SPE Adsorbent Research Articles

Evaluation of polytetrafluoroethylene as a novel selective adsorbent for solid phase extraction followed by RP-HPLC determination of synthetic pyrethroids from surface waters

The phenomena of selective adsorption of synthetic pyrethroids on polytetrafluoroethylene containers observed while storing contaminated water samples, has been reversibly exploited for quantitative solid phase extraction followed by their determination by RP-HPLC. A specially designed glass column packed with very fine pellets of polytetrafluoroethylene was used as a SPE cartridge and factors affecting adsorption/desorption processes were optimized. High enrichment factors ranging 1882–3318 were obtained with detection limits as low as 0.03–0.06 ng mL−1. When compared with the conventional C18-based SPE, it showed good selectivity against highly and moderately polar organic compounds making it superior to C18 SPE particularly for extraction of synthetic pyrethroids from complex aqueous media. This is the first report on the use of polytetrafluoroethylene as SPE adsorbent for selective extraction and quantitative determination of synthetic pyrethroids from contaminated surface waters.

Preparation of molecularly imprinted polymer for use as SPE adsorbent for the simultaneous determination of five sulphonylurea herbicides by HPLC

A high selective pre-treatment method for the analysis of sulphonylurea herbicides (SUHs) in rice grain samples based on molecularly imprinted solid-phase extraction (MISPE) was developed. The molecularly imprinted polymers (MIPs) were synthesised with high adsorption capacity and suitable particle size using pyrazosulphuron ethyl (PS) as the template and by screening three porogens and porogen volumes. The resulting MIPs showed high selectivity for PS. The MISPE procedure was developed for the purification and enrichment of PS, bensulphuron methyl (BSM), tribenuron methyl (TBM), metsulphuron methyl (MSM) and nicosulphuron (NS) from a rice grain sample prior to reversed-phase high-performance liquid chromatography (HPLC) analysis. Average recoveries of the PS, NS, MSM and BSM were 95.6%, 88.6%, 87.8% and 89.4%, respectively, but the recovery of TBM was lower (48.2%). This pre-treatment methodology for extracting SUHs was simple and cleaner extractions. The limits of detection ranged from 10.1 to 50.0ngL−1. Five local rice grain samples were analysed by HPLC–MISPE, and PS was detected in all five samples, while BSM was detected in one sample.

Rapid separations by LC using ion‐exchange media based on spongy monoliths

Novel sponge-based monoliths containing ionic functional groups were developed for rapid separation and/or concentration of ionic solutes. The cationic and anionic spongy monoliths were prepared by chemical modifications of the pore surface on an original spongy monolith consisting of poly(ethylene-co-vinyl acetate). After hydrolysis of the spongy monolith, an anionic or a cationic moiety was introduced with succinyl chloride or acryloyl chloride/diethylamine, respectively. As a result of liquid chromatographic evaluations for the columns packed with these ionic spongy monoliths, both anionic and cationic monoliths showed ionic interactions with the opposing ionic solutes even if a higher flow rate (9.0 mL/min) was employed. Furthermore, we demonstrated the effective and rapid preconcentration of adenosine 5'-monophosphate in water using column-switching LC combined with the cationic spongy monolith as an online SPE adsorbent.

Preparation and application of surface molecularly imprinted silica gel for selective extraction of melamine from milk samples

Highly selective molecularly imprinted layer-coated silica gel (MIP@SiO2) for melamine (MEL) was prepared by the surface molecular imprinting technique on the supporter of silica gel. Non-imprinted polymer layer-coated silica gel (NIP@SiO2) and bulk molecularly imprinted polymer (MIP) were also prepared for comparison. Characterization and performance tests of the obtained products revealed that MIP@SiO2 not only had excellent selectivity to the target molecule MEL compared with NIP@SiO2, but also displayed absorption capacity superior to MIP due to the molecular recognition sites on the surface of silica gel. As the MIP@SiO2 were adopted as the adsorbents of solid-phase extraction for detecting MEL in milk samples, the recoveries of spiked samples ranged from 75.6% to 96.8% with the relative standard deviation of spiked samples less than 10%, which reveals that the MIP@SiO2 were efficient SPE adsorbents for melamine.

Analysis of acidic, basic and neutral pharmaceuticals in river waters: clean-up by 1°, 2° amino anion exchange and enrichment using an hydrophilic adsorbent

A fast and sensitive LC-MS/MS method suitable to monitor a set of 24 pharmaceuticals belonging to 9 therapeutical families was developed using an analytical column of reduced dimensions and an appropriate SPE procedure for acidic, basic and neutral analytes. Furthermore, a preliminary assessment of the occurrence and levels of these substances in surface waters of the Leça and Douro rivers, located in the north of Portugal, was conducted. Among 17 different SPE adsorbents tested, some of them often neglected, the JTBaker H2Ophilic provided the best recoveries (average 86%). When compared to the amino and quaternary ammonium adsorbents, the 1°, 2° amino proved the most suitable clean-up media for surface water samples prior to enrichment by SPE. The overall method provided limits of detection generally below 5 ng L−1 and a precision below or around 10% RSD in three non-consecutive days at 500 ng L−1 and around 12% at 50 ng L−1 concentration levels. The confirmatory capabilities of the method developed are especially welcome either through the MS3 spectra or the isotopic pattern. The first known results regarding the occurrence of pharmaceuticals in Leça river confirmed its expected high contamination load and the successful selection of the target pharmaceuticals. Concentrations up to 770 ng L−1 of bezafibrate, 925 ng L−1 of paracetamol, 389 ng L−1 of hydrochlorothiazide and 283 ng L−1 of furosemide were measured. The most ubiquitous in both seasons, February and June 2009, were bisoprolol, furosemide, bezafibrate and gemfibrozil. In Douro river the abundance and contamination level of pharmaceuticals was much lower which gives a clear indication that the hydraulic features of the river provide enough attenuation of the several contamination sources whereas Leça is highly impacted by insufficiently treated anthropogenic effluents.

Nanometer‐sized alumina packed microcolumn solid‐phase extraction combined with field‐amplified sample stacking‐capillary electrophoresis for the speciation analysis of inorganic selenium in environmental water samples

In this paper, a new method of nanometer-sized alumina packed microcolumn SPE combined with field-amplified sample stacking (FASS)-CE-UV detection was developed for the speciation analysis of inorganic selenium in environmental water samples. Self-synthesized nanometer-sized alumina was packed in a microcolumn as the SPE adsorbent to retain Se(IV) and Se(VI) simultaneously at pH 6 and the retained inorganic selenium was eluted by concentrated ammonia. The eluent was used for FASS-CE-UV analysis after NH₃ evaporation. The factors affecting the preconcentration of both Se(IV) and Se(VI) by SPE and FASS were studied and the optimal CE separation conditions for Se(IV) and Se(VI) were obtained. Under the optimal conditions, the LODs of 57 ng L⁻¹ (Se(IV)) and 71 ng L⁻¹ (Se(VI)) were obtained, respectively. The developed method was validated by the analysis of a certified reference material of GBW(E)080395 environmental water and the determined value was in a good agreement with the certified value. It was also successfully applied to the speciation analysis of inorganic selenium in environmental water samples, including Yangtze River water, spring water, and tap water.

Determination of Traces of Iron and Lead in Food and Water Samples After Preconcentration on Multiwalled Carbon Nanotubes

A new method using multiwalled carbon nanotubes as an SPE adsorbent was developed for the sensitive determination of trace iron and lead prior to flame atomic absorption spectrometry analysis. Iron and lead as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline chelates were adsorbed quantitatively on multiwalled carbon nanotubes at a pH of 6.0 and easily eluted with 10 mL 1 M HNO3. The influences of matrix ions were also examined. The LOD values for iron and lead were calculated as 1.3 and 2.9 microg/L, respectively. Validation of the presented procedure was performed by the analysis of TMDA 54.4 fortified lake water and HR-1 Humber River sediment certified reference materials. The method was successfully applied to the determination of trace iron and lead in real environmental samples, and excellent results were achieved.

Multiwalled Carbon Nanotubes as SPE Adsorbents for Simultaneous Determination of Seven Sulfonylurea Herbicides in Environmental Water by LC–MS–MS

An 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 2 > 0.99) over the range of 0.05–5,000 ng L−1, and precisions (RSD) for nine replicate measurements of a standard mixture of 200 ng L−1 were 1.9–7.4%. The limits of detection and quantification were 0.01–0.20 and 0.05–1.00 ng L−1, 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.

Determination of trace organophosphorus pesticides in water samples with TiO2 nanotubes cartridge prior to GC‐flame photometric detection

This article described a new method for the sensitive determination of organophosphorus pesticides in water samples using SPE in combination with GC-flame photometric detection. In the procedure of method development, TiO(2) nanotubes were used as SPE adsorbents for the enrichment of organophosphorus pesticides from water samples. Several factors, such as eluent and its volume, sample pH, sample volume, sample flow rate, and concentration of humic acid, were optimized. Under the optimal conditions, the proposed method had good linear ranges as 0.1-40 microg/L for each of them, LOD of 0.11, 0.014, and 0.0025 microg/L, and LOQs of 0.37, 0.047, and 0.0083 microg/L for chlorpyrifos, phorate, and methyl parathion, respectively. The proposed method was validated with real environmental water samples and the spiked recoveries were over the range of 86.5-115.1%. All these results indicated that TiO(2) nanotubes, as a new SPE adsorbent, would be used widespread for the preconcentration and determination of environmental pollutants in the future.

Development of magnetic octadecylsilane particles as solid-phase extraction adsorbent for the determination of fat-soluble vitamins in fruit juice-milk beverage by capillary liquid chromatography

A sensitive, fast and simple method based on magnetic octadecylsilane particles was developed for the extraction of three fat-soluble vitamins followed by capillary LC (CLC) analysis with UV detection. Magnetic octadecylsilane particles were prepared based on three-step reactions including co-precipitation, sol-gel polymerization and alkylation. The characterization of the prepared product was studied by scanning electron microscope and Fourier-transform infrared spectrometry. The particles were used as magnetic SPE adsorbent for the extraction of fat-soluble vitamins in fruit juice-milk beverage. The extraction condition and efficiency of the particles for fat-soluble vitamins were investigated. By coupling magnetic SPE with capillary LC with UV detection, low concentrations of fat-soluble vitamins in fruit juice-milk beverage can be detected without the interference from other substances in the sample matrix.

Highly sensitive determination of tetrabromobisphenol A and bisphenol A in environmental water samples by solid‐phase extraction and liquid chromatography‐tandem mass spectrometry

Using bamboo-activated charcoal as SPE adsorbent, a novel SPE method was developed for the sensitive determination of tetrabromobisphenol A and bisphenol A in environmental water samples by rapid-resolution LC-ESI-MS/MS. Important parameters influencing extraction efficiency, including type of eluent, eluent volume, sample pH, volume and flow rate, were investigated and optimized. Under the optimal extraction conditions (eluent: 8 mL methanol, pH: 7; flow rate: 4 mL/min; sample volume: 100 mL), low LODs (0.01-0.02 ng/mL), good repeatability (6.2-8.3%) and wide linearity range (0.10-10 ng/mL) were obtained. Satisfied results were achieved when the proposed method was applied to determine the two target compounds in real-world environmental water samples with spiked recoveries over the range of 80.5-119.8%. All these facts indicate that trace determination of tetrabromobisphenol A and bisphenol A in real-world environmental water samples can be realized by bamboo-activated charcoal SPE-rapid resolution-LC-ESI-MS/MS.

Electrospun Nylon6 Nanofibrous Membrane as SPE Adsorbent for the Enrichment and Determination of Three Estrogens in Environmental Water Samples

In this paper, electrospun Nylon6 nanofibrous membrane was firstly used as adsorbent for solid membrane extraction (SME). The membrane was arranged as a disk in a home-made device, three estrogens-estradiol (E2), ethinylestradiol (EE2) and estrone (E1) in environmental water were extracted and then determined by liquid chromatography–ultraviolet detector (LC–UV). The important parameters affecting extraction efficiency were completely studied and optimized. The experimental results showed that only 1.5 mg Nylon6 nanofibrous membrane could make the maximum sample loading volume up to 50 mL and the target analytes were adsorbed effectively. Under the optimized conditions, the limits of detection (LOD) for E2, EE2, E1 were up to 0.05, 0.08, 0.17 ng mL−1 respectively and the repeatabilities (RSD%) of intra-membrane and inter-membrane were below 6.0% about spiked samples. The proposed method was subsequently applied to studying water samples from river, rain, pond and tap. Satisfactory spiked recoveries in the range of 85.3–95.9% at 0.25 ng mL−1 spiked level for the three estrogens were obtained. A comparison with commercial nylon microporous membrane and octadecylsilica (ODS) cartridges was also carried out. All the results showed that electrospun Nylon6 nanofibrous membrane, as a new adsorbent material has great potential for the enrichment of steroid estrogens in the water samples with satisfactory recovery and repeatability.

Evaluation of sulfobetaine‐type polymer resin as an SPE adsorbent in the analysis of trace tetracycline antibiotics in honey

A new sulfobetaine polymer resin SPE method combined with HPLC-MS/MS for the determination of tetracycline (TC) antibiotics residues from honey samples is presented. The sulfobetaine resin was synthesized and was packed into a syringe-type tube, which served as the SPE cartridge for selective adsorption of TCs. TCs were quantitatively adsorbed on the sulfobetaine cartridge, when the loading solvent was 95% v/v acetonitrile solution, and TCs adsorbed were not eluted by aqueous acetonitrile washing solution. TFA aqueous solution was used for eluting the adsorbed TCs. The proposed SPE method has been applied to the determination of TCs in honey samples. The recoveries of TCs spiked in honey samples ranged from 70 to 80%. Reduction of the recoveries might be derived from low solubility of TCs in acetonitrile. Compared with other SPE resins, this resin was superior in terms of selectivity with simple pretreatment.

Sensitive determination of phenols in environmental water samples with SPE packed with bamboo carbon prior to HPLC

Bamboo carbon, an inexpensive, readily available material, has attracted great attention in recent years because of adsorptive properties. In this paper, the potential of bamboo carbon as a SPE adsorbent for the determination of phenols, was investigated. Phenols are important environmental contaminants that may adversely affect human health. Parameters influencing extraction efficiency, including type of eluent, eluent volume, amount of adsorbent, as well as sample pH, volume, and flow rate were investigated and optimized. The optimized results exhibited excellent linear relationships between peak area and phenol concentrations over the range of 2.0-100 ng/mL, with precision between 2.2-7.2%. The LODs were 0.06-0.4 ng/mL for the eight phenols tested. The proposed method has been successfully applied to the analysis of several real-world environmental water samples. These results indicate that bamboo carbon may be used as a novel SPE adsorbent for the concentration and determination of phenols in real environmental water samples.

Use of Multiwalled Carbon Nanotubes as a SPE Adsorbent for Analysis of Carfentrazone-Ethyl in Water

Solid-phase extraction and gas chromatography with electron-capture detection has been used for sensitive, simple, and reliable analysis of carfentrazone-ethyl residues in water. Carfentrazone-ethyl was enriched by use of multiwalled carbon nanotubes (MWCNT), a new adsorptive material. Several conditions affecting recovery of the analyte, for example polarity and volume of eluents, pH of water samples, and sample volume, were studied. Recovery from fortified samples, linear range, and limit of detection were evaluated. The results showed that MWCNT are an efficient SPE adsorbent for preconcentration of carfentrazone-ethyl in water. Under the optimized SPE conditions, recovery of carfentrazone-ethyl from fortified water was 81.49–91.08%, with RSD from 1.66 to 8.21%. The limits of detection and quantification were 0.01 and 0.03 µg L−1, which were lower than the MRL stipulated by the EU for individual pesticides in water (0.1 µg L−1). Finally, the method was applied to tap water and river water; the results showed that the method was suitable for detection of carfentrazone-ethyl in environmental water samples.

Improvement on Analyte Extraction by Molecularly Imprinted Polymer Microspheres toward Enrofloxacin

A collection of molecularly imprinted polymer microspheres (MIPMs) for Enrofloxacin (ENRO) were for the first time obtained through suspension polymerization in this work. The appropriate MIPMs used as specific SPE adsorbents were selected based on evaluation of binding capacities and morphology characterization. Combined with one simpler MISPE procedure for cleanup and preconcentration of ENRO in milk, further HPLC-UV analysis showed improved sensitivity of 10 µg kg−1 than those reported in previous studies, with the desirable recoveries of 73.6–101.6%, proving that the developed MIPMs are applicable for extraction of ENRO during the process of sample preparation.

A novel Pb(II)-imprinted IPN for selective preconcentration of lead from water and sediments

A novel adsorbent Pb(II)-imprinted interpenetrating polymer network (IPN) of epoxy resin-triethylenetetramine and lead methacrylate-acrylamide-1,4-butanedioldiacrylate (BDDA) was synthesized by the metal ionic imprinted polymer (MIIP) technique. The IPN was prepared by in situ sequential polymerization, and the coordination interaction of Pb(II) and functional groups of the IPN adsorbent was discussed using FT-IR spectra. The characters of the IPN were investigated by a series of experiments. The experimental results show that trace Pb(II) ions can be quantitatively preconcentrated at pH 4.0 with recoveries >95%. The maximum static adsorption capacity of the ion-imprinted adsorbent was 138.6 mg g−1. The imprinted IPN has a higher adsorption capacity and selectivity towards Pb(II). Moreover, the Pb(II)-imprinted IPN shows superior reusability and stability. The precision (R.S.D.) for 11 replicate adsorbent extractions of 20 ng mL−1 Pb(II) was 2.9%. The accuracy of the proposed procedure was verified by analysing three standard reference materials. The prepared ion-imprinted IPN adsorbent was applied to three natural samples and also yielded satisfactory results. That is to say, the Pb(II)-imprinted IPN is suitable for environmental Pb(II) ionic selective removal as an SPE adsorbent.

Comparison of the Enrichment Efficiency of Multiwalled Carbon Nanotubes, C18 Silica, and Activated Carbon as the Adsorbents for the Solid Phase Extraction of Atrazine and Simazine in Water Samples

Multiwalled carbon nanotubes with exceptional merits as SPE adsorbents for enrichment of environmental pollutants have absorbed much attention. The goal of this paper was to make a comparison with it and regular adsorbents such as C18 silica and activated carbon in the extraction capacity of atrazine and simazine. The results indicated that multiwalled carbon nanotubes were very suitable for determination of atrazine and simazine because of an enrichment performance similar to that of C18 silica. In contrast, the spiked recovery of simazine was higher than that of atrazine using multiwalled carbon nanotubes as packing material for SPE. However, reverse results were obtained when the extraction was performed with packing of C18 silica. Moreover, as the extraction of simazine was concerned, multiwalled carbon nanotubes were much better than C18 silica. As for the enrichment of atrazine, C18 silica achieved greater extraction factor than multiwalled carbon nanotubes. Activated carbon did not give the expected extraction efficiency because of its large size and blank volume and less active sites for adsorption. All these experimental results indicated that multiwalled carbon nanotubes could be used as a valuable alternative adsorbent for SPE of atrazine and simazine in many real water samples.

Sensitivity enhancement for nitrophenols using cationic surfactant-modified activated carbon for solid-phase extraction surface-assisted laser desorption/ionization mass spectrometry.

Previous work has demonstrated that a combination of solid-phase extraction with surface-assisted laser desorption/ionization (SPE-SALDI) mass spectrometry can be applied to the determination of trace nitrophenols in water. An improved method to lower the detection limit of this hyphenated technique is described in this present study. Activated carbon powder is used as both the SPE adsorbent and the SALDI solid in the analysis by SPE-SALDI. The surface of the activated carbon is modified by passing an aqueous solution of a cationic surfactant through the SPE cartridge. The results demonstrate that the sensitivity for nitrophenols in the analysis by SPE-SALDI can be improved by using cationic surfactants to modify the surface of the activated carbon. The detection limit for nitrophenols is about 25 ppt based on a signal-to-noise ratio of 3 by sampling from 100 mL of solution.

Screening of antifouling pesticides in sea water samples at low ppt levels by GC-MS and LC-MS

Studies of various analytical procedures for simultaneous determination of antifouling pesticides in sea water, based on SPE followed by GC-MS and LC-MS, have been made. The main characteristics of these compounds in GC-MS in both positive and negative modes and in LC-ES-MS were studied. Extraction of the compounds from filtered water was performed off-line with different SPE adsorbents using graphitized carbon (Envi-carb) and polymer cartridges (Isolute ENV+ and Oasis HLB) by passing 600 mL samples through them. Detection was carried out following selected analytical procedures (GC-MS in El and NCI modes) and LC-ES-MS (positive mode). Recoveries ranged from 80–95% except for dichlofluanid and Sea-nine 211 where they were 40 and 46%. In spite of this, the low coefficients of variation (<11%) obtained, were low enough to consider these recoveries adequately. Limits of detection were at low part-per-trillon levels in all cases. Finally, a six-month pilot study was carried out at various marinas in the South-East of Spain. Irgarol 1051 and diuron were revealed as the major antifouling agents in this area at concentrations up to 0.9 and 0.8 µg L−1 respectively.