounds using magnetic sector type analyzers, a standing requirement of many international standards. The introduction of a quadrupole high‐resolution time‐of‐flight mass analyzer broadened interest in this method and novel applications were developed, especially for multi‐target screening purposes. This review is focused on the development and the most interesting applications of gas chromatography coupled to high‐resolution mass spectrometry towards analysis of environmental matrices, biological fluids, and food safety since 2010. The main attention is paid to various approaches and applications of gas chromatography coupled to high‐resolution mass spectrometry for non‐target screening to identify contaminants and to characterize the chemical composition of environmental, food, and biological samples. The most interesting quantitative applications, where a significant contribution of gas chromatography with high‐resolution mass spectrometry over the currently used methods is expected, will be discussed as well.     

Comparison of comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry and gas chromatography-mass spectrometry for the analysis of tobacco essential oils

A sample of tobacco essential oil was analyzed using gas chromatography-mass spectrometry (GC/MS) and comprehensive two-dimensional gas chromatography coupled to a time-of-flight mass spectrometry (GC × GC/TOFMS), respectively. In the GC/MS analysis, serially coupled columns were used. By comparing the GC/MS results with GC × GC/TOFMS results, many more components in the essential oil could be found within the two-dimensional separation space of GC × GC. The quantitative determination of components in the essential oil was performed by GC × GC with flame ionization detection (FID), using a method of multiple internal standards calibration.     

中药质谱分析方法及应用研究

分别从中药成分分析、活性筛选和代谢组学三方面对质谱技术在中药研究中的应用进展进行了全面综述.在中药成分分析方面,重点介绍了寡糖异构体的分析方法,以及质谱指纹图谱技术在中药成分分析及质量控制中的应用;在活性筛选方面,分别介绍了超滤-质谱、细胞膜色谱-质谱、微透析-质谱、亲和色谱-质谱、强度衰减质谱、修饰琼脂糖珠-质谱和直接分析质谱等技术及其应用;在代谢组学研究方面,对中药治疗肝损伤、肾虚、心肌梗死和糖尿病等疾病方面的研究进展进行了阐述.上述内容充分反映了质谱技术在中药创新性研究中的重要性.     

Enhanced mass resolution tandem mass spectrometry method for 2,3,7,8-tetrachlorodibenzo-p-dioxin detection with ion trap mass spectrometry using high damping gas pressure

Damping gas flow was optimized for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) determination using ion trap mass spectrometer. A tandem mass spectrometry (MS-MS) method with better than unit-mass resolution (mass width, 0.3 u) was developed at a damping gas flow of 1.5 ml/min and a collision-induced dissociation (CID) voltage of 3.30 V. The relative standard deviation (R.S.D.) at the enhanced resolution was 2.9% in 24 h of consecutive injections. The detection limit was significantly improved because the efficiency of both precursor ion trapping and fragmentation increased with the damping gas flow. Product ion yield was 4.5 times higher and limit of detection was 3.2 times lower than at the default flow (0.3 ml/min and 1.65 V).     

Indirect hydrogen analysis by gas chromatography coupled to mass spectrometry (GC–MS)

Gas chromatography (GC) is an analytical tool very useful to investigate the composition of gaseous mixtures. The different gases are separated by specific columns but, if hydrogen (H₂) is present in the sample, its detection can be performed by a thermal conductivity detector or a helium ionization detector. Indeed, coupled to GC, no other detector can perform this detection except the expensive atomic emission detector. Based on the detection and analysis of H₂ isotopes by low‐pressure chemical ionization mass spectrometry (MS), a new method for H₂ detection by GC coupled to MS with an electron ionization ion source and a quadrupole analyser is presented. The presence of H₂ in a gaseous mixture could easily be put in evidence by the monitoring of the molecular ion of the protonated carrier gas. Copyright © 2013 John Wiley & Sons, Ltd.