European Union Maximum Residue Limits Research Articles

High Throughput Analytical Techniques for the Determination and Confirmation of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea by GC/MS, GC/MS/MS, and LC/MS/MS: Collaborative Study, First Action 2014.09.

Thirty laboratories from fom North and South America, Europe, and Asia participated in this AOAC collaborative study (15 from China; five from Germany; two each from Italy and the United States; and one each from the Republic of Korea, Canada, Spain, Japan, Belgium, and India). Participants represented government regulatory, commercial testing, university, research institute, and private laboratories. The single-laboratory validated (SLV) tea method was evaluated in the collaborative study to determine the recovery and reproducibility of the method under multilaboratory conditions. Since there were no restrictions regarding the type of analytical instrumentation to use for the analyses, laboratories used a combination of equipment that included GC/MS, GC/MS/MS, and LC/MS/MS instruments from 22 different manufacturers, 21 brands of GC and LC columns, 13 different GC temperature programming profiles, 11 LC gradient elution programs, and six different vendor manufactured SPE cartridges. Even though all the analytical performance parameters for all the 653 compounds had been determined in the SLV study, guidance was obtained from an expert review panel of the AOAC Method-Centric Committee on Pesticide Residues to conduct the multilaboratory collaborative study based on 20 selected compounds that can be analyzed by GC/MS and 20 compounds that can be analyzed by LC/MS/MS. Altogether, 560 samples covering the 40 selected pesticides were analyzed in the study. These samples included green tea and oolong tea samples fortified typically at the European Union maximum residue limit for regulatory guidance and compliance, aged tea samples incurred with 20 pesticides, and green tea and oolong tea samples incurred with five pesticides. The analysis of the 560 samples generated a total of 82 459 test results by the 30 participating laboratories. One laboratory failed to meet the proficiency requirements in the precollaborative study. Therefore, its data submitted for the collaborative study were excluded from further analysis and interpretation. The results presented are therefore the 6638 analytical results obtained from the 29 remaining laboratories, which included 1977 results generated by GC/MS, 1704 results by GC/MS/MS, and 2957 results by LC/MS/MS. It was determined after application of the Grubbs and Dixon tests for outliers to the data sets that there were 65 outlier results from the 1977 GC/MS results (3.3%), 65 outlier results from the 1704 GC/MS/MS results (3.8%), and 57 outlier results out of 2957 LC/MS/MS results (1.9%), representing 0.98, 0.98, and 0.86%, respectively, of the 6638 results generated in the study. Analysis with the AOAC statistical software package also confirmed that the method is rugged, and average recovery, average concentration, RSDr, RSDR, and HorRat values all meet recovery and reproducibility criteria for use in multiple laboratories. The Study Director is recommending this method for adoption as an AOAC First Action Official MethodSM.

Pesticide contamination of produce and medicinal plants in Suriname: An emerging environmental health threat

Background: Pesticides are used widely in Suriname, an upper middle-income country, in large and small-scale agriculture and family gardens. The levels of imported pesticides in 2013 include 73,144.77 kg of insecticides, 447390.80 kg of fungicides and 277,234.00 kg of herbicides. While import is regulated, no policies exist regarding distribution and sale. National monitoring of pesticide residues in produce is absent; however, data from the Netherlands (2011-2013) on imported produce from Suriname show that approximately 20% of samples confirmed pesticide residues above the European Union Maximum Residue Limits. The Caribbean Consortium for Research in Environmental and Occupational Health is designed to address high-priority environmental and occupational health risks in Suriname. Among the consortium’s key studies is examining the public health implications of agricultural pesticides use. Methods: The study is being conducted in three phases. Phases 1 and 2 entail the environmental characterization; pesticide residue analysis of mostly consumed crops and medicinal plants cultivated or harvested in Suriname in the 2 main seasons. Phase 1 consists of a preliminary characterization; analysis of the biota collected in the rainy season from the largest fresh market of Suriname, district Paramaribo. In Phase 2 the environmental characterization is expanded with spatial sampling in the dry season and with an additional pesticide test panel. Sampling is conducted at the largest fresh market of district Paramaribo as well as district Wanica; the 2 most densely populated districts. Additionally, the most popular produce item Tannia is sampled at 3 other fresh markets in district Paramaribo. Phase 3 focuses on human health assessment including a comprehensive dietary assessment to conduct a risk factor analysis and biomarker testing to ascertain organ system function impact. Findings: In Phase 1, 32 insecticides (e.g. lambdacyhalotrin) and 12 fungicides (e.g. carbendazim) were tested on 7 crops (tannia, cabbage, long beans, peppers, rice, sweet potatoes, and banana) and 1 medicinal plant (Phyllanthus amarus). Tannia had levels of Endosulfan that exceeds the MRLs of the EU. Endosulfan is an insecticide that is prohibited in Suriname and is being phased out globally. Phase 1 results are only based on collection of crops from 1 fresh market in only 1 season. Also, the Surinamese population consumes not solely locally cultivated crops. However, this study is the first to characterize pesticide contaminated produce and to conduct the future human health assessment. Interpretation: The results indicate that pesticide residue levels may pose a threat to human health. Produce samples are currently being analyzed using an expanded pesticide panel including other organophosphates, herbicides and fungicides. The findings will be available and will be presented at the upcoming conference. Funding: Funding is provided by the Fogarty International Center of the National Institutes of Health. Abstract #: 02SEDH001

Persistence of bifenthrin in tea and its transfer from black tea to tea brew

Field experiments were conducted at two places in Tamil Nadu (India) to determine the residues of bifenthrin in black tea. Residues were quantified at different harvest intervals of ‘0’ (3 hr), 1 st , 3 rd , 5 th , 7 th , 10 th and 14 th day after acaricide application. Persistence, dissipation pattern, half-life value and safe harvest interval of the acaricide in tea were calculated. Residues of bifenthrin dissipated exponentially after application at both the locations and reached below the European Union maximum residue limit (MRL) of 5 mg kg-1 on the 10th day. Bifenthrin showed that like other acaricides it followed the first order dissipation kinetics. Half-life values varied from 2.4 to 3.2 days for bifenthrin and a safe harvest interval of 10 days is suggested for tea at the recommended dosage.

Investigation of enrofloxacin and chloramphenicol residues in broiler chickens carcasses collected from local markets of tabriz, northwestern iran.

The present study was aimed to determine the residual amounts of chloramphenicol and enrofloxacin in broiler chickens muscle and liver sam-ples gathered from local markets of Tabriz City, northwestern Iran. Ninety broiler chickens carcasses were collected from different local markets of Tabriz, during July/August 2013. Random samples of thigh and breast muscle and liver were gathered and kept at -80(°)C until analyzes. The samples were then assayed using enzyme-linked immunosorbent assay (ELISA) according to the protocol of each antibiotic kit. Data were statistically analyzed using the computer program SAS 9.1. Eighty two samples (91/1 %) contained residues of enrofloxacin, alt-hough mean (±SD)of enrofloxacin concentration was lower than the European Union maximum residue limits(MRLs) value (P<0.001). Moreover, 28 (31/1 %) had detectable concentrations of chloramphenicol while it was not defined any MRLs value for chloramphenicol because its using has been forbidden in food animals. The frequency of contamination with enrofloxacin was considerable for the analyzed samples. Furthermore, the existence of chloramphenicol in almost one third of samples seems to be a public health threat due to its illegal use in food animals including poultry.

Monitoring and Risk Assessment of Pesticide Residues in Tea Samples from China

ABSTRACTIn the present study an effort was made to monitor the residue levels of 32 pesticides in tea samples collected from three representative tea districts of China during 2010 to 2012. A total of 223 samples of green tea, pu-erh tea, black tea, and oolong tea were determined using gas chromatography with mass spectrometry (GC-MS). Among 223 samples, 198 samples contained pesticide residues, and 39 samples had residue levels that were more than the European Union (EU) maximum residue limits (MRLs). The most positive and violated MLRs were observed in Oolong tea. The highest detection rates and the most often exceeding the MRLs were observed for the residues of bifenthrin. Ten pesticides were not found in the 223 tea samples. The potential health risks to consumers due to tea consumption in three representative cities were estimated. The results suggested that non-cancer hazards of organophosphorus, organochlorines, and pyrethroids and the cancer risks from exposure to hexachlorobenzene, heptachlor, chlordane, and pp’-DDT were clearly below the safe limit. Nevertheless, an investigation into continuous monitoring and tighter regulation of pesticide residues in tea samples are almost always desirable or even necessary for public health protection.

Development of a monoclonal antibody-based immunochromatographic strip for cephalexin

An anti-cephalexin (CEX) monoclonal antibody was prepared by the immunogen of CEX-keyhole limpet hemocyanin connected by disuccinimidyl suberate, which was used for the establishment of a rapid immunochromatographic test strip. With this semi-quantitative detection method, a low limit of deduction of 10 ng mL−1 was obtained with the naked eyes and 1.3 ± 0.1 ng mL−1 by a strip reader in unprocessed milk within 5 min, which was much lower than the European Union Maximum Residue Limit of 100 µg kg−1 in milk. The recovery in the range of 87–120% was measured in another milk sample. In conclusion, this method with high sensitivity and satisfactory recovery shows significant potential for CEX residue detection in milk.

Dietary Intake of Pesticides Based on Vegetable Consumption in Ismailia, Egypt: A Case Study

ABSTRACT The objective of this study was to assess pesticide residues in tomatoes, cucumbers, peppers, strawberries, and potatoes collected from local markets in Ismailia, Egypt, and to assess dietary intake and health risk implications of pesticide residues through food consumption. Vegetable selection was based on their popularity and consumption. Selection of pesticides was based on their impact on humans, and on their heavy use. The majority of the analyzed samples contained detectable levels of pesticides. Residues of some organophosphorus pesticides, including malathion, ethion, and profenofos and some pyrethroid pesticides such as fenpropathrin and cypermethrin were found in some samples at concentration equal to or exceeding their European Union's maximum residue limits (EU-MRLs). The fungicide bupirimate detected in potato samples exceeded the EU-MRL by 1500%. Phentohate and profenofos were the most frequently detected pesticides in 30 and 27% of analyzed samples, respectively. Data were used to estimate the potential health risks associated with exposure to these pesticides by ingestion of food. Estimated daily intakes (EDIs) of pesticides ranged from 0.03% to 40% of the acceptable daily intakes (ADIs), depending on pesticide concentration and vegetable consumption. Overall, the EDIs of the different pesticides from vegetable consumption are not considered a public health problem.

Bioefficacy, residue dynamics and safety assessment of the combination fungicide trifloxystrobin 25% + tebuconazole 50%-75 WG in managing early blight of tomato (Lycopersicon esculentum Mill.)

This paper reports the in vitro and in vivo bioefficacy of a combination fungicide trifloxystrobin (25%) + tebuconazole (50%) against early blight disease of tomato (Lycopersicon esculentum Mill.) caused by Alternaria solani and their corresponding pre-harvest intervals (PHI) with reference to the maximum residue limits (European Union). Bioefficacy of the test fungicide combination revealed that in vitro conditions manifested the best control (75.1%) at 350 mg kg−1 against 76.2% control under field conditions. A sample preparation method based on ethyl acetate extraction and estimation by LC-MS multiple reaction monitoring (MRM) was validated in tomato fruits at 0.01 mg/kg and dissipation studies were conducted in field at single and double doses. The residues of both the compounds on all the sampling days were below the European Union maximum residue limits (EU-MRLs) and the maximum permissible intakes (MPIs) were calculated on the basis of prescribed acceptable daily intake (ADI). The combined bioefficacy and residue dynamics information will support label-claim of this fungicide combination for the management of early blight in tomato.

Dissipation kinetics, safety evaluation, and assessment of pre-harvest interval (PHI) and processing factor for kresoxim methyl residues in grape

A field dissipation study was conducted to evaluate the pre-harvest interval (PHI) and processing factor (PF) for kresoxim methyl (Ergon 44.3 SC) residues in grapes and during raisin making process at recommended dose (RD) and double the recommended dose (DRD). Kresoxim methyl residues dissipated following 1st-order kinetics with a half-life of 10 and 18 days at RD and DRD, respectively. The PHIs with respect to the European Union maximum residue limit (EU-MRL) of 1 mg kg(-1) for grapes were 13 and 30 days at RD and DRD, respectively. The degradation data during grape to raisin making process were best fitted to nonlinear 1st + 1st-order kinetics with a half-life ranging between 4 and 8 days for both shade drying and with raisin dryer at different doses. The PFs were 1.19 and 1.24 with shade drying and 1.09 and 1.10 with raisin dryer, respectively, which indicates concentration of the residues during raisin making process. The dietary exposure of kresoxim methyl on each sampling day was less than the respective maximum permissible intake both at RD and DRD. The residues of kresoxim methyl in market samples of grapes and raisins were well below the EU-MRL and were also devoid of any risk of acute toxicity related to dietary exposure.

IDEXX SNAP® Beta-Lactam ST Validation for Penicillin G Detection

IDEXX has produced a robust and improved rapid test kit optimized to detect penicillin G in a variety of milk matrixes. The SNAP Beta-Lactam ST Test Kit is designed to be run without the use of a heat block. The new test is optimized to ensure a detection capability for penicillin G that is at or below the European Union maximum residue limit of 4 parts per billion. The test can be used with commingled cow milk, commingled goat milk, commingled sheep milk, and reconstituted whole fat powdered milk. The SNAP Beta-Lactam ST Test Kit contains all the items necessary to run and interpret the test in a single package. No heat block or reader is required. The results can be read visually or with an IDEXX SNAPshot or SNAPshot DSR Reader. The total assay time is approximately 7 minutes.

Mercury occurrence in Italian seafood from the Mediterranean Sea and possible intake scenarios of the Italian coastal population

Mercury (Hg) settlements in the Mediterranean Sea determine a potential toxicological relevance of seafood intakes for coastal populations. To assess this possibility, fish, molluscs, and crustaceans of commercial size of 69 different species were sampled and analyzed for total mercury (HgTOT) from georeferenced areas and evaluated for their compliance with the European Union Maximum Residue Limits of 0.5 and 1.0mg/kgwet weight (ww). Accounting for the weekly estimated seafood intake in the Italian coastal population (mean 469–626g/person/week) it was then possible to recover threshold contamination values in seafood. Under a Tolerable Weekly Intake of 1.3μg/kg/bw/week, a threshold seafood contamination <0.10mg/kgww has been derived for sensitive groups. A suitable algorithm based on the parallel MeHg and HgTOT analysis on the most consumed species, helped to refine the uncertainties related to the conservative assumption in seafood all the HgTOT present is in form of MeHg. This work aims to improve the link between the risk management and risk assessment strategies, with the identification of those fish and seafood species, that, when regularly consumed, could determine or prevent potential HgTOT/MeHg overintakes in sensitive groups.

Pesticides and degradation products in groundwaters from a vineyard region: Optimization of a multiresidue method based on SPE and GC-MS

A reliable multiresidue method based on solid phase extraction was developed using GC-MS to determine and quantify 34 pesticides, including herbicides, fungicides, insecticides, and some of their degradation products, in groundwater in a vineyard region of La Rioja (northern Spain). Different parameters were optimized and good recoveries (65-108% range) and precisions (12-19% range) were achieved with spiked water samples for a concentration of 0.1 μg/L. The experimental results showed an excellent linearity (r(2) > 0.99) over the 0.1-1.5 μg/L range. The detection limits of the proposed method were 1-37 ng/L for most of the compounds studied. The methodology has been successfully applied to the analysis of groundwater samples from vineyard areas in La Rioja and the presence of pesticides, especially fungicides and herbicides, at several concentration levels was revealed. Terbuthylazine, its metabolite desethyl-terbuthylazine, and fluometuron were the pesticides most frequently detected in higher concentrations. Overall and taking into consideration the European Union maximum residue limit of pesticides in groundwater, 16 of the 34 compounds included in this study were detected in concentrations over that limit in at least one of the samples analyzed.

Investigation of pesticide residues in vegetables and fruits grown in various regions of Hatay, Turkey

In this study, 175 pesticide residues in various vegetable and fruit samples grown in different regions of Hatay, Turkey, were investigated. Residue analyses were performed using liquid chromatography–tandem mass spectrometry with the QuEChERS method. In tomato, plum and apricot samples, pesticide residues were below the limits of detection. In other samples, at least one pesticide residue was detected. Twelve pesticides (acetamiprid, carbendazim, chlorpyrifos, fenarimol, fludioxonil, hexythiazox, imidacloprid, metalaxyl, pyridaben, pyriproxyfen, thiabendozole, triadimenol) were found at levels between 0.003 and 0.759 mg kg−1. Only in cucumber samples, acetamiprid residues were found at levels greater than the maximum acceptable limit in Turkish Food Codex and European Union maximum residue limits (EU MRLs). In other samples, the detected residue amounts are less than the MRLs declared in the Turkish Food Codex and EU MRLs.

Pesticide Residue Levels in Green Beans Cultivated in Souss Masa Valley (Morocco) After Multiple Applications of Bifenthrin and λ-Cyhalothrin

Dissipation of bifenthrin and λ-cyhalothrin pyrethroid insecticides, under environmental conditions, was evaluated on green beans grown in experimental greenhouses (Souss Massa valley, Morocco). Pesticide residues were determined by gas chromatography with micro electron-capture detector (GC-μECD) after dichloromethane extraction and cleanup on florisil phase cartridges. In the case of field experiments, a random block scheme was employed. Each block contained 25 plants in a single row and tests were carried out in triplicates applying pesticides at the recommended doses by the manufacturers. Fruit samples were periodically taken until the end of the preharvest interval (p.i.). The results obtained showed that the p.i of bifenthrin in green bean were 4days in the winter and 3.5days in the spring, whereas that for λ-cyhalothrin 8days was found in the winter and 7.5days in the spring. Consequently, it is possible to consider the European Union maximum residue limit (EU MRL) values compatible with the proper agricultural practices used for growing green bean in the plastic greenhouse of Souss Massa valley in South Morocco. Bifenthrin had a degradation of first-order kinetics, whereas that of levels for λ-cyhalothrin residue can not be interpreted by the use of a first order model.

Emergency slaughter of casualty cattle increases the prevalence of anthelmintic drug residues in muscle

The ProSafeBeef project studied the prevalence of residues of anthelmintic drugs used to control parasitic worms and fluke in beef cattle in Ireland. Injured (casualty) cattle may enter the human food chain under certain conditions, verified by an attending veterinarian and the livestock keeper. An analytical survey was conducted to determine if muscle from casualty cattle contained a higher prevalence of anthelmintic drug residues than healthy (full slaughter weight) cattle as a result of possible non-observance of complete drug withdrawal periods. A validated analytical method based on matrix solid-phase dispersive extraction (QuEChERS) and ultra-performance liquid chromatography–tandem mass spectrometry was used to quantify 37 anthelmintic drugs and metabolites in muscle (assay decision limits, CCα, 0.15–10.2 µg kg−1). Of 199 control samples of beef purchased in Irish shops, 7% contained detectable anthelmintic drug residues but all were compliant with European Union Maximum Residue Limits (MRL). Of 305 muscle samples from injured cattle submitted to abattoirs in Northern Ireland, 17% contained detectable residues and 2% were non-compliant (containing either residues at concentrations above the MRL or residues of a compound unlicensed for use in cattle). Closantel and ivermectin were the most common residues, but a wider range of drugs was detected in muscle of casualty cattle than in retail beef. These data suggest that specific targeting of casualty cattle for testing for anthelmintic residues may be warranted in a manner similar to the targeted testing for antimicrobial compounds often applied in European National Residues Surveillance Schemes.

Pesticide residue analysis in cereal-based baby foods using multi-walled carbon nanotubes dispersive solid-phase extraction

In the present study, a new analytical method has been developed for the simultaneous quantification of 15 organophosphorus pesticides, including some of their metabolites, (disulfoton-sulfoxide, ethoprophos, cadusafos, dimethoate, terbufos, disulfoton, chlorpyrifos-methyl, malaoxon, fenitrothion, pirimiphos-methyl, malathion, chlorpyrifos, terbufos-sulfone, disulfoton-sulfone and fensulfothion) in three different types of commercial cereal-based baby foods. Dispersive solid-phase extraction (dSPE) with multi-walled carbon nanotubes (MWCNTs) was used together with gas chromatography with nitrogen phosphorus detection. Most favorable conditions involved a previous ultrasound-assisted extraction of the sample with acetonitrile containing formic acid. After evaporation of the extract and redissolution in water, a dSPE procedure was carried out with MWCNTs. The whole method was validated in terms of repeatability, linearity, precision and accuracy and matrix effect was also evaluated. Absolute recoveries were in the range 64-105 % with relative standard deviation values below 7.6 %. Limits of quantification achieved ranged from 0.31 to 5.50 μg/kg, which were lower than the European Union maximum residue limits for pesticide residues in cereal-based baby foods.

Anthelmintic drug residues in beef: UPLC-MS/MS method validation, European retail beef survey, and associated exposure and risk assessments

Anthelmintic drugs are widely used to control parasitic infections in cattle. The ProSafeBeef project addressed the need for data on the exposure of European consumers of beef to potentially harmful drug residues. A novel analytical method based on matrix solid-phase dispersive extraction and ultra-performance liquid chromatography-tandem mass spectrometry was validated for 37 anthelmintic drugs and metabolites in muscle (assay decision limits, CCα, = 0.15–10.2 µg kg−1). Seven European countries (France, Spain, Slovenia, Ireland, Italy, Belgium and Portugal) participated in a survey of retail beef purchased in local shops. Of 1061 beef samples analysed, 26 (2.45%) contained detectable residues of anthelmintic drugs (0.2–171 µg kg−1), none above its European Union maximum residue limit (MRL) or action level. Residues detected included closantel, levamisole, doramectin, eprinomectin, moxidectin, ivermectin, albendazole and rafoxanide. In a risk assessment applied to mean residue concentrations across all samples, observed residues accounted for less than 0.1% of the MRL for each compound. An exposure assessment based on the consumption of meat at the 99th percentile of consumption of adults in 14 European countries demonstrated that beef accounted for less than 0.02% of the acceptable daily intake for each compound in each country. This study is the first of its kind to apply such a risk-based approach to an extensive multi-residue survey of veterinary drug residues in food. It has demonstrated that the risk of exposure of the European consumer to anthelmintic drug residues in beef is negligible, indicating that regulation and monitoring is having the desired effect of limiting residues to non-hazardous concentrations.

A broadly applicable approach to prepare monoclonal anti-cephalosporin antibodies for immunochemical residue determination in milk

A simple, efficient and rapid method for the synthesis of cephalosporin-protein conjugates was established. These conjugates were used as immunogens to produce monoclonal antibodies (mAbs) and as solid phase antigens in competitive indirect enzyme immunoassays (EIAs). With this generic approach, a novel set of monoclonal antibodies for cephalosporins was prepared, including ceftiofur and cephalexin as well as, reported here for the first time, cefoperazone, cefquinome and cephapirin. All 5 EIAs were highly sensitive, with standard curve IC(50) values of 0.7 (ceftiofur), 1.1 (cefquinome), 5.2 (cephalexin), 13.8 (cefoperazone) and 40.3 ng mL(-1) (cephapirin). Detection limits (IC(30)) ranged from 0.3 (ceftiofur mAb 1D7) to 17.2 ng mL(-1) (cephapirin mAb 2F10). Specificity studies revealed that cephalosporin-antibody binding was strongly determined by the side chain residues of the cephem nucleus. Therefore all mAbs, to some extent, recognized other beta-lactam antibiotics with similar side chain residues. Within the group of cephalosporins approved for use in veterinary medicine, however, the final EIAs were highly selective for their respective antigen, except for the ceftiofur EIA which showed cross-reactions with cefquinome. The applicability of the five assays for drug residue testing in milk was demonstrated. In each EIA the target drug could be determined in milk with high accuracy and precision at concentrations far below the European Union maximum residue limits.

Validation of a multi-residue enzyme-linked immunosorbent assay for qualitative screening of corticosteroids in liver, urine and milk

A rapid and sensitive enzyme-linked immunosorbent assay (ELISA) was applied for the qualitative screening analysis of dexamethasone, betamethasone, flumethasone, and prednisolone in milk and urine, and dexamethasone, flumethasone and prednisolone in liver samples at levels corresponding to the European Union maximum residue limit (MRL), or at required performance levels (RPLs) for substances for which there is no established MRL. Method validation was performed according to Commission Decision 2002/657/EC criteria established for qualitative screening methods. In this regard, the following parameters were determined: detection capability (CCβ), specificity, limit of detection (LOD), limit of quantitation (LOQ), recovery, within-laboratory reproducibility, linearity and ruggedness. LODs were 0.2, 1.2 and 0.6 µg kg−1 in milk, urine and liver samples, and LOQ values were 0.3, 1.2 and 1.4 µg kg−1 in milk, urine and liver, respectively. Recoveries from spiked samples ranged from 68% to 131% for dexamethasone, from 57% to 120% for flumethasone, from 60% to 155% for betamethasone, and from 23% to 32% for prednisolone, with a coefficient of variation (CV) between 1.6% and 21.2%. The CCβ value was below the MRL/RPL for all examined matrices. Moderate variations of some critical factors in the sample pre-treatment for liver and milk samples were deliberately introduced for ruggedness evaluation and did not result in any negative effects on corticosteroid detection. The proposed method is suitable for qualitative screening analysis of corticosteroids in the above-mentioned food in conformity with the current European Union performance requirements.

Multi-walled carbon nanotubes–dispersive solid-phase extraction combined with nano-liquid chromatography for the analysis of pesticides in water samples

In this work, the simultaneous separation of a group of 12 pesticides (carbaryl, fensulfothion, mecoprop, fenamiphos, haloxyfop, diclofop, fipronil, profenofos, fonofos, disulfoton, nitrofen, and terbufos) by nano-liquid chromatography with UV detection is described. For the analyses, a 100 μm internal diameter capillary column packed with silica modified with phenyl groups was used. Experimental parameters, including the use of a trapping column for increasing the sensitivity, were optimized and validated. A preliminary study of the applicability of a rapid and practical dispersive solid-phase extraction (DSPE) procedure was developed for the extraction of some of these pesticides (carbaryl, fensulfothion, fenamiphos, fipronil, profenofos, fonofos, disulfoton, nitrofen, and terbufos) from Milli-Q water samples using multi-walled carbon nanotubes (MWCNTs). The method was validated through a recovery study at three different levels of concentration, obtaining limits of detection in the range 0.016-0.067 μg/L (below European Union maximum residue limits) for the majority of the pesticides. In this work, MWCNTs were reused up to five times, representing an important reduction of the waste of stationary phase. Furthermore, DSPE permitted a clear diminution of the total sample treatment time with respect to conventional SPE.