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Dynamic headspace-thermal desorption/gas chromatography-mass spectrometry was employed to characterize the volatile profile of extra virgin olive oils before and after the process of sedimentation plus racking. Several oils produced in the provinces of Ourense (San Cibrao das Viñas) and Lugo (Quiroga) (northwestern Spain) and in that of Córdoba (southwestern Spain) were selected for such a purpose. There are no data on the effect of racking on the headspace composition of EVOOs. The volatile components were identified, and the differences found were highlighted in terms of the process but also in terms of different varieties and origins. The results suggest that besides the genetic factor, environmental conditions and process treatments influence the volatile formation. After racking, there is an increase of fruity vs. green notes (C6 alcohols vs. C6 aldehydes) and an apple-like character vs. a banana-like nuance (C6 linoleic acid route vs. C6 linolenic acid route) but also a more bitter character (C5 vs. C6 volatiles), with whiskey, spicy and malty nuances (by the slight increase of minor alcohols and aldehydes). [ABSTRACT FROM AUTHOR]

This article discusses the adsorption behavior of several PAHs to colloid dispersion of humic substances in water. According to the authors, PAHs are a concern because they can cause cancers in humans and are harmful to fish and other aquatic life. They concluded that the key factors controlling the distribution of PAHs and their stability-persistence and possible bioavailability in the natural aqueous environments, were the hydrophobicity and the water solubility of PAHs. Adsorption of the different PAHs to humic substances can be modeled in terms of both of these factors.

No abstract available. [ABSTRACT FROM AUTHOR]

The European Union specificies that drinking water can contain pesticide residues at concentrations of up to 0.1 μg/L each and 0.5 μg/L in total, and that 1–3 μg/L of pesticides can be present in surface water, but the general idea is to keep discharges, emissions and losses of priority hazardous substances close to zero for synthetic substances. Therefore, in order to monitor pesticide levels in water, analytical methods with low quantification limits are required. The method proposed here is based on solid phase extraction (SPE) followed by gas chromatography with a nitrogen–phosphorous detector (GC-NPD). During method development, six organophosphate pesticides (azinphos-ethyl, chlorfenvinphos, chlorpyriphos, ethoprophos, fenamiphos and malathion) and two organonitrogen pesticides (alachlor and deltamethrin) were considered as target analytes. Elution conditions that could influence the efficiency of the SPE were studied. The optimized methodology exhibited good linearity, with determination coefficients of better than 0.996. The analytical recovery for the target analytes ranged from 70 to 100%, while the within-day precision was 4.0–11.5 %. The data also showed that the nature of the aqueous matrice (ultrapure, surface or drinking water) had no significant effect on the recovery. The quantification limits for the analytes were found to be 0.01–0.13 μg/L (except for deltamethrin, which was 1.0 μg/L). The present methodology is easy, rapid and gives better sensitivity than solvent drop microextraction for the determination of organonitrogen and organophosphate pesticides in drinking water at levels associated with the legislation. [ABSTRACT FROM AUTHOR]

This article discusses a study which elucidated the dynamics of atrazine sorption and desorption in acid-surface soils obtained from the plough layer of corn fields in Galicia, Spain. Organic carbon, nitrogen and sulphur contents were examined. Atrazine adsorption by the soils was found to decrease with increasing hydrogen-ion concentration. Copper slightly increased atrazine adsorption. Meanwhile, zinc slightly reduced atrazine adsorption. The adsorption of copper and zinc was severely reduced by the presence of atrazine in the soils.

A simple and sensitive HPLC method was developed for the determination of colistin antibiotic in feeds employing pre-column derivatization and fluorescence detection. Extraction of colistin in feeds was by sonication and shaking with 0.1 M HCl. Pre-column derivatization was with phthaldialdehyde and 2-mercaptoethanol (ME) in borate buffer (pH 10.5) to obtain a fluorescent derivative. Elution of the derivative onto an Ultracarb 5 μm ODS column was by using acetonitrile—ultrapure water (75∶25). Detection was by spectrofluorimetry at 340 nm (excitation wavelength) and 440 nm (emission wavelength). Total elution time was <20 min. The applicability of the validated method was tested by analyzing commercial medicated feeds without any interference from the matrix. [ABSTRACT FROM AUTHOR]

EU Directive 90/128/EEC prescribes a specific migration limit (SML) of 0.05 mg kg−1 for the aliphatic diamine m-xylylenediamine (XDA) into food or food simulants, but there is no generally accepted method of analysis available for testing compliance with this restriction. m-XDA has been determined in olive oil (EU food simulant for fatty foods) by high-performance liquid chromatography (HPLC) with fluorescence detection, after extraction into an aqueous phase and derivatization with fluorescamine. The method is appropriate for the quantitative determination of m-XDA at a minimum level of 0.02 mg kg−1 in this food simulant. The method should also be applicable to other fatty-food simulants (sunflower oil and HB 307). [ABSTRACT FROM AUTHOR]

A simple, rapid and inexpensive method has been developed for the determination of vitamins riboflavin (B2) and pyridoxine (B6) in beverages with added vitamins, and validated by checking the precision from those samples, and calibration and detection levels from proper standards. The method involves direct injection of the beverage into an HPLC. B2 vitamin is also analysed by second derivative, synchronous spectrofluorimetry. The precision of the method obtained with samples is satisfactory (RSD<2.5%). Detection and quantification limits obtained with standards were 0.02 and 0.06 mg L−1 for B2, and 0.12 and 0.36 for B6, respectively, which indicates that these vitamines can be monitored by this method in all kind of vitaminised beverages. [ABSTRACT FROM AUTHOR]

Colistin (COL) and tiamulin (TML) are antibiotics used in veterinary practice. Diseases in animals are usually treated by adding the drug (liquid and/or solid medicated premix) to animal feed. Two simple, inexpensive, and rapid methods have been developed for quantification of COL and TML in liquid and solid medicated premixes by HPLC with diode-array detection, on the basis of scanning in the UV range 200–380 nm. The wavelengths 206 and 208 nm were used for quantification of COL and TML, respectively. The total elution time was less than 15 min. When the applicability of the optimized method was tested by analysis of commercial feed premixes there was no interference from the matrix. [ABSTRACT FROM AUTHOR]