Electrochemically controlled in-tube solid phase microextraction

We report a new in-tube solid phase microextraction approach named electrochemically controlled in-tube solid phase microextraction (EC in-tube SPME). This approach, which combined electrochemistry and in-tube SPME, led to decrease in total analysis time and increase in sensitivity. At first, pyrrole was elctropolymerized on the inner surface of a stainless steel tube. Then, the polypyrrole (PPy)-coated in-tube SPME was coupled on-line to liquid chromatography (HPLC) to achieve automated in-tube SPME–HPLC analysis. After the completion of EC-in-tube SPME–HPLC setup, the PPy-coated tube was used as working electrode for uptake of diclofenac as target analyte. Extraction ability of the tube in presence and in absence of applied electrical field was investigated. It was found that, under the same extraction conditions, the extraction efficiency could be greatly enhanced by using the constant potential. Important factors are also optimized. The detection limit (S/N = 3) and precision were 0.1 μg L⁻¹ and 4.4%, respectively.     

Preparation and evaluation of a novel molecularly imprinted polymer coating for selective extraction of indomethacin from biological samples by electrochemically controlled in-tube solid phase microextraction

In the present work, an automated on-line electrochemically controlled in-tube solid-phase microextraction (EC-in-tube SPME) coupled with HPLC-UV was developed for the selective extraction and preconcentration of indomethacin as a model analyte in biological samples. Applying an electrical potential can improve the extraction efficiency and provide more convenient manipulation of different properties of the extraction system including selectivity, clean-up, rate, and efficiency. For more enhancement of the selectivity and applicability of this method, a novel molecularly imprinted polymer coated tube was prepared and applied for extraction of indomethacin. For this purpose, nanostructured copolymer coating consisting of polypyrrole doped with ethylene glycol dimethacrylate was prepared on the inner surface of a stainless-steel tube by electrochemical synthesis. The characteristics and application of the tubes were investigated. Electron microscopy provided a cross linked porous surface and the average thickness of the MIP coating was 45 μm. Compared with the non-imprinted polymer coated tubes, the special selectivity for indomethacin was discovered with the molecularly imprinted coated tube. Moreover, stable and reproducible responses were obtained without being considerably influenced by interferences commonly existing in biological samples. Under the optimal conditions, the limits of detection were in the range of 0.07–2.0 μg L⁻¹ in different matrices. This method showed good linearity for indomethacin in the range of 0.1–200 μg L⁻¹, with coefficients of determination better than 0.996. The inter- and intra-assay precisions (RSD%, n = 3) were respectively in the range of 3.5–8.4% and 2.3–7.6% at three concentration levels of 7, 70 and 150 μg L⁻¹. The results showed that the proposed method can be successfully applied for selective analysis of indomethacin in biological samples.     

Determination of polycyclic aromatic hydrocarbons in food samples by automated on-line in-tube solid-phase microextraction coupled with high-performance liquid chromatography-fluorescence detection

A simple and sensitive automated method, consisting of in-tube solid-phase microextraction (SPME) coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD), was developed for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in food samples. PAHs were separated within 15 min by HPLC using a Zorbax Eclipse PAH column with a water/acetonitrile gradient elution program as the mobile phase. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a CP-Sil 19CB capillary column as an extraction device. Low- and high-molecular weight PAHs were extracted effectively onto the capillary coating from 5% and 30% methanol solutions, respectively. The extracted PAHs were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME HPLC-FLD method, good linearity of the calibration curve (r > 0.9972) was obtained in the concentration range of 0.05–2.0 ng/mL, and the detection limits (S/N = 3) of PAHs were 0.32–4.63 pg/mL. The in-tube SPME method showed 18–47 fold higher sensitivity than the direct injection method. The intra-day and inter-day precision (relative standard deviations) for a 1 ng/mL PAH mixture were below 5.1% and 7.6% (n = 5), respectively. This method was applied successfully to the analysis of tea products and dried food samples without interference peaks, and the recoveries of PAHs spiked into the tea samples were >70%. Low-molecular weight PAHs such as naphthalene and pyrene were detected in many foods, and carcinogenic benzo[a]pyrene, at relatively high concentrations, was also detected in some black tea samples. This method was also utilized to assess the release of PAHs from tea leaves into the liquor.     

Selective molecularly imprinted polymer combined with restricted access material for in-tube SPME/UHPLC-MS/MS of parabens in breast milk samples

A new molecularly imprinted polymer modified with restricted access material (a hydrophilic external layer), (MIP-RAM) was synthesized via polymerization in situ in an open fused silica capillary. This stationary phase was used as sorbent for in-tube solid phase microextraction (in-tube SPME) to determine parabens in breast milk samples by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Scanning electron micrographs (SEM) illustrate MIP surface modification after glycerol dimethacrylate (hydrophilic monomer) incorporation. The interaction between parabens and MIP-RAM was investigated by Fourier-transform infrared (FTIR) spectroscopy. The Scatchard plot for MIP-RAM presented two linear parts with different slopes, illustrating binding sites with high- and low-affinity. Endogenous compounds exclusion from the MIP-RAM capillary was demonstrated by in-tube SPME/LC-UV assays carried out with blank milk samples. The in-tube SPME/UHPLC-MS/MS method presented linear range from 10 ng mL⁻¹ (LLOQ) to 400 ng mL⁻¹ with coefficients of determination higher than 0.99, inter-assay precision with coefficient of variation (CV) values ranging from 2 to 15%, and inter-assay accuracy with relative standard deviation (RSD) values ranging from −1% to 19%. Analytical validation parameters attested that in-tube SPME/UHPLC-MS/MS is an appropriate method to determine parabens in human milk samples to assess human exposure to these compounds. Analysis of breast milk samples from lactating women demonstrated that the proposed method is effective.     

Determination of patulin in fruit juice and dried fruit samples by in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive method for the determination of patulin in fruit juice and dried fruit samples was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Patulin was separated within 5 min by high-performance liquid chromatography using a Synergi MAX-RP 80A column and water/acetonitrile (80/20, v/v) as the mobile phase. Electrospray ionization conditions in the negative ion mode were optimized for MS detection of patulin. The pseudo-molecular ion [M−H]⁻ was used to detect patulin in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Carboxen 1006 PLOT capillary column as an extraction device. The extracted patulin was readily desorbed from the capillary by passage of the mobile phase, and no carry-over was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve (r = 0.9996) was obtained in the concentration range of 0.5–20 ng/mL using ¹³C₃-patulin as an internal standard, and the detection limit (S/N = 3) of patulin was 23.5 pg/mL. The in-tube SPME method showed >83-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) were below 0.8% and 5.0% (n = 6), respectively. This method was applied successfully for the analysis of fruit juice and dried fruit samples without interference peaks. The recoveries of patulin spiked into apple juice were >92%, and the relative standard deviations were <4.5%. Patulin was detected at ng/mL levels in various commercial apple juice samples.     

Analysis of polar pesticides in water and wine samples by automated in-tube solid-phase microextraction coupled with high-performance liquid chromatography-mass spectrometry

A simple and sensitive method for the determination of polar pesticides in water and wine samples was developed by coupling automated in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ESI-MS detection were investigated. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, especially the stationary phases used for SPME. For the compounds studied, a custom-made polypyrrole (PPY)-coated capillary showed superior extraction efficiency as compared to several commercial capillaries tested, and therefore, it was selected for in-tube SPME. The influence of the ethanol content on the performance of in-tube SPME was also investigated. It was found that the amount of pesticides extracted decreased with the increase of ethanol content in the solutions. The ESI-MS detection conditions were optimized as follows: nebulizer gas, N2 (30 p.s.i.; 1 p.s.i.=6894.76 Pa); drying gas, N2 (10 l/min, 350 degrees C); capillary voltage, 4500 V; ionization mode, positive; mass scan range, 50-350 amu; fragmentor voltage, variable depending on the ions selected. Due to the high extraction efficiency of the PPY coating and the high sensitive mass detection, the detection limits (S/N = 3) of this method for the compounds studied are in the range of 0.01 to 1.2 ng/ml, which are more than one order of magnitude lower than those of the previous in-tube SPME-HPLC-UV method. A linear relationship was obtained for each analyte in the concentration range of 0.5 to 200 ng/ml with MS detection. This method was applied to the analysis of phenylurea and carbamate pesticides in spiked water and wine samples.     

Determination of aflatoxins in food samples by automated on-line in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive automated method for determination of aflatoxins (B1, B2, G1, and G2) in nuts, cereals, dried fruits, and spices was developed consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Aflatoxins were separated within 8 min by high-performance liquid chromatography using a Zorbax Eclipse XDB-C8 column with methanol/acetonitrile (60/40, v/v): 5 mM ammonium formate (45:55) as the mobile phase. Electrospray ionization conditions in the positive ion mode were optimized for MS detection of aflatoxins. The pseudo-molecular ions [M+H]⁺ were used to detect aflatoxins in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted aflatoxins were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve (r > 0.9994) was obtained in the concentration range of 0.05–2.0 ng/mL using aflatoxin M1 as an internal standard, and the detection limits (S/N = 3) of aflatoxins were 2.1–2.8 pg/mL. The in-tube SPME method showed >23-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) at the concentration of 1 ng/mL aflatoxin mixture were below 3.3% and 7.7% (n = 5), respectively. This method was applied successfully to analysis of food samples without interference peaks. The recoveries of aflatoxins spiked into nuts and cereals were >80%, and the relative standard deviations were <11.2%. Aflatoxins were detected at <10 ng/g in several commercial food samples.     

Separation and determination of selenium in water samples by the combination of APDC coprecipitation: X-ray fluorescence spectrometry

A sensitive and non chromatographic analytical procedure for the separation of inorganic selenium species in natural water has been performed. A combination of APDC coprecipitation and determination by an absolute thin layer Energy dispersive X-ray fluorescence spectrometry method was used. The influence of various analytical parameters such as element concentration, oxidation states and pH on the recoveries of Se (IV) was examined. The presence of organic matter and bicarbonate anions, typical components in Cuban groundwater samples, was also tested. Negligible matrix effects were observed. At pH 4 a 100% recovery was found for Se (IV). The coprecipitation recovery of the oxidized selenium species (Se (VI)) was null for the selected concentration range (5–100 μg L⁻¹). When the Se (VI) was reduced by heating the solution with 4 mol L⁻¹ HCl, quantitative recovery was also obtained. The determination of total selenium was conducted by the application of the oxidation–reduction process and the analytical procedure for Se (IV). Se (VI) content was calculated as the difference between total selenium and Se (IV). The detection limit was 0.13 μg L⁻¹. The relative standard deviation was lower than 3.5% for 5 μg L⁻¹ of Se (IV). The trueness of the method was verified by using standardized hydride generation-atomic absorption spectrometry technique. The results obtained using the EDXRF technique were in good agreement with the ones determined by HG-AAS. The proposed method was applied to the determination of Se (IV) in surface water and groundwater samples.     

Development of a highly robust solid phase microextraction fiber based on crosslinked methyl methacrylate–polyhedral oligomeric silsesquioxane hybrid polymeric coating

A novel solid-phase microextraction (SPME) fiber was prepared by polymerization of an organic–inorganic hybrid polymeric coating on an anodized and derived Ti wire, and applied for the analysis of polycyclic aromatic hydrocarbons from environmental samples followed by high performance liquid chromatography (HPLC) analysis. A polyhedral oligomeric silsesquioxane (POSS) reagent containing methacryl substituent groups was used as an organic–inorganic hybrid cross-linker, and copolymerized with methyl methacrylate (MMA) to fabricate the hybrid coating via thermally initiated free radical polymerization in a glass capillary mold. The prepared fiber can be easily withdrawn from the glass capillary mold by controlling the polymerization conditions, especially polymerization solvent. A homogeneous and porous coating with thickness of about 100 μm was achieved using ethanol as polymerization solvent at the mass ratio of MMA to POSS as 1:0.5. High chemical and mechanical stability, as well as excellent durability for more than 100 times extractions with almost undiminished extraction efficiency were achieved due to the chemical immobilization and crosslinked hybrid coating. The proposed fiber showed much better extraction performance than the 100 μm commercial polydimethylsiloxane fiber for extracting PAHs from aqueous sample. The developed SPME-HPLC method for the determination of PAHs using the MMA–POSS hybrid coating achieved good linearity with good correlation coefficients (R = 0.991–0.999) and low detection limits in the range of 0.006 to 0.05 ng mL⁻¹ (S/N = 3). The proposed fiber was successfully applied to the extraction of PAHs from environmental water samples with recoveries of 82–104% for river water, 83–103% for pool water, and 79–98% for wastewater, respectively.     

Conformationally blocked quinoxaline cavitand as solid-phase microextraction coating for the selective detection of BTEX in air

A tetraquinoxaline cavitand functionalized with methylenoxy bridges at the upper rim is proposed as selective solid-phase microextraction (SPME) coating for the determination of BTEX at trace levels in air. The SPME fibers were characterized in terms of film thickness, morphology, thermal stability and extraction capabilities. An average coating thickness of 35 (±4) μm, a thermal stability up to 350 °C and a good fiber-to-fiber and batch-to-batch repeatability with RSD lower than 15% were obtained. Excellent enrichment factors ranging from 360–700 × 10³ were obtained for the investigated compounds. Finally, method validation proved the capabilities of the developed coating for the selective sampling of BTEX, achieving LOD values in the 0.4–1.2 ng m⁻³ range.     

On-fibre solid-phase microextraction coupled to conventional liquid chromatography versus in-tube solid-phase microextraction coupled to capillary liquid chromatography for the screening analysis of triazines in water samples

This paper compares the advantages and disadvantages of two different configurations for the extraction of triazines from water samples: (1) on-fibre solid-phase microextraction (SPME) coupled to conventional liquid chromatography (LC); and (2) in-tube SPME coupled to capillary LC. In-tube SPME has been effected either with a packed column or with an open capillary column. A critical evaluation of the main parameters affecting the performance of each method has been carried out in order to select the most suitable approach according to the requirements of the analysis. In the on-fibre SPME configuration the fibre coating was polydimethylsiloxane (PDMS)-divinylbenzene (DVB). The limits of detection (LODs) obtained with this approach under the optimized extraction and desorption conditions were between 25 and 125 microg/L. The in-tube SPME approach with a C18 packed column (35 mm x 0.5 mm I.D., 5 microm particle size) connected to a switching micro-valve provided the best sensitivity; under such configuration the LODs were between 0.025 and 0.5 microg/L. The in-tube SPME approach with an open capillary column coated with PDMS (30 cm x 0.25 mm I.D., 0.25 microm of thickness coating) connected to the injection valve provided LODs between 0.1 and 0.5 microg/L. In all configurations UV detection at 230 nm was used. Atrazine, simazine, propazine, ametryn, prometryn and terbutryn were selected as model compounds.     

Miniaturized solid-phase extraction as a sample preparation technique for the determination of phthalates in water

Miniaturized solid-phase extraction (SPE) has been developed and successfully employed for the determination of organic species in water samples by liquid chromatography (LC). The method is based on the concept of a microscale extraction technique using a fused-silica capillary column for gas chromatography (GC), so-called in-tube solid-phase microextraction (SPME). The extraction conditions, such as the extraction time and flow-rate for the extraction and desorption process, were investigated as well as the effect of the internal structure of the extraction capillary on the efficiency. By inserting a stainless steel wire into the extraction capillary to reduce the internal volume of the capillary with the same surface area of the coating, an improved extraction and pre-concentration effects were obtained. Further pre-concentration was accomplished by the extraction device with a novel fiber-in-tube configuration. The direct coupling of the extraction method with a LC system has made it possible to determine low levels of phthalates in water samples without high consumption of organic solvents. The system developed must have potential applications for the analysis of environmental and biological samples in aqueous sample matrices.     

Preconcentration and separation of inorganic selenium on Dowex 1X8 prior to hydride generation-atomic absorption spectrometry

Exchange reactions between inorganic selenium species and chloride were studied on Dowex 1X8. The concentration exchange constants were determined with the batch technique at room temperature and used to predict the chromatographic enrichment and separation of tetra- and hexavalent selenium. A procedure for the determination of total selenium after digestion with permanganate and anion exchange preconcentration was also developed. The enrichment techniques were applied to the determination of Se(IV) and total dissolved selenium in drinking water and fresh water using flow injection hydride generation-atomic absorption spectrometry (HG-AAS). Results agreed with those obtained in a HG-AAS system where selenium was preconcentrated as hydrogen selenide in a trap at liquid nitrogen temperature.     

Determination of fluoroquinolones in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

We developed a sensitive and useful method for the determination of five fluoroquinolones (FQs), enoxacin, ofloxacin, ciprofloxacin, norfloxacin, and lomefloxacin in environmental waters, using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS). These compounds were analysed within 7 min by high-performance liquid chromatography (HPLC) using a CAPCELL PAK C8 column and aqueous ammonium formate (pH 3.0, 5 mM)/acetonitrile (85/15, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the positive ion mode were optimized for MS/MS detection. In order to optimize the extraction of FQs, several in-tube SPME parameters were examined. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample at a flow-rate of 150 μL/min, using a Carboxen 1010 PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve (r ≥ 0.997) was obtained in the concentration range from 0.1 to 10 ng/mL for all compounds examined. The limits of detection (S/N = 3) of the five FQs ranged from 7 to 29 pg/mL. The in-tube SPME method showed 60-94-fold higher sensitivity than the direct injection method (5 μL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface waters and wastewaters were collected from the area around Asahi River, and ofloxacin was detected in wastewater samples of a sewage treatment plant and other two hospitals at 17.5-186.2 pg/mL. The recoveries of FQs spiked into river water were above 81% for a 0.1 or 0.2 ng/mL spiking concentration, and the relative standard deviations were below 1.9-8.6%.     

In-tube solid-phase microextraction-capillary liquid chromatography as a solution for the screening analysis of organophosphorus pesticides in untreated environmental water samples

This paper describes a method for the selective screening of organophosphorus pesticides in water. In-tube solid-phase microextraction (SPME) in an open capillary column coupled to capillary liquid chromatography (LC) with UV detection has been used to effect preconcentration, separation and detection of the analytes in the same assembly. For in-tube SPME two capillary columns of the same length and different internal diameters and coating thicknesses have been tested and compared, a 30 cm x 0.25 mm I.D., 0.25 micro m thickness coating column, and a 30 cm x 0.1 mm I.D., 0.1 micro m of coating thickness column. In both columns the coating was 95% dimethylpolysiloxane (PDMS)-5% diphenylpolysiloxane. The proposed methodology provided limits of detections (LODs) for the tested organophosphorus pesticides in the 0.1-10 micro g/L range, whereas the direct injection of the samples onto the capillary LC system provided LODs in the 50-1000 micro g/L range. The sensitivity of the proposed in-tube SPME-capillary LC method is adequate to monitorize the analyte levels in drinking water. Several triazines, polycyclic aromatic hydrocarbons (PAHs), nonylphenol, organochloride pesticides or polybrominated diphenyl ethers (PBDEs) have been evaluated as possible interferents. The reliability of the described method is demonstrated by analysing different real water samples.     

Automated analysis of lidocaine and its metabolite in plasma by in-tube solid-phase microextraction coupled with LC-UV for pharmacokinetic study

A sensitive, selective, and reproducible in-tube solid-phase microextraction and liquid chromatographic (in-tube SPME/LC-UV) method for determination of lidocaine and its metabolite monoethylglycinexylidide (MEGX) in human plasma has been developed, validated, and further applied to pharmacokinetic study in pregnant women with gestational diabetes mellitus (GDM) subjected to epidural anesthesia. Important factors in the optimization of in-tube SPME performance are discussed, including the draw/eject sample volume, draw/eject cycle number, draw/eject flow rate, sample pH, and influence of plasma proteins. The limits of quantification of the in-tube SPME/LC method were 50 ng/mL for both metabolite and lidocaine. The interday and intraday precision had coefficients of variation lower than 8%, and accuracy ranged from 95 to 117%. The response of the in-tube SPME/LC method for analytes was linear over a dynamic range from 50 to 5000 ng/mL, with correlation coefficients higher than 0.9976. The developed in-tube SPME/LC method was successfully used to analyze lidocaine and its metabolite in plasma samples from pregnant women with GDM subjected to epidural anesthesia for pharmacokinetic study.     

Halloysite nanotubes-titanium dioxide as a solid-phase microextraction coating combined with negative corona discharge-ion mobility spectrometry for the determination of parathion

Halloysite nanotubes-titanium dioxide (HNTs-TiO₂) as a biocompatible environmentally friendly solid-phase microextraction (SPME) fiber coating was prepared. HNTs-TiO₂ was chemically coated on the surface of a fused-silica fiber using a sol–gel process. Parathion as an organophosphorus pesticide was selected as a model compound to investigate the extraction efficiency of the fiber. The extracted analyte was detected by negative corona discharge-ion mobility spectrometer (NCD-IMS). The effective parameters on the extraction efficiency, such as salt effect, extraction temperature and extraction time were investigated and optimized. The extraction efficiency of HNTs-TiO₂ fiber was compared with bare-silica (sol–gel based coating without HNTs-TiO₂), HNTs, carbon nanotubes and commercial SPME fibers (PA, PDMS, and PDMS–DVB). The HNTs-TiO₂ fiber showed highest extraction efficiency among the studied fibers. The intra- and inter-day relative standard deviations were found to be 4.3 and 6.3%, respectively. The limit of detection and limit of quantification values were 0.03 and 0.1 μg L⁻¹, respectively. The dynamic range of the method was in the range of 0.1–25 μg L⁻¹. The spiking recoveries were between 85 (±9) and 97 (±6). The SPME–HNTs-TiO₂ combined with NCD–IMS was successfully applied for the determination of parathion in apple, strawberry, celery and water samples.     

Preparation of C18 composite solid-phase microextraction fiber and its application to the determination of organochlorine pesticides in water samples

In this work, a C18 composite solid-phase microextraction (SPME) fiber was prepared with a new method and applied to the analysis of organochlorine pesticides (OCPs) in water sample. A stainless steel wire (o.d. 127 μm) was used as the substrate, and a mixture of the C18 particle (3.5 μm) and the 184 silicone was used as the coating material. During the process of fiber preparation, a section of capillary column was used to fix the mixture onto the stainless steel wire and to ensure the constant of coating thickness. The prepared fiber showed excellent thermal stability and solvent resistance. By coupling with gas chromatography–mass spectrometry (GC–MS), the fiber exhibited wide linearity (2–500 ng L⁻¹) and good sensitivity for the determination of six OCPs in water samples, the OCPs tested included hexachlorobezene, trans-chlordane, cis-chlordane, o,p-DDT, p,p-DDT and mirex. Not only the extraction performance of the newly prepared fiber was more than seven times higher than those of commercial fibers, the limits of detections (LODs) (0.059–0.151 ng L⁻¹) for OCPs achieved under optimized conditions were also lower than those of reported SPME methods. The fiber was successfully applied to the determination of OCPs in real water samples by using developed SPME–GC–MS method.     

Determination of stimulants in human urine and hair samples by polypyrrole coated capillary in-tube solid phase microextraction coupled with liquid chromatography-electrospray mass spectrometry

A simple and sensitive method for the determination of amphetamine, methamphetamine and their methylenedioxy derivatives in urine and hair samples was developed by coupling automated in-tube solid phase microextraction (SPME) to high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ES-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ES-MS detection were investigated. ES-MS detection conditions were studied by flow injection analysis (FIA) with direct liquid injection. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, including capillary stationary phases and sample pH. For the compounds studied, a custom-made polypyrrole (PPY) coated capillary showed superior extraction efficiency as compared to commercial capillaries. Therefore, the PPY coated capillary was selected for in-tube SPME in this study. The calibration curves of stimulants were linear in the range from 0.1 to 100 ng ml(-1) with detection limits (S/N=3) of 8-56 ng l(-1). This method was successfully applied to the analysis of the stimulants in spiked human urine and hair samples.     

In-sample derivatization-solid-phase microextraction of amphetamines and ecstasy related stimulants from water and urine

A solid-phase microextraction (SPME) method for the determination of five amphetamine type stimulants (ATSs) in water and urine samples is presented. Analytes were simultaneously derivatized with iso-butyl chloroformate (iBCF) in the aqueous sample while being extracted, improving in this way the extractability of ATSs and permitting their determination by gas chromatography–mass spectrometry (GC–MS). The SPME procedure was carefully optimized in order to achieve adequate limits of detection (LODs) for environmental concentrations. Hence, different operational parameters were considered: type of SPME coating, ionic strength, basic catalyzer and derivatizing agent amount, extraction time and temperature. The final SPME procedure consists into the extraction of 100 mL of sample containing 2 g of dipotassium monohydrogen phosphate trihydrate and 100 μL of iBCF (1:1 in acetonitrile), for 40 min at 60 °C with a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber. Under these conditions, LODs in wastewater ranged from 0.4 to 2 ng L⁻¹, relative recoveries in the 84–114% range and relative standard deviations (RSD) lower than 15% were obtained. The application of the method to wastewater and river water samples showed the ecstasy ATS, 3,4-methylenedioxymethamphetamine (MDMA), as the most frequently detected, followed by methamphetamine, in concentrations around 20 ng L⁻¹. Finally, the method was downscaled and also validated with urine samples, proving its good performance with this matrix too: RSD < 11%, recoveries in the 98–110% range and LODs lower than 0.1 μg L⁻¹.