Development and validation of a solid-phase microextraction method for the analysis of volatile organic compounds in groundwater samples

A Study of Headspace Solid-Phase Microextraction in the Analysis of 54 Hydrophobic Pollutants in Remote Alpine Lake Waters with an Emphasis on Analyte Recovery and Storage Time

Commercially available headspace solid-phase microextraction (HS-SPME) fibers have been used for years to extract pesticides and polychlorinated biphenyls from aqueous samples at the expected ultratrace levels (picograms per liter or parts per quadrillion) in alpine lakes. Several variables of the HS-SPME technique have been adequately evaluated, including water temperature, pH, salt content, fiber type and coating thickness, length of fiber-sample exposure, and liquid immersion versus headspace exposure; but surprisingly, analyte recovery as a function of analyte concentration and storage time has not been included in previous studies, which can be important for remote sampling sites. Seven hydrophobic chlorinated pollutants were identified in alpine lake water (out of 54 analyzed); but recovery using the common SPME technique was found to be inconsistent as the analyte concentration decreases, and the recovery trend as a function of concentration varies on a compound-to-compound basis that could result in a large underestimation of analyte concentrations in field samples. Of the 54 compounds surveyed, o,p'-dichlorodiphenyltrichloroethane (DDT), p,p'-DDT, p,p'-dichlorodiphenyldichloroethylene (DDE), o,p'-DDE, chlorthal-dimethyl, endosulfan I, γ-hexachlorocyclohexane, heptachlor, and trans-nonachlor were generally measured at concentrations between 1 and 150 pg/L (parts per quadrillion). No study to date has evaluated this commonly used but unstandardized technique for analyte recovery as a function of analyte concentration or storage time of aqueous samples. Environ Toxicol Chem 2023;42:1199-1211. © 2023 SETAC.

Sensitive multiresidue method by HS-SPME/GC-MS for 10 volatile organic compounds in urine matrix: a new tool for biomonitoring studies on children

A HS-SPME method coupled with GC-MS analysis has been developed for simultaneously measuring the concentration of 10 volatile organic compounds (VOCs) (benzene, toluene, ethylbenzene, o-, m-, and p-xylene, methyl tert-butyl ether, ethyl tert-butyl ether, 2-methyl-2-butyl methyl ether, and diisopropyl ether) in urine matrix as a biomonitoring tool for populations at low levels of exposure to such VOCs. These compounds, potentially toxic for human health, are common contaminants of both outdoor and indoor air, as they are released by autovehicular traffic; some of them are also present in environmental tobacco smoke (ETS). Thus, the exposure to these pollutants cannot be neglected and should be assessed. The low limits of detection and quantification (LODs and LOQs <6.5 and 7.5 ng L(-1), respectively) and the high reproducibility (CVs <4 %) make the developed method suited for biomonitoring populations exposed at low levels such as children. Further, the method is cost-effective and low in time-consumption; therefore, it is useful for investigating large populations. It has been applied to children exposed to traffic pollution and/or ETS; the relevant results are reported, and the relevant implications are discussed.

New trends in sample preparation techniques for environmental analysis

Environmental samples include a wide variety of complex matrices, with low concentrations of analytes and presence of several interferences. Sample preparation is a critical step and the main source of uncertainties in the analysis of environmental samples, and it is usually laborious, high cost, time consuming, and polluting. In this context, there is increasing interest in developing faster, cost-effective, and environmentally friendly sample preparation techniques. Recently, new methods have been developed and optimized in order to miniaturize extraction steps, to reduce solvent consumption or become solventless, and to automate systems. This review attempts to present an overview of the fundamentals, procedure, and application of the most recently developed sample preparation techniques for the extraction, cleanup, and concentration of organic pollutants from environmental samples. These techniques include: solid phase microextraction, on-line solid phase extraction, microextraction by packed sorbent, dispersive liquid-liquid microextraction, and QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe).

Fast identification and quantification of BTEX coupling by Raman spectrometry and chemometrics

Monoaromatic hydrocarbons (MAHs) monitoring is of environmental interest since these chemical pollutants are omnipresent.

Sample preparation for the analysis of volatile organic compounds in air and water matrices

This review summarizes literature data from the past 5 years on new developments and/or applications of sample preparation methods for analysis of volatile organic compounds (VOC), mainly in air and water matrices. Novel trends in the optimization and application of well-established airborne VOC enrichment techniques are discussed, like the implementation of advanced cooling systems in cryogenic trapping and miniaturization in adsorptive enrichment techniques. Next, focus is put on current tendencies in integrated sampling-extraction-sample introduction methods such as solid phase microextraction (SPME) and novel in-needle trapping devices. Particular attention is paid to emerging membrane extraction techniques such as membrane inlet mass spectrometry (MIMS) and membrane extraction with a sorbent interface (MESI). For VOC enrichment out of water, recent evolutions in direct aqueous injection (DAI) and liquid-liquid extraction (LLE) are highlighted, with main focus on miniaturized solvent extraction methods such as single drop microextraction (SDME) and liquid phase microextraction (LPME). Next, solvent-free sorptive enrichment receives major attention, with particular interest for innovative techniques such as stir bar sorptive extraction (SBSE) and solid phase dynamic extraction (SPDE). Finally, recent trends in membrane extraction are reviewed. Applications in both immersion and headspace mode are discussed.

Identification and elimination of polysiloxane curing agent interference encountered in the quantification of low-picogram per milliliter methyl tert-butyl ether in blood by solid-phase microextraction headspace analysis

Widespread use of the gasoline additive methyl tert-butyl ether (MTBE) and the subsequent human exposure that follows have led to the need to quantify MTBE in a variety of complex biological matrixes. In this work, we demonstrate our latest MTBE quantification assay for whole blood and uncover previously unidentified contamination sources that prevented routine quantification in the low picogram per milliliter (parts per trillion, ppt) range despite a sensitive and selective analytical approach. The most significant and unexpected sources of contamination were found in reagents and laboratory materials most relevant to sample preparation and quantification. In particular, significant levels of MTBE were identified in sample vial septa that use poly(dimethylsiloxane) (PDMS)-based polymers synthesized with peroxide curing agents having tert-butyl side groups. We propose that MTBE is one of the byproducts of these curing agents, which cross-link PDMS via the methyl side groups. Residual MTBE levels of approximately 20 microg/septa are seen in septa whose formulations use these curing agents. Fortunately, these levels can be significantly reduced (i.e., <0.2 ng/septa) by additional processing. Performance achieved with this sample preparation approach is demonstrated using a mass spectrometry-based method to quantify blood MTBE levels in the low-ppt range.

Determination of volatile oak compounds in wine by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC) coupled to mass spectrometry (MS) method was developed to identify and quantify 14 volatile oak compounds in aged red wines. The most important HS-SPME variables were optimised by experimental design technique in order to improved the extraction process. The selected conditions were: 10 mL of sample in 20 mL sealed vials with addition of 30% of sodium chloride (saturated solution), divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre, 10 min of pre-incubation time, 70 degrees C of temperature and 60 min of extraction time without agitation. The features of the method were established for the studied compounds in terms of linear range, slope and intercept of the calibration graphs, detection and quantification limits and repeatability. For all compounds detection limits were below their threshold levels and repeatability, in terms of relative standard deviation, was good, with values between 3 and 11%. Finally, the method was applied to the analysis of six aged red wines by both internal standard and standard addition calibration methods. The concentrations obtained with both methods were statistically compared.

Direct screening and confirmation of benzene, toluene, ethylbenzene and xylenes in water

A novel, straightforward sample screening method for benzene, toluene, ethylbenzene and xylene isomers (BTEX) in water is proposed. The method is based on the direct coupling of a headspace (HS) sampler with a mass spectrometer by using a chromatographic column heated to 200 degrees C as an interface. Samples are acidified and subjected to the headspace generation process, the resulting volatile fraction being directly introduced into the source of the mass spectrometer. The large number of samples to be analyzed and the wide range of m/z ratios scanned (75-110) suggest the use of chemometric approaches based on pattern recognition techniques (PRT). For sample classification purposes, the detection limit of the method (overall response 4.0 ng/ml BTEX) was selected as the cut-off level. The method proved highly reliable as no false negatives were obtained at the legally established concentration levels. Positive water samples were confirmed by using the same instrumental setup as in the screening method, but by heating the chromatographic column at 40-200 degrees C to separate the analytes.