Automated Solid-phase Microextraction Research Articles

Application of automated solid-phase microextraction to determine haloacetonitriles, haloketones, and chloropicrin in Canadian drinking water

An automated headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS) method was developed to monitor the occurrence of selected haloacetonitriles (HANs), haloketones (HKs), and chloropicrin (CP) in drinking water supplies. The method was rapid with analysis time of 30 min, including extraction and chromatographic run. Chemical ionization (CI) was used to increase the sensitivity of the method for the HKs. SPME fibers with seven different coatings including commercial polyacrylate (PA), carbowax/divinylbenzene (CW/DVB), polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), carboxen/polydimethylsiloxane (CAR/PDMS), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), and a novel custom-made polydimethylsiloxane/divinylbenzene-N-vinylpyrrolidone (PDMS/DVB-NVP) were evaluated. The DVB/CAR/PDMS fiber was found more suitable for the range of the analytes and the novel PDMS/DVB-NVP fiber more efficient for the brominated acetonitriles under the experimental conditions. Method detection limits (MDLs) for the chlorinated acetonitriles and CP varied between 2 and 40 ng/L and for the brominated acetonitriles and HKs between 100 and 180 ng/L. Relative standard deviations (RSD %) of measurements were 4–7%. The method was applied in parallel with a liquid–liquid extraction gas chromatography electron capture detection (LLE-GC-ECD) method (EPA Method 551.1) to the analysis of drinking water samples from eight Canadian water treatment and distribution systems. The results generated by the two methods showed good agreement.

Therapeutic Monitoring of Tranexamic Acid Concentration: High-Throughput Analysis With Solid-Phase Microextraction

The controversy still surrounds the optimal dosing regimen of tranexamic acid (TA), primary antifibrinolytic agent used in high-risk surgeries. This study compares the pharmacokinetics profile obtained from the group of patients undergoing heart surgery with the use of cardiopulmonary bypass (CPB) with the theoretical model currently used as an established dosing regimen of TA in cardiac surgery. After induction of anesthesia, TA was administered intravenously as a bolus (30 mg/kg) infused over 15 minutes. Bolus was followed by an infusion of 16 mg·kg·h TA until the end of surgery (chest closure of the sternotomy wound). Before initiation of CPB, a bolus of 2 mg/kg was given to the pump prime. Blood samples were collected at baseline and at 30-minute time intervals during the surgery and after surgery. Automated solid-phase microextraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used for the determination of TA concentration. Blinded studies on monitoring of TA concentration were performed on 94 samples. Obtained results were compared with a previously described pharmacokinetic model of TA dosing. The average concentration of TA during the use of CPB was 134 mcg/mL with the relative standard deviation 27%. The observed range of TA concentrations was 70-188 mcg/mL showing that individual patients can significantly exceed the recommended levels proposed by the theoretical model. lower limit of quantification of the proposed method was 1 mcg/mL. Intra- and interday accuracy was ±10% and precision was ≤12% at all concentration levels tested. The suitability of automated solid-phase microextraction for high-throughput clinical analysis was established for the first time. The obtained pharmacokinetic profiles showed significant interpatient variation in the concentration of TA during heart surgery with the use of CPB, which confirms the need of the therapeutic monitoring of this antifibrinolytic agent.

Fully automated solid-phase microextraction–fast gas chromatography–mass spectrometry method using a new ionic liquid column for high-throughput analysis of sarcosine and N-ethylglycine in human urine and urinary sediments

A fully automated, non invasive, rapid and high-throughput method for the direct determination of sarcosine and N-ethylglycine in urine and urinary sediments using hexyl chloroformate derivatization followed by direct immersion solid-phase micro extraction and fast gas chromatography–mass spectrometric analysis was developed and validated. The use of a new ionic liquid narrow bore column, as well as the automation and miniaturization of the preparation procedure by a customized configuration of the utilized XYZ robotic system, allowed a friendly use of the GC apparatus achieving a quantitation limit of 0.06 μg L −1 for sarcosine, good repeatability with CV always lower than 7% and reduced analysis times useful for point-of-care testing. The method was then applied for the analysis of 56 samples of urine and urinary sediments in healthy subjects, in those with benign prostatic hypertrophy and in patients with clinically localized prostate cancer. The results obtained showed that the medians of sarcosine/creatinine in urine were 103, 137 and 267 μg g −1 respectively, thus assessing the potential use of sarcosine as urinary biomarker for prostate cancer detection. The highest values of sensitivity (79%) and specificity (87%) were obtained in correspondence of a cut-off value of 179 μg sarcosine (g creatinine) −1, thus by using this cut-off threshold, sarcosine was significantly associated with the presence of cancer ( p < 0.0001). Finally, ROC analyses proved that the discrimination between clinically localized prostate cancer and patients without evidence of tumor is significantly correlated with sarcosine.

Optimization of Modern Analytical SPME and SPDE Methods for Determination of Trans-2-nonenal in Barley, Malt and Beer

Trans-2-nonenal is an aldehyde contributing to an unpleasant off-flavor and odor of rancid butter in stored beer. The automated solid-phase microextraction technique (SPME) coupled with gas chromatography (GC) and solid-phase dynamic extraction (SPDE) coupled with gas chromatography were optimized and introduced to determine trans-2-nonenal in barley, malt and beer. Five types of SPME fibers coated with different stationary phases (100 μm PDMS, 65 μm PDMS/DVB, 85 μm CAR/PDMS, 50/30 μm DVB/CAR/PDMS, 85 μm PA) and two needles (PDMS, PDMS/AC) were compared and tested for their efficiencies in the headspace (HS) SPME and SPDE determination of trans-2-nonenal in barley, malt and beer. The highest extraction efficiency of HS-SPME was achieved with the PDMS/DVB fiber, and addition of 1.5 g of NaCl, extraction time was 20 min at 60 °C. The highest extraction efficiency of HS-SPDE was obtained with the PDMS needle, 15 extraction strokes at 60 °C and addition of 1.5 g of NaCl. Trans-2-nonenal was identified with the method of HS-SPME coupled gas chromatography-mass spectrometry (GC–MS); the samples were analyzed using the HS-SPME-GC-coupled gas chromatography-flame ionization detector (GC-FID) technique.

Improved Measurements of Partition Coefficients for Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDEs) are a class of widely used brominated flame retardants with strong hydrophobicity. Due to their strong affinity for organic matter, accurate measurement of adsorption coefficients for PBDEs using conventional batch methods can be confounded by biases caused by their sorption to dissolved organic carbon (DOC). In this study, sorption isotherms were constructed for BDE-47 and BDE-99 in sediments by using different methods to measure the aqueous phase concentration Cw. Upon centrifugation, Cw measured by automated solid-phase microextraction (Cw-SPME) was consistently smaller than by liquid-liquid extraction (Cw-LLE), suggesting substantial association of PBDEs with DOC. Significant underestimations (1.2-106-fold) of sediment-water partition coefficient Kd occurred when Cw was measured by LLE. The log KDOC values derived from the SPME measurements ranged from 5.10 to 8.02 for eight congeners from BDE-28 to BDE-183, suggesting a strong tendency for PBDEs to complex with DOC. This study showed that PBDE congeners have larger sorption coefficients than would be measured by the conventional method. The high affinity to DOC also means a potential for DOC-facilitated transport, thus enhancing the environmental mobility of PBDEs.

Wound-State Monitoring for Burn Patients Using E-Nose/SPME System

Array-based gas sensors now offer the potential of a robust analytical approach to odor measurement for medical use. We are developing a fast reliable method for detection of microbial infection by monitoring the headspace from the infected wound. In this paper, we present initial results obtained from wound-state monitoring for burn patients using an electronic nose incorporating an automated solid-phase microextraction (SPME) desorption system to enable the system to be used for clinical validation. SPME preconcentration is used for sampling of the headspace air and the response of the sensor module to variable concentrations of volatiles emitted from SPME fiber is evaluated. Gas chromatography-mass spectrometry studies prove that living bacteria, the typical infectious agents in clinical practice, can be distinguished from each other by means of a limited set of key volatile products. Principal component analysis results give the first indication that infected patients may be distinguished from uninfected patients. Microbial laboratory analysis using clinical samples verifies the performance of the system.

Automated solid-phase microextraction and thin-film microextraction for high-throughput analysis of biological fluids and ligand–receptor binding studies

This protocol describes how to perform automated solid-phase microextraction (SPME) and thin-film microextraction (TFME) in a 96-well plate format for high-throughput analysis of drugs, metabolites and any other analytes of interest in biological fluids using liquid chromatography-electrospray tandem mass spectrometry. Sample preparation time required is typically 1 min per sample; hence, the throughput achievable with automated SPME/TFME is comparable with automated 96-well liquid-liquid extraction and solid-phase extraction methods, but greater than most online solid-phase extraction methods. The technique is applicable to complex samples such as whole blood without additional pretreatment. The amount of analyte extracted by SPME/TFME is proportional to the free (unbound) concentration of the analyte; hence, SPME/TFME can be used to determine both total and free concentrations of analytes from a single biofluid sample and to perform automated ligand-receptor binding studies in order to determine binding affinity and/or overall extent of ligand binding to a complex biofluid.

Investigation of the Effect of the Extraction Phase Geometry on the Performance of Automated Solid-Phase Microextraction

A new configuration of C(18) thin film extraction phase designed for high sample throughput has been developed and applied to the analysis of benzodiazepines in spiked urine samples using high performance liquid chromatography coupled with tandem mass spectrometry. The high throughput analysis was achieved with the use of a robotic autosampler which enabled parallel analyte extraction in a 96-well plate format. Factors affecting data reproducibility, extraction kinetics, sample throughput, and reliability of the system were investigated and optimized. The intrawell reproducibility was 4.5-7.3%, while interwell reproducibility was 7.0-11% in urine and PBS samples. The limits of detection and quantitation were 0.05-0.15 ng/mL and 0.2-2.0 ng/mL for all analytes, respectively. By comparison with optimized automated multifiber SPME relying on rod geometry, the C(18) thin films showed higher extraction rates (approximate 2-fold increase) and hence higher sample throughput because of the improved configuration and more effective agitation/mass transfer. In addition, this new configuration provided an extraction phase with greater surface area to volume ratio and greater extraction phase volume, which resulted in approximately 2-fold increase in the extraction capacity for diazepam compared with the extractions with automated multifiber SPME rod geometry. The results of this investigation demonstrated the advantages of using thin films to improve extraction kinetics and sensitivity of automated SPME methods for high performance liquid chromatography.

Analysis of tetramethylene disulfotetramine in foods using solid-phase microextraction–gas chromatography–mass spectrometry

An automated solid-phase microextraction–gas chromatography–mass spectrometry (SPME–GC–MS) method for the determination of tetramethylene disulfotetramine in foods was developed. A comparison of direct immersion (DI) and headspace (HS) extraction techniques using a 70 μm carbowax/divinylbenzene (CW/DVB) fiber is presented. The optimized DI-SPME method provided an aqueous extraction limit of detection (LOD) of 9.0 ng/g while the HS-SPME LOD was 2.7 ng/g. In both SPME modes, recovery was highly matrix dependent and quantification requires standard addition calibrations. Analysis of foods using DI-SPME encountered many obstacles including fiber fouling, low recovery and poor reproducibility. HS-SPME was successfully applied to food analysis with minimal interferences. Standard addition calibration curves for foods gave high linearity ( R 2 > 0.98), reproducibility (RSD < 12%) and sensitivity with LODs ranging from 0.9 to 4.3 ng/g.

Reliable identification of pesticides using linear retention indices as an active tool in gas chromatographic–mass spectrometric analysis

The present research is focused on the current development and employment of a dedicated pesticide mass spectral library, characterized by a double-filter search procedure: the first is based on the degree of spectral similarity and the second on chromatographic retention information (linear retention indices). The highly pure mass spectra contained in the library have been attained by subjecting mixtures of widely used pesticides to comprehensive GC–MS analysis. Linear retention indices for conventional GC–MS analyses were calculated by injecting the same compounds on a single-column GC–MS system. The effectiveness of this approach was verified by analysing a white wine sample spiked with 10 structurally similar pyrethroid compounds, through automated solid-phase microextraction–GC–MS.

Determination of hydroxy metabolites of polycyclic aromatic hydrocarbons by fully automated solid-phase microextraction derivatization and gas chromatography–mass spectrometry

A fully automated sample pretreatment method was developed for the detection of mono and dihydroxy metabolites of polycyclic aromatic hydrocarbons (PAHs) by gas chromatography–mass spectrometry in the selected ion monitoring mode. Direct immersion solid-phase microextraction for the extraction of target compounds and the headspace on-fiber silylation with N, O-bis(trimethylsilyl)trifluoroacetamide were performed automatically by a multipurpose autosampler (MPS2). The operating conditions including extraction time, derivatization time, ionic strength, pH, and incubation temperature were optimized. Calibration responses of nine metabolites of PAHs over a concentration range of 0.1–100 μg L −1 with a correlation coefficient of 0.999 were obtained. The detection limits of the nine metabolites in mini pore water, minimal salts medium and soil extract culture medium were in the range of 0.001–0.013, 0.002–0.024 and 0.002–0.134 μg L −1, respectively, while the respective quantification limits were 0.003–0.044, 0.005–0.081 and 0.008–0.447 μg L −1. The reliability was confirmed by the traditional solid-phase extraction method. The proposed method could be used to analyze the metabolites of PAHs degraded by microorganisms such as algae and to determine the biodegradation pathways of PAHs.

Rapid headspace solid-phase microextraction–gas chromatographic–time-of-flight mass spectrometric method for qualitative profiling of ice wine volatile fraction: I. Method development and optimization

An analytical method for the determination of volatile and semi-volatile compounds representing various chemical groups in ice wines was developed and optimized in the presented study. A combination of the fully automated solid-phase microextraction (SPME) sample preparation technique and gas chromatographic–mass spectrometric (GC–MS) system to perform the final chromatographic separation and identification of the analytes of interest was utilized. A time-of-flight mass spectrometric (TOF-MS) analyzer provided very rapid analysis of this relatively complex matrix. Full spectral information in the range of m/ z 35–450 was collected across the short GC run (less than 5 min). Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) 50/30 μm fiber performed best during the optimization experiments and it was used in the headspace SPME mode to isolate compounds from ice wine samples, consisting of 3 mL wine with 1 g salt addition. After the sample incubation and extraction (both 5 min at 45 °C), analytes were thermally desorbed in the GC injector for 2 min (injector maintained at 260 °C) and transferred into the column. The MS data acquisition rate of 50 spectra/s was selected as optimal. The optimized analytical method did not exceed 20 min per sample, including both the isolation and pre-concentration of the analytes of interest, the final GC–TOF-MS analysis and the fiber bake-out. Both a linear temperature-programmed retention index (LTPRI) method using C 8–C 20 alkanes loaded onto the fiber and a mass spectral library search were employed to identify the target compounds. The repeatability of the developed and optimized HS-SPME-GC–TOF-MS method for ice wine analysis, expressed as relative standard deviation (RSD, %, n = 7), ranged from 3.2 to 9.0%.

Determining Chemical Activity of (Semi)volatile Compounds by Headspace Solid-Phase Microextraction

This research introduces a new analytical methodology for measuring chemical activity of nonpolar (semi)volatile organic compounds in different sample matrices using automated solid-phase microextraction (SPME). The chemical activity of an analyte is known to determine its equilibrium concentration in the SPME fiber coating. On this basis, SPME was utilized for the analytical determination of chemical activity, fugacity, and freely dissolved concentration using these steps: (1) a sample is brought into a vial, (2) the SPME fiber is introduced into the headspace and equilibrated with the sample, (3) the SPME fiber is injected into the GC for thermal desorption and analysis, and (4) the method is calibrated by SPME above partitioning standards in methanol. Model substances were BTEX, naphthalene, and alkanes, which were measured in a variety of sample types: liquid polydimethylsiloxane (PDMS), wood, soil, and nonaqueous phase liquid (NAPL). Variable sample types (i.e., matrices) had no influence on sampling kinetics because diffusion through the headspace was rate limiting for the overall sampling process. Sampling time was 30 min, and relative standard deviations were generally below 5% for homogeneous solutions and somewhat higher for soil and NAPL. This type of activity measurement is fast, reliable, almost solvent free, and applicable for mixed-media sampling.

Application of solid-phase microextraction to in vitro skin permeation experiments: example using diethyl phthalate

The application of automated solid-phase microextraction (SPME) as a sample preparation technique for in vitro studies of skin permeation is described, using diethyl phthalate (DEP) as an example. In vitro diffusion cell experiments and skin–vehicle partition coefficient determinations require quantitative analysis of low-level analytes in aqueous samples. SPME is an ideal candidate for sample preparation for subsequent gas chromatographic analysis, offering numerous advantages over other methods. SPME conditions were optimized and the automated method was found to exhibit adequate sensitivity and good precision (relative standard deviation = 3%). Abdominal skin (dermatomed at 350 μm) from male hairless guinea pigs ( n = 6) was used to measure DEP skin permeation parameters. In vitro methods were employed to determine permeability coefficient ( k p), time lag ( τ) and skin–buffer partition coefficient ( K SB) for 2 mM DEP in HEPES buffered Hanks Balanced Salt Solution. Measurements (mean ± standard deviations) are: k p, 0.021 ± 0.012 cm/h; τ, 0.67 ± 0.18 h; K SB, 4.74 ± 0.68. The skin may be a significant route for the uptake of DEP.

Determination of Volatile Compounds in Wine by Automated Solid-Phase Microextraction and Gas Chromatography

Solid-phase microextraction in headspace mode has been applied to the determination of volatile compounds (3-methyl-1-butyl acetate, 3-methyl-1-butanol, ethyl hexanoate, pentanol, hexanol, linalool, diethyl succinate, α-terpineol, 2-phenylethyl acetate, geraniol, 2-phenylethanol and octanoic acid) in wine samples from the Denominacion de Origen Calificada Rioja using gas chromatography and a flame ionization detector. After the preliminary tests, several parameters were optimized using a Plackett-Burman design to get the most relevant variables. These parameters were: extraction time, desorption time, split ratio, magnetic stirring, type of fibre, type of injection (headspace or direct sampling) and type of salt. Five wine samples were analysed under optimum conditions. Concentrations ranging from 0.0104 mg L−1 for pentanol and 48.9 mg L−1 for 3-methyl-1-butanol were obtained. Linalool, α-terpineol and geraniol were not detected. Limit of detection ranging 0.00150-0.00800 mg L−1 and relative standard deviation ranging 1.1–5.7% were obtained.

Correlations between pulp properties of eucalyptus clones and leaf volatiles using automated solid-phase microextraction.

Analysis of biogenic volatile organic compounds (BVOC) of 14 Eucalyptus clones has been performed using an automated headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography (GC)/ion trap mass spectrometry (ITMS) method. Correlations between pulp properties of Eucalyptus clones and the BVOC of their leaf headspaces were studied. The compounds alpha-terpineol and the sesquiterpene beta-eudesmol were positively correlated with S5, a property related to the hemicelluose content in the pulp. Qualitative results obtained with automated HS-SPME were sufficient to group together the same species and related hybrids through cluster analysis and were confirmed through principal component analysis. A preliminary separation of the essential oils of Eucalyptus dunnii through comprehensive two-dimensional gas chromatography (GC x GC) showed approximately 580 peaks compared to approximately 60 in a typical GC/ITMS first-dimension chromatogram. The potential of HS-SPME coupled to GC x GC to improve the separation of Eucalyptus volatiles and other plant essential oils looks extremely promising for new applications of unsupervised learning methods.

Trace analysis of technical nonylphenol, bisphenol A and 17α-ethinylestradiol in wastewater using solid-phase microextraction and gas chromatography–mass spectrometry

To enable high sample throughput, an automated solid-phase microextraction (SPME) method coupled with GC–MS for the trace analysis of technical nonylphenol, bisphenol A and 17α-ethinylestradiol was developed. The extraction performance of different SPME fibre coatings was examined, with polyacrylate proving most suitable. Although study of the extraction time showed that the analytes have not reached equilibrium after 3 h, as a compromise an extraction time of 1 h was applied in all the experiments with detection limits between 0.04 and 1 μg l −1 for wastewater effluent. The mean reproducibility of the technique is 8% RSD. Carry-over effects are negligible. The linearity of calibration curves ranges over three orders of magnitude. The method was tested for determining the analytes in influents and effluents of constructed wetland plants and in model wastewater used in laboratory experiments.

Quantitation of 2-chlorovinylarsonous acid in human urine by automated solid-phase microextraction–gas chromatography–mass spectrometry

Lewisite [dichloro(2-chlorovinyl)arsine] is a highly toxic chemical warfare agent with vesicant properties. The accidental exposure to lewisite or its intentional use as a chemical terrorism weapon are a public health threat and warrant investigations for the development of analytical methods to detect biomarkers of exposure to lewisite. Under aqueous conditions, lewisite rapidly hydrolyzes to the non-volatile 2-chlorovinylarsonous acid (CVAA). We have developed a sensitive, simple, and automated method for measuring CVAA in human urine. The assay is based on the use of solid-phase microextraction (SPME) and gas chromatography–mass spectrometry (GC–MS) after derivatization of the CVAA with 1,3-propanedithiol (PDT). The volatile CVAA-PDT is adsorbed onto a SPME fiber and analyzed by GC–MS. The assay was validated on human urine samples spiked with CVAA to determine the accuracy, precision, and limit of detection (LOD). The LOD was 7.4 pg in 1 ml of urine.

Examination of the Enantiomeric Distribution of Certain Monoterpene Hydrocarbons in Selected Essential Oils by Automated Solid-Phase Microextraction--Chiral Gas Chromatography--Mass Selective Detection

A viable approach for the determination of sources of essential oils based on automatic injection solid-phase microextraction-chiral-gas chromatography-mass selective detection is demonstrated. With no sample preparation, it is shown that the source of essential oils such as peppermint, spearmint, and rosemary can be easily distinguished. Short fiber exposure times of approximately 6 s to the headspace above submicroliter quantities of the selected oils are all that is required to obtain both the required sensitivity and resolution to afford analyses with excellent reproducibilities (relative standard deviation values consistently less than 5.0%).

Design of an automated analysis system for the determination of organic compounds in continuous air stream using solid-phase microextraction

An automated solid-phase microextraction (SPME) unit coupled to gas chromatography was used to determine organic compounds in air. The target analyte was released from microcapsules into the air at ambient temperature. A fully automated system was designed to facilitate the monitoring of the organic analytes in the continuous air stream. A thin layer of the capsules was prepared by spraying an aqueous solution containing the microcapsules on one side of a glass slide. The slide was exposed to an air stream, which served as a carrier for the analyte vapors. The exposed air was passed through a flow-through cell that was mounted on the autosampler carousel. The SPME assembly, which was fitted with poly(dimethylsiloxane) fiber, was controlled by standard autosampler software. In the dynamic measurement mode, the fiber was inserted in the cell and the analytes partitoned onto the coating. The performance of the sampling device was characterized with respect to mass loading on the fiber, linearity, exposure time and precision. The primary objective of the study was to characterize the release of the pheromone Gossyplure [(Z)-7-(Z,E)-11-hexadecadien-1-ol acetate] from microcapsules. The precision of the SPME method was, in general, less than 7% RSD using 18 repetitive extractions. The method was found to be linear over at least three orders of magnitude. The sampling interval was typically 30 min.