Studies on neurosteroids. IX. Characterization of estrogens in rat brains using gas chromatography-tandem mass spectrometry.

The characterization of the classical estrogens (estrone, estradiol, estriol) and guaiacol estrogens (2-hydroxyestrone 3-methyl ether, 4-hydroxyestrone 3-methyl ether) in rat brains was performed using gas chromatography-tandem mass spectrometry (GC-MS-MS). Estrogens were purified from Wistar strain rat brains by some chromatographic pre-treatments, such as solid-phase extraction, preparative thin-layer chromatography or preparative high-performance liquid chromatography. After the derivatization with O-methylhydroxylamine and/or N,O-bis(trimethylsilyl)trifluoroacetamide, estrogens were identified by comparison of their chromatographic behavior during GC-MS-MS operating in the product ion scan mode and comparison with the product ion MS spectra of an authentic sample. These evidences suggested that estrogens exist in rat brains as neurosteroids or neuroactive steroids.     

Pulsed flow modulation two-dimensional comprehensive gas chromatography-tandem mass spectrometry with supersonic molecular beams

Pulsed flow modulation (PFM) two-dimensional comprehensive gas chromatography (GC x GC) was combined with quadrupole-based mass spectrometry (MS) via a supersonic molecular beam (SMB) interface using a triple-quadrupole system as the base platform, which enabled tandem mass spectrometry (MS-MS). PFM is a simple GC x GC modulator that does not consume cryogenic gases while providing tunable second GC x GC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. The 20-ml/min second column flow rate involved with PFM is handled, splitless, by the SMB interface without affecting the sensitivity. The combinations of PFM GC x GC-MS with SMB and PFM GC x GC-MS-MS with SMB were explored with the analysis of diazinon and permethrin in coriander. PFM GC x GC-MS with SMB is characterized by enhanced molecular ion and tailing-free fast ion source response time. It enables universal pesticide analysis with full scan and data analysis with reconstructed single ion monitoring on the enhanced molecular ion and another prominent high mass fragment ion. The elimination of the third fragment ion used in standard three ions method results in significantly reduced matrix interference. GC x GC-MS with SMB improves the GC separation, and thereby our ability for sample identification using libraries. GC-MS-MS with SMB provides better reduction (elimination) of matrix interference than GC x GC-MS. However, it is a target method, which is not always applicable. GC x GC-MS-MS does not seem to further reduce matrix interferences over GC-MS-MS and unlike GC x GC-MS, it is incompatible with library identification, but it is beneficial to have both GC x GC and MS-MS capabilities in the same system.     

Comparison of gas chromatographic-mass spectrometric methods for screening of chlorotriazine pesticides in soil.

The performance of a coupled technique resulting from the combination of gas chromatography with a selective mass spectrometric technique (tandem mass spectrometry) (GC-MS-MS) with collisionally activated dissociation (CAD) and multi-reaction monitoring (MRM) was compared with that of GC-low resolution MS (GC-LRMS) at a resolving power of 1000 and GC-high-resolution MS (GC-HRMS) at resolving powers of 5000 and 10,000 for the determination of atrazine, simazine, cyanazine, deethylatrazine and deisopropylatrazine in polluted soil samples. GC-MS-MS daughter ion spectra for the parent ions [M]+. and [M - CH3]+ were generated using collisionally activated dissociation and studied. Also, by optimizing the collision energy for maximum sensitivity a method for screening chlorotriazines by MRM was developed. Analyses of soil sample extracts showed that GC-MS-MS overcomes interferences from other chlorotriazines and interfering compounds that could not be removed by GC-HRMS or GC-LRMS at resolving powers of 10,000 and 1000, respectively. The limits of detection for GC-MS-MS and GC-HRMS at a signal-to-noise ratio of 10 ranged between 1 and 24 pg, with a mean relative standard deviation of 25-30%. Soil samples known to contain chlorotriazines and their degradation products were analysed by GC-MS-MS and the results obtained were compared with those given by GC-HRMS at resolving powers of 5000 and 10,000, with quantification differences of 25-30%.     

Recent progress in the analysis of sugar monomers from complex matrices using chromatography in conjunction with mass spectrometry or stand-alone tandem mass spectrometry

Analysis of trace levels of carbohydrate monomers in complex matrices requires excellent discrimination of the peaks of interest from background noise. Minimizing contaminating peaks introduced during sample preparation and chromatography is extremely important. However, the exquisite selectivity of the mass spectrometer is essential as a chromatographic detector in this regard. Traditionally gas chromatography-mass spectrometry (GC-MS) has been the method of choice for trace analysis of derivatized carbohydrates. Recent improvements in commercial tandem mass spectrometers (MS-MS) are encouraging the use of GC-MS-MS for improved specificity in trace analysis. There has also been an explosion in applications of electrospray ionization (ESI) for sensitive introduction of polar molecules (including sugars) into the mass spectrometer. This has encouraged ongoing developments in high-performance liquid chromatography-mass spectrometry (LC-MS) and MS-MS of underivatized carbohydrates. This has the potential to dramatically simplify sample preparation. However, as yet LC-MS and MS-MS do not match the sensitivity of GC-MS or GC-MS-MS. Developments in analysis of sugar monomers from complex matrices using chromatography (GC/LC) in conjunction with mass spectrometry (MS, MS-MS) or stand-alone MS-MS are discussed.     

Simultaneous determination of phenolic acids and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one in wheat (Triticum aestivum L.) by gas chromatography-tandem mass spectrometry

A procedure using gas chromatography and tandem mass spectrometry (GC-MS-MS) has been developed for the identification and quantification of some allelochemicals in wheat (Triticum aestivum L.). The quantities of allelochemicals in wheat shoots ranged from 2.9 to 110 mg per kilogram of dry shoot residues. Compared with gas chromatography-mass spectrometry (GC-MS), the GC-MS-MS technique significantly increased instrument selectivity and sensitivity, thereby providing more reliable quantitation results in the determination of the phytotoxic compounds examined during this allelopathy research.     

气相色谱-串联质谱法快速测定调味品中3种糠醛类物质

建立了同时测定调味品中糠醛、5-甲基糠醛和5-羟甲基糠醛的气相色谱-串联质谱法(GC-MS/MS)。对样品的前处理方法及GC-MS/MS分析条件进行优化,样品经乙酸乙酯萃取,GC-MS/MS多反应监测模式(MRM)进行测定。3种糠醛类物质在0.001～20 mg/L范围内均呈良好的线性关系,相关系数为0.999 0～0.999 5;检出限(S/N=3)均为0.005 mg/kg,加标回收率为86%～95%。该法简便、快速、溶剂用量少,可消除调味品中复杂基质的干扰,结果准确可靠、灵敏度高,适用于调味品中3种糠醛类物质的同时测定。     

Identification of certain chemical agents in complex organic solutions by gas chromatography/tandem mass spectrometry

Analytical methods that are used for the detection and identification of chemicals related to the Chemical Weapons Convention in complex organic solutions were developed. A matrix modified by the addition of complex diesel oil background compounds and interferences was used for the development of a gas chromatography-mass spectrometry or gas chromatography-tandem mass spectrometry (GC-MS or GC-MS/MS) method for unambiguous identification of the scheduled chemicals. Co-elution of diethyl N,N-dimethylphosphoramidate and ethyl N,N-dimethylphosphoramidocyanidate, which are not separated by GC, was identified by GC-MS. Although GC-MS can identify the compounds, GC-MS/MS identification has greater accuracy and sensitivity in the case of complex matrixes. Four scheduled chemicals were accurately and selectively identified against numerous interfering substances by GC-MS/MS. The fragmentation chemistry of these compounds using MS/MS analysis was investigated.     

气相色谱-四极杆-飞行时间质谱和气相色谱-串联质谱对水果、蔬菜中208种农药残留筛查确证能力的对比

对比研究了气相色谱-串联质谱(GC-MS/MS)与气相色谱-四极杆-飞行时间质谱(GC-QTOF/MS)在水果、蔬菜中208种农药多残留检测中基质效应及方法学效能的差异,提出两种仪器在农药残留检测方面的特点和适用范围,为残留检测分析提供参考。在苹果、柑橘、番茄、黄瓜4种基质,3个添加浓度(5.0、10.0和20.0 μg/kg)下,两种仪器中均有93.0%以上的农药回收率在70%~120%范围内且相对标准偏差(RSD)≤20%(n=5)。检测灵敏度方面,绝大部分农药在两种仪器的检出限均低于5.0 μg/kg,满足各国农药残留限量的要求,且GC-MS/MS灵敏度更高,线性范围更宽,定量能力更加准确。筛查确证方面,GC-QTOF/MS在快速、高通量筛查、准确定性及非目标化合物鉴定等方面表现出了优势。     

Reduction of analysis time in gas chromatography. Application of low-pressure gas chromatography-tandem mass spectrometry to the determination of pesticide residues in vegetables

An alternative to conventional capillary gas chromatography (GC) is evaluated as a new approach to determine pesticide residues in vegetables. Low-pressure gas chromatography-tandem mass spectrometry (LP-GC-MS-MS) is proposed after a fast and simple extraction of the vegetable samples with dichloromethane and without clean up. The use of the above-mentioned GC technique reduced the total time required to determine 72 pesticides to less than half the present time (31 min), increasing the capability of a monitoring routine laboratory. The use of guard column and plug of carbofrit into the glass liner in combination with LP-GC was evaluated. The method was validated with limits of quantitation low enough to determine the pesticide residues at concentrations below the maximum residue levels stated by legislation. In order to assess its applicability to the analysis of real samples, 25 vegetable samples previously determined using conventional-capillary GC-MS-MS were analysed by LP-GC-MS-MS. The results obtained with the compared techniques showed differences lower than 0.01 mg kg(-1).     

多次溶剂萃取-气相色谱/串联质谱法测定热熔胶中的多环芳烃

建立了热熔胶中16种多环芳烃( PAHs)的多次溶剂萃取-气相色谱/串联质谱测定方法。详细研究了样品的萃取条件、净化条件和气相色谱/串联质谱测定条件,并与气相色谱-质谱法进行了对比。样品以10 mL正己烷为萃取溶剂,于60℃超声萃取20 min,萃取液依次经冷冻后离心、二甲基亚砜萃取2次、正己烷反萃取2次进行净化,得到的净化液以气相色谱/串联质谱法多反应监测( MRM)模式进行检测。本方法的线性相关系数( R2)均大于0.9969,检出限为1.0~10μg/kg,精密度小于6.3%,16种PAHs的加标回收率为80.4%~117.6%。考察了串联质谱检测的基质效应,发现基质效应不明显。本方法检出限优于气相色谱-质谱法(23~94μg/kg),并能增加定性和定量分析的准确性。本方法灵敏、准确可靠,满足热熔胶中PAHs测试要求。     

Carbohydrate profiling of bacteria by gas chromatography-mass spectrometry and their trace detection in complex matrices by gas chromatography-tandem mass spectrometry.

Bacterial cellular polysaccharides are composed of a variety of sugar monomers. These sugars serve as chemical markers to identify specific species or genera or to determine their physiological status. Some of these markers can also be used for trace detection of bacteria or their constituents in complex clinical or environmental matrices. Analyses are performed, in our hands, employing hydrolysis followed by the alditol acetate derivatization procedure. Substantial improvements have been made to sample preparation including simplification and computer-controlled automation. For characterization of whole cell bacterial hydrolysates, sugars are analyzed by gas chromatography-mass spectrometry (GC-MS). Simple chromatograms are generated using selected ion monitoring (SIM). Using total ion GC-MS, sugars can be readily identified. In more complex clinical and environmental samples, markers for bacteria are present at sufficiently low concentrations that more advanced instrumentation, gas chromatography-tandem mass spectrometry (GC-MS-MS), is preferred for optimal analysis. Using multiple reaction monitoring, MS-MS is used (replacing more conventional SIM) to ignore extraneous chromatographic peaks. Triple quadrupole and ion trap GC-MS-MS instruments have both been used successfully. Absolute chemical identification of sugar markers at trace levels is achieved, using MS-MS, by the product spectrum.     

气相色谱-串联质谱法快速测定鸡肉组织中氯羟吡啶残留量

采用气相色谱-串联质谱法快速测定鸡肉组织中的氯羟吡啶残留,样品经乙腈-水提取,冷冻脱脂后,直接以丙酸酐衍生,采用气相色谱-串联质谱(GC-MS/MS)进行分析,多反应监测(MRM)模式检测。结果表明,氯羟吡啶在0.5~40 ng/m L浓度范围内呈良好的线性关系,方法的定量下限为5.0μg/kg,回收率为101.5%~111.8%,相对标准偏差(RSD)小于7.7%。该方法简便、快速、灵敏度高,重现性好,可用于鸡肉组织中氯羟吡啶的快速确证检测。     

Recently developed GC/MS and LC/MS methods for determining NSAIDs in water samples

Pharmaceuticals have become major targets in environmental chemistry due to their presence in aquatic environments (following incomplete removal in wastewater treatment or point-source contaminations), threat to drinking water sources and concern about their possible effects to wildlife and humans. Recently several methods have been developed for the determination of drugs and their metabolites in the lower nanogram per litre range, most of them using solid-phase extraction (SPE) or solid-phase microextraction (SPME), derivatisation and finally gas chromatography mass spectrometry (GC-MS), gas chromatography tandem mass spectrometry (GC-MS/MS) and liquid chromatography electrospray tandem mass spectrometry (LC-ES/MS/MS). Due to the elevated polarity of non-steroidal anti-inflamatory drugs (NSAIDs), analytical techniques based on either liquid chromatography coupled to mass spectrometry (LC-MS) and gas chromatography coupled to mass spectrometry (GC-MS) after a previous derivatisation step are essential. The most advanced aspects of current GC-MS, GC-MS/MS and LC-MS/MS methodologies for NSAID analysis are presented.     

Determination of Hormones and Non-ionic Surfactant Degradation Products in Small-Volume Aqueous Samples from Soil Columns Using LC-ESI-MS-MS and GC-MS

The leaching of two estrogens, 17β-estradiol and estrone, and two degradation products of non-ionic surfactants, octylphenol and nonylphenol, through a soil column were studied to estimate their transport behavior. Different concentration methods (lyophilization, solid phase extraction, and liquid–liquid extraction) were evaluated for analyzing these compounds in small effluent fractions (30–50 mL) collected. Liquid chromatography-mass spectrometry (LC-MS-MS) and gas chromatography-mass spectrometry (GC-MS) were employed for quantitative analysis of these compounds. After comparison, the lyophilization-LC-MS-MS method was found to be best suited for the analysis of the two estrogen hormones and the liquid–liquid extraction-GC-MS method best for the analysis of the two phenols in small samples in the soil column study. Because of their high sorption capacity, these compounds were mostly sorbed in the upper part of the soil column and were difficult to detect in column effluent.     

Analysis of endosulfan and its metabolites in human serum using gas chromatography-tandem mass spectrometry

A new analytical method combining solid-phase extraction and gas chromatography-tandem mass spectrometry (GC-MS-MS) is proposed to determine the insecticide endosulfan as well as its metabolites endosulfan-ether, -lactone, and -sulfate in human serum. Most matrix interferences are avoided using a cleanup step included in the sample treatment and an instrumental technique such as GC-MS-MS, which presents a high sensitivity and selectivity. Recoveries of spiked compounds range between 94.8 and 100.4% and 93.4 and 99.7% at fortification levels of 10 and 30 ng/mL, respectively. The relative standard deviation is lower than 17.6% in all cases, and the limits of detection calculated range from 6 to 19 pg/mL. Serum samples of nine agricultural workers that spray endosulfan into greenhouses in Almería (Spain) and two nonoccupationally exposed people are analyzed, and endosulfan is found in all the samples studied.     

气相色谱-串联质谱法快速测定禽蛋中203种农药及化学污染物残留

建立了禽蛋中203种农药及化学污染物残留的气相色谱-串联质谱(GCMS/MS)检测方法.样品用乙腈振荡提取,经ODS C18+Carb串联固相萃取柱净化,乙腈-甲苯(3:1,v/v)洗脱,洗脱液浓缩至0.5mL,氮吹至近干,加1mL正己烷超声溶解后,在气相色谱-串联质谱多反应监测(MRM)模式下进行测定.在1倍MRL(...     

Determination of priority pesticides in baby foods by gas chromatography tandem quadrupole mass spectrometry

A gas chromatography-tandem quadrupole mass spectrometry (GC-MS/MS) method for the determination of twelve priority pesticides, and transformation products (e.g. metabolites) specified in the EU Baby Food Directive 2003/13/EC is described. Prior to GC-MS/MS analysis, co-extractives were removed from acetonitrile extracts using dispersive solid phase extraction with octadecyl (200 mg) and primary secondary amine (50 mg) sorbents. The clean up proved essential for the satisfactory long-term chromatographic performance during the analysis of a range of representative commercially pre-prepared baby food samples. Extracts spiked with pesticides at 1-8 microg kg(-1), yielded average recoveries in the range 60-113% with relative standard deviations less than 28%.     

Determination of ergosterol on mouldy building materials using isotope dilution and gas chromatography-tandem mass spectrometry

Ergosterol content of building materials was quantified using gas chromatography-tandem mass spectrometry (GC-MS-MS) in an ion trap with external ionisation. Hydrolysing the samples by classic extraction at 85 degrees C for 90 min in vials was faster, more precise and safer than microwave assisted extraction. [4-2H2]ergosterol was synthesised and used as internal standard, giving method standard deviation of 5-10% from 10 to 30 ng to 10-15 microg ergosterol in the sample. The use of GC-MS-MS meant that no solid-phase extraction clean-up was needed, so one person could easily prepare 40-80 samples per day.     

Validation study on 660 pesticide residues in animal tissues by gel permeation chromatography cleanup/gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry

A new method using gel permeation chromatography (GPC) cleanup followed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS-MS) has been established for quantitative determination of 437 pesticide residues in animal tissues such as beef, mutton, pork, chicken, and rabbit. Based on an appraisal of the characteristics of both GC-MS and LC-MS-MS, validation experiments were conducted for 660 pesticides. In the method, 10 g animal samples were mixed with 20 g sodium sulfate and extracted with 35 mL of cyclohexane+ethyl acetate (1+1) twice by blender homogenization, centrifugation, and filtration. Evaporation was conducted and an equivalent of 5 g sample was injected into a 400 mm x 25 mm S-X3 GPC column, with cyclohexane+ethyl acetate (1+1) as the mobile phase at a flow rate of 5 mL/min. The 22-40 min fraction was collected for subsequent analysis. For the 368 pesticides determined by GC-MS, the portions collected from GPC were concentrated to 0.5 mL and exchanged with 5 mL hexane twice. For the 69 pesticides by LC-MS-MS, the portions collected from GPC were dissolved with acetonitrile+water (60+40) after taking the extract to dryness with nitrogen gas. In the linear range of each pesticide, the correlation coefficient was r > or = 0.98, exceptions being dinobuton, linuron, and fenamiphos sulfoxide. At the low, medium and high three fortification levels of 0.2-4800 microg/kg, recoveries fell within 40-120%, among which 417 pesticides recoveries between 60% and 120%, accounting for 95%, 20 analytes between 40% and 60%, accounting for 5%. The relative standard deviation was below 28% for all 437 pesticides. The limits of detection for the method were 0.2-600 microg/kg, depending on each pesticide.     

Analysis of estrogens in river sediments by liquid chromatography-electrospray ionisation mass spectrometry. Comparison of tandem mass spectrometry and time-of-flight mass spectrometry

A method has been developed and optimised for the determination of two natural estrogens, estrone (E1) and 17beta-estradiol (E2), and one synthetic estrogen, 17alpha-ethynylestradiol (EE2), in river sediments at the sub-ng/g level. This procedure includes microwave-assisted solvent extraction (MASE), solid-phase extraction and high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) with electrospray ionisation. Using sediments spiked with the three estrogens at 10 ng/g wet weight, efficient extraction (>92%) of all the three analytes was achieved by MASE, and whole-procedure recoveries ranged from 82 to 98%. Optimisation of the LC separation allowed for substantial reduction of ionisation suppression in the electrospray source to a final level of <18% suppression. Time-of-flight mass spectrometry (TOF-MS) and MS/MS were compared for the analysis of sediment extracts, with the latter technique proving to be the most selective. The method detection limits achieved by LC-MS/MS were 15, 30 and 40 pg/g for E1, E2 and EE2, respectively, which were 13-fold lower than those obtained by LC-TOF-MS. Analysis of river sediments collected from the River Ouse, UK, showed the presence of the natural estrogens at sub-ng/g level. E1 levels ranged from 0.40 ng/g (dry weight) to 3.30 ng/g while E2 levels ranged from <0.03 to 1.20 ng/g and EE2 was never detected (<0.04 ng/g).