Esther Rodríguez

Coupling solid-phase microextraction and high-performance liquid chromatography for direct and sensitive determination of halogenated fungicides in wine

A solid-phase microextraction (SPME) method coupled to high-performance liquid chromatography with diode array detection (HPLC-DAD) for the analysis of six organochlorine fungicides (nuarimol, triadimenol, triadimefon, folpet, vinclozolin and penconazole) in wine was developed. For this purpose, polydimethylsiloxane-divinylbenzene-coated fibers were utilized and all factors affecting throughput, precision, and accuracy of the SPME method were investigated and optimized. These factors include: matrix influence, extraction and desorption time, percentage of ethanol, pH, salt effect and desorption mode. The performed analytical procedure showed detectability ranging from 4 to 27 microg l(-1) and precision from 2.4 to 14.2% (as intra-day relative standard deviation, RSD) and 4.7-25.7% (as inter-day RSD) depending on the fungicide. The results demonstrate the suitability of the SPME-HPLC-DAD method to analyze these organochlorine fungicides in red wine.

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 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.

Photo-Assisted Oxidation of Indigocarmine in an Acid Medium

The kinetics of photo-oxidation of indigocarmine dye—5,5-indigosulfonate disodium (5,5-IDS)—in an acid medium has been studied to discover the effect of different parameters in the efficiency of the process. The experiments were conducted applying ultraviolet (UV)-polychromatic radiation to oxygen-saturated solutions. All kinetic experiments showed that the dye reaction order was zero, and its initial concentration did not influence the experimental rate constant. An increase in the rate was observed with an increasing UV radiation dose (Duv) and/or the acidity. Temperatures—ranging from 290 K to 320 K—did not significantly affect the rate constant, indicating the photochemical activation of the oxidative process. 5-Isatinesulfonate sodium (5-IS) was identified as a photo-oxidation product. The effluent of the phototreatment had no color and contained no toxic products. Results showed that UV-induced oxidation of 5,5-IDS dye in an oxygensaturated aqueous medium, at room temperature, is an alternative trea...

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.

Persistence of Diflubenzuron on Conifer Forest Foliage in a Mediterranean-Climate Ecosystem Following Aerial Application

Dimilin 45 ODC (diflubenzuron) was applied in a Mediterranean-climate conifer forest, near Vitoria, Basque Country, Spain. Pine needles were collected at post-treatment 5-day intervals for analysis of the diflubenzuron residues. A liquid chromatography method with on-line diode-array and electrochemical detection was developed for the determination of the pesticide diflubenzuron and its main metabolites: 2,6-diflurobenzamide, 4-chlorophenylurea, 4-chloroacetanilide, 4-chloroaniline and N-methyl-4-chloroaniline in forestry matrices. Aerial application at 56.3 g AI ha−1 resulted in deposition levels of the insecticide of 1080 ng g−1. Within 40-65 days following treatment, 51-73% of the insecticide had been removed from the foliage. During this period, the concentration of diflubenzuron was higher than 295 ng g−1. The only metabolite detected was 2,6-difluorobenzamide and this persisted on foliage until the first rainfalls occurred. An empirical mathematical correlation was found to express the influence of rainfall, solar radiation and temperature on the persistence of the insecticide.

Multisorbent tubes sampling used in thermal desorption cold trap injection with gas chromatography-mass spectrometry for C2–C6 hydrocarbon measurements in an urban atmosphere

Three solid adsorbents (Carbotrap, Carbotrap C, and Carbosieve III) were evaluated for sampling trace non-methane hydrocarbons in urban atmospheres. The sampled atmosphere was pumped through a multisorbent tube containing the three sorbents separated by a small amount of silanized glass wool. The trapped compounds were recovered by thermal desorption and analysed by combining cryogenic enrichment with gas chromatography and mass spectrometry. Adsorption/thermal desorption and breakthrough experiments were performed to test their ability to quantitatively trap the light hydrocarbons. The technique was suitable for determination of low ppbv concentrations of these compounds. Ambient atmospheric sampling was conducted in Vitoria-Gasteiz (Basque Country, Spain), and the measurements cover a period of one year (2001–2002). Fifteen C2–C6 hydrocarbons are identified and quantified, and seasonal trends are discussed.