Use of solid-phase microextraction to detect and quantify gas-phase dicarbonyls in indoor environments

Solid-phase microextraction (SPME) was evaluated for the detection and quantification of the gas-phase dicarbonyls, glyoxal (GLY) and methylglyoxal (MGLY). Additionally, polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), and carbowax/divinylbenzene (CW/DVB) fibers were tested to determine the optimum fiber for detection of these species. GLY and MGLY were derivatized with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PFBHA), extracted with SPME from headspace or bag chamber and then analyzed by GC/MS. The PDMS/DVB SPME fiber for on-fiber derivatization and subsequent sampling for gas-phase methylglyoxal provided the optimum combination of analytical reproducibility and sensitivity. Linearity of the calibration curve was achieved across a range of 11-222 microg/m(3) (4-75 ppb).     

Determination of diphenylether herbicides in water samples by solid-phase microextraction coupled to liquid chromatography

Solid-phase microextraction (SPME) coupled to LC for the analysis of five diphenylether herbicides (aclonifen, bifenox, fluoroglycofen-ethyl, oxyfluorfen, and lactofen) is described. Various parameters of extraction of analytes onto the fiber (such as type of fiber, extraction time and temperature, pH, impact of salt and organic solute) and desorption from the fiber in the desorption chamber prior to separation (such as type and composition of desorption solvent, desorption mode, soaking time, and flush-out time) were studied and optimized. Four commercially available SPME fibers were studied. PDMS/divinylbenzene (PDMS/DVB, 60 microm) and carbowax/ templated resin (CW/TPR, 50 microm) fibers were selected due to better extraction efficiencies. Repeatability (RSD, < 7%), correlation coefficient (> 0.994), and detection limit (0.33-1.74 and 0.22-1.94 ng/mL, respectively, for PDMS/DVB and CW/TPR) were investigated. Relative recovery (81-104% for PDMS/DVB and 83-100% for CW/TPR fiber) values have also been calculated. The developed method was successfully applied to the analysis of river water and water collected from a vegetable garden.     

Determination of phthalates and adipate in bottled water by headspace solid-phase microextraction and gas chromatography/mass spectrometry

The performance of three fibres for the headspace solid-phase microextraction (SPME) of di-2-ethylhexyl adipate (DEHA) and eight phthalates in water was investigated systematically under different extraction conditions. Good responses on the 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) SPME fibre were observed for DEHA and all phthalates. The polydimethylsiloxane (PDMS) SPME fibre had very poor responses for the lighter and slightly polar phthalates, dimethyl phthalate (DMP) and diethyl phthalate (DEP), while the divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) SPME fibre had very poor responses for the heavier and non-polar adipate and phthalates. The salt (NaCl) was found to increase the partitioning of DMP, DEP, diisobutyl phthalate (DiBP), di-n-butyl phthalate, and benzyl butyl phthalate (BBP) from water into the headspace, while partitioning of heavier adipate and phthalates from water into headspace was suppressed when the concentration of NaCl was above 10%. The automated headspace SPME methods were developed and validated under two different salting conditions (30% NaCl for DMP, DEP and BBP, and 10% for DEHA, DiBP, DBP, di-n-hexyl phthalate (DHP), di-2-ethylhexyl phthalate (DEHP), and di-n-octyl phthalate (DOP)). Linearity with R(2) values better than 0.9949 was observed for DEHA and eight phthalates over the range from 0.1 to 20 microg L(-1). Method detection limits ranged from 0.003 microg L(-1) for DOP to 0.085 microg L(-1) for BBP. Good repeatability was observed for DEHA and most phthalates with relative standard deviation (RSD) values less than 10%. The methods were used to analyse bottled water samples for DEHA and eight phthalates. DMP, DHP, BBP, DEHA and DOP were not detected in any samples. Concentrations of the other phthalates were low (around sub-ppb) except for DBP in the water from a polycarbonate bottle at 1.72 microg L(-1).     

Analysis of triazine in water samples by solid-phase microextraction coupled with high-performance liquid chromatography

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) for the determination of triazine is described. Carbowax/templated resin (CW/TPR, 50 μm), polydimethylsiloxane/divinylbenzene (PDMS/DVB, 60 μm), polydimethylsiloxane (PDMS, 100 μm), and polyacrylate (PA, 85 μm) fibers were evaluated for extraction of the triazines. CW/TPR and PDMS/DVB fibers were selected for further study. Several parameters of the extraction and desorption procedure were studied and optimized (such as types of fibers, desorption mode, desorption time, compositions of solvent for desorption, soaking periods and the flow rate during desorption period, extraction time, temperature, pH, and ionic strength of samples). Both CW/TPR and PDMS/DVB fibers are acceptable; a simple calibration-curve method based on simple aqueous standards can be used. The linearity of this method for analyzing standard solution has been investigated over the range 5-1000 ng mL⁻¹ for both PDMS/DVB and CW/TPR fibers. All the correlation coefficients in the range 5-1000 ng mL⁻¹ were better than 0.995 except Simazine and Atratone by CW/TPR fiber. The R.S.D.s range from 4.4% to 8.8 % (PDMS/DVB fiber) and from 2.4% to 7.2% (CW/TPR fiber). Method-detection limits (MDL) are in the range 1.2-2.6 and 2.8-3.4 ng mL⁻¹ for the two fibers. These methods were applied to the determination of trazines in environmental water samples (lake water).     

Optimization of headspace solid phase microextraction for gas chromatography/mass spectrometry analysis of widely different volatility and polarity terpenoids in olibanum

The aim of this study was the optimization of headspace SPME conditions for trapping diterpenes present in frankincense (olibanum). Diterpenes like cembrenes or incensole and its derivatives are characteristic of olibanum. So in order to detect by SPME the occurrence of olibanum in archeological objects, it appears essential to have the best extraction conditions for these diterpenes that will be in very small quantities. Both sampling time and extraction temperature were studied and five fiber coatings were tested: polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), carboxen/polydimethylsiloxane (CAR/PDMS), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) and carbowax/divinylbenzene (CW/DVB). The PDMS/DVB fiber was found to be the most efficient for trapping olibanum characteristic diterpenes, with a sampling time of 1 h and a sampling temperature of 80 degrees C.     

Optimization of the extraction conditions of the volatile compounds from chili peppers by headspace solid phase micro-extraction

A method involving headspace-solid phase micro-extraction (HS-SPME), gas chromatography with flame ionization detection (GC-FID) and gas chromatography with mass spectrometry (GC-MS) was developed and optimized to investigate the volatile composition of Capsicum chili peppers. Five SPME fibers were tested for extraction: carboxen/polydimethylsiloxane (CAR/PDMS-75μm), polydimethylsiloxane (PDMS-100μm), divinylbenzene/polydimethylsiloxane (DVB/PDMS-65μm), carbowax/divinylbenzene (CW/DVB-70μm), and divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS-50/30μm), the last of which was shown to be the most efficient fiber to trap the volatile compounds. Optimization of the extraction conditions was carried out using multivariate strategies such as factorial design and response surface methodology. Eighty three compounds were identified by GC-MS when using the optimized extraction conditions, the majority of which were esters.     

Evaluation of headspace solid-phase microextraction for analysis of phosphine residues in wheat

In headspace (HS) analysis, a fumigant is released from a commodity into a gas-tight container by grinding, heating, or microwaves. A new technique uses HS-solid-phase microextraction (SPME) for additional preconcentration of fumigant. HS-SPME was tested for detection of phosphine (PH3), chosen for examination because of its wide use on stored commodities. PH3 was applied to 50 g wheat in separate 250 mL sealed flasks, which were equipped either with a septum for conventional HS analysis or with one of four HS-SPME fibers [100 microm polydimethylsiloxane (PDMS), 85 microm carboxen (CAR)/PDMS, 75 microm CAR/PDMS, and 65 pm PDMS/divinylbenzene (DVB)]. The wheat was heated at 45 degrees C for 20 min. In conventional HS analysis, a gaseous aliquot (80 pL) was taken from the HS and injected into the GC instrument. In the HS-SPME procedure, the fiber was removed from the HS and exposed in the heated injection port of the GC instrument. In all cases, PH3 was determined under the same chromatographic conditions with a GC pulsed flame photometric detector. In a comparison of the efficacy of the fibers, the bipolar fibers (CAR/PDMS and PDMS/DVB) contained more PH3 than the aliquot in the conventional HS analysis; larger size bipolar fibers extracted PH3 more efficiently than smaller fibers (e.g., 85 > 75 > 65 microm). The nonpolar fiber (PDMS) contained no PH3. Four fortification levels of PH3 on wheat were tested: 0.01, 0.05, 0.1, and 0.3 microg/g. The response of each bipolar fiber increased with the fortification levels, but the conventional HS analysis detected no fumigant at the lowest fortification level of 0.01 mg/g. Under the conditions of the validation study, the LOD was in the range of 0.005-0.01 ng PH3/g wheat.     

Evaluation of solid-phase micro-extraction coupled to gas chromatography-mass spectrometry for the headspace analysis of volatile compounds in cocoa products

The aroma profile of cocoa products was investigated by headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS). SPME fibers coated with 100 μm polydimethylsiloxane coating (PDMS), 65 μm polydimethylsiloxane/divinylbenzene coating (PDMS-DVB), 75 μm carboxen/polydimethylsiloxane coating (CAR-PDMS) and 50/30 μm divinylbenzene/carboxen on polydimethylsiloxane on a StableFlex fiber (DVB/CAR-PDMS) were evaluated. Several extraction times and temperature conditions were also tested to achieve optimum recovery. Suspensions of the samples in distilled water or in brine (25% NaCl in distilled water) were investigated to examine their effect on the composition of the headspace. The SPME fiber coated with 50/30 μm DVB/CAR-PDMS afforded the highest extraction efficiency, particularly when the samples were extracted at 60 °C for 15 min under dry conditions with toluene as an internal standard. Forty-five compounds were extracted and tentatively identified, most of which have previously been reported as odor-active compounds. The method developed allows sensitive and representative analysis of cocoa products with high reproducibility. Further research is ongoing to study chocolate making processes using this method for the quantitative analysis of volatile compounds contributing to the flavor/odor profile.     

Rapid screening of precursor and degradation products of chemical warfare agents in soil by solid-phase microextraction ion mobility spectrometry (SPME-IMS)

The use of solid-phase microextraction (SPME) coupled to ion mobility spectrometry (IMS) to detect precursor and degradation products of chemical warfare agents (CWAs) as soil contaminants was investigated. The development and characterization of a system to interface a thermal desorption solid-phase microextraction inlet with a hand held ion mobility spectrometer was demonstrated. The analytes used in this study were diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP), and dimethyl methylphosphonate (DMMP). Two SPME fibers with different stationary phases, 100 μm polydimethylsiloxane (PDMS) and 65 μm polydimethylsiloxane divinylbenzene (PDMS/DVB), were evaluated in this study to determine the optimal fiber and extraction conditions. Better results were obtained with the PDMS fiber. SPME-IMS offered good repeatability and detection of the precursor and degradation products in spiked soil at concentrations as low as 10 μg/g. Sample analysis time was less than 30 min for all the precursor and degradation products.     

Enantiomeric monoterpene emissions from natural and damaged Scots pine in a boreal coniferous forest measured using solid-phase microextraction and gas chromatography/mass spectrometry

In order to develop a valuable method for accurate screening of biogenic emissions from undisturbed living plants or for plant-insect interactions, solid-phase microextraction (SPME) has been combined with dynamic branch enclosure cuvettes and enantioselective GC/MS. The study was conducted at Hyyti?l? forest station, Finland within a boreal coniferous forest dominated by Scots pine (Pinus sylvestris). The SPME method was optimized for monoterpenes by testing three fibre coatings: polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB) and carbowax/divinylbenzene (CW/DVB) and determining the optimum exposure time. The PDMS/DVB fibre was found to be most suitable and was used to characterize emissions of P. sylvestris enclosed in dynamic branch enclosure cuvettes by exposure for 1 min followed by desorption and separation on a beta-cyclodextrin column installed in the GC/MS oven. Dynamic cuvette measurements have been compared to static headspace SPME samples of the emission of detached needles from the same tree species and a portable dynamic air sampler (PDAS)-SPME for sampling the ambient air around the same trees. The method developed has allowed an accurate characterization of the gaseous emission of P. sylvestris and the identification of 17 isoprenoids comprising chiral and achiral monoterpenes. Two chemotypes of Scots pine can be differentiated through their emission of (+)-delta-3-carene. While SPME-dynamic cuvette, portable dynamic sampler and absorbent results agreed well, significant differences in enantiomeric ratios were observed in natural emissions and those of damaged leaves. Therefore, in enantioselective studies of plant-insect and/or plant-plant interactions, the two enantiomers of a given monoterpene should be treated as two separate substances.     

Fiber introduction mass spectrometry: determination of pesticides in herbal infusions using a novel sol-gel PDMS/PVA fiber for solid-phase microextraction

An application of the direct coupling of solid-phase microextraction (SPME) with mass spectrometry (MS), a technique known as fiber introduction mass spectrometry (FIMS), is described to determine organochlorine (OCP) and organophosphorus (OPP) pesticides in herbal infusions of Passiflora L. A new fiber coated with a composite of poly(dimethylsiloxane) and poly(vinyl alcohol) (PDMS/PVA) was used. Sensitive, selective, simple and simultaneous quantification of several OCP and OPP was achieved by monitoring diagnostic fragment ions of m/z 266 (chlorothalonil), m/z 195 (alpha-endosulfan), m/z 278 (fenthion), m/z 263 (methyl parathion) and m/z 173 (malathion). Simple headspace SPME extraction (25 min) and fast FIMS detection (less than 40 s) of OCP and OPP from a highly complex herbal matrix provided good linearity with correlation coefficients of 0.991-0.999 for concentrations ranging from 10 to 140 ng ml(-1) of each compound. Good accuracy (80 to 110%), precision (0.6-14.9%) and low limits of detection (0.3-3.9 ng ml(-1)) were also obtained. Even after 400 desorption cycles inside the ionization source of the mass spectrometer, no visible degradation of the novel PDMS/PVA fiber was detected, confirming its suitability for FIMS. Fast (ca 20 s) pesticide desorption occurs for the PDMS/PVA fiber owing to the small thickness of the film and its reduced water sorption.     

Fiber introduction mass spectrometry: determination of pesticides in herbal infusions using a novel sol-gel PDMS/PVA fiber for solid-phase microextraction

An application of the direct coupling of solid-phase microextraction (SPME) with mass spectrometry (MS), a technique known as fiber introduction mass spectrometry (FIMS), is described to determine organochlorine (OCP) and organophosphorus (OPP) pesticides in herbal infusions of Passiflora L. A new fiber coated with a composite of poly(dimethylsiloxane) and poly(vinyl alcohol) (PDMS/PVA) was used. Sensitive, selective, simple and simultaneous quantification of several OCP and OPP was achieved by monitoring diagnostic fragment ions of m/z 266 (chlorothalonil), m/z 195 (alpha-endosulfan), m/z 278 (fenthion), m/z 263 (methyl parathion) and m/z 173 (malathion). Simple headspace SPME extraction (25 min) and fast FIMS detection (less than 40 s) of OCP and OPP from a highly complex herbal matrix provided good linearity with correlation coefficients of 0.991-0.999 for concentrations ranging from 10 to 140 ng ml(-1) of each compound. Good accuracy (80 to 110%), precision (0.6-14.9%) and low limits of detection (0.3-3.9 ng ml(-1)) were also obtained. Even after 400 desorption cycles inside the ionization source of the mass spectrometer, no visible degradation of the novel PDMS/PVA fiber was detected, confirming its suitability for FIMS. Fast (ca 20 s) pesticide desorption occurs for the PDMS/PVA fiber owing to the small thickness of the film and its reduced water sorption.     

Selected ion storage versus tandem MS/MS for organochlorine pesticides determination in drinking waters with SPME and GC-MS

The use of two modes for mass spectrometry (MS) detection with an ion trap instrument, selected ion storage (SIS) and tandem mass spectrometry (MS/MS), are compared for the solid-phase microextraction (SPME)–gas chromatography (GC) coupled to mass spectrometry (GC-MS) determination of 16 priority organochlorine pesticides (OCPs) in drinking water samples at the ultratrace levels (ng?L^?1) required by official guidelines in the European legislation. Experimental parameters investigated for the SPME sample preparation were: the type of coating (100?µm polydimethylsiloxane, PDMS, and 65?µm poly(dimethylsiloxane)–divinylbenzene, PDMS/DVB), SPME modality, extraction and desorption times and desorption temperature and the methanol percentage in the SPME working solution. Under the calculated optimal conditions two methodologies were developed, one for SIS and the other for MS/MS modes. The detection limits, precision and accuracy were evaluated for both alternatives and were appropriate to the official guidelines requirements. The SPME–GC-MS(SIS) methodology offered LODs from 0.2–6.6?ng?L^?1, precision below 13% and recoveries between 83 and 110%. The SPME–GC–MS/MS methodology provided limits of detection (LODs) ranging from 0.3 to 7.6 ng?L^?1, % RSD were ≤14% and recoveries of 79–108% were achieved. After the results observed within an Interlaboratory Exercise, the latest MS methodology was selected for the pursued analysis in real drinking water samples. Also, the good results in this round-robin exercise validate the proposed SPME–GC–MS/MS methodology.     

Determination of diisopropylfluorophosphate in rat plasma and brain tissue by headspace solid-phase microextraction gas chromatography/mass spectrometry

A simple, sensitive and rapid method for the determination of diisopropylfluorophosphate (DFP) in rat plasma and brain tissue using headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) is presented. A 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was selected for sampling. The main parameters affecting the SPME process such as extraction and desorption temperature, extraction and desorption time, salt addition, and fiber preheating time were optimized in each matrix to enhance the extraction efficiency of the method. The lower limits of quantitation for DFP in plasma and brain tissue were 1 ng/mL and 3 ng/g, respectively. The method showed good linearity over the range from 1-100 ng/mL in plasma and 3-300 ng/g in brain tissue with correlation coefficient (R(2)) values higher than 0.995. The precision and accuracy for intra-day and inter-day were less than 10%. The relative recoveries in plasma and brain for DFP were greater than 50%. Stability tests including autosampler and freeze and thaw were also investigated. This validated method was successfully applied to study the neurobehavioral effects of low-level organophosphate exposures. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Highly porous solid-phase microextraction fiber coating based on poly(ethylene glycol)-modified ormosils synthesized by sol-gel technology

The preparation and characteristics of solid-phase microextraction (SPME) fibers coated with Carbowax 20M ormosil (organically modified silica) are described here. Raw fused silica fibers were coated with Carbowax 20M-modified silica using sol-gel process. Scanning electron micrographs of fibers revealed a highly porous, sponge-like coating with an average thickness of (8 +/- 1) microm. The sol-gel Carbowax fibers were compared to commercial fibers coated with 100 microm polydimethylsiloxane (PDMS) and 65 microm Carbowax-divinylbenzene (DVB). Shorter equilibrium times were possible with the sol-gel Carbowax fiber: for headspace extraction of the test analytes, they ranged from less than 3 min for benzene to 15 min for o-xylene. Extraction efficiencies of the sol-gel Carbowax fiber were superior to those of conventional fibers: for o-xylene, the extracted masses were 230 and 540% of that obtained with 100 microm PDMS and 65 microm Carbowax-DVB fibers, respectively.     

Application of solid-phase microextraction for determination of pyrethroids in groundwater using liquid chromatography with post-column photochemically induced fluorimetry derivatization and fluorescence detection

Solid-phase microextraction (SPME) is a rapid and simple analytical technique which uses coated fused-silica fibers to extract analytes from aqueous samples. This study develops a method of SPME analysis for seven pyrethroids, including fenpropathrin, lambda-cyhalothrin, deltamethrin, fenvalerate, permethrin, tau-fluvalinate and bifenthrin in groundwater samples using high performance liquid chromatography combined with post-column photochemically induced fluorimetry derivatization and fluorescence detection (SPME-LC-PIF-FD). To perform the SPME, a 60 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used for the extraction of the pesticides from groundwater samples. The main factors affecting the SPME process, such as extraction time, stirring rate, extraction temperature, pH and the desorption process were studied. The use of photochemically induced fluorescence for detection improved sensitivity and selectivity. The limits of quantification (LOQs) obtained in the matrix, with respect to EURACHEM Guidance, varied between 0.03 and 0.075 microgL(-1). Relative recoveries ranged from 92 to 109% and relative standard deviations values ranged from 2 to 9%.     

Study of the effect of different fiber coatings and extraction conditions on dry cured ham volatile compounds extracted by solid-phase microextraction (SPME)

Extraction of dry cured ham volatile compounds by solid-phase microextraction (SPME) was optimized. Different fiber coatings (carboxen/polydimethylsiloxane (CAR/PDMS), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB)), times of extraction (15, 30, 60 min) and sample preparation (ground samples and homogenates with NaCl saturated solution) were assayed. CAR/PDMS and DVB/CAR/PDMS fiber coatings extracted more than 100 volatile compounds and showed the highest area counts for most volatile compounds. CAR/PDMS coating extracted better those compounds whose Kovats index (KI) was lower than 980 (on average) and DVB/CAR/PDMS those with higher KI. Fifteen minutes of extraction provided a volatile compound profile with lower area counts for most compounds and qualitatively different to that obtained with 30 and 60 min of extraction. Homogenates gave a different profile compared to ground samples, with lower total counts for most compounds but higher proportion of aldehydes, and presence of several compounds not found in ground samples.     

Screening of volatile composition from Portuguese multifloral honeys using headspace solid-phase microextraction-gas chromatography-quadrupole mass spectrometry

The volatile composition from four types of multifloral Portuguese (produced in Madeira Island) honeys was investigated by a suitable analytical procedure based on dynamic headspace solid-phase microextraction (HS-SPME) followed by thermal desorption gas chromatography-quadrupole mass spectrometry detection (GC-qMS). The performance of five commercially available SPME fibres: 100 μm polydimethylsiloxane, PDMS; 85 μm polyacrylate, PA; 50/30 μm divinylbenzene/carboxen on polydimethylsiloxane, DVB/CAR/PDMS (StableFlex); 75 μm carboxen/polydimethylsiloxane, CAR/PDMS, and 65 μm carbowax/divinylbenzene, CW/DVB; were evaluated and compared. The highest amounts of extract, in terms of the maximum signal obtained for the total volatile composition, were obtained with a DVB/CAR/PDMS coating fibre at 60 °C during an extraction time of 40 min with a constant stirring at 750 rpm, after saturating the sample with NaCl (30%). Using this methodology more than one hundred volatile compounds, belonging to different biosynthetic pathways were identified, including monoterpenols, C₁₃-norisoprenoids, sesquiterpenes, higher alcohols, ethyl esters and fatty acids. The main components of the HS-SPME samples of honey were in average ethanol, hotrienol, benzeneacetaldehyde, furfural, trans-linalool oxide and 1,3-dihydroxy-2-propanone.     

Analysis of carbamate and phenylurea pesticide residues in fruit juices by solid-phase microextraction and liquid chromatography-mass spectrometry

A new analysis method to detect carbamates and phenylurea pesticide residues in fruit juices was developed using solid-phase microextraction (SPME) coupled with liquid chromatography-single quadrupole mass spectrometry (LC/MS) and liquid chromatography-quadrupole ion trap mass spectrometry (LC/QIT-MS). The pesticide residues present in watery matrices as fruit juices were extracted using three types of fibers: 50-microm Carbowax/templated resin (CW/TPR), 60-mum poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) and 85-microm polyacrylate. The different extraction conditions were evaluated choosing as the best parameters 90 min (time), 20 degrees C (temperature) and 1 ml (volume). After extraction, the desorption (in a static mode) was performed in the specific interface chamber SPME/HPLC, previously filled with 70% methanol and 30% water. The best recoveries, evaluated at two fortification levels (0.2 and 0.5 mg kg(-1)) in fruit juices, were obtained using PDMS/DVB and CW/TPR fibers, and ranged from 25 to 82% (monolinuron, diuron and diethofencarb), with relative standard deviations (RSDs) from 1 to 17%. All the limits of quantification (LOQs) were in the range of 0.005-0.05 microg ml(-1) and, in any case, equal to, or lower than, maximum residue limits (MRLs) established by Italian and Spanish legislations. The mass spectrometry analyses were carried out using an electrospray ionization (ESI) source operating in the positive mode both for single quadrupole and for QIT mass analysers, operating in selected ion monitoring (SIM) and in multiple reaction monitoring (MRM) modes, respectively. The proposed new method can be applied to the determination of selected pesticides in real samples of fruit juices.     

Preparation and Characterization of Prometryn Molecularly Imprinted Solid‐Phase Microextraction Fibers

Abstract

A novel reproducible solid‐phase microextraction (SPME) coating was prepared on the surface of silanized silica fibers by molecularly imprinted polymerization using prometryn as template molecule. The structure and extraction performance of molecularly imprinted polymer (MIP) coating was studied with the scanning electron microscope and high performance liquid chromatography (HPLC). Specific selectivity was found with the prometryn MIP‐coated fiber to prometry and its structural analogues such as atrazine, simetryn, terbutylazin, ametryn, propazine and terbutryn. In contrast, these triazines could not be selectively extracted by the non‐imprinted polymer fiber or commercial polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), polyacrylate (PA) fibers.