New PVC materials for medical applications—the release profile of PVC/polycaprolactone–polycarbonate aged in aqueous environments

Medical grade PVC plasticised with polycaprolactone–polycarbonate (PCL–PC) was subjected to aqueous environments at different temperatures. The release profile during ageing was determined by solid phase microextraction (SPME) and GC–MS. At the same time changes in the surface composition due to, for example, migration of PCL–PC from the blend were followed by FTIR. Almost no changes in the material or its surface composition were observed during 98 days at 37 °C in water or phosphate buffer. Only trace amount of 6-hydroxyhexanoic acid the final hydrolysis product of PCL–PC was detected in the GC–MS chromatograms and the weight loss was negligible. Even when the ageing temperature was raised to 70 °C only minor increase in the amount of 6-hydroxyhexanoic acid was observed and the weight loss after 98 days was under 1%. Changes in the FTIR spectra indicating migration of PCL–PC towards the surface of the PVC/PCL–PC tubing were observed first after 70 days at 70 °C. Large increase in the hydrolysis rate of PCL–PC and almost complete depletion of PCL–PC from the blend was observed when the ageing temperature was raised to 100 °C.     

Evaluation of solid-phase microextraction as an alternative to the official method for the analysis of organic micro-pollutants in drinking water

The objective this study was to compare the official EU liquid-liquid extraction (LLE) method with solid-phase microextraction (SPME) for the analysis of compounds migrating from cross-linked polyethylene into water. A medium polarity polydimethylsiloxane/divinylbenzene (PDMS/DVB) 65 microm fibre proved most efficient for the SPME extraction of nine test compounds and the optimum extraction conditions were an immersion time of 30 min with heating to 60 degrees C. The repeatability of the SPME method was variable: RSD values ranged from approximately 4-18% depending on the individual compound, though correlation coefficients were greater than 0.999 in the concentration range 0.5-1000 microg/l. It would also seem that there is some competition amongst different compounds for sites on the fibre and this is a potential drawback of SPME when applied to unknown samples. However, when applied to water samples in contact with polyethylene, SPME proved to be immensely more sensitive and to have a greater extraction range than LLE. These factors coupled with the rapidity and ease of use of SPME mean that it could be developed for use as an alternative to the existing official method or as an alert system in the routine analysis of materials used to transport domestic water.     

Migration of Additives from Poly(vinyl chloride) (PVC) Tubes into Aqueous Media

The stability and migration product of medical PVC tubes plasticized with polyadipates were investigated by ageing in phosphate buffer at pH 1.679 and water at different temperatures. Changes in the PVC tubes were studied by water absorption, weight loss, Fourier infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The low molecular weight migration product that was released was extracted and silylanized before gas chromatography/mass spectroscopy (GC/MS) identification and quantification. After 70 days, the weight loss was less than 0.5% and only a small amount of adipic acid migrated when a tube was aged at 37°C in water and phosphate buffer (pH 1.679), and at 70°C in water after 56 days. However, when aged at 70 and 110°C, gradual deactivation of heat stabilizer after 21 days of ageing in buffer solution and separation of plasticizer from PVC matrix occurred. When the tube was aged at 110°C, significant degradation of both polyadipates and PVC were observed. Adipic acid and 1,4-butanediol monomers and oligomers of polyadipate were the major migration products from polyadipates in the water ageing solution, while only a relatively high amount of adipic acid was identified as the main product in the buffer ageing solution.     

Solid-phase microextraction coupled with gas chromatography-ion trap mass spectrometry for the analysis of haloacetic acids in water

Headspace solid-phase microextraction (SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of haloacetic acids (HAAs) in water. The method involves derivatization of the acids to their ethyl esters using sulphuric acid and ethanol after evaporation, followed by headspace SPME with a polydimethylsiloxane fibre and gas chromatography-ion trap mass spectrometry (GC-IT-MS). The derivatization procedure was optimized: maximum sensitivity was obtained with esterification for 10 min at 50 degrees C in 30 microl of sulphuric acid and 40 microl of ethanol. The headspace SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25 degrees C, an absorption time of 10 min, the addition of 0.1 g of anhydrous sodium sulfate and a desorption time of 2 min. Good precision (RSD lower than 10%) and detection limits in the ng l(-1) range (from 10 to 200 ng l(-1)) were obtained for all the compounds. The optimized procedure was applied to the analysis of HAAs in tap water and the results obtained by standard addition agreed with those of EPA method 552.2, whereas discrepancies due to matrix interferences were observed using external calibration. Consequently, headspace SPME-GC-IT-MS with standard addition is recommended for the analysis of these compounds in drinking water.     

Solid-Phase Microextraction Gas Chromatography for Determination of Some Organophosphorus Pesticides

A simple and rapid solid-phase microextraction (SPME) method is presented based on activated charcoal–PVC fiber for determination of some organophosphorus pesticides from aqueous samples in direct mode SPME. After optimization of the experimental variables affecting SPME of the target compounds from aqueous solutions, the proposed method was applied to determine pesticides in fruit juice. The analytes in this procedure were preconcentrated for 15 min on the SPME fiber and subsequently desorbed by heating the fiber at 200 °C for 5 min in the GC injection port. Separation was on a capillary column GC followed by flame ionization detection. Recoveries of the pesticides studied in aqueous samples ranged 42%–63% and repeatability for all analytes was < 9% for a single fiber. Fiber-to-fiber reproducibility was < 18%.     

Volatile flavour constituent patterns of Terras Madeirenses red wines extracted by dynamic headspace solid-phase microextraction

A suitable analytical procedure based on static headspace solid-phase microextraction (SPME) followed by thermal desorption gas chromatography-ion trap mass spectrometry detection (GC-(ITD)MS), was developed and applied for the qualitative and semi-quantitative analysis of volatile components of Portuguese Terras Madeirenses red wines. The headspace SPME method was optimised in terms of fibre coating, extraction time, and extraction temperature. The performance of three commercially available SPME fibres, viz. 100 mum polydimethylsiloxane; 85 mum polyacrylate, PA; and 50/30 mum divinylbenzene/carboxen on polydimethylsiloxane, was evaluated and compared. The highest amounts extracted, in terms of the maximum signal recorded for the total volatile composition, were obtained with a PA coating fibre at 30 degrees C during an extraction time of 60 min with a constant stirring at 750 rpm, after saturation of the sample with NaCl (30%, w/v). More than sixty volatile compounds, belonging to different biosynthetic pathways, have been identified, including fatty acid ethyl esters, higher alcohols, fatty acids, higher alcohol acetates, isoamyl esters, carbonyl compounds, and monoterpenols/C(13)-norisoprenoids.     

Monoterpenic and norisoprenoidic glycoconjugates of Vitis vinifera L. cv. Melon B. as precursors of odorants in Muscadet wines.

The volatile monoterpenic and norisoprenoidic compounds released by glycosidase enzyme hydrolysis of C18 reversed-phase isolates from the juice of Vitis vinifera L. cv. Melon B. have been qualitatively and quantitatively determined using GC-MS and GC-FID. The components analyzed were broadly similar to those previously reported for other varieties but the level of bound p-menth-1-en-7,8-diol was higher in this cultivar. Then the monoterpenic and norisoprenoidic volatiles released from the same glycosidic extracts under mild acid conditions, mimicking wine aging conditions, have been analyzed using GC-Olfactometry and GC-MS. The most odorous compounds detected were p-cymene, terpinen-4-ol, cis- and trans-vitispiranes, 1,6,6-trimethyl-1,2-dihydronaphtalene (TDN), beta-damascenone and riesling acetal. To assess their potential levels in corresponding wines after ageing, most of these odorants were generated by harsh acid hydrolysis from the precursors extracts and quantitatively determined using SPME and GC-MS/MS. For the development and application of this analysis, the odorants not commercialy available were synthesized. The total amounts of norisoprenoidic odorants generated by acid hydrolysis of the glycosidic extracts were shown to be proportional to the total amounts of these precursors.     

固相微萃取-气相色谱/质谱测定植物叶片中的挥发性物质

采用固相微萃取（SPME)方法吸附植物叶片中的挥发性物质,然后采用气相色谱/质谱法（GC/MS）分析了挥发性物 质的成分。在45 ℃水浴温度下,采用Polyacrylate(85 μm)固相微萃取头,在广口瓶中植物叶片的上方顶空吸附60 min,然后进行GC/MS分析。结果表明,植物叶片中的挥发性物质得到了很好的分离,受山楂叶螨(Tetraychus vienneis) 危害严重的植物的完好叶片中的挥发性物质均含有顺-3-己烯-1-醇乙酸酯、顺-3-己烯-1-醇丁酸酯和α-法呢烯,且含量 较大。初步确定这些物质是对山楂叶螨具有引诱作用的主要物质,从而为利用天然生物活性物质防治山楂叶螨提供了理论 依据。     

Flavour analysis of Greek white wine by solid-phase microextraction-capillary gas chromatography-mass spectrometry

Solid-phase microextraction (SPME) was optimised for the qualitative determination of the volatile flavour compounds responsible for the aroma of Greek Boutari wine. Several factors influencing the equilibrium of the aroma compounds between the sample and the SPME fiber were taken into account, including the extraction time, the extraction temperature, the sampling mode (headspace and direct immersion or liquid SPME), and the presence of salt. Four different SPME fibers were used in this study. namely poly(dimethylsiloxane) (PDMS), poly(acrylate), carbowax-divinylbenzene and divinylbenzene-carboxen on poly(dimethylsiloxane). The best results were obtained using the PDMS fiber during headspace extraction at 25 degrees C for 30 min after saturating the samples with salt. The optimised SPME method was then applied to investigate the qualitative aroma composition of three other Greek wines, namely Zitsa, Limnos and Filoni.     

Analysis of terpenes in white wines using SPE-SPME-GC/MS approach

Terpenes contribute to some white wines aroma, especially these produced from Muscat grapes and others aromatic ones of high terpene contents (Gewürtztramminer, Traminer, Huxel, Sylvaner). Terpenes are present in wine in free and bound (in a form of glycosides) forms. Analyses of bound terpenes are usually performed using solid phase extraction after hydrolysis of glycosides. A new method for determination of terpenes from wine, focused on determination of terpenes released after acidic hydrolysis, based on solid phase extraction (SPE) followed by solid phase microextraction (SPME) was developed. Non-polar (free) and polar (bound terpenes) fractions were separated on 500 mg C18 cartridges. Bound terpenes were sampled using SPME immediately after acidic hydrolysis in non-equilibrium conditions. Application of combined SPE-SPME approach allowed quantification of selected terpenes in lower concentrations than in SPE approach and added a selectivity to the method, which enabled detection of compounds non-detectable in SPE extracts. Results obtained by SPE and SPE-SPME approach were correlated for free terpenes and those released after acid hydrolysis 20 white wines obtained from different grape varieties (R² = 0.923). Although developed for wine terpenes analysis, SPE followed by SPME approach has a great potential in analysis of other bound wine flavor compounds, especially those potent odorants present in trace amounts.     

Headspace-solid-phase microextraction preconcentration of phenols, indoles and on-fibre derivatised volatile fatty acids in liquid and gas samples from cow slurries

Odorous organic compounds from liquid and gas samples of animal wastes were studied by headspace (HS)-solid-phase microextraction (SPME)-GC-MS. 1-Pirenyldiazomethane (PDAM) was adsorbed/absorbed on the SPME fibre in order to obtain the corresponding ester derivatives during the preconcentration step. The SPME fibre was immersed into a PDAM solution. Then, the SPME fibre was withdrawn and exposed to the HS of the liquid cow slurry. This way derivatisation of VFAs took place in the SPME fibre together with the preconcentration of the rest of the analytes of interest. The analytes were desorbed in the hot injection port (300 degrees C) of a GC-MS for 3 min. Four different fibre types and different immersion periods of the fibre in the PDAM solution were studied in order to obtain the best sensitivity with the selected fibre. Accuracy, precision and the LODs were calculated using spiked liquid and gas samples. The possibility of storing liquid samples after sampling by preconcentration on the fibre was also considered. Storage time and temperature were studied. The optimised method was applied to the determination of the analytes in liquid and gas samples from cow slurries from an intensive production farm.     

Optimisation of a headspace solid-phase microextraction with on-fiber derivatisation method for the direct determination of haloanisoles and halophenols in wine

A solid-phase microextraction (SPME) procedure for the determination of four haloanisoles (2,4,6-trichloroanisole, 2,3,4,6-tetrachloroanisole, pentachloroanisole and 2,4,6-tribromoanisole), as well as their precursor halophenols (2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol and 2,4,6-tribromophenol), involved in the presence of cork taint in wine, was developed. Firstly, analytes were concentrated on a SPME fiber, and then halophenols were derivatised using N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA). The compounds were desorbed for 5 min in the gas chromatography injector port and then determined with an electron capture detector. The influence of different parameters on the efficiency of extraction (volume of sample, type of fibre coating and time) and derivatisation (time, temperature and volume of MSTFA) steps was evaluated. Polyacrylate (PA) was selected as the extraction fiber, optimised parameters for SPME were 10 ml of wine, temperature 70 degrees C and extraction time 60 min. The optimal conditions identified for the derivatisation step were temperature 25 degrees C, reagent volume 50 microl and extraction time 25 min. Under optimal conditions, the proposed method showed satisfactory linearity, precision and detection limits. The method was applied successfully to the analysis of red wine samples. To our knowledge, this is the first time that headspace (HS) SPME combined with on-fiber derivatisation has been applied to determine cork taint responsible compounds in wine.     

Identification of volatile organic compounds emitted by a naturally aged book using solid-phase microextraction/gas chromatography/mass spectrometry

Solid-phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) has been applied to the analysis of volatile organic compounds emitted from a naturally aged groundwood pulp paper originating from an old book in order to access the products produced through the decomposition reactions occurring in paper upon ageing. Two different extraction methods were developed and compared: headspace SPME and contact SPME. The influence of few extraction parameters were tested in order to define the best extraction conditions. An optimised non-destructive contact SPME method was elaborated and allowed the characterisation of more than 50 individual constituents.     

Rapid determination of C6-aldehydes in tomato plant emission by gas chromatography-mass spectrometry and solid-phase microextraction with on-fiber derivatization

A simple, rapid, sensitive, and solvent-free method was developed for determination of plant-signalling compounds, the three C6-aldehydes hexanal, (Z)-3-hexenal, and (E)-2-hexenal, in tomato plant emission by gas chromatography-mass spectrometry (GC-MS) and solid-phase microextraction (SPME) with on-fiber derivatization. In this method, O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine (PFBHA) in aqueous solution was first headspace adsorbed onto a 65 microm poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber at 25 degrees C for 5 min, and then the fiber with adsorbed PFBHA was used for headspace extraction of tomato plant emission at 25 degrees C for 6 min. Finally, the resulting oximes adsorbed on the fiber were desorbed and analyzed by GC-MS. Extraction conditions and method validation were studied. The proposed method had low detection limit values for the three aldehydes from 0.1 to 0.5 ng/L and good precision (RSD less than 10%). In this work, the method was applied to investigation of tomato plant defense response to Helicoverpa armigera.     

Determination of volatile alkyl sulfides in wastewater by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry

An analytical procedure based on headspace solid-phase microextraction (SPME) followed by gas chromatography coupled to mass spectrometry in the electron impact mode has been developed for the determination of low-molecular-mass sulfides and disulfides in wastewater. Parameters affecting to the extraction of these volatile alkyl sulfides (VASs) with the SPME, such as the extraction temperature, sample volume, pH and the NaCl addition to the matrix, have been optimised using a polydimethylsiloxane-Carboxen fibre. The linear dynamic range was close to three orders of magnitude for all the studied compounds. Detection limits of 4 ng l(-1) for dimethyl sulfide, 0.7 ng l(-1) for ethylmethyl sulfide, 5 ng l(-1) for diethyl sulfide and 1 ng l(-1) for dimethyl disulfide were achieved, with a relative standard deviation between 4 and 6%. The developed analytical methodology was applied to determine those VASs in different wastewaters.     

RPHPLC determination of L- and D-cystine and cysteine as cysteic acid

Summary In the quantitative analysis of cystine and cysteine, before hydrolysis the compounds are often oxidized to cysteic acid with performic acid. The applicability of this process to the quantification of the enantiomers of cystine and cysteine has been examined. An RPHPLC analytical method was developed for determination of the amount of cysteic acid enantiomers and the rate of conversion during oxidation from cystine and cysteine into cysteic acid was determined. Racemization of L-cysteine was not significant during oxidation with performic acid and the process can, therefore, be applied before hydrolysis during quantification of enantiomers of these compounds. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Determination of phosphoric acid triesters in human plasma using solid-phase microextraction and gas chromatography coupled to inductively coupled plasma mass spectrometry

A simple and sensitive method for determination of phosphoric acid triesters at trace levels in human plasma sample is described. In this work, solid-phase microextraction (SPME) is employed as a sample preparation procedure for extraction and pre-concentration of alkyl and aryl phosphates followed by gas chromatography coupled to inductively coupled plasma mass spectrometry (GC-ICP-MS) for phosphorus-specific and very sensitive determination of these compounds in human plasma. The detection limits from blood plasma were 50 ngL(-1) (tripropyl phosphate), 17 ngL(-1) (tributyl phosphate), 240 ngL(-1) (tris(2-chloroethyl) phosphate) and 24 ngL(-1) (triphenyl phosphate). Sample preparation involves plasma deproteinization followed by direct immersion SPME with 65 microm poly(dimethylsiloxane/divinylbenzene) fiber. Extraction was performed at 40 degrees C for 30 min and at pH 7.0 in 10 mM sodium carbonate buffer. The reported method, to our knowledge, describes the first application of SPME with element-specific detection for analysis of phosphoric acid esters. Application of the method to the plasma samples, previously stored in poly(vinyl chloride) plasma bags revealed the presence of triphenyl phosphate, which was further confirmed by SPME GC time-of-flight high-resolution mass spectrometry.     

固相微萃取活性炭涂层萃取头的制备及其对卤代烃化合物的萃取

利用自制的有机硅树脂胶粘剂和粉状活性炭制成活性炭涂层萃取头。该萃取头富集能力强,对氯仿、四氯化碳、三氯乙烯、四氯乙烯4种卤代烃化合物的富集率达到13.8~18.7倍;热稳定性好,最高使用温度可达290 ℃;使用寿命长,250 ℃解吸条件下可反复使用140次以上。上述4种化物固相微萃取-气相色谱分析的结果表明,方法的最低检出质量浓度为0.008~0.05 μg/L。采用该萃取头对含有该4种卤代烃化合物的实际水样进行了SPME-GC分析,4种化合物的回收率为95.5%~104.6%。     

New approach based on solid-phase microextraction to estimate polydimethylsiloxane fibre coating-water distribution coefficients for brominated flame retardants

A depletion solid-phase microextraction (SPME) method based on multiple SPME extraction was applied to estimate fibre coating-water distribution constants (Kfs) of brominated flame retardants. Several polybrominated diphenyl ethers (PBDEs) including compounds present in the commercial mixture "Pentamix", and two polybrominated biphenyls (PBBs) were considered as target analytes. One hundred-micrometer poly(dimethylsiloxane) (PDMS) coating fibre was selected to estimate partition coefficients. SPME kinetics studies at 25 and 100 degrees C were performed. Kfs values obtained at both temperatures for brominated flame retardants were compared with the corresponding octanol-water partition coefficients (Kow) values found in literature. A linear log-log relationship between Kow with Kfs was found. To the best of our knowledge, this is the first study where brominated flame retardants Kfs values are estimated.     

Optimization of headspace solid-phase microextraction for the analysis of specific flavors in enzyme modified and natural Cheddar cheese using factorial design and response surface methodology

A headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC/MS) method was developed using experimental designs to quantify the flavor of commercial Cheddar cheese and enzyme-modified Cheddar cheese (EMCC). Seven target compounds (dimethyl disulfide, hexanal, hexanol, 2-heptanone, ethyl hexanoate, heptanoic acid, delta-decalactone) representative of different chemical families frequently present in Cheddar cheese were selected for this study. Three types of SPME fibres were tested: Carboxen/polydimethylsiloxane (CAR/PDMS), polyacrylate (PA) and Carbowax/divinylbenzene (CW/DVB). NaCl concentration and temperature, as well as extraction time were tested for their effect on the HS-SPME process. Two series of two-level full factorial designs were carried out for each fibre to determine the factors which best support the extraction of target flavors. Therefore, central composite designs (CCDs) were performed and response surface models were derived. Optimal extraction conditions for all selected compounds, including internal standards, were: 50 min at 55 degrees C in 3M NaCl for CAR/PDMS, 64 min at 62 degrees C in 6M NaCl for PA, and 37 min at 67 degrees C in 6M NaCl for CW/DVB. Given its superior sensitivity, CAR/PDMS fibre was selected to evaluate the target analytes in commercial Cheddar cheese and EMCC. With this fibre, calibration curves were linear for all targeted compounds (from 0.5 to 6 microg g(-1)), except for heptanoic acid which only showed a linear response with PA fibres. Detection limits ranged from 0.3 to 1.6 microg g(-1) and quantification limits from 0.8 to 3.6 microg g(-1). The mean repeatability value for all flavor compounds was 8.8%. The method accuracy is satisfactory with recoveries ranging from 97 to 109%. Six of the targeted flavors were detected in commercial Cheddar cheese and EMCC.