F. Borrull

Molecularly imprinted polymers: new tailor-made materials for selective solid-phase extraction

Solid-phase extraction (SPE) materials are a promising and innovative application of molecularly imprinted polymers (MIPs). These polymers allow certain analytes to be selectively extracted from complex matrices without matrix interference. The applications described in this article include the molecularly imprinted SPE (MISPE) of several kinds of analytes of biological, pharmaceutical and environmental interest. To ensure selectivity emphasis is placed on synthetic considerations and the various steps in the extraction process. Finally, we also report on recent advances in this technique.

Determination of phthalate esters in water samples by solid-phase microextraction and gas chromatography with mass spectrometric detection.

Solid-phase microextraction (SPME) with an 85 microm polyacrylate fiber, coupled to gas chromatography-mass spectrometry was used to determine six phthalate esters and bis(2-ethylhexyl) adipate in water samples. The variables affecting the SPME absorption process were optimized and the method developed was applied to analyze both tap and commercial mineral water samples as well as water from the Ebro river and fishing and industrial ports. For real samples, the linear range in full scan acquisition mode was between 0.02 and 10 microg l(-1) for most compounds, and the limits of detection of the method were between 0.006 and 0.17 microg l(-1). Commercial water samples contained in recipients which were made from different materials were analyzed, and the influence of the material of the recipients on the concentration of phthalates was evaluated.

Solid-phase microextraction coupled to high-performance liquid chromatography to determine phenolic compounds in water samples☆

Solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with ultraviolet (UV) and electrochemical detection (ED) has been applied to determine 11 phenolic compounds considered priority pollutants by the US Environmental Protection Agency. 85 microm polyacrylate fibers were used to extract the analytes from the aqueous samples. Two different designs of the liquid chromatograph were compared in combination with SPME. Dynamic and static modes of desorption in both HPLC designs were compared and the variables affecting both absorption and desorption processes in SPME-HPLC were optimized. Static desorption in both HPLC systems showed better recoveries for the phenolic compounds. The performance of the SPME-HPLC-UV-ED method was evaluated with river water and wastewater samples. The method enabled the determination of phenolic compounds at low levels in these water samples.

New polymeric and other types of sorbents for solid-phase extraction of polar organic micropollutants from environmental water

This article describes different types of sorbents for the solid-phase extraction of polar organic pollutants from environmental water and emphasizes the use of the new synthesized sorbents. The most important new sorbents are the chemically modified polymeric resins with functional groups such as acetyl, hydroxymethyl, benzoyl and o-carboxybenzoyl, and the highly crosslinked polymers. These sorbents are compared and their properties described. Recoveries for the most polar compounds are better when these new sorbents are used. Immunosorbents and molecularly imprinted polymers are new types of extraction sorbents which are specific for a group of compounds and they enable chromatograms with no matrix interference to be obtained when analyzing some polar compounds. The advantages and drawbacks of off-line and on-line procedures are also discussed, and solutions to their limitations are proposed.

Trends in solid-phase microextraction for determining organic pollutants in environmental samples

Abstract Solid-phase microextraction (SPME) is a recent technique for sample preparation. It has been used successfully to analyze environmental pollutants in a variety of matrices such as soils, water, and air. SPME is a solvent-free technique which has a number of advantages over more conventional sample preparation techniques such as liquid–liquid extraction (LLE) and solid-phase extraction (SPE). We describe the most recent developments in SPME and some which are being developed, including its coupling to HPLC and CE, the use of new fibers, and the automation of the entire SPME process and its application to field analysis. A summary is given of the most important parameters for applying this extraction technique to the analysis of environmental samples.

On-line solid-phase extraction with molecularly imprinted polymers to selectively extract substituted 4-chlorophenols and 4-nitrophenol from water.

Three polymers have been synthesised using 4-chlorophenol (4-CP) as the template, following different protocols (non-covalent and semi-covalent) and using different functional co-monomers, 4-vinylpyridine (4-VP) and methacrylic acid (MAA). The polymers were evaluated to check their selectivity as molecularly imprinted polymers (MIPs) in solid-phase extraction (SPE) coupled on-line to liquid chromatography. The solid-phase extraction procedure using MIPs (MISPE), including the clean-up step to remove any interferences, was optimised. The 4-VP non-covalent polymer was the only one which showed a clear imprint effect. This MIP also showed cross-reactivity for the 4-chloro-substituted phenols and for 4-nitrophenol (4-NP) from a mixture containing the 11 priority EPA (Environmental Protection Agency) phenolic compounds and 4-chlorophenol. The MIP was applied to selectively extract the 4-chloro-substituted compounds and 4-NP from river water samples.

Method based on solid-phase microextraction--high-performance liquid chromatography with UV and electrochemical detection to determine estrogenic compounds in water samples.

We determined a group of estrogenic compounds by solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with both ultraviolet (UV) and electrochemical detection (ED). A modified liquid chromatograph was used. Polyacrylate fibers (85 microns) were used to extract the analytes from the aqueous samples. Dynamic and static modes of desorption were compared and the variables affecting both absorption and desorption processes in SPME-HPLC were optimized. Static desorption gave the best recoveries and peak shapes. The performance of the SPME-HPLC-UV-ED method was checked with river water and wastewater. The method enabled estrogenic compounds to be determined at low-microgram l-1 levels in real water samples. Limits of detection were between 0.3 and 1.1 micrograms l-1 using UV detection and between 0.06 and 0.08 microgram l-1 using ED. beta-Estradiol was found in samples from a wastewater treatment plant at concentrations between 1.9 and 2.2 micrograms l-1.

Comparison of different fibers for the solid-phase microextraction of phthalate esters from water

Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) has been applied to determine six phthalate esters and one adipate ester in water. The SPME parameters were optimized for several commercially available fibers. A 65-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) was the fiber selected and was applied to analysis of water from the Ebro river and the industrial port of Tarragona. The studied compounds were found at concentrations ranging from 0.4 microg l(-1) for di-n-butyl phthalate ester (DnBP) to 3.2 microg l(-1) for bis(2-ethylhexyl) phthalate ester (DEHP). The linear range for real samples was from 0.1 to 10 microg l(-1) for most phthalates, and the limits of detection of the method were between 3 and 30 ng l(-1). Repeatability and reproducibility between days (n = 5) for 1 microg l(-1) samples were below 13 and 18%, respectively.

Non-covalent and semi-covalent molecularly imprinted polymers for selective on-line solid-phase extraction of 4-nitrophenol from water samples

Two molecularly imprinted polymers (MIPs) have been synthesised for the selective extraction of 4-nitrophenol (4-NP) from water samples. One polymer was synthesised via a non-covalent approach and the other via a semi-covalent approach. The selectivity of the polymers for 4-NP was evaluated when these polymers were applied in on-line solid-phase extraction (MISPE) coupled to reversed-phase HPLC. The MISPE conditions for both MIPs were optimised and a clean-up step was included to eliminate non-specific interactions. Differences between the two MIPs were observed with the non-covalent MIP being the more selective of the two, whereas the recoveries were slightly higher for the semi-covalent MIP. The performance of the imprinted polymers in the MISPE of real water samples was also evaluated.

Solid-phase microextraction and gas chromatography with mass spectrometric detection for the determination of pesticides in aqueous samples

Abstract Solid-phase microextraction (SPME) is a fast, alternative method for extracting organochlorine, triazine and thiocarbamate pesticides. An 85-μm polyacrylate fiber was used to extract the analytes directly from aqueous samples and then thermal desorption was carried out in the hot injector of a gas chromatograph–mass spectrometer. To enhance the sensitivity of SPME, the temperature and the length of the extraction and desorption steps and the pH and salt concentration of the sample were optimized. The linearity of most of pesticides for real samples was found to be between 0.07 and 30 μg l−1 when GC–MS under full-scan acquisition was used and between 0.005 and 10 μg l−1 when selected-ion monitoring (SIM) acquisition was used. Limits of detection at the sub μg l−1 level were achieved with GC and MS under the full-scan acquisition mode and at the ng l−1 level for MS under SIM acquisition. The repeatability of the method for tap water spiked at a level of 0.5 μg l−1 (n=5) was below 25% (R.S.D.).