Gas chromatography--inductively coupled plasma--time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental water samples

The application of inductively coupled plasma--time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental waters is described. Construction of the transfer line was achieved by means of a relatively simple and rapid coupling procedure. Derivatization of the ionic lead species was achieved by in-situ propylation with sodium tetrapropylborate; simultaneous extraction of the derivatized compounds in hexane was followed by separation and detection by capillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight mass spectrometry. Detection limits for the different organolead species ranged from 10 to 15 fg (as Pb), corresponding to procedural detection limits between 50 and 75 ng L(-1), on the basis of a 50 mL snow sample, extraction with 200 microL hexane, and subsequent injection of 1 microL of the organic extract on to the column. The accuracy of the system was confirmed by additional analysis of the water samples by capillary gas chromatography coupled with microwave-induced plasma-atomic-emission spectrometry and the analysis of a standard reference material CRM 605 (road dust) with a certified content of trimethyllead.     

Gas chromatography – inductively coupled plasma – time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental water samples

The application of inductively coupled plasma – time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental waters is described. Construction of the transfer line was achieved by means of a relatively simple and rapid coupling procedure. Derivatization of the ionic lead species was achieved by in-situ propylation with sodium tetrapropylborate; simultaneous extraction of the derivatized compounds in hexane was followed by separation and detection by capillary gas chromatography hyphenated to inductively coupled plasma–time-of-flight mass spectrometry. Detection limits for the different organolead species ranged from 10 to 15 fg (as Pb), corresponding to procedural detection limits between 50 and 75 ng L^–1, on the basis of a 50 mL snow sample, extraction with 200 μL hexane, and subsequent injection of 1 μL of the organic extract on to the column. The accuracy of the system was confirmed by additional analysis of the water samples by capillary gas chromatography coupled with microwave-induced plasma–atomic-emission spectrometry and the analysis of a standard reference material CRM 605 (road dust) with a certified content of trimethyllead.     

Determination of nalbuphine using high-performance liquid chromatography coupled to photodiode-array detection and gas chromatography coupled to mass spectrometry.

A procedure involving capillary column gas chromatography coupled to mass spectrometry and a method involving liquid chromatography coupled to a diode-array detector have been developed for the analysis of nalbuphine. The extraction step is the same for both techniques and involves extraction under alkaline conditions in chloroform-2-propanol-n-heptane (50:17:33, v/v/v) with levallorphan as the internal standard. After purification by acidic extraction and back alkaline extraction, drugs are derivatized with N,O-bis-(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane for gas chromatography-mass spectrometry and directly injected for high-performance liquid chromatography-diode-array detection. The limits of detection are 2.0 and 25.0 ng/mg, respectively.     

In situ derivatization–liquid liquid extraction as a sample preparation strategy for the determination of urinary biomarker prolyl‐4‐hydroxyproline by liquid chromatography–tandem mass spectrometry

Polar analytes that possess protic functional groups have often been treated with alkyl chloroformates to decrease their polarity and increase their volatility prior to gas chromatography–mass spectrometry analysis. This derivatization reaction has two distinct advantages. It proceeds smoothly in aqueous media, and the desired reaction products are efficiently separated from interfering ionic components by their extraction into a water‐immiscible organic phase. In the present work, the derivatization–liquid liquid sample preparation was examined in detail for analysis of a potential urinary dipeptide biomarker l ‐prolyl‐4‐l ‐hydroxyproline (PHP) by downstream liquid chromatography coupled to electrospray mass spectrometry. PHP was treated with a series of alkyl and fluoroalkyl chloroformates in aqueous media, and the detected reaction products were investigated. Smooth conversion of PHP into the N‐isobutyloxycarbonyl isobutyl ester was accomplished by the coupled action of isobutanol, isobutyl chloroformate and the pyridine catalyst. This derivative afforded a highest detector response from all the derivatized forms examined, including the nonderivatized PHP. A simple isocratic elution on a common RP‐C18 HPLC column coupled with tandem mass spectrometry, and use of the synthesized heptadeuterated analog (D7‐PHP) as an internal standard, enabled validation of the method and determination of PHP in human urine in less than 5 min. The in situ derivatization–liquid liquid extraction has thus been demonstrated to be a useful sample preparation strategy for the analysis of polar metabolites by liquid chromatography–tandem mass spectrometry in the complex urine matrix. Copyright © 2012 John Wiley & Sons, Ltd.     

Kovats and lee retention indices determined by gas chromatography/mass spectrometry for organic compounds of environmental interest

Retention indices of standard organic compounds of environmental interest were determined by gas chromatography/mass spectrometry, using a DB-5 fused-silica capillary column. Retention indices are useful references for tentative compound identification by gas chromatography, or confirmation by gas chromatography/mass spectrometry. They provide elution order for isomers that might be indistinguishable based on mass spectra. Modified Kovats and Lee retention indices are given for polycyclic aromatic hydrocarbons; sulfur heterocycles; nitrogen heterocycles; aromatic amines; oxygen heterocycles; phenols; alcohols; ketones; alkanes; nitriles; and methylesters of fatty, dicarboxylic, and aromatic acids for comparison and reference. Retention index values for heterocycles by gas chromatography/mass spectrometry are comparable with gas chromatography values previously reported.     

Comparison of gas chromatographic and gas chromatographic/mass spectrometric techniques for the analysis of TNT and related nitroaromatic compounds

The use of capillary column gas chromatography and gas chromatography/mass spectrometry for the analysis of a series of standard solutions (0.1 to 10 μg/ml) of 2,4,6-trinitrotoluene (TNT) and eight other nitroaromatic components was evaluated. The techniques included gas chromatography with electron capture detection (GC/ECD), full scan and selected ion monitoring gas chromatography/mass spectrometry with electron impact ionization (EI/FS and EI/SIM), full scan and selected ion monitoring gas chromatography/mass spectrometry with positive ion chemical ionization using methane reagent gas (PICI/FS and PICI/SIM), and full scan and selected ion monitoring gas chromatography/mass spectrometry with negative ion chemical ionization using methane reagent gas (NICI/FS and NICI/SIM). The performance of the techniques was comapared by determining the linear response range, precision, and detection limits of the analyses.     

Rapid characterization of the chemical constituents of Cortex Fraxini by homogenate extraction followed by UHPLC coupled with Fourier transform ion cyclotron resonance mass spectrometry and GC–MS

Cortex Fraxini is an important traditional Chinese medicine. In this work, a rapid and reliable homogenate extraction method was applied for the fast extraction for Cortex Fraxini, and the method was optimized by response surface methodology. Ultra high performance liquid chromatography combined with Fourier transform ion cyclotron resonance mass spectrometry and gas chromatography with mass spectrometry were established for the separation and characterization of the constituents of Cortex Fraxini. Liquid chromatography separation was conducted on a C₁₈ column (150 mm × 2.1 mm, 1.8 μm), and gas chromatography separation was performed on a capillary with a 5% phenyl‐methylpolysiloxane stationary phase (30 m × 0.25 mm × 0.25 mm) by injection of silylated samples. According to the results, 33 chemical compounds were characterized by liquid chromatography with mass spectrometry, and 11 chemical compounds were characterized by gas chromatography with mass spectrometry, and coumarins were the major components characterized by both gas chromatography with mass spectrometry and liquid chromatography with mass spectrometry. The proposed homogenate extraction was an efficient and rapid method, and coumarins, phenylethanoid glycosides, iridoid glycosides, phenylpropanoids, and lignans were the main constituents of Cortex Fraxini. This work laid the foundation for further study of Cortex Fraxini and will be helpful for the rapid extraction and characterization of ingredients in other traditional Chinese medicines.     

Characterization of crude oil biomarkers using comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry

Oil samples from Recôncavo basin (NE Brazil), previously analyzed by traditional techniques such as gas chromatography coupled to tandem mass spectrometry, were evaluated using comprehensive two‐dimensional gas chromatography coupled to quadrupole mass spectrometry and comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry along with simplified methods of samples preparation to evaluate the differences and advantages of these analytical techniques to better understand the development of the organic matter in this basin without altering the normal distribution of the compounds in the samples. As a result, the geochemical parameters calculated by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry described better the origin, maturity, and biodegradation of both samples probably by increased selectivity, resolution, and sensitivity inherent of the multidimensional technique. Additionally, the detection of the compounds such as, the C(14α‐) homo‐26‐nor‐17α‐hopane series, diamoretanes, nor‐spergulanes, C₁₉–C₂₆ A‐nor‐steranes and 4α‐methylsteranes resolved and detected by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry were key to classify and differentiate these lacustrine samples according to their maturity and deposition conditions.     

Determination of Trace Amounts of Organic Pollutants in the Yellow River by Capillary Column Gas Chromatography-Mass Spectrometry

Abstract

The trace organic pollutants in the Yellow River enriched by a solvent extraction method were pre-separated into four different fractions of fatty hydrocarbons, polycyclic aromatic hydrocarbons, polar compounds and organic acids and were analyzed by the use of combined capillary column gas chromatography-mass spectrometry. Using the combined techniques of relative retention value, mass spectra and mass chromatogram, more than 60 organic pollutants were identified, among which 16 fatty hydrocarbons and 6 polycyclic aromatic hydrocarbons which were quantitatively analyzed. The concentration range of fatty hydrocarbon was 5–800 ng/l, and that of polycyclic aromatic hydrocarbon was 0-90ng/l.     

固相萃取-高效液相色谱-串联质谱法同时测定土壤中氟喹诺酮、四环素和磺胺类抗生素

建立了固相萃取-高效液相色谱-串联质谱法同时检测土壤中氟喹诺酮类、四环素类和磺胺类18种抗生素的分析方法。土样经含50%乙腈的磷酸盐缓冲液(pH=3)提取后,以SAX-HLB串联小柱净化富集,在HPLC/MS/MS多反应监测模式下进行定性及定量分析。添加浓度为200和50μg/kg时,土壤中氟喹诺酮类、四环素类、磺胺类的加标回收率分别为67.2%～89.0%,62.2%～85.4%和55.8%～97.4%;其相对标准偏差为1.1%～17.2%。以3倍信噪比估算出氟喹诺酮类、四环素类、磺胺类的检出限分别为3.4～8.9μg/kg,0.56～0.91μg/kg和0.07～1.85μg/kg。应用此方法检测6种不同类型土壤样品,结果表明,污灌区土壤中检出有抗生素,浓度为1.72～119.6μg/kg。     

Analyses of pesticides and their metabolites in foods and drinks

The importance of matrix pretreatment, sample extraction and clean-up in multiresidue methods for pesticide analyses is discussed, with emphasis on alternative new techniques attempted worldwide such as accelerated solvent extraction, microwave-assisted extraction, solid-phase extraction, solid-phase micro-extraction, matrix solid-phase dispersion, supercritical fluid chromatography, ultrasonic extraction and gel permeation chromatography. Detection employing capillary gas chromatography and high-performance liquid chromatography in conjunction with mass spectrometry, capillary electrophoresis, immunoassay techniques and others is summarized.     

High resolution capillary GC–MS analysis of low molecular weight organic compounds in municipal wastewater

High resolution capillary gas chromatography–mass spectrometry has been used in combination with various sample preparation methods to analyze a wide range of low molecular weight organic contaminants in municipal wastewaters. Volatile organic compounds were extracted using a purge and trap concentrator connected directly to a wide bore DB-624 capillary column. Because of the high organic load in wastewater samples, this method was preferred to the more sensitive closed loop stripping technique which suffered from competition effects and insufficient adsorbent capacity. Volatile and semi-volatile base/neutral compounds and acids were extracted with dichloromethane at pH 11 and pH 2, respectively, or were recovered using a simultaneous distillation-extraction procedure. Acidic compounds were subsequently derivatized using diazomethane methylation. Both fractions were separated with a 30m DB-5ms capillary column. Specific ionic substances (LAS, NTA, EDTA) were isolated by solid-phase extraction then derivatized with diazomethane (LAS) or acetyl chloride in n-butanol (NTA, EDTA) before GC–MS analysis. This array of techniques enabled the identification of more than 150 organic contaminants in the influent of a municipal wastewater treatment plant in northern suburban Paris. The individual concentrations of these contaminants ranged from < 0.1 μg/l to 5.7 mg/l.     

Rapid extraction and analysis of organic compounds from solid samples using coupled supercritical fluid extraction/gas chromatography

Summary Direct coupling of supercritical fluid extractions with gas chromatography (SFE-GC) allows the extraction, concentration, and gas chromatographic analysis of organic analytes from solid samples to be performed in less than 1 h. Coupling of the supercritical fluid extraction step with a capillary gas chromatographic column is achieved using a standard on-column injector and requires no modification of the gas chromatograph. Maximum sensitivity is achieved and analyte degradation or loss is minimized since the extracted species are quantitatively transferred into the fusedsilica capillary gas chromatographic column where they are cryogenically focused prior to normal gas chromatographic analysis using flame ionization (SFE-GC/FID) or mass spectral (SFE-GC/MS) detection. SFE-GC analysis yields good chromatographic peak shapes that compare favorably with those obtained using standard on-column injection techniques. Class-selective extractions can be achieved by performing multiple SFE-GC analyses with different extraction pressures. The ability of coupled SFE-GC to yield rapid extraction and analysis of organic analytes is demonstrated for a variety of samples including polycyclic aromatic hydrocarbons (PAHs) from treated wood, urban dust, and river sediment, phenolic species from wood smoke particulates, nicotine from tobacco, biological markers from coal, and flavor components from food products.

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Schnelle Extraktion und Analyse von organischen Verbindungen aus festen Proben durch Kopplung von Extraktion mit überkritischen fluiden Phasen und GC

     

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.     

Effect of organic matter content in the trace analysis of triazines in various types of soils with GC-NPD

Summary Recent work demonstrated that the combination of microwave assisted solvent extraction (MASE) and capillary gas chromatography with selective nitrogen detection (GC-NPD) is a viable approach for the efficient determination of triazine herbicides in soils. However, for soils with a high organic matter content or the injection of more concentrated extracts to obtain lower LOD's the performance of gas chromatographic analysis of uncleaned extracts is hampered. This results in both a decrease of the chromatographic response of analytes and a decrease in the life time of the column due to coextracted matrix substances. The effect of various types of soils on the chromatographic analysis of triazine herbicides was studied. It appeared that for the investigated samples with an organic matter content below 5% processing of uncleaned extracts is possible. Samples with a higher organic matter content required a cleanup step. A rapid procedure on 100 mg silica cartridges has been developed using solvents compatible with the MASE extracts and the instrumental analysis. Beside the testing with different standard soils, about 120 samples of an ongoing monitoring program involving three different types of soil (organic matter content: 3–37%) were analysed. The selected compounds atrazine, desethylatrazine, desisopropyl-atrazine and simazine could be assayed in the various soil types to a level of at least 2 μg kg⁻¹. For soil samples with a high organic matter content (>5%), the rapid cleanup procedure allowed the trace analysis of the triazines and considerably increased the life time of the capillary column. Recoveries at levels from 2 to 50 μg kg⁻¹ ranged from 70 to 100% with RSDs ranging from 5.1 to 9.5%. Confirmation of positive samples was carried out by gas chromatography mass spectrometry.     

固相萃取–气相色谱–串联质谱法检测土壤中15种邻苯二甲酸酯

建立了固相萃取结合气相色谱串联质谱联用仪检测土壤中15种邻苯二甲酸酯残留的方法。样品采用丙酮和石油醚超声提取,取上清液浓缩,上弗罗里硅土固相萃取柱净化,收集洗脱液,定容,以气相色谱串联质谱法分析。该方法在20~2 000 ng/g范围内线性关系良好(r~20.999 0),检出限(S/N=3)为0.12~0.61 ng/g。20,50,200 ng/g 3个添加浓度的15种邻苯二甲酸酯的加标回收率在78.9%~101.8%之间,测定结果的相对标准偏差为0.19%~8.34%(n=5)。该方法准确、灵敏,符合痕量分析的要求,适用于土壤中邻苯二甲酸酯类残留的分析。     

Improved sample preparation of glyphosate and methylphosphonic acid by EPA method 6800A and time‐of‐flight mass spectrometry using novel solid‐phase extraction

The employment of chemical weapons by rogue states and/or terrorist organizations is an ongoing concern in the United States. The quantitative analysis of nerve agents must be rapid and reliable for use in the private and public sectors. Current methods describe a tedious and time‐consuming derivatization for gas chromatography–mass spectrometry and liquid chromatography in tandem with mass spectrometry. Two solid‐phase extraction (SPE) techniques for the analysis of glyphosate and methylphosphonic acid are described with the utilization of isotopically enriched analytes for quantitation via atmospheric pressure chemical ionization–quadrupole time‐of‐flight mass spectrometry (APCI‐Q‐TOF‐MS) that does not require derivatization. Solid‐phase extraction‐isotope dilution mass spectrometry (SPE‐IDMS) involves pre‐equilibration of a naturally occurring sample with an isotopically enriched standard. The second extraction method, i‐Spike, involves loading an isotopically enriched standard onto the SPE column before the naturally occurring sample. The sample and the spike are then co‐eluted from the column enabling precise and accurate quantitation via IDMS. The SPE methods in conjunction with IDMS eliminate concerns of incomplete elution, matrix and sorbent effects, and MS drift. For accurate quantitation with IDMS, the isotopic contribution of all atoms in the target molecule must be statistically taken into account. This paper describes two newly developed sample preparation techniques for the analysis of nerve agent surrogates in drinking water as well as statistical probability analysis for proper molecular IDMS. The methods described in this paper demonstrate accurate molecular IDMS using APCI‐Q‐TOF‐MS with limits of quantitation as low as 0.400 mg/kg for glyphosate and 0.031 mg/kg for methylphosphonic acid. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrophilic interaction chromatography coupled to electrospray mass spectrometry for the separation of peptides and protein digests

In this study, the analysis of a peptide set, chosen for their differences in hydrophilicity, and the tryptic digests of bovine cytochrome c and β-lactoglobulin by hydrophilic interaction chromatography–electrospray ionisation mass spectrometry (HILIC–ESI-MS) is demonstrated. Two different types of HILIC phases, i.e., an amide- and an amino-modified silica-based phase, packed into narrow bore or capillary columns, were investigated with separations conducted under either low pH or neutral pH conditions. The separation performance of the two HILIC columns with respect to peak efficiency and selectivity have been documented under these different mobile phase conditions, and the results compared with the performance of a conventional capillary reversed-phase C18 column of similar dimensions. It was found that very good separation of the peptide set could be achieved by using the amide-modified silica column over a broad pH range. Moreover, with the protein digest samples, excellent separation of the tryptic digests was obtained with the amide-modified HILIC column under neutral pH conditions. Compared to the conventional reversed-phase C18 separations, the use of these HILIC columns not only provided complementary separation selectivity, but also offered the capability to identify unique peptides using tandem HILIC–mass spectrometric techniques. These studies therefore highlight the potential of HILIC procedures for future proteomic applications.     

Development of a liquid chromatography-tandem mass spectrometry method for plasma-free metanephrines with ion-pairing turbulent flow online extraction

Liquid chromatography–tandem mass spectrometry has become the preferred technology to measure unconjugated metanephrine and normetanephrine in plasma because of its high sensitivity and specificity over immunoassay and gas chromatography–mass spectrometry. In our earlier study, plasma metanephrines were extracted with offline ion-pairing solid-phase extraction and quantified by liquid chromatography–tandem mass spectrometry with porous graphitic carbon column based chromatography. In this study, we aim to automate the sample preparation with turbulent flow online extraction technology and maintain or improve the analytical performance previously achieved from the offline approach. The online extraction was done with a mixed-mode cation exchange turbulent flow chromatography column assisted with ion-pairing reagent and porous graphitic column was used for chromatographic separation. The total online extraction and analytical LC runtime was 12 min. This method was linear from 6.3 to 455.4 pg/mL for metanephrine; 12.6 to 954.5 pg/mL for normetanephrine with an accuracy of 80.6% to 93.5% and 80.9% to 101.7%, respectively. The lower limit of quantitation was 6.3 pg/mL for metanephrine and 12.6 pg/mL for normetanephrine. Inter-assay and intra-assay precision for metanephrine and normetanephrine at low and high concentration levels ranged from 2.0% to 10.5%. In conclusion, we have developed a fast and sensitive automated online turbulent flow extraction method for the quantitative analysis of plasma metanephrines. Ion-pairing reagent was necessary for the success of this method.     

Analysis of acrylamide in cooked foods by liquid chromatography tandem mass spectrometry

A method using liquid chromatography tandem mass spectrometry (LC-MS-MS) with electrospray for the analysis of acrylamide in foods is reported. The method comprises the addition of deuterium-labelled acrylamide-d3, extraction with water, mixed mode solid phase extraction, ultrafiltration and a graphitised carbon column for chromatography. The transitions m/z 72 > 55, 72 > 54, 72 > 44, 72 > 27, 72 > 72 and 75 > 58 were recorded in multiple reaction monitoring mode for identification and quantification. In-house validation data for products from potatoes and cereals (30 to 10,000 microg kg(-1)) are presented (accuracy 91 to 102%, relative standard deviation 3 to 21%). Interlaboratory validation data (comparison with gas chromatography mass spectrometry, 25 to 2000 microg kg(-1)) showed excellent results (r2 = 0.998).