Sorbent For Dispersive Solid-phase Extraction Research Articles

Graphene oxide–polyaniline nanocomposite as a potential sorbent for dispersive solid-phase extraction and determination of selected pharmaceutical and personal care products in wastewater samples using HPLC with a diode-array detector

A graphene oxide–polyaniline nanocomposite was proposed for the dispersive solid-phase extraction of six pharmaceutical and personal care products in wastewater matrices.

Selective extraction and release using (EDTA-Ni)-layered double hydroxide coupled with catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine for sensitive detection of copper ion

Copper is an important heavy metal in various biological processes. Many methods have been developed for detecting of copper ions (Cu2+) in aqueous samples. However, an easy, cheap, selective and sensitive method is still desired. In this study, a selective extraction-release-catalysis approach has been developed for sensitive detection of copper ion. Ethylenediaminetetraacetic acid (EDTA) chelated with nickel ion (Ni2+) were intercalated in a layered double hydroxide via a co-precipitation reaction. The product was subsequently applied as sorbent in dispersive solid-phase extraction for the enrichment of Cu2+ at pH 6. Since Cu2+ has a stronger complex formation constant with EDTA, Ni2+ exchanged with Cu2+ selectively. The resulting sorbent containing Cu2+ was transferred to catalyze the 3,3′,5,5′-tetramethylbenzidine oxidation reaction, since Cu2+ could be released by the sorbent effectively and has high catalytic ability for the reaction. Blue light emitted from the oxidation product was measured by ultraviolet–visible spectrophotometry for the determination of Cu2+. The extraction temperature, extraction time, and catalysis time were optimized. The results showed that this method provided a low limit of detection of 10nM, a wide linear range (0.05–100μM) and good linearity (r2=0.9977). The optimized conditions were applied to environmental water samples. Using Cu2+ as an example, this work provided a new and interesting approach for the convenient and efficient detection of metal cations in aqueous samples.

Synthesis of a graphene-based nanocomposite for the dispersive solid-phase extraction of vancomycin from biological samples.

The approach of this work was to study the capability of graphene-based materials in the field of biological sample preparation. A polypyrrole/graphene composite was synthesized and characterized. The potential of the nanocomposite was investigated as a sorbent in dispersive solid-phase extraction followed by high-performance liquid chromatography with UV detection for vancomycin as a model drug. The effect of different parameters influencing extraction efficiency such as sample pH and sample volume, ionic strength, extraction time, type, and volume of desorption solvent and desorption time were investigated. A comparison study was also conducted between polypyrrole/graphene and some different novel and classic sorbents. Under optimized conditions, the calibration curve for vancomycin showed linearity in the range of 0.05-10 μg/mL. In addition, limits of detection, and quantification were 0.003 and 0.01 μg/mL, respectively. The intraday and interday relative standard deviations at a concentration of 0.05 μg/mL (n = 3) were 1.6 and 2.1%, respectively. Furthermore, the proposed method was successfully applied for the determination of vancomycin in plasma and urine samples. The relative recoveries indicated the feasibility of graphene-based sorbents in biological sample analysis.

In-syringe dispersive solid-phase extraction using dissolvable layered double oxide hollow spheres as sorbent followed by high-performance liquid chromatography for determination of 11 phenols in river water

Layered double oxide hollow spheres (LDO-HSs) were synthesized and employed as a dissolvable sorbent in dispersive solid-phase extraction (DSPE) to extract eleven United States Environmental Protection Agency's priority phenols from aqueous samples. With their higher specific surface area, LDO-HSs showed much higher extraction efficiency than normal layered double hydroxides and layered double oxides. The entire extraction process was accomplished in a syringe. After DSPE, the sorbent with the analytes was isolated conveniently by directly expelling the spent sample solution out of the syringe. The analyte-enriched sorbent was then subsequently dissolved by withdrawing an acidic solution into the syringe. The final extract was analyzed by high-performance liquid chromatography with ultraviolet detection. The results showed that this method provided low limits of detection for the phenols (0.005–0.153μg/L), good linearity (r2≥0.9956) and relative standard deviations of ≤6.7%. The optimized method was applied to water samples from 3 rivers. This simple extraction procedure was demonstrated to be a fast, efficient and convenient DSPE approach.

Ultrathin-shell boron nitride hollow spheres as sorbent for dispersive solid-phase extraction of polychlorinated biphenyls from environmental water samples

Boron nitride hollow spheres with ultrathin-shells were synthesized and used as sorbents for dispersive solid-phase extraction of aromatic pollutants at trace levels from environmental water samples. Polychlorinated biphenyls (PCBs) were selected as target compounds. Sample quantification and detection were performed by gas chromatography–tandem mass spectrometry. Extraction parameters influencing the extraction efficiency were optimized through response surface methodology using the Box–Behnken design. The proposed method achieved good linearity within the concentration range of 0.15–250ngL−1 PCBs, low limits of detection (0.04–0.09ngL−1, S/N=3:1), good repeatability of the extractions (relative standard deviation, <12%, n=6), and satisfactory recoveries between 84.9% and 101.0% under optimal conditions. Real environmental samples collected from rivers, local lakes, rain and spring waters were analyzed using the developed method. Results demonstrated that the hexagonal boron nitride-based material has significant potential as a sorbent for organic pollutant extraction from environmental water samples.

Multiresidue analysis of 16 pesticides in jujube using gas chromatography and mass spectrometry with multiwalled carbon nanotubes as a sorbent.

Although jujube is a minor crop and very few pesticides are registered on it, the application of pesticides during the growth stage of jujube is inevitable to control the pests or diseases. This situation has led to pesticide misuse. A modified quick, easy, cheap, effective, rugged, and safe method using a novel sorbent, multiwalled carbon nanotubes, as a dispersive solid-phase extraction sorbent combined with gas chromatography with mass spectrometry, was developed for the determination of 16 pesticides in jujube. Under the optimized conditions, recoveries of 76.7-112.4% were obtained for the target analytes at three spiked concentration levels. The relative standard deviations ranged from 1.2 to 12.3%. Limits of detection and limits of quantification for 16 pesticides ranged from 1 to 10 and 3 to 30μg/kg, respectively. The residues of chlorpyrifos, hexaconazole, tebuconazole, and cyhalothrin were detected from samples obtained from the market.

Application of Dissolvable Layered Double Hydroxides As Sorbent in Dispersive Solid-Phase Extraction and Extraction by Co-Precipitation for the Determination of Aromatic Acid Anions

Three types of magnesium-aluminum layered double hydroxides were synthesized and employed as solid-phase extraction (SPE) sorbents to extract several aromatic acids (protocatechuic acid, mandelic acid, phthalic acid, benzoic acid, and salicylic acid) from aqueous samples. An interesting feature of these sorbents is that they dissolve when the pH of the solution is lower than 4. Thus, the analyte elution step, as needed in conventional sorbent-based extraction, was obviated by dissolving the sorbent in acid after extraction and separation from the sample solution. The extract was then directly injected into a high-performance liquid chromatography-ultraviolet detection system for analysis. In the key adsorption process, both dispersive SPE and co-precipitation extraction with the sorbents were conducted and experimental parameters such as pH, temperature, and extraction time were optimized. The results showed that both extraction methods provided low limits of detection (0.03-1.47 μg/L) and good linearity (r(2) > 0.9903). The optimized extraction conditions were applied to human urine and sports drink samples. This new and interesting extraction approach was demonstrated to be a fast and efficient procedure for the extraction of organic anions from aqueous samples.

Simultaneous determination of six resorcylic acid lactones in feed using liquid chromatography–tandem mass spectrometry and multi-walled carbon nanotubes as a dispersive solid phase extraction sorbent

A simple and cost-effective pre-treatment procedure was developed for six resorcylic acid lactones (RALs) in feed using dispersive solid phase extraction (dSPE) with multi-walled carbon nanotubes (MWCNTs). The sample was analysed after purification by ultra-high performance liquid chromatography–negative electrospray ionisation tandem mass spectrometry (UHPLC–ESI-MS/MS). After extraction with acetonitrile/water (80:20, v/v) and dilution with water, a dSPE procedure was carried out with MWCNTs. The pH value of the extract, the extraction time for MWCNTs, the type and amount of MWCNTs and the type of eluent were optimised to increase the sample throughput and the sensitivity. The samples were quantified using the internal standard zearalenone-D6. The absolute recoveries of the target compounds from feed samples were most efficient when using 100mg of MWCNTs with an outer diameter of less than 8nm and a length of 10–30μm, and ethyl acetate was shown to be the most suitable solvent for desorbing the target compounds from the MWCNTs. The mean recoveries from fortified swine mixed feed samples ranged from 95.3% to 107.2% and had relative standard deviations lower than 10%; the limits of detection and quantification for RALs were in the ranges of 0.20–0.29μg/kg and 0.54–0.78μg/kg, respectively.

Simultaneous determination of 10 β2-agonists in swine urine using liquid chromatography–tandem mass spectrometry and multi-walled carbon nanotubes as a reversed dispersive solid phase extraction sorbent

A simple and inexpensive pretreatment procedure was developed for 10 β2-agonists (clenbuterol, ractopamine, salbutamol, bambuterol, penbuterol, tulobuterol, clorprenaline, mabuterol, cimaterol and terbutaline) in swine urine using dispersive solid phase extraction (dSPE) with multi-walled carbon nanotubes (MWCNTs). The sample was analysed after purification by ultra high performance liquid chromatography–positive electrospray ionisation tandem mass spectrometry (UHPLC-ESI–MS/MS). The pH value of the swine urine, extraction time, type and amount of MWCNTs and type of eluent were optimised to increase the sample throughput and sensitivity. The samples were quantified using clenbuterol-D9, ractopamine-D6 and salbutamol-D3 as internal standards. The recoveries of the target compounds from swine urine samples at pH 10.0 were most efficient when using 20mg of MWCNTs with a 30–50nm outer diameter and a length of 10–30μm, while a mixture of water/methanol (90:10, v/v) with 0.5% formic acid was shown to be the most suitable solvent for desorbing the compounds from the MWCNTs. The proposed method was validated according to the European Commission Decision 2002/657/EC, which determines linearity, specificity, decision limit (CCα), detection capability (CCβ), recovery, precision and stability.

Rapid Determination of Chlormequat in Meat by Dispersive Solid-Phase Extraction and Hydrophilic Interaction Liquid Chromatography (HILIC)–Electrospray Tandem Mass Spectrometry

A rapid method for analyzing trace levels of chlormequat (CQ) in meat samples by hydrophilic interaction liquid chromatography (HILIC)-electrospray tandem mass spectrometry was developed. The samples were extracted with acetonitrile, followed by a rapid cleanup through a dispersive solid-phase extraction (DSPE) technique with octadecyl (C18) DSPE sorbents. The chromatographic separation was achieved within 6 min using a HILIC column with 10 mM ammonium acetate and 0.1% (v/v) formic acid in water/acetonitrile (v/v, 40:60) as the mobile phase. Quantification was performed using a matrix-matched calibration curve, which was linear in the range of the 0.05-100 μg/L. The limit of detection (LOD) was estimated at 0.03 μg/kg for CQ on the basis of a peak to peak signal noise (S/N = 3). The limit of quantification (LOQ) was 0.1 μg/kg on the basis of the lowest spiked concentration with suitable precision and accuracy. The average recovery of CQ in spiked meat samples was 86.4-94.7% at 2, 20, and 200 μg/kg. Finally, this method was applied to determine CQ in the livestock and poultry meats purchased from markets in Beijing in 2011. CQ was detected in all 12 samples, and the concentration was 0.4-636.0 μg/kg. Concentrations in a chicken sample (636.0 μg/kg) and a goat meat sample (486.0 μg/kg) were found to be 15.9 and 2.43 times the corresponding Codex maximum residue limits, respectively.

Rational design of core–shell molecularly imprinted polymer based on computational simulation and Doehlert experimental optimization: application to the separation of tanshinone IIA from Salvia miltiorrhiza Bunge

Computational simulation and Doehlert experimental optimization were done for the rational design of a core-shell molecularly imprinted polymer (CS-MIP) for use in the highly selective separation of Tanshinone IIA (TSIIA) from the crude extracts of Salvia miltiorrhiza Bunge (SMB). The functional monomer layer of the polymer shells directed the selective occurrence of imprinting polymerization at the surface of silica through the copolymerization of vinyl end groups with functional monomers and also drove TSIIA templates into the formed polymer shells through the charge-transfer complex interactions between TSIIA and the functional monomer layer. As a result, the maximum rebinding capacity was achieved with the use of optimal grafting ratio by the Doehlert design. The CS-MIP exhibited high recognition selectivity and binding affinity to TSIIA. When the imprinted particles were used as dispersive solid phase extraction sorbents, the recovery yield of TSIIA reached 93% by a one-step extraction from the crude extracts of SMB, and the purity of TSIIA was larger than 98% by HPLC analysis. These results show the possibility of a highly selective separation and enrichment of TSIIA from the SMB using the TSIIA-imprinted core-shell molecularly imprinted polymers.

Multiresidue determination of 160 pesticides in wines employing mixed-mode dispersive-solid phase extraction and gas chromatography–tandem mass spectrometry

A new multiresidue method for the efficient screening, identification and quantification of over 160 pesticides belonging to different chemical classes in red, rose and white wines have been developed. The analysis was based on gas chromatographic-tandem quadrupole mass spectrometric determination (GC-QqQ–MS/MS). An optimization strategy involved the selection of buffering conditions and sorbents for dispersive-solid phase extraction (dispersive-SPE) in order to achieve acceptably high recoveries and reduce co-extractives in the final extracts. As a result, the optimized procedure allowed us to obtain consistent recoveries of the target pesticides including problematic ones such as captan, chlorothalonil, dichlofluanid, folpet and tolylfluanid. The attained recoveries were typically between 80 and 110% (89% on average) with RSD values typically lower than 10% (8% on average) at three spiking levels of 0.01, 0.05 and 0.2mgkg−1. Linearity was studied in the range between 0.005 and 0.2mgkg−1 using pesticide standards prepared both in pure solvent and in the presence of matrix, showing coefficients of determination (R2) higher than 0.99 for all the pesticides except for desmedipham, thiabendazole and thiamethoxam in pure solvent. The study of the ratio of the slopes obtained in solvent and in matrix provided information about the matrix effects, which was <10%, 10–20% and >20% for 33, 36 and 31% of the studied pesticides, respectively. To improve accuracy, matrix matched standards were always used for calculation of the quantification results. The expanded uncertainties were estimated by using a “top-down” approach as being 17% on average (coverage factor k=2, confidence level 95%). Finally, the method was used with success to detect and quantify pesticide residues in commercial wines.

Determination of the nucleosides and nucleobases in Tuber samples by dispersive solid-phase extraction combined with liquid chromatography–mass spectrometry

A simple, fast and inexpensive method based on dispersive solid phase extraction (DSPE) combined with LC–MS was developed for simultaneous determination of 7 nucleosides and nucleobases (i.e., adenine, hypoxanthine, uridine, adenosine, guanine, guanosine, and inosine) in Tuber fruiting-bodies and fermentation mycelia. The DSPE procedure was firstly introduced to remove the protein interference from sample solutions, and D3520 macroporous resin was chosen as the DSPE sorbent because of its high removal capability on protein interferences, but low adsorption rate on analytes. Besides, key parameters on DSPE procedure (i.e., macroporous resin type, macroporous resin amount, methanol concentration, and vortex time) were optimized, and the protein removal efficacy could achieve about 95% after the process optimization. Though the method validation test, the DSPE-LC–MS method was confirmed to be precise, accurate and sensitive, and the column blinding problem was solved successfully. By using this established method, the total amount of nucleosides and nucleobases in the fermentation mycelia was determined to range from 4881.5 to 12,592.9 μg g −1, which was about 2–25 times higher than the fruiting-bodies (from 498.1 to 2274.1 μg g −1). The formulation of nucleosides and nucleobases in the fermentation mycelia maintained relatively constant, while the formulation in Tuber fruiting-bodies varied significantly with their species. Hierarchical cluster analysis (HCA) showed the formulation similarity of nucleosides and nucleobases between Tuber fermentation mycelia and the fruiting-bodies of Tuber indicum and Tuber himalayense. From the viewpoint of nucleosides and nucleobases, this work confirms the potentiality of Tuber fermentation mycelia as the alternative resource for its fruiting-bodies.