Determination of methanol in biodiesel by headspace solid phase microextraction

A new direct gas chromatography procedure (headspace solid phase microextraction) was developed for the quantitative determination of methanol in biodiesel. The analysis was performed by exposing a carboxen–polydimethylsiloxane SPME fiber assembly to the headspace of the biodiesel sample. The gas chromatography used a HP-5 capillary column and flame ionization detection. A polynomial relationship was observed between the methanol concentration and its peak area. This method showed good reproducibility (average relative standard deviation 7.06%) and recovery (average recovery 100.2%).     

Analysis of strawberry volatiles using comprehensive two-dimensional gas chromatography with headspace solid-phase microextraction

The aims of the current study were to develop an enantioselective multi-dimensional gas chromatography (GC x GC) method for the examination of strawberry volatiles and to use this method to make comparisons between the volatile profiles of different cultivars and between fresh picked and post-harvest berries of the same cultivar. Strawberry volatiles were sampled using solid-phase microextraction (SPME), and the repeatability and reproducibility of this method was examined. Semi-quantitative analysis of the volatiles was conducted using the relatively new technique of comprehensive multi-dimensional gas chromatography, using enantioselective (chiral) columns for the differentiation of analyte enantiomers. Chiral GC x GC facilitated the detection of key enantiomers in strawberry flavour. The (-)-enantiomer of 2,5-dimethyl-4-hydroxy-(2H)-furan-3-one (DMHF) and the S-enantiomer of linalool were tentatively identified as the predominant forms in both the cultivars Selva and Adina. The compounds benzaldehyde and methyl hexanoate were shown to decrease in post-harvest berries, whilst DMHF and nerolidol increased upon storage.     

Analysis of volatile constituents isolated by hydrodistillation and headspace solid-phase microextraction from Adenostyles briquetii Gamisans

The volatile fraction of the whole plant and separated organs of Adenostyles briquetii Gamisans (syn. Cacalia briquetii; family Asteraceae), an endemic species from Corsica, has been studied by headspace solid-phase microextraction (HS-SPME), GC and GC-MS(EI and CI). A total of 141 components were identified, representing 93% of the entire amount. The volatile fraction was characterised by sesquiterpene hydrocarbons (52.8%) and oxygenated sesquiterpenes (25.9%). The major components were germacrene D (18.5%), zingiberene (12.9%) and beta-oplopenone (10.8%). The influence of HS-SPME parameters on the extraction of family components is reported for the first time.     

采用多次顶空固相微萃取分析拟南芥绿叶挥发性物质

顶空固相微萃取作为一种新的挥发性和半挥发性物质分析技术,被广泛应用于植物样品的定性分析。由于进行顶空分析时,挥发性组分间的基质效应以及较为复杂的扩散和吸附过程,定量分析一直是SPME分析应用的难题。目标分析物的量看作是达到吸附平衡后单一萃取的物质量的总和,则无需考虑分析样品在顶空、萃取涂层间的分配,同时可以消除基质效应。在利用标准物质进行校正后只需要一次顶空萃取,即可求出分析物质的总量。首先利用DVB/CAR/PDMS定性得到拟南芥挥发性物质的组成,然后采用CAR/PDMS涂层定量,分析了拟南芥的3种绿叶挥发性物质,优化后萃取条件为40℃萃取20min,相对标准偏差小于12%,在3株植物样品中这些挥发性物质的量为78.6~158.4ng.g-1。     

Developments in multiple headspace extraction

This paper reviews new developments in multiple headspace extraction (MHE), especially its combination with two miniaturized extraction techniques, solid-phase microextraction (SPME) and single-drop microextraction (SDME). The combination of the techniques broadens the applicability of SPME and SDME to quantitative determination of analytes in complex liquid and solid matrixes. These new methods offer several advantages over traditional liquid-solid, liquid-liquid and headspace extraction techniques. The potential applications include extraction of volatiles and semivolatiles from environmental and physiological samples and from different polymer products such as medical and biomedical materials, food packaging and building materials. The theoretical principals of the techniques are also briefly reviewed.     

Gas chromatography-mass spectrometric analysis of hexanal and heptanal in human blood by headspace single-drop microextraction with droplet derivatization

In this work, we developed a new approach to the analysis of the lung cancer biomarkers, hexanal and heptanal in human blood that was based on headspace single-drop microextraction (HS-SDME) with droplet derivatization, followed by gas chromatography-mass spectrometry (GC-MS). Aldehydes in blood were headspace extracted, concentrated, and derivatized by a suspended microdrop solvent containing the derivatization agent O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride. The aldehyde oximes formed in the microdrop solvent were analyzed by GC-MS. The optimal HS-SDME with droplet derivatization parameters extraction solvent of decane, sample temperature of 40 degrees C, extraction time of 6 min, stirring rate of 1100 rpm, and solvent volume of 2.0 microL were obtained and used for analysis of hexanal and heptanal in blood. The method reproducibility, linearity, recovery, and detection limit were studied and the obtained results demonstrated the method feasibility. Finally, the proposed method was applied to the quantification of hexanal and heptanal in cancer blood and normal blood. Due to sample extraction, concentration, and derivatization being performed in a single step, the method provided a simple, rapid, low-cost, and efficient approach to analysis of aldehydes in blood samples.     

Determination of dichloromethane, trichloroethylene and perchloroethylene in urine samples by headspace solid phase microextraction gas chromatography-mass spectrometry

A method for the determination of volatile chlorinated hydrocarbons, namely dichloromethane (DCM), trichloroethylene (TCE), and perchloroethylene (PCE), in urine samples was developed using headspace solid phase microextraction (HS-SPME) gas chromatography-mass spectrometry (GC-MS). HS-SPME was performed using a 75 microm Carboxen-polydimethylsiloxane fiber. Factors, which affect the HS-SPME process, such as adsorption and desorption times, stirring, salting-out effect, and temperature of sampling have been evaluated and optimized. The highest extraction efficiency was obtained when sampling was performed at room temperature (22 degrees C), from samples saturated with salt and under agitation. Linearity of the HS-SPME-GC-MS method was established over four orders of magnitude and the limit of detection was 0.005 microg/l for all the compounds. Precision, calculated as %R.S.D. at three different concentration levels, was within 1-8% for all intra- and inter-day determinations. The method was applied to the quantitative determination of TCE and PCE in human urine samples from exposed (TCE, n=5; median, 9.32 microg/l and PCE, n=39; median, 0.58 microg/l) and non-exposed individuals (n=120; median concentrations, 0.64, 0.22 and 0.11 microg/l for DCM, TCE and PCE, respectively. In addition, two cases of acute accidental exposure to DCM are reported, and the elimination kinetics in blood and urine was followed up. The calculated half-lives of urinary and blood DCM were, respectively, 7.5 and 8.1 h for one subject and 3.8 and 4.3 h for the other.     

An alternative method for irones quantification in iris rhizomes using headspace solid-phase microextraction

Introduction – The essential oil obtained from iris rhizomes is one of the most precious raw materials for the perfume industry. Its fragrance is due to irones that are gradually formed by oxidative degradation of iridals during rhizome ageing. Objective – The development of an alternative method allowing irone quantification in iris rhizomes using HS‐SPME‐GC. Methodology – The development of the method using HS‐SPME‐GC was achieved using the results obtained from a conventional method, i.e. a solid–liquid extraction (SLE) followed by irone quantification by CG. Results – Among several calibration methods tested, internal calibration gave the best results and was the least sensitive to the matrix effect. The proposed method using HS‐SPME‐GC is as accurate and reproducible as the conventional one using SLE. These two methods were used to monitor and compare irone concentrations in iris rhizomes that had been stored for 6 months to 9 years. Conclusion – Irone quantification in iris rhizome can be achieved using HS‐SPME‐GC. This method can thus be used for the quality control of the iris rhizomes. It offers the advantage of combining extraction and analysis with an automated device and thus allows a large number of rhizome batches to be analysed and compared in a limited amount of time. Copyright © 2010 John Wiley & Sons, Ltd.     

A quantitative headspace–solid-phase microextraction–gas chromatography–flame ionization detector method to analyze short chain free fatty acids in rat feces

This study sought to develop and validate a quantitative method to analyze short chain free fatty acids (SCFAs) in rat feces by solid-phase microextraction and gas chromatography (SPME–GC) using the salt mixture ammonium sulfate and sodium dihydrogen phosphate as salting out agent. Conditioning and extraction time, linearity, limits of detection and quantification, repeatability, and recovery were evaluated. The proposed method allows quantification with improved sensitivity as compared with other methods exploiting SPME–GC. The method has been applied to analyze rat fecal samples, quantifying acetic, propionic, isobutyric, butyric, isopentanoic, pentanoic, and hexanoic acids.     

Three-phase liquid-phase microextraction of weakly basic drugs from whole blood

The behaviour of weak basic analytes in liquid-phase microextraction (LPME) and the optimisation of parameters in whole blood are described. Benzodiazepines and non-benzodiazepine drugs were chosen as model substances. Liquid-phase microextraction based on disposable polypropylene hollow fibres was used in the three-phase extraction of five weak bases from whole blood. The sample work up with the liquid-phase microextraction technique can be impeded by low recovery due to incomplete trapping in the acceptor phase of weakly basic drugs and the complexity of the whole blood matrix. Different parameters related to this problem were experimentally studied. Additionally the stability of the analytes was examined because of low pH in the acceptor phase. The investigation resulted in optimised LPME conditions for the extraction of weak bases from whole blood. The parameters limiting the recovery were evaluated.     

Evaluation of electrochemically synthesized sulfadimethoxine‐imprinted polymer for solid‐phase microextraction of sulfonamides

Solid‐phase microextraction (SPME) is widely used in analytical laboratories for the analysis of organic compounds, thanks to its simplicity and versatility. In the present work, the synthesis and evaluation of imprinted films for SPME by electropolymerisation of pyrrole alone or in the presence of ethylene glycol dimethacrylate is proposed. Sulfadimethoxine (SDM), a sulfonamide antibiotic, was used as template molecule. Initially, a molecularly imprinted polymer film was prepared by electropolymerisation of pyrrole onto a platinum foil, using SDM as template. The SDM template was removed by overoxidation. The behaviour of SDM on imprinted and non‐imprinted polymers was investigated by differential pulse voltammetry, and a clear imprinting effect was observed, which was confirmed by rebinding experiments using both conventional and electrochemically enhanced‐SPME. However, in general, the extraction efficiency was rather low (<6%) and unspecific interactions are too high. Attempts to increase extraction efficiency were unsuccessful, but the incorporation of ethylene glycol dimethacrylate to the films reduced unspecific interactions to a certain extent. Copyright © 2014 John Wiley & Sons, Ltd.     

Monitoring seasonal variation in apple fruit volatile emissions in situ using solid-phase microextraction

Emissions of volatiles from apple fruits (Malus domestica Borkh.) were monitored in situ over the course of a growing season (from early June to mid September) for two apple varieties, Golden Delicious and Maigold. Results indicate a characteristic time-course of volatile emissions as the sampling date was a statistically significant factor for nine of the 13 compounds considered. The amounts of volatiles collected were greatest early and late in the season. The temporal effect on emissions was generally much larger than the effect of variety, which was significant for only four of the 13 compounds considered. The possible sources of variation which are not explained by the statistical models are discussed, and it is considered that they are most likely related to differences in the emissions from individual fruits.     

Determination of acrolein by headspace solid-phase microextraction gas chromatography and mass spectrometry

We developed a headspace solid-phase microextraction (headspace SPME) method to measure acrolein in human urine. This new technique resolves some problems with the headspace gas chromatography and mass spectrometry (GC–MS) method which we developed previously. With the original method, a column and a filament were damaged by the injection of air. A 0.5-ml urine (or phosphate-buffered saline) sample in a glass vial containing propionaldehyde as an internal standard was heated for 5 min. The SPME fiber (65 μm carbonwax–divinylbenzene fiber) was exposed to the headspace and then inserted into a GC–MS instrument in which a DB-WAX capillary column (30 m×0.32 mm, film thickness 0.5 μm) was installed. The total analysis time was 15 min. The inter-assay and intra-assay coefficients of variation were 10.07 and 5.79%, respectively. The calibration curve demonstrated good linearity throughout concentrations ranging from 1 to 10 000 nM. The headspace SPME method exhibits high sensitivity and requires a short analysis time as well as the previous method. We conclude that this method is useful to measure urinary acrolein.     

Simultaneous detection of amphetamine-like drugs with headspace solid-phase microextraction and gas chromatography-mass spectrometry

A headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS) procedure for the simultaneous detection of methylen-dioxyamphetamine (MDA), methylen-dioxymethamphetamine (MDMA), methylen-dioxyethamphetamine (MDE) and N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB) in hair has been developed. This method is suitable for the separation of primary and secondary amines, is reproducible, is not time consuming, requires small quantities of sample and does not require any derivatization. It provides sufficient sensitivity and specificity, with limits of detection (LOD) and limits of quantitation (LOQ) for each substance of <0.7 and 1.90 ng/mg, respectively. Intra- and inter-day precision were within 2 and 10%, respectively. This method is suitable for routine clinical, epidemiological and forensic purposes and can be used for the preliminary screening of many other substances (amphetamine, methamphetamine, ketamine, ephedrine, nicotine, phencyclidine, methadone) in hair and other biological matrices such as saliva, urine and blood. We also describe the first application of this HS-SPME-GC-MS procedure to the analysis of hair and saliva samples from young people attending a disco in the Rome area. All positive hair samples were confirmed by the gas chromatography-mass-mass (GC-MS(2)) technique in positive chemical ionization (PCI) mode. Some examples of the use of the method in detecting different drugs are reported.     

Determination of amphetamines in human urine by headspace solid-phase microextraction and gas chromatography

Solid-phase microextraction (SPME) is under investigation for its usefulness in the determination of a widening variety of volatile and semivolatile analytes in biological fluids and materials. Semivolatiles are increasingly under study as analytical targets, and difficulties with small partition coefficients and long equilibration times have been identified. Amphetamines were selected as semivolatiles exhibiting these limitations and methods to optimize their determination were investigated. A 100- micro m polydimethylsiloxane (PDMS)-coated SPME fiber was used for the extraction of the amphetamines from human urine. Amphetamine determination was made using gas chromatography (GC) with flame-ionization detection (FID). Temperature, time and salt saturation were optimized to obtain consistent extraction. A simple procedure for the analysis of amphetamine (AMP) and methamphetamine (MA) in urine was developed and another for 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-N-methamphetamine (MDMA) and 3,4-methylenedioxy-N-ethylamphetamine (MDEA) using headspace solid-phase microextraction (HS-SPME) and GC-FID. Higher recoveries were obtained for amphetamine (19.5-47%) and methamphetamine (20-38.1%) than MDA (5.1-6.6%), MDMA (7-9.6%) and MDEA (5.4-9.6%).     

Use of solid phase microextraction (SPME) for profiling fungal volatile metabolites

AIMS: The influence of isolation methods: solid phase microextraction (SPME) with different fibres and simultaneous distillation extraction (SDE) on the profile of isolated fungal volatile metabolites was investigated. METHODS AND RESULTS: Four SPME fibre types: Polydimethylsiloxane, Polyacrylate, Carboxen/PDMS and Carboxen/Divinylbenzene/PDMS were evaluated in terms of their efficiency in extracting volatile metabolites emitted by Penicillium roqueforti grown on wheat kernel medium. All fibres showed varied efficiency and selectivity in extracting volatile compounds. Sesquiterpene hydrocarbons were the predominant fraction of volatile compounds isolated by all fibres, and ranged from 55.4 to 93.7% of all volatiles depending on the type of fibre used. Alcohols and ketones ranged from 2.7 to 20.5%, esters from 1.2 to 12.8%, and monoterpene hydrocarbons from 1.2 to 5.4%. Profile of volatile compounds obtained by SDE differed from SPME and the oxygenated sesquiterpenes formed the predominant fraction of volatiles isolated using SDE. SIGNIFICANCE AND IMPACT OF THE STUDY: The data in this study show that analysed profile of volatile compounds emitted by fungi is highly dependent on the extraction method.     

Solid-phase microextraction for determining twelve orange flavour compounds in a model beverage emulsion

Solid-phase microextraction (SPME) coupled to gas chromatography has been applied for the headspace analysis (HS) of 12 target flavour compounds in a model orange beverage emulsion. The main volatile flavour compounds studied were: acetaldehyde, ethyl acetate, alpha-pinene, ethyl butyrate, beta-pinene, myrcene, limonene, gamma-terpinene, octanal, decanal, linalool and citral (neral plus geranial). After screening the fibre type, the effect of other HS-SPME variables such as adsorption temperature (25-55 degrees C), extraction time (10-40 min), sample concentration (1-100% w/w), sample amount (5-10 g) and salt amount (0-30% w/w) were determined using a two-level fractional factorial design (2(5-2)) that was expanded further to a central composite design. It was found that an extraction process using a carboxen-polydimethylsiloxane fibre coating at 15 masculineC for 50 min with 5 g of diluted emulsion 1% (w/w) and 30% (w/w) of sodium chloride under stirring mode resulted in the highest HS extraction efficiency. For all volatile flavour compounds, the linearity values were accurate in the concentration ranges studied (r(2) > 0.97). Average recoveries that ranged from 90.3 to 124.8% showed a good accuracy for the optimised method. The relative standard deviation for six replicates of all volatile flavour compounds was found to be less than 15%. For all volatile flavour compounds, the limit of detection ranged from 0.20 to 1.69 mg/L.     

Application of solid-phase microextraction combined with derivatization to the determination of amphetamines by liquid chromatography

This work evaluates the utility of solid-phase microextraction (SPME) in the analysis of amphetamines by liquid chromatography (LC) after chemical derivatization of the analytes. Two approaches have been tested and compared, SPME followed by on-fiber derivatization of the extracted amphetamines, and solution derivatization followed by SPME of the derivatives formed. Both methods have been applied to measure amphetamine (AP), methamphetamine (MA), and 3,4-methylenedioxymethamphetamine (MDMA), using the fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) and carbowax-templated resin (CW-TR)-coated fibers. Data on the application of the proposed methods for the analysis of different kind of samples are presented. When analyzing aqueous solutions of the analytes, both approaches gave similar analytical performance, but the sensitivity attainable with the solution derivatization/SPME method was better. The efficiencies observed when processing spiked urine samples by the SPME/on-fiber derivatization approach were very low. This was because the extraction of matrix components into the fiber coating prevented the extraction of the reagent. In contrast, the efficiencies obtained for spiked urine samples by the solution derivatization/SPME approach were similar to those obtained for aqueous samples. Therefore, the later method would be the method of choice for the quantification of amphetamines in urine.     

Determination of metaldehyde in human serum by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A rapid headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method has been developed for the determination of metaldehyde in human serum samples. Metaldehyde is extensively used as a molluscicide for the control of slugs and snails, and cases of metaldehyde poisoning have been reported. Metaldehyde was headspace-extracted on a polydimethylsiloxane (PDMS) fiber at 70 degrees C for 25 min, desorbed, and analyzed rapidly by GC-MS. The method was validated for limit of detection (LOD), linearity, precision, and recovery. Although the recovery of the sample was very low, the method itself was rapid with a low detection limit of 0.25 microg/ml, R.S.D. value 12.6%, and linearity range 0.5-25.0 microg/ml (r(2)=0.999). The results demonstrated that the SPME-GC-MS method for the analysis of metaldehyde is simple, rapid, solvent-free, and does not require any pre-analysis conversions.