Fiber-packed needle-type sample preparation device designed for gas chromatographic analysis

A miniaturized sample preparation technique that uses a fine-fiber-packed needle as the extraction medium is reviewed, especially in relation to its application to the analysis of volatile organic compounds by gas chromatography. When the needle was packed longitudinally with a bundle of fine filaments (12 μm o.d.) which were also surface-coated with polymeric materials, successful sample preconcentration was obtained. Improved sensitivity was also established by introducing simultaneous derivatization reactions into the extraction process in the fiber-packed needle. The storage performance of the needle clearly demonstrated the potential of the technique for typical on-site sampling during environmental analysis. In this short review, the fiber-packed extraction needle developed by the authors is summarized along with applications that use the fiber-packed needle as a miniaturized extraction device.     

Determination of Bisphenol A in Water Using a Packed Needle Extraction Device

A fiber-packed needle extraction device was used as a novel method for the extraction of bisphenol A from water samples. A bundle of filaments having a coating of polydimethylsiloxane was packed longitudinally into the needle. Good extraction efficiency was obtained even for an extraction time of 10 min, when the water sample was pumped through the needle with a syringe pump. The needle could be used repeatedly. The preparation procedure, included a derivatization process. Under optimum conditions, use of the fiber-packed needle showed a higher extraction efficiency than conventional sample preparation methods such as liquid–liquid extraction and solid-phase extraction.     

Simultaneous derivatization/preconcentration of volatile aldehydes with a miniaturized fiber-packed sample preparation device designed for gas chromatographic analysis

A novel in-needle sample preparation device has been developed for the determination of volatile aldehydes in gaseous samples. The needle device is designed for the gas chromatographic (GC) analysis of aldehydes and ketones commonly found in typical in-house environments. In order to prepare the extraction device, a bundle of polymer-coated filaments was longitudinally packed into a specially designed needle. Derivatization reactions were prompted by 2,4-dinitrophenylhydrazine (NDPH) included in the needle, and so the aldehydes and ketones were derivatized to the corresponding hydrazones and extracted with the extraction needle. A reproducible extraction needle preparation process was established, along with a repeatable derivatization/extraction process that ensures the successful determination of aldehydes. The storage performance of the extraction needle was also evaluated at room temperature for three days. The results demonstrate the successful application of the fiber-packed extraction device to the preparation of a gaseous sample of aldehydes, and the future possibility of applying the extraction device to the analysis of in-house environments.     

A simplified hollow-fibre supported liquid membrane extraction method for quantification of 2-amino-1-methyl-6-phenylimidazo[4,5-<Emphasis Type="BoldItalic">b</Emphasis>]pyridine (PhIP) in urine and plasma samples

A simple and easy-to-use extraction procedure has been optimised, validated, and applied for extraction of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in urine and spiked plasma samples. PhIP is a carcinogenic and mutagenic heterocyclic aromatic amine that is formed during cooking of meat and fish. The novelty of the extraction procedure lies in using a short piece of narrow capillary-like microporous hollow-fibre (HF) membrane as extraction device. The HF membrane was filled with a few microlitres of acidic solution and the membrane pores were impregnated with an organic extraction solvent. Therefore, the technique was called hollow-fibre supported liquid membrane (HF-SLM) extraction. The HF extraction device was then supported by a syringe needle and directly immersed in urine (1.4 mL) or plasma (0.3 mL) previously made alkaline by adding 0.5 mol L⁻¹ NaOH solution to give a final volume of 1.6 mL. The operation of the HF-SLM extraction at the optimal conditions resulted in a PhIP extraction efficiency of 74% from both spiked urine and plasma, corresponding to enrichment factors of 126 and 27, respectively. For 90 min extraction time, limits of detection and quantification were, respectively, 8 and 25 pg mL⁻¹ for urine and 6 and 11 pg mL⁻¹ for plasma. Within-day repeatability (n = 6) and between-day reproducibility (n = 3) were, respectively, 5% and 13% for urine and 6% and 7% for plasma. Analysis of urine samples collected for 12 h after a volunteer had eaten 250 g well-done chicken showed the PhIP concentration was 124 ± 21 pg mL⁻¹, calculated assuming an extraction efficiency of 74%.     

Preparation and application of a coated‐fiber needle extraction device

In this study, a needle‐trap device with fibers coated with a molecularly imprinted polymer was developed for separation. A number of heat‐resistant Zylon filaments were longitudinally packed into a glass capillary, followed by coating with a molecularly imprinted polymer. Then, the molecularly imprinted polymer coating was copolymerized and anchored onto the surface of the fibers. The bundle of synthetic fibers coated with the molecularly imprinted polymer was packed into a 21G stainless‐steel needle and served as an extraction medium. The coated‐fiber needle extraction device was used to extract volatile organic compounds from paints and gasoline effectively. Subsequently, the extracted volatile organic compounds were analyzed by gas chromatography. Calibration curves of gaseous benzene, toluene, ethylbenzene, and o‐xylene in the concentration range of 1–250 μg/L were obtained to evaluate the method, acceptable linearity was attended with correlation coefficients above 0.998. The limit of detection of benzene, toluene, ethylbenzene, and o‐xylene was 11–20 ng/L using the coated‐fiber needle‐trap device. The relative standard deviation of needle‐to‐needle repeatability was less than 8% with an extraction time of 20 min. The loss rates after storage for 3 and 7 days at room temperature were less than 30%.     

Novel sample preparation technique with needle-type micro-extraction device for volatile organic compounds in indoor air samples

A novel needle-type sample preparation device was developed for the effective preconcentration of volatile organic compounds (VOCs) in indoor air before gas chromatography–mass spectrometry (GC–MS) analysis. To develop a device for extracting a wide range of VOCs typically found in indoor air, several types of particulate sorbents were tested as the extraction medium in the needle-type extraction device. To determine the content of these VOCs, air samples were collected for 30 min with the packed sorbent(s) in the extraction needle, and the extracted VOCs were thermally desorbed in a GC injection port by the direct insertion of the needle. A double-bed sorbent consisting of a needle packed with divinylbenzene and activated carbon particles exhibited excellent extraction and desorption performance and adequate extraction capacity for all the investigated VOCs. The results also clearly demonstrated that the proposed sample preparation method is a more rapid, simpler extraction/desorption technique than traditional sample preparation methods.     

Selective Solid-Phase Extraction of Trace Copper Ions in Aqueous Solution with a Cu(II)-Imprinted Interpenetrating Polymer Network Gel Prepared by Ionic Imprinted Polymer (IIP) Technique

An Cu(II)-imprinted interpenetrating polymer network (IPN) gel of epoxy-diethylenetriamine and methacrylic acid-acrylamide-N,N′-methylene-bis-(acrylamide) was synthesized by the ionic imprint polymer (IIP) technique. The first polymer network is formed by epoxy gelation with diethylenetriamine. The other is formed by copper methacrylate co- polymerization with acrylamide and cross-linker N,N′-methylene-bis-(acrylamide). The adsorption–desorption characteristics of the IPN gel as a highly selective solid-phase extraction (SPE) and preconcentration adsorbent for Cu²⁺ from aqueous solution were investigated. The experimental results show that trace Cu²⁺ ions can be quantitatively enriched at pH 5 with recovery >95%. The maximum static adsorption capacity of the ion-imprinted functionalized gel adsorbent was 76 mg g⁻¹. Comparing with non-imprinted IPN gel, the imprinted IPN gel has higher adsorption capacity and selectivity for Cu²⁺ by the static adsorption–desorption experiment. Simultaneously, the times of adsorption equilibration and complete desorption were remarkably short. The precision (RSD) for 11 replicate adsorbent extractions of 20 ng mL⁻¹ Cu²⁺ was 3.4%. The established procedure was applied to two real water samples with satisfactory results. The prepared ion-imprinted IPN gel adsorbent was shown to be promising for solid-phase extraction coupled with atomic absorption spectrometry (AAS) for the determination of trace copper in real samples. In addition, the coordination interaction of Cu²⁺ and functional groups of the IPN gel adsorbent was primarily discussed by FT-IR spectra.     

Trace analysis of antidepressants in environmental waters by molecularly imprinted polymer-based solid-phase extraction followed by ultra-performance liquid chromatography coupled to triple quadrupole mass spectrometry

This paper presents the development, optimization, and validation of an innovative method to analyze trace concentrations of seven selected psychoactive pharmaceuticals in environmental waters. Hereby, the solid-phase extraction (SPE) potential of molecularly imprinted polymers (MIPs) in terms of extraction recovery, breakthrough, precision, and selectivity is studied for the first time. Instrumental analysis by ultra-performance liquid chromatography coupled to triple quadrupole mass spectrometry allowed a rapid (run time = 7.5 min) and sensitive (instrumental detection limit ≤7 pg injected) quantification of the target analytes. A systematic optimization study revealed that, among the seven compounds of interest, mainly the selective serotonin reuptake inhibitors paroxetine, fluoxetine, and citalopram are selectively retained on the MIPs. Experiments performed in spiked river water, sewage treatment plant (STP) effluent and influent showed for these compounds extraction recoveries higher than 70%, breakthrough volumes up to 200 mL, method detection limits (MDL) as low as 0.5 ng/L, and good precision (exemplified by relative standard deviations better than 15%, n ≥ 3). Compared to the widely used hydrophilic–lipophilic balanced (HLB) polymers, the newly developed MIPs indicated to be more resistant toward matrix effects induced ion signal suppression particularly when dealing with relative dirty samples like STP influents. As a result of the better selectivity, the MDL obtained with the MIP-based SPE method was up to a factor of 7 lower compared to those obtained with a recently reported multi-residue HLB method. However, optimizing a HLB method in terms of selectivity, e.g., by introducing a stronger washing protocol, can significantly reduce its MDL up to values approximating those obtained with MIPs.     

Determination of volatile organic hydrocarbons in water samples by solid-phase dynamic extraction

In the present study a headspace solid-phase dynamic extraction method coupled to gas chromatography–mass spectrometry (HS-SPDE-GC/MS) for the trace determination of volatile halogenated hydrocarbons and benzene from groundwater samples was developed and evaluated. As target compounds, benzene as well as 11 chlorinated and brominated hydrocarbons (vinyl chloride, dichloromethane, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, carbon tetrachloride, chloroform, trichloroethylene, tetrachloroethylene, bromoform) of environmental and toxicological concern were included in this study. The analytes were extracted using a SPDE needle device, coated with a poly(dimethylsiloxane) with 10% embedded activated carbon phase (50-μm film thickness and 56-mm film length) and were analyzed by GC/MS in full-scan mode. Parameters that affect the extraction yield such as extraction and desorption temperature, salting-out, extraction and desorption flow rate, extraction volume and desorption volume, the number of extraction cycles, and the pre-desorption time have been evaluated and optimized. The linearity of the HS-SPDE-GC/MS method was established over several orders of magnitude. Method detection limits (MDLs) for the compounds investigated ranged between 12 ng/L for cis-dichloroethylene and trans-dichloroethylene and 870 ng/L for vinyl chloride. The method was thoroughly validated, and the precision at two concentration levels (0.1 mg/L and a concentration 5 times above the MDL) was between 3.1 and 16% for the analytes investigated. SPDE provides high sensitivity, short sample preparation and extraction times and a high sample throughput because of full automation. Finally, the applicability to real environmental samples is shown exemplarily for various groundwater samples from a former waste-oil recycling facility. Groundwater from the site showed a complex contamination with chlorinated volatile organic compounds and aromatic hydrocarbons. Figure SPDE Principle     

Rapid determination of ethylene oxide with fiber-packed sample preparation needle

Fiber-packed sample preparation device was applied to the simultaneous derivatization/preconcentration of ethylene oxide (EO) in air samples. The polymer-coated filaments were packed longitudinally into the needle, and hydrogen bromide (HBr) was loaded onto the filaments in the preconditioning process. Simultaneous derivatization with HBr in the needle was made during the sampling process of the gaseous EO, and the corresponding derivatized analyte, 2-bromoethanol, was desorbed by passing a small amount of methanol through the extraction needle in the heated gas chromatograph (GC) injector. The basic extraction/desorption parameters for EO have been evaluated. The limit of detection (LOD), limit of quantification (LOQ) and the relative standard deviation (RSD) of run-to-run repeatability were 1.8 ng/L, 5.4 ng/L and less than 4%, respectively, with an extraction time of about 10 min. Satisfactory storage performance for three days at room temperature was also confirmed.     

Needle‐trap device for the sampling and determination of chlorinated volatile compounds

A needle‐trap device, with immobilized sorbent inside the syringe, coupled with GC–MS was applied for air sampling and determination of chlorinated volatile organic compounds such as dichloromethane, trichloromethane, and tetrachloromethane. The application of a needle trap packed with combination of three sorbents including Tenax TA, Carbopack X, and Carboxen 1000 resulted in detection limits of few pg for chlorinated volatile compounds and recoveries of 99.2–102.8%. The extraction and desorption parameters were optimized within the study. As a result, the precision determined as RSD was equal to 5.05 and 3.03 and 6.52% for dichloromethane, trichloromethane, and tetrachloromethane, respectively. The storage time for chlorinated compounds up to 48 h and reusability of the needle‐trap device were verified. The obtained results have proved the ability of needle traps to compete with other solventless sampling and sample preparation extraction techniques.     

A liquid–liquid extraction technique for phthalate esters with water-soluble organic solvents by adding inorganic salts

In the presence of inorganic salts, the mixture solution of some water-soluble organic solvents and water can form two clearly separated phases. One is the organic solvent rich phase, the other is the water rich phase. In the phase separation process, hydrophobic solutes dissolved in the mixture solution such as phthalate esters can be extracted into the organic solvent rich phase quantitatively. Based on this phase separation phenomenon, a liquid–liquid extraction technique of phthalate esters using water-soluble organic solvents as organic phases was developed. Several important parameters affecting the extraction efficiency including the kind and the amount of water-soluble organic solvents, the kind and the amount of inorganic salts and the pH of the sample solutions were carefully studied. This new extraction technique has been applied to the HPLC analysis for water lixivium of plastic wrapping film. Under the optimized conditions, detection limits of 1.5, 2.3, 1.0, 2.6, 1.3 and 3.0 ng mL⁻¹ were obtained for diethylphthalate, di-n-propylphthalate, di-iso-butylphthalate, dicyclohexylphthalate, di-n-octylphthalate and di-n-nonylphthalate ester respectively. The strongpoints of this new liquid–liquid extraction technique are the easy phase separation, rapid partition equilibrium, less toxicity and very good compatibility with subsequent HPLC determinations.     

Speciation analysis of chromium in natural water samples by electrothermal atomic absorbance spectrometry after separation/preconcentration with nanometer-sized zirconium oxide immobilized on silica gel

Silica gel was prepared by the sol–gel method, modified with nanometer-sized zirconium oxide, and this material was characterized by X-ray diffraction. A micro-column packed with silica gel modified with nanometer zirconium oxide as sorbent has been developed for the quantitative separation and preconcentration of trace amounts of chromium(III) prior to their determination by electrothermal atomic absorption spectrometry. Total chromium was determined after the reduction of chromium(VI) to chromium(III) by 10% (m/v) of aqueous ascorbic acid as reducing reagent. The adsorption capacity for chromium(III) was found to be 2.36 mg g⁻¹. The detection limit for chromium(III) was 15 ng L⁻¹ with an enrichment factor of 100. The relative standard deviation was 3.2% (n = 7, c = 2.0 ng mL⁻¹).     

Comparison of Needle Concentrator with SPME for GC Determination of Benzene, Toluene, Ethylbenzene, and Xylenes in Aqueous Samples

A method of solventless extraction of volatile organic compounds from aqueous samples has been developed and validated. A new arrangement in which the internal volume of a needle capillary adsorption trap is completely filled with Porapak Q, as adsorbent material, and wet alumina, as a source of desorptive water vapor flow, is presented. The device has been used for head-space sampling of benzene, toluene, ethylbenzene, and xylenes (BTEX) from water samples and compared with solid-phase microextraction. Under the same sampling conditions the analytical characteristics of the device for the BTEX compounds are better than those of solid-phase microextraction. Limits of detection and quantification are below 0.5 μ g L⁻¹.     

Water-compatible molecularly imprinted polymer for the selective recognition of fluoroquinolone antibiotics in biological samples

A novel water-compatible molecularly imprinted polymer (MIP), prepared with enrofloxacin (ENR) as the template, has been optimised for the selective extraction of fluoroquinolone antibiotics in aqueous media. The results of a morphological characterisation and selectivity tests of the polymer material for ENR and related derivatives are reported. High affinity for the piperazine-based fluoroquinolones marbofloxacin, ciprofloxacin, norfloxacin and ofloxacin was observed, whereas no retention was found for nonrelated antibiotics. Various parameters affecting the extraction efficiency of the polymer have been optimised to achieve selective extraction of the antibiotics from real samples and to reduce nonspecific interactions. These findings resulted in a MISPE/HPLC-FLD method allowing direct extraction of the analytes from aqueous samples with a selective wash using just 50% (v/v) organic solvent. The method showed excellent recoveries and precision when buffered urine samples fortified at five concentration levels (25–250 ng mL⁻¹ each) of marbofloxacin, ciprofloxacin, norfloxacin, enrofloxacin and sarafloxacin were tested (53–88%, RSD 1–10%, n = 3). Moreover, the biological matrix of the aqueous samples did not influence the preconcentration efficiency of the fluoroquinolones on the MIP cartridges; no significant differences were observed between the recovery rates of the antibiotics in buffer and urine samples. The detection limits of the whole process range between 1.9 and 34 ng mL^–1 when 5-mL urine samples are processed. The developed method has been successfully applied to preconcentration of norfloxacin in urine samples of a medicated patient, demonstrating the ability of the novel MIP for selective extraction of fluoroquinolones in urine samples.     

Development of a new three-phase membrane-assisted liquid-phase microextraction method: determination of nitrite in tap water samples as model analytical application

A novel and simple device for membrane-assisted liquid-phase microextraction is used for the first time in a three-phase system. The device consists of a glass vial containing the aqueous acceptor phase, whose septum of its screw stopper has been replaced by a sized piece of polytetrafluoroethylene membrane impregnated with n-decane. The vial is assembled to a volumetric flask containing the aqueous donor phase, and the membrane comes in contact alternatively with both donor and acceptor aqueous phases by orbital agitation. The device has been tested for the determination of nitrite in tap water samples, which is extensively carried out in routine analysis, as model analytical application. Experimental variables, such as the organic solvent used to form the supported liquid membrane, the volumes of both donor and acceptor phases, the orbital agitation rate, and the extraction time were studied and optimized in terms of enrichment factor. Under the selected working conditions, the analytical figures of merit for nitrite determination were a linearity range up to 50 ng mL⁻¹, limits of detection and quantification of 0.15 and 0.50 ng mL⁻¹, respectively, and a good repeatability (RSD < 10%). The method has been applied to four tap water samples of different origins, and accurate and precise results were achieved. Besides, the very low volume of organic solvent used, its low cost and the no-risk of cross-contamination are significant operational advantages.     

Application of a novel nylon needle filter-based solid-phase extraction device to determination of 1-hydroxypyrene in urine

In this work, a simple and miniaturized solid-phase extraction device was constructed by connecting a commercial nylon needle filter to a syringe, which was applied for extracting 1-hydroxypyrene from a urine sample via hydrophobic and hydrogen bond interactions. The nylon membrane in the needle filter acted as the solid-phase extraction adsorbent, meanwhile, it filtered the particles in the urine sample. To obtain high extraction efficiency, key parameters influencing extraction recovery were investigated. The entire pretreatment process was accomplished within 5 min under the optimal conditions. By coupling high-performance liquid chromatography–ultraviolet, a rapid, low-cost, and convenient nylon needle filter-based method was established for the analysis of 1-hydroxypyrene in a complex urine matrix. Within the linearity range of 0.2–1000 μg/L, the method exhibited a satisfactory correlation coefficient (R = 0.9999). The limit of detection was 0.06 μg/L, and the recoveries from urine sample spiked with three concentrations (5, 20, and 100 μg/L) ranged from 105.8% to 113.1% with the relative standard deviations less than 6.7% (intra-day, n = 6) and 8.9% (inter-day, n = 4). Finally, the proposed method was successfully applied for detecting 1-hydroxypyrene in urine samples from college students, smokers, gas station workers, and chip factory workers. The detected concentration in actual urine samples ranged from 0.46 to 5.26 μg/L. Taken together, this simple and cost-effective nylon needle filter-based solid-phase extraction device showed an excellent application potential for pretreating hydrophobic analytes from aqueous samples.     

Electrospun composite of polypyrrole-polyamide as a micro-solid phase extraction sorbent

A micro-solid phase extraction technique was developed using a novel polypyrrole-polyamide nanofiber sheet, fabricated by electrospinning method. The applicability of the new nanofiber sheet was examined as an extracting medium to isolate malathion as a model pesticide from aqueous samples. Solvent desorption was subsequently performed in a microvial, and an aliquot of extractant was injected into gas chromatography–mass spectrometry. Various parameters affecting the electrospinning process including monomer concentration, polyamide content, applied voltage, and electrospinning time were examined. After fabricating the most suitable preparation conditions, influential parameters on the extraction and desorption processes were optimized. The developed method proved to be rather convenient and offers sufficient sensitivity and good reproducibility. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the method under optimized conditions were 50 and 100 ng L⁻¹, respectively. The relative standard deviation at concentration level of 1 ng mL⁻¹ was 2% (n = 3). The calibration curve of analyte showed linearity in the range of 0.1–1 ng mL⁻¹ (R ² = 0.9975). The developed method was successfully applied to tap and Zayanderood river water samples, while the relative recovery percentages of 98% and 96% were obtained, respectively. The whole procedure showed to be conveniently applicable and quite easy to be manipulated.     

Molecularly imprinted on-line solid-phase extraction combined with chemiluminescence for the determination of pazufloxacin mesilate

A novel molecularly imprinted polymer solid-phase extraction (MISPE) with flow-injection chemiluminescence (CL) was developed for the determination of pazufloxacin mesilate (PZFX). The molecularly imprinted polymer (MIP) was synthesized by using PZFX as the imprinting molecule. A glass tube packed the particles of the MIP was employed as MISPE micro-column, which was connected into the sampling loop of the eight-way injection valve for on-line selective preconcentration and extraction of PZFX. The eluent of acetonitrile:acetic acid (9:1, v:v) was used as carrier for eluting the adsorbed PZFX to react with the mixture of cerium(IV) and sodium sulfite in the flow cell to produce strong CL. The relative intensity of CL was linear to PZFX concentration in the range from 2.5 × 10⁻⁹ to 2.5 × 10⁻⁷ g mL⁻¹. The limit of detection was 7 × 10⁻¹⁰ g mL⁻¹ (3 σ) and the relative standard deviation for 5 × 10⁻⁸ g mL⁻¹of PZFX solution was 3.7% (n = 7). This method has been applied to the determination of PZFX in human urine.     

Selective determination of alkylmercury compounds in solid matrices after subcritical water extraction,followed by solid‐phase microextraction and GC–MS

A method for the extraction and determination of methylmercury (MeHg) in solid matrices is presented. Combining the advantages of two extraction techniques—subcritical water extraction (subWE) and solid‐phase microextraction (SPME)—selective separation of MeHg from soils is possible. The procedure is based on extraction with subcritical water without using organic solvents, followed by in situ aqueous‐phase derivatization with sodium tetraethylborate and headspace SPME with a silica fiber coated with poly(dimethylsiloxane). The optimization of the extraction parameters is described. The identification and quantification of the extracted alkylmercury compounds from spiked soil samples is performed by GC–MS after thermal desorption. Copyright © 2000 John Wiley & Sons, Ltd.