Sorbents For On-line Solid Phase Extraction Research Articles

Advanced nanofibrous sorbents for the extraction of pollutants from river water and protein-containing matrices

The extraction efficiencies of thirty types of fibers produced by meltblown, alternating current electrospinning, and meltblown-co-electrospinning technologies were tested as advanced sorbents for on-line solid-phase extraction in a high-performance liquid chromatography system have been tested and compared with a commercial C18 sorbent. The properties of each fiber, which were often depended on the production process, and their applicability were demonstrated with the extraction of the model analytes nitrophenols and chlorophenols from various matrices including river water and to purify complex matrix human serum and bovine serum albumin from macromolecular ballast. Polycaprolactone fibers outperformed other polymers and were selected for subsequent modifications including (i) incorporation of hybrid carbon nanoparticles, i.e., graphene, activated carbon, and carbon black into the polymer prior to fiber fabrication, and (ii) surface modification by dip coating with polyhydroxy modifiers including graphene oxide, tannin, dopamine, hesperidin, and heparin. These novel fibrous sorbents were comparable to commercial C18 sorbent and provided excellent analyte recoveries of 70–112% even from the protein-containing matrices.

Sulfonate-bonded covalent organic polymer as mixed-mode sorbent for on-line solid-phase extraction of ß2-receptor agonists

A novel sulfonate-bonded covalent organic polymer (COPTPBA-BPDA@SA) with mixed-mode interactions of hydrophobic and cation-exchange was synthesized and exploited as sorbent for on-line solid-phase extraction (on-line SPE) of ß2-receptor agonists. The successful synthesis of COPTPBA-BPDA@SA was confirmed by the characterization of SEM, XPS and FT-IR. Due to the excellent mixed-mode extraction ability towards the positively charged ß2-receptor agonists and the good anti-interference performance, COPTPBA-BPDA@SA was introduced into on-line SPE-HPLC system for selective extraction of ß2-receptor agonists in pork and pork liver. Via the optimization of the extraction condition, including formic acid percentage and ACN percentage in the sampling solution, the mixed-mode extraction mechanism of COPTPBA-BPDA@SA was investigated. The elution condition, such as the pH value, formic acid percentage and ACN percentage of the eluent was also optimized for the desired SPE performance. Under the optimized condition, COPTPBA-BPDA@SA revealed better purification performance than COPTPBA-BPDA without sulfonating. The LODs for ß2-receptor agonists were in the range of 0.08–0.22 μg/kg, and the recoveries in different samples at three spiked levels (0.4, 4.0, 8.0 μg/kg) were ranged from 83.2% to 98.5% with RSDs less than 5.2%, which indicated the satisfactory mixed-mode extraction ability of COPTPBA-BPDA@SA as well as the good applicability of the developed method.

A novel poly (NMA-co-DEA-co-EDMA) monolithic column as a sorbent for online solid-phase extraction and its application in the determination of β-sitosterol in plant oil samples.

A novel monolithic column was prepared by in-situ free radical polymerization using N-methylolacrylamide (NMA) and N,N-diethylacrylamide (DEA) as co-monomers. The monolith was characterized by scanning electron microscopy (SEM) and its nitrogen adsorption-desorption isotherm, and it was used as a solid phase extraction (SPE) absorbent for the online enrichment of β-sitosterol by high performance liquid chromatography. The optimized method had good linearity, and the linear regression coefficient was 0.998. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.006 mg/mL and 0.02 mg/mL, respectively. The interday and intraday accuracies were less than 7.28%. The spiked recoveries of β-sitosterol in the six plant oil were 90.96-103.56%. The maximum amount of β-sitosterol adsorbed on the monolithic column was 12.69 mg/g, and the enrichment factor of β-sitosterol was 78. The results showed that the monolith could be used as an online SPE absorbent for the determination of β-sitosterol in plant oil samples.

Evaluation of ionic liquids supported on silica as a sorbent for fully automated online solid-phase extraction with LC-MS determination of sulfonamides in bovine milk samples.

Sulfonamides are antibiotics widely used in the treatment of diseases in dairy cattle. However, their indiscriminate use for disease control may lead to their presence in tissues and milk and their determination requires a sample preparation step as part of an analytical approach. Among the several sample preparation techniques available, those based upon the use of sorptive materials have been widely employed. Recently, the application of ionic liquids immobilized on silica surfaces or polymeric materials has been evaluated for such an application. This manuscript addresses the evaluation of silica-based ionic liquid obtained by a sol-gel synthesis process by basic catalysis as sorbent for online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry for sulfonamides determination. Infrared vibrational spectroscopy confirmed the presence of the ionic liquid on the silica surface, suggesting that the ionic liquid was anchored on to the silica surface. Other sorbents varying the ionic liquid alkyl chain were also synthesized and evaluated by off-line solid-phase extraction in the sulfonamide extraction. As the length of the alkyl chain increased, the amount of extracted sulfonamides decreased, possibly due to a decrease in the electrostatic interaction caused by the reduction in the polarity, as well as the presence of a hexafluorophosphate anion that increases the hydrophobic character of the material. The use of 1-butyl-3-methylimidazolium hexafluorophosphate as a selective ionic liquid sorbent enabled the isolation and sulfonamide preconcentration in bovine milk by online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The limit of quantification for the method developed was 5-7, 5 μg/mL, with extraction recoveries ranging between 74 and 93% and intra- and interassay between 1.5-12.5 and 2.3-13.1, respectively.

Application of Deep Eutectic Solvent Modified Cotton as a Sorbent for Online Solid-Phase Extraction and Determination of Trace Amounts of Copper and Nickel in Water and Biological Samples.

Deep eutectic solvent (DES) was used as the extractant to improve the extraction properties of cotton. DES of choline chloride-urea (ChCl-urea) was prepared and immobilized on the surface of cotton fibers. The resulting sorbent was packed on a microcolumn, and a flow injection flame atomic absorption spectrometry was designed for the online separation and determination of trace amounts of copper and nickel. Various parameters affecting the extraction recovery of analytes such as pH, sample volume, sample loading rate, nature, volume, concentration, and flow rate of eluent were investigated and optimized. Under the optimum conditions, the method showed good linearity in the concentration range of 0.25-50.0 and 4.0-125.0μgL-1 with the coefficient of determination (r 2) of 0.9991 and 0.9990 for copper and nickel, respectively. The method was very sensitive with the detection limits (defined as 3Sb/m) of 0.05 and 0.60μgL-1 for Cu and Ni, respectively. It was successfully applied for the determination of Cu and Ni in water and biological samples. The accuracy of the method was evaluated through the recovery experiments and independent analysis by electrothermal atomic absorption spectrometry.

Zeolite imidazolate framework-8 as sorbent for on-line solid-phase extraction coupled with high-performance liquid chromatography for the determination of tetracyclines in water and milk samples

Zeolite imidazolate framework-8 (ZIF-8) was used as the novel sorbent for on-line solid-phase extraction coupled with high-performance liquid chromatography (HPLC) for the determination of oxytetracycline (OTC), tetracycline (TC) and chlorotetracycline (CTC) in water and milk samples. 390mg of ZIF-8 was packed into a stainless steel column (3cm long×4.6mm i.d.) which was mounted on the HPLC injector valve to replace the sample loop. On-line solid-phase extraction of OTC, TC and CTC was achieved by loading sample solution at a flow rate of 3.0mLmin−1 for 10min with the aid of a flow-injection system. The extracted analytes were subsequently eluted into a C18 analytical column (25cm long×4.6mm i.d.) for HPLC separation under isocratic condition with a mobile phase (10% MeOH–20% ACN–70% 0.02molL−1 oxalic acid solution) at a flow rate of 1.0mLmin−1. Under optimized conditions, the developed method gave the enhancement factors of 35–61, the linearity range of 5–1000μgL−1, the detection limits of 1.5–8.0μgL−1, quantification limits of 5.0–26.7μgL−1, uncertainties of 0.9–1.1μgL−1, and the sample throughput of 4 samples h−1. The recoveries of OTC, TC and CTC at 50μgL−1 in water and milk samples ranged from 70.3% to 107.4%.

On-Line Solid-Phase Extraction Based on Poly (Nipaam-MAA-co-EDMA) Monolith Coupled with High-Performance Liquid Chromatography for Determination of Nitrendipine and Nisoldipine in Human Urine

A solid-phase extraction absorbent material based on poly (N-isopropylacrylamide-co- methacrylic acidco-ethylene glycol dimethacrylate) [poly (NIPAAm-MAA-co-EDMA)] monolithic column was developed for the simultaneous determination of nitrendipine and nisoldipine from human urine. The morphology of monolithic column and pressure drop across the columns were characterized. The results showed excellent permeability and high selectivity. Urine samples (0.05 mL) were injected directly onto the prepared Solid-Phase Extraction (SPE) monolithic column. Most biological matrix compounds in urine were removed by on-line SPE technology, while nitrendipine and nisoldipine retained on the SPE column were effectively separated on a C18 analytical column. For all analytes, linear calibration curves were obtained over a range of 50-500 ng/mL with coefficient of correlation > 0.9996. Accuracy and precision for inter- and intra-day assay showed acceptable results for quantitative assay with Relative Standard Deviation (RSD) less than 10%. The recovery was found to be in the range of 89-102%. The results indicated that the prepared monolith was feasible to be use as an on-line SPE sorbent material and the method was especially appropriate for multi-analytes monitoring in urine samples.

Preparation and evaluation of molecularly imprinted ionic liquids polymer as sorbent for on-line solid-phase extraction of chlorsulfuron in environmental water samples

In this report, vinylimidazolium ionic liquid as a functional monomer for preparation of chlorsulfuron (CS) imprinted polymers were first studied. The imprinted materials showed high selectivity for CS, and fast kinetics so that adsorption equilibrium was achieved within 5 min. These materials have been further employed to detect trace CS from water samples by online preconcentration coupled with HPLC. The sorbent offered good linearity (0.005–30 μg L −1, r 2 > 0.99) for on-line solid-phase extraction of trace chlorsulfuron. Under the optimal experimental conditions, the recovery for chlorsulfuron was in the range of 81.0–110.1% for the water samples, with RSDs ranging from 1.2 to 7.6%.

Multiwalled Carbon Nanotubes as Sorbent for Online Solid-Phase Extraction of Resveratrol in Red Wines Prior to Fused-Core C18-Based Ultrahigh-Performance Liquid Chromatography−Tandem Mass Spectrometry Quantification

An ultrafast analytical protocol based on online solid-phase extraction (SPE)/high-performance liquid chromatography-tandem mass spectrometry for the determination of resveratrol in red wines has been developed. In the present work, multiwalled carbon nanotubes (MWCNTs) were used as SPE sorbents for the analytes' online extraction and cleanup. The target analytes were separated on a fused-core C18-silica column (Halo, 50 mm × 2.1 mm i.d., 2.7 μm) and quantified by triple-quadrupole linear ion trap mass spectrometry in negative ion multiple-reaction monitoring (MRM) mode. The proposed analytical procedures were carefully optimized and validated. The calibration function is linear from 0.37 to 370 ng mL(-1) and from 0.13 to 130 ng mL(-1) for trans- and cis-resveratrol, respectively. The limits of quantification (LOQs) of trans- and cis-resveratrol obtained were 0.05 and 0.06 ng mL(-1), which means that the proposed method is suitable for trace analysis of resveratrol at low-level concentration. At the three fortified levels (low, medium, and high), recoveries of resveratrol ranging from 76.9 to 108.3% were obtained. Eight red wine samples from different regions of China were analyzed. The results indicated that the present online SPE-LC-MS/MS system significantly increased sample throughput and decreased solvent consumption, exhibiting great potential to be applied for analyzing resveratrol in red wines.

Comparison of Hydrophilic Polymeric Sorbents for On-Line Solid-Phase Extraction of Polar Compounds from Aqueous Samples

Two 4-vinylimidazole-divinylbenzene (4VIm-DVB) polymers were synthesized and applied as sorbents for on-line solid-phase extraction (SPE) followed by liquid chromatography for analyzing polar compounds in aqueous samples. The new sorbents (4VIm-DVB) were compared to another sorbent that had been previously synthesized by our group (N-vinylimidazole-divinylbenzene (NVIm-DVB)) and to the commercial OASIS® HLB and StrataTM X.

On-line trace enrichment of phenolic compounds from water using a pyrrole-based polymer as the solid-phase extraction sorbent coupled with high-performance liquid chromatography

A pyrrole-based conductive polymer was prepared and applied as new sorbent for on-line solid-phase extraction (SPE) of phenol and chlorophenols from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in non-aqueous solution. The efficiency of this polymer for extraction of phenol and chlorophenols was evaluated using 35 mg of PPy as the sorbent in an on-line SPE system coupled to reversed-phase liquid chromatography with UV detection. The mobile phase were mixture of phosphate buffer–acetonitrile and compounds were eluted by the mobile phase using a six-port switching valve. High volumes of water, up to 160 ml, could be preconcentrated without the loss of phenols, except for the more polar ones. The R.S.D. for a river water sample spiked with phenol and chlorophenols at sub-ppb level was lower than 7% ( n =5) and detection limits of 15–100 and 35–150 ng l −1 for tap and river water were obtained, respectively.

On-line trace enrichment of phenolic compounds from water using a pyrrole-based polymer as the solid-phase extraction sorbent coupled with high-performance liquid chromatography

A pyrrole-based conductive polymer was prepared and applied as new sorbent for on-line solid-phase extraction (SPE) of phenol and chlorophenols from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in non-aqueous solution. The efficiency of this polymer for extraction of phenol and chlorophenols was evaluated using 35 mg of PPy as the sorbent in an on-line SPE system coupled to reversed-phase liquid chromatography with UV detection. The mobile phase were mixture of phosphate buffer–acetonitrile and compounds were eluted by the mobile phase using a six-port switching valve. High volumes of water, up to 160 ml, could be preconcentrated without the loss of phenols, except for the more polar ones. The R.S.D. for a river water sample spiked with phenol and chlorophenols at sub-ppb level was lower than 7% ( n=5) and detection limits of 15–100 and 35–150 ng l −1 for tap and river water were obtained, respectively.

Comparison of different sorbents for on-line solid-phase extraction of pesticides and phenolic compounds from natural water followed by liquid chromatography

Three different sorbents, Carbopack B, a carbon black, Bond Elut PPL, a functionalized polymeric resin, and HYSphere-1, a higher cross-linking polymeric resin, in a steel precolumn of 10×3 mm I.D., were compared for solid-phase extraction (SPE) of a group of pesticides and phenolic compounds in water which was on-line coupled to reversed-phase liquid chromatography and UV detection. HYSphere-1 gave a higher breakthrough volume for phenol, one of the most polar compounds studied and enabled 100 ml of water to be concentrated with no significant losses of the compounds studied (73% for phenol). Recoveries in tap water were between 67% for phenol and 86% for eight polar analytes, and detection limits were between 0.03 and 0.17 μg l −1.