Effects of sample pretreatment and storage conditions in the determination of pyrethroids in water samples by solid-phase microextraction and gas chromatography–mass spectrometry

Factors controlling the fate of pyrethroids residues during post-harvest processing of raw agricultural crops: An overview

Control of residual levels of synthetic pyrethroids in fresh fruits and vegetables as well as in foodstuff made of fresh agricultural produces is of utmost importance. Apart from the need to more control on application of pesticides by farmers, simple and effective postharvest practices by consumers and/or manufacturers usually applied to produces before consumption may enhance food safety from potentially harmful pesticide residues. The present review discusses the underline factors that control the effectiveness of crops postharvest treatments and the possible mechanisms of loss of pesticides during food processing. It is shown that the effectiveness of postharvest processes is controlled by various factors and that understanding such factors is essential for more control of residual pesticides. Though postharvest processes may lead to substantial reduction of residual pesticides, metabolites of broken pesticides are of great concern.

Stabilisation of groundwater samples for the quantification of organic trace pollutants

The concentration of contaminants in groundwater samples can be decreased by degradation in the time course between field sampling and quantification in the laboratory, especially in samples from sites where degradation activity is enhanced by remediation measures. The sampling sites covered a variety of priority organic pollutants such as volatile aromatic and chlorinated compounds, phenols and petroleum hydrocarbons and different remediation strategies such as anaerobic and aerobic microbial in situ degradation, in situ chemical oxidation, and on-site purification with biological treatment. The stability of the contaminants' concentration was investigated over a time range of several hours without cooling in the autosampler of the analytical equipment (short term) and over several days of storage until analysis (long term). A number of stabilisation techniques suggested in international standards ISO 5667-3:2013 and ASTM D6517:2000 were compared both with regard to short term and long term stabilisation of the contaminants and their practicability for field sampling campaigns. Long term storage turned out to be problematic for most compound groups even under cooling. Short term stability was problematic also for volatiles such as benzenic aromates, naphthalene and volatile organic halogenated compounds to be analysed by headspace gas chromatography. Acidification (pH <2) was sufficient to prevent degradation of benzenic aromates, naphthalene, phenols and petrol hydrocarbons for up to seven days. The use of acids was not applicable to stabilise volatiles in waters rich in carbonates and sulphides due to stripping of the volatiles with the liberated gases. The addition of sodium azide was successfully used for stabilisation of volatile organic halogenated compounds.

Occurrence and behavior of pesticides in wastewater treatment plants and their environmental impact

Reports on pesticides elimination during wastewater treatment are rare since these substances are typically considered of agricultural rather than of urban origin. In this context, the aim of this work was to evaluate the presence, removal and environmental relevance of 22 selected pesticides in three different wastewater treatment plants (WWTPs), paying attention not only to their occurrence and elimination but also to the toxicity of each pesticide against three aquatic micro organisms (algae, daphnia and fish) through the calculation of the so-named Environmental Relevance of Pesticides from Wastewater treatment plants Index (ERPWI). For this purpose, an analytical method based on isotope dilution on-line solid phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) was optimized, allowing the determination of the 22 target pesticides in wastewater with satisfactory sensitivity (limits of detection below 30 ng/L), accuracy and precision. Concerning the results, total pesticide levels were in most instances below 1 μg/L but removal in the WWTPs was variable and often poor, with concentrations in the effluent sometimes higher than in the corresponding influent. Possible explanations for these poor or negative removal rates are, among many others considered (e.g. sampling, sample preservation, method biases, atmospheric deposition), deconjugation of metabolites and/or transformation products of the pesticides, hydrolysis, and desorption from particulate matter during wastewater treatment. The most significant pesticides in terms of concentration and frequency of detection were diazinon and diuron. These two pesticides, followed by atrazine, simazine and malathion, were also the most relevant from the environmental point of view, according to the calculated ERPWI.

An overview of sample preparation and extraction of synthetic pyrethroids from water, sediment and soil

The latest developments in sample preparation and extraction of synthetic pyrethroids from environmental matrices viz., water, sediment and soil were reviewed. Though the synthetic pyrethroids were launched in 1970s, to the best of authors' knowledge there was no review on this subject until date. The present status and recent advances made during the last 10 years in sample preparation including conservation and extraction techniques used in determination of synthetic pyrethroids in water, sediment and soil were discussed. Pre- and post-extraction treatments, sample stability during extraction and its influence upon the whole process of analytical determination were covered. Relative merits and demerits including the green aspects of extraction were evaluated. The current trends and future prospects were also addressed.

Time-dependent integrity during storage of natural surface water samples for the trace analysis of pharmaceutical products, feminizing hormones and pesticides

Monitoring and analysis of trace contaminants such as pharmaceuticals and pesticides require the preservation of the samples before they can be quantified using the appropriate analytical methods. Our objective is to determine the sample shelf life to insure proper quantification of ultratrace contaminants. To this end, we tested the stability of a variety of pharmaceutical products including caffeine, natural steroids, and selected pesticides under refrigerated storage conditions. The analysis was performed using multi-residue methods using an on-line solid-phase extraction combined with liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) in the selected reaction monitoring mode. After 21 days of storage, no significant difference in the recoveries was observed compared to day 0 for pharmaceutical products, while for pesticides, significant losses occurred for DIA and simazine after 10 days (14% and 17% reduction respectively) and a statistically significant decrease in the recovery was noted for cyanazine (78% disappearance). However, the estrogen and progestogen steroids were unstable during storage. The disappearance rates obtained after 21 days of storage vary from 63 to 72% for the feminizing hormones. Overall, pharmaceuticals and pesticides seem to be stable for refrigerated storage for up to about 10 days (except cyanazine) and steroidal hormones can be quite sensitive to degradation and should not be stored for more than a few days.

Investigation of the photochemical behaviour of pyrethroids lacking the cyclopropane ring by photo-solid-phase microextraction and gas chromatography/mass spectrometry

The characterization of by-products arising from the UV photodegradation of two insecticide pyrethroids lacking the cyclopropane ring (flucythrinate and fenvalerate) has been investigated by gas chromatography coupled with mass spectrometry (GC/MS). Twenty photoproducts were tentatively identified mainly based on the interpretation of the experimental mass spectra or by using reference mass spectra. Some of these compounds had not previously been detected. Furthermore, the generation of some of the photoproducts might be a matter for concern due to their potential toxicity. The corresponding photodegradation routes, including postulation of the intermediate radicals, have also been proposed. These photodegradation studies were performed by photo-solid-phase microextraction (photo-SPME) in which the SPME fibre was exposed to light after extraction of the target analytes from aqueous solutions. The degradation kinetics of the investigated pyrethroids and the photoformation-photodegradation curves of the photoproducts generated in situ were also monitored through the ion chromatograms obtained for different irradiation times and the corresponding mass spectra.

Development of a high-throughput method for the determination of organochlorinated compounds, nitromusks and pyrethroid insecticides in indoor dust

Investigation of chemical exposure inside the homes and offices where people spend the majority of their lives has only recently begun. These chemicals are degraded much more slowly than outdoor because they are more protected from sunlight, severe environmental conditions and microbial activity. Hence, indoor dust has been recognized as an important exposure pathway for organic contaminants. Pyrethroids are synthetic insecticides widely used in domestic environment for numerous applications and also in agriculture. Chlorobenzenes are a family of compounds used as intermediates in the production of a wide range of household consumer products. Nitromusks are a kind of synthetic musks used in the production of cleaning agents, detergents, and personal care products. A high-throughput method for the determination of these compounds in indoor dust samples has been developed. Microwave-assisted solvent extraction was used as the extraction technique whereas quantification of compounds was carried out by gas chromatography with micro-electron-capture detection. Several cleanup procedures were tested and finally a non-classical "on batch" procedure was selected, which allows increasing the throughput of the analysis while decreasing sample manipulation. Extraction conditions were optimized using a multifactorial experimental design approach. Quantitative recovery (84-103%) was achieved for all compounds and method precision was satisfactory. Limits of detection ranged from 0.22 ng g(-1) for lindane to 40 ng g(-1) for 1,4-dichlorobenzene. Standard reference material SRM 2585 was analyzed and the obtained values were in good agreement with the reported reference values for organochlorinated compounds and nitromusks. Pyrethroids and polychlorobenzenes have been analyzed for the first time in this reference material and some of them have been found. In addition, real samples collected in houses of north-western Spain have been analyzed by the proposed method and 17 of the 22 target compounds have been detected in the samples.