Use In Solid-phase Extraction Research Articles

Use of response surface methodology to optimize triclosan adsorption on alumina pillared clays in a fixed-bed column for applications in solid-phase extraction

Fixed-bed column studies are generally conducted to consider possible applications in water-purification processes. In this work, three synthetic alumina pillared interlayered clays (Al-PILC) were analyzed in fixed-bed column studies for use as sorbents for solid-phase extraction (SPE) for the first time. Adsorption processes were studied for triclosan (TCS), which is an emerging pollutant (EP) that has been shown to have several health effects. Breakthrough curves were investigated by varying process parameters such as bed height (0.25–0.75 cm), inlet TCS concentration (20–60 mg/cm3), and flow rate (0.5–3 cm3/min). Bohart-Adams, Bed Depth Service Time (BDST), and Thomas models were satisfactory applied to the results obtained for fixed-bed columns. The adsorption of TCS was successfully optimized for use in SPE for the three adsorbents studied using response surface methodology with a Box–Behnken design (RSM-BBD). The models developed were adequate for the experimental data (95% significance level), with high regression parameters (98.9–99.1). The optimum values for TCS adsorption on the fixed-bed column were 378.04, 367.78, and 378.93 mg (amount of adsorbent packed into the column), 0.5 cm3/min (flow rate), 4.24, 3.96, and 3.85 (pH), and 2.56, 1.93, and 1.13 mg/dm3 (inlet TCS concentration) for Al-PILCAE, Al-PILCBE, and Al-PILCCM, respectively. From these results synthetic Al-PILC are effective and promising sorbents that can be used for analytical purposes in SPE, and that RSM-BDD is an effective and reliable tool for evaluating and optimizing the adsorption conditions for emerging contaminants in a fixed-bed column system.

Utilization of UiO-66-NH2@cellulose hybrid aerogel for solid-phase extraction of sildenafil in health products

研究建立了一种基于UiO-66-NH2@纤维素复合气凝胶的高灵敏度固相萃取新方法,与高效液相色谱法联用用于保健品中西地那非的检测。先将纤维素进行醛基和酰肼基的功能化,然后将两种功能化的纤维素通过交联并负载UiO-66-NH2形成复合气凝胶。将此复合气凝胶作为固相萃取的吸附剂使用时,易于收集且不需要外加磁场或者抽真空的辅助作用,操作简单。研究对制备所得的UiO-66-NH2@纤维素复合气凝胶进行了X-射线粉末衍射、扫描电镜、红外光谱和N2吸附等表征,结果显示UiO-66-NH2成功负载于气凝胶的孔道中,纤维素气凝胶掺杂了UiO-66-NH2之后其孔道结构变得规整,并且比表面积增大。研究优化了复合气凝胶中UiO-66-NH2的负载量对萃取的影响,高比例的负载量有利于西地那非的富集,并且最高的负载率为50%。研究优化了影响西地那非富集效率的实验条件,包括溶液pH、萃取时间、洗脱剂类型、洗脱时间、洗脱体积和离子强度。采用安捷伦Zorbax Eclipse Plus C18色谱柱(150 mm×4.6 mm, 5 μm)进行分离,以含0.1 mol/L三乙胺的磷酸盐水溶液(pH=6.50)-乙腈(30∶70, v/v)为流动相进行洗脱,检测波长为292 nm。在最佳的萃取条件下(pH为9.0,萃取时间为60 min,洗脱剂为乙腈,洗脱液体积为3×2 mL,洗脱时间为40 min),该分析方法的线性范围为10~2000 ng/mL (相关系数R2=0.9949),检出限(LOD, S/N=3)为2.85 ng/mL,富集因子为59.17。将该方法用于保健品中西地那非的萃取,所得回收率为74.93%~89.12%,相对标准偏差为2.8%~5.3%,表明了方法的回收率和精密度良好,说明了该方法具有应用于保健品中西地那非日常检测的潜力。

Oilothermal, a novel pyrolysis method for fabrication of carbon dots-loaded carriers from cyanobacteria for use in solid-phase extraction of cadmium

BackgroundMaking carbon dots-loaded carriers (CLCs) required the use of two types of precursors (one for carrier particles and the other for carbon dots) and at least three steps. In this study, CLCs were fabricated by using cyanobacterial cells as a dual-purpose precursor and oilothermal as an innovative pyrolysis method. MethodsThe oilothermal method allowed that each cyanobacterial cell (carrier particle precursor) with its hydrous exopolysaccharides (EPSs) layer (carbon dots precursor) to be encapsulated together by an oil micelle and pyrolyzed separate from other cells and formed the CLC in one step. The potential of emerging CLCs for solid-phase extraction (SPE) was assessed. For this purpose, the CLCs were tested in a cadmium-based model. Significant findingsThe range of the maximum pH-dependent adsorption efficiency (>95%) was extensive (pH 4–10). The adsorption kinetics and isotherm had the best fit with the pseudo-second-order and Langmuir linear models, respectively. The adsorption capacity was 5305.61 mg kg−1 only in 2 min exposure time. The findings in this research conclude that emerging CLCs, because of their unique features such as high capacity, fast adsorption rate, fast recovery rate, green origin, optimal and efficient fabrication method, have a high potential for SPE of trace cadmium.

NanoMIP-Based Solid Phase Extraction of Fluoroquinolones from Human Urine: A Proof-of-Concept Study

NanoMIPs that are prepared by solid phase synthesis have proven to be very versatile, but to date only limited attention has been paid to their use in solid phase extraction. Thus, since nanoMIPs show close similarities, in terms of binding behavior, to antibodies, it seems relevant to verify if it is possible to use them as mimics of the natural antibodies that are used in immunoextraction methods. As a proof-of-concept, we considered prepared nanoMIPs against fluoroquinolone ciprofloxacin. Several nanoMIPs were prepared in water with polymerization mixtures of different compositions. The polymer with the highest affinity towards ciprofloxacin was then grafted onto a solid support and used to set up a solid phase extraction–HPLC method with fluorescence detection, for the determination of fluoroquinolones in human urine. The method resulted in successful selection for the fluoroquinolone antibiotics, such that the nanoMIPs were suitable for direct extraction of the antibiotics from the urine samples at the µg mL−1 level. They required no preliminary treatment, except for a 1 + 9 (v/v) dilution with a buffer of pH 4.5 and they had good analyte recovery rates; up to 85% with precision in the range of 3 to 4.5%, without interference from the matrix. These experimental results demonstrate, for the first time, the feasibility of the use of nanoMIPs to develop solid phase extraction methods.

Solid-Phase Extraction of Active Compounds from Natural Products by Molecularly Imprinted Polymers: Synthesis and Extraction Parameters.

Molecularly imprinted polymers (MIPs) are synthetic polymers with a predetermined selectivity for a particular analyte or group of structurally related compounds, making them ideal materials for separation processes. Hence, in sample preparation, MIPs are chosen as an excellent material to provide selectivity. Moreover, its use in solid-phase extraction, also referred to as molecular imprinted solid phase extraction (MISPE), is well regarded. In recent years, many papers have been published addressing the utilization of MIPs or MISPE as sorbents in natural product applications, such as synthesis. This review describes the synthesis and characterization of MIPs as a tool in natural product applications.

Bisphenol A adsorption in aqueous medium by investigating organic and inorganic components of hybrid polymer (polyvinylpyridine/SiO2/APTMS)

The synthesis, characterization, and evaluation of new hybrid polymers towards bisphenol A (BPA) adsorption in aqueous medium were described. Different parameters related to the synthesis, such as catalyst nature, solvent type and the influence of 4-vynilpyridine (4-VP), 3-aminopropyltrimethoxysilane (APTMS) and tetraorthosilicate (TEOS) were investigated. The synthesized materials were named as polyvinylpyridine/SiO2/APTMS, polyvinylpyridine/SiO2, and polyvinylpyridine and characterized by FT-IR, SEM, TGA, elemental analysis and nitrogen adsorption/desorption measurements, as well as by kinetics and isotherms assays. From textural data results and binding adsorption assays, it was observed that the presence of APTMS in the hybrid polymer (polyvinylpyridine/SiO2/APTMS) gives rise to a adsorbent with lower adsorption capacity towards BPA and lower porosity. On the other hand, the presence of TEOS in the hybrid polymer (polyvinylpyridine/SiO2) provided a substantial improvement on the surface area and satisfactory adsorption capacity towards BPA compared with polyvinylpyridine/SiO2/APTMS. The organic polymer polyvinylpyridine, in turn, presented a slight superior adsorption capacity towards BPA (295 mg g−1) and lower surface area (75.1 m2 g−1) compared with polyvinylpyridine/SiO2 (232 mg g−1 and 132.5 m2 g−1), but drawbacks of overpressure when packed into extraction columns, which limits its use in solid phase extraction (SPE) procedures. Therefore, polyvinylpyridine/SiO2 has demonstrated the best performance towards BPA adsorption in aqueous medium, thereby showing the symbiosis of organic and inorganic components for obtaining materials with complementary properties.

A magnetic knitting aromatic polymer as a new sorbent for use in solid-phase extraction of organics.

Magnetic knitting aromatic polymers (Fe3O4/KAPs) are introduced here as a new kind of sorbents. KAPs are hyper-cross-linked-polymers that were prepared via a Friedl-Crafts reaction from triphenylphosphine and benzene as building blocks. The Fe3O4/KAP composite was obtained by coprecipitation of KAP with magnetite nanoparticles. The resulting Fe3O4/KAP is shown to be a viable magnetic sorbent for various organic materials such as the phenylurea herbicides (PUHs), including metoxuron, monuron, chlortoluron, monolinuron and buturon, and also for various phthalates, polycyclic aromatic hydrocarbons and chlorophenols. The Fe3O4/KAP was characterized by means of Brunauer-Emmett-Teller surface area measurements, Fourier-transform infrared spectroscopy, thermogravimetry, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Following desorption with acetonitrile, the analytes were quantified by using HPLC with UV detection. The effects of adsorbent dosage, extraction time, sample pH, ionic strength, desorption solvent and desorption time were optimized for the PUHs. Under optimal conditions, response is linear from 0.5-1.0 up to 50ng·mL-1 for the five PUHs. Lower limits of detection range between 0.05 and 0.30ng·mL-1. Other figures of merit include (a) high enrichment factors (60-297), (b) good recoveries (91.8-106.5%), and (c) relative standard deviations of <8.4%. The method was successfully applied to analysis of the PUHs in real samples (bottled mixed juice, milk and soymilk). The results indicate that such Fe3O4/KAPs have a wide application scope as an adsorbent for use in magnetic solid phase extraction. Graphical abstract A magnetic knitting aromatic polymer based nanocomposite (Fe3O4/KAP) was prepared by a one-pot method and explored as an absorbent for magnetic solid-phase extraction (MSPE) of phenylurea herbicides (PUHs) from bottled mixed juice, milk and soymilk samples before quantitation byHPLCwithUV detection.

Development of immunosorbents for the analysis of forchlorfenuron in fruit juices by ion mobility spectrometry

The advantages of using smart materials as immunosorbents in the analysis of complex matrices by ion mobility spectrometry (IMS) have been highlighted in this study. A novel analytical method has been proposed for the sensitive, selective, and fast determination of residues of the plant growth regulator forchlorfenuron in fruit juices. Three different monoclonal antibodies (s3#22, p2#21, and p6#41) were employed for the production of immunosorbents, based on Sepharose gel beads, which were characterized in terms of loading capacity, solvent resistance, and repeatability for its use in solid-phase extraction (SPE). Immunosorbents that were prepared with antibody p6#44 provided the best performance, with a loading capacity of 0.97μg, a 10% (v/v) 2-propanol tolerance, and a reusability of at least eight uses. The SPE procedure involved the use of a column with 0.15g Sepharose beads, containing 0.5mg antibody, which was loaded to 20mL of the sample, washed with 2mL of water plus 2mL of 10% (v/v) 2-propanol, and eluted with 2mL of 2-propanol. The cleaned extract was directly analyzed by IMS, giving a limit of detection of 2μgL-1 with a relative standard deviation of 7.6%. Trueness was assessed by the analysis of blank grape and kiwifruit juice samples spiked with forchlorfenuron concentrations from 10 to 400μgL-1, with recoveries from 80 to 115%. The analytical performance of the proposed immunosorbent was compared with conventional extraction and cleanup methods, such as QuEChERS and C18-based SPE, giving the cleanest extracts for accurate determinations of forchlorfenuron by IMS. Graphical abstract ᅟ.

Magnetic nanoparticle based solid-phase extraction of heavy metal ions: A review on recent advances.

This review (with 151 refs) focuses on recent progress that has been made in magnetic nanoparticle-based solid phase extraction (SPE), pre-concentration and speciation of heavy metal ions. In addition, it discusses applications to complex real samples such as environmental, food, and biological matrices. The introduction addresses current obstacles and limitations associated with established SPE approaches and discusses the present state of the art in different formats of off-line and on-line SPE. The next section covers magnetized inorganic nanomaterials for use in SPE, with subsections on magnetic silica, magnetic alumina and titania, and on magnetic layered double oxides. A further section treats magnetized carbonaceous nanomaterials for use in SPE, with subsections on magnetic graphene and/or graphene oxides, magnetic carbon nanotubes and magnetic carbon nitrides. We then discuss the progress made in SPE based on the use of magnetized organic polymers (mainly non-imprinted and ion-imprinted polymer). This is followed by shorter sections on the use of magnetized metal organic frameworks, magnetized ionic liquids and magnetized biosorbents. All sections include discussions of the nanomaterials in terms of selectivity, sorption capacity, mechanisms of sorption and common routes for material synthesis. A concluding section addresses actual challenges and discusses perspective routes towards further improvements. Graphical abstract An overview on booster nanomaterials (ionic liquids, inorganic, organic and biological materials, and metal-organic frameworks) for use in magnetic nanoparticle-based solid-phase extraction of heavy metal ions.

Testing of nylon 6 nanofibers with different surface densities as sorbents for solid phase extraction and their selectivity comparison with commercial sorbent

Nylon 6 nanofibers were tested for their ability to serve as a sorbent for solid phase extraction (SPE). The regular nanostructure providing a great sorption area and amidic functionality should lead to the assumption that nylon 6 nanofibers could be used as a novel sorbent with great potential for sample pre-treatment. However, due to the substantial differences between classical particle sorbents used for solid phase extraction and nanofibers, it is necessary to evaluate this novel approach. This article describes three types of laboratory fabricated nylon 6 nanofibers with different surface density (5.04gm−2, 3.90gm−2 and 0.75gm−2) and corresponding surface areas for solid phase extraction of several groups of compounds with different structural and physicochemical properties (parabens, steroids, flavonoids and pesticides). The nanofibers were created by needleless electrospinning. Extraction columns were manually packed in classic 1- or 3-mL plastic syringe cartridges with 26–30mg of nanofibers and the column bed was sealed with polypropylene frits. The SPE procedure followed a typical five-step protocol and the collected eluates were analyzed by HPLC with UV detection. Extraction recovery was used as a parameter to evaluate the behavior of the analytes within the SPE process. Under this set condition, the recovery of the SPE process ranged from 23.1% to 125.8%. SPE showed good repeatability (0.58–11.87% RSD) and inter-day reproducibility (3.86–9.79% RSD). The achieved results were compared with SPE using a classic particle sorbent column. Good mechanical and chemical stability of nanofibers was proved. Scanning electron microscope was used for the evaluation of morphological changes in nanostructure. Nylon 6 nanofibers proved being a cost-effective sorbent for repeated use in SPE. Nylon 6 nanofibers have great potential in miniaturized SPE enabling users to overcome troubles with high back-pressure.

Preparation of ionic liquid-modified SiO2@Fe3O4nanocomposite as a magnetic sorbent for use in solid-phase extraction of zinc(ii) ions from milk and water samples

A sorbent based on silica-coated magnetite nanoparticles modified with triethoxysilylpropylpyridinium hexafluorophosphate ionic liquid was synthesized and used for preconcentration of zinc(ii) ions.

Potential of ion imprinted polymers synthesized by trapping approach for selective solid phase extraction of lanthanides

Ion imprinted polymers (IIPs) specific to lanthanides were synthesized using neodymium ions (Nd3+) as template ions. Nd3+ ions form binary complex ions with 5,7-dichloroquinoline-8-ol (DCQ) or vinylpyridine (VP), or ternary complex ions with both DCQ and VP in 2-methoxyethanol, before copolymerization in the presence of styrene and divinylbenzene as monomer and cross-linker, respectively. DCQ was expected to be trapped in the synthesized polymers pores. The template ion removal was then optimized. For the first time, the DCQ leakage was determined by HPLC-UV during the template removal and the sedimentation steps before solid-phase extraction (SPE) packing. It was observed that the trapped DCQ was unfortunately lost in significant amounts, up to 51%, and that this amount varied from one synthesis to another. The grinded and sieved polymers were next packed in SPE cartridges. The study of the SPE profiles obtained with the IIPs synthesized either with the binary or the ternary complex confirmed the prominent role of DCQ on the selectivity of an IIP by comparison with a non-imprinted polymer (NIP), i.e. a polymer synthesized under the same conditions as those of the IIP but without template ions. The influence of the porogenic solvent on the selectivity was also investigated by replacing 2-methoxyethanol by acetonitrile or dimethylsulfoxyde (DMSO). The polymers synthesized in DMSO led to the most repeatable results when elution solutions with a gradual decrease in pH were percolated through the cartridge. This is why DMSO was used to optimize the SPE protocol in order to maximize the difference of extraction yield between the IIP and the NIP, i.e. promoting a selective retention on the IIP. A value of about 30% was obtained for La3+, Ce3+, Nd3+, and Sm3+. Nevertheless, with the optimized SPE protocol, IIPs from different syntheses did not have the same SPE behavior, which may result from different random leakages of DCQ. This demonstrates for the first time the main limitation of the IIPs synthesized in bulk with the trapping approach for their use in SPE.

Application of sol–gel hybrid extraction sorbent for gas chromatographic analysis of organophosphorus pesticides

Sol–gel hybrid extraction sorbent based on methyltrimethoxysilane-cyanopropyltriethoxysilane (MTMOS-CNPrTEOS) was successfully synthesized by sol–gel process for use in solid-phase extraction (SPE) of organophosphorus pesticides (OPPs). Analysis was performed using gas chromatography–mass spectrometry. Several important sol–gel parameters were optimized. Fourier transform infrared spectroscopy, scanning electron microscopy and surface area analyses were used to characterize the composite structure and morphology in detail. The results showed that the specific area of sol–gel hybrid MTMOS-CNPrTEOS was 585 m2g−1 with perfect spherical shape with average size of 174 nm. Under the optimum sol–gel conditions (2:1 mol composition of MTMOS:CNPrTEOS, NH4OH of pH 10.5 and drying temperature of 100 °C), the method using MTMOS-CNPrTEOS SPE showed good linearity with excellent limit of detection (10–70 pg mL−1) at signal to noise ratio = 3 and good relative standard deviation (RSD < 9 %) for all the three OPPs analyzed.

Preparation of silica-supported carbon by Kraft lignin pyrolysis, and its use in solid-phase extraction of fluoroquinolones from environmental waters

The article describes a carbon-based material for solid-phase extraction (SPE) of fluoroquinolones from waters. It was obtained by pyrolytic deposition of Kraft lignin (LG) on silica particles. Marbofloxacin (MAR) and enrofloxacin (ENR) were chosen as model contaminants. The material was prepared by first adsorbing LG onto silica microparticles, this followed by pyrolytic treatment at 1200 °C for 2 h. Silica-supported carbon was characterized by scanning electron microscopy, surface area measurement (by BET), thermogravimetric analysis, and electron paramagnetic resonance. The carbon-coated silica particles were then tested as a column packing for SPE of MAR and ENR from spiked tap and river waters. Quantitative adsorption was observed at pH values of ~7.5 for both drugs. They were eluted with a 70:30 mixture of aqueous tetrabutylammonium hydroxide and acetonitrile and then quantified by HPLC coupled to fluorescence detection. Samples spiked with MAR and ENR in the range from 10 to 1000 ng·L−1 gave recoveries ranging from 70 to 116% (for n = 3). Good inter-day precision (with RSDs between 7 and 16%) was observed for 20–1000 ng·L−1 spikes, also in natural river water. Sample volumes up to 500 mL provided enrichment factors up to 125, and this makes this material useful for determination of the two drugs at environmentally significant levels which are as low as a few ng·L−1. The batch-to-batch reproducibility was verified for 3 preparations. The sorbent was successfully applied to the determination of these drugs in environmental waters.

Click chemistry-based synthesis of water-dispersible hydrophobic magnetic nanoparticles for use in solid phase extraction of non-steroidal anti-inflammatory drugs

Magnetic nanoparticles (MNPs), prepared via thiol-ene click chemistry and containing both diol and octadecyl groups, are shown to possess both hydrophobic and hydrophilic functionalities. They display excellent dispersibility in water and also are capable of extracting non-steroidal anti-inflammatory drugs (NSAIDs) from water samples. The MNPs can be magnetically separated, and the NSAIDs eluted with acetonitrile-water (9:1, v:v) and submitted to high performance liquid chromatographic analysis. Extraction variables, such as the kind of ion-pairing reagents, amount of MNPs, pH of sample solution, extraction and desorption time, volume of desorption solvent and salt addition, were optimized. Under optimum conditions, the method has a wide analytical range (from 5 to 800 ng∙mL‾1), good reproducibility with intra-day and inter-day relative standard deviations of <19.2 % (for n = 6), and low detection limits of 0.32 to 1.44 ng∙mL‾1 for water samples. The results demonstrate that the material possesses good water compatibility, thus warranting ease of operation and good reproducibility.

Magnetic silica nanomaterials for solid-phase extraction combined with dispersive liquid-liquid microextraction of ultra-trace quantities of plasticizers

We are presenting surface modified magnetic silica nanoparticles (m-Si-NPs) for use in solid-phase extraction combined with dispersive liquid-liquid microextraction (DLLME). The m-Si-NPs were surface-functionalized with octadecyl groups to give a material for the extraction of the plasticizers dibutyl phthalate, di(2-ethylhexyl) adipate and di(2-ethylhexyl) phthalate from water samples. The functionalized m-Si-NPs were characterized by scanning electron microscopy, FTIR spectroscopy, thermal gravimetric analysis, and vibrating sample magnetometry. The results showed that the m-Si-NPs were well functionalized with octadecyl groups. The effects of various experimental variables on the extraction efficiencies were investigated. The analytes were quantified by GC/FID. Under optimal conditions, the calibration plots are linear in the range from 0.01 to 100 μg∙L‾1, and very high enrichment factors (mean value ~20,000) were obtained. As a result of the high enrichment factors, the detection limits are as low as 2–3 ng∙L‾1. The method was successfully employed to the extraction of the plasticizers from (spiked) water samples, and recoveries are in the order of 93.9 to 106.7 %. The method is low cost, fast, and very sensitive.

Silica-coated Mn3O4 nanoparticles coated with an ionic liquid for use in solid phase extraction of silver(I) ions prior to their determination by AAS

We demonstrate the applicability of ionic liquid-modified silica-coated Mn3O4 nanoparticles (NPs) as a sorbent for solid-phase extraction and preconcentration of Ag(I) ion without a chelating agent. The size, morphology and surface coating of the nano-sorbent were characterized via X-ray diffraction analysis, scanning electron microscopy and Fourier transform IR spectroscopy. Following desorption with HCl, silver was quantified by AAS. Under optimized experimental conditions, the calibration graph is linear in the 0.8 − 320 ng mL−1 concentration range (with an r2 of 0.9970). The limit of detection and limit of quantification are 0.2 and 0.8 ng mL−1, respectively. The relative standard deviation (for n = 6; at an Ag(I) concentration of 60 ng mL−1) and preconcentration factor are 1.9 % and 50, respectively. The method was used to determine Ag(I) in (spiked) water samples and in radiology films. The accuracy of the method was confirmed by successfully analyzing the certified reference material NIST SRM 1566b.

Magnetic nanoparticles coated with dithizone-modified chitosan for use in solid-phase extraction of copper(ii)

Novel magnetic nanoparticles coated with dithizone-modified chitosan were prepared. The magnetic adsorbent for magnetic solid-phase extraction was successfully applied to detection of trace copper(ii) ion by graphite furnace atomic absorption spectrometry.

Preparation and evaluation of hydrophilic C18 monolithic sorbents for enhanced polar compound retention in liquid chromatography and solid phase extraction

Hydrophilic C18 monolithic polymer sorbents were synthesized for use in solid phase extraction (SPE) and in capillary liquid chromatography (LC). The approach involved incorporating both hydrophobic and hydrophilic monomers into a monolithic material, by copolymerization of stearyl methacrylate (SMA), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) and ethylene dimethacrylate (EDMA) in the presence of selected porogens, to produce translucent mesoporous monolithic materials in bulk (SPE) or white macroporous monoliths inside fused silica capillary columns (capillary LC). A capillary column containing one of the hydrophilic C18 monoliths (i.e. poly(SMA-co-PEGMEMA-co-EDMA) with 15% (w/w) PEGMEMA) demonstrated nearly 35% reduction in retention of polycyclic aromatic compounds and greater than 40% increase in retention of phenols compared to a hydrophobic C18 monolithic column. In addition, the hydrophilic monolith demonstrated significantly improved resolution of phenols. Similar monolithic materials prepared in bulk were ground and sieved to obtain 45-65 μm particles with desired rigidity for SPE. To achieve optimum extraction performance for phenols, several parameters, including sample pH and volume, and eluent type and volume, were investigated. Under optimized experimental conditions, the method demonstrated good sensitivity (1.6 ng/mL LOD) and linearity (R(2)>0.97 for 10-200 ng/mL). Again, incorporation of 15% (w/w) PEGMEMA in the monolith increased the extraction efficiency of phenols in water from approximately 20% to 67-92% compared to a hydrophobic C18 monolithic material. Increased wettability of the sorbent by the aqueous sample matrix and the presence of hydrogen-bonding interactions are responsible for the improved retention of polar compounds.

Porous metal membranes for solid-phase extraction of polycyclic aromatic hydrocarbons

Solid-phase extraction (SPE) is one of the most important techniques for sample preparation, purification, concentration and cleanup. Membranes made from synthetic organic polymers, cellulose, or glass fibers are used for sample pretreatment. In this work, we report that a porous metal membrane, the metal filter in HPLC, was used as a novel kind of solid-phase extraction adsorbent material. To evaluate the performance of the porous metal membrane for the SPE, naphthalene, fluorene, anthracene, phenanthrene, fluoranthene, pyrene, chrysene, perylene and benzo(a)pyrene were selected as analytes. Several parameters that affected the extraction efficiency such as the extraction time, the concentration of NaCl, the extraction temperature and the agitation speed were optimized. The experimental result indicates that the porous metal membrane possesses high adsorption ability to the tested polycyclic aromatic hydrocarbons (PAHs). Under the optimum conditions, the detection limits of the developed method were in the range of 0.03-0.082 μg L(-1) (S/N = 5), and excellent linear correlations between peak area and concentration of PAHs were found over the range of 0.1-60 μg L(-1). The precisions (RSD) for five replicate extractions of the PAHs from sample solutions were in the range of 2.6-5.0%. The recoveries of the PAHs from tap water and river water samples spiked with 9 PAHs (20 μg L(-1) of each individual PAH) ranged from 83.0% to 112.5%. The porous metal membrane is durable, simple, inexpensive, reproducible and has a high adsorption ability for use in SPE of PAHs.