Analysis of phenolic acids as chloroformate derivatives using solid phase microextraction–gas chromatography

A method was developed for the analysis of volatile polar compounds in a water matrix using open cap vials Solid Phase Micro-Extraction (SPME) and Capillary Gas Chromatography (CGC). Both SPME techniques – direct sampling and headspace – were tested. Optimization of experimental conditions – exposure time, desorption time, with headspace SPME in addition the influence of the temperature and ionic strength of the sample solution on compound sorption, and finally GC response – were investigated. The analytes were extracted by directly immersing the 85 μm polyacrylate fiber in the aqueous sample or in the headspace. The linear range of the preconcentration process and the precision were examined. The amount of polar analytes sorbed on the fiber was determined and was found to be concentration dependent; it amounted to 0.014–0.64% in the concentration range of 0.00425–425 ppm studied in aqueous solution for direct sampling SPME and to 0.011–2.76% for solutions of concentration 0.0425–255 ppm for headspace SPME. The limits of determination were ascertained. Headspace SPME was applied to the analysis of real-life samples.

A method based on a solid phase microextraction gas chromatography- mass spectrometry (SPME-GC/MS) was developed for the quantitative determination of chlorpyrifos residues in cherry samples. Three kinds of fiber coatings: PA (polyacrylate, 85µm), PDMS–DVB (polydimethylsiloxane–divinylbenzene 65 mm) and PDMS (polydimethylsiloxane, 100 mm) were compared. Various parameters affecting SPME procedures such as temperature, extraction and desorption times, salinity, stirring rate were investigated. The analytes from all sample extracts were preconcentrated for 30 minutes in the SPME fiber at 60 °C and then the fiber was desorbed by heating at 250 °C for 10 minutes in the gas chromatography injection port. Limits of detection (LOD) and quantitation (LOQ) values were 0.03 µg/L and 0,1 µg/L, respectively. An average recovery range was 93-98% with relative standard deviation (RSD) < 10 %.

The aroma is one of the most appreciated sensorial attributes of fruit and one of the decisive factors in choosing a food. The flavor industry has grown significantly in recent years and the consumer's desire for new essences has given rise to the development of products from non-conventional fruits. The soursop (Annona muricata L.) is an important tropical fruit known to have a pleasant aroma and distinctive flavor. The objective of this work was to capture the volatiles from soursop pulp using solid phase microextraction (SPME) with the fibers 85 μm CAR/PDMS (carboxen/polydimethylsiloxane), 65 μm PDMS/DVB (polydimethylsiloxane/ divinylbenzene) and 50/30 μm DVB/CAR/PDMS (divinylbenzene/carboxen/ polydimethylsiloxane). The separation of volatile compounds was performed by GC-MS equipped with a nonpolar column (DB5-MS 30 m × 0.25 mm × 0,25 μm), and identified by comparing the mass spectra of the compounds of the samples with NIST (National Institute of Standards & Technology) and by comparison of the linear retention index (LRI). A total of 47 volatile compounds were identified with SPME technique, including 26 esters, 9 terpenes, 4 aldehydes, 1 alcohol, 2 aromatic hydrocarbons, 2 alkanes and 3 unidentified. Among the tested fiber which extracted more number of compounds was PDMS/DVB with a total of 39 compounds, and compounds with greater total area were the methyl hexanoate (39.19%), trans-2-methylhexanoate (25.23%), methyl butanoate (15.35%), trans-2-methyl-butenoate (4.41%) and trans-2-methyl octenoate (2.54%).

Sample preparation is important for the isolation and concentration of desired trace components from complex matrices. Sample preparation is the most labor-intensive and error-prone process in analytical methodology, and greatly influences the reliable and accurate determination of analytes. The integration of sample preparation with various analytical instruments is most conveniently achieved by using microextraction techniques and/or microdevices. Solid-phase microextraction (SPME) is both simple and effective, enabling miniaturization, automation and high-throughput performance. Moreover, SPME has reduced analysis times, as well as the costs of solvents and disposal. This review describes current developments and future trends in novel SPME techniques, including fiber SPME, in-tube SPME and related new microextraction techniques. Especially innovative SPME approaches, including multi-well high-throughput sampling, ligand-receptor binding study for pharmacokinetics, direct in vivo sampling, chip-based microfluidic system, and new sampling techniques using intelligent carbon nanotube and temperature-response polymer in pharmaceutical and biomedical analysis are focused items.

A headspace solid-phase microextraction (SPME) method was developed for the determination of secondary compounds from Brazilian sugar cane spirits, or cachaça, by GC-FID. An SPME holder with an 85 microm polyacrylate coating was utilized. The novel method is compared with an optimized method: liquid-liquid extraction (LLE). Both methods showed good linearity, but the repeatability for analyses done with the SPME technique (%RSD = 1.8-3.9) was better than for those done with LLE (%RSD = 10.3-11.7). The concentrations of the analytes obtained in the analysis of 12 cachaça samples with the SPME technique were higher than those obtained with LLE. In the SPME method the extraction wastes are smaller. Cachaça samples were qualitatively analyzed for GC-MS.

Gunshot residue (GSR) is a complex chemical mixture that is created during the discharge of a firearm. Its detection and interpretation play a crucial role in the investigation of firearm incidents. Current GSR analysis is limited to inorganic GSR (IGSR), however, the evidential value could be strengthened by inclusion of organic GSR (OGSR). The present study aims to address this potential by proposing a categorisation system for relevant OGSR compounds and developing a methodology for the collection, extraction and analysis of both organic and inorganic GSR from a single sample. The organic composition of more than 50 propellant powders has been determined and compared against more than 200 propellant compositions reported in the literature. This work has resulted in a three-tier categorisation system for OGSR compounds, which together with the current IGSR classification will provide unequivocal identification of GSR materials with the possibility of discriminating between GSR from different ammunition types. Evaluation of MonoTrap extraction showed that this is an effective pre-concentration technique for the characterisation of propellants. Solid-phase microextraction (SPME), however, was the superior method for the extraction of OGSR compounds from various sampling media, including swabs and stubs. The optimised methodology involves GSR collection using carbon adhesive stubs followed by SPME gas chromatography – mass spectrometry (GC-MS) analysis of OGSR and subsequent scanning electron microscopy – energy-dispersive X-ray spectrometry (SEM-EDX) analysis for IGSR. This protocol has resulted in the detection of both characteristic IGSR and categorised organic compounds, demonstrating the ability to obtain a full chemical profile from a single sample. Detection of both first and second tier organic compounds provides complementary compositional information that could be used to discriminate between samples. Furthermore, this methodology requires no changes to the current sampling and IGSR analysis protocols and addresses the limited storage time of OGSR. Since GC-MS instruments are readily available in most analytical laboratories, implementation of the proposed protocol is feasible.

Porous material-based sorbent coatings in solid-phase microextraction technique: Recent trends and future perspectives

A solid-phase microextraction fiber with carbon nanoparticles as sorbent material prepared by a simple flame-based preparation process

In this study, caged calcium alginate-caged multiwalled carbon nanotubes dispersive microsolid phase extraction was described for the first time for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples prior to gas chromatographic analysis. Fluorene, phenanthrene and fluoranthene were selected as model compounds. The caged calcium alginate-caged multiwalled carbon nanotubes was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and thermal gravimetry analyses. The effective parameters namely desorption solvent, solvent volume, extraction time, desorption time, the mass of adsorbent and sample volume were optimized. Under the optimum extraction conditions, the developed method showed good linearity in the range of 0.5-50 ng mL-1 (R2 ≥ 0.996), low limits of detection and quantification (0.42-0.22 ng mL-1) (0.73-1.38 ng mL-1) respectively, good relative recoveries (71.2-104.2%) and reproducibility (RSD 1.8-12.4%, n = 3) for the studied PAHs in water sample. With high enrichment factor (1,000), short extraction time (<30 min), low amounts of adsorbent (100 mg) and low amounts of solvent (0.1 mol) have proven that the microsolid phase extraction method based on calcium alginate-caged multiwalled carbon nanotubes are environmentally friendly and convenient extraction method to use as an alternative adsorbent in the simultaneous preconcentration of PAHs from environmental water samples.

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.

An approach to solventless sample preparation procedure for pesticides analysis using solid phase microextraction/supercritical fluid extraction technique

Aroma analysis of horticultural produce is an emerging field in which both flavor producing and malodorous compounds are detected from within a complex sample matrix. Qualitative and quantitative information is desired to monitor produce ripeness and provide quality control over processed products such as juices, preserves and canned products. Conventional analysis methods such as purge and trap and gas chromatography–mass spectrometry provide much of this information but are laborious and time consuming. Faster techniques are required when large numbers of samples are being analyzed and when rapid feedback to the produce harvester is required. Solid-phase microextraction (SPME) has recently been shown to significantly reduce the sampling times required by more conventional methods. The use of fast gas chromatographic techniques along with the recently commercialized time-of-flight mass spectrometer has also significantly reduced the separation and analysis times. We have combined SPME with gas chromatography–time-of-flight mass spectrometry as a rapid and quantitative tool for the analysis of flavor volatiles in apples and tomatoes. The sampling and analysis processes provide significant improvements to sample throughput, with analysis times taking only 2–6 minutes. The linear response of this system to butylacetate, ethyl-2-methylbutanoate and hexylacetate ranges from ppb to ppm levels, and the identification of unknown flavor compounds is possible even in the presence of other co-eluting compounds. The SPME technique is able to investigate volatiles changes in apple cuticle and tissues, which open the new possibility for flavor biochemistry research.

Development of a solid-phase microextraction gas chromatography with microelectron-capture detection method for a multiresidue analysis of pesticides in bovine milk

Gas chromatographic determination of 2-hydroxy-4-methoxybenzophenone and octyldimethyl- p-aminobenzoic acid sunscreen agents in swimming pool and bathing waters by solid-phase microextraction

Biomonitoring of persistent organochlorine compounds in blood using the solid phase microextraction technique (SPME) and gas chromatography with electron capture detection (GC-ECD) is described. Polar substances as tri-, tetra- and penta-chlorophenols are analyzed simultaneously with less polar compounds such as hexachlorobenzene (HCB), α-, β-, and γ-hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and its derivatives and with some important congeners of the polychlorinated biphenyls (PCB). No derivatization is needed for the determination of the phenolic compounds. The results show a good reproducibility down to the lower μg/L-region. The method is very fast and of low cost compared to the classic extraction and determination procedures.