Solid-phase Microextraction In Combination Research Articles

Determination of Microcystins in Water Using Integrated Solid-Phase Microextraction with Microbore High-Performance Liquid Chromatography--Electrospray Quadruple Time-of-Flight Mass Spectrometry

The development of a technique combining solid-phase microextraction (SPME) with microbore high-performance liquid chromatography (micro-HPLC)-tandem quadrupole time-of-flight (QTOF) mass spectrometry (MS) for determination of dissolved microcystins in water is reported. Several important parameters affecting the efficiency of SPME extraction of microcystins are investigated. A microbore C18 column HPLC coupled with tandem QTOF-MS with information-dependent acquisition (IDA) is developed to effectively analyze microcystins in microliter volumes of SPME extracts. The micro-HPLC-QTOF-MS with IDA technique provides comprehensive information, including a survey chromatogram (total ion chromatogram), full scan mass spectrum, and product ion scan mass spectra at different collision energies for individual analytes, which allows for both identification and quantitation in the same run. Linear calibration curves of microcystin standard [microcystin (MC)-arginine (R)R] 1-100 microg/L and of microcystin standard [MC-leucine (L)R] 1-250 microg/L are obtained with a correlation coefficient of 0.996. The combination of SPME with HPLC-QTOF-MS and IDA offers limits of detection of 0.6 pg for MC-RR and 1.6 pg for MC-LR. Analysis of spiked lake-water samples shows a recovery of > 86% for MC-RR and > 70% for MC-LR. This technique requires small sample volumes, minimizes the use of organic solvents, and provides sensitive and information-rich analysis of unknown samples.

Method optimization by solid-phase microextraction in combination with gas chromatography with mass spectrometry for analysis of beer volatile fraction

A simple and sensitive method for the analysis of beer volatile compounds was optimised using headspace solid-phase microextraction (SPME) and gas chromatography with mass detection. Headspace SPME using a 75 μm Carboxen-polydimethylsiloxane (CAR-PDMS) fiber provided effective sample enrichment and enabled extraction of a wide variety of compounds. The reproducibility depended on the compounds, with a mean value of 1.4% for alcohols, 3.3% for ethers, 6.7% for aldehydes, 3.4% for acids, 1.7% for aromatic compounds, 2.4% for esters, 7.4% for hydrocarbons, 1.8% for alicyclic compounds, and 3.4% for heterocyclic compounds. The optimised methodology can be used to compare volatile profile from different types of beers and eventually to study the evolution of a particular beer during aging.

Comparison of three different solid-phase microextraction fibres for analysis of essential oils in yacon ( Smallanthus sonchifolius) leaves

A headspace solid-phase microextraction (HS-SPME) procedure based on three commercialised fibers (100 μm polydimethylsiloxane, 65 μm polydimethylsiloxane–divinylbenzene and 50/30 μm divinylbenzene–Carboxen–polydimethylsiloxane) is presented for the determination of a selected essential oils in dried leaves of yacon ( Smallanthus sonchifolius). The extraction performances of these compounds were compared using fibers with one, two and three coatings. The optimal experimental procedures for the adsorption and desorption of target compounds were determined. Significant parameters affecting sorption process such as sample weight, sorption and desorption time and temperature were optimised and discussed. Finally, the optimised procedures were applied successfully for the determination of these compounds in various yacon species. The relative concentration factors of three characteristic components of yacon were measured for relative evaluation of the fiber efficiency. Main essential oils were isolated from dried yacon leaves by appropriate solid-phase microextraction fiber and semi-quantitative analysis of the target volatiles was conducted by gas chromatography–flame ionisation detection (GC–FID) using a capillary column. Three compounds—β-pinene, caryophylene and γ-cadinene were found as the predominant essential oils. Its relative content was important for specification of yacon varieties. Solid-phase microextraction in combination with gas chromatography enabled a rapid and simple determination of relative content of essential oils in yacon.

Gas Chromatographic Determination of Extractable Compounds Composition and Emission Rate of Volatile Terpenes from Larch Needle Litter

A combination of solid-phase microextraction (SPME) and gas chromatography can be successfully used both for establishing the qualitative composition of volatile organic compounds (VOC) emitted by leaf litter and for determining their emission rates. Taking as an example European larch litter, it is shown that “dead” plant material contains considerable amounts of volatile components as well as non-volatile compounds that can be VOC precursors formed as a result of enzymatic reactions. It is proposed to include the determination of extractable compounds into the methodology of studying litter as a source of atmospheric VOC. Some data on litter mass are reported and it is concluded that this data may be included into special models for emission evaluation. In this work the distribution coefficients of monoterpene hydrocarbons between the gas phase and polydimethylsiloxane fiber coating necessary for quantitative determinations in SPME were estimated.

A Review on Solid Phase Micro Extraction—High Performance Liquid Chromatography (SPME-HPLC) Analysis of Pesticides

Pesticides are an important and diverse environmental and agricultural species. Their determination in formulations, in feed and food, and in complex environmental matrices (e.g., water, soil, sludge, sediments, etc.) often requires separation methods capable of high efficiency, unique selectivity, and high sensitivity. Because pesticides (organophosporus, organochlorine, carbamate, dithiocarbamate, etc.) are carcinogenic, they are problematic for humans in the course of the food chain. Residual analyses have been performed to find out the concentration and type of pesticides and their metabolites left in food at the time of consumption. This ultimately helps in production of better and human-friendly pesticides. A new and effective sampling technique, Solid-Phase microextraction (SPME), was developed in 1990 using a fused silica fiber coated on the outside with appropriate stationary phase in which analyte in the sample is directly extracted to the fibber coating. Two types of fiber techniques can be used to extract analytes: Headspace (HS-SPME), where the fiber is exposed to the vapor phase above a gas, and direct immersion (DI-SPME), where the fiber is directly immersed in the samples. More advanced in-tube SPME recently has been developed, which uses open tubular fused-silica capillary column instead of SPME fiber. SPME in combination with HPLC, GC, GC-MS, LC-MS is getting a wide acceptability as an analytical technique. These have great advantages over the classical sampling techniques, which are time consuming and require larger samples and solvents. This review discusses the various advantages and disadvantages of the SPME for the extraction of the pesticides and their analysis by HPLC.

Analysis of Laminated Documents Using Solid-Phase Microextraction

To evaluate the condition of a laminated document, it is helpful to identify the plasticizers present in the cellulose diacetate lamination film. Plasticizers degrade more readily than the polymer, and some are less stable than others. Solid-phase microextraction in combination with gas chromatography—mass spectroscopy analysis is a simple, nondestructive, and sensitive technique for studying plasticizers and other additives in laminated documents. In this project, five types of solid-phase microextraction fibers were used to study films that contained various combinations of plasticizers. Laminated documents related to the Louisiana Purchase were also studied. Plasticizers were easily identified, as well as the possible degradation products phthalic anhydride and phenol. Various types of films were readily distinguished. With further study it may be possible to better understand the deterioration process by relating the original composition of the cellulose diacetate film to the present condition of a laminated document.

Improving headspace-solid-phase microextraction of 3-isobutyl-2-methoxypyrazine by experimental design with regard to stable isotope dilution gas chromatography?mass spectrometric analysis of wine

To solve problems of sensitivity, repeatability and multi-step extraction related to 3-isobutyl-2-methoxypyrazine (IBMP) determination in wines, a simple method based on the novel combination of solid-phase microextraction and stable isotope dilution assay is presented. Among the parameters that affect this type of extraction, five of them have been optimised since the other parameters have common values or do not require optimisation (e.g. addition of sodium chloride at saturated concentration) and so were fixed. Vial volume, sample volume/vial volume ratio, pH, adsorption time and temperature have been optimised by means of two experimental designs. After extraction, quantification was performed by stable isotope dilution with gas chromatography-tandem mass spectrometry ([2H2]-IBMP as internal standard). The final procedure allowed quantification far below IBMP’s sensory threshold (1 ng l−1 versus 15 ng l−1) with a 4% standard deviation. This method has been applied to experimental Fer servadou wines. Comparison of IBMP contents confirmed the efficiency of some viticultural and enological techniques on the herbaceous flavour decrease, such as prior fermentation maceration at high temperature (70 °C) and the use of a reflective carpet on viticultural soil.

Improving headspace-solid-phase microextraction of 3-isobutyl-2-methoxypyrazine by experimental design with regard to stable isotope dilution gas chromatography–mass spectrometric analysis of wine

To solve problems of sensitivity, repeatability and multi-step extraction related to 3-isobutyl-2-methoxypyrazine (IBMP) determination in wines, a simple method based on the novel combination of solid-phase microextraction and stable isotope dilution assay is presented. Among the parameters that affect this type of extraction, five of them have been optimised since the other parameters have common values or do not require optimisation (e.g. addition of sodium chloride at saturated concentration) and so were fixed. Vial volume, sample volume/vial volume ratio, pH, adsorption time and temperature have been optimised by means of two experimental designs. After extraction, quantification was performed by stable isotope dilution with gas chromatography-tandem mass spectrometry ([ 2 H 2 ]-IBMP as internal standard). The final procedure allowed quantification far below IBMP’s sensory threshold (1 ng l −1 versus 15 ng l −1) with a 4% standard deviation. This method has been applied to experimental Fer servadou wines. Comparison of IBMP contents confirmed the efficiency of some viticultural and enological techniques on the herbaceous flavour decrease, such as prior fermentation maceration at high temperature (70 °C) and the use of a reflective carpet on viticultural soil.

Quantitative determination of formaldehyde in cosmetics using a combined solid-phase microextraction–isotope dilution mass spectrometry method

Solid-phase microextraction (SPME) in conjunction with isotope dilution mass spectrometry (ID-MS) was employed for the analysis of formaldehyde in cosmetic products. The formaldehyde is derivatized in situ with pentafluorophenyl hydrazine. The formed hydrazone is adsorbed over a poly(dimethylsiloxane)–divinylbenzene-coated fiber and analyzed using gas chromatography–mass spectrometry. The adsorption–time profiles and salting effect were studied. The quantitation was performed by using a stable isotope labeled analogue as an internal standard. The precision, recovery and detection limits were determined with spiked samples. The relative standard deviations from different spiked cosmetic samples were all less than 10% and the recoveries were between 89.00 and 101.23%. The limit of detection was of 0.39 μg/l. Compared with other techniques, the study shown here provides a simple, fast and reliable method for the analysis of formaldehyde in cosmetic products.

Potential of SPME-GC and chemometrics to detect adulteration of soft fruit purées.

The potential of combining solid-phase microextraction (SPME) with gas chromatography and chemometric data analysis to differentiate between pure strawberry samples (Fragraria ananassa) and strawberry samples adulterated with 10, 40, and 70% (v/v) apple purée was investigated. The method involved the extraction of aroma volatiles from the headspace of the purée samples using a SPME fiber followed by GC analysis with flame ionization detection. The principal component analysis (PCA) data matrix consisted of the relative percent peak areas of 37 compounds deemed to be significant in the differentiation of the samples on the basis of adulteration. The PCA results clearly showed that differentiation of the adulterated and unadulterated samples was possible, particularly at the higher levels of adulteration. Partial least-squares regression (PLSR) using a dummy set of Y variables (set to 0 for unadulterated and 1 for adulterated samples) resulted in clear discrimination between unadulterated purées and those containing 40 and 70% (v/v) apple. PLSR using a second set of Y variables, consisting of the actual level of adulteration, enabled quantification of apple purée with a standard error of prediction of 11.6%, implying a minimum detectable level of 25% (v/v) apple. GC-MS analysis enabled identification of the compounds with the greatest influence on sample differentiation. These compounds were identified as hexanoic acid, 2-hexenal, and alpha-farnesene, all of which are key aroma compounds in apples.

Identification and quantification of methyl jasmonate in leaf volatiles of Arabidopsis thaliana using solid-phase microextraction in combination with gas chromatography and mass spectrometry.

Static headspace sampling with solid-phase microextraction has been used in combination with GC-FID and GC-MS for the specific enrichment, identification and quantification of volatile methyl jasmonate secreted by wounded leaves of Arabidopsis thaliana. The microsample method of analysis was found to be precise, accurate, sensitive and rapid. The detection limit of the procedure is 1.5 ppb (approximately 1.3 ng) per injection, which is of adequate sensitivity to detect the natural baseline levels of methyl jasmonate (approximately 10-100 ng/g) present in plant tissues. The method can be applied to most plants, requires a minimum of sample material, and shows the additional advantage that it is suitable for automation and could thus be used for high-throughput screening.

Headspace solid-phase microextraction in combination with gas chromatography–mass spectrometry for the rapid screening of organophosphorus insecticide residues in strawberries and cherries

A headspace solid-phase microextraction (HS-SPME) method in combination with GC–MS was used for the extraction and quantification of diazinon, fenitrothion, fenthion, parathion ethyl, bromophos methyl, bromophos ethyl and ethion. The method was developed using a 100-μm poly(dimethylsiloxane) fiber. The obtained results showed higher responses of the insecticides after addition of aliquots of water and solvent to the fruit samples. Calibration curves that were constructed for the analytes spiked into strawberry and cherry samples followed linear relationships with good correlation coefficients ( R 2>0.986). Linearity range was between 50 and 500 μg/kg and the precision was found to be lower than 15% when applying the optimized HS-SPME procedure to fruit samples. Limits of detection in both strawberry and cherry samples using GC–MS (selected ion monitoring mode) were below 13 μg/kg. Moreover, the HS-SPME method was applied to the analysis of fruit samples and compared with liquid–liquid extraction. Results obtained in this study were in good agreement with those obtained using liquid–liquid extraction demonstrating that the recommended procedure was a fast, accurate and stable sample pretreatment method obtaining good efficiency for the extraction of organophosporus insecticides from strawberries and cherries.

Rapid differentiation of new apple cultivars by headspace solid-phase microextraction in combination with chemometrical data processing.

The aim of this study was to test a combination of automated headspace solid phase-microextraction gas chromatography (GC) with chemometrical data treatment for the rapid differentiation of enzyme-inactivated homogenates of new apple cultivars. The four cultivars Pinova, Piflora, Renora and Florina are characterized by different volatile patterns. Differences in the contents of volatiles were especially found for butyl acetate, ethyl butanoate, 2-methyl butanol, ethyl acetate and 6-methyl-5-hepten-2-ol. The used sample preparation method for GC coupled with pattern recognition of chromatograms is a useful tool for rapid and reliable determination of large numbers of samples.

Determination of MTBE in a recreational harbor using solid-phase microextraction

Discovery of the fuel additive methyl tert-butyl ether (MTBE) in groundwater, surface water, and stormwater has prompted studies of its sources, transport and fate. More limited data, however, is available on the extent of contamination of coastal waters, as well as the persistence of MTBE in the marine environment. We apply here the combination of solid phase microextraction and gas chromatography–mass spectrometry to the detection of sub-to-low μg/l concentrations of MTBE in seawater samples. Analysis of samples collected at the Marina del Rey harbor, a shallow recreational harbor near Los Angeles, CA, show MTBE contamination in the low μg/l level. MTBE measurements were made at different depths, from the surface to the bottom, at five sites within the harbor during months showing no measurable precipitation. The highest concentration of MTBE (18 μg/l) was found at the boat launching ramp, and the lowest (0.2 μg/l) near the harbor entrance, approximately 2.3 km from the ramp. The levels of MTBE measured, as well as their variation over the study period, are fully consistent with recreational boating as the primary source of contamination. No evidence for MTBE contamination from the adjacent stormwater control channel was noted.

Study of light-induced volatile compounds in goat's milk cheese.

Light-induced volatile compounds in goat cheese were studied by a combination of solid phase microextraction (SPME)-gas chromatography (GC)-mass spectrometry (MS), headspace oxygen depletion, and sensory evaluation. Samples stored under fluorescent light for 2 days at 30 degrees C had 90% more volatile compounds and 4 times more headspace oxygen depletion than samples stored in the dark at 30 degrees C. The volatiles 1-heptanol, heptanal, nonanal, and 2-decenal were formed and increased only in the light-stored samples, which may be formed from singlet oxygen oxidation of unsaturated fatty acids. Sensory evaluation showed that samples stored under light had significantly more off-flavor than samples stored in the dark at 30 degrees C (P < 0.05), and 1-heptanol, heptanal, nonanal, and 2-decenal increased the goat cheese off-flavor significantly (P < 0.05).

Monitoring and fast detection of mycotoxin-producing fungi based on headspace solid-phase microextraction and headspace sorptive extraction of the volatile metabolites

Solid phase microextraction in combination with capillary GC–MS was used as monitoring technique for the collection and detection of the fungal volatile metabolite (+)-aristolochene by sporulated surface cultures of Penicillium roqueforti. A comparison was made between different toxigenic and nontoxigenic strains of P. roqueforti. Different growth conditions and media, such as malt extract agar, potato dextrose agar and sabouraud dextrose agar were compared. Whereas toxigenic strains produced large amounts of (+)-aristolochene, β-elemene, valencene and germacrene A, nontoxigenic P. roqueforti strains showed a remarkably different headspace profile, in which ethyl-2-hexenoate, E-β-caryophyllene, aromadendrene and β-patchoulene were the predominant volatiles, apart from other sesquiterpene hydrocarbons present at lower concentrations. Stir bar sorptive extraction, was also applied in the headspace sampling mode, i.e. headspace sorptive extraction (HSSE) for the enrichment of fungal volatiles from sporulated surface cultures to differentiate between toxigenic and nontoxigenic fungi. Hence, it can be concluded that headspace analysis of volatile fungal metabolites by SPME and HSSE in combination with capillary GC–MS is a suitable monitoring technique for the fast detection of mycotoxin producing fungi.

Separation and identification of aromatic acids in soil and the Everglades sediment samples using solid-phase microextraction followed by capillary zone electrophoresis.

The separation and identification of aromatic acids in soil and the Everglades sediment samples was carried out using solid-phase microextraction (SPME) followed by capillary zone electrophoresis (CZE). The soil and sediment samples were subject to a series of sample treatments including oxidative hydrolysis with molecular oxygen in a sodium hydroxide solution, acidification and filtration. The aromatic acids in the sample filtrate were extracted using SPME with a polyacrylate-coated fiber. The acids adsorbed on the fiber were subsequently desorbed in methanol. The desorbed acids were then separated by CZE. Several aromatic acids (e.g.. salicylic acid, p-coumaric acid, ferulic acid and vanillic acid) in both soil and sediment samples were separated, identified and quantified. The results of this study show that the combination of SPME with CZE is promising for environmental analysis.

Solid-phase microextraction in combination with GC/MS for quantification of the major volatile free fatty acids in ewe cheese.

This work describes a method for quantification of the major free fatty acids of ewe cheese that contribute to its distinct and strongly marked flavor. A headspace SPME method in combination with GC/MS was used for the extraction, identification, and quantification of butanoic, hexanoic, octanoic and decanoic acids in ewe cheeses. The method used for sample preparation was simple. A fiber coated with 85-microm polyacrylate film was chosen to extract the free fatty acids. To perform a reliable quantification, several factors were taken into consideration for reliable quantification, namely, (i) the influence of addition of water, of an electrolyte or of a hygroscopic salt, on the release of free fatty acids from the matrix; (ii) the linear relationship between the amount of analyte adsorbed by the SPME polymer film and the initial concentration of the analyte in the cheese sample; and (iii) the competition for adsorption by fiber. Water removal with sodium sulfate promoted a more efficient extraction of volatile free fatty acids; biases due to competition or linear range excesses were controlled by choosing the appropriate amount of sample for each ewe cheese. The method of standard additions was used with success for the quantification of free fatty acids. Calibration curves that were constructed for the major short-chain free fatty acids (butanoic, hexanoic, octanoic, and decanoic acids) spiked into cheese followed linear relationships with highly significant (p < 0.001) correlation coefficients (r > 0.999). Coefficients of variation of <7.9% indicated that the technique was reproducible. A marked increase in concentration of short-chain free fatty acids was observed during cheese ripening, ranging from 0.35 to 9.33 mg/100 g for butanoic acid, 0.363 to 4.34 mg/100 g for hexanoic acid, 0.343 to 2.0 mg/100 g for octanoic acid, and 1.291 to 3.85 mg/100 g for decanoic acid. The limits of quantification were registered at levels of parts per million. The absolute quantification of butanoic acid was also carried out by using isotope dilution assays (IDA). The levels of acid obtained with this method were similar to those obtained by the standard additions method.

Headspace solid-phase microextraction in combination with gas chromatography and tandem mass spectrometry for the determination of organochlorine and organophosphorus pesticides in whole human blood

A method for the determination of several organochlorine and organophosphorus pesticides in human whole blood samples was developed. The combination of solid-phase microextraction in headspace mode with gas chromatography with tandem mass spectrometry allowed the determination of 11 selected pesticides at ppb levels, minimizing the sample treatment. Quantitation was carried out by means of calibration curves prepared in blood using labelled surrogate/internal standards. The method showed good linearity between 1 and 50 ng ml −1 (0.5–25 ng ml −1 for HCB) using second-order calibration curves. Precision was found to be better than 20% at the three concentration levels assayed in the range of ng ml −1. The detection limits obtained were in the range 0.02–0.7 ng ml −1, except for p,p′-DDT (3 ng ml −1). The developed procedure was applied to blood and serum samples obtained from agricultural workers. HCB, β-HCH and p,p′-DDE were most frequently detected in the samples analyzed.

Analysis of fire ant pesticides in water by solid-phase microextraction and gas chromatography/mass spectrometry or high-performance liquid chromatography/mass spectrometry

The analysis of four widely used fire ant pesticides (chlorpyrifos, fenoxycarb, avermectin, and hydramethylnon) in water was accomplished by combining solid-phase microextraction (SPME) with either gas chromatography/quadruple ion trap mass spectrometry (GC/MS) or high-performance liquid chromatography/quadruple ion trap MS (HPLC/MS). Solid-phase microextraction is a fast, selective, and solvent-free extraction technique that accomplishes both extraction and pre-concentration events in a single step. These features allowed the methods developed to be sensitive, with calculated LOD of 10 ng/l for chlorpyrifos, 80 ng/l for fenoxycarb, 100 ng/l for avermectin, and 1 μg/l for hydramethylnon, each obtained from only 10 min extractions from standards in water. These values represent an improvement of an order of magnitude in detection limits for avermectin and hydramethylnon compared to those reported previously. The methods were shown to be linear in the range of 100 ng/l–100 μg/l for chlorpyrifos and fenoxycarb, 1 μg/l–1 mg/l for avermectin, and 10 μg/l–1 mg/l for hydramethylnon. These methods were applied to the analysis of water samples to which commercial fire ant bait preparations had been added and to runoff water collected from a lawn. Quantitative analyses were performed for chlorpyrifos, fenoxycarb, and avermectin, as the pesticides in the water samples were monitored for ∼9 days to almost 2 months. However, due to poor precision of the method for hydramethylnon, only qualitative data were obtained.