Field performance of the Chemcatcher passive sampler for monitoring hydrophobic organic pollutants in surface water.

Six field trials were carried out to assess the performance of the Chemcatcher passive sampler alongside spot sampling for monitoring priority hydrophobic organic pollutants (polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides) in a wide range of conditions in surface water. The trials were performed in three European rivers: Elbe (Czech Republic), Alna (Norway) and Meuse (Netherlands), in two seasons (April-June 2004, and September-October 2004). Samplers spiked with performance reference compounds (PRCs) were deployed for either 14 or 28 days. Ten spot samples of water were collected over the course of the trial and filtered through a 0.7 microm glass fibre filter. Concentrations of pollutants measured using the Chemcatcher were compared with the average concentrations found in spot samples. This study describes the operational performance of Chemcatcher for measuring hydrophobic (log K(OW) 3.7-6.8) chemicals in surface water. Site specific Chemcatcher sampling rates up to 0.5 L d(-1) were found using the PRC approach that reduced the uncertainty in estimates of sampling kinetics where temperature, local flow conditions and biofouling potential varied between sites and seasons, and with time during sampler exposure. The limits of quantification of sampled analytes ranged from one to tens ng L(-1). Highest sensitivity was achieved for compounds with a favourable combination of low instrument quantification limits and high sampling rates including dieldrin, hexachlorobenzene, lindane, pentachlorobenzene, and PAHs with less than five aromatic rings. The direct comparison of time weighted average (TWA) concentrations (mostly close to method limits of detection) obtained using passive and spot sampling was possible for lindane, hexachlorobenzene, and PAHs < 4 rings. Implications of using the Chemcatcher in regulatory monitoring programmes such as the European Union Water Framework Directive are discussed.

Can Occurrence of Pesticide Metabolites Detected in Crops Provide the Evidence on Illegal Practices in Organic Farming?

Modern pesticides rapidly degrade after their application due to both physicochemical factors and through biotransformation. Consequently, pesticide residues in samples might be either undetectable or detected at low concentrations (≤10 µg/kg). Under such conditions, a monitoring of pesticide metabolites in samples might be a conceivable solution enabling the documentation of earlier pesticide use. Analysis of metabolites might pose analytical challenges because pesticide degradation leads to the production of a number of metabolites, differing somewhat in their structure and polarity. This study was focused on the determination of pesticide residues and their metabolites in samples of grapevine and wine using ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry, with the objective of supporting the possibility of the verification of the method of farming. It documents the identification of pesticide metabolites commonly used in conventional farming and provides a characterization of pesticide degradation during grapevine growth, maturation, and during the wine-making process.

Food fraud in oregano: Pesticide residues as adulteration markers.

Oregano, a widely used and popular herb, is particularly vulnerable to fraud. Less valued plants, adulterants that are often used for dilution, may introduce into this commodity additional contaminants such as pesticide residues. In this study, more than 400 pesticides were screened in a representative set of 42 genuine and 34 adulterated dried oregano samples collected from various locations across Europe. The results obtained by advanced mass spectrometry-based methods, showed, that some pesticide residues could be detected in virtually all tested samples, nevertheless, on average, higher contamination was found in the adulterated oregano samples. Increased incidence of insecticides such as cyfluthrin, permethrin and cyhalothrin was typical for these samples, moreover, pyriproxyfen was detected exclusively in adulterated samples. Thus, based on a critical assessment of pesticide profiles, suspected adulterated oregano samples can be selected for follow up authenticity testing.

Evaluation of pesticide residue dynamics in Chinese cabbage, head cabbage and cauliflower.

Pesticide residues from the time of application until harvest were analysed for 20, 17 and 18 active insecticidal and fungicidal substances in Chinese cabbage, head cabbage and cauliflower, respectively. In total, 40 mathematical models of residue degradation were developed using a first-order kinetic equation, and from these models it was possible to forecast the action pre-harvest interval for a given action threshold for low-residue production in Brassica vegetables as a percentage of the maximum residue level. Additionally, it was possible to establish an action pre-harvest interval based on an action threshold of 0.01 mg kg‒1 for the production of Brassica vegetables for baby food. Among the evaluated commodities, the speed of residue degradation was highest in head cabbage, medium in Chinese cabbage and lowest in cauliflower. The half-lives of pesticide in various vegetables were also determined: they ranged from 1.55 to 5.25 days in Chinese cabbage, from 0.47 to 6.54 days in head cabbage and from 1.88 to 7.22 days in cauliflower.