Patrick Edder

Comprehensive fast multiresidue screening of 150 veterinary drugs in milk by ultra-performance liquid chromatography coupled to time of flight mass spectrometry ☆

This paper shows the use of ultra-performance liquid chromatography (UPLC) coupled to orthogonal acceleration time of flight mass spectrometry (TOF MS) for the comprehensive screening of 150 veterinary drugs residues in raw milk. An easy sample preparation based on protein precipitation associated with ultrafiltration was hyphenated to fast chromatography. This method enabled the screening for more than 50 samples per day and searched for 150 drugs and metabolites including avermectines, benzimidazoles, beta-agonists, beta-lactams, corticoides, macrolides, nitroimidazoles, quinolones, sulfonamides, tetracyclines and some others. Identification of contaminants is based on accurate mass measurement. UPLC-TOF also showed very good performances for quantitation and allowed the determination of majority of compounds below MRL. An in-house validation procedure was conducted based on European directive 2002/657/EC with measurement of response function, accuracy, repeatability, limits of detection (LOD), decision limit (CCalpha) and detection capability (CCbeta).

Pesticide residues survey in citrus fruits

The use of pesticides is widespread in citrus fruits production for pre- and post-harvest protection and many chemical substances may be applied in order to control undesirable moulds or insects. A survey was carried out to evaluate levels of pesticide residues in citrus fruits. Two multiresidue analytical methods were used to screen samples for more than 200 different fungicides, insecticides and acaricides. A total of 240 samples of citrus fruits including lemon, orange, mandarin, grapefruit, lime, pomelo and kumquat were taken in various markets in the Geneva area during the year 2003. Ninety-five percent of the 164 samples issued from classical agriculture contained pesticides and 38 different compounds have been identified. This high percentage of positive samples was mainly due to the presence of two post-harvest fungicides, imazalil and thiabendazole, detected in 70% and 36% of samples respectively. Only three samples exceeded the Swiss maximum residue limits (MRLs). Fifty-three samples sold with the written indication “without post-harvest treatment” were also controlled. Among theses samples, three exceeded the Swiss MRLs for penconazole or chlorpyrifos and 18 (34%) did not respect the written indication since we found large amounts of post-harvest fungicides. Finally, 23 samples coming from certified organic production were analysed. Among theses samples, three contained small amounts of pesticides and the others were pesticides free.

Aminoglycoside analysis in food of animal origin with a zwitterionic stationary phase and liquid chromatography–tandem mass spectrometry

In this study, fourteen highly polar aminoglycoside (AGs) antibiotics were selected. Various stationary phases were tested, including Obelisc R, ZIC-HILIC, BEH amide and aminopropyl. The nature of the stationary phase, mobile phase (water or buffer solutions and acetonitrile), pH (percentage of formic acid), gradient conditions and injection solvents were systematically studied as relevant parameters for tuning retention selectivity and detectability of AGs in liquid chromatography electrospray tandem mass spectrometry (LC-(ESI)-MS/MS). Only the two zwitterionic phases (Obelisc R and ZIC-HILIC) achieved a proper chromatographic separation considering interferences due to the crosstalk effect in low resolution mass spectrometers. The water/acetonitrile mobile phase containing 1% formic acid used with Obelisc R provided more sensitivity than the highly concentrated buffered mobile phases required for ZIC-HILIC. A solid phase extraction (SPE) clean-up procedure with polymeric weak cation exchange (WCX) cartridges was optimized for honey, milk and liver samples. Different brands of cartridges and elution solvents were tested, and the Taurus WCX offered the best recovery rate with a buffer elution at pH 3. The final optimized method was validated in these matrices according to Decision 2002/657/EC. A monitoring campaign for sixty honey, milk and liver samples was carried out at the Food Authority Control in Geneva. The concentration of dihydrostreptomycin (DSTP) found in one ovine liver exceeded the established maximum residue levels (MRLs) within the European and Swiss legislations but it was compliant taking into account the validation data.

Dissipation of pesticides during composting and anaerobic digestion of source-separated organic waste at full-scale plants

In the present study, concentration levels and dissipation of modern pesticides during composting and digestion at full-scale plants were followed. Of the 271 pesticides analyzed, 28 were detected. Within the three windrows studied, total concentrations were between 36 and 101microg per kg of dry matter (d.m.) in input materials and between 8 and 20microg kg d.m.(-1) in composts after 112 days of treatment. Fungicides and among them triazoles clearly dominated over other pesticides. More than two-thirds of all pesticides detected in the input materials showed dissipation rates higher than 50% during composting, whilst levels of most triazoles decreased slightly or remained unchanged. The investigation on semi-dry thermophilic anaerobic digestion suggests that pesticides preferentially end up in presswater after solid-liquid separation.

Multi-targeted screening of botanicals in food supplements by liquid chromatography with tandem mass spectrometry.

Safety, quality and composition assessments of food supplements based on botanical ingredients are of major concern, as they have usually not been through a rigorous testing process as required for the approval of therapeutic phytopreparations. Therefore, an efficient multi-targeted method was developed to screen selected botanicals of interest in herbal food supplements. Liquid chromatography coupled with a hybrid triple quadrupole linear ion trap was used for this purpose. Botanicals were characterised by means of appropriate biomarkers, which were unambiguously identified by mass spectrometry using an information dependent acquisition experiment which combined a multiple reaction monitoring survey with dependent enhanced product ion scans. During this procedure, product ion scans of targeted analytes were generated at three collision energies and compared with an in-house library of MS/MS spectra acquired from reference standards of all biomarkers. This generic method enables detection, identification and quantification of 98 biomarkers intended to characterise 79 selected plants.

Analysis of erythromycin and oleandomycin residues in food by high-performance liquid chromatography with fluorometric detection

A reliable and sensitive procedure is presented for the analysis of erythromycin (ERY) and oleandomycin (OLE) in food of animal origin, such as meat, liver, kidney, raw milk and egg. The method is based on a solid-phase extraction clean-up with a cation exchange cartridge, a 9-fluoromethylchloroformate (FMOC) precolumn derivatization and a separation by HPLC with fluorometric detection. The selectivity is satisfactory enough to control ERY and OLE residues as not many interfering peaks are observed for various food matrices. The macrolides recoveries of the total procedure were low, although >50%. However, addition of an internal standard (roxithromycin) corrected for recovery to give satisfactory quantitative results for repeatability, linearity, detection and quantification limits and mainly accuracy.

Risk assessment of herbicide mixtures in a large European lake

Lake Geneva is one of the largest European lakes with a surface area of 580 km2. Its catchment area covers 7400 km2, of which ∼20% is arable land. Monitoring campaigns have been carried out in 2004 and 2005 to determine the contamination of the lake by pesticides. The results highlight the widespread presence of herbicides in water, the measured concentrations for most substances remaining constant in 2004 and 2005. However, for some individual herbicides the concentrations increased drastically (e.g., the herbicide foramsulfuron). We assessed the environmental risk of the herbicides detected in the lake using water quality criteria recently determined for the Swiss environmental protection agency. Furthermore, we assessed the risk of herbicide mixtures, grouped based upon their mode of action. Generally, the risk estimated for all single substances is low, except for some sulfonylurea compounds. For these substances, the measured concentrations are higher than the predicted no‐effect concentration. Impact on the flora of the lake can therefore not be excluded. When mixtures of pesticides with similar mode of action are taken into account, the risk remains lower than the mixture water quality criteria for all groups, but can reach as high as one third of this quality criteria. A further step would therefore be to assess the risk of the total pesticide mixture, including similar and dissimilar modes of action.

Analysis of Nitrofuran Metabolites in Food by High-Performance Liquid Chromatography with Tandem Mass Spectrometry Detection

Abstract A reliable and sensitive procedure is presented for the analysis of nitrofuran metabolite residues in foods of animal origin, like poultry and shrimp. The method is based on a one-step extraction/derivatization, followed by solid-phase extraction clean-up with polymeric phase cartridges. The separations were carried out by liquid chromatography coupled with tandem mass spectroscopy detection. Results from the full validation of the procedure and from a survey of food available from the Swiss market, with the analysis of 236 samples of shrimp, poultry, fish and rabbit, are presented and demonstrate that this method is satisfactory in order to control nitrofuran residues in foods of animal origin.

Comprehensive screening of veterinary drugs in honey by ultra-high-performance liquid chromatography coupled to mass spectrometry

In the context of multi-residue screening in honey, a complete methodology was developed for 200 veterinary drugs comprising a sample preparation step and an ultra-high-performance liquid chromatography (UHPLC) coupled to time-of-flight (TOF) mass spectrometry analysis. In addition, specific analytical strategies were developed for two compounds, streptomycin and chloramphenicol, using UHPLC and tandem mass spectrometry (MS/MS). Methodologies were then applied to real honey samples obtained from the Swiss market.

Extended-spectrum β-lactamase-producing Enterobacteriaceae in hospital food: a risk assessment.

OBJECTIVE Determine the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-PE) contamination of food and colonization of food handlers in a hospital kitchen and compare retrieved ESBL-PE strains with patient isolates. DESIGN Cross-sectional study. SETTING A 2,200-bed tertiary care university hospital in Switzerland. PARTICIPANTS Food handlers. METHODS Raw and prepared food samples were obtained from the hospital kitchen, with a comparator group from local supermarkets. Fecal samples collected from food handlers and selectively pre-enriched homogenized food samples were inoculated onto selective chromogenic media. Phenotypic confirmation of ESBL production was performed using the double disk method. Representative ESBL-PE were characterized using polymerase chain reaction (PCR) and sequencing for blaCTX-M, blaSHV, and blaTEM genes, and Escherichia coli strains were typed using phylotyping, repetitive element palindromic PCR, and multilocus sequence typing. Meat samples were screened for antibiotic residues using liquid chromatography time-of-flight mass spectrometry. RESULTS Sixty (92%) of the raw chicken samples were ESBL-PE positive, including 30 (86%) of the hospital samples and all supermarket samples. No egg, beef, rabbit, or cooked chicken samples were ESBL-PE positive. No antibiotic residues were detected. Six (6.5%) of 93 food handlers were ESBL-PE carriers. ESBL-PE strains from chicken meat more commonly possessed blaCTX-M-1 and blaCTX-M-2, whereas blaCTX-M-14 and blaCTX-M-15 were predominant among strains of human origin. There was partial overlap in the sequence type of E. coli strains of chicken and human origin. No E. coli ST131 strains or blaCTX-M-15 genes were isolated from meat. CONCLUSIONS Although there is significant ESBL-PE contamination of delivered chicken meat, current preventive strategies minimize risks to food handlers, hospital staff, and patients.