Roberto Alzaga

Development of a supercritical fluid extraction procedure for tributyltin determination in sediments

The effect of extraction variables, such as extraction time, temperature and extraction agent composition (X), in supercritical fluid extraction (SFE) and tributylin (TBT) from a spiked sediment, has been optimized by using a factorial-fractional experimental design. Under the optimum conditions (T = 60°C, P = 35 MPa, X = 5.1 M methanol in CO2, t = 30 min) the TBT extraction efficiency was 82% with a coefficient of variation (C.V.) of 9.2% (n = 5). Furthermore, the analytical procedure was validated using a reference material (RM) certified for its TBT content and was successfully applied to the analysis of a Certified Reference Material (CRM). Furthermore, an intercomparison of the SFE with another extraction procedure based on atmospheric pressure liquid extraction (APE) for the TBT determination in sediments has been carried out. Although TBT recoveries were significantly higher in the SFE procedure, the precision of both methods was comparable, probably associated to similar steps in the extract treatment procedure (derivatization and clean up).

Determination of linear alkylbenzensulfonates in aqueous matrices by ion-pair solid-phase microextraction–in-port derivatization–gas chromatography–mass spectrometry

Trace determination (low ng/ml) of linear alkylbenzensulfonates (LASs) in water was achieved by solid-phase microextraction (SPME) of ion-pairs formed with tetrabutylammonium. This ion-pairing reagent served two purposes. First, it allowed the extraction of LAS with the polydimethylsiloxane fiber by counterion association and second, the derivatization of the formed LAS ion pairs in the GC injection port at 300 degrees C to form the corresponding sulfonated butyl esters. The methodology developed allows the isomer specific determination of LAS at low detection limits (0.16-0.8 ng/ml), depending on the alkyl chain lengths of LASs with RSDs of 10-12%. Furthermore, the developed methodology was applied to urban wastewater and sea water and compared with a solid-phase extraction (SPE) method (e.g. C18 and strong anion-exchange sorbent) to obtain concordant values for urban wastewater. Moreover, the developed SPME methodology overcame the procedural blank and matrix-dependent recoveries found in the SPE methodologies at low LAS concentrations.

Physico-chemical characterisation of atmospheric aerosols in a rural area affected by the aznalcollar toxic spill, south-west Spain during the soil reclamation activities

High levels of atmospheric contamination due to the re-suspension of pyrite particles from the mining waste slurry were recorded in the Guadiamar valley (the Guadiamar is a tributary of the Guadalquivir river) after the toxic spill of Aznalcóllar, north of the Doñana Natural Park (SW Spain). Major high-particulate events occurred during the extraction of the pyrite-rich mud layer, which covered an extensive area of the valley downstream of the confluence of the Agrio and Guadiamar rivers. This study deals with the monitoring of the ambient air quality at two stations near the village of Aznalcázar in the central part of the flooded area. Although the Spanish legal limit for atmospheric particles and lead in environmental air were not exceeded, high daily levels of total suspended particles (TSP) and of some elements with an environmental significance (As, Cd, Cu, Mn, Ni, Pb, Sn, Tl and Zn) were recorded at Aznalcázar and in the Guadiamar valley during soil reclamation (July-August 1998). Despite a progressive decrease in TSP levels through September-October 1998, background was higher than the levels for the May-June period. Evolution of levels for most of the elements studied showed a similar trend. The exceptions were copper, which was partially increased by other emission sources such as fumigation activities, and sodium, which remained at relatively constant levels during the study period because of its marine origin. The physico-chemical characterisation of the atmospheric particulates allowed us to determine the major grain size modes of the pyrite related elements and the solubility of the potentially toxic elements, and to identify the major particulate types present in the atmosphere in the area. Secondary and tertiary aromatic amines (i.e. alkyldiphenylamines and phenylcarbazoles, respectively) were identified in the suspended particles and in the vapour phase collected at the same station as the TSP samples. As some of these aromatic amines had been previously identified in the pyrite sludge, it is assumed that fine sludge particles containing aromatic amines were re-suspended in the atmosphere. The highest concentrations of aromatic amines in the particulate phase were recorded in August 1998 during the pyrite slurry extraction in the proximity of the Aznalcázar sampling site. Despite a sharp drop in the suspended particles of the aromatic amine concentrations, a significant concentration was detected in the vapour phase (< 1.2 mm) during autumn, probably because of longer residence time in the atmosphere. Although health hazards associated with the presence of these aromatic amines are unknown, their acute toxicity exceeded that of urban aerosols.

Comparison of supercritical fluid extraction and liquid-liquid extraction for isolation of selected pesticides stored in freeze-dried water samples

SummaryThe stability of freeze-dried water samples spiked with eight agrochemicals (atrazine, simazine, linuron, carbaryl, propanil, fenitrothion, parathion and fenamiphos) were examined to evaluate their suitability as candidate reference materials for their determination in water samples. In addition, two different extraction procedures, liquid-liquid and supercritical fluid extraction, were compared for the isolation and trace enrichment of target analytes from freeze-dried water samples. Final analytical determinations were by gas chromatography-nitrogen phosphorus detection and electronic impact mass spectrometry, and by liquid chromatography-diode array detection. The whole methodology developed in this paper permitted the determination of pesticides spiked in water at levels varying from 0.03 to 6.9 μg L−1.

Determination of Organic Contaminants in Landfill Leachates: A Review

Leachates derived from landfills constitute a potential risk of groundwater pollution because a variety of contaminants can be released by leaking from the contention system. Therefore, the leachate composition is of interest of their appropriate management. Although the leachate characterisation is usually carried out by global parameters (i.e. DOC, BOD, COD, AOX, etc), its characterisation at molecular level is of increasing interest and will be reviewed in the present article. Sample handling and determination techniques for a variety of organic contaminants is discussed and pitfalls as well as limitations of each analytical technique will be highlighted.

Characterization of organic compounds in soil and water affected by pyrite tailing spillage

Abstract A variety of mono- and di-chlorinated and brominated triphenylamines were identified in the sludge and contaminated soils affected by a toxic waste spill that occurred in the Los Frailes pyrite mine (SW Spain). A negative gradient of aromatic amine concentrations from 29 μg g−1 in the vicinity of the broken dam to 0.14 μg g−1 in contaminated soils collected 30 km to the south in the Guadiamar River valley was observed. Substituted carbazoles (e.g. 9-phenylcarbazole) were also identified as contaminating sludge, soils and the temporarily dammed water at Entremuros and the Guadalquivir River and its tributary, the Guadiamar River. Our results demonstrate that contaminated waters from the pyrite sludge spill reached the Guadalquivir Estuary. However, the more lipophilic compounds, such as the halogenated triphenylamines, were not recorded in water bodies because of their strong adsorption by soils during the weathering process. Conversely, the more hydrophilic benzothiazoles were widespread in surface waters, a finding attributable to their higher solubility than chlorinated aromatic amines. Although the source of the nitrogen organic compounds (NOCs) has not yet been identified, it would seem to be related to the pyrite tail spillage. For example, degradation of technical products used in ore processing or industrial waste dumped in the mine waste collection dam could be the source of these compounds. Given the widespread occurrence of 9-phenylcarbazole in the affected area, this compound is proposed as a specific molecular marker of the Aznalcollar spill. Furthermore, some of the NOCs were identified in the contaminated waters of the Guadiamar and Guadalquivir Rivers, providing evidence that these rivers were affected by the mining spill. Taking into account the field concentrations (water, sludge) and the spill volume, it can be concluded that the budget of aromatic amines is in the range of 27 t — of this, 32.6% was in the aqueous phase and the remaining 67.4% was in the soil.

Intercomparison among SFE, ASE, Soxhlet and sonication for the trialkylamine determination in sediment and sludge

Abstract Accelerated solvent extraction (ASE) and supercritical fluid extraction (SFE) have been compared to Soxhlet and sonication extraction procedures for the determination of long-chain trialkylamines (CH3NR1R2 where R1 and R2 = C14H29 C16H33 or C18H37) in sediment and sludge. An hybrid experimental design was applied for the first time to the optimization of temperature and modifier composition for the SFE of incurred trialkylamines from marine sediment and primary sewage sludge. SFE at 50°C and 30 MPa with CO2 modified dynamically with MeOH and statically with triethylamine yielded concentrations of incurred TAMs 10-77% higher than Soxhlet or sonication (3 extractions) with dichloromethane-methanol mixture (2:1). However, the ASE technique with the same extraction mixture at 150°C and 17 MPa showed the highest extraction efficiency among the extraction methods evaluated. The precision improvement in SFE was attributed to the direct analysis of extracts by GC-NPD without any cleanup step whereas Soxh...

New approach on the alkylthiol determination in water by in situ derivatization SPME followed by GC-ECD/NPD analysis

Alkylthiols are very reactive and highly volatile compounds, and thus it is difficult to determine these in the water phase. In the present work, an in situ derivatization step prior to solid-phase microextraction (SPME) has been developed for their determination in water samples. The dinitrobenzylation reaction was selected because the high chemical stability of the corresponding thioethers formed provides a significant increase in the distribution coefficient between the SPME fibre and the aqueous phase, and a potential increase in the selectivity and sensitivity. Therefore, different derivatization reaction conditions (i.e. pH, temperature, reaction time and derivatizating reagent concentration) have been studied. Then, the main parameters affecting to the SPME process, that is coating selection, extraction time profile, extraction and desorption temperatures, have been optimized. Finally, a method based on a simple 2,4-dinitrophenylation reaction at pH 8–10, in 60 min at 75°C, coupled to direct SPME using PDMS-DVB fibres at 30°C for 45 min is proposed. The performance of the method provided a good linearity and precision data, and the detection limits were in the low ng L−1 level.

DETERMINATION OF ORGANOCHLORINE COMPOUNDS IN NEUSTON FROM THE MEDITERRANEAN

Abstract A reliable analytical procedure was developed to determine trace levels of organochlorine compounds in neuston samples. Freeze‐dried samples were extracted by sonication (3 × 15 ml cyclohexane, 15 min) followed by gel permeation chromatography (GPC) and gas chromatography electron capture detection (GC‐ECD) determination. Neuston samples may present great differences in their lipid content, which may become a drawback for the analytical determination of hydrophobic pollutants. In this way, GPC fractionation combined with Florisil® cleanup was successfully used to avoid potential lipidic interferences in the GC‐ECD determination. Organochlorine compounds were determined by GC‐ECD and a standard addition method was performed to evaluate the recoveries of 41 PCB individual congeners (80±20%). The congeners with lower Kow (octanal water partition coeeficient) values showed lower recoveries (54 ± 7%) than the more lipophylic ones (80 ± 7%). The limits of detection ranged from 0.001 to 0.211 ng g−1 of wet samples. The reproducibility of the developed analytical methodology for independent replicates (n = 3) at low pg g−1 levels was quite satisfactory (RSD 18 + 10%).