Maria Llompart

Ultrasound-assisted emulsification–microextraction of emergent contaminants and pesticides in environmental waters

The analytical use of ultrasound-generated emulsions has recently found a growing interest to improve efficiency in liquid-liquid extraction since they increase the speed of the mass transfer between the two immiscible phases implied. Thus, dispersed droplets can act as efficient liquid-liquid microextractors in the continuous phase, and later they can be readily separated by centrifugation. A novel method based on ultrasound-assisted emulsification-microextraction (USAEME) and gas chromatography coupled to mass spectrometry (GC/MS) has been developed for the analysis of synthetic musk fragrances, phthalate esters and lindane in water samples. Extraction conditions were optimized using a multivariate approach. Compounds were extracted during 10 min in an acoustically emulsified media formed by 100 microL chloroform and 10 mL sample (enrichment factor=100). The method performance was studied in terms of accuracy (recovery=78-114%), linearity (R2> or =0.9990) and repeatability (RSD< or =14%). Limits of detection (LODs) were at the pg mL(-1) level for most of compounds, and at the sub-ng mL(-1) level for the most ubiquitous phthalate esters. USAEME is proposed as an efficient, fast, simple and non-expensive alternative to other extraction techniques such as SPE, SPME and LPME for the analysis of environmental waters including bottled, tap, river, municipal swimming pool, sewage and seaport water samples. Since no matrix effect has been found for any of the water types analyzed, quantification could be carried out by using conventional external calibration, thus allowing a higher throughput of the analysis in comparison with other microextraction techniques based on equilibrium such as solid-phase microextraction.

Solid-phase extraction of phenols

Sample preparation for phenol analysis using solid-phase extraction (SPE) is reviewed. The scope of the review has been restricted to the literature dealing with the analysis of phenols as the main objective. The use, advantages and disadvantages of silica sorbents, polymeric, functionalized, carbon-based and mixed available sorbents, when applied to the separation and preconcentration of phenols, as well as the available experimental devices, are discussed. Other aspects such as phenol derivatisation prior to SPE, solid-phase microextraction, matrix effects and the storage of phenols in SPE cartridges, have been also discussed.

Optimization of a derivatization–solid-phase microextraction method for the analysis of thirty phenolic pollutants in water samples

Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry has been applied to the extraction of 30 phenol derivatives from water samples. Analytes were in situ acetylated and headspace solid-phase microextraction was performed. Different parameters affecting extraction efficiency were studied. Optimization of temperature, type of microextraction fiber and volume of sample has been done by means of a mixed-level categorical experimental design, which allows to study main effects and second order interactions. Five different fiber coatings were employed in this study; also, extraction temperature was studied at three levels. Both factors, fiber coating and extraction temperature, were important to achieve high sensitivity. Moreover, these parameters showed a significant interaction, which indicates the different kinetic behavior of the SPME process when different coatings are used. It was found that 75 microm carboxen-polydimethylsiloxane and 100 microm polydimethylsiloxane, yield the highest responses. The first one is specially appropriated for phenol, methylphenols and low chlorinated chlorophenols and the second one for highly chlorinated phenols. The two methods proposed in this study shown good linearity and precision. Practical applicability was demonstrated through the analysis of a real sewage water sample, contaminated with phenols.

Trace analysis of parabens, triclosan and related chlorophenols in water by headspace solid-phase microextraction with in situ derivatization and gas chromatography-tandem mass spectrometry.

An in situ derivatization solid-phase microextraction method has been developed for the determination of parabens, triclosan and related chlorophenols in water. Acetylated derivatives are selectively determined using gas chromatography with tandem mass spectrometry. Parameters affecting both derivatization and SPME procedures, such as fiber coating, extraction mode, temperature, volume of derivatizating reagent and ionic strength, are studied and optimized through a multifactorial experimental design. The performance of the method is studied in terms of accuracy, linearity, precision and limits of detection. Quantitative recoveries (> or =82%) and satisfactory precision (RSD< or =12%) are obtained. Limits of detection at the low picogram per millilitre level are achieved for all target compounds. Linearity is studied in a wide range of concentrations and an analysis of variance with a lack-of-fit test is run to validate the calibration data. Extraction time profiles are also obtained. Finally, the applicability of the proposed method is demonstrated for several real samples including river water, wastewaters and swimming pool water. Since no matrix effects are observed, quantification can readily be carried out by external calibration with ultrapure water standards.

Ultrasound-assisted emulsification-microextraction of phenolic preservatives in water.

Simultaneous ultrasound-assisted emulsification-microextraction (USAEME) and derivatization combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) is proposed for the first time for the analysis of parabens, triclosan and related phenols in water samples. In situ acetylation was successfully applied for the derivatization of target compounds with high efficiency using non-expensive reagents. The proposed method exhibits many advantages such as simplicity, efficiency, low cost, and minimum solvent consumption. In addition, the whole analytical process, including sample preparation and determination, is performed in only 20 min. A multifactorial experimental design was employed to study and optimize the main variables potentially affecting the microextraction and derivatization processes (extraction solvent, phase ratio, sodium chloride concentration, extraction time, and acetic anhydride volume). The performance of the method was studied in terms of accuracy, linearity, precision, and enrichment factor. Quantitative recoveries (>or=85%) were obtained for all target compounds, and method precision was also satisfactory (RSD<or=13%) even for complex samples. Enrichment factors ranging from 100 to 200 were obtained, allowing achieving limits of detection at the low picogram per millilitre for most of the target compounds. Several real samples, including wastewaters, river waters and swimming pool water, were analyzed. Since matrix effects were not observed, quantification can easily be performed using external calibration with acetylated standards, allowing a high sample throughput.

Analysis of industrial contaminants in indoor air: Part 1. Volatile organic compounds, carbonyl compounds, polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

This article reviews recent literature on the analysis of industrial contaminants in indoor air in the framework of the REACH project, which is mainly intended to improve protection of human health and the environment from the risks of more than 34 millions of chemical substances. Industrial pollutants that can be found in indoor air may be of very different types and origin, belonging to the volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) categories. Several compounds have been classified into the priority organic pollutants (POPs) class such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDD/PCDFs) and related polychlorinated compounds, and polycyclic aromatic hydrocarbons (PAHs). Many of these compounds are partially associated to the air gas phase, but also to the suspended particulate matter. Furthermore, settled dust can act as a concentrator for the less volatile pollutants and has become a matrix of great concern for indoors contamination. Main literature considered in this review are papers from the last 10 years reporting analytical developments and applications regarding VOCs, aldehydes and other carbonyls, PCBs, PCDDs, PCDFs, and PAHs in the indoor environment. Sample collection and pretreatment, analyte extraction, clean-up procedures, determination techniques, performance results, as well as compound concentrations in indoor samples, are summarized and discussed. Emergent contaminants and pesticides related to the industrial development that can be found in indoor air are reviewed in a second part in this volume.

Headspace solid phase microextraction (HSSPME) for the determination of volatile and semivolatile pollutants in soils.

We have investigated the use of headspace solid phase microextraction (HSSPME) as a sample concentration and preparation technique for the analysis of volatile and semivolatile pollutants in soil samples. Soil samples were suspended in solvent and the SPME fibre suspended in the headspace above the slurry. Finally, the fibre was desorbed in the Gas Chromatograph (GC) injection port and the analysis of the samples was carried out. Since the transfer of contaminants from the soil to the SPME fibre involves four separate phases (soil-solvent-headspace and fibre coating), parameters affecting the distribution of the analytes were investigated. Using a well-aged artificially spiked garden soil, different solvents (both organic and aqueous) were used to enhance the release of the contaminants from the solid matrix to the headspace. It was found that simple addition of water is adequate for the purpose of analysing the target volatile organic chemicals (VOCs) in soil. The addition of 1 ml of water to 1 g of soil yielded maximum response. Without water addition, the target VOCs were almost not released from the matrix and a poor response was observed. The effect of headspace volume on response as well as the addition of salt were also investigated. Comparison studies between conventional static headspace (HS) at high temperature (95 degrees C) and the new technology HSSPME at room temperature ( approximately 20 degrees C) were performed. The results obtained with both techniques were in good agreement. HSSPME precision and linearity were found to be better than automated headspace method and HSSPME also produced a significant enhancement in response. The detection and quantification limits for the target VOCs in soils were in the sub-ng g(-1) level. Finally, we tried to extend the applicability of the method to the analysis of semivolatiles. For these studies, two natural soils contaminated with diesel fuel and wood preservative, as well as a standard urban dust contaminated with polyaromatic hydrocarbons (PAHs) were tested. Discrimination in the response for the heaviest compounds studied was clearly observed, due to the poor partition in the headspace and to the slow kinetics of all the processes involved in HSSPME.

Solid-Phase Microextraction and Headspace Solid-Phase Microextraction for the Determination of Polychlorinated Biphenyls in Water Samples

A solid-phase microextraction (SPME) method has been developed for the quantification of polychlorinated biphenyls (PCBs) in water samples. Parameters such as sampling time, volume of water, volume of headspace, temperature, addition of salts, and agitation of the sample were studied. Because the time for reaching equilibrium between phases takes several hours or days, depending on the experimental conditions, it was necessary to work in nonequilibrium conditions to keep the sample analysis to a reasonable time. The possibility of sampling the headspace over the water sample (HSSPME), instead of immersing the fiber into the water (SPME), was also investigated, and despite the low partition of PCB into the headspace, HSSPME offered higher sensitivity than SPME at 100 °C. The adsorption kinetics for SPME at room temperature, SPME at 100 °C, and HSSPME at 100 °C were investigated and compared. The proposed HSSPME method exhibits excellent linearity and sensitivity. The detection limit was in the sub-ng/L level. This method has been applied to a real industrial harbor water and compared with liquid-liquid extraction. Both techniques offered similar results, but HSSPME was much more sensitive and considerably faster, by eliminating all the manual process intensive sample workup, and reduces solvent consumption entirely. The only drawback was that matrix effects were observed, but with the addition of deuterated surrogates to the sample or the use of a standard addition calibration, accurate quantification can be achieved.

Microwave-assisted extraction: Application to the determination of emerging pollutants in solid samples

Flame retardants, surfactants, pharmaceutical and personal care products, among other compounds, have been the object of numerous environmental studies. In this chapter, the application of microwave-assisted extraction (MAE) in the development of analytical methods for several groups of organic compounds with growing concern as emerging pollutants has been considered. Compared to other extraction techniques, optimization of MAE experimental conditions is rather easy owing to the low number of influential parameters (i.e. matrix moisture, nature of the solvent, time, power, and temperature in closed vessels). The great reduction in the extraction time and solvent consumption, as well as the possibility of performing multiple extractions, increasing the sample throughput, can also be highlighted among MAE advantages. In summary, the study of several applications of MAE to environmental problems demonstrates that this technique constitutes a good alternative for the determination of organic compounds in environmental samples. It can be used as a rapid screening tool, and also to obtain detailed information on the sources, behaviour and fate of emerging pollutants in environmental matrices.

Sonochemical degradation of triclosan in water and wastewater

The sonochemical degradation of 5 microg l(-1) triclosan, a priority micro-pollutant, in various environmental samples (seawater, urban runoff and influent domestic wastewater) as well as in model solutions (pure and saline water) was investigated. Experiments were conducted with a horn-type sonicator operating at 80 kHz frequency and a nominal applied power of 135 W, while solid-phase microextraction coupled with gas chromatography-electron capture detector (SPME/GC-ECD) was employed to monitor triclosan degradation. The latter followed pseudo-first order kinetics with the rate constant being (min(-1)): 0.2284 for seawater>0.1051 for 3.5% NaCl in deionised water>0.0597 for centrifuged urban runoff approximately 0.0523 for untreated urban runoff >0.0272 for deionised water >0.0063 for wastewater influent. SPME/GC-ECD and SPME coupled with gas chromatography-mass spectrometry (SPME/GC-MS) were also used to check for the formation of chlorinated and other toxic by-products; at the conditions in question, the presence of such compounds was not confirmed.