Comparison of solvent extraction and solid-phase extraction for the determination of organochlorine pesticide residues in water.

Solid-phase extraction (SPE) of organochlorine pesticide residues from environmental water samples was evaluated using octadecyl (C18)-bonded porous silica. The efficiency of SPE of these pesticide residues from reagent water samples at 1-5 micrograms dm-3 levels was compared with those obtained by solvent extraction with hexane and Freon TF (trichlorotrifluoroethane). Average recoveries exceeding 80% for these organochlorine pesticides were obtained via the SPE method using small cartridges containing 100 mg of 40 microns C18-bonded porous silica. The average recovery by solvent extraction with hexane and Freon TF exceeded 90% in both instances. It was concluded that the recoveries and precision for the SPE of organochlorine pesticides were poorer than those for the solvent extraction method. Organochlorine pesticide residue levels in environmental water samples from two major rivers flowing through predominantly rice-growing areas were monitored by gas chromatography using the solvent extraction method with hexane. Exceptionally high levels of organochlorine pesticide residues such as BHC, DDT, heptachlor, endosulfan and dieldrin were found in these water samples.     

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.     

Design and evaluation of synthetic silica-based monolithic materials in shrinkable tube for efficient protein extraction

Sample pretreatment is a required step in proteomics in order to remove interferences and preconcentrate the samples. Much research in recent years has focused on porous monolithic materials since they are highly permeable to liquid flow and show high mass transport compared with more common packed beds. These features are due to the micro-structure within the monolithic silica column which contains both macropores that reduce the back pressure, and mesopores that give good interaction with analytes. The aim of this work was to fabricate a continuous porous silica monolithic rod inside a heat shrinkable tube and to compare this with the same material whose surface has been modified with a C(18) phase, in order to use them for preconcentration/extraction of proteins. The performance of the silica-based monolithic rod was evaluated using eight proteins; insulin, cytochrome C, lysozyme, myoglobin, β-lactoglobulin, ovalbumin, hemoglobin, and bovine serum albumin at a concentration of 60 μM. The results show that recovery of the proteins was achieved by both columns with variable yields; however, the C(18) modified silica monolith gave higher recoveries (92.7 to 109.7%) than the non-modified silica monolith (25.5 to 97.9%). Both silica monoliths can be used with very low back pressure indicating a promising approach for future fabrication of the silica monolith inside a microfluidic device for the extraction of proteins from biological media.     

System Maps for Retention of Small Neutral Compounds on a Superficially Porous Ethyl-Bridged,Octadecylsiloxane-Bonded Silica Stationary Phase in Reversed-Phase Liquid Chromatography

The system constants of the solvation parameter model are used to prepare system maps for the retention of small neutral compounds on an ethyl-bridged, ocatadecylsiloxane-bonded superficially porous silica stationary phase (Kinetex EVO C18) for aqueous mobile phases containing 10–70% (v/v) methanol or acetonitrile. Electrostatic interactions (cation-exchange) are important for the retention of weak bases with acetonitrile–water but not methanol–water mobile phase compositions. Compared with a superficially porous octadecylsiloxane-bonded silica stationary phase (Kinetex C18) with a similar morphology but different topology statistically significant differences in selectivity at the 95% confidence level are observed for neutral compounds that vary by size and hydrogen-bond basicity with other intermolecular interactions roughly similar. These selectivity differences are dampened with acetonitrile–water mobile phases, but are significant for methanol–water mobile phase compositions containing <30% (v/v) methanol. A comparison of a totally porous ethyl-bridged, octadecylsiloxane-bonded silica stationary phase (XBridge C18) with Kinetex EVO C18 indicated that they are effectively selectivity equivalent.     

Solid phase versus solvent extraction of pesticides from water

The average recovery for 12 pesticides spiked into 100 ml of water at 0.1 ppb was 90% when cartridges containing 100 mg of C-18 bonded porous silica were used for adsorption. Flow rates of up to 200 bed volumes per minute were employed for the adsorption step. Quantitative desorption of the pesticides was accomplished with less than 100l of solvent, thus eliminating the need for a solvent reduction step. The pesticides from samples of surface waters were adsorbed onto C-18 bonded porous silica at the sampling site and the cartridges containing the bonded phase were returned to the laboratory for elution and analysis. The analytical results obtained from use of this procedure agreed with those obtained for duplicate samples of the water that were processed in the laboratory using standard solvent extraction procedures.     

A core-shell magnetic mesoporous silica sorbent for organic targets with high extraction performance and anti-interference ability

C(18)-functionalized mesoporous silica shell was successfully fabricated on the surface of an Fe(3)O(4)/SiO(2) core to obtain an Fe(3)O(4)/SiO(2)/SiO(2)-C(18) magnetic microsphere. The microsphere exhibited high extraction efficiency to organic targets and strong anti-interference ability to natural organic matter. It could be easily isolated from water solution after extraction.     

疏水多孔硅制备及其对水中有机污染物的吸附

以硅酸钠为硅源,盐酸为催化剂,三甲基氯硅烷(TMCS)为表面改性剂,经溶胶-凝胶和表面改性过程制备出一种疏水性多孔硅材料.采用傅里叶变换红外(FTIR)光谱仪、接触角分析仪、氮气物理吸附仪和扫描电子显微镜(SEM)对其结构和性质进行表征.结果表明:所制备的多孔硅具有分等级孔道结构(中孔-大孔),比表面积为566m2·g-1,孔体积高达2.28cm3·g-1,多孔硅与水的接触角为156°,显示出超疏水特征.对甲苯、汽油、柴油和润滑油的吸附量均可高达自身质量的14倍,丰富的孔道使其在几分钟内即可达到饱和吸附.这种多孔硅在汽油/水混合体系中对汽油具有较高的选择性,同时具有良好的再生能力.经正己烷萃取再生后,多孔硅仍能基本保持初始吸附容量.此方法制备的多孔硅材料在吸附分离污水中的有机物和溢油处理方面具有很好的应用前景.     

Multiresidue Analysis of Organic Pollutants in Water by SPE with a C8 and SDVB Combined Cartridge

Abstract

A multi-component target method for screening purposes to determine organic pollutants of different polarities in water is reported. The following classes of chemicals were tested: base-neutral and acidic herbicides, phenolic compounds, polycyclic aromatic hydrocarbons and phthalic acid esters.

Data was initially obtained from the extraction of one liter of water sample, using separate octyl bonded porous silica (C8) and highly crosslinked polystyrene based polymer columns (SDVB) cartridges. A second set of data was obtained using for the extraction a combined cartridge containing both phases. The analysis was carried out directly by GC-MS in SIM mode, without any derivatisation, with the exception of acidic herbicides, derivatised with pentafluorobenzylbromide. The obtained results showed recoveries between 75% and 98% at two different spiking levels, with relative standard deviations below 15%.     

应用于全氟辛烷磺酸萃取富集的全氟癸基修饰毛细管硅胶整体柱的制备及应用

利用溶胶-凝胶法,经过烷氧基硅烷的水解、硅羟基的缩聚、凝胶化、陈化、中孔制备、干燥和表面修饰等步骤制备了全氟癸基修饰的毛细管硅胶整体柱。采用该整体柱对全氟辛烷磺酸(PFOS)进行萃取富集,考察其富集特性和效率,并与传统的C18毛细管硅胶整体柱进行对比。结果表明,全氟癸基修饰毛细管硅胶整体柱(15 cm×75 μm)对PFOS具有更高的吸附量和更好的富集选择性,其平均吸附量可以达到75 ng;样品中PFOS的质量浓度为0.25 mg/L时,富集倍数平均可以达到29倍。此全氟癸基修饰毛细管硅胶整体柱对PFOS具有良好的萃取富集性能,可用于水质中痕量PFOS的萃取富集。     

Silica gel-immobilized-dithioacetal derivatives as potential solid phase extractors for mercury(II)

Dithioacetal derivatives with different para-substituents, XH, CH(3), OCH(3), Cl and NO(2) were synthesized and chemically immobilized on the surface of silica gel for the formation of five newly synthesized silica gel phases (I-V). Characterization of the silica gel surface modification by the organic compounds was accomplished by both the surface coverage determination as well as the infrared spectroscopic analysis. The metal sorption properties of the silica gel phases were studied to evaluate their performance toward metal-uptake, extraction and selective extraction processes of different metal ions from aqueous solutions based on examination of the various controlling factors. The studied and evaluated factors are the pH effect of metal ion solution on the metal capacity values (mmol g(-1)), equilibration shaking time on the percent extraction as well as the structure and substituent (X) effects on the determined mmol g(-1) values. The results of these studies revealed a general rule of excellent affinity of these silica gel phases-immobilized-dithioacetal derivatives for selective extraction of mercury(II) in presence of other interfering metal ions giving rise to a range of 94-100% extraction of the spiked mercury(II) in the metal ions mixture. The potential application of the newly synthesized silica gel phases (I-V) for selective extraction of mercury(II) from two different natural water samples, namely sea and drinking tap water, spiked with 1.0 and 10.0 ng ml(-1) mercury(II) were also studied by column technique followed by cold vapour atomic absorption analysis of the unretained mercury(II). The results indicated a good percent extraction and removal (90-100+/-3%) of the spiked mercury(II) by all the five silica gel phases. In addition, insignificant contribution by the matrix effect on the processes of selective solid phase extraction of mercury(II) from natural water samples was also evident.     

Selective determination of estrogenic compounds in water by microextraction by packed sorbents and a molecularly imprinted polymer coupled with large volume injection-in-port-derivatization gas chromatography-mass spectrometry

A fully automated protocol consisting of microextraction by packed sorbents (MEPS) coupled with large volume injection-in-port-derivatization-gas chromatography–mass spectrometry (LVI-derivatization-GC–MS) was developed to determine endocrine disrupting compounds (EDCs) such as alkylphenols, bisphenol A, and natural and synthetic hormons in river and waste water samples. During method optimization, the extraction parameters as ion strength of the water sample, the MEPS extraction regime, the volume of organic solvent used for the elution/injection step, the type of elution solvents and the selectivity of the sorbents were studied. For optimum in-port-derivatization, 10 μL of the derivatization reagent N,O-bis(trimethylsilyl)triufloroacetamide with 1% of trimethylchlorosilane (BSTFA + 1% TMCS) was used. 17β-Estradiol-molecularly imprinted polymer (MIP) and silica gel (modified with C-18) sorbents were examined for the enrichment of the target analytes from water samples and the obtained results revealed the high selectivity of the MIP material for extraction of substances with estrogen-like structures. Recovery values for most of the analytes ranged from 75 to 109% for the C18 sorbent and from 81 to 103% for the MIP material except for equilin (on C18 with only 57–66% recovery). Precision (n = 4) of the entire analysis protocol ranged between 4% and 22% with both sorbents. Limits of detection (LODs) were at the low ng L⁻¹ level (0.02–87, C18 and 1.3–22, MIP) for the target analytes.     

Polyvinylimidazole/sol–gel composite as a novel solid‐phase microextraction coating for the determination of halogenated benzenes from aqueous solutions

A polyvinylimidazole/sol–gel composite is proposed as a novel solid‐phase microextraction fiber to extract five halobenzenes from the headspace of aqueous solutions in combination with gas chromatography with mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The obtained results showed that porous polyvinylimidazole/sol–gel composite was chemically deposited on fused silica fiber. The effect of important extraction parameters including extraction temperature, extraction time, and salt content were investigated. The optimum conditions were as follows: extraction temperature 25°C, extraction time 20 min, and salt concentration 30 w/v%. Detection limits and relative standard deviations of the developed method for halogenated benzenes were below 0.1 pg/mL and 15%, respectively. Repeatability of the proposed method, explained by relative standard deviation, varied between 5.48 and 9.15% (n = 5). The limits of detection (S/N = 3) ranged between 0.01 and 0.10 ng/L using gas chromatography with mass spectrometry with selected ion monitoring mode. For real sample analysis, three types of water samples with different matrices (ground, surface, and tap water) were studied. The optimized procedure was applied to extraction and method validation of halogenated benzenes in spiked water samples.     

Effect of the structure and density of chemically bonded C18 phase on the recovery of tryptophan and its metabolites from human urine

A series of materials with chemically bonded C18 phase for use as the packings in clean-up columns for solid-phase extraction were prepared. The effects of the monomeric and/or polymeric structure of the chemically bonded phase and of the porous structure of the silica gel support on the recovery of tryptophan and two of its metabolites used as test substances were considered. It appeared that the best recoveries of at least 60% of the three test substances were obtained on material of the "monomer" type containing chemically bonded C18 phase characterized by a high coverage density of alpha RP approximately 3.8 mumol/m2. The use of a silica gel support with a larger pore size and volume permits not only the effective isolation of individual substances, e.g., from urine, but also their 5-fold concentration.     

Preparation of magnetic core mesoporous shell microspheres with C18-modified interior pore-walls for fast extraction and analysis of phthalates in water samples

In this study, core-shell magnetic mesoporous microspheres with C18-functionalized interior pore-walls were synthesized through coating Fe(3)O(4) microspheres with a mesoporous inorganic-organic hybrid layer with a n-octadecyltriethoxysilane (C18TES) and tetraethyl orthosilicate (TEOS) as the silica source and cetyltrimethylammonia bromide (CTAB) as a template. The obtained C18-functionalized Fe(3)O(4)@mSiO(2) microspheres possess numerous C18 groups anchored in the interior pore-walls, large surface area (274.7 m(2)/g, high magnetization (40.8 emu/g) and superparamagnetism, uniform mesopores (4.1 nm), which makes them ideal absorbents for simple, fast, and efficient extraction and enrichment of hydrophobic organic compounds in water samples. Several kinds of phthalates were used as the model hydrophobic organic compounds to systematically evaluate the performance of the C18-functionalized Fe(3)O(4)@mSiO(2) microspheres in extracting hydrophobic molecules by using a gas chromatography-mass spectrometry. Various parameters, including eluting solvent, the amounts of absorbents, extraction time and elution time were optimized. Hydrophobic extraction was performed in the interior pore of magnetic mesoporous microspheres, and the materials had the anti-interference ability to macromolecular proteins, which was also investigated in the work. Under the optimized conditions, C18-functionalized Fe(3)O(4)@mSiO(2) microspheres were successfully used to analyze the real water samples. The results indicated that this novel method was fast, convenient and efficient for the target compounds and could avoid being interfered by macromolecules.     

Optimization by orthogonal array design of solid phase extraction of organochlorine pesticides from water

Summary A two-level orthogonal array design (OAD) to optimize the solid phase extraction of organochlorine pesticides is described. Parameters including eluting solvents, SPE cartridges packed with C₁₈-bonded silica from different manufacturers, duration of air drying, pH, salinity and humic acid have been examined using OAD. This systematic approach was then used to optimize the relevant parameters required for off-line solid phase extraction of organochlorine pesticides from water. The optimized parameters were employed to perform extraction of the pesticides from natural waters.     

Optimization by orthogonal array design of solid phase extraction of organochlorine pesticides from water

Summary A two-level orthogonal array design (OAD) to optimize the solid phase extraction of organochlorine pesticides is described. Parameters including eluting solvents, SPE cartridges packed with C₁₈-bonded silica from different manufacturers, duration of air drying, pH, salinity and humic acid have been examined using OAD. This systematic approach was then used to optimize the relevant parameters required for off-line solid phase extraction of organochlorine pesticides from water. The optimized parameters were employed to perform extraction of the pesticides from natural waters.     

Solid phase extraction system for vitamin D and its major metabolites in human plasma

A new procedure using C18 and silica cartridges for the extraction and subsequent separation of vitamin D and its major metabolites from plasma has been developed and compared to a conventional extraction procedure with respect to lipophilic material extracted as evaluated by high-performance liquid chromatographic profiles. The C18 cartridges were efficient in extracting all compounds tested while subsequent chromatography of the extract on silica cartridges was effective in resolving vitamin D and its metabolites based on increasing polarity. High-performance liquid chromatographic profiles of each silica cartridge fraction clearly demonstrated that the newly conceived solid phase extraction was superior to conventional extraction methods with respect to cleanliness of sample fractions. This difference in lipophilic load between the new and conventional extraction systems was most apparent in the vitamin D and 25-hydroxyvitamin D containing fractions. The new extraction system can be used when total extraction and subsequent analysis of vitamin D and its major metabolites is desired.     

Trace analysis of triazines and organophosphorus pesticides in water

A method for the determination of trace levels of triazines and organophosphorus pesticides in water is presented. The extraction method is based on a solid-phase extraction on C-18 bound silica SPE cartridges. A precolumn filled with Merck C-18 bound silica and home-made C-18 bound silica have been tested at a flow-rate of 3 ml/min with comparable preconcentration yields. A SIM-MS method using a (15)N labelled internal standard has been developed for the organophosphorus pesticides. Detection limits lower than 1 microg/L have been obtained. Separations have been carried out on a conventional GC column OV 17 (1 m) and a capillary column OV 17 (25 m) with a temperature program from 150 degrees C (2 min) to 300 degrees C (rate of 6 degrees C/min).     

Pre-concentration of ultra trace amounts of copper,zinc, cobalt and nickel in environmental water samples using modified C18 extraction disks and determination by inductively coupled plasma–optical emission spectrometry

A highly sensitive and accurate method for pre-concentration and determination of ultra trace amounts of zinc, copper, cobalt and nickel ions in environmental water samples is proposed. The method is based on the solid phase extraction of these ions on C18-bonded silica extraction disks modified with a novel Schiff base 2,2′-[1,6-hexanediyl bis (nitriloethylidine)]bis-1-naphthol (HDN). The retained ions on the prepared solid phase was eluted with 10 mL 0.01 M nitric acid and measured by inductively coupled plasma–optical emission spectrometry. The extraction efficiency and the influence of the type and least amount of eluent for the stripping of ions from the disks, pH, flow rates of sample solution and eluent, amount of HDN, effect of other ions and breakthrough volume were evaluated. The limits of detection of the method were 0.2, 0.2, 0.8 and 0.6 µg L^?1 for zinc, copper, cobalt and nickel, respectively and an enrichment factor of 100 was obtained. The proposed method was applied for determination of zinc, copper, cobalt and nickel ions in some natural and synthetic water samples with satisfactory results.     

A simple preparation of stationary phase of alkylamide reversed-phase liquid chromatograph for the separation of basic substances.

A simple preparation process of alkylamide phase for reversed-phase HPLC (RP-HPLC) is described. The process includes aminopropyltrimethoxysilane firstly reacted with octanoyl chloride, then the intermediate was coupled onto porous silica. The resultant bonded silica has a reproducible ligand surface concentration and homogenous bonded ligand distribution on the porous silica. Characterization of prepared packing was carried out with elemental analysis, solid-state 13C NMR and Fourier transform infrared (FT-IR). Chromatographic evaluations were carried out by using a mixture of organic compounds including acidic, basic and neutral analytes under methanol/water as binary mobile phase. The results showed that the stationary phase have excellent chromatographic properties and can be efficiently used for the separation of basic compounds.