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Air quality is a global concerning topic because of its great impact on the environment and health. Because of that, the study of atmospheric aerosols looking for harmful pollutants is rising, as well as the interest in the origin of the contaminants. Depending on the nature and size of the aerosols, some elements can be detected at a great distance from the emission source, even in Antarctica, where this study is conducted. Several samples of PM filters from 2018 to 2019 (Deception Island) and 2019-2020 (Livingston Island) campaigns have been analyzed by three powerful spectroscopic techniques: FESEM (Field Emission Scanning Electron Microscopy), LIBS (Laser Induced Breakdown Spectroscopy), and ICP-MS (Inductively Coupled Plasma Mass Spectrometry). These techniques have allowed us to find some heavy metals in the air of the Antarctic region (Al, Fe, Ti, Ni, Cr, and Mn). Deeper studies on ICP-MS results have confirmed those results and have also provided information on their potential sources. Thus, while Al, Fe, Ti and Mn concentrations can be explained by crustal origin, Ni and Cr presented high values only coherent with important human contribution. The results point out that the Antarctic region is no longer a clean and isolated environment from human pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The non-destructive spectroscopic characterization of airborne particulate matter (PM) was performed to gain better knowledge of the internal structures of atmospheric aerosols at the particle level in the Antarctic region, along with their potential sources. PM and soil samples were collected during the 2016-2017 austral summer season at the surroundings of the Spanish Antarctic Research Station "Gabriel de Castilla" (Deception Island, South Shetland Islands). PM was deposited in a low-volume sampler air filter. Raman spectroscopy (RS) and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) were used to determine the elemental and molecular composition of the individual aerosol and soil particles. Filter spectra measured by these techniques revealed long-range atmospheric transport of organic compounds (polystyrene and bacteria), local single and cluster particles made of different kinds of black carbon (BC), exotic minerals (polyhalite, arcanite, niter, ammonium nitrate, syngenite and nitrogen, phosphorus, and potassium (NPK) fertilizer), and natural PM (sea salts, silicates, iron oxides, etc.). In addition to the filter samples, forsterite and plagioclase were discovered in the soil samples together with magnetite. This is the first report of the presence of a microplastic fiber in the Antarctic air. This fact, together with the presence of other pollutants, reflects that even pristine and remote regions are influenced by anthropogenic activities., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Atmospheric aerosols (particulate matter - PM) affect the air quality and climate, even in remote areas, such as the Antarctic Region. Current techniques for continuous PM monitoring are usually complex, costly, time consuming and do not provide real-time measurements. In this work, based on micro laser-induced breakdown spectroscopy (LIBS), an innovative method with an optical design and multi-elemental scanning imaging, is presented to characterize PM collected in filters from Antarctica. After following a simple protocol and under atmospheric pressure, the new approach allows to obtain a global visualization of the elemental PM composition of the filters with a minimum sample destruction and preparation. For the first time, we were able to map the localization of pollutants in filters at high spatial resolution and speed. This recent method offers a new insight on the characterization of PM, particularly in isolated areas, where no complex equipment and real time measurements are demanded., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Suspended particulate matter (SPM) measurements and backward air mass trajectory analysis using the HYSPLIT model were performed to better understand the main sources and transport pathways of heavy metals in atmospheric aerosols reaching the Antarctic region. Field campaigns were carried out during the austral summer 2016-2017 at the "Gabriel de Castilla" Spanish Antarctic Research Station, located on Deception Island. Aerosols were deposited in an air filter through a low-volume sampler and chemically analysed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The study of air masses and high enrichment factor values of several elements (Hf, Zr, As, Cu, Sn, Zn, Pb) together with their correlations (Hf/Zr, V/As, Ti/Mn and Cu/Sn) suggests a potentially significant role of three main sources in this area: remote maritime traffic, local petrol combustion (generators and/or tourist cruises), and remote/local crust. Additionally, the investigation of atmospheric flow patterns through backward trajectory analysis revealed that Hf/Zr correlation was related to a remote crustal origin, V/As to anthropogenic local pollution, Ti/Mn to terrestrial inputs on the island and Cu/Sn to remote anthropogenic sources. Overall, the present study demonstrates the existence of anthropogenic pollution at this remote site from distant as well as local sources following the Antarctic circumpolar wind pattern., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The present work reports on the analysis of atmospheric aerosols in the Antarctic region, Deception Island, collected during austral summer 2016-2017 by field measurements carried from Gabriel de Castilla Spanish Research Station. A low-volume sampler was used to capture the aerosols depositing them onto the air filters. A chemical analysis of the samples using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) provided the total carbon (TC), organic carbon (OC), elemental Carbon (EC) and elements such as Al, Ca, Fe, K, Mg, Na, P, S, Cu, Pb, Sr, Ti, Zn and Cr. The average mass concentration of particulate matter (PM 10 ) originated by natural and anthropogenic activities was calculated as 10 ± 4 μg/m 3 , although values such as 28.2 μg/m 3 were also obtained which is very high even when compared to other places in the coast of the Antarctic region. In addition, high enrichment factors have been found for elements such as Pb, Cr, Cu and Zn showing a remote anthropogenic contribution to particulate matter in this region. Correlations were found between Na, Mg, Ca, Al, Ti and S, where Na/Mg displayed the influence of marine environments, S correspond to volcanic activities, Ca to penguin colonies and influence of sea whereas Al/Ti indicated the crustal origin. Polar contour graphical maps were obtained from meteorological data using chemometrics methods, which allowed reproducing wind maps revealing the distribution of the aerosols and possible emission sources of different elements in the area. Given that this island has not been previously studied for atmospheric contamination, this work provides an interesting insight about the site-specific characteristics of particulate matter., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The present work reports the distribution of pollutants in the Madrid city and province from 22 monitoring stations during 2010 to 2017. Statistical tools were used to interpret and model air pollution data. The data include the annual average concentrations of nitrogen oxides, ozone, and particulate matter (PM 10 ), collected in Madrid and its suburbs, which is one of the largest metropolitan places in Europe, and its air quality has not been studied sufficiently. A mapping of the distribution of these pollutants was done, in order to reveal the relationship between them and also with the demography of the region. The multivariate analysis employing correlation analysis, principal component analysis (PCA), and cluster analysis (CA) resulted in establishing a correlation between different pollutants. The results obtained allowed classification of different monitoring stations on the basis of each of the four pollutants, revealing information about their sources and mechanisms, visualizing their spatial distribution, and monitoring their levels according to the average annual limits established in the legislation. The elaboration of contour maps by the geostatistical method, ordinary kriging, also supported the interpretation derived from the multivariate analysis demonstrating the levels of NO 2 exceeding the annual limit in the centre, south, and east of the Madrid province.

Separation of enantiomers remains a challenge owing to their identical physical and chemical properties in an achiral environment, and research on specialized separation techniques such as multidimensional achiral-chiral liquid chromatography continues to resolve individual enantiomers in complex samples. Recent advances in application of multidimensional liquid chromatography applied to chiral analysis are reviewed. For this reason, benefits of achiral-chiral coupling are shown, with emphasis in applications on biological and pharmaceutical fields as well as pesticide analysis. A description of standard instrumental setup in both heart-cut and comprehensive multidimensional liquid chromatography is shown. The most broadly used chiral stationary phases for multidimensional liquid chromatography are summarized. An extensive overview of different interface designs applied to complex samples is presented., (Copyright © 2013 John Wiley & Sons, Ltd.)

A direct chiral LC-UV method was optimized for the determination of salbutamol (SAL) β2 -agonist in environmental water. Two commercially available columns were evaluated: teicoplanin Chirobiotic-T™ (150 × 2.1 mm i.d., 5 µm) and vancomycin Chirobiotic-V™ (150 × 2.1 mm i.d., 5 µm). Finally, teicoplanin chiral stationary phase was selected for SAL enantiomer resolution. In order to preserve its integrity and maintain the column performance for longer time, the use of additives such as triethylamine (TEA) in the mobile phase was avoided. Experimental design was applied to simultaneously evaluate the influence of several parameters involved in enantiomer separation and to establish the conditions for acceptable resolution and performance in short analysis time. Optimum mobile phase was methanol-20 mM ammonium acetate buffer at pH 4.5 (98:2, v/v). A solid-phase extraction procedure for sample pre-concentration and clean-up allowed the determination of chiral SAL residues in natural water samples spiked at low concentrations in the range 1.0-20 ng mL(-1) . Reproducible recoveries, between 77 and 98%, were obtained and matrix effect was negligible. Injection of sample solutions at low elution strength permitted the SAL enantioresolution in the natural water complex matrix with satisfactory sensitivity and precision., (Copyright © 2013 John Wiley & Sons, Ltd.)

A method for the analysis of serotonin (5-HT) and its precursors, 5-hydroxytryptophan (5-HTP) and l-tryptophan (TP) in chocolate samples by capillary liquid chromatography-mass spectrometry (cLC-MS) has been developed. Optimum chromatographic conditions were established by using a personalized multifactorial experimental design. Finally the cLC separation was achieved through a mixture of acetonitrile and 5mM ammonium formate at pH 4 (3:97, v/v) as mobile phase in gradient elution, setting the injection volume at 10 μL and using pure water as injection solvent for focusing purposes on the head of the capillary column. For extraction of targets in chocolate samples a new, fast and simple procedure based on the use of acidic extraction medium and sonication was developed. Working in selected ion mode (m/z 177 for 5-HT, m/z 205 for l-tryptophan and m/z 221 for 5-HTP) detection limits were between 0.01 and 0.11 μg g(-1) and linearity was in the concentration range of 0.5-25 μg g(-1). Recoveries higher than 76% with RSDs lower than 8% were obtained from spiked samples for all analytes, showing the effectiveness of the proposed method. Serotonin and its precursors were determined in 5 kinds of commonly consumed chocolates with different cocoa contents (70-100%). The highest serotonin content was found in chocolate with a cocoa content of 85% (2.93 μg g(-1)). Regarding l-tryptophan, the highest content of this amino acid (13.27-13.34 μg g(-1)) was found in chocolate samples with the lowest cocoa content (70-85%). 5-Hydroxytryptophan was not detected in any chocolate samples., (Copyright © 2011 Elsevier B.V. All rights reserved.)

In this paper, the enantiomeric separation of two aryloxyphenoxypropionic esters (fluazifop-butyl and quizalofop-ethyl) and a safener herbicide (mefenpyr-diethyl), which is widely used for protecting crop plants, has been studied by direct liquid chromatography (LC) with UV detection on an α(1)-acid glycoprotein as chiral stationary phase. Optimization of separation conditions was done by factorial experimental design. Experimental factors and ranges selected were propanol (5-10%), phosphate buffer pH (6.5-7.0), and column temperature (15-25 °C). Responses were expressed in terms of enantioresolution (R(s)) and adjusted retention time of the second eluted enantiomer (t(r2)'). The chemometric method used to explore data was response surface analysis. Multiple response analyses were carried out to determine the combination of experimental factors which simultaneously optimize experimental responses. Under optimum conditions for enantioseparation of each herbicide, partially overlapped or fully resolved enantiomers were obtained. Deconvolution tools were employed as an integration method to fit chromatographic data and to achieve a more precise enantiomeric ratio (ER) and enantiomeric fraction (EF) values. Applicability of both direct chiral LC and peak deconvolution methods was evaluated in spiked soil samples at different R/S enantiomeric ratios. Acceptable and reproducible recoveries between 71% and 96% with precision in the range 1-6% were achieved for herbicide-spiked levels from 0.50 to 9.0 μg g(-1). In addition, parameters such as R(s), ER, and EF were calculated and compared with values obtained using the common valley drop integration method.

This paper describes a multivariate approach to study the effect on chromatographic conditions and to optimize such conditions in capillary liquid chromatography when high injection volumes are required. Several separations have been evaluated by using isocratic and gradient solvent elution, as well as isocratic elution combined with temperature programming. In this study, easily ionisable organic compounds with low logP have been used as representative analytes. Injection volume and nature of the injection solution have been evaluated in order to increase the sensitivity (peak area) and column performance (N values). The equations obtained by multiple linear regressions and response surfaces allow achieving the optimum on-column focusing conditions for chlorophenoxy acids, carbamates and heterocyclic amines., (Copyright © 2010 Elsevier B.V. All rights reserved.)

In the present paper, we have developed a capillary liquid chromatography with MS detection for the determination at ngg⁻¹ levels of four heterocyclic aromatic amines (MeIQx, norharman, harman and harmine), a group of mutagenic and carcinogenic compounds that can potentially be produced in protein-rich food during processing operations. They have been determined in commercial ready-to-eat (RTE) smoked salmon and soft cheese treated with E-beam irradiation. On the basis of experimental design studies and operating conditions of MS detector, best chromatographic conditions were obtained using a Luna® C¹⁸ capillary column (150 mm × 0.3 mm I.D.) with a mixture of acetonitrile-ammonium formate 5 mM pH 3.6 buffer (13:87, v/v) as mobile phase. To improve sensitivity, large injection volumes (20 μL) and injection solutions of low elution strength were employed. Sample preparation procedure included a previous treatment with 1M NaOH, followed by two solid-phase extraction steps; firstly on diatomaceous earth and then on mixed-mode cartridges. Heterocyclic amines were detected neither in irradiated and in non-irradiated samples, indicating that they were not formed by the radiation effect even at doses higher than those indicated in the Food Safety Objective established by regulatory agencies. RTE food samples were spiked at concentration levels in the range 10-30 ngg⁻¹. Recoveries higher than 85% (n=3 for each spiked level) were obtained, showing the effectiveness of the proposed methodology., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Changes in free amino acids content and its potential racemization in ready-to-eat foods treated with E-beam irradiation between 1 and 8 kGy for sanitation purposes were studied. A simple heart cut two-dimensional high performance liquid chromatographic method (LC-LC) for the simultaneous enantiomeric determination of three pairs of amino acids used as markers (tyrosine, phenylalanine, and tryptophan) is presented. The proposed method involves the use of two chromatographs in an LC-LC achiral-chiral coupling. Amino acids and their decomposition products were firstly separated in a primary column (C(18)) using a mixture of ammonium acetate buffer (20 mM, pH 6) (94%) and methanol (6%) as the mobile phase. Then, a portion of each peak was transferred by heart cutting through a switching valve to a teicoplanin-chiral column. Methanol (90%)/water (10%) was used as the mobile phase. Ultraviolet detection was at 260 nm. Detection limits were between 0.16 and 3 mg L(-1) for each enantiomer. Recoveries were in the range 79-98%. The LC-LC method combined with the proposed sample extraction procedure is suitable for complex samples; it involves an online cleanup, and it prevents degradation of protein, racemization of L-enantiomers, and degradation of tryptophan. Under these conditions, D-amino acids were not found in any of the analyzed samples at detection levels of the proposed method.

Some of the optimization methods in reversed phase high-performance liquid chromatography (RP-HPLC) are based on resolution of the critical band pair. Mobile phase composition is changed systematically to establish those conditions giving an acceptable resolution for such a critical band pair, but sometimes the critical pair may change with the separation conditions, which obliges to identify it for each of those conditions. In the case of ionizable compounds, more than two bands may be involved in resolution, showing--in some cases--changes in the elution order when the mobile phase composition was modified. In this paper, an alternative way that does not identify the critical pair after changing experimental conditions is proposed. The relative separation of the three bands involved in two alternating critical band pairs is evaluated as a sort of conjugate or combined resolution, represented as contour maps vs. two variables (content of organic modifier and pH). These maps are obtained from data of chromatograms made under different separation conditions; these conditions were generated by experimental design and data was mathematically processed with a computer program. Analytes of three families that have acid-base properties, triazines, phenoxyacids, and phenols, were used for this purpose. The chromatographic behavior when elution order reversion of ionizable compounds exists is studied.

Heterocyclic aromatic amines (HAs) are a group of mutagenic and carcinogenic substances present in significant amounts in cooked meat and fish that can potentially be formed during food processing operations. This paper proposes a capillary liquid chromatography method with diode array detection for the trace-level determination of three HAs, namely, MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline), norharman (9H-pyrido[3,4-b]indole) and harman (1-methyl-9H-pyrido[3,4-b]indole), in ready-to-eat (RTE) cooked ham processed by electron-beam (accelerated electrons) irradiation to eliminate pathogenic microorganisms and to extend its shelf-life. The HAs selected have frequently been detected and quantified in a wide range of food and could be potential markers to indicate the presence of these toxic compounds. The method is based on the separation in an Inertsil C(8) capillary column (150 mm x 0.3-mm internal diameter, 3 microm) by gradient elution mode using a mixture of acetonitrile and 30 mM ammonium acetate pH 4.5 buffer as the mobile phase. Detection was at 250 and 265 nm and, to improve sensitivity, large injection volumes (20 microL) and on-column focusing techniques based on the injection of HA samples in low organic solvent strength solutions were employed. A simple and short solid-phase extraction and purification procedure was also optimized for sample preparation. Nonirradiated and irradiated RTE cooked ham samples at doses between 1 and 8 kGy were analyzed. HAs were not detected in any of the samples analyzed; so both types of samples were spiked at concentration levels in the range 5-25 ng g(-1), which may be found in meat products. The quality parameters of the method developed in the food matrix were established, and detection limits around 0.3 ng g(-1) were obtained. Spiked recoveries between 70 and 79% (n = 3 for each spiked level) relative standard deviations between 1 and 5% were also obtained, showing the effectiveness of the proposed method.

Simple one- and two-dimensional high-performance liquid chromatography (HPLC) methods for the simultaneous enantiomeric determination of alkyloxyphenoxypropionic acid herbicides is presented. Compounds studied were ( R, S)-2-[4-(2,4-dichlorophenoxy)phenoxy]propionic acid (diclofop-acid) and ( R, S)-2-[4-(2,4-dichlorophenoxy)]methyl propionate (diclofop-methyl). Mobile phases necessary to separate their enantiomers on an alpha1-acid glycoprotein chiral stationary phase are different; therefore, the simultaneous separation by an isocratic mode is not possible. The chiral separation method proposed involves a one-step gradient allowing for the simultaneous determination of both racemic enantiomers. Detection limits of the method were 0.03 mg/L for both diclofop-acid enantiomers and 0.14 and 0.15 mg/L for diclofop-methyl enantiomers, respectively. The two-dimensional method involves the use of two chromatographs in one achiral-chiral coupling. The LC-LC method is more suitable for complex samples because it involves an online cleanup effect. Detection limits were 1.25 and 1.87 mg/L for diclofop-acid and 2.70 and 3.02 mg/L for diclofop-methyl enantiomers, respectively. Accuracy, repeatability, and reproducibility have been studied in standard samples and a technical product.

Chlorophenoxy acid herbicides are intensively applied to get rid of unwanted plants because of their low cost and selectivity. Due to their toxicity, which depends on their chemical form, the European Community has established legal directives to restrict their use and to control their maximum residue levels in several matrices. Determination of chlorophenoxy acids-2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2-(2,4-dichlorophenoxy)propanoic acid (2,4-DP), 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP), 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB) and 2-(2,4,5-trichlorophenoxy)propanoic acid (2,4,5-TP) in spiked human urine samples has been carried out by capillary LC, after solid-phase extraction on a column packed with silica C18 restricted-access material. Chromatographic analysis was performed in gradient-elution mode at 25 degrees C, with injection of 20 microL low-organic-solvent composition herbicide solutions for focusing purposes on the head of the capillary column, and diode array detection at 232 nm. Urine samples collected during 24 h from healthy and unexposed volunteers were spiked in the concentration range 25-150 microg L(-1); recoveries obtained were between 66 and 100% (n = 6 for each spiked level) and RSDs (relative standard deviations) were between 1 and 5%. Detection limits in the urine samples from volunteers were between 3.5 and 6.0 microg L(-1). The developed methodology has allowed the clean-up and preconcentration of low volumes of untreated human urine without previous treatment, showing the effectiveness of the employed SPE sorbent for extracting the target analytes and ultimately resulting in the reduction of the sample-preparation time.

In this work, the effect of temperature in isothermal and programmed modes on several chromatographic parameters such as retention factor, selectivity, resolution and plate number has been discussed. A critical comparison of isocratic/isothermal, gradient/isothermal and isocratic/program temperature modes has been made. Two representative families of pesticides have been selected for this study. One includes ionisable chlorophenoxy acids and two of their esters, some of which show similar polarities. The other one contains several weakly polar carbamates. Analysis was carried out using a reversed-phase capillary high-performance liquid chromatography (HPLC) system and focusing technique with UV or diode array detection (DAD).

A capillary liquid chromatography (cLC) method with gradient elution has been used to determine chlorophenoxy acid herbicides: 2,4-dichlorophenoxyacetic acid, 4-chloro-2-methylphenoxyacetic acid, 2-(2,4-dichlorophenoxy)propanoic acid, 2-(4-chloro-2-methylphenoxy)propanoic acid, 4-(2,4-dichlorophenoxy)butanoic acid, 4-(4-chloro-2-methylphenoxy)butanoic acid, 2-(2,4,5-trichlorophenoxy)propanoic acid, 2,4-dichlorophenoxyacetic-1-methyl ester and 2,4-dichlorophenoxyacetic-1-butyl ester in spiked apple juice samples with amounts between 0.025 and 0.150 mg kg(-1) of each herbicide. Clean-up and preconcentration of acid and esters were carried out in an Oasis MCX polymer. Detection limits obtained by cLC, between 0.005 and 0.018 mg kg(-1), allowed the determination of chlorophenoxy acids and their esters in apple juice samples around the levels permitted by the European Regulations, with recoveries in the range 84-99% and RSDs between 1 and 4%.

A rapid high-performance liquid chromatography (HPLC) method using a monolithic column with UV detection at 238 nm was developed for the determination of fenpropathrin, betacyfluthrin, deltamethrin, and permethrin (cis and trans isomers) in whole urine. The method is based on the use of a monolithic chromatographic column and a restricted access material (RAM) cartridge for sample preparation. The mobile phase was water/acetonitrile (42:58 v/v), the flow rate was 3 mL min(-1), and chromatographic separation was carried out in 10 min. The separation of cis and trans isomers of permethrin was also possible under the above-mentioned conditions. Detection limits in reconstituted whole urine samples were between 0.9 microg L(-1) for betacyfluthrin and 4.4 microg L(-1) for fenpropathrin and trans-permethrin. Recoveries for urine samples spiked with different amounts of pyrethroids (between 19 microg L(-1) and 75 microg L(-1)) were in the 70+/-6 to 90+/-7% range.

An analytical procedure, oxygen bomb combustion-ion chromatography (IC), has been developed for the determination of total chlorine in Automotive Shredder Residues (ASR). Samples of these residues are fired under elevated oxygen pressure (30 atm) and the combustion products are transferred into a Na2CO3/NaHCO3 absorbent solution containing 1% of H2O2; the chlorine contents are then evaluated by ion chromatography. The use of the non-suppressed IC determination with a conductivity detector provides a rapid, sensitive and selective method for chlorine determination in ASR, allowing determinations of this heteroatom at levels below 1% in the presence of bromine and sulfur. Moreover, the proposed method allows the simultaneous determination of chlorine, bromine and sulfur which are potential environmental hazards.

Solid-phase extraction is an attractive alternative in sample preparation because it overcomes many drawbacks of liquid-liquid extraction and makes on-line determination possible by hyphenation with chromatographic techniques. Driven by the need for more effective and more selective sorbents, advances in solid-phase extraction include the development of new materials. This paper describes different types of chemically modified sorbents for the solid-phase extraction of compounds from aqueous samples. Chemical introduction of different functional groups into a polymeric resin improves the efficiency of solid-phase extraction by providing better surface contact with the aqueous samples; also, these sorbents have a greater capacity than the typical solid-phase materials for polar compounds have. The most important new sorbents are the chemically modified resins based on styrene-divinylbenzene copolymers. Preparation of these new sorbents is described, and advantages and drawbacks of off-line procedures and on-line procedures are also discussed. Applications for off-line and on-line chromatographic determinations of polar compounds are presented.

A method for quantitative evaluation of pentachlorophenol (PCP) in sawdust has been developed. Pentachlorophenol is extracted from the solid matrix with 0.5 M sodium hydroxide and preconcentration was carried out using quinolin-8-ol immobilized on controlled pore glass. Determination was carried out by using liquid chromatography with detection at 240 nm. Recoveries were between 84 and 97% at 1-3 microg/g.

The efficiency of an adsorbent consisting of quinolin-8-ol immobilized on controlled-pore glass which was packed in a minicolumn to preconcentrate nitrophenols in the presence of iron(III) has been established. Retention was carried out at acidic pH in the presence of 20 mM iron(III). Methanol-30 mM formic acid-sodium formate aqueous solution (pH 4.2) (65:35) was used in a one-step elution. Determinations were carried out by using liquid chromatography with detection at 350 nm. Determination of trace amounts of dinoseb in lemon juice was carried out with a minimum sample preparation. Recoveries were between 89 and 100% at 200-33 micrograms l-1. The maximum admissible concentration in fruit juice dictated by the Spanish and European Community legislation can be measured.

A multicomponent analysis method is proposed for the determination of chlorophenols by diode array derivative spectrophotometry. The method is based on formation of ion-pairs with tetrabutylammonium as counterion and extraction in chloroform at pH 9.1. Quantitative determinations (within the 2-20 mg/l. concentration range) of two-, three- and four-component mixtures were possible, using the first derivative spectra and a least-squares computer programme.