Luis Piedra

Toxicity evaluation of single and mixed antifouling biocides measured with acute toxicity bioassays

Antifouling biocides used in boat paints were analyzed with a battery of toxicity bioassays to evaluate the toxic effects of these compounds on Vibrio fischeri, Daphnia magnaand Selenastrum capricornotum.The antifoulants tested were Irgarol 1051, Kathon 5287, chlorothalonil, diuron, dichlofluanid, 2-thiocyanomethylthiobenzothiazole (TCMTB) and tributyltin (TBT). In most cases, the sensitivity of the organisms towards the toxicants followed the order: S. capricornotum> D. magna> V. fischeri. Toxicity by concentration level had the following order: TBT = Kathon 5287 > chlorothalonil > Irgarol 1051 > diuron > dichlofluanid > TCMTB for S. capricornotum .F orD. magna(48 h test), the toxicity order of compounds was TBT > Kathon 5287 > chlorothalonil > TCMTB > dichlofluanid > Irgarol 1051 > diuron. For V. fischeri (30 min test), the compound toxicity had the following order: Kathon 5287 > TBT > TCMTB > dichlofluanid > Irgarol 1051 > chlorothalonil. Degradation products of Irgarol 1051 and diuron were also tested. Degradation product of Irgarol 1051 was found to be less toxic to the crustacean and the microalga but more toxic to the bacterium. Degradation products of diuron were less toxic to the microalga in comparison with the bacterium. For mixtures of compound, toxicities were additive in only 33% of the cases and 21% of mixtures were less toxic than expected based on the sum of concentrations of toxicants (antagonistic effect). Synergistic enhancements of toxicity were observed for a majority (46%) of the mixtures. The average reproducibility of the EC50 and LOEC measurements was 27, 24 and 28%, respectively, in the V. fischeri, S. capricornotum and D. magna bioassays. For single compound, the reproducibility of EC50 was better than ±20% for a vast majority of the measurements with the V. fischeri system, thus agreeing closely with the reported reproducibility values for this relatively well-known assay.

Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyser

A selective and sensitive chromatographic method is described for the determination of nine organochlorine and organophosphorus pesticides in vegetable samples by gas chromatography-mass spectrometry. The proposed method combines the use of positive and negative chemical ionisation and tandem mass spectrometric fragmentation, resulting in a significant increase in selectivity and allowing the simultaneous confirmation and quantification of trace levels of pesticides in complex vegetable matrices. Parameters relative to ionisation and fragmentation processes were optimised to obtain maximum sensitivity. Repeatability and reproducibility studies yielded relative standard deviations lower than 25% in all cases. Identification criteria, such as retention time and relative abundance of characteristic product ions, were also evaluated in order to guarantee the correct identification of the target compounds. The method was applied to real vegetable samples to demonstrate its use in routine analysis.

Splitless large-volume GC-MS injection for the analysis of organophosphorus and organochlorine pesticides in vegetables using a miniaturised ethyl acetate extraction

A simple, rapid and sensitive multiresidue method has been developed for the determination of ten organophosphorus and organochlorine pesticides, commonly used in crop protection. The analysis uses a miniaturised extraction with ethyl acetate followed by large volume injection (10 microL) GC-EI-MS analysis in SIM (selective ion monitoring) mode. Sensitivity and selectivity of the method were acceptable with limits of detection (LODs) lower than 0.01 mg kg-1, except for endosulfan alpha and beta (0.05 mg kg-1). Average recoveries of between 63-99% were obtained and good linearity was observed in the range from 0.01 to 1.00 mg kg-1. Repeatability and reproducibility studies yielded relative standard deviations lower than 20% in all the cases. The method was applied to the analysis of 110 tomato, pepper and cucumber samples, as part of the monitoring programme of the Association of Producers and Exporters of Fruits and Vegetables of Almería.

Determination of traces of five antifouling agents in water by gas chromatography with positive/negative chemical ionisation and tandem mass spectrometric detection.

A highly selective and sensitive gas chromatography-mass spectrometry methodology has been developed for the determination of five antifouling compounds, currently licensed for use in marine antifouling paints. The procedure uses an ion trap mass spectrometer provided with an external ion source that allows the combined use, in the same analysis, of positive (PCI) and negative (NCI) chemical ionisation and tandem mass spectrometric fragmentation (MS-MS). Ionisation and fragmentation processes were optimised individually for each compound, thus, permitting maximum sensitivity and selectivity to be obtained. A complete validation study, including those aspects that affect both correct quantification and unequivocal confirmation, demonstrated the good performance of the proposed method. Detection limits obtained were lower than 0.005 microg l(-1), except for Irgarol 1051 (0.050 microg l(-1)). The method was applied to real seawater samples from different

Multiresidue method for the analysis of five antifouling agents in marine and coastal waters by gas chromatography–mass spectrometry with large-volume injection

A simple multiresidue method has been developed for the determination of five pesticides, commonly used as active ingredients in antifouling paints, in seawater samples. The pesticides studied were: chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile), dichlofluanid (N-dimethyl-N-phenylsulphamide), Sea-Nine 211 (4,5-dichloro-2-n-octyl-4-isothazolin-3-one), Irgarol 1051 (2-methylthio-4-tert.-butylamino-6-cyclopropylamino-s-triazine) and TCMTB (2-thiocyanomethylthiobenzothiazole). The analytes were extracted from 200 ml water samples, using solid-phase extraction. A copolymer with hydrophilic-lipophilic balance was used as sorbent yielding good recoveries (82-95%) for most compounds except dichlofluanid and Sea-Nine 211 (<60%). Large volume injection (10 microl) gas chromatography and electron impact ionization MS (selected ion monitoring mode) detection enabled these compounds to be identified and quantified at the 1.2-3.0 ng/l level. Analysis of samples performed in three marinas in Almería (Spain) revealed the presence of Irgarol 1051 in all the cases, at concentration levels between 25 and 450 ng/l.

Screening of Antifouling Pesticides in Sea Water Samples at Low ppt Levels by GC-MS and LC-MS

SummaryStudies of various analytical procedures for simultaneous determination of antifouling pesticides in sea water, based on SPE followed by GC-MS and LC-MS, have been made. The main characteristics of these compounds in GC-MS in both positive and negative modes and in LC-ES-MS were studied. Extraction of the compounds from filtered water was performed off-line with different SPE adsorbents using graphitized carbon (Envi-carb) and polymer cartridges (Isolute ENV+ and Oasis HLB) by passing 600 mL samples through them. Detection was carried out following selected analytical procedures (GC-MS in El and NCI modes) and LC-ES-MS (positive mode). Recoveries ranged from 80–95% except for dichlofluanid and Sea-nine 211 where they were 40 and 46%. In spite of this, the low coefficients of variation (<11%) obtained, were low enough to consider these recoveries adequately. Limits of detection were at low part-per-trillon levels in all cases. Finally, a six-month pilot study was carried out at various marinas in the South-East of Spain. Irgarol 1051 and diuron were revealed as the major antifouling agents in this area at concentrations up to 0.9 and 0.8 µg L−1 respectively.

Determination of methyl tert.-butyl ether and tert.-butyl alcohol in seawater samples using purge-and-trap enrichment coupled to gas chromatography with atomic emission and mass spectrometric detection.

A rapid and simple analytical method has been established for the determination of methyl tert.-butyl ether (MTBE) and tert.-butyl alcohol (TBA), in seawater. The method involves purge-and-trap enrichment followed by gas chromatographic (GC) determination. Two different detection systems have been compared: atomic emission detection (AED) and MS (selected ion monitoring mode). Validation parameters and possible matrix effects have been evaluated. The linearity and analytical precision was good with both methods, but limits of detection reached by AED (10 microg l(-1)) were not low enough to evaluate current environmental concentrations. GC-MS detection presented much better sensitivity [limits of detection (LODs) of 0.04 microg l(-1) for MTBE and 0.09 microg l(-1) for TBA] and selectivity, providing a more reliable determination. The analysis of samples collected from various marinas in the south of Spain (Almería and Málaga) showed, in all cases, detectable concentrations of MTBE that ranged from below LOD to 1842 microg l(-1), depending on the sampling point and time. TBA was also detected in some cases, with concentration levels that ranged from 400 to 600 microg l(-1). These preliminary results should be followed by monitoring programs in coastal waters, in order to establish real levels of presence of MTBE in our coasts and its possible effect on the marine environment.

Toxicity of Single and Mixed Contaminants in Seawater Measured with Acute Toxicity Bioassays

Different types of organic pollutants commonly detected in seawater have been evaluated by acute toxicity bioassays. Vibrio fischeri, Daphnia magna, and Selenastrum capricornotum were selected to test toxic effects of individual compounds and mixtures of these compounds, obtaining EC50 values in the range of 0.001 to 28.9 mg/l. In the case of mixtures, synergistic toxic responses were seen for a clear majority of the cases (>60%). Mixtures containing methyl-tertiary-butyl ether (MTBE) exhibit accelerated processes that result in a change in concentration required to produce a toxic effect; for example, in the case of mixtures containing MTBE and Diuron and Dichlofluanid.

Chromatography-mass spectrometry and toxicity evaluation of selected contaminants in seawater

SummaryIn the present work a combined analytical study involving gas and liquid-chromatography and toxicity studies were developed for the determination of various contaminants typically present in sea water samples. The compounds investigated were Diuron, Chlorothalonil, Dichlofluanid, TCMTB (2-thiocyanomethylthiobenzothiazole), lrgarol 1051, Sea nine 211 and MTBE (methyl-tert-butyl ether). The selected compounds are additives of boat paints and gasoline and they can release into the aquatic environment in considerable amounts in areas with intense shipping traffic. The developed analytical protocol consisted on the use of a solid phase extraction procedure with Oasis™ HLB cartridges followed by GC-El/NCI-MS and LC-ES-MS both in SIM mode. Average recoveries, loading 600 mL of samples with pH=3, varied from 40 to 95% and the detection limits ranged from 1–25 ng L−1. The developed method was applied to real samples from various marinas of Andalusia (Spain).Daphnia magna, Vibrio fischeri andSelenastrum capricornotum toxicity bioassays on individual and mixtures of selected compounds were applied to evaluate EC50 (effective concentration) and LOEC (lowest observable effect concentration) values. Resulting values were in the range of 0.001–720 mg L−1 for EC50 and 0.8.10−9–30 mg L−1 for LOEC for all contaminants except for MTBE where no toxic effect were found up to 680 mg L−1 onDaphnia magna. Toxicity effects of binary mixtures of the selected compounds showed synergistic effects in the majority of the cases (47.6%) and antagonistic in the lower of the cases (9.5%). Levels of the contaminants found in the seawater samples showed around a 30% of inhibition on tested species, during the summer months considering mixture lrgarol 1051-Diuron. Accelerated toxicity processes were observed in mixtures MTBE-Diuron and MTBE-Dichlofluanid.