Z. Gomez de Balugera

Solid-phase microextraction for the determination of systemic and non-volatile pesticides in river water using gas chromatography with nitrogen-phosphorous and electron-capture detection.

A solid-phase microextraction (SPME) method combined with gas chromatography with nitrogen-phosphorous and electron capture detection for the analysis of the pesticides terbumeton, metribuzine, isomethiozine, pyridafenthion and triadimenol in river water has been developed. For this purpose, polyacrylate and polydimethylsiloxane coated fibres have been utilised and the factors affecting throughput, precision and accuracy of the SPME method have been investigated and optimised. These factors include: matrix influence, adsorption time, pH, salt effect, desorption time, temperature and also the lapse of time between sampling and injection. The performed analytical procedure showed detectability ranging from 2.0 ng l(-1) to 3.0 microg l(-1) and precision from 1.9 to 27.7% (as relative standard deviation) depending on the pesticide, the fibre and the detector used. The results demonstrate the suitability of the SPME method to analyse these non-volatile pesticides in river water.

Speciation of Volatile Aromatic and Chlorinated Hydrocarbons in an Urban Atmosphere Using TCT-GC/MS

Abstract Several aromatic and chlorinated volatile hydrocarbons (VOCs) were measured in Vitoria-Gasteiz City (Spain) throughout the years 1999 and 2002 in order to find out the concentration of these pollutants in urban air. These VOCs were retained in Tenax TA, subsequently desorpted by using a thermal desorption cold trap injector (TCT), and thereafter analyzed by gas chromatography/mass spectrometry (GC/MS). This analytical methodology permits the determination of 42 VOCs at very low concentrations, although only 32 of them were found in the urban air of the city (ranging from 205.51 to 0.01 μg m−3), with high reproducibility (%RSD lower than 10%). Twenty-four-hour samples were taken each sampling day to ascertain their total daily concentration, and rigorous quality controls were carried out to check the representativeness of sampling. Results of this exhaustive study show that toluene (T), xylenes (X), ethylbenzene (E), and benzene (B) were, respectively, the most abundant of these VOCs in the urban area during that period. The total concentration of BTEX represented, on average, more than 72.6% of the VOC total concentration, with the highest concentrations being reached in autumn, except for benzene and derived compounds (in winter). Benzene was the minority BTEX pollutant, its yearly mean concentration being less than the maximum established by the European Directive 2000/69/CE (5 μg m−3).

Determination of herbicides by reductive amperometric detection in liquid chromatography

A liquid chromatographic method has been developed for the determination of the herbicides metamitron, metribuzin, isometiozin and nitralin in soil samples. Reductive amperometric detection using a hanging mercury drop electrode has been selected because of the selectivity of the technique. The separation has been performed in a Spherisorb CN, 5 μm (250x4.0 mm) column. A mobile phase consisting of acetonitrile-phosphate buffer (32:68, v/v) pH 2.5 was used with the detector operated in direct current mode at E=-1350 mV. The analysis time was 9 min. The mean relative standard deviations (R.S.D.) of the results were <4%. Conditions for extraction of herbicides from soil samples have been established. The method allows the determination of 3.4, 2.9, 12.1 and 6.9 ng g of metamitron, metribuzin, isometiozin and nitralin in soil, respectively.

Determination of simazine and cymoxanil in soils by microwave-assisted solvent extraction and HPLC with reductive amperometrical detection

SummaryA microwave-assisted extraction (MAE) method was optimized for the herbicide simazine and the fungicide cymoxanil in soil samples. The experimental variables that affect MAE, such as temperature, extraction time and solvent volume, were studied. It was concluded that these pesticides could be efficiently extracted from soil samples in a microwave oven with 10 mL of acetonitrile at 90°C for 5 min The analysis of extracts has been carried out by high performance liquid chromatography with amperometric reductive detection (HPLC-ED). The detector, equipped with a hanging mercury drop electrode (HMDE), operated in direct current mode at −1.2 V vs Ag/AgCl, when a mobile phase consisting of phosphate buffer-acetonitrile (95:5, v/v) was used. The procedure developed involving MAE and HPLC-ED provided detectability in soil samples of 30 μg Kg−1, acceptable recoveries (range 82.3–100.3%) and RSDs of lower than 5% for cymoxanil and simazine.

Study of the toxicity in industrial soils by the bioluminescence assay

Abstract A survey of the toxicity of soils from the several industrial zones of the Spanish Basque Country was undertaken in order to identify the relationship between chemical contamination and toxicity. The measured effect in the solid and liquid‐phase Microtox toxicity test was correlated with the chemical parameters to determine the origin of the toxicity effect. Results indicate the higher sensitivity of solid‐phase bioassay. In a comparative study with the liquid‐phase assay it was found that due to different solubility of each contaminant in water the test on the extracts represents only a part of multiple contamination. Moreover water elutriation could underestimate the types and concentrations of organic contaminants present.

Determination of 4-Chloroaniline and 4-Chlorophehyl Urea in Honey By Liquid Chromatography with Electrochemical Detection

Abstract A liquid chromatographic technique with amperometric detection was developed for determining diflubenzuron metabolites, 4-chlorophenyl urea and 4-chloroaniline, using a Spherisorb C18 column 5μm (4.1 × 250 mm). A mobile phase of acetonitrile / citrate-disodium hydrogenphosphate buffer, 30:70, at pH=7.0, was pumped at a flow rate of 1 mL min−1. The amperometric detector, equipped with a glassy carbon working electrode was operated at 1100 mV vs Ag/AgCl. The method showed a limit of detection of 0.46 μg 1−1 for 4-chlorophenyl urea and 0.20 μg 1−1for 4-chloroaniline. Reproducibility in terms of relative standard deviation ranged between 1.24 and 4.50 % for the 4-chlorophenyl urea and 1.60 and 3.93% for the 4-chloroaniline. The method was applied to the determination of both metabolites in honey. The prior extraction of the two substances from honey was established using different solid-liquid extraction phases.

HPLC/Diode-Array Method for the Determination of the Pesticide Diflubenzuron and Its Major Metabolites 2,6-Difluorobenzamide, 4-Chlorophenylurea, and 4-Chloroaniline in Forestry Matrices

Abstract A method using liquid chromatography with diode-array detection, LC-DAD, has been developed for the determination of the pesticide diflubenzuron and some of its major metabolites, such as 2,6-difluorobenzamide, 4-chlorophenylurea, and 4-chloroaniline in pine-needles. Samples were extracted into acetonitrile and further cleaned-up through aminopropyl cartridge. LC was performed on a C18 column using acetonitrile-methanol-water (50:2:48) as mobile phase at 1 mL min−1 at room temperature.

Determination of Nematicide Aldicarb and Its Metabolites Aldicarb Sulfoxide and Aldicarb Sulfone in Soils and Potatoes by Liquid Chromatography With Photodiode Array Detection

Abstract Solid phase extraction has been combined with High Perfomance Liquid Chromatography using a Photodiode Array Detector to isolate, determine, quantify and recover trace concentrations of aldicarb and its toxic metabolites, aldicarb sulfoxide and aldicarb sulfone, in soils and potatoes. A method is proposed which eliminates matrix interferences. The procedure involved extracting with acetonitrile or dichloromethane, initial separation and clean-up with a Sep-Pack Florisil or Silica cartridges. The extract can be successfully analyzed by HPLC-DAD and recoveries for pesticides were not influence by the use of this extraction method. The results have been applied to the systematic study of these compounds in growns of patatoes. The lowest detectable concentration for each pesticide is 40 μg kg−1 in soil and 15 μg kg−1 in potatoes.