Solid-phase Extraction Of Organic Compounds Research Articles

Magnetic Solid-Phase Extraction of Organic Compounds Based on Graphene Oxide Nanocomposites.

Graphene oxide (GO) is a chemical compound with a form similar to graphene that consists of one-atom-thick two-dimensional layers of sp2-bonded carbon. Graphene oxide exhibits high hydrophilicity and dispersibility. Thus, it is difficult to be separated from aqueous solutions. Therefore, functionalization with magnetic nanoparticles is performed in order to prepare a magnetic GO nanocomposite that combines the sufficient adsorption capacity of graphene oxide and the convenience of magnetic separation. Moreover, the magnetic material can be further functionalized with different groups to prevent aggregation and extends its potential application. Until today, a plethora of magnetic GO hybrid materials have been synthesized and successfully employed for the magnetic solid-phase extraction of organic compounds from environmental, agricultural, biological, and food samples. The developed GO nanocomposites exhibit satisfactory stability in aqueous solutions, as well as sufficient surface area. Thus, they are considered as an alternative to conventional sorbents by enriching the analytical toolbox for the analysis of trace organic compounds.

Materials for Solid-Phase Extraction of Organic Compounds

This review provides an overview of the most recent developments involving materials for solid-phase extraction applied to determine organic contaminants. It mainly concerns polymer-based sorbents that include high-capacity, as well as selective sorbents, inorganic-based sorbents that include those prepared using sol-gel technology along with structured porous materials based on inorganic species, and carbon nanomaterials, such as graphene and carbon nanotubes. Different types of magnetic nanoparticles coated with these materials are also reviewed. Such materials, together with their main morphological and chemical features, are described, as are some representative examples of their application as solid-phase extraction materials to extract organic compounds from different types of samples, including environmental water, biological fluids, and food.

Magnetic adsorbents based on iron oxide nanoparticles for the extraction and preconcentration of organic compounds

We summarize data published over the last five years on the approaches and methods used in the synthesis of magnetic adsorbents based on iron oxide nanoparticles. A classification of magnetic adsorbents is proposed; examples of their use in the magnetic solid-phase extraction of organic compounds in the analysis of environmental samples, food, and biological fluids are given.

Solid-phase extraction of organic compounds in atmospheric aerosol particles collected with the particle-into-liquid sampler and analysis by liquid chromatography–mass spectrometry

Atmospheric aerosol particles, collected with the particle-into-liquid sampler at SMEARII station in Finland in mid-August 2007, were analysed for biogenic acids. The sample pretreatment method, comprising solid-phase extraction with anion exchange and hydrophilic–lipophilic balance materials, was optimized. Extraction efficiencies of solid-phase extraction from 10 and 20 ml samples were about 100%, with average relative standard deviation of 8.9%, in concentration range from 12.5 to 50 ng/ml of the acid. Extraction of aldehydes was less successful, with efficiencies from 69 to 163% and average 10% deviation. Pretreated samples were analysed by reversed phase high performance liquid chromatography with ion trap mass spectrometric detection. Limits of detection achieved for organic acids with the analytical procedure developed ranged from 9 to 27 μg/l of extracted sample, while limits of quantitation were from 31 to 90 μg/l. Oxidation with ozone was used for the preparation of the acid of β-caryophyllene (β-caryophyllinic acid), which was also studied in aerosol samples. MS 2 experiments were used to confirm the identification of trans-pinic, trans-pinonic and β-caryophyllinic acids. Azelaic, hexadecanoic, cis-pinonic, and cis- and trans-pinic acids were quantitated in the samples with use of authentic standards, while the concentrations of trans-pinonic and β-caryophyllinic acids were determined with cis-pinonic acid as surrogate. Also, the contribution of β-caryophyllene oxidation products to aerosol organic carbon was evaluated. Aldehydes could not be analysed in real samples due to the insufficient extraction. The particle-into-liquid sampler proved to be suitable for the collection of aerosol particles for the elucidation of daily and diurnal variation of selected species. The optimized sample pretreatment, together with the analysis method, offer a promising approach for the study of aerosol chemical composition, where artifact formation is minimal and time resolution is good.

Application of Ceramic Carbon Materials for Solid-Phase Extraction of Organic Compounds

Ceramic carbon materials were developed as new sorbents for solid-phase extraction of organic compounds using chlorpromazine as a representative. The macroporosity and heterogeneity of ceramic carbon materials allow extracting a large amount of chlorpromazine over a short time. Thus, the highly sensitive and selective determination of chlorpromazine in urine sample was achieved by differential pulse voltammograms after only 1-min extraction. The total analysis time was less than 3 min. In comparison with other electrochemical and electrochemiluminescent methods following 1-min extraction, the proposed method improved sensitivity by about 2 and 1 order of magnitude, respectively. The fast extraction, diversity, and conductivity of ceramic carbon materials make them promising sorbents for various solid-phase extractions, such as solid-phase microextraction, thin-film microextraction, and electrochemically controlled solid-phase extraction. The preliminary applications of ceramic carbon materials in chromatography were also studied.

Molecularly imprinted polymers: new molecular recognition materials for selective solid-phase extraction of organic compounds.

During the last few years molecularly imprinted polymers have appeared as new selective sorbents for solid-phase extraction of organic compounds in different samples. Molecular imprinting technology involves the preparation of a polymer with specific recognition sites for certain molecules. Once the polymer has been obtained, it can be used in solid-phase extraction protocols, where a careful selection of the most appropriate solvents to be used in the different steps (sample loading, washing and elution) is needed in order to extract the target analyte selectively. This review describes the state of the art of this methodology, including the preparation of imprinted polymers, a process description for molecularly imprinted solid-phase extraction, as well as more recent applications. It is concluded that molecularly imprinted solid-phase extraction is a powerful tool to selectively isolate certain analytes, and future advances are to be expected in order to widen the field of application.

New, high-capacity carboxylic acid functionalized resins for solid-phase extraction of a broad range of organic compounds

New high capacity carboxylic acid-functionalized resins, prepared by ring-opening-metathesis suspension polymerization, were used for solid-phase extraction of organic compounds from water. Two resins, exhibiting a capacity range of 3.0 and 3.75 mequiv. COOH/g, respectively, have either been employed in their beaded form or in the form of particle-loaded membranes. A large variety of organic compounds such as phenols, alcohols, aldehydes and ketones, carboxylic acids, esters, chlorinated hydrocarbons, amines, nitrosamines as well as polycyclic aromatic aromatic hydrocarbons were succesfully extracted by these materials. For most compounds, a quantitative recovery was observed. The extraction efficiency of the new resins was compared to those of other, commercially available high-performance materials such as Silicalite and Empore disks. The general advantages of the new materials, the mechanism of extraction, differences between membranes and columns containing the new particles as well as the extraction behavior versus the compounds investigated are discussed.

Semi-micro solid-phase extraction of organic compounds from aqueous and biological samples

A technique is described for performing solid-phase extractions on a semi-micro scale. Thin membrane disks 4 mm in diameter containing lightly sulfonated polystyrene or Silicalite particles are placed in the hub of a syringe needle. Aqueous samples (1–6 ml) are passed through the membrane disks and the extracted compounds are subsequently eluted with 20–50 μl of an organic solvent. Unlike solid-phase micro extraction (SPME) which uses a coated fiber, the present method is essentially a total extraction technique. Recoveries >90% were generally obtained for a wide variety of test compounds. The same test compounds in human urine, albumin and human serum samples can be extracted without any pretreatment other than addition of a suitable surfactant. A “double-pass” technique was developed for convenient field sampling.

Chemically modified resins for solid-phase extraction

The packings most widely used for solid-phase extraction are hydrophobic and make poor surface contact with aqueous samples unless the resins are first treated with an activating organic solvent such as methanol. Insertion of an acetyl- or hydroxymethyl group into a porous polystyrene-divinylbenzene resin provides a more hydrophilic surface that is easily wetted by water alone. Small columns of the chemically modified resins were found to be very efficient for the solid-phase extraction of many types of organic solutes from aqueous samples. Comparative recovery studies showed that the modified resins are superior to both silica packings and unmodified organic resins for the solid-phase extraction of organic compounds, and especially for polar organics such as phenols.

Use of membrane extraction disks for on-line trace enrichment of organic compounds from aqueous samples

Membrane extraction disks have been recently introduced for the solid-phase extraction of organic compounds from aqueous samples. The material consists of alkyl-modified silica particles enmeshed in an inert PTEE matrix. Aqueous samples containing polar pesticides and herbicides, are preconcentrated on-line from acidic solutions on membrane extraction disks containing immobilized octadecyl-modified silica and analyzed with an isocratic liquid chromatographic system using PLRP-S as the stationary phase and aqueous acetonitrile mixtures (pH 3) as the eluent. Data on the lifetime and the dimensions of the preconcentration disks, and the efficiency and the repeatability of the procedure are reported. For 10 ml samples, the detection limits of the analytes atrazine, simazine and 2,3,4-trichlorophenol in tap water are 0.1–1 ppb.