M.F. Alpendurada

Multiresidue method for the simultaneous determination of four groups of pesticides in ground and drinking waters, using solid-phase microextraction–gas chromatography with electron-capture and thermionic specific detection

A common sample preparation procedure capable of efficiently concentrating various groups of pesticides, taking advantage of universal detectors like the mass spectrometer or combined techniques of group selective detectors like gas chromatography-electron capture detection (ECD)/thermionic specific detection (TSD), is desirable in environmental analysis. Six solid-phase microextraction fibres available for analysis of semi-volatiles (7, 30 and 100 microm poly(dimethylsiloxane) (PDMS), 85 microm polyacrylate, 60 microm PDMS-divinylbenzene (PDMS-DVB) and 65 microm Carbowax-DVB) were evaluated and the 60 microm PDMS-DVB was selected for the simultaneous extraction of 34 compounds, included in the organochlorine (OCPs), organophosphorous (OPPs), pyrethroid and triazine pesticide groups. All parameters affecting the extraction efficiency from water samples, namely fibre coating, sample agitation, pH and ionic strength, extraction temperature and time, were optimised. The analytical procedure involves solid-phase microextraction extraction, gas chromatographic separation and subsequent ECD and TSD via a post-column splitter adjusted to a split ratio of 1:10, respectively. Detection limits in the range of 1-10 ng l(-1) for OCPs, 1-30 ng l(-1) for OPPs, 20-30 ng l(-1) for pyrethroids and 8-50 ng l(-1) for triazines are easily attainable with the optimised procedure. The method validated for ground and drinking waters has low cost of implementation and operation although it requires careful maintenance.

Persistence of selected pesticides and their phenolic transformation products in natural waters using off-line liquid solid extraction followed by liquid chromatographic techniques

The degradation of three organophosphorus pesticides with phenolic type structure (fenitrothion, ethyl-parathion, methylparathion) and pentachlorophenol in natural waters from Porto (Portugal) was studied. Three different types of natural waters (river water, estuarine water and ground water) were spiked with ethyl-parathion, methyl-parathion, fenitrothion and pentachlorophenol at 40 μg/l level and were exposed outdoor to ambient sunlight and temperature in natural conditions at the Faculty of Pharmacy of Porto during a period up to 7 weeks. Water samples were placed in 1 1 Pyrex flasks, properly closed. The samples were exposed day and night at these conditions during May and June 1996, the outside temperature being 22 °C with 5.5 h of sunlight exposition per day on average during the period studied. In order to monitor the degradation process, 100 ml of water was preconcentrated periodically by means of liquid solid extraction (LSE) using the polymeric sorbent Lichrolut EN from Merck (Darmstadt, Germany) and the extract was determined by liquid chromatography with diode array detection (LC-DAD). The use of LC coupled with mass spectrometry detection (LC-APcI-MS) permitted the unequivocal identification of various degradation products (4-nitrophenol, 3-methyl-4-nitrophenol, paraoxon ethyl, paroxon methyl, fenitrooxon and S-methylisomer of fenitrothion). Half-life for methyl-parathion was of 3 days in ground water and 4 days in both estuarine and river water; half-life for ethyl-parathion was of 2 days in ground and estuarine water and 3 days in river water; values of 1 day and less than 2 h were obtained for fenitrothion and pentachlorophenol, respectively, in all types of water. All transformation products resulted to be more stable than parent compounds except in ground water conditions. Half-lives of 5 and 4 days were calculated for 4-nitrophenol and paraoxon ethyl, respectively, in estuarine and river water. Values of 3 and 4 days were obtained for 3-methyl-4-nitrophenol in estuarine and river water, respectively.

Comparison of three different poly(dimethylsiloxane)–divinylbenzene fibres for the analysis of pesticide multiresidues in water samples: structure and efficiency

Despite the continuing development of SPME (solid-phase microextraction) fibre coatings, their selection presents some difficulties for analysts in choosing the appropriate fibre for a certain application. There are two distinct types of SPME coatings available commercially. The most widely used are poly(dimethylsiloxane) (PDMS) and poly(acrylate) (PA). Supelco has developed new mixed phases consisting of porous polymer particles, either poly(divinylbenzene) (DVB) or Carboxen suspended in a matrix of PDMS or Carbowax for extracting analytes via adsorption. In addition to the nature of the extracting phase, the thickness of the polymeric film must be taken into account and, surprisingly, the construction of the fibres when apparently they bear the same coating, as it is the case of the three PDMS-DVB fibres available. Other fibre structure properties not well explored were identified and must be taken into consideration. To elucidate their extraction efficiency, three PDMS-DVB fibres, namely 60 microm for HPLC use, 65 microm for GC use and 65 microm StableFlex for GC use, were compared with regard to the extraction of 36 compounds included in four pesticide groups. The first was particularly suited for the extraction of organophosphorus pesticides and triazines whereas the StableFlex exhibited advantages in the analysis of organochlorine pesticides and pyrethroids. An explanation for the extraction differences is suggested based on the different structure of the fibres. Detection limits in the range of 1-10 ng/l for organochlorine pesticides, 1-30 ng/l for organophosphorus pesticides, 8-50 ng/l for triazines and 10-20 ng/l for pyrethroids were attained in a method using the 60 microm PDMS-DVB fibre. The fibre maintains its performance at well above 100 extractions with between-day precision below 10%.

Optimisation of a headspace-solid-phase micro-extraction method for simultaneous determination of organometallic compounds of mercury, lead and tin in water by gas chromatography-tandem mass spectrometry.

In this work, a headspace-solid-phase micro-extraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) method for multielemental speciation of organometallic compounds of mercury, lead and tin in water samples was upgraded by the introduction of tandem mass spectrometry (MS/MS) as detection technique. The analytical method is based on the ethylation with NaBEt(4) and simultaneous headspace-solid-phase micro-extraction of the derivative compounds followed by GC-MS/MS analysis. The main experimental parameters influencing the extraction efficiency such as derivatisation time, extraction time and extraction temperature were optimized. The overall optimum extraction conditions were the following: a 50 microm/30 microm divinyl-benzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) SPME fibre, 150 min derivatisation time, 15 min extraction time, sample agitation at 250 rpm and 40 degrees C extraction temperature. The analytical characteristics of the HS-SPME method combined with GC-MS and GC-MS/MS were evaluated. The combination of both techniques HS-SPME and GC-MS/MS allowed to attain lower limits of detection (4-33 ng l(-1)) than those obtained by HS-SPME-GC-MS (17-45 ng l(-1)). The proposed method presented good linear regression coefficients (r(2)>0.9970) and repeatability (4.8-21.0%) for all the compounds under study. The accuracy of the method measured as the average percentage recovery of the compounds in spiked river water and seawater samples was higher than 80% for all the compounds studied, except for monobutyltin in the river water sample. A study of the uncertainty associated with the analytical results was also carried out.

Characterization of organic pollutants in industrial effluents using liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

Contaminated industrial effluents often contain a variety of organic pollutants which are difficult to analyse by standard GC-MS methods since this technique often misses the more polar or non-volatile fraction of these organic compounds. In the present work a method for the characterization of complex mixtures of organic contaminants present in various industrial effluents is proposed. The protocol consists of setting-up a methodology based on solid phase extraction (SPE) using an Automated Sample Preparation with Extraction Columns system (ASPEC XL) and Lichrolut EN sorbent material for preconcentrating 300-500 ml of water volumes spiked with a variety of pollutants: phenolic compounds, benzophenone, isothiocyanate-cyclohexane, ethylbenzoate, 1 -methyl-2-pyrrolidinone, 2-methylbenzenesulphonamide, benzidines, acridine, 1,1,3,3-tetramethyl-2-thiourea, 2,2-dimethyl-1,3-propanediol, phosphates, phthalates and non-ionic detergents characterized by LC-MS using atmospheric pressure chemical ionization in the positive and negative ion modes. The developed protocol permitted unequivocal identification of target analytes such as pentachlorophenol, tributyl pbosphate, 4-nonylphenol, dibutylphthalate, dimethylphthalate, bis(2-ethylhexyl)phthalate, isothiocyanate-cydohexane, ethylbenzoate, 2-methylbenzene-sulphonamide, tetramethyl-thiourea, 2,2-dimethyl-1,3-propanediol and 1-methyl-2-pyrrolidinone at concentration levels varying from 0.16 to 54.4 μg l -1 .

Simultaneous analysis of 23 priority volatile compounds in water by solid-phase microextraction–gas chromatography–mass spectrometry and estimation of the method's uncertainty

Most water contaminations with volatile organic compounds (VOCs) are traceable to leaking underground fuel reservoirs, solvent storage vessels, agricultural practices, industrial residues, and deficient wastewater treatment and disposal. In order to perform effective monitoring of such organic micropollutants in a straightforward manner, a multiresidue method for the determination of 23 VOCs (trihalomethanes (THMs), BTEX and chlorinated solvents) in water has been developed using solid-phase microextraction (SPME) and capillary gas chromatography–mass spectrometry (GC–MS). This group includes also methyl-tert-butyl ether, epichlorhydrine, and vinyl chloride which present additional analytical difficulties. Three different fibres were assayed: 7-µm polydimethylsiloxane (PDMS), 100-µm PDMS, and 75-µm Carboxen-PDMS, and the extraction conditions were optimized. The best results for the majority of the analytes and mainly for those with the lowest signals were obtained using the Carboxen-PDMS fibre after 15 min of extraction in the headspace mode at a room temperature of 20 ± 2°C. The analytical sensitivity, linearity, precision, accuracy, and uncertainties have been studied for method validation in agreement with the international standard ISO/IEC 17025:2005. The limits of detection achieved with the proposed method (0.06–0.17 µg L−1) are adequate to determine the VOCs at the restrictive levels established by the European legislation. This was a decisive achievement to enable the analysis of all VOCs listed under the drinking-water directive in a single assay. The method exhibits performance capabilities suitable for routine analysis of VOCs in drinking-water by quality-control laboratories as enforced by EU Directives. The method is currently being used for this purpose, and participation in proficiency tests was assessed, with encouraging results.

Identification of carbofuran and methiocarb and their transformation products in estuarine waters by on-line solid phase extraction liquid chromatography-mass spectrometry

Abstract The degradation of the carbamate insecticides carbofuran and methiocarb in distilled and natural waters was determined. Degradation studies were carried out both under a xenon arc irradiation and natural sunlight at pesticide concentrations of 50–100 μg/L. 50–100 mL water sample were preconcentrated using automated online solid phase extraction (SPE) followed by liquid chromatography (LC), UV detection or post column fluorescence detection (EPA method 531.1 for carbamate insecticides). Structure identification was carried out by on-line SPE-LC-MS either with thermospray and/or high flow pneumatically assisted electrospray interfaces. Half-lives varying between 4–12.5 days for carbofuran and methiocarb were determined under natural sunlight exposure, being chemical hydrolysis the major degradation pathway. When using xenon arc lamp irradiation both pesticides degraded very rapidly with half-lives varying from 0.3–1.7 hours. The various degradation products identified were: methiocarb sulfoxide, 4-...

Evaluation of the phototransformation of the antiviral zanamivir in surface waters through identification of transformation products

The antiviral zanamivir has been recently reported to occur in surface waters where its presence may lead to the selection of resistant strains of virus in aquatic fauna. In order to evaluate the fate of zanamivir in surface waters, its susceptibility to phototransformation was evaluated using simulated and natural sunlight. Upon exposure of aqueous solutions (20μgL(-1)) to simulated sunlight, zanamivir in surface water degraded at t1/23.6h. Under natural sunlight in surface water about 30% of the initial concentration of the antiviral disappeared within 18 days. The experiments with surface water showed similar effect as humic acid addition with expected decreasing effect on degradation while nitrate addition showed increasing effect. In the experiments with artificial sunlight at high concentrations of zanamivir, four photoproducts were tentatively identified by hydrophilic interaction chromatography-LTQ-Orbitrap-MS, showing [M+H](+) ions at m/z 112 (TP111), m/z 275 (TP274), m/z 323 (TP322), and m/z 333 (TP332). However at 20μgL(-1) only the formation of the recalcitrant TP111 was observed. The proposed structures were rationalized by photolysis mechanisms. Photoproduct TP111 was confirmed with a commercially available standard (isocytosine). In summary, the findings suggest that the photodegradation of zanamivir in surface waters proceeds with slow kinetics.

Analysis of acidic, basic and neutral pharmaceuticals in river waters: clean-up by 1°, 2° amino anion exchange and enrichment using an hydrophilic adsorbent

A fast and sensitive LC-MS/MS method suitable to monitor a set of 24 pharmaceuticals belonging to 9 therapeutical families was developed using an analytical column of reduced dimensions and an appropriate SPE procedure for acidic, basic and neutral analytes. Furthermore, a preliminary assessment of the occurrence and levels of these substances in surface waters of the Leça and Douro rivers, located in the north of Portugal, was conducted. Among 17 different SPE adsorbents tested, some of them often neglected, the JTBaker H2Ophilic provided the best recoveries (average 86%). When compared to the amino and quaternary ammonium adsorbents, the 1°, 2° amino proved the most suitable clean-up media for surface water samples prior to enrichment by SPE. The overall method provided limits of detection generally below 5 ng L−1 and a precision below or around 10% RSD in three non-consecutive days at 500 ng L−1 and around 12% at 50 ng L−1 concentration levels. The confirmatory capabilities of the method developed are especially welcome either through the MS3 spectra or the isotopic pattern. The first known results regarding the occurrence of pharmaceuticals in Leça river confirmed its expected high contamination load and the successful selection of the target pharmaceuticals. Concentrations up to 770 ng L−1 of bezafibrate, 925 ng L−1 of paracetamol, 389 ng L−1 of hydrochlorothiazide and 283 ng L−1 of furosemide were measured. The most ubiquitous in both seasons, February and June 2009, were bisoprolol, furosemide, bezafibrate and gemfibrozil. In Douro river the abundance and contamination level of pharmaceuticals was much lower which gives a clear indication that the hydraulic features of the river provide enough attenuation of the several contamination sources whereas Leça is highly impacted by insufficiently treated anthropogenic effluents.

Chapter 9:Green Analytical Chemistry in the Determination of Organic Pollutants in the Environment

This chapter gives an overview of different strategies used in green analytical chemistry for analysing organic pollutants in the environment. Although green analytical chemistry is not a new approach for environmental analysis, the present chapter presents innovations that have been achieved recently. The chapter also discusses analytical techniques that have not been covered in previous publications; these include the use of green solvents for sample preparation, recent developments for chromatographic separations, improvements in greening the interfaces for mass spectrometric analysis and biological techniques for sample preparation and detection. Some examples using green analytical techniques for the determination of organic pollutants in the environment are presented.