Sorptive Extraction Thermal Desorption Gas Chromatography Mass Spectrometry Research Articles

Determination of booster biocides in sediments by focused ultrasound-assisted extraction and stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

Booster biocides present in natural waters may be captured by the sediments. Highly sensitive, robust, selective and reliable analytical methods are required to evaluate their presence in the sediments. A focused ultrasound assisted extraction method for the simultaneous determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in marine sediments is proposed. The isolation of the target compounds from 0.5 g of sediment was efficient using 2.5 mL of methanol as solvent, an output amplitude of 50 W, 100% duty cycle and an extraction time of 300 s. The extraction procedure was followed by solid-phase clean-up on non-polar sorbents (Oasis HLB). The compounds were sampled using stir bars (20 mm length, 0.5 mm film thickness) coated with polydimethylsiloxane (PDMS). The stir bars were stirred at 900 rpm for 3 h at room temperature. Desorption was carried out by thermal desorption (TD), and the analytes were separated in the gas chromatography (GC). They were detected by triple quadrupole mass spectrometry (MS/MS) using the multiple reaction monitor (MRM) mode. The detection limits (DLs) of booster biocides were in the range of 0.02 to 2.2 ng g − 1 dry weight. The regression coefficients were higher than 0.999. The average recovery was higher than 86% (R.S.D.: 7–11%). The analytical procedure was applied to determination of the booster biocides in port sediment samples from the southwestern Spain. Sea-Nine 211 was found in one sediment at a level of 2.1 ng g−1. Irgarol was present in all the sediments at concentrations between 2 and 9 ng g−1.

Development of stir-bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry for the analysis of musks in vegetables and amended soils

The aim of this study was to develop a sensitive and environment-friendly method based on stir-bar sorptive extraction (SBSE) followed by thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) to determine 8 synthetic musks (musk ambrette, musk ketone, celestolide, tonalide, galaxolide, phantolide, traseolide, and cashmeran) in vegetables (lettuce, carrot, and pepper) and amended soil samples. In a first step sorptive extraction was studied both in the headspace (HSSE) and in the immerse mode (SBSE). The best results were obtained in the immersion mode which was further studied. The influence of the main factors: methanol (20%) and NaCl addition (0%), extraction temperature (40°C) and time (180min), extraction solvent volume (9mL) and stirring rate (600rpm) on the efficiency of SBSE was evaluated by means of experimental designs. In the case of TD, desorption time (10min), desorption temperature (300°C), cryo-focusing temperature (−30°C), vent flow (75mL/min) and vent pressure (7.2psi) were studied using both a fractioned factorial design and a central composite design (CCD). The method was validated in terms of apparent recoveries (AR%), method detection limits (MDLs) and precision at two different concentration levels. Although quantification using instrumental calibration rendered odd results in most of the cases, satisfactory recoveries (74–126%) were obtained in the case of matrix-matched calibration approach for all of the analytes and matrices studied at the two concentration levels evaluated. MDLs in the range of 0.01–0.8ng/g and 0.01–1.1ng/g were obtained for vegetables and amended soil samples, respectively. RSD values within 1–23% were obtained for all the analytes and matrices. Finally, the method was applied to the determination of musks in vegetable and amended soil samples.

Determination of selenomethionine and seleno-methyl-selenocysteine in biota by ultrasonic-assisted enzymatic digestion and multi-shot stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A method based on stir bar sorptive extraction (SBSE) and thermal desorption (TD)–gas chromatography–mass spectrometry (GC–MS) has been optimized for the determination of seleno-methyl-selenocysteine (SeMetSeCys) and selenomethionine (SeMet) in biota samples. Aliquots of freeze-dried tissue, a mixture of protease XIV-lipase and water were sonicated for 2min. After extraction, the extract was separated by centrifugation and subjected to derivatization and SBSE–TD–GC–MS. The parameters affecting derivatization, absorption and desorption steps were investigated. The optimized conditions consist of a derivatization with 40μL of ethyl chloroformate (ECF) in 400μL of a water:ethanol:pyridine (60:32:8) mixture, followed by dilution to 1.5mL of 70g NaClL−1 in water at neutral pH and an extraction step using 10mm×1mm PDMS stir bar, stirring at 800rpm for 20min at room temperature (23±1°C). Three stir bars were used for the extraction of three different aliquots of the same sample and then placed in a single glass desorption liner and simultaneously desorbed for GC–MS analysis. The desorption step required the following conditions: 300°C (desorption temperature), 6min (desorption time), 50mLmin−1 (vent flow) and −5°C (cryotrapping temperature). The method provided precise (8.1%) and accurate results in the mgSekg−1 range (using the selected-ion monitoring-SIM mode) against certified reference material SELM-1 yeast, with recoveries higher than 80% for spiked algae and clams samples.

An Improved Method for Determination of Polychlorinated Biphenyls and Polybrominated Diphenyl Ethers in Sediment by Ultrasonic Solvent Extraction Followed by Stir Bar Sorptive Extraction Coupled to TD–GC–MS

An improved simple, fast and miniaturized method for the determination of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in freshwater sediment using ultrasonic solvent extraction followed by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry (USE-SBSE/TD–GC–MS) is presented. The sediment sample (0.2 g) is extracted with methanol (1:1.2, 2:1.0 mL) in an ultrasonic bath (two 5-min extraction cycles). The combined extracts are made up to 5 mL with water, and from the resulting solution, the analytes are preconcentrated on a stir bar coated with polydimethylsiloxane during 1 h of stirring. The loaded sorptive stir bar is then thermally desorbed and online analysed by GC–MS. For the analytes in river sediment, a linear dynamic range of 0.5–50 ng g−1 was established and limits of detection in sub nanogram-per-gram level were achieved. Recoveries and repeatability were obtained in the ranges 62.8–91.5 % and 3.6–15.0 %, respectively. The method accuracy was confirmed by the analysis of PCBs and PBDEs in a certified reference material. The main improvement in comparison with similar published methods is in shortening the sample handling time and the method miniaturization.

Determination of five booster biocides in seawater by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

Stir bar sorptive extraction (SBSE) and thermal desorption (TD)–gas chromatography–mass spectrometry (GC–MS) have been optimized for the determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in seawater samples. The parameters affecting the desorption and absorption steps were investigated using 10mL seawater samples. The optimised conditions consisted of an addition of 0.2gmL−1 KCl to the sample, which was extracted with 10mm length, 0.5mm film thickness stir bars coated with polydimethylsiloxane (PDMS), and stirred at 900rpm for 90min at room temperature (25°C) in a vial. Desorption was carried out at 280°C for 5min under 50mLmin−1 of helium flow in the splitless mode while maintaining a cryotrapping temperature of 20°C in the programmed-temperature vaporization (PTV) injector of the GC–MS system. Finally, the PTV injector was ramped to a temperature of 280°C and the analytes were separated in the GC and detected by MS using the selected-ion monitoring (SIM) mode. The detection limits of booster biocides were found to be in the range of 0.005–0.9μgL−1. The regression coefficients were higher than 0.999 for all analytes. The average recovery was higher than 72% (R.S.D.: 7–15%). All these figures of merit were established running samples in triplicate. This simple, accurate, sensitive and selective analytical method may be used for the determination of trace amounts of booster biocides in water samples from marinas.

Development of a screening method for the analysis of organic pollutants in water using dual stir bar sorptive extraction-thermal desorption-gas chromatography–mass spectrometry

The development of a method for screening of organic compounds with a wide range of physico-chemical properties in water, based on dual stir bar sorptive extraction coupled with thermal desorption and gas chromatography–mass spectrometry (dual SBSE-TD-GC–MS) is described. The investigated water sample is divided into two aliquots and extracted with stir bar sorptive extraction at two different conditions: using addition of methanol or sodium chloride, respectively. Following extraction, the two stir bars are inserted into the same glass thermal desorption liner and are simultaneously desorbed and analysed by GC–MS. The method optimisation was performed using 45 environmentally harmful substances with different volatilities (boiling point from 193 to 495°C), polarity (logKow from 2.17 to 8.54) and acido-basic properties. The majority of model compounds was selected from the EU list of priority substances in the field of water policy and from the US EPA method 625, respectively. Optimisation was performed for extraction parameters (sample volume, extraction time, stirring rate, addition of modifiers) as well as for the thermal desorption conditions (desorption flow, desorption time, cryofocusing temperature). Performance characteristics (recovery, repeatability, carryover, linearity, limits of detection and quantification) were determined for the optimised method. An example of analysis of a contaminated groundwater sample is presented.

Overall calibration procedure via a statistically based matrix-comprehensive approach in the stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry analysis of pesticide residues in fruit-based soft drinks

Stir bar sorptive extraction (SBSE)–thermal desorption (TD) procedure combined with gas chromatography mass spectrometry (GC–MS) and the statistical variance component model (VCM) is applied to the determination of semi-volatile compounds including organochlorine and organophosphorus pesticides in various synthetic and real fruit-based soft drink matrices. When the matrix effects are corrected using isotopically labelled or non labelled internal standard, but matrix/calibration run-induced deviations are still present in the measurements, the adoption of a variance component model (VCM) in the quantitative analysis of various matrices via an overall calibration curve is successful. The method produces an overall calibration straight line for any analyte accounting for the uncertainty due to all the sources of uncertainty, namely matrix-induced deviations, calibration runs performed at different times, measurement errors. Small increases in the detection limits and in uncertainty in the concentration values obtained in the inverse regression face favourably the decrease in times and costs for routine analyses.

Stir bar sorptive extraction-thermal desorption-gas chromatography–mass spectrometry: An effective tool for determining persistent organic pollutants and nonylphenol in coastal waters in compliance with existing Directives

A multi-residual method based on stir bar sorptive extraction coupled with thermal desorption-gas chromatography–mass spectrometry (SBSE-TD-GC–MS) has been developed to measure 49 organic pollutants (organochlorine pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated diphenyl ethers and nonylphenol) in seawater. Using 100ml of water, the method exhibited good linearity, with recoveries between 86% and 118% and relative standard deviation between 2% and 24% for almost all compounds. The method was applied to determine target contaminants in Catalonian seawater, including coastal areas, ports and desalination plant feed water. Overall individual compound levels oscillated between 0.16 and 597ngl−1; PAHs and nonylpenol were the compounds found at the highest concentrations. The method provided LODs between 0.011 and 2.5ngl−1, lower than the Environmental Quality Standards (EQS) fixed by Directive 2008/105/EC. In compliance with the directive, this method can be used as a tool to survey target compounds and is aimed at protecting coastal ecosystems from chemical pollution.

Multi-residue off-flavour profiling in wine using stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A multi-residue method (MRM) for the detection and quantification of eight compounds responsible for off-flavours in wine using stir bar sorptive extraction (SBSE) followed by thermal desorption (TD) and gas chromatography–mass spectrometry (GC–MS) analysis is presented. The extraction and desorption conditions were optimised in order to get the best compromise for the simultaneous analysis of the eight target solutes, belonging to different chemical classes. The analytical conditions enable the quantification of the solutes below their respective organoleptic perception thresholds in wine. The method displayed good linearity over the concentration ranges explored in wine as well as excellent repeatability (RSD below 6%) and good reproducibility (RSD below 24%). The developed methodology was applied to the analysis of several wines and showed good agreement with the results collected with headspace solid-phase microextraction (HS-SPME) or liquid–liquid extraction (LLE) followed by GC–MS or electron capture detection (ECD). Good correlation was also found between the analytical and sensory results.

Optimization and validation of headspace sorptive extraction for the analysis of volatile compounds in wine vinegars

Quantification of aroma compounds in wine vinegars is challenging due to the complexity of the matrix and the low concentrations expected. A method for the determination of volatile compounds in wine vinegars employing headspace sorptive extraction–thermal desorption–gas chromatography–mass spectrometry (HSSE–TD–GC–MS) was developed. A central composite design was used to optimize the sampling condition. The proposed method was successfully validated and low detection and quantification limits was obtained. The application of the proposed methodology allows the determination of 53 compounds in different wine vinegars (red, Sherry). Five of them have been detected in wine vinegars for the first time.

Simultaneous speciation of methylmercury and butyltin species in environmental samples by headspace-stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

In this work, making use of experimental designs, headspace-stir bar sorptive extraction (HS-SBSE) followed by thermal desorption (TD) coupled to a gas chromatography–mass spectrometry (GC–MS) for the simultaneous determination of mercury and tin organometallic compounds present in surface water, sediment and biological tissue was optimized. All solid samples require a previous extraction typically done with diluted HCl or KOH/methanol solutions, and the derivatization, in all the cases, of the organometallic compounds with NaBEt 4. As a consequence, the preconcentration step was carried out in a 0.1 mol L −1 HOAc/NaOAc buffer solution, with 0.1% (m/v) of NaBEt 4, without the addition of NaCl as a salting out reagent, and with the stir bar (20 mm × 1 mm) located in the headspace (HS). In addition, the desorption step required the following conditions: 250 °C (desorption temperature), 15 min (desorption time), 14.1 psi (∼97.2 kPa) (vent pressure) and 75 mL min −1 (vent flow). Finally, to assure the extraction of all the analytes under equilibrium, 5 h are required. Inorganic mercury (Hg 2+) and tripropyltin (TPrT) were used as internal standards to correct for variations in the extraction, derivatization and detection steps. The resulting method provides precise (4–17%) and accurate (against four certified reference materials) results in the ng L −1 and pg g −1 range concentrations with recoveries within 80–120% for water samples. The proposed methodology is currently applied in the speciation analysis of specimens obtained in different estuarine sites of the Basque Coast.

Simultaneous determination of pesticides, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in seawater and interstitial marine water samples, using stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A method for the simultaneous determination of semi-volatile organic contaminants (polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine and organophosphorus pesticides) in marine samples has been developed, for the first time, using the stir bar sorptive extraction technique (SBSE) and thermal desorption coupled to capillary gas chromatography–mass spectrometry (SBSE-TD-GC–MS). Polydimethyl siloxane (PDMS) was used for the extraction of the selected analytes and two procedures have been optimised and validated, one for seawater samples (100 mL) and another for interstitial water samples (10 mL), using PDMS stir bars of 20 mm and 10 mm size, respectively. The extraction and analytical conditions, such as extraction time, matrix effects, sample volume and desorption time, were optimised. The proposed methods are sensitive, simple and show good linearity and detection limits lower than 1 ng L −1 with seawater and lower than 10 ng L −1 with interstitial marine water for the majority of compounds tested. Repeatability and reproducibility, expressed as relative standard deviation, have values lower than 20% for the majority of analytes considered. The recoveries for both sample volume procedures are higher than 60 and 70% for 10 and 100 mL, respectively, except for the more apolar (some PAHs and PCBs) and the more polar (some triazines) analytes which present lower values. The present SBSE/GC/MS method was applied for the analysis of trace organic contaminants in seawater and interstitial water samples from Cadiz Bay (SW of Spain). Terbutylazine, DDX and some PAHs were found at several seawater sampling points at ng L −1 levels, and some PAHs in interstitial water too.

Optimization of a novel method for the organic chemical characterization of atmospheric aerosols based on microwave-assisted extraction combined with stir bar sorptive extraction

A practical analytical methodology based on coupling microwave-assisted extraction–stir bar sorptive extraction–thermal desorption-gas chromatography–mass spectrometry (MAE–SBSE–TD–GC–MS) was developed and validated for the characterization of several SVOC in atmospheric particulate matter (PM). The high enrichment capacity of SBSE makes it a powerful tool for improving detection limits and MAE has been useful for overcoming the long extraction times and high volumes of extraction solvent used in traditional methodologies. Relative to Soxhlet extraction followed by GC–MS analysis (EPA Methods 3540 and 8270C), the MAE–SBSE–TD–GC–MS methodology resulted with approximately 10 4 times better detection limits. Detection limits ranged from 0.3 to 8.3 pg m −3 for pp′-DDD and decachlorobyphenyl, respectively in PM2.5, 24 m 3 air sample. The performance of the optimized methodology gave good precisions, with R.S.D. less than 30% for most of the standards, and linearity within the range tested of 0.1–15 μg L −1. Analysis of real PM samples resulted in the identification of compounds in the ng L −1 range.

Analysis of nine polybrominated diphenyl ethers in water samples by means of stir bar sorptive extraction-thermal desorption-gas chromatography–mass spectrometry

An optimised method using stir bar sorptive extraction (SBSE) for the determination of nine bromodiphenil ether (Lake Michigan mix) from water samples was developed. Recoveries near to 100% were found by using 20 mm × 0.5 mm (length × film thickness) PDMS commercial stir bars with 100 mL spiked water samples and 20% methanol addition and an extraction period of 25 h. Method sensitivity, linearity, repeatability and reproducibility have been also studied. Detection limits between 0.4 and 9.4 ng/L were calculated for the combination of SBSE and thermal desorption-GC–MS. The procedure was applied a real sample, a surface water contaminated by the effluents, and the results were compared with a classical liquid–liquid extraction method.

Analysis of 35 priority semivolatile compounds in water by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry: Part II: Method validation

A multiresidue method for the determination of 35 organic micropollutants, pesticides, and polycyclic aromatic hydrocarbons (PAHs) in water using stir bar sorptive extraction (SBSE) and thermal desorption coupled to capillary gas chromatography–mass spectrometry (SBSE–TD–GC–MS) has been validated. Method sensitivity, linearity, repeatability and reproducibility, accuracy, matrix effects, and overall uncertainties have been studied for method validation according to the international norm ISO/IEC 17025:1999. The quantification limits ranged from 0.1 to 36 ng/L working in the MS full scan mode. Correlation coefficients of the calibration curves from 20 to 600 ng/L were higher than 0.990 for all the compounds. To validate matrix effects for tap water, ground water and surface water, repeatability, reproducibility, accuracy and overall uncertainty were calculated for the three matrices at 50 and 500 ng/L levels. The accuracy of the method was also evaluated by participating in a proficiency interlaboratory test with real samples.

Dual derivatization–stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry for determination of 17β-estradiol in water sample

A novel method for the trace analysis of 17β-estradiol (E2) in river water sample was developed, which involved stir bar sorptive extraction (SBSE) with in situ acylation (first derivatization) and thermal desorption (TD) with quartz wool assisted (QWA) in tube silylation (second derivatization), followed by gas chromatography–mass spectrometry (GC–MS), and is called the “dual derivatization method.” The optimum conditions for SBSE with in situ acylation, such as the volume of acetic acid anhydride and the extraction time, were investigated. In addition, the optimum conditions for TD with QWA in tube silylation, such as the volume of N, O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and the TD temperature and hold time, were investigated as well. The detection limit (S/N = 3) and the quantitation limit (S/N > 10) of E2 in the river water sample were 0.5 and 2 pg ml −1 (ppt), respectively, by the dual derivatization method. In addition, the detection limit was 0.1 pg ml −1 by using dual derivatization method with multi-shot mode. The calibration curve for E2 was linear in the range of 0.002–10 ng ml −1 with correlation coefficients >0.999. The average recoveries of E2 ( n = 6) at the concentrations of 0.05 and 1.0 ng ml −1 from the river water sample were 93.1 (RSD: 1.4%) and 98.4% (RSD: 0.8%), respectively, with correction using the added surrogate standard, 17β-estradiol- 13C 4. This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of E2 in water samples.

Determination of phenols in lake and ground water samples by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A simple and inexpensive method for sorptive extraction of phenols from water samples is presented. A polydimethyl siloxane (PDMS) stir bar (Twister) is used as an extraction medium for derivatized phenols, which is thermally desorbed and analyzed by gas chromatography–mass spectrometry (GC–MS). Its performance was illustrated and evaluated for the enrichment of μg l −1 to ng l −1 of phenol and selected chlorophenols in water samples. The method showed good linearity, recoveries and blank levels, as well as advantages such as sensitivity, simplicity, low cost and high feasibility, being successfully applied for the analysis of phenolic compounds in natural water samples.

A rapid method of diagnosing pulmonary tuberculosis using stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A fast method for detection of tuberculostearic acid (TBSA) in sputum samples is described. The samples, obtained from patients with known or suspected pulmonary tuberculosis, were decontaminated and concentrated before being analyzed by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry (SBSE–TD–GC–MS). Prior to extraction, the mycobacterial lipids were hydrolyzed and then derivatized with ethyl chloroformate to increase the sorption of the compounds by the polydimethylsiloxane (PDMS) stir bar coating. The limit of detection (LOD) is 0.2 ng ml −1. Four sputum samples that were classified by direct microscopy as smear-positive or negative were analyzed by GC–MS. TBSA was detected at concentrations ranging from 0.47 to 2.3 ng ml −1. The method is sufficiently sensitive to detect TBSA directly in clinical samples without the need to culture the organisms.

Analysis of 35 priority semivolatile compounds in water by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry: I. Method optimisation

A multiresidue method for the determination of 35 organic micropollutants (pesticides and polycyclic aromatic hydrocarbons) in water has been optimised using stir bar sorptive extraction (SBSE) and thermal desorption coupled to capillary gas chromatography–mass spectrometry (GC–MS). In the present work, the different parameters affecting the extraction of the analytes from the water samples to the PDMS-coated stir bars and optimisation of conditions affecting thermal desorption are investigated. The optimised conditions consist of a 100-ml water sample with 20% NaCl addition extracted with 20 mm length×0.5 mm film thickness stir bars at 900 rpm during 14 h at ambient temperature. Desorption is carried out at 280 °C during 6 min under a helium flow of 75 ml/min in the splitless mode while maintaining a cryofocusing temperature of 20 °C in the programmed-temperature vaporisation (PTV) injector of the GC–MS system. Finally, the PTV injector is ramped to a temperature of 280 °C and the analytes are separated in the GC and detected by MS using full scan mode ( m/ z 60–400). Under the described conditions, the good repeatability, high analyte recoveries and robustness, make SBSE a powerful tool for routine quality control analysis of the selected semivolatile compounds in water samples.

Automated sorptive extraction-thermal desorption-gas chromatography-mass spectrometry analysis: Determination of phenols in water samples

A recently developed method for the automated analysis of organic micropollutants in water samples was evaluated for the determination of phenols. Several phenols were selected from the priority pollutant lists to represent the entire range of these pollutants. The phenols are derivatized off-line with acetic anhydride, which is added directly to the water sample. After derivatization is complete, the sample is transferred to the analytical system where automated . sample processing takes place. The sample 10 mL is loaded onto a cartridge packed with polydimethylsiloxane particles, which extract the analytes from the water. After sample loading, the cartridge is dried with nitrogen to eliminate water and derivatization agent. The cartridge is then transferred to the analytical system in which thermal desorption and chromatographic analysis take place. Using mass spectrometric detection in the selected ion monitoring mode, detection limits are on the order of 1) 5n grL. Q 1999 John Wiley & Sons, Inc. J Micro Sep 11: 471)474, 1999