GC/MS on an LC/MS instrument using atmospheric pressure photoionization

Atmospheric pressure (AP) GC/MS was first introduced by Horning et al. [E.C. Horning, M.G. Horning, D.I. Carroll, I. Dzidic, R.N. Stillwell, Anal. Chem. 45 (1973) 936] using ⁶³Ni as a beta-emitter for ionization. Because, at the time special instrumentation was required, the technique was only applied with consistency to negative ion environmental studies where high sensitivity was required [T. Kinouchi, A.T.L. Miranda, L.G. Rushing, F.A. Beland, W.A. Korfmacher, J. High Resolut. Chromatogr., Chromatogr. Commun. 13 (1990) 281]. Currently, AP ion sources are commonly available on LC/MS instruments and recently a method was reported for converting an AP-LC/MS ion source to a combination AP-LC/MS:GC/MS source [C.N. McEwen, R.G. McKay, J. Am. Soc. Mass Spectrom. 16 (2005) 1730]. Here, we report the use of atmospheric pressure photoionization (APPI) with GC/MS and compare this to AP chemical ionization (APCI) GC/MS and electron ionization (EI) GC/MS. Using a nitrogen purge gas, we observe excellent chromatographic resolution and abundant molecular M⁺ and MH⁺ ions as well as structurally significant fragment ions. Comparison of a 9.8 eV UV lamp with a 10.6 eV lamp, as expected, shows that the higher energy lamp gives more universal ionization and more fragment ions than the lower energy lamp. While there are clear differences in the fragment ions observed by APPI-MS versus EI-MS, there are also similarities. As might be expected from the ionization mechanism, APPI ionization is similar to low energy EI. These odd electron fragment ions are useful in identifying unknown compounds by comparison to mass spectra in computer libraries.     

Selected ion storage versus tandem MS/MS for organochlorine pesticides determination in drinking waters with SPME and GC-MS

The use of two modes for mass spectrometry (MS) detection with an ion trap instrument, selected ion storage (SIS) and tandem mass spectrometry (MS/MS), are compared for the solid-phase microextraction (SPME)–gas chromatography (GC) coupled to mass spectrometry (GC-MS) determination of 16 priority organochlorine pesticides (OCPs) in drinking water samples at the ultratrace levels (ng?L^?1) required by official guidelines in the European legislation. Experimental parameters investigated for the SPME sample preparation were: the type of coating (100?µm polydimethylsiloxane, PDMS, and 65?µm poly(dimethylsiloxane)–divinylbenzene, PDMS/DVB), SPME modality, extraction and desorption times and desorption temperature and the methanol percentage in the SPME working solution. Under the calculated optimal conditions two methodologies were developed, one for SIS and the other for MS/MS modes. The detection limits, precision and accuracy were evaluated for both alternatives and were appropriate to the official guidelines requirements. The SPME–GC-MS(SIS) methodology offered LODs from 0.2–6.6?ng?L^?1, precision below 13% and recoveries between 83 and 110%. The SPME–GC–MS/MS methodology provided limits of detection (LODs) ranging from 0.3 to 7.6 ng?L^?1, % RSD were ≤14% and recoveries of 79–108% were achieved. After the results observed within an Interlaboratory Exercise, the latest MS methodology was selected for the pursued analysis in real drinking water samples. Also, the good results in this round-robin exercise validate the proposed SPME–GC–MS/MS methodology.     

快速溶剂萃取-气相色谱-串联质谱法测定血中巴比妥类药物

提出了气相色谱-串联质谱法测定血中巴比妥类药物(巴比妥、苯巴比妥、异戊巴比妥、司可巴比妥)含量的方法。样品以乙酸乙酯-环己烷(1+1)混合液为萃取剂,经快速溶剂萃取仪提取后,提取液用氮气吹干后以1.0mL甲醇溶解,通过VF-5MS色谱柱分离,采用电子轰击离子源多反应监测模式进行质谱测定。4种巴比妥类药物的质量浓度与其峰面积均在10～1 000μg.L-1之间呈线性关系,检出限(3S/N)在0.07～0.26μg.L-1之间。以空白血液样品为基体进行回收试验,测得回收率在77.8%～93.4%之间,测定值的相对标准偏差(n=7)在2.3%～6.9%之间。     

Coupling of an atmospheric-samling ion source with an ion-trap mass spectrometer

An atomospheric-sampling glow-discharge ionization source has been interfaced with an ion-trap mass spectrometer. Under optimum conditions, the efficiency of ion injection is 1–5%. Several factors have a significant effect on the ion injection efficiency, including the voltages on the three-element lens system situated between the ion-source exit and the ion-trap entrance end-cap, the pressure of the bath gas present in the ion-trap vacuum housing, the nature of the bath gas and the amplitude of the radiofrequency voltage applied to the ring electrode during ion injection. Collision-induced dissociation (and electron detachment from anions) is also observed for some ions on injection, depending on the conditions. The most important experimental variables in determining the extent to which dissociation (or electron detachment) occurs are the nature of the bath gas, the bath gas presure and the radiofrequency voltage applied to the ring electrode during injection. These effects are illustrated with data obtained for polyatomic anions injected from the golw-discharge ion source.     

Analysis of poly-beta-hydroxybutyrate in environmental samples by GC-MS/MS

Application of gas chromatography-mass spectrometry (GC-MS) can significantly improve trace analyses of compounds in complex matrices from natural environments compared to gas chromatography only. A GC-MS/MS technique for determination of poly-beta-hydroxybutyrate (PHB), a bacterial storage compound, has been developed and used for analysis of two soils stored for up to 319 d, fresh samples of sewage sludge, as well as a pure culture of Bacillus megaterium. Specific derivatization of beta-hydroxybutyrate (3-OH C4:0) PHB monomer units by N-tert-butyl-dimethylsilyl-N-methyltrifluoracetamide (MTBSTFA) improved chromatographic and mass spectrometric properties of the analyte. The diagnostic fragmentation scheme of the derivates tert-butyldimethylsilyl ester and ether of beta-hydroxybutyric acid (MTBSTFA-HB) essential for the PHB identification was shown. The ion trap MS was used, therefore the scan gave the best sensitivity and with MS/MS the noise decreased, so the S/N was better and also with second fragmentation the amount of ions increased compared to SIM. The detection limit for MTBSTFA-HB by GC-MS/MS was about 10(-13) g microL(-1) of injected volume, while by GC (FID) and GC-MS (scan) it was around 10(-10) g microL(-1) of injected volume. Sensitivity of GC-MS/MS measurements of PHB in arable soil and activated sludge samples was down to 10 pg of PHB g(-1) dry matter. Comparison of MTBSTFA-HB detection in natural soil sample by GC (FID), GC-MS (scan) and by GC-MS/MS demonstrated potentials and limitations of the individual measurement techniques.     

气相色谱-串联质谱法测定白酒中16种增塑剂

采用气相色谱-串联质谱法测定白酒中16种增塑剂的含量。样品经30℃水浴真空旋转蒸发10min去除乙醇后,用正己烷萃取,漩涡振荡1min,取上层有机相用TR-5MS色谱柱分离,选择反应监测扫描(SRM)模式测定。16种增塑剂的质量浓度在5~1 000μg·L-1范围内与其峰面积呈线性关系,检出限(3S/N)在5~15μg·kg-1之间。在50,100,500μg·kg-1等3个浓度水平进行加标回收试验,回收率在70.5%~120%之间,相对标准偏差(n=6)小于15%。     

Sensitive analytical methods for 22 relevant insecticides of 3 chemical families in honey by GC-MS/MS and LC-MS/MS

Several methods for analyzing pesticides in honey have been developed. However, they do not always reach the sufficiently low limits of quantification (LOQ) needed to quantify pesticides toxic to honey bees at low doses. To properly evaluate the toxicity of pesticides, LOQ have to reach at least 1 ng/g. In this context, we developed extraction and analytical methods for the simultaneous detection of 22 relevant insecticides belonging to three chemical families (neonicotinoids, pyrethroids, and pyrazoles) in honey. The insecticides were extracted with the QuEChERS method that consists in an extraction and a purification with mixtures of salts adapted to the matrix and the substances to be extracted. Analyses were performed by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) for the pyrazoles and the pyrethroids and by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) for the neonicotinoids and ethiprole. Calibration curves were built from various honey types fortified at different concentrations. Linear responses were obtained between 0.2 and 5 ng/g. Limits of detection (LOD) ranged between 0.07 and 0.2 ng/g, and LOQ ranged between 0.2 and 0.5 ng/g. The mean extraction yields ranged between 63 % and 139 % with RSD <25 %. A complete validation of the methods also examined recovery rates and specificity. These methods were applied to 90 honey samples collected during a 2009–2010 field study in two apiaries placed in different anthropic contexts.

快速溶剂萃取-气相色谱-串联质谱法测定血中12种催眠类药物

提出了气相色谱-串联质谱法测定血液中12种催眠类药物含量的方法。样品以乙酸乙酯-环己烷-丙酮(2+2+1)混合液为萃取剂,使用氧化铝吸附剂达到在线净化的效果,经快速溶剂萃取仪提取后,提取液用氮气吹干,用甲醇0.5mL溶解,通过VF-5MS色谱柱分离,采用电子轰击离子源多反应监测模式进行测定。12种催眠类药物的质量浓度与其峰面积均在50.0~1 000μg·L-1之间呈线性关系,测定下限(10S/N)在0.02~4.7μg·L-1之间。加标回收率在65.4%~98.2%之间,测定值的相对标准偏差在0.9%~14.8%之间。     

Multiresidue GC-MS/MS pesticide analysis for evaluation of tea and herbal infusion safety

ABSTRACT

A fast, simple, low-cost and high-throughput multiresidue pesticide analysis method was developed and validated for 300 pesticides in herbal and fruit infusion samples based on modified QuEChERS (quick, easy, cheap, effective, rugged and safe) procedure combined with gas chromatography coupled with tandem mass spectrometry method (GC-MS/MS). The objectives were to develop low cost GC-MS/MS method, validate the method in accordance to SANTE/11,813/2017 guidance document and application in routine. The results obtained using different GC and MS/MS parameters were evaluated in order to develop quick, robust, accurate and effective multiresidue method. Total analysis time was 28 min with 0.6 µL injection volume. For accurate quantification, matrix-matched calibration (MMC) curves (in range of 10 µg/kg – 250 µg/kg) were applied to compensate matrix effect. The limits of quantification (LOQ) were ranged between 0.06 µg/kg and 135 µg/kg, and for the majority of the pesticides the LOQ were below the regulatory maximum residue limits. Most recoveries at 10 µg/kg and 100 µg/kg were in the range 70%–120% indicating satisfactory accuracy. The validated method was applied to commercial herbal and fruit infusion products detecting chlorpyriphos, DEET, tebuconazole, terbuthylazine, piperonyl butoxide, biphenyl, pendimethalin, pirimiphos-methyl and p,p’-DDE in more than 100 samples from 1,466 so risk assessment on human health was calculated specially for those pesticides.     

气相色谱-串联质谱法测定稻米中毒死蜱及其代谢物

提出了气相色谱-串联质谱法测定稻米中毒死蜱及其代谢物3,5,6-三氯-2-羟基吡啶(TCP)含量的方法。样品经含体积分数为1%盐酸的乙腈提取,盐析并浓缩至近干后,残渣用乙酸乙酯溶解TCP用N-甲基-N-叔丁基二甲基硅基三氟乙酰胺衍生化,用气相色谱-串联质谱法测定,外标法定量。毒死蜱及TCP的质量浓度与峰面积均在0.02～0.4mg.L-1范围呈线性关系,测定下限(10S/N)依次为0.5,0.2μg.kg-1。在3个浓度水平下进行了回收和精密度试验,毒死蜱和TCP的回收率分别在94.3%～111.9%和95.1%～109.6%范围内,相对标准偏差(n=5)分别在1.7%～4.0%和3.1%～11.6%范围内。     

气相色谱-串联质谱法测定生姜中25种农药残留量

采用气相色谱-串联质谱法测定生姜中25种农药的残留量。样品用乙腈提取,过NH2/Carbon固相萃取柱净化,将淋出液浓缩后用正己烷-丙酮(9+1)溶液定容。通过VF-5MS色谱柱分离,串联质谱测定。25种农药的质量浓度在0.020～0.500mg.L-1范围内与其峰面积均呈线性关系,检出限(3S/N)在0.2～10.0μg.kg-1之间。加入两个浓度水平的农药标准溶液进行了回收试验,多数农药的回收率在77%～130%之间,相对标准偏差(n=5)均小于20%。     

气相色谱-三重四极杆质谱分析人参炮制品中的挥发性成分

人参炮制的化学成分变化研究主要集中在皂苷和糖类,本文首次从挥发性成分角度阐释了人参不同炮制品的物质基础。利用气相色谱-质谱联用(GC-MS/MS)方法,对鲜参、生晒参和红参中挥发性成分及其衍生规律进行研究。采用TG-5SILMS非极性气相色谱柱,以He为载气,通过NIST MS Spectral Database对挥发性成分进行检测并鉴定。鲜参、生晒参、红参中分别检出30、33和34种挥发性成分,其中生晒参中(-)-斯巴醇含量为鲜参含量的31.98倍,辛醛等8种挥发性成分为鲜参中含量的3倍以上,红参中有环癸等10种挥发性成分为鲜参中含量的3倍以上。生晒参和红参中各有4种挥发性成分在鲜参中未检出。     

QuEChERS/气相色谱质谱法同时测定膨化食品中多环芳烃类物质

建立了同时测定膨化食品中12种多环芳烃(PAHs)的Qu EChERS/气相色谱三重四极杆质谱(GC-MS/MS)的方法。称取2 g(精确至0.01 g)样品,加入10 mL正己烷提取15 min,采用500 mg乙二胺-N-丙基硅烷化硅胶(PAS)和500 mg C18粉末进行净化,净化后进行GC-MS/MS分析测定。实验结果表明,12种多环芳烃在气相色谱中的分离度良好,在1~1000 ng/mL的浓度范围内线性关系良好。加标回收率测定范围为49%~130%,RSD在1.0%~10%(n=7)之间。检出限在0.20~0.66μg/kg之间,定量限在0.66~2.20μg/kg之间。该方法数据可靠、操作简单快捷、灵敏度高,适合大批量样品中PAHs的测定。     

'Information-Based-Acquisition' (IBA) technique with an ion-trap/time-of-flight mass spectrometer for high-throughput and reliable protein profiling

Highly complex protein mixtures can be analyzed after proteolysis using liquid chromatography/mass spectrometry (LC/MS). In an LC/MS run, intense peptide ions originating from high-abundance proteins are preferentially analyzed using tandem mass spectrometry (MS(2)), so obtaining the MS(2) spectra of peptide ions from low-abundance proteins is difficult even if such ions are detected. Furthermore, the MS(2) spectra may produce insufficient information to identify the peptides or proteins. To solve these problems, we have developed a real-time optimization technique for MS(2), called the Information-Based-Acquisition (IBA) system. In a preliminary LC/MS run, a few of the most intense ions detected in every MS spectrum are selected as precursors for MS(2) and their masses, charge states and retention times are automatically registered in an internal database. In the next run, a sample similar to that used in the first run is analyzed using database searching. Then, the ions registered in the database are excluded from the precursor ion selection to avoid duplicate MS(2) analyses. Furthermore, real-time de novo sequencing is performed just after obtaining the MS(2) spectrum, and an MS(3) spectrum is obtained for accurate peptide identification when the number of interpreted amino acids in the MS(2) spectrum is less than five. We applied the IBA system to a yeast cell lysate which is a typical crude sample, using a nanoLC/ion-trap time-of flight (IT/TOF) mass spectrometer, repeating the same LC/MS run five times. The obtained MS(2) and MS(3) spectra were analyzed by applying the Mascot (Matrix Science, Boston, MA, USA) search engine to identify proteins from the sequence database. The total number of identified proteins in five LC/MS runs was three times higher than that in the first run and the ion scores for peptide identification also significantly increased, by about 70%, when the MS(3) spectra were used, combined with the MS(2) spectra, before being subjected to Mascot analysis.     

HS/GC-MS/MS法检测海产品中二甲苯

建立了顶空进样/气相色谱-串联三重四极杆质谱(HS/GC-MS/MS)检测海产品中3种二甲苯同分异构体的方法。海产品经90℃温育和振荡平衡40 min顶空进样,HP-INNOWax色谱柱分离,程序升温,在多反应监测(MRM)模式下进行GC-MS/MS检测,外标法定量。结果表明,3种二甲苯同分异构体在5.0~100.0μg/kg范围内呈良好线性,相关系数均在0.99以上,方法检出限为2.5μg/kg,定量下限为5.0μg/kg。黄鱼样品在6.0、15.0、50.0μg/kg加标水平下的平均回收率为89.6%~112.4%,相对标准偏差(RSD)不大于11.5%。采用建立的方法测定了不同海产品中二甲苯同分异构体的含量。该法操作简单、定性准确、灵敏度较高,适于海产品中二甲苯残留量的测定。     

Determination of 3-MCPD by GC-MS/MS with PTV-LV injector used for a survey of Spanish foodstuffs

3-Monochloropropane-1,2-diol (3-MCPD) is the most common chemical contaminant of the group of chloropropanols. It can occur in foods and food ingredients at low levels as a result of processing, migration from packaging materials during storage and domestic cooking. A sensitive method for determination of 3-MCPD in foodstuffs using programmable temperature vaporization (PTV) with large-volume injection (LVI) gas chromatography (GC) with tandem mass spectrometry detection (MS/MS) has been developed and optimized. The optimization of the injection and detection parameters was carried out using statistical experimental design. A Plackett-Burman design was used to estimate the influence of resonance excitation voltage (REV), isolation time (IT), excitation time (ET), ion source temperature (IST), and electron energy (EE) on the analytical response in the ion trap mass spectrometer (ITMS). Only REV was found to have a statically significant effect. On the other hand, a central composite design was used to optimize the settings of injection temperature (T(inlet)), vaporization temperature (T(vap)), vaporization time (t(vap)) and flow (Flow). The optimized method has an instrumental limit of detection (signal-to-noise ratio 3:1) of 0.044 ng mL(-1). From Valencian, Spain, supermarkets 94 samples of foods were surveyed for 3-MCPD. Using the optimized method levels higher than the limit established for soy sauce by the European Union were found in some samples. The estimated daily intake of 3-MCPD throughout the investigated foodstuffs for adults and children was found about 0.005 and 0.01%, respectively, of the established provisional tolerable daily intake.     

Determination of 77 Multiclass Pesticides and Their Metabolitesin Capsicum and Tomato Using GC-MS/MS and LC-MS/MS

A quick, sensitive, and reproducible analytical method for the determination of 77 multiclass pesticides and their metabolites in Capsicum and tomato by gas and liquid chromatography tandem mass spectrometry was standardized and validated. The limit of detection of 0.19 to 10.91 and limit of quantification of 0.63 to 36.34 µg·kg⁻¹ for Capsicum and 0.10 to 9.55 µg·kg⁻¹ (LOD) and 0.35 to 33.43 µg·kg⁻¹ (LOQ) for tomato. The method involves extraction of sample with acetonitrile, purification by dispersive solid phase extraction using primary secondary amine and graphitized carbon black. The recoveries of all pesticides were in the range of 75 to 110% with a relative standard deviation of less than 20%. Similarly, the method precision was evaluated interms of repeatability (RSDr) and reproducibility (RSD_wR) by spiking of mixed pesticides standards at 100 µg·kg⁻¹ recorded anRSD of less than 20%. The matrix effect was acceptable and no significant variation was observed in both the matrices except for few pesticides. The estimated measurement uncertainty found acceptable for all the pesticides. This method found suitable for analysis of vegetable samples drawn from market and farm gates.     

气相色谱-质谱/质谱检测原油中 27、24、21-降胆甾烷

随着地质勘探研究工作的深入和发展,一些常规检测的生物标记化合物,已无法满足特殊区域地质研究的需要,地球化学家把注意力放在一些含量极微,但具有明确断代标志意义或明确生源的标志物身上,而这些组分靠常规的GC-MS分析根本检测不到。而GC-MS/MS由于是二级质谱串联比GC-MS增加     

GC-MS/MS Determination of Steroid Hormones in Urine Using Solid-Phase Derivatization as an Alternative to Conventional Methods

Solid-phase analytical derivatization (SPAD) is a promising hybrid sample preparation technique combining the clean-up and preconcentration of the sample in a single step. In this work, a novel SPAD method based on the preparation of trimethylsilyl (TMS) derivatives of steroid hormones (testosterone, estrone, DHT, estriol, estradiol, and progesterone) in Phenomenex Strata C18-E (100 mg, 1 mL) cartridges has been developed and applied for their GC-MS/MS determination in human urine samples. The proposed procedure allows the detection and quantification of steroids with limits of 1.0–2.5 and 2.5–5 ng/mL, respectively. These characteristics are comparable with those obtained with a conventional liquid–liquid extraction, while the recovery of analytes in the proposed SPAD procedure is higher. The major advantages of SPAD are a short derivatization time, high efficiency, and the possibility to automatize the procedure. However, its cost-effectiveness in routine practice is still questionable.     

气相色谱-串联质谱法测定茶叶中24种农药残留量

采用气相色谱-串联质谱法测定茶叶中24种农药残留量。茶叶样品经乙腈超声振荡提取,Cleanert TPT固相萃取柱净化,乙腈-甲苯(3+1)溶液洗脱。在气相色谱分离中用RTX-5MS色谱柱为固定相,在质谱分析中采用多反应监测模式。采用内标法定量,24种农药的线性范围均为0.005~1.0mg·L-1,检出限(3S/N)在0.2~1.2μg·kg-1之间。在0.01,0.1,1.0mg·kg-1等3个浓度水平进行加标回收试验,回收率在67.5%~122%之间,测定值的相对标准偏差(n=6)在0.60%~9.9%之间。