Multiresidue Procedure Research Articles

Novel Method Development for Extraction and Analysis of Pesticide Residues in Human Serum Samples

In recent years, exposure to pesticides has gained widespread attention due to their adverse health effects. Long-term exposure to pesticides has shown hazardous effects on vital functions of the human nervous and reproductive systems. Therefore, it is crucial to determine the extent of pesticide exposure in humans. Primarily, it is quite challenging to determine trace levels of pesticide residues in biological matrices. Hence, a quick, multi-residue extraction procedure was experimented for pesticide residue analysis in human serum. Herein, the original QuEChERS extraction method was modified for achieving the best possible recoveries. A total of 15 representative pesticides from each class were selected and fortified into the human serum samples. The extraction was performed by employing acidified solution containing acetonitrile and ethyl acetate followed by vortex and centrifugation. The obtained aqueous layer was collected and vapourised to dryness and d-SPE clean-up was conducted utilising PSA. The extracted sample was injected into the GC-MS/MS system under MRM mode. The method development parameters such as linearity, % RSD, accuracy, LOD, LOQ and % ME were assessed. The results obtained for the serum matrix were found to be within the criteria mentioned in European Union SANTE/12682/2019 guidelines for method validation. The developed solitary method is quick, simple and highly efficient for routine pesticide residue analysis. Hence, a wide spectrum of pesticides can be analysed utilising the proposed method for human serum.

Multiresidue procedure to assess the occurrence and dissipation of fungicides and insecticides in vineyard soils from Northwest Spain

The presence of fungicide and insecticide residues in wine has been largely investigated. However, few studies have addressed the persistence of these compounds in vineyard soils. In this research, we investigate the residues of a relevant number of fungicides and insecticides in vineyard soils, obtained in the Northwest of Spain, at the beginning of each agriculture campaign. Moreover, the dissipation of species showing high concentrations were monitored during the non-vegetative period of vines, in order to understand their soil evolution between application campaigns. To this end, a multiresidue analytical procedure based on pressurized liquid extraction (PLE) followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) determination was first optimized. Under final working conditions, absolute recoveries in the range from 70 to 130% were achieved for 44 out of 51 selected compounds. The method LOQs remained at the low ng g−1 level (0.2–13 ng g−1) with a linear response range up to 500 ng g−1. Analysis of vineyard soils, collected during a 2-year period, from a geographic area with a high incidence of fungal diseases, demonstrated the presence of relevant concentrations of several fungicides and the insecticide imidacloprid (IMI) in this compartment. Most compounds detected at the end of the application season remained in soil at the beginning of the next year campaign. Among them, six fungicides (dimethomorph, boscalid, myclobutanil, penconazole, pyraclostrobin and pyrimethanil) and IMI showed average dissipation efficiencies below 50%, so they pose a potential to accumulate in this kind of soils.

Studies on multiresidue determination of pesticides in fruits and vegetables by gas chromatography/mass spectrometry

A multiresidue method using gas chromatography/mass spectrometry (GC/MS) was evaluated for the determination of several pesticides in fruits and vegetables. The pesticides were extracted using a slightly modified Luke multiresidue procedure, separated by capillary column gas chromatography and detected by mass chromatography with quadrupole mass spectrometer in the electron impact mode. Recovery studies of chlorpyrifos, diazinon, endosulfan, fenarimol, fenvalerate, folpet, iprodione, malathion, methamidophos, phosmet and procymidone were performed at the 0.5 ppm spike level in cherry tomatoes, chin-chian pe-tsai, Chinese cabbages, kidney beans and oranges. Recoveries were between 64.6 and 124.6%, with the exception of methamidophos which produced interference due to the constituents of the samples. Coefficients of variation ranged between 0.3 and 17.6%, with an average of 5.3%. The estimated limits of detection of the pesticides (except methamidophos) in the crops were at the 0.1 ppm level. Because the mass spectrometer is capable of achieving higher levels of molecular specificity as compared to the traditional GC detectors and can be programmed to search for several hundred target ions simultaneously, GC/MS may be a promising method for the use of regulatory agencies with which to monitor pesticide residues in daily food products.

Occurrence of pesticides in fruits and vegetables from organic and conventional agriculture by QuEChERS extraction liquid chromatography tandem mass spectrometry

Human exposure to pesticides commands the implementation of food safety control, but few studies have provided a comparative assessment of conventional and organic products. This study set out to examine 22 pesticides in four distinct commodities (lettuce, apples, grapes, and tomatoes) from conventional and organic agriculture available to consumers. A multiresidue procedure based on QuEChERS extraction and ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was first validated for its robustness. Suitable determination coefficients (R2 > 0.99) and recoveries generally between 70 and 110% were obtained. Intraday and interday variations were <20% and low matrix effects were noted with sample-to-sample variation. Method limits of detection (LOD) in the overall range of 0.05–2 μg kg−1 were obtained. The validated method was applied to 133 fruit and vegetable samples purchased in Canada, including conventional and organic culture samples. Overall, 47% of the 133 samples had levels above the LOD for at least one pesticide. Neonicotinoid insecticides were detected in all four product types. Imidacloprid (0.08–29 μg kg−1), acetamiprid (0.11–108 μg kg−1), and clothianidin (0.13–141 μg kg−1) were the most recurrent. Atrazine was reported in approximately a third of the lettuce samples (0.25–7.5 μg kg−1). For varieties with samples available from both organic and conventional agriculture, the proportion of insecticide levels > LOD was significantly higher (p < 0.05) for samples from conventional agriculture (9.7%) than from organic agriculture (2.0%). Measured levels were compliant to Canadian Maximum Residue Limits (MRLs), but a thorough human health risk assessment has yet to be conducted for many of these pesticides.

GC-MS Modified Quechers Method for Multiresidue Pesticide Determination in Red Wine

This work reports a new selective and accurate multiresidue procedure for determination of 25 pesticides in red wine by GC-MS. Proposed procedure uses an original approach in sample preparation technique based on QuEChERS theory. Main focus of method development was modification of salts thus increasing ionic strength of solution which improved pesticides partitioning and extraction efficiency. LOQs were in the range 0.01–250 μg L–1 with 56 % of target pesticides below or equal to 10 μg L–1. RSD for most pesticides was &amp;lt; 20 % and recoveries were in the range 70–120 %. Matrix effect was found to be high for five pesticides confirming sample preparation procedure to be efficient. The proposed procedure was applied to 12 wine samples of different variety with determination of 40 % of target pesticides. Developed GC-MS methodology provides novel, selective and accurate approach for determination of 25 pesticide residues in red wine.

Determination of Multiclass Harmful Residues in Shellfish Using LC-MS

A multi-residue procedure with liquid chromatography-tandem mass spectrometry analysis was developed to simultaneously detect the presence of 4 diarrheic shellfish poisoning toxins, 14 sulfonamides, chloramphenicol and thiamphenicol in shellfish tissues. Samples were first purified by a modified rapid procedure and separated on a ZOBRAX Eclipse Plus C18 column and quantified using electron spray ionization-mass spectrometry-mass spectrometry. The results showed that the limits of quantification (LOQ) of SPX1, OA-C, GYM, and PTX-2 were 1.0, 2, 0.5 and 2 μg/kg, respectively. The LOQ for the antibiotics was below acceptable limits established by most countries. Compared to the external standard method, this matrix matched the calibration method effectively, overcame the matrix effects and gave better quantitative results. Recoveries of spiked compounds ranged between 67.6% and 109.8%, with relative standard deviations below 15% for most target analytes. Only sulfathiazole had a %RSD of 18.6% at the lowest spiked concentration. The proposed method was accurate, rapid and reliable.https://doi.org/10.21423/jrs-v05n01p009 (DOI assigned 4/17/2019)

Multiresidue Pesticide Analysis in Fresh Produce by Capillary Gas Chromatography−Mass Spectrometry/Selective Ion Monitoring (GC-MS/SIM) and −Tandem Mass Spectrometry (GC-MS/MS)†

A multiresidue method for the analysis of pesticides in fresh produce has been developed using salt-out acetonitrile extraction, solid-phase dispersive cleanup with octadecyl-bonded silica (C(18)), and graphitized carbon black/primary-secondary amine (GCB/PSA) sorbents and toluene, followed by capillary gas chromatography-mass spectrometry in selected ion monitoring mode (GC-MS/SIM) or -tandem mass spectrometry (GC-MS/MS). Quantitation was determined from calibration curves using matrix-matched standards ranging from 3.3 to 6667 ng/mL with r(2) > 0.99, and geometric mean limits of quantitation were typically 8.4 and 3.4 microg/kg for GC-MS/SIM and GC-MS/MS, respectively. Identification was determined by using target and qualifier ions and qualifier-to-target ratios for GC-MS/SIM and two ion transitions for GC-MS/MS. Fortification studies (10, 25, 100, and 500 microg/kg) were performed on 167 organohalogen, organophosphorus, and pyrethroid pesticides in 10 different commodities (apple, broccoli, carrot, onion, orange, pea, peach, potato, spinach, and tomato). The mean percent recoveries were 90 +/- 14, 87 +/- 14, 89 +/- 14, and 92 +/- 14% for GC-MS/SIM and 95 +/- 22, 93 +/- 14, 93 +/- 13, and 97 +/- 13% for GC-MS/MS at 10, 25, 100, and 500 microg/kg, respectively. GC-MS/MS was shown to be more effective than GC-MS/SIM due to its specificity and sensitivity in detecting pesticides in fresh produce samples. The method, based on concepts from the multiresidue procedure used by the Canadian Food Inspection Agency and QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe), was shown to be efficient in screening, identifying, and quantitating pesticides in fresh produce samples.

Simultaneous direct analysis of benzimidazole fungicides and relevant metabolites in agricultural products based on multifunction dispersive solid-phase extraction and liquid chromatography–mass spectrometry

A fast and flexible multi-residue procedure for effective extraction of benzimidazole fungicides and the related transformation products in various raw agricultural commodities is developed for direct and simultaneous analysis by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The new sample preparation method, introduced to allow direct extraction of the labile fungicides as the intact forms in complex matrices, is achieved using a conservative homogenizing extraction and multifunction adsorption cleanup (CHEMAC), which basically involves salting-out partitioning/extraction with acetate-buffered acetonitrile at low-temperature and sequential rapid solid-phase dispersive cleanup with a ternary sorbent mixture. The CHEMAC procedure was optimized and further modified by incorporating several pretreatment variables influencing sample stability and process efficiency, such as pH, temperature, salt and sorbent utilized. By using CHEMAC, a noteworthy improvement in extraction recoveries was obtained for the problematic fungicides, while no significant differential matrix effects were detected on the LC–MS/MS analysis in all 9 matrices. The in-source fragmentation of benomyl occurred but caused no cross-talk interference in multi-component analysis. Thus the CHEMAC-based LC–MS/MS strategy can serve as an attractive approach to satisfactory overall process efficiencies (70–92%) with acceptable repeatability (relative standard deviations below 16%) for all the analyte–matrix combinations. Mean accuracies were obtained within the range of 70–110% at fortified levels of 1–500 ng/g, with intra-day and inter-day variations less than 15 and 20%, respectively. The successful practical application of the proposed method to real samples has also been demonstrated.

Simultaneous determination of eleven quinolones in animal feed by liquid chromatography with fluorescence and ultraviolet absorbance detection

A rapid and simple multi-residue procedure is described for assaying eleven quinolones (cinoxacin, ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, flumequine, marbofloxacin, nalidixic acid, norfloxacin, oxolinic acid and sarafloxacin) in feeds at sub-additive levels (1–5 mg kg −1). Five grams of sample were extracted by a metaphosphoric acid/acetonitrile mixture (70/30, v/v) and purified onto OASIS HLB cartridges. The determination was achieved by liquid chromatography (LC) using a GEMINI C18 analytical column both with fluorescence detection (FD) and photodiode-array (DAD). Limits of detection for each drug were in the range 0.04–0.8 mg kg −1. Above the limit of quantification (LOQ), in poultry feed the recoveries were from 69 to 98% with relative standard deviations less than or equal 10%. Finally the measurement uncertainty was estimated using the bottom-up approach.

Preconcentration and determination of high leachable pesticides residues in water using solid-phase extraction coupled with high-performance liquid chromatography

A multi-residue procedure was developed for analysis of four common pesticides in water using solid-phase extraction and high-performance liquid chromatography in combination with UV detection at 230 nm. The investigated pesticides (atrazine, dicloran, metazachlor and simazine) are highly leachable and easily migrate within the soil. Multi-walled carbon nanotubes (MWCNTs) adsorbent outperformed C18 bonded silica and graphitized carbon black for preconcentration of the pesticides from solution. The optimum experimental conditions for pesticides extraction were carefully studied and optimised. At the optimum preconcentration conditions (sample volume: 700 mL; adsorbent mass: 300 mg; solution pH: 5.0; flow rate: 3.0 mL min−1; and elution medium: methanol), a quantitiative recovery for pesticides was reported and a high preconcentration factor (1400) was attained. The detection limits of the proposed method were found in the range: 5–15 ng L−1. The dynamic range for simazine and atrazine determination was extended from 15 to 1000 ng L−1, while for metazachlor and dicloran the range was within 60–1000 ng L−1. Five replicate determinations of 70 ng of pesticides mixture present in 700 mL solution gave good results with RSD values within the range 2.5 to 4.6%. The present method gave recoveries from 92.7 to 95.3% for determination of 100 ngL−1 of pesticides in tap water and recoveries from 85.3 to 87.0 in well water with satisfactory RSD values (≤6%).

Improved HPLC-MS/MS Method for Determination of Isoxaflutole (Balance) and Its Metabolites in Soils and Forage Plants

A robust multi-residue procedure is needed for the analysis of the pro-herbicide isoxaflutole and its degradates in soil and plant materials at environmentally relevant (<1 microg kg-1) levels. An analytical method using turbo-spray and heat-nebulizer high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed for the analysis of isoxaflutole (IXF) and its two metabolites, diketonitrile (DKN) and the benzoic acid metabolite (BA), at sub-microgram per kilogram levels in soil and plant samples. The average recoveries of the three compounds in spiked soil and plant samples ranged from 84 to 110% and 94 to 105%, respectively. The limits of quantification were validated at 0.06 microg kg-1 for soil and 0.3 microg kg-1 for plant samples. The limits of detection (LOD) for soil analysis were 0.01, 0.002, and 0.01 microg kg-1 for IXF, DKN, and BA, respectively. Corresponding LOD for the plant analysis method were 0.05, 0.01, and 0.05 microg kg-1. The developed method was validated using forage grass and soil samples collected from a field lysimeter study in which IXF was applied to each of four forage treatments. Forage plants and soils were sampled for analyses 25 days after IXF application to the soil. In soils, IXF was not detected in any treatment, and DKN was the predominant metabolite found. In forage plants, the concentrations of DKN and BA were 10-100-fold higher than that in soil samples, but IXF was not detected in any forage plants. The much higher proportion of BA to DKN in plant tissues (23-53%), as compared to soils (0-5%), suggested that these forages were capable of detoxifying DKN. The developed methods provided LODs at sub-microgram per kilogram levels to determine the fate of IXF and its metabolites in soils and forage plants, and they also represent considerable improvements in extraction recovery rates and detection sensitivity as compared to previous analytical methods for these compounds.

Chlorinated pesticide residues in the total diet of Kuwait

Total diet of Kuwait was assessed for the residues of chlorinated pesticides. 140 core samples along with 90 additional samples (collected during 1995–96) were analyzed following US FDA multiresidue procedures. The results showed that 17.6% of the core samples contained detectable residues. Chlorpyrifos-methyl was present (ranging from 0.05 to 0.72 mg/kg) in most of the positive samples. Wheat flour was the single important source of this residue in the diet. Residues of chlorpyrifos, vinclozolin, procymidon and captan were also detected in some fresh fruits and vegetable. In general, residue levels were quite low and were significantly below the maximum residue limits (MRLs) established for these pesticides in food.

Multiresidue Analysis of Cotton Defoliant, Herbicide, and Insecticide Residues in Water by Solid-Phase Extraction and GC−NPD, GC−MS, and HPLC−Diode Array Detection

A multiresidue procedure was developed for analysis of cotton pesticide and harvest-aid chemicals in water using solid-phase extraction and analysis by GC-NPD, GC-MS, and HPLC-DAD. Target compounds included the defoliants tribufos, dimethipin, thidiazuron; the herbicide diuron; and the insecticide methyl parathion. Three solid-phase extraction (SPE) media, octadecylsilyl (ODS), graphitized carbon black (GCB), and a divinylbenzene-N-vinyl pyrollidine copolymer (DVBVP), were evaluated. On GCB and ODS, recoveries varied depending on compound type. Recoveries were quantitative for all compounds on DVBVP, ranging from 87 to 115% in spiked deionized water and surface runoff. The method detection limit was less than 0.1 microg L(-)(1). SPE with DVBVP was applied to post-defoliation samples of surface runoff and tile drainage from a cotton research plot and surface runoff from a commercial field. The research plot was defoliated with a tank mixture of dimethipin and thidiazuron, and the commercial field, with tribufos. Dimethipin was detected (1.9-9.6 microg L(-)(1)) in all research plot samples. In the commercial field samples, tribufos concentration ranged from 0.1 to 135 microg L(-)(1). An exponentially decreasing concentration trend was observed with each successive storm event.

Multiresidue procedures for determination of triazine and organophosphorus pesticides in water by use of large-volume PTV injection in gas chromatography

Two procedures, based on large-volume injection with a programmed-temperature vaporizer (PTV), have been developed for the determination of several triazine and organophosphorus pesticides. The use of PTV for injection in gas chromatography (GC) has enabled the introduction of up to 200 μL sample extract into the GC, thus increasing the sensitivity of the method. PTV injection has been combined off-line with two different microextraction procedures—liquid-liquid partition and solid-phase extraction. A simple and rapid off-line liquid-liquid microextraction procedure (5 mL water/1 mL methyltert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5μg L−1. Recoveries of the overall procedure were >80% and the precision was better than 15%. Detection limits were 80% and coefficients of variation <12%) and the limits of detection ranged from 1 to 9 ng L−1. Finally, several surface water samples were anlysed, and triazine herbicides were detected at concentrations of approx. 0.1–0.2 μg L−1. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2 μL.

Confirmation of Eprinomectin, Moxidectin, Abamectin, Doramectin, and Ivermectin in Beef Liver by Liquid Chromatography/Positive Ion Atmospheric Pressure Chemical Ionization Mass Spectrometry

A liquid chromatographic (LC) multiresidue screening procedure was developed for determination of eprinomectin, moxidectin, abamectin, doramectin, and ivermectin in beef liver at 0, 25, 50, and 100 ppb levels. A procedure using low resolution LC/atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) was developed with further purification steps added to the quantitative LC method to confirm residues. Acetonitrile extracts of liver, prior to derivatization for LC analysis, were further purified by using a C8 solid-phase extraction cartridge and an alumina-B cartridge. The purified extract was analyzed by injection into an LC/positive ion APCI MS. Identity of the compound was confirmed by comparison of its retention time and relative intensity data with those of a standard or recovery from a fortified control liver sample. Anthelmintic drugs in acetonitrile extracts of liver containing eprinomectin, moxidectin, abamectin, doramectin, and ivermectin at 25 ppb, the lowest level of fortification used in the LC determinative method, were successfully confirmed.

Multiresidue analysis of β 2-agonists in human and calf urine using multimodal solid-phase extraction and high-performance liquid chromatography with electrochemical detection

Various β 2-agonists are used as illegal growth promoters in man and in animals. We developed a multiresidue procedure for the analysis of four β-agonists in human and calf urine. The sample was pre-extracted with an Extrelut column at alkaline pH. The β-agonists were eluted with a mixture of tert.-butylmethyl ether and hexane. Then the extract was further cleaned with a mixed mode SPE column, or with a combination of immunoaffinity chromatography (IAC) and the mixed mode SPE column. The IAC column contained antibodies against salbutamol, which were suitable for multiresidue extractions. The extract was then brought onto a mixed mode SPE column at an acidic pH. The column was washed with 70% methanol in water. Thereafter, the β-agonists were eluted with ammoniated ethanol–hexane. The extract was analysed with an HPLC method with electrochemical detection. The β-agonists were separated on a reversed-phase column using a mobile phase buffered at pH 5.5 and containing an ion-pair reagent. Recoveries were higher when the IAC procedure was not performed (90–105% vs. 65–75%), but the extracts were cleaner when the latter step was included. Detection limits in human and calf urine were in the low ng/ml range. The study indicated that β 2-agonists can be analysed in human and calf urine without the selectivity of a mass spectrometer, but that comprehensive clean-up is required to avoid the interference of urine matrix components.

SOLID PHASE EXTRACTION (SPE) FOR MULTI-RESIDUE ANALYSIS OF β2-AGONISTS IN BOVINE URINE

Solid phase extraction (SPE) for the treatment of bovine urine samples in the analysis of β2-agonist multi-residues by gas chromatography-mass spectrometry (GC-MS) was evaluated. Mabuterol, mapenterol, clenproperol, terbutaline, clenbuterol, salbutamol, clenpenterol, bromobuterol and hidroxi-metilclenbuterol (NA1141) were tested with five different mechanisms: adsorption, reverse phase, polar, ion exchange, and mixed phase, and eleven sorbents: diatomaceous earth, octadecyl (C18), octyl (C8), native silica (Si), diol (2OH), amine (NH2), trimethylaminopropyl (SAX), propylbenzenesulphonic (SCX), Bond Elut Certify® (C8+SCX), Clean Screen DAU® (CSDAU) and Multimode (C18+SCX+SAX). Recoveries of the nine β2-agonists from urine samples spiked at 20 ng mL−1 using metoprolol as internal standard were in ranges of 2.9% to 58.1%, of 12.0% to 60.7%, of 6.3% to 31.3%, of 3.3% to 56.8% and of 17.7% to 66.9%, respectively for adsorption, non polar, polar, ion exchange, and multiple extraction mechanisms. The coefficients of variation (C.V.) were also evaluated and discussed. The proposed study show that mixed phase sorbents, especially those which combine hydrophobic and strong cationic exchange interactions, were recommended for a β2-agonist multi-residue solid phase extraction procedure from bovine urine.

A method for the separation of residues of nine compounds in cattle liver related to treatment with oxfendazole.

A method for the determination of nine compounds closely related to oxfendazole has been developed for the monitoring of residues in food. The method is based on a multi-residue procedure for basic drug residues and used strong cation exchange solid phase extraction for sample clean-up. These nine compounds include fenbendazole, which is itself a licensed veterinary product. The pro-drug febantel converts quickly to fenbendazole or oxfendazole soon after administration. The method is therefore suitable for monitoring residues following the use of any of these compounds. Some of these analytes have been shown to be present as residues following the treatment of farm animals with oxfendazole. Average recoveries for the nine compounds from tissue fortified with 100 micrograms kg-1 were between 34% and 96% with relative standard deviations between 3% and 22%.

Dexamethasone and clenbuterol detection by enzyme immunoassay in Bovine Liver Tissue: A new multiresidue extraction procedure

A fast and simple extraction procedure was developed for simultaneous determination in bovine liver of two veterinary drugs, widely used as growth promoters in meat production: dexamethasone (a synthetic corticosteroid drug) and clenbuterol (a beta2‐adrenergic agonist drug). Liver samples were extracted by acetonitrile, without any clean‐up step. Two different ELISAs, specific for the two classes of drugs, were used to determine the residue concentration in the extracts. The intra‐ and inter‐extraction variability was determined at different concentrations: the intra‐extraction coefficients of variation (CVs) were between 2.5 and 17.7% for dexamethasone and between 0.9 and 9.8% for clenbuterol; the inter‐extraction CVs were between 2.0 and 16.8% for dexamethasone and between 0.5 and 10.8% for clenbuterol. Recovery ranged from 92 to 154% for dexamethasone and from 78 to 105% for clenbuterol. The limit of detection was 1.43 ng g−1 and 0.43 ng g−1, respectively. The limit of quantification for dexamethasone was 2.09 ng g−1 and for clenbuterol was 0.72 ng g−1. The combination of the new extraction procedure with an ELISA detection permitted the rapid semi‐quantitative determination of both dexamethasone at its maximum residue level (MRL: 2.5 ng g−1 in liver tissue), and clenbuterol at low concentration level.

Determination of Free Metabolites of Ceftiofur in Animal Tissues with an Automated Liquid Chromatographic Cleanup

Ceftiofur, a recently introduced antibiotic of the beta-lactam group, is rapidly converted to both free and protein-bound metabolites when administered by the prescribed procedure, intramuscular injection. Free metabolites retain antimicrobial activity and may be detected by antibiotic-screening tests based on antimicrobial activity. It is thus desirable to distinguish ceftiofur metabolites from other antibiotics. A multiresidue procedure for beta-lactams in milk was adapted for determination of free ceftiofur metabolites by collecting appropriate liquid chromatographic fractions during cleanup. Analysis of tissues from treated animals showed that the principal free metabolite was the desfuroylceftiofurcysteine conjugate.