Search

An effective analytical method to quantify glyphosate (Gly), aminomethylphosphonic acid (AMPA) and glufosinate (Glu) in four kinds of Chinese herbs by derivatization was developed. The method was studied in four steps: extraction, purification, derivatization and enrichment. The extraction and purification steps were optimized. The sample was added with isotope-labeled internal standards and extracted with 30% acetonitrile. The MCX solid-phase extraction cartridge was chosen to reduce interferences and the purification solution was derivatized with 9-fluoromethoxycarbonyl chloride. 4 M HCl was selected as reaction terminator. The supernatant was enriched by salting-out using NaCl and analyzed by LC–MS/MS in heated positive electrospray ionization mode by multiple reactions monitoring. To verify the method methodically, matrix effect, linearity, limits of quantitation and detection, accuracy and precision all met SANTE/12682/2019 requirements. The modified method was applied to 152 batches of 4 different Chinese herbs. The overall detection rate of Gly was 79.61%, AMPA was 72.37% and Glu was 16.45%. [ABSTRACT FROM AUTHOR]

Veterinary antibiotics in agricultural soil are a growing concern, as they pose risks to soil quality and food safety. An analysis approach that covers a broad spectrum of target substances and has low detection limits is required for a comprehensive risk assessment. In this study, we developed a method for simultaneously analyzing 34 antibiotics (tetracyclines, sulfonamides, macrolides, and quinolones) in agricultural soil. The soil was extracted using an organic solution of acetonitrile and methanol (v:v, 1:1) with 0.2% formic acid followed by the addition of Na2EDTA-McIlvaine buffer. Dispersive and solid-phase extractions (SPE) were compared for cleanup. Ultra-performance liquid chromatography-tandem mass spectrometry with matrix-matched calibration was used for quantification. The results of this study showed that SPE was more appropriate for determining multi-class antibiotics. The SPE approach proved better recoveries (56–98%) than dispersive SPE (d-SPE) (28–121%). The matrix effects obtained by SPE (46–299%) were more reasonable than that by d-SPE (3–4036%). The method detection limits by SPE were in the range of 0.007–1.400 μg/kg with relative standard deviations < 18%. This optimized method was then applied to 55 agricultural soil samples. The total concentrations of veterinary antibiotics ranged from blow method detection limits to 1448 μg/kg. Tetracyclines were the dominant antibiotics, particularly in soil applied with swine manure. This method can be used to screen for and accurately determine the presence of veterinary antibiotics in soil, which will aid their risk assessment and regulation of these antibiotics in the agroecosystem. [ABSTRACT FROM AUTHOR]

Herein, we proposed a simple and efficient microwave-assisted preparation method for the fabrication of zirconium (IV) intercalated expanded graphite (Zr-EG). The synthetic approach could be completed in one step within 20 s, where KMnO4 was used as the oxidizing agent, H2SO4 and ZrOCl2 as the intercalating agents. The as-prepared Zr-EG exhibited thin multi-layered structure, plenty of small Zr-relevant particles and oxygenated groups in both layers and surface, which gave Zr-EG high absorption capability. Subsequently, the Zr-EG, as a new kind of solid-phase extraction absorbent, was applied to the separation, purification and enrichment of chlorpyrifos in honey samples, followed by high-performance liquid chromatography analysis. Under optimal extraction and analysis conditions, the detection limit was 100 ng g−1. The relative standard deviations ranged from 2.6 to 6.8%. At three spiked levels (1, 10, 100 μg g−1), the recoveries of chlorpyrifos were in the range of 86.1–92.2%. Comparison with other conventional solid-phase extraction adsorbents, modified EG showed rapid synthesis, layered modification flexibility, stable structure, large adsorption capacity and good selectivity, demonstrating great potential in pollutants separation and detection. [ABSTRACT FROM AUTHOR]

Estradiol valerate (EST) and Norethisterone acetate (NOR) are co-formulated as a hormone replacement therapy. Naturally occurring steroidal hormones like estradiol, estrone and estriol are also considered as impurities in drug substance. Chromatographic separation of these five steroidal hormones was developed by HPLC and TLC. Reversed-phase chromatography was applied using either acetonitrile–methanol containing 0.05% β-cyclodextrin as a mobile phase for HPLC with gradient elution and chloroform–propanol–formic acid (5:3:2, by volume) as a developing system in TLC. The methods have been applied for determination of EST and NOR in presence of other natural congeners in biological samples as well as in drug products as official impurities. Solid-phase extraction was applied for saliva sample cleaning using testosterone as internal standard whereas ampoules and tablets formulations were used in pharmaceutical applications. The methods have been validated for bioanalytical and pharmaceutical analysis following the respective FDA and ICH guidelines. The obtained results were statistically compared with the official methods for both drugs. [ABSTRACT FROM AUTHOR]

In this study, the influence of the different mobile phase compositions on the sensitivity and chromatographic performance of prohibited small peptides (< 2 kDa), their metabolites, and non-peptide substances (anamorelin, ibutamoren) were demonstrated using LC–electrospray ionization coupled with triple quadrupole tandem mass spectrometry (LC–ESI–MS/MS). In the mobile phase, widely used mobile phase additives, ammonium formate (AF), formic acid (FA), and dimethylsulfoxide (DMSO) were employed with different organic phase modifiers such as acetonitrile (ACN) and methanol (MeOH). To evaluate the limit of detection (LOD) and matrix effect of analytes, urine samples were prepared by solid-phase extraction (SPE), and then, their analysis was performed by LC–ESI–MS/MS. LOD values of analytes were found to be between 0.05–2 ng mL−1 except for ibutamoren, anamorelin, and leuprolide (5–9), which had LOD values of lower than 0.05 ng mL−1. The best results related to sensitivity and chromatographic performance for the analysis of the analytes were achieved using ACN-based mobile phase containing 0.1% FA, which led to less ion suppression for most analytes compared to other employed mobile phase compositions. The proposed method to use for confirmation analysis of analytes was validated with respect to selectivity, carryover, precision, the limit of identification (LOI), recovery, matrix effect, and robustness. The applicability of the method in real urine samples was demonstrated by analyzing two different excretion urine samples containing leuprolide and triptorelin. [ABSTRACT FROM AUTHOR]

An analytical method based on solid-phase extraction–hydrophilic interaction chromatography–tandem mass spectrometry (SPE–HILIC–MS/MS) has been developed to quantify moniliformin in vegetable oil. The sample was extracted by methanol and purified by an Oasis MAX solid-phase extraction column. Following purification, it was separated by a Waters HILIC hydrophilic interaction column. Acetonitrile and 0.5 mM ammonium acetate solution were used as a mobile phase for gradient elution. An electrospray-negative ion multiple-reaction monitoring mode was used to quantify moniliformin by external standard method. In the mass concentration range of 0.1–10 μg/L, the correlation coefficient of moniliformin was 0.9997. The detection limit of this method was 0.03 μg/L, and the limit of quantification was 0.1 μg/L. When the three levels of 1.0, 2.0 and 5.0 μg/kg moniliformin were added, the recovery was 84.6%–98.2% with a relative standard deviation of 1.3%–5.1%. The results indicated that this method is simple, fast, sensitive, reproducible, and can be used to determine moniliformin in vegetable oil. [ABSTRACT FROM AUTHOR]

An ion chromatography (IC) method coupled with solid-phase extraction was established for the simultaneous determination of trace organic acids and inorganic anions in sodium carboxymethyl cellulose (CMC). To prevent CMC from contaminating analytical column, a self-packed solid-phase extraction column packed with quaternized adsorbents was applied in sample pretreatment. An IonPac, AS11-HC column was used as the analytical column for separation of glycolate, chloroacetate, chloride, and sulfate with gradient elution of potassium hydroxide at a flow rate of 1.0 mL min−1. Under the optimized chromatographic conditions, the linearity of the method was satisfactory over a concentration range of 0.5–150.0 mg L−1 with correlation coefficients of 0.9992–0.9999, and the limits of detection varied from 0.05 to 0.1 mg L−1, based on the signal-to-noise ratio of 3. The proposed method was successfully applied to the analysis of organic acids and inorganic anions in CMC samples. The recoveries ranged from 86.7 to 109.0% with the relative standard deviations (RSDs) over the range of 0.32–3.61%. The method offers a reliable application for the analysis of trace organic acids and inorganic anions in complex anionic cellulose. [ABSTRACT FROM AUTHOR]

Rotenone, a naturally occurring isoflavone compound, is applied to water as a piscicide to manage undesired fish populations in lakes, ponds, rivers and in aquaculture. A rapid and sensitive method based on solid-phase extraction (SPE) combined with large-volume sample stacking with polarity switching (LVSS) and micellar electrokinetic chromatography (MEKC) has been developed for the identification and quantification of rotenone in lake water. Several experimental parameters for MEKC, LVSS and SPE were investigated to achieve the optimum conditions necessary for the analysis. The optimized conditions which included a background electrolyte containing 20 mM sodium borate and 25 mM sodium dodecyl sulfate (SDS) at pH 10 were used to successfully detect rotenone within 17 min. Using a combined SPE and LVSS approach, the rotenone signal was enhanced by 1000-fold compared with a normal capillary electrophoresis analysis, and limits of detection and quantification obtained were 3 and 10 μg L−1, respectively. The calibration curve was linear for rotenone concentration over the range of 10–100 μg L−1 and the method was highly reproducible with the relative standard deviation of the peak areas and migration times for method intra-day repeatability (n = 6) found to be 5.4% and 0.6%, respectively. Quantitative recoveries ranging from 85 to 88% were obtained in the lake water matrices. The potential of the proposed method to be used for quantitative determination of rotenone at trace level concentrations in water samples was demonstrated by analyzing lake water samples including surface (1 m) and bottom (13 m), which makes it a suitable practical method for analyzing rotenone residues in water. [ABSTRACT FROM AUTHOR]

Eight molecularly imprinted polymers (MIPs) were synthesized for the determination of the antibacterial agent gemifloxacin mesylate (GFM). The polymers were prepared using GFM as a template, methacrylic acid (MAA) or 4-vinylpyridine (4-VP) as functional monomers, ethylene glycol dimethacrylate (EGDMA) as a cross linker, 2,2′-azobisisobutyronitrile (AIBN) as an initiator and a mixture of dimethylsulfoxide (DMSO)/acetonitrile (ACN) (1:1, v/v) as a porogen. The optimized polymer was utilized as a solid-phase extraction (SPE) sorbent material for GFM from different matrices. Different loading, washing and elution protocols were investigated. Quantitative analysis of the extracts was performed using a newly developed ultra-performance liquid chromatography–mass spectrometry (UPLC–MS/MS) method on an Acquity BEH C18 column (100 mm × 2.1 mm, particle size of 1.7 µm). The isocratic mobile phase was a mixture of methanol (MeOH)/water (H2O) with 0.1% formic acid (70:30, v/v), the flow rate was 0.3 mL min−1 and the column temperature was 40 °C. Lomefloxacin (LOM) was used as an internal standard. The developed method was validated based on the recommendations of the International Conference on Harmonization (ICH) and was found suitable for the extraction of GFM from a pharmaceutical drug preparation and spiked human urine samples. Recovery % values ranged from 90.24 to 112.8% with relative standard deviation (RSD) of less than 7%. [ABSTRACT FROM AUTHOR]

In this study, a rapid reversed-phase liquid chromatography method for the determination of azithromycin and its related substances was developed and validated on a novel polyfunctional silyl reagent [hexanhexamethyloctadecyltetrasiloxane (HMODTS–C18)] bonded core–shell RP C-18 column (100 × 4.6 mm, 2.6 µm) as per ICH guidelines. A binary gradient elution programme with a mixture of solvent A (phosphate buffer, pH 8.9) and solvent B (ACN: MeOH, 3:1) as mobile phase, at a flow rate of 1.5 mL min−1 and detection at 210 nm was finally optimized for the study. The validation results showed that the method to be specific, selective, highly sensible (0.004 mg mL−1), precise (% RSD ≤ 10), linear and accurate in a concentration range of 0.004–0.032 mg mL−1. Simple SPE method was performed for extraction and checked for repeatability. The result showed that the method is precise (%RSD < 2). The validated chromatographic method was applied to the solid-phase extracted samples of azithromycin and its four major related substances. Also, docking study was carried out using AutoDock Tools to find out the binding affinities, number of hydrogen bonds and residues involved in hydrogen bonds for azithromycin and its four major related impurities with the human plasma proteins. The results confirmed the applicability of the proposed method on the extracted human plasma samples. Finally, the study demonstrates that the impurities of azithromycin have strong binding affinities with the plasma proteins compared to that of azithromycin and half life of these impurities may be higher than azithromycin which can cause major health risk on repeated doses of azithromycin. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the more recent applications of solid-phase extraction (SPE, from January 2015 to September 2018, which have been recorded in Web of Science) in preparation of food and environmental samples. First, the history, milestones, principles, and features of different formats of SPE are discussed. In addition, miniaturization of SPE techniques and comparison of classical SPE and miniaturized SPE—called dispersive micro solid-phase extraction (D-μ-SPE)—are covered. Next, the published applications in extraction and separation of diverse organic and inorganic analytes from a variety of food and environmental samples are classified on the basis of their sorbents including layered double hydroxide, metal organic frameworks, carbon nanotube-based sorbents, graphene-based sorbents, β-cyclodextrin-based sorbents, dendrimer-based sorbents, molecular or ion recognition sorbents, and restricted access materials. Finally, the future trends in this area are discussed. [ABSTRACT FROM AUTHOR]

The effective extraction and detection of pollutants in the environment have been important issues in analytical science. Cellulosic materials, composed of both functionalized and composited components, have been recently identified as promising solid-phase extraction adsorbents for various applications. Due to their alluring properties such as renewability, biodegradability, biocompatibility, high strength and stiffness and easy modification, this unique class of materials exhibits excellent extraction and enrichment performance for numerous target analytes. Herein, we review recent significant advances in solid-phase extraction using cellulosic sorbents for organic and inorganic pollutants in environmental matrices. The development of new cellulose-based sorbents and related solid-phase extraction (SPE) patterns, including cartridge SPE (c-SPE), disk SPE, dispersive SPE, magnetic SPE, molecularly imprinted SPE, on-line SPE, SPE spectroscopy/spectrometry and thin film microextraction (TFME), were discussed in this review. [ABSTRACT FROM AUTHOR]

This work focuses on the extraction and determination of contaminants of environmental concern belonging to the classes of benzotriazoles and benzothiazoles from tap and raw river water samples. The sorbent, recently proposed by this research group, prepared by pyrolysis of humic acids (HAs) onto silica microparticles (HA-C@silica), was tested for fixed-bed SPE of benzotriazole and benzothiazole compounds by modulating its sorption affinity through the carbon loading. This was successfully increased from 10 to 20 wt% HAs and the obtained material, characterized by different techniques, provided quantitative adsorption at the sample native pH (7.5–8), for 50–250 mL samples spiked with each compound at the micrograms per litre levels. After extraction, the analytes were simultaneously desorbed by 4 mL methanol, even more reducible to small volume before HPLC–HESI-MS/MS analysis. Recovery was satisfactory for all compounds, ranging from 70 to 114%, with RSD values ≤ 16% (n = 3). The developed procedure allows quantitation of benzotriazoles at concentrations far below the environmental trigger limits. HA-C@silica turned out to be appealing in comparison with the commercial sorbents in terms of cost, recovery and pre-concentration for determination of such pollutants in actual surface waters. Good reproducibility was observed on independent HA-C@silica preparations. [ABSTRACT FROM AUTHOR]

Determination of parts per quadrillion (ppq) levels of various pollutants, contaminants, or background species in environmental samples is a challenging task for analytical chemistry. Among them, dioxins, perfluoroalkylated acids, organophosphorus and organochlorine pesticides, herbicides, and nitrosamines are found in the environment and consequently they must be determined at ppq levels. Analytical techniques alone are not able to reach these concentration levels, and they can be utilized only if sample enrichment is applied. This review is based on the literature reporting analytical methods based on solid-phase extraction or related techniques that are applied to determine ppq levels or have quantitation limits below the parts per trillion (ppt) range. Some other important aspects of the analytical process, such as calibration, precision, recovery, uncertainty, environmental matrix certified reference materials, or interlaboratory comparison, are discussed in the context of this analytical research. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are porous crystalline materials with large surface areas, uniform pore size, and tunable selectivity. In the last few years, the number of analytical applications of MOFs has been growing constantly. However, the direct use of as-synthesized MOFs in packed column format is rather limited for analytical separations because of the small size and non-spherical shape of MOF crystals. In this review, we outline and critically discuss the advantages and limitations of the different methods described to immobilize MOFs into functional supports for analytical separations, including beads, monoliths, and fibers. These methods are based on embedding MOF crystals into functional supports, in situ MOF growth, controlled layer-by-layer MOF growth, or the in situ conversion of immobilized MOF metal oxide precursors. Representative examples of immobilized MOFs for sample preparation and chromatographic separation are overviewed. We also overview recent progress on the use of MOFs as precursors to obtain other functional materials such as layered double hydroxides or porous carbons. [ABSTRACT FROM AUTHOR]

A method for the determination of catecholamine derivatives in human urine is proposed that includes the derivatization of target compounds on a solid-phase extraction cartridge and determination of the analytes by a UHPLC method with tandem mass-spectrometric detection. 9-Fluorenyl-methoxycarbonyl chloride was used as the derivatization agent. The limits of detection for the analytes were 2.5 ng mL−1 for 9-fluorenyl-methoxycarbonyl-adrenaline, 5 ng mL−1 for 9-fluorenyl-methoxycarbonyl-octopamine, and 25 ng mL−1 for 9-fluorenyl-methoxycarbonyl-dopamine. The proposed procedure was tested on real samples obtained from volunteers. [ABSTRACT FROM AUTHOR]

This work presents the synthesis of a polymeric mixed-mode solid-phase extraction (SPE) sorbent for clean-up and isolation of caffeine from black and green tea samples. The material was synthesized by a simple thermally initiated copolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate. Further functionalization was executed with histidine (HIS). Functional groups were investigated by attenuated total-reflection infrared spectroscopy. Furthermore, nitrogen sorption porosimetry was executed and revealed surface areas of 90 m2 g− 1. Adsorption capacities for caffeine were compared between functionalized and non-modified polymers and showed maximum capacities of 3.01 and 4.82 mg g− 1 polymer, respectively. Time adsorption profiles revealed an equilibrium adsorption after 15 min. The proposed polymer was used for SPE of black and green tea extracts and showed excellent clean-up efficiency for isolation of caffeine with recoveries ranging from 89 to 93%. When compared to commercially available Oasis HLB, the HIS-functionalized polymer demonstrated a distinctly better performance for clean-up. Finally, the proposed method was validated regarding international (ICH) guidelines and regulations. [ABSTRACT FROM AUTHOR]

Abstract: A rapid and effective solid-phase extraction high-performance liquid chromatography fluorescence detection (SPE-HPLC-FLD) method, using a novel porous aromatic framework (PAF-6) as solid-phase extraction sorbent, was established to enrich and determine bisphenol (BPA) in milk and its packing samples. Parameters influencing the extraction efficiency, such as volume of the sample solutions, pH of the sample, and the eluent volume, were examined. The limits of detection and quantitation were 0.1 and 0.33 ng mL−1, respectively. The recovery of the method was desirable at 81-91% and the relative standard deviation was less than 2.35%. Besides, the PAF-6-based cartridges exhibited superior reusability for milk sample analysis. In addition, theoretical computations were performed to further understand the molecular interaction mechanism between the PAF-6 and the BPA. The results showed that PAF-6 had an excellent adsorption capability for BPA based on hydrogen bonding and the inclusion interactions of host-guest. The proposed method is sensitive, simple, and cost-saving, and provides a detection platform for the monitoring of BPA residues in real milk samples.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: A quick and reproducible screening analytical method for the simultaneous determination of algal toxins, belonging to different chemical classes, was developed to provide a toxin profile in seawater, useful to assess potential risks to environment and human health. The target compounds were: gonyautoxin-1,4, gonyautoxin-2,3, decarbamoylgonyautoxin-2,3, N‐sulfocarbamoyl-gonyautoxin-1,2, neosaxitoxin, decarbamoyl-neosaxitoxin, saxitoxin, decarbamoyl-saxitoxin, domoic acid, 13-desmethyl spirolide C (SPX1), palytoxin and okadaic acid. Extraction and clean-up were carried out with a combination of Bond Elut LRC-C18 and Carbograph4 cartridges connected in series. Analyte separation was performed in gradient elution mode in 12 min with a Gemini C18 column. Compound detection was carried out in multiple reaction monitoring and in positive ionization mode for paralytic shellfish poisoning toxins, domoic acid, SPX1 and palytoxin, and in negative ionization mode for okadaic acid. The toxins were quantified with matrix-matched calibration curves constructed by spiked seawater samples (concentration levels 0.02–2 μg L−1 depending on the compound). The method was reproducible with intra-day and inter-day relative standard deviations ranging from 4 to 9% and from 8 to 16%, respectively. Good recoveries (84–105%) and good accuracy (2–20%) were obtained by spiking experiments. Limits of detection were calculated for each toxin and varied from 0.011 to 0.12 μg L−1 depending on the compound. The developed method was applied to cultured Ostreopsis cf. ovata samples. The proposed procedure may be considered a valuable alternative to existing methods for monitoring toxic microalgae, since it offers a rapid screening of target toxins, reduced organic solvent consumption, and handling of smaller sample volumes while providing good sensitivity and accuracy.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Development of efficient methods for isolation and separation of biologically active compounds remains an important challenge for researchers. Designing systems such as organomineral composite materials that allow extraction of a wide range of biologically active compounds, acting as broad-utility solid-phase extraction agents, remains an important and necessary task. Selective sorbents can be easily used for highly selective and reliable extraction of specific components present in complex matrices. Herein, state-of-the-art approaches for selective isolation, preconcentration, and separation of biologically active compounds from a range of matrices are discussed. Primary focus is given to novel extraction methods for some biologically active compounds including cyclic polyols, flavonoids, and oligosaccharides from plants. In addition, application of silica-, carbon-, and polymer-based solid-phase extraction adsorbents and membrane extraction for selective separation of these compounds is discussed. Potential separation process interactions are recommended; their understanding is of utmost importance for the creation of optimal conditions to extract biologically active compounds including those with estrogenic properties. [ABSTRACT FROM AUTHOR]

Graphene aerogel monolith was synthesized directly in the solid-phase extraction cartridge through template-free 'sol-cryo' method and used for the separation of pyrethroids insecticides from water samples, followed by gas chromatography-mass spectrometry analysis. Graphene sheets, the basic components of graphene aerogel, extracted the analytes from water samples through π-π stacking interaction and hydrophobic interaction. Then the targets were desorbed in ethyl acetate for subsequent analysis. Several parameters such as adsorption property, the type of the elution solvent and elution volume, the loading volume and its pH were investigated to achieve the best solid-phase extraction performance. Low limits of detection in the range of 0.83-9.31 ng L and acceptable precision (RSDs 3.8-11.7%) were achieved under the optimized conditions. The developed method was applied to extract pyrethroids from real water samples with satisfactory recoveries between 76.2 and 106.0%. The present work extends the application of graphene related materials in separation science. Graphical abstract: [ABSTRACT FROM AUTHOR]

Untreated rice husk (RH) was evaluated as solid-phase extraction (SPE) sorbent for Fluoroquinolone antibiotics (FQs). This natural material, made of cellulose, hemicellulose, lignin and silica, and containing various functional groups, i.e., carboxyl, hydroxyl, and amidogen residues, is a potential sorbent material for polar aromatics like FQs. First, the RH capability to adsorb FQ species from water was studied by batch sorption experiments in tap and river waters, and the experimental data, fitted by the Langmuir model, gave adsorption capacities up to 32 mg g. Then, RH was tested as column-packed sorbent for pre-concentration of tap and not tampered river waters spiked with six widely employed FQs, i.e., Ciprofloxacin, Danofloxacin, Enrofloxacin, Levofloxacin, Marbofloxacin, and Norfloxacin. The analytes were quantitatively adsorbed on the RH cartridge at the native pH, simultaneously eluted by NH-MeOH mixture, separated in an 8 min ultrahigh-performance liquid chromatography run and quantified/confirmed by electrospray ionization tandem mass spectrometric detection in single reaction monitoring mode. Recoveries in the range 71-120% were observed (RSD < 15%, n = 3) for 75-1000 ng L spikes. Method detection limits were in the range 25-33 ng L. The batch-to-batch reproducibility was assessed, and the analytical procedure was applied to the determination of FQs in actual environmental waters. [ABSTRACT FROM AUTHOR]

This study examined the matrix effect of a typical surfactant on the detection of pesticides in water using ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). When direct sample injection is employed, surfactants in water samples tend to adsorb onto the chromatographic column, weakening its analyte separation capability and consequently lowering signal detection intensities and raising detection limits. A new sample preparation approach of a tailored solid-phase extraction (SPE) is proposed based on the difference in adsorption affinities between surfactant and pesticide for silylated surfaces. Using sodium dodecyl sulfate (SDS) as a representative surfactant, four types of silylated silica particles with different surface hydrophobicity and functionality were examined for selectively adsorbing and removing SDS from water samples with pesticide analytes to eliminate the matrix effect of the surfactant on liquid chromatographic (LC) separation. It was found that the tailored SPE sample preparation for cleanup of SDS could be effectively achieved based on this concept. Samples prepared with trimethylchlorosilane methylated silica particles in the tailored SPE produced a desirable LC separation and low detection limits for the pesticide analytes. The linear calibration range extended from 0.1 up to 40 μg L ( R = 0.9906-0.9998, n = 6). Low limits of quantitation for the 11 pesticides were achieved (0.027-0.090 μg L). The precision of the proposed method for the 11 analytes was less than 10%. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A novel method of functionalized polymer grafting onto nanographite using cyanuric chloride and allyl amine is reported. The polymer-grafted nanographite was characterized in depth using Fourier transform infrared spectroscopy, elemental analysis (CHN), thermogravimetric analysis, and scanning electron microscopy. This polymer-grafted nanographite was used for the solid-phase extraction of trace enrofloxacin in biological fluids and pharmaceutical samples. The profile of enrofloxacin uptake by the polymer-grafted nanographite reflected the high accessibility of the interaction sites in the polymer. The sorption capacity of the polymer-grafted nanographite was 24.4 µmol g at the identified optimum pH of 6 and at 20 °C, according to Scatchard analysis. The equilibrium adsorption data for enrofloxacin on grafted nanographite were analyzed using Langmuir, Freundlich, Temkin, and Redlich-Peterson models. Recoveries of 68.5, 91.6, and 81.2 % were obtained in the extraction of trace enrofloxacin in human serum, urine, and pharmaceutical samples, respectively. The calibration curves were linear ( R ≥ 0.997) in the concentration range 0.1-60 μg mL for enrofloxacin. The limit of detection for enrofloxacin was 8.5 ng mL. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS)-based profiling of serum peptides for biomarker discovery purposes and comparative analyses of clinical cohorts has been widely applied on surface-enhanced laser desorption/ionization- and matrix-assisted laser desorption/ionization (MALDI)-platforms. Most commonly, these strategies involve a single-step sample clean-up procedure and time-of-flight MS readout. Previously, we have developed fully automated high-throughput magnetic bead-based solid-phase extraction (SPE) procedures to enable peptide and protein profiling studies. In this study, it will be shown that the combination of SPE with MALDI and ultrahigh resolution Fourier transform ion cyclotron resonance MS provides a next-generation platform that allows such profiling up to molecular weights of 15 kDa with full isotopic resolution for each species. Beneficial aspects of using ultrahigh resolution MS for MALDI profiling are mass precision and spectral alignment, resolving overlapping signals, and identification (structure characterization) of differentiating features. [ABSTRACT FROM AUTHOR]

A comprehensive analytical method based on ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) has been developed for the simultaneous determination of 22 regulated coumarin derivatives in cosmetics. Various categories of cosmetic samples (creams, lotions, shampoos, and lipsticks) were subjected to optimized ultrasound-assisted extraction and solid-phase extraction procedures, which enabled exhaustive extraction of target analytes and efficient cleanup of sample matrices prior to instrumental analysis. The rapid chromatographic separation of the 22 coumarin derivatives was performed on a sub-2 µm Waters ACQUITY UPLC BEH C column (50 mm × 2.1 mm, 1.7 µm), preceded by a pre-column of the same packing material within 5 min. The entire column eluent from UPLC was directed into a triple quadrupole mass spectrometer with an electrospray ionization source. The MS/MS data acquisition was conducted under the mode of multiple reaction monitoring (MRM) with two precursor-product ion transitions recorded but only one used for quantitation. The proposed method was validated in terms of matrix effects, linearity, sensitivity, accuracy, precision, specificity, and stability, and could be applied for the screening and monitoring of these prohibited or restricted coumarin derivatives in cosmetics to ensure consumers' health and protection. [ABSTRACT FROM AUTHOR]

Solid-phase extraction followed by dispersive liquid-liquid microextraction (SPE-DLLME) technique has been developed as a new analytical approach for extracting, cleaning up and preconcentrating benzaldehyde, a toxic oxidation product of the widely used preservative and co-solvent benzyl alcohol, in injectable formulation solutions. SPE of benzaldehyde from samples was carried out using C sorbent. After the elution of benzaldehyde from the sorbent by using acetonitrile, DLLME technique was performed on the obtained solution. Benzaldehyde was preconcentrated by using DLLME technique. Thus, 1.5 mL acetonitrile extract (disperser solvent) and 55.0 µL 1,2-dichloroethane (extraction solvent) were added to 5 mL ultra pure water and a DLLME technique was applied. Several variables that govern the proposed technique were studied and optimized. Under optimum conditions, the method detection limit (LOD) of benzaldehyde calculated as three times the signal-to-noise ratio (S/N) was 0.08 µg L. The relative standard deviation (RSD) for four replicates was 5.8 %. The calibration graph was linear within the concentration range of 0.5-500 µg L for benzaldehyde. The proposed method has been successfully applied to the analysis of the benzaldehyde in injectable formulation solutions (diclofenac, vitamin B-complex and voltaren) and the relative recoveries were between 88 and 92 % and show that matrix has a negligible effect on the performance of the proposed method. [ABSTRACT FROM AUTHOR]

In this work we demonstrated analytical capability of micro-planar (micro-TLC) technique comprising one and two-dimensional (2D) separation modes to generate fingerprints of environmental samples originated from sewage and ecosystems waters. We showed that elaborated separation and detection protocols are complementary to previously invented HPLC method based on temperature-dependent inclusion chromatography and UV-DAD detection. Presented 1D and 2D micro-TLC chromatograms of SPE (solid-phase extraction) extracts were optimized for fast and low-cost screening of water samples collected from lakes and rivers located in the area of Middle Pomerania in northern part of Poland. Moreover, we studied highly organic compounds loaded in the treated and untreated sewage waters obtained from municipal wastewater treatment plant 'Jamno' near Koszalin City (Poland). Analyzed environmental samples contained number of substances characterized by polarity range from estetrol to progesterone as well as chlorophyll-related dyes previously isolated and pre-purified by simple SPE protocol involving C18 cartridges. Optimization of micro-TLC separation and quantification protocols of such samples were discussed from the practical point of view using simple separation efficiency criteria including total peaks number, log(product Δ hR), signal intensity and peak asymmetry. Outcomes of the presented analytical approach, especially using detection involving direct fluorescence (UV366/Vis) and phosphomolybdic acid (PMA) visualization are compared with UV-DAD HPLC-generated data reported previously. Chemometric investigation based on principal components analysis revealed that SPE extracts separated by micro-TLC and detected under fluorescence and PMA visualization modes can be used for robust sample fingerprinting even after long-term storage of the extracts (up to 4 years) at subambient temperature (−20 °C). Such approach allows characterization of wide range of sample components that are present in given extract in high and middle concentration range. Due to protocol simplicity and low cost of analysis this method can be useful for preliminary sample screening. [ABSTRACT FROM AUTHOR]

A solid-phase extraction (SPE) using graphene as adsorbent coupled with capillary zone electrophoresis method was developed for the determination of four sulfonamide residues (sulfadimidine, sulfadimethoxine, sulfathiazole and sulfadiazine) in meat sample. Several condition parameters, such as elution solvents and volumes, sample pH and sample volume were optimized to obtain high SPE recoveries and extraction efficiency. Intra-day precisions of sulfonamides were in the range of 2.5-2.6 % and the inter-day precisions of sulfonamides were in the range of 2.6-3.4 %. Recoveries were 60.9-66.6 % for sulfadiazine and 86.1-111.4 % for other three sulfonamides in spiked meat sample. The developed method was successfully applied for the determination of sulfonamides in meat samples. [ABSTRACT FROM AUTHOR]

In this paper, amino-modified nanoporous silica (APS-SBA-15) was synthesized as a new solid-phase sorbent for the extraction of glycolic acid, monochloroacetic acid, and dichloroacetic acid in synthetical betaine products. Octadecyl silica cartridge was used to reduce the concentration of matrix betaine. PS-Ag pre-treatment cartridge was applied to remove high Cl concentration. The obtained effluent sample was passed through of the APS-SBA-15 sorbent. The effect of pH, flow rate of sample and eluent, and type and volume of the eluent were investigated and optimized. Chloroacetate and glycolate were eluted with 0.8 mol L solution of HClO and measured by HPLC with a UV-vis detector. At optimum effective parameters, preconcentration factor of 129 was achieved in this method. The detection limits of mono- and dichloroacetic acid and glycolic acid were 13, 3.7, and 8.6 ng L, respectively. [ABSTRACT FROM AUTHOR]

A simple signal derivatization based on mathematical derivatization was demonstrated to overcome the resolution problem in liquid chromatographic separation of fluoroquinolone antibiotics. A reversed-phase Symmetry C18 column with gradient mobile phase of acetonitrile and formic acid was used for separation. The studied fluoroquinolones were detected using a fluorescence detector at excitation and emission wavelengths of 280 and 450 nm, respectively. The chromatographic resolution was improved after plotting the first-derivative chromatogram without any further optimization of the experimental conditions. Milk samples were treated by preliminary protein precipitation with an acetonitrile-formic acid mixture followed by solid-phase extraction using an Oasis HLB cartridge. Good recoveries were obtained for all analytes and the limits of detection were 15-20 μg L. The results demonstrated adequate sensitivity and selectivity to allow quantification of fluoroquinolones in various milk products. [ABSTRACT FROM AUTHOR]

Bleeding of the SPE column, resulting in sample contamination, is not often a focus of attention. However, such problems can be relevant in sample purification procedures. In this work SPE method was optimized in order to clean up an atrazine soil aqueous solution, which is usually needed to quantify this pollutant to follow its sorption into soils. During this optimization a sorbent bleeding was witnessed, resulting in sample contamination. This unexpected event led us to the bleeding evaluation of different SPE cartridges commonly used in analytical chemistry laboratory experimental procedures. Using the same conditioning and elution protocol in five different commercial SPE cartridges, only the Oasis cartridge did not present any sorbent leaching and subsequent eluate contamination. [ABSTRACT FROM AUTHOR]

simple and reliable analytical method for fluroxypyr-meptyl residues in wheat and soil was established. The residual levels and dissipation rates of this pesticide in wheat and soil were determined by gas chromatography with electron capture detector (GC-ECD). Samples of wheat grains and soil were extracted with methanol-water, and then liquid-liquid partitioned with dichloromethane. The extracts were further cleaned up by solid-phase extraction (SPE) with Florisil cartridges (500 mg, 3 mL), and eluted with petroleum ether-acetic ether (95/5, v/v). The eluate was collected and concentrated for GC-ECD analysis. The results showed good linearity ( r = 0.999) over the concentration range of 0.01-1.0 μg mL. Limits of quantification (LOQ) of the method were 0.005 mg kg for both soil and wheat grains. Average recoveries for the wheat grains and soil samples were 84.45-108.2% and 95.33-106.6%, respectively, and the corresponding relative standard deviations (RSDs) of the recovery data were 0.819-3.77% and 1.55-5.28% for the three fortified levels (0.005, 0.1, 0.5 mg kg). The half-life of fluroxypyr-meptyl in soil from experimental field was 1.93 days (in Beijing) and 3.01 days (in Tianjin). The final residue of the pesticide in wheat and soil was lower than 0.005 mg kg, respectively, at harvest time. The analytes in real samples were further confirmed by gas chromatography-mass spectrometry (GC-MS). It was demonstrated that the proposed method was simple and efficient, and particularly suitable for detecting fluroxypyr-meptyl residues in wheat and soil. [ABSTRACT FROM AUTHOR]

Solid-phase extraction (SPE) coupled with high-performance liquid chromatography-fluorescence detection (LC-FL) was developed for the determination of three thiol compounds including glutathione, cysteine and acetylcysteine. 4-(Aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole was used for derivatization of thiols. Factors affecting derivatization and extraction efficiency were optimized. Sample solution (2 mL) was extracted on a SPE column for 2 min and then eluted with 400 μL methanol. The analytes were injected onto the LC system for separation on a C column, and eluted with methanol-acetate buffer. The analytes were detected by fluorescence at an emission wavelength of 515 nm with excitation at 385 nm. The linearity of the method was in the range of 0.1-60 μM, with correlation coefficients ranging from 0.9979 to 0.9990. The detection limits of the method were in the range of 5-20 nM. The proposed method was applied to the analysis of human plasma samples with recoveries of 86-112.9%. [ABSTRACT FROM AUTHOR]

sensitive and selective analytical method for the quantification of pregabalin, sildenafil and the active desmethyl metabolite of sildenafil (UK-103320) has been developed. The method can simultaneously quantify the three analytes within the expected in vivo concentration ranges using 50 μL of rat plasma. It utilises solid-phase extraction followed by high performance liquid chromatography coupled with tandem mass spectrometry. Quantitation in rat plasma demonstrated good accuracy and precision over the following dynamic ranges for each analyte: pregabalin (70-10,000 ng mL), sildenafil (1-2,000 ng mL) and UK-103320 (1-2,000 ng mL). For each analyte, the following lower limits of quantitation were obtained: 70 ng mL for pregabalin and 1 ng mL for sildenafil and UK-103320, respectively. The method was successfully used to analyse plasma samples from rats when pregabalin and sildenafil were administered in combination. [ABSTRACT FROM AUTHOR]

We present the validation of a multiresidue method for the concurrent SPE of organochlorine (OCP) and phenoxy-acidic pesticides (PA) in river water. The two classes of compounds show very different chemical characteristics. The analyses were performed by gas chromatography-mass spectrometry and by liquid chromatography-electrospray ionization-mass spectrometry. The method was validated at three different concentrations: method limit of quantitation, 0.5 and 5 μg L. The recoveries were in the range 65-135% for all the target compounds and in the range 83-113% with RSD <20% for most of them at all the concentrations tested. The method showed good accuracy, precision, and sensitivity, and allowed the analysis of the selected pesticides at a concentration lower than that required by the EU current legislation for surface water []. The single-step procedure reduced artifacts, matrix effects, and speeded up sample preparation. [ABSTRACT FROM AUTHOR]

method has been developed for analysis of 14 organochlorine pesticide residues in cereals. After accelerated solvent extraction and solid-phase extraction clean-up on graphitized carbon black/primary-secondary amine (GCB/PSA), to reduce co-extraction of interferences, pesticide residues were analyzed by gas chromatography with electron-capture detection. When the method was validated, recoveries were in the range 78-116%, relative standard deviations were in the range 1.1-16.3%, and limits of detection and quantification were from 1.5 to 4.2 μg kg and from 4.6 to 12.5 μg kg, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a highly selective Sudan IV molecularly imprinted polymer was synthesized by surface molecular imprinting technique in combination with a sol-gel process using γ-aminopropyl triethoxysilane as functional monomer, tetraethoxysilane as cross-linker and activated silica gel as support material. The imprinted polymer was characterized by FT-IR spectra, scanning electron micrograph and adsorption experiments and it was exhibited good recognition and selective ability, offered a faster rate for the adsorption of Sudan IV. Using the imprinted material as sorbent, a solid-phase extraction coupled with high-performance liquid chromatography method for determination of trace Sudan IV was presented. The detection limit ( S/ N = 3) was 25.2 ng L, and the RSD for five replicate was 2.86%. With a loading flow rate of 2.5 mL min for loading 30 mL, an enrichment factor of 104 was achieved. This method was applied for extraction and determination of chilli powder and duck egg samples with good recoveries ranging from 85.3 to 98.1%. [ABSTRACT FROM AUTHOR]

Ionic liquid-modified silica, with functional groups based on imidazole as the cation, was obtained. A molecular imprinting technique was introduced to form the order of functional groups. The selectivity of the obtained ionic liquid-modified silica was successfully used as a special imprinted sorbent in the solid-phase extraction to isolate cryptotanshinone, tanshinone I and tanshinone IIA from Salvia miltiorrhiza Bunge. Several washing and elution solvents with different polarities were evaluated. The ionic liquid-modified silica as the sorbent exhibited a higher selectivity than blank ionic liquid-modified silica, traditional silica and C cartridges. A quantitative analysis was conducted by liquid chromatography with a C column and methanol/water (75:25, v/v, containing 0.5% acetic acid) as the mobile phase. A good linearity was obtained from 0.5 × 10 to 0.1 mg mL ( r > 0.99) with relative standard deviations that were less than 4.6%. [ABSTRACT FROM AUTHOR]

rapid, precise, accurate, and selective high-performance liquid chromatographic method with fluorescence detection has been validated and used for analysis of amisulpride in human plasma after a simple solid-phase extraction procedure. Compounds were separated on a CN column with 0.03 M potassium dihydrogen phosphate (pH 6.5)-acetonitrile 65:35 ( v/ v) as mobile phase. Fluorescence detection was performed at excitation and emission wavelengths of 274 and 370 nm, respectively. Calibration plots were linear over the concentration range 10-1,000 ng mL in human plasma, and the lower limit of quantification was 10 ng mL. Accuracy was between 0.4 and 6.4% and precision was between 3.1 and 7.5%. Amisulpride was sufficiently stable through three freeze-thaw cycles, during storage for 6 h at room temperature, and for 2 months at −22 °C. The method is suitable for the analysis of clinical samples from pharmacokinetic studies. [ABSTRACT FROM AUTHOR]

Solid-phase extraction coupled with LC-fluorescence detection was used for the extraction and determination of three thiol compounds including glutathione (GSH), cysteine (Cys) and acetylcysteine (NAc). Fluorescence probe N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza- s-indacene-3-yl)methyl)iodoacetamide (BODIPY Fl-C-IA) was applied for derivatization of thiols. The derivatization and extraction conditions have been investigated in detail. The calibration graph of the proposed method was linear in the range of 1-200 nM (GSH and Cys) and 20-2,000 nM (NAc). The limits of detection were in the range of 0.2-4.0 nM. The usefulness of the proposed method has been validated by measuring thiol-containing compounds in human urine and blood samples from healthy persons, with recoveries of 92.5-110%. [ABSTRACT FROM AUTHOR]

method for the simultaneous determination of 11 triazine herbicides residues in river water has been developed. It involves solid-phase extraction (SPE) pretreatment step and rapid resolution liquid chromatography-tandem mass spectrometry (RRLC-MS-MS). In the SPE pretreatment step, the adsorptive performance of MWCNTs material as SPE adsorbent and the elution capability of five kinds of solvents were investigated; in the LC separation step, a rapid resolution high throughput LC column, was used and the gradient elution mode adopted. The linear correlation coefficients ( r) of the method for 11 target analytes varied between 0.9930 and 0.9980, the mean recoveries were in the range of 73.0 and 98.0% with relative standard deviations (RSD) 2.6 ~ 4.2%, the method detection limits (MDL) were all below 0.1 ng L. An expanded uncertainty of not more than 20% was estimated for each analyte at the spiked concentration of 4.0 μg L. The proposed method was applied to the determination of the residue concentrations of 11 pollutants in Songhuajiang River water. [ABSTRACT FROM AUTHOR]

fast and simple fractionation method was optimized to selectively separate oxy-PAH from polycyclic aromatic hydrocarbons (PAH) and n-alkanes contained in solvent extracted organic matter (SEOM) from atmospheric particles with an aerodynamic diameter ≤2.5 μm (PM). Samples were collected in Mexico City. Multivariate parameters were adjusted on a standard mixture, and on SEOM spiked with pure standard mixture solutions: type and amount of phase; packing densities; type, proportion and amount of solvents, and elution flow rates were tested under several elution schemes. Cyanopropylsilyl-bonded phase material was the selected stationary phase. The separation method was applied to real samples of SEOM (2.6, 5.6 and 8.5 mg) spiked with n-alkanes, PAH and oxy-PAH. n-Alkanes overlapped with PAH due to an excess of n-alkanes in real samples overloading the capacity of the stationary phase. Oxy-PAH was separated totally from n-alkanes and PAH. Mean recoveries ± confidence intervals (95%) for n-alkanes ranged from 53 ± 17% ( n-tetracontane) to 101 ± 11% ( n-hexacosane); for PAH from 58 ± 5% (phenanthrene) to 85 ± 9% (benzo[ k]fluoranthene); and for oxy-PAH from 68 ± 12% (9,10-dihydrobenzo[ a]pyren-7(8 H)one) to 108 ± 9% (1,2-benzopyrone). This method is an efficient fractionation procedure to be applied to oxy-PAH, PAH and n-alkanes in complex organic mixtures extracted from PM. [ABSTRACT FROM AUTHOR]

The tissue distribution of wogonin was investigated for study of its anticancer activity. A robust, reliable, and sensitive LC method was developed for simultaneous analysis of wogonin and its major metabolite, wogonoside, in tissues of tumor-bearing nude mice. To reach the required level of detection in different tissues, sample pretreatment was by solid-phase extraction. Good LC separation was achieved on a C column with methanol-0.5% formic acid 68:32 ( v/ v) as mobile phase. UV detection was performed at 275 nm and calibration plots for both analytes were linear over the range 0.16-80.0 μg g for all the biological samples studied with correlation coefficients >0.9980. Inter-day and intra-day precision were no more than 15% at the limit of quantification and 10% at other concentrations; recovery from all tissues was 92.3-101.4% for wogonin and 66.7-74.3% for wogonoside. The method was ideal for this tissue distribution study and results obtained reflect the potential of wogonin for further pharmaceutical development as an anticancer agent. [ABSTRACT FROM AUTHOR]

robust and sensitive method was developed for the simultaneous analysis of metribuzin and quizalofop- p-ethyl residues in potato and soil, based on solid-phase extraction (SPE) coupled to capillary gas chromatography with electron capture detector (GC-ECD). Residues of two herbicides were extracted from potato and soil with acetone and methanol-water, followed by SPE to remove coextractives, before analysis by GC-ECD. SPE procedures were performed on Florisil cartridges (500 mg, 3 mL), the analytes from potato and soil matrix were eluted with petroleum ether-acetic ether (9:1 v/v, 5 mL) and petroleum ether-acetic ether (8:2 v/v, 2 mL), respectively. Limits of quantification of the method were 0.01 mg kg, and the mean recoveries ranged from 72.9 to 109.5% with relative standard deviation ranging from 0.7 to 9.2% at the three spike levels (0.01, 0.1, and 0.5 mg kg). The proposed method was successfully applied to the analysis of metribuzin and quizalofop- p-ethyl residues in potato and soil samples from an experimental field. Direct confirmation of the analytes in real samples was achieved by gas chromatography-mass spectrometry (GC-MS). [ABSTRACT FROM AUTHOR]

n effective and rapid method was developed for simultaneous determination of seven sulfonylurea herbicides in environmental water using multiwalled carbon nanotubes as solid-phase extraction sorbent coupled with liquid chromatography–tandem mass spectrometry. Important parameters influencing the extraction efficiency such as pH of the sample solution, flow rate of sample loading, the eluent and its volume were optimized. Under optimum conditions, good linearity was obtained for all herbicides ( r > 0.99) over the range of 0.05–5,000 ng L, and precisions (RSD) for nine replicate measurements of a standard mixture of 200 ng L were 1.9–7.4%. The limits of detection and quantification were 0.01–0.20 and 0.05–1.00 ng L, respectively. The proposed method was successfully applied to the analysis of tap water, spring water, ground water and well water, and mean recoveries for seven analytes at three spiked concentration levels were from 81.5 to 110.5% with RSDs between 0.3 and 7.0%. The results showed that the established method has wide application to analyze sulfonylurea herbicides at trace level in water. [ABSTRACT FROM AUTHOR]

A new method was developed for the analysis of herbicide mefenacet (MN) and its three photolysis degradation products namely hydroxylbenzothiazole (HBT), N-methylaniline (N-MA) and 2-benzothiazoloxyacetic acid (2-BAA) in water samples by rapid resolution liquid chromatography coupled with UV detection and electrospray ionization mass spectrometry. In the SPE pre-concentration step, the adsorptive potential of oxidized multi-walled carbon nanotubes for the extraction of these four target analytes was investigated for the first time. Parameters influencing the extraction efficiency, such as sample flow-rate, eluent volume and sample volume, were examined. The mean recoveries were between 85.6 and 101.4% and relative standard deviations were between 3.0 and 9.2%. The limits of detection obtained were 0.02 μg L−1 for MN and 2-BAA and 0.04 μg L−1 for HBT and N-MA. The proposed method was applied to monitor the residual concentrations of these four target analytes in 39 real water samples collected from April to July of 2009. [ABSTRACT FROM AUTHOR]

A rapid and sensitive reversed-phase high-performance liquid chromatographic method for analysis of fexofenadine in human plasma has been developed and optimized. The analytes were extracted from biological samples by solid-phase extraction on hydrophilic–lipophilic balance cartridges. LC separation was performed on a C18 analytical column (125 mm × 4 mm i.d., 5-μm particles) with 42:58 ( v/ v) acetonitrile–water adjusted to pH 2.7 with 85% orthophosphoric acid as mobile phase. Fluorescence detection was performed with excitation at 230 nm and emission at 290 nm. The total time for chromatographic separation was 7 min. The method was validated in accordance with EU guidelines by analysis of plasma samples fortified with fexofenadine at concentrations between 0.05 and 800 ng mL−1. Calibration plots were linear in this range. Mean recovery was typically 94.03% and the detection limit was 0.05 ng mL−1. The time required for quantitative analysis is shorter than that required by other methods. [ABSTRACT FROM AUTHOR]

Solid-phase extraction using automated equipment has been applied to different types of wine (red, white, sparkling and rosé) spiked with 16 organochlorine pesticides (OCPs) for their preconcentration. PRPS, Oasis HLB, Hysphere Resin SH, Resin GP, C8 and C18 sorbent cartridges were tested. The separation–detection step was carried out by gas chromatography–tandem mass spectrometry. Changes in both the volume flushed through the sorbent (ranging between 25 and 100 mL) and the volume injected into the chromatograph (1 or 10 μL) allow the detection limits of the method to be adapted to the analytes contents in the target samples. Preconcentrating 100 mL of wine and injecting into the chromatrograph 10 μL of extract, limits of detection obtained for the OPCs range between 1.7 and 9.7 ng L−1, depending on the OCP and type of wine. [ABSTRACT FROM AUTHOR]