Gas Chromatography Ion-trap Tandem Mass Spectrometry Research Articles

Determination of benzothiazoles in seafood species by subcritical water extraction followed by solid-phase microextraction-gas chromatography-tandem mass spectrometry: estimating the dietary intake.

Benzothiazoles are high production volume chemicals widely used in many industrial and household applications. However, information on their occurrence in aquatic organisms is very limited, although a high level of bioaccumulation is expected. In this study and for the first time, a method was developed involving subcritical water extraction followed by solid-phase microextraction coupled to gas chromatography-ion trap-tandem mass spectrometry for the determination of five benzothiazoles in seafood. The repeatability and reproducibility of the method were under 21% (%RSD, n=5, 100ngg-1 (dw)), while method detection limits and method quantification limits were between 0.5 and 10ngg-1 (dw) and 1 and 50ngg-1 (dw), respectively. Ten widely consumed fish and shellfish species from the county of Tarragona (Catalonia, Spain) were selected in order to estimate dietary exposure and to assess the human health risks. The most frequently determined compounds were benzothiazole and 2-(methylthio)-benzothiazole, with squid being the species which showed the highest level of benzothiazole (82ngg-1 (dw)). In terms of human exposure, the current concentrations of benzothiazoles found in fish and shellfish could not be compared to threshold values because of the lack of toxicological data.

Comparative study of comprehensive gas chromatography-nitrogen chemiluminescence detection and gas chromatography-ion trap-tandem mass spectrometry for determining nicotine and carcinogen organic nitrogen compounds in thirdhand tobacco smoke

Thirdhand tobacco smoke (THS) constitutes a poorly understood pathway of exposure of non-smokers, especially toddlers, to tobacco-related carcinogens. However, to date most of the carcinogens present in tobacco smoke have not been detected in THS and, therefore, the significance of THS health risk is still unknown. In this study, we have compared the performance of two analytical methods – one based on gas chromatography coupled to ion trap mass spectrometry detection (GC-IT-MS) and the other on comprehensive two-dimensional gas chromatography coupled to a nitrogen chemiluminescence detector (GC×GC-NCD) – for simultaneously determining, in settled house dust, the presence of 16 organic nitrogen carcinogens already detected in tobacco smoke. The target compounds included four aromatic amines, two nitrocompounds, eight N-nitrosamines and two tobacco-specific nitrosamines, as well as nicotine as a tobacco marker. Dust samples were extracted using in-cell clean up pressurized liquid extraction with silica as clean up sorbent and ethyl acetate as the organic solvent, with average recovery of 89%. Although GC-IT-MS, using chemical ionization with methanol and tandem MS, performed well, the optimized GC×GC-NCD gave lower limits of detection (from 4 to 22ngg−1) and better repeatability and reproducibility a low concentration levels (%RSD<8%) and, therefore, was applicable for determining these different groups of carcinogens without the need for derivatization prior to the GC analysis.The performance of the optimized PLE/GC×GC-NCD method was tested by quantifying the target compounds in house dust samples from smokers’ and non-smokers’ homes. The median carcinogen compounds detected was 3.8μgg−1 and 1.1μgg−1 in smokers’ and non-smokers’ house dust, respectively. In this study, we have detected highly carcinogenic aromatic amines and nitro compounds for the first time in settled house dust complementing the state of knowledge of THS composition and providing fresh evidence about THS health risks.

Is deproteinization necessary in the determination of human plasmatic steroids by GC/IT-MS/MS analysis?

For many years concentrations of functional steroid hormones or their precursors have been determined mainly in plasma or serum samples of patients, occasionally in saliva or tissues, or as their metabolites, in urine or amniotic fluid [1]. Gas Chromatography/Mass Spectrometry (GC/MS) is well-suited for the identification of a large number of potential steroids and metabolites due to its high chromatographic resolution capacity and reproducible ionization efficiency [2]. Albumin is dominant in the binding, transport, and delivery of a range of endogenous ligands and pharmaceuticals because it accounts for approximately 60% of the total proteins in blood serum with a typical concentration of 3.4–5.0 g/dL [3]. Biblio graphy shows that protein precipitation for human plasma analysis performed by GC/MS can be performed successfully with methanol by centrifugation [4, 5, 6] with acetonitrile [7, 8, 9] with 70% perchloric acid and n-hexane [10], with 5% sulfosalicylic [11], with ethanol [12], with acetone [13], and with trichloroacetic acid [14]. Other methods for plasma deproteinization focus on physical methods as described [15]. These methods include ultrafiltration and centrifugation with varied molecular weight cut-offs, or using other simple methods such as heating the plasma. However, it has not been shown that these deproteinization methods interfere with gaschromatography-ion trap-tandem mass spectrometry (GC/IT-MS/MS) analysis of plasmatic steroids. Hence, the aim of this work was to identify if it is necessary and useful to apply a deproteinization treatment to human plasma before its analysis in order to determine steroids hormones using GC/IT-MS/MS.

Influence of pre-treatment process on matrix effect for the determination of musk fragrances in fish and mussel

Musk compounds are widely used as fragrances in personal care products. On account of their widespread use and their low biodegradation, they can be found in environmental samples. In our study two extraction methodologies were compared and different clean-up strategies were also studied in order to develop a reliable analytical method, with minimum matrix effect and good detection limits, to determine synthetic musk fragrances- six polycyclic musks, three nitro musks and the degradation product of one polycyclic musk- in fish and mussel samples. The first extraction technique involves a QuEChERS extraction, a consolidate extraction methodology in the field of food analysis of growing interest over recent years, followed by a dispersive solid-phase extraction (dSPE) as clean-up strategy. The second extraction technique consists of a conventional pressurised liquid extraction (PLE) with dichloromethane and an in-cell clean-up to decrease the matrix effect and remove the undesired components⁎present in PLE extracts. Large volume injection (LVI) followed by gas chromatography-ion trap-tandem mass spectrometry (GC-IT-MS/MS) was chosen as the separation and detection technique. Validation parameters, such as method detection limits and method quantification limits were found at ng g−1 levels for both fish and mussel matrices. Good levels of intra-day and inter-day repeatabilities were obtained analysing fish and mussel samples spiked at 50ng g−1 (d.w.) (n=5, RSDs<17%). The developed PLE/GC-IT-MS/MS method was successfully applied to determine the target musk fragrances present in fish and mussel samples from the local market in Tarragona and fish samples from the Ebro River. The results showed the presence of galaxolide (2.97–18.04ng g−1 (d.w.)) and tonalide (1.17–8.42ng g−1 (d.w.)) in all the samples analysed, while the remaining polycyclic musks such as cashmeran, celestolide and phantolide, were only detected in some of the fish samples analysed. None of the samples analysed contained detectable traces of the nitro musks studied.

In-line sequential injection-based hollow-fiber sorptive microextraction as a front-end to gas chromatography–mass spectrometry: a novel fully automatic sample processing technique for residue analysis

A novel and affordable analytical setup is herein reported for automatic flow-through sorptive microextraction of organic contaminants, exploiting polydimethylsiloxane (PDMS) as a front-end to gas chromatography-ion trap-tandem mass spectrometry. The analytical procedure involves a short single-strand PDMS hollow fiber integrated in a sequential injection (SI) network for automatic fluidic handling by programmable flow. The target species are in-line extracted from 10 mL of sample containing 20% (v/v) methanol followed by elution with a metered volume of organic solvent, which is whereupon quantitatively transferred into the programmed temperature vaporization (PTV) injector of the GC. Diffusional resistance to mass transfer was overcome by effecting the overall concentration and stripping steps at a single PDMS tubing interface. The proof of concept of the novel hyphenated system was demonstrated for extraction and determination of organochlorine pesticides (OCPs), namely, heptachlor, dieldrin, endrin, endosulfan, p,p'-dichlorodiphenyldichloroethane, p,p'-dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethylene, and endrin ketone, taken as model analytes, in environmental and industrial waters. Four organic solvents with a broad spectrum of polarity were investigated as eluents in the SI-based assembly, namely, ethyl acetate, methyl tert-butyl ether, hexane, and chloroform. Chloroform was proven the most suitable solvent for expedient elution and fast evaporation in the PTV injector. Under the selected experimental variables, limits of detection (signal-to-noise ratio (S/N) = 3) within the range of 0.3-1.1 ng L(-1), limits of quantification (S/N = 10) of 1.0-3.6 ng L(-1), and method repeatabilities spanning from 1.7 to 4.7% were obtained for the suite of OCPs. The hyphenated flow analyzer was harnessed to the analysis of samples of varying matrix complexity with good relative recoveries (86-112%) in drinking water, surface water, and influent and effluent wastewaters, with quantification limits far below those endorsed by WHO and EU drinking water directives setting maximum allowed concentrations at ≤100 ng L(-1) OCPs.

Validation of a Gas Chromatography–Ion Trap-Tandem Mass Spectrometry Assay for the Simultaneous Quantification of Cocaine, Benzoylecgonine, Cocaethylene, Morphine, Codeine, and 6-Acetylmorphine in Aqueous Solution, Blood, and Skeletal Muscle Tissue

A gas chromatography-ion trap-tandem mass spectrometry method was developed and validated for the simultaneous solid-phase extraction and quantification of cocaine, benzoylecgonine, cocaethylene, morphine, codeine, and 6-monoacteylmorphine in blood, muscle tissue, and water. An assay for total morphine in blood and muscle was also validated. The limit of quantification was ≤ 0.01 mg/kg in muscle and ≤ 0.005 mg/L in blood and water. Good linearity was observed over the concentration ranges studied (r ≥ 0.99). The repeatability (% RSD) at the three concentration levels was typically ≤ 15% and never exceeded 17%. Intermediate precision of ≤ 16% was obtained for all matrices. Deviation < 20% of the nominal concentration was obtained in all repeatability and intermediate precision experiments. Extraction recoveries for cocaine and metabolites ranged from 91% to 110% in water, 81% to 110% in blood, and 61% to 75% in muscle. Recoveries for opiates ranged from 59% to 104% in water, 50% to 95% in blood, and 41% to 79% in muscle. The hydrolysis efficiency for the total morphine assay in blood and muscle ranged from 91% to 99% with within-day and intermediate precisions of ≤ 14% and ≤ 12%, respectively.

Suitability of selective pressurized liquid extraction combined with gas chromatography–ion-trap tandem mass spectrometry for the analysis of polybrominated diphenyl ethers

A one-step extraction and clean-up method using pressurized liquid extraction (PLE) (selective PLE) combined with gas chromatography–ion-trap tandem mass spectrometry (GC–ITMS–MS) was evaluated for the analysis of polybrominated diphenyl ethers (from tri- to hepta-PBDEs) at low concentrations in fish and shellfish samples. To this end, the performance of an on-line PLE extraction/clean-up method and of a classical Soxhlet extraction and clean-up method using a multi-layer modified silica column were compared. The two sample treatment methods provided similar results, although an important reduction in the sample treatment time (40 min per sample) was achieved using the selective PLE method. In addition, the suitability of the PLE combined with GC–ITMS–MS method was evaluated by comparing the results obtained in the analysis of fish samples with those obtained by gas chromatography–high resolution mass spectrometry (GC–HRMS). Good agreement between both techniques was obtained with differences between the mean values of less than 16%. The selective PLE method coupled to GC–ITMS–MS produced accurate results for PBDE determination with low limits of detection (1.0–16.8 pg g −1 wet weight) and quantification (3.1–51 pg g −1 wet weight) as well as good precision (RSD < 16%). This method has been applied to the analysis of PBDEs in fish and shellfish samples collected at fish markets in Catalonia (NE Spain).

Single-run determination of polybrominated diphenyl ethers (PBDEs) di- to deca-brominated in fish meal, fish oil and fish feed by isotope dilution: Application of automated sample purification and gas chromatography/ion trap tandem mass spectrometry (GC/ITMS)

The present paper describes the application of automated cleanup and fractionation procedures of the Power Prep system (Fluid Management Systems) for the determination of polybrominated diphenyl ethers (PBDEs) in feeding stuffs and fish meal and oil. Gas chromatography (GC) separation followed by ion trap tandem mass spectrometry detection in EI mode (ITMS) allowed the analysis of di- to deca-BDEs in the samples matrices used in fish aquaculture. The method developed enabled the determination of 26 native PBDE congeners and 11 13C 12-labelled congeners, including deca-BDE 209, in a single-run analysis, using isotope dilution. The automated cleanup, consisting of a succession of multilayer silica and basic alumina columns previously applied by Wyrzykowska et al. (2009) [28] in combustion flue gas, was succesfully applied in our complex matrices. The method allowed an increase in productivity, i.e. lower time was required to process samples, and simultaneous purification of several samples was achieved at a time, reducing analyst dedication and human error input. Average recoveries of 43–96% were obtained. GC/ITMS can overcome the complexity originating from the sample matrix, eliminating matrix effects by tandem MS, to enable the detection of congeners penta- to nona-BDEs where interferent masses were present. The provisional detection limits, estimated in the samples, were 5–30 pg for di-, tri-, tetra-, and penta-BDEs, 20–65 pg for hexa-, hepta-, octa- and nona-BDEs, and 105 pg for deca-BDE. Reduction of deca-BDE 209 blank values is of concern to ongoing research. Good accuracy was obtained by application of the whole procedure, representing an efficient, low-cost and fast alternative for routine analyses.

Pressurised hot water extraction followed by simultaneous derivatization and headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry for the determination of aliphatic primary amines in sewage sludge

In this paper we describe an environmentally friendly and sensitive method for the determination of ten primary amines in sewage sludge. The method is based on pressurised hot water extraction (PHWE) followed by simultaneous derivatization with pentafluorobenzaldehyde (PFBAY) and headspace solid-phase microextraction (HS-SPME) and subsequent gas-chromatography ion-trap tandem mass spectrometry (GC-IT-MS–MS) analysis. The influence of the main factors on the PHWE of sludge was optimized by a central composite design. For all species the optimal conditions were water at pH 4 as the extracting solvent, an extraction temperature of 100 °C and an extraction time of 15 min. The separation and detection of the ten amines by GC-IT-MS–MS took just 10 min and the entire process took approximately 1 h. Repeatability and reproducibility between days, expressed as RSD (%) ( n = 5), were less than 19 and 24%, respectively. The average limit of detection (LOD) was of 65 μg kg −1 s (range found 9–135) and the average limit of quantification (LOQ) was of 230 μg kg −1 (range found 50–450) of dry weight (d.w.). Under optimized conditions we used this method to determine the compounds in industrial and municipal sewage sludge samples and in sludge from a potable water treatment plant. Methylamine and isobutylamine showed the highest levels in one of the industrial sewage sludge samples (404 and 543 mg kg −1 (d.w.), respectively). To our knowledge, this paper presents for the first time the determination of ten primary amines in sewage sludge samples using PHWE.

Determination of drugs of abuse in water by solid-phase extraction, derivatisation and gas chromatography–ion trap-tandem mass spectrometry

An alternative method for the sensitive determination of several drugs of abuse and some of their metabolites in surface and sewage water samples is proposed. Analytes are concentrated using a solid-phase extraction (SPE) sorbent, converted into the corresponding trimethylsilyl derivatives and selectively determined by gas chromatography (GC) with tandem mass spectrometry (MS/MS) detection. Parameters affecting the performance of extraction, derivatisation and determination steps are systematically investigated. Moreover, the stability of target analytes in sewage water samples is discussed. Under final working conditions, water samples were adjusted at pH 8.5 and concentrated using a 200 mg OASIS HLB SPE cartridge. Analytes were sequentially eluted with ethyl acetate followed by acetone and silylated using N-methyl- N-(trimethylsilyl)trifluoroacetamide (MSTFA). The reaction was completed in 60 min at 80 °C and the mixture injected directly in the GC–MS/MS system without further purification. In most cases, analytes presented a poor stability in sewage water samples; however, once they are submitted to the SPE process, cartridges can be stored at −20 °C for at least 3 months without significant degradation and/or inter-conversion reactions of illicit drugs. The proposed method provided recoveries over 74% and LODs between 0.8 and 15 ng/L for river and treated wastewater samples. In the case of raw wastewater slightly worse recoveries, between 63 and 137%, and similar LODs were attained. Analysis of a limited number of waste and surface water samples confirmed the presence of several illicit drugs in the aquatic environment, with the highest levels and frequency corresponding to benzoylecgonine, the main metabolite of cocaine.

Rapid and sensitive gas chromatography–ion-trap tandem mass spectrometry method for the determination of tobacco-specific N-nitrosamines in secondhand smoke

Tobacco-specific nitrosamines (TSNAs) are some of the most potent carcinogens in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risks. We developed and validated a specific and sensitive method to measure four TSNAs adsorbed to model surfaces and secondhand smoke (SHS) particles using gas chromatography–ion-trap tandem mass spectrometry. In an 18-m 3 room-sized chamber, a smoking machine generated realistic concentrations of SHS that were actively sampled on Teflon-coated fiber glass (TCFG) filters, and passively sampled on cellulose substrates. A simple solid–liquid extraction protocol using methanol as solvent was successfully applied to both substrates with recoveries ranging from 85 to 115%. For each TSNA, tandem MS parameters were optimized and the major fragmentation pathways were elucidated. The method showed excellent performance, with a linear dynamic range from 2 to 1000 ng mL −1, low detection limits (S/N > 3) of 30–300 pg mL −1 and precision with experimental errors below 10% for all compounds. Moreover, no interfering peaks were observed, indicating a high selectivity of MS/MS without the need for a sample clean-up step. This method provides a suitable analytical tool to detect and quantify traces of TSNA in indoor environments polluted with SHS.

Comparison of gas chromatography–ion-trap tandem mass spectrometry systems for the determination of polychlorinated dibenzo- p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls

Two gas chromatography–mass spectrometry systems equipped with an ion-trap mass analyzer working in tandem mode (GC–MS–MS) were evaluated for the determination of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) in food samples. The performance of the two ion-trap instruments, which dispose of an external ion source (ThermoFinnigan GCQ/Polaris) and internal ionization (Varian Saturn 2200), have been compared in terms of linearity, repeatability, limit of detection and long-term precision. Both instruments provided similar run-to-run and day-to-day precisions, ranging from 2% to 8% and between 2% and 13%, and instrumental limits of detection between 0.09 and 0.36 pg injected for PCDD/Fs and from 0.03 to 0.09 pg injected for dioxin-like PCBs. Although both instruments seem to be suitable for food analysis, only the use of external ionization allowed to achieve reliable results for PCDD/F determination at concentrations close to the maximum residue levels established by the EU for foods. Internal ionization provides high limits of detection (from 10- to 30-fold higher) and worse precision (RSD, 14–43%). In contrast, for dioxin-like PCBs both instruments allowed to obtain excellent results with precisions lower than 15%.

Fat transforms ascorbic acid from inhibiting to promoting acid-catalysed N-nitrosation

Background:The major potential site of acid nitrosation is the proximal stomach, an anatomical site prone to a rising incidence of metaplasia and adenocarcinoma. Nitrite, a pre-carcinogen present in saliva, can...

Validation of a gas chromatography—Ion trap tandem mass spectrometry for simultaneous analyse of cocaine and its metabolites in saliva

Cocaine (COC) is one of the most widely used drugs of abuse. Therefore numerous procedures are published in the literature to propose an analysis of this substance and related compounds in different matrixes. In the same way, the authors have described, in a previous work, the simultaneous analysis of COC and three of its metabolites in hair by gas chromatography–ion-trap tandem mass spectrometry (GC–MS/MS) using chemical ionization with isobutane. The present paper investigated the ability to transfer this convenient existing method for hair to another matrix, in occurrence saliva. The aim of this work was then to verify that the whole procedure (solid phase extraction (SPE) and analytical method) was also convenient to analyse simultaneously COC and three of its metabolites in this matrix. Therefore this sensitive GC–MS/MS method has been studied for the simultaneous analysis of COC, anhydroecgonine methylester (AEME), ecgonine methylester (EME) and cocaethylene (COET) in saliva samples. The method has been validated and its performances were evaluated in terms of trueness and precision using quality control (QC) samples. For quantification, the following ranges were found appropriate: 5–500 ng/ml for EME, 2–500 ng/ml for COC and COET; AEME could only be determined “semi-quantitatively” between 2 and 200 ng/ml according to our chosen acceptance criteria. Suggested dissociation pathways have also been proposed to interpret the obtained spectra.

Dynamic headspace coupled to perevaporation for the analysis of anisoles in wine by gas chromatography–ion-trap tandem mass spectrometry

Dynamic headspace coupled to perevaporation for the analysis of anisoles in wine by gas chromatography–ion-trap tandem mass spectrometry

Dynamic headspace coupled to perevaporation for the analysis of anisoles in wine by gas chromatography–ion-trap tandem mass spectrometry

Off-flavours in wines are mainly due to the presence of 2,4,6-trichloroanisole and other haloanisoles. The purpose of this study was to develop a method based on the coupling of dynamic headspace and perevaporation to GC–MS–MS to attain better analyte sensitivity and selectivity. The approach has been applied to the analysis of 2,6-dichloroanisole, 2,4,6-trichloroanisole and 2,4,6-tribromoanisole in various wines. For these compounds that cause taste and odour problems, the method was linear from the quantification limit to 3 ng for all the analytes with recoveries greater than 80% and satisfactory precision. Detection limits were as low as 2–36 ng l −1.

Analysis of anisoles in wines using pervaporation coupled to gas chromatography–mass spectrometry

Two procedures for the determination of 2,4,6-trichloroanisole, 2,6-dichloroanisole and 2,4,6-tribromoanisole in tainted wines have been developed. Both methods are based on pervaporation (PV) of the analytes and final determination by gas chromatography–ion-trap tandem mass spectrometry (GC–MS). In the Approach A, pervaporation was directly coupled to the GC–MS system (PV–GC–MS/MS) and in Approach B a solid-phase cryogenic trap-thermal desorption (CT–TD) device was connected to the pervaporator (PV–CT–TD–GC–MS/MS). Results show that last coupling present better sensitivity as well as precision. Detection limits (DLs) for 2,4,6-trichloroanisole were estimated to be 25.8 and 4.2 ng l −1 for Approaches A and B, respectively, when 10 ml of sample was analysed. Linear range of the calibration curves ranged from quantification limit to 15 ng for PV–GC–MS/MS and from quantification limit to 2 ng for PV–CT–TD–GC–MS/MS. Due to the low threshold odour concentration of these compounds in wine, Approach B is proposed as a reliable method for analytical quality control of this product.

Use of Gas ChromatographyIontrap Tandem Mass Spectrometry for the Determination of Chemical Markers of Microorganisms in Organic Dust

Gas chromatography/tandem mass spectrometry (GC/MS/MS) using an ion-trap instrument was applied for the determination of ergosterol, muramic acid and 3-hydroxy fatty acids with 10–18 carbon atoms in samples of organic dust. These substances were used as chemical markers to measure fungal biomass, bacterial peptidoglycan and Gram-negative bacterial lipopolysaccharide, respectively. It was found that detection limits attained with GC/MS/MS were comparable to those reached with conventional quadrupole GC/MS analysis using selected-ion monitoring, since all markers, analysed as trimethylsilyl derivatives (the fatty acids after methylation of the carboxyl group), were detectable in the low-picogram range (injected amounts). GC/MS/MS, however, gave results that were easier to interpret owing to the superior detection specificity. Ion trap tandem MS is a convenient technique that should be very useful for the determination of microbial substances in environmental samples, including organic dust.