Dual-Label Chemiluminescence Strategy for Multiplexed Immunoassay of 20 Fluoroquinolones, 15 β-Lactams, 15 Sulfonamides,and CAP in Milk

In this paper, a novel dual-label time-resolved chemiluminescent multiplexed immunoassay (DLTRC-MIA) based on the distinction of the kinetic characteristics of horseradish peroxidase (HRP) and alkaline phosphatase (ALP) with approximate estimation approach for simultaneous determination of 20 fluoroquinolones (FQs), 15 β-lactams, 15 sulfonamides (SAs), and chloramphenicol (CAP) in milk was developed. The strategy integrated a single-chain variable fragment–alkaline phosphatase fusion protein (scFv-ALP), a recombinant penicillin-binding protein (PBP) 2×*, a monoclonal antibody (MAb), and a polyclonal antibody (PAb) in one immunoassay and in a single well together to fulfill the simultaneous detection of 51 low-molecular weight contaminants (20 FQs, 15 β-lactams, 15 SAs, and CAP). The limits of detection for FQs, β-lactams, SAs, and CAP range from 0.29 μg L^?1 for ciprofloxacin (CIP) to 81.6 μg L^?1 for trovafloxacin (TRO), 0.27 μg L^?1 for ceftiofur (CEF) to 44.1 μg L^?1 for cephalexin (CEL), 0.089 μg L^?1 for sulfadimethoxine (SDM) to 2.7 μg L^?1 for sulfadiazine (SDZ), and 0.028 μg L^?1 for CAP, respectively. The results demonstrated that the detection limits of DLTRC-MIA meet the requirement of detection levels for 51 drug residues in milk, suitable for high-throughput screening of low-molecular weight contaminants.     

Development and Validation of a Sensitive Indirect Competitive Enzyme-Linked Immunosorbent Assay for the Screening of Florfenicol and Thiamphenicol in Edible Animal Tissue and Feed

To monitor the illegal use of florfenicol (FF) and thiamphenicol (TAP) in edible animal tissue and feed, a sensitive monoclonal antibody-based indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) has been developed with simple sample preparation and cleanup. The obtained monoclonal antibody (5F4) that has isotype IgG1 showed an IC₅₀ value of 0.21 μg L^?1 for FF and 0.35 μg L^?1 for TAP, respectively. It did not exhibit measurable cross-reactivity with other antibiotics. The limits of detection (LODs) for FF and TAP in a muscle matrix ranged from 0.07 to 0.14 μg kg^?1 and in a feed matrix ranged from 2.9 to 5.2 μg kg^?1. The recoveries were 72.8 to 113.4 % with a coefficient of variation of less than 15 %. Good correlation between the ELISA and HPLC-MS/MS results in the tissues tested demonstrated the reliability of our ic-ELISA. This ELISA is a useful tool for screening FF and TAP in edible animal tissue and feed.     

Confirmatory Method for the Determination of Amphenicols in Muscle and Kidney of Several Animal Species

A rapid and reliable method using liquid chromatography (UHPLC) tandem mass spectrometry (MS/MS) to identify and quantify chloramphenicol (CAP), thiamphenicol (TAP), florfenicol (FF) and its marker residue florfenicol amine (FFA) has been developed and validated. FF and TAP are both allowed substances and different MRLs have been established for different matrices and species. However, CAP is a well-known forbidden substance with a MRPL of 0.3 μg kg^?1 for all matrices. It was relevant to develop this confirmatory method to quantify simultaneously the four amphenicols in kidney and muscle of all species, to make more effective the official control programme for this group of substances. The variety of levels of interest to be studied for the allowed compounds and the different chemical behaviour of FFA have been the main difficulties in the development and validation of the method. The method has been validated in swine, bovine, caprine, equine, porcine, aquaculture species, rabbit and poultry muscle and kidney (except aquaculture species, rabbit and poultry). Performance criteria have been calculated in accordance with Commission Decision 2002/657/EC. The proposed procedure is being applied to the official control in the Valencian Region after being successfully evaluated by ENAC (Spanish national body for the accreditation).     

Depletion of florfenicol and florfenicol amine in eggs of laying hens and growing pullets after oral administration

ABSTRACT

In this study, we carried out two experiments to evaluate depletion of florfenicol (FF) and its metabolite florfenicol amine (FFA) in eggs from growing pullets and laying hens. Eggs were collected, and the egg white and yolk were separated. FF and FFA were analysed by liquid chromatography-tandem mass spectrometry. In the first experiment, 30 laying hens were given FF capsules at 50 mg/kg·bw^?1 daily for 5 d. FF + FFA was detectable in egg white (1,190 µg/kg) on day 1 of treatment and increased slowly thereafter. After treatment, the residues decreased rapidly and were not detected by day 11. In yolk, residues were detected at a lower concentration on day 1 and increased dramatically to 3308 µg/kg at the end of treatment. The residues remained steady over the next 4 days post-treatment, followed by a rapid drop. Residues were not detectable on day 15 post-treatment. In the second experiment, four groups (B1 through B4) of growing pullets were treated in the same manner for 25, 20, 15, and 10 days before egg primiparity. FF and FFA were not detectable in the eggs of group B1; however, they were detectable in egg whites and yolks of groups B2, B3, and B4. The highest total concentrations of FF and FFA detected in egg white and yolk of group B4 were 3,190 µg/kg and 3,214 µg/kg, respectively. Thereafter, concentrations decreased until no more residues were detected in egg whites or yolks on days 17 and 21 post-treatment, respectively. Therefore, drug treatment should be stopped at least 21 d before primiparity of growing pullets to guarantee food safety.     

Occurrence of bound 3-monochloropropan-1,2-diol content in commonly consumed foods in Hong Kong analysed by enzymatic hydrolysis and GC-MS detection

The aim of this study was to determine the level of bound 3-monochloropropan-1,2-diol in foodstuffs commonly consumed in Hong Kong, China, by an enzymatic hydrolysis indirect method which proved to be free from interferences. A total of 290 samples were picked up randomly from the local market and analysed. About 73% of these samples were found to contain detectable amounts of bound 3-MCPD. Amongst the 73 food items, bound 3-MCPD was not detected in 13 food items, including extra virgin olive oil, beef ball/salami, beef flank, ham/Chinese ham, nuts, seeds, soy sauce, oyster sauce, butter, yoghurt, cream, cheese and milk. For those found to contain detectable bound 3-MCPD, the content ranged up to 2500 µg kg^?1. The highest mean bound 3-MCPD content among the 14 food groups was in biscuits (440 [50–860] µg kg^?1), followed by fats and oils (390 [n.d.–2500] µg kg^?1), snacks (270 [9–1000] µg kg^?1), and Chinese pastry (270 [n.d.–1200] µg kg^?1). Among the samples, the highest bound 3-MCPD content was in a grape seed oil (2500 µg kg^?1), followed by a walnut flaky pastry (1200 µg kg^?1) and a grilled corn (1000 µg kg^?1). Basically, the results of this study agreed well with other published results in peer-reviewed journals, except for cheese, cream, ham, nuts and seeds.     

Occurrence of chloramphenicol in cereal straw in north-western Europe

Two surveys are presented of straw analysed for naturally occurring chloramphenicol (CAP), a drug banned for use in food-producing animals. In the first study, CAP was analysed by LC-MS/MS and detected in 37 out of 105 straw samples originating from the Netherlands, France, the UK, Germany and Denmark. The highest level found was 6.3 µg kg^?1, the average 0.6 µg kg^?1 and the median 0.2 µg kg^?1. The second study included a method comparison between ELISA and LC-MS/MS and a survey of CAP in cereal straw sampled at farms in all areas of Sweden. A total of 215 samples were screened by ELISA and a subset of 26 samples was also analysed by LC-MS/MS. Fifty-four of the samples contained more than 1 µg kg^?1 CAP and the highest level found was 32 µg kg^?1 (confirmed by LC-MS/MS). The highest contents of CAP in this study were allocated to the Baltic sea coast in the south-eastern part of Sweden (the county of Skåne and the Baltic Sea isle of Gotland). These results indicate a high incidence of CAP in straw in north-west Europe and have a severe impact on the enforcement of European Union legislation.     

氟苯尼考及其代谢物氟苯尼考胺在肉鸡中残留消除规律

目的 评估氟苯尼考及其代谢物氟苯尼考胺在不同品种肉鸡中的残留消除规律。方法 选用AA肉鸡、WOD168肉鸡、雪山鸡和狼山鸡为试验对象, 于出栏前3周开始按氟苯尼考25 mg/kg体重饮水给药, 连用5 d, 于停药后1、3、5、7、10、14 d采集肌肉、肝脏、肾脏、皮脂, 检测其中的氟苯尼考和氟苯尼考胺残留量, 并利用WT1.4软件计算休药期。结果 氟苯尼考及其代谢物氟苯尼考胺可迅速残留于肉鸡肌肉、肝脏、肾脏和皮脂中, 残留物以氟苯尼考为主。停药后第1 d残留量达到峰值, 肾脏组织中的残留量最大; 停药后第3 d, 各组织中氟苯尼考和氟苯尼考胺的残留量进入快速消除期, 均低于最大残留限量值; 停药后第14 d已基本消除完全。利用WT1.4软件计算出AA肉鸡、WOD168肉鸡、雪山鸡和狼山鸡休药期分别至少为3.22、3.85、4.49和4.32 d。结论 氟苯尼考在慢速型肉鸡体内的休药期要长于快速型肉鸡, 但都小于5 d。     

Ochratoxin A in traditional dry-cured meat products produced from sub-chronic-exposed pigs

The presence of ochratoxin A (OTA) was determined in traditional dry-cured meat products made from sub-chronically OTA-exposed pigs. The experimental group of pigs (n = 5) was treated with 300 µg OTA kg^–1 of feed during 30 days, whereas the control group (n = 5) remained untreated. After the household production of six types of dry-cured meat products based on traditional recipes, OTA residues were determined in final products produced from each treated and untreated animal using an immunoenzymatic technique (ELISA) and HPLC with fluorescence detection (HPLC-FD). The analytical methods showed acceptable analytical performance results and high correlation coefficients. Mean OTA concentrations ranged from 4.51 ± 0.11 µg kg^–1 in smoked ham to 6.87 ± 2.01 µg kg^–1 in home-made Slavonian sausage. The study demonstrated that pig exposure to OTA leads to the accumulation of OTA residues in muscle and adipose tissue used for the production, and consequently results in contamination of the final meat products.     

Simultaneous Determination of Multiclass Pesticides and Antibiotics in Honey Samples Based on Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

A simple, fast, and efficient method was developed for simultaneous determination of 79 pesticides and 13 antibiotics compounds of different chemical classes of pesticides and antibiotics in honey samples by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). The sample preparation procedure includes homogenization with McIlvaine buffer 0.1 mol L^?1 (pH 4), followed by extraction with acetonitrile and cleanup with florisil, using dispersive solid phase extraction (d-SPE). The proposed method was validated with good results, such as linearity (r ²?>?0.9901), normality, and independence of the evaluated data, as well as recoveries between 70 and 120 % with relative standard deviation (RSD) <20 % for most of the compounds spiked from 0.1 to 200 μg kg^?1. The experimental method limits of detection and quantification were from 0.03 to 1.51 μg kg^?1 and from 0.1 to 5 μg kg^?1, respectively, for the pesticides. For the antibiotics, the decision limits (0.1 to 2 μg g^?1) and the detection capacity (0.12 to 2.81 μg g^?1) were below the maximum residue limits (MRLs) established for honey by the Brazilian and European legislation. The method was successfully applied to real samples from different botanical and geographic origins. From them, 44 % presented residues from 0.12 to 10 μg kg^?1 of one or more analytes. The proposed method combines the advantages of a quick sample preparation step with the selectivity and sensitivity of the UHPLC-MS/MS and proved to be suitable for routine analyses.     

Determination of glyphosate,AMPA, and glufosinate in honey by online solid-phase extraction-liquid chromatography-tandem mass spectrometry

A simple method was developed for the simultaneous determination of glyphosate, its main degradation product (aminomethylphosphonic acid), and glufosinate in honey. Aqueous honey solutions were derivatised offline prior to direct analysis of the target analytes using online solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry. Using the developed procedure, accuracies ranging from 95.2% to 105.3% were observed for all analytes at fortification levels of 5, 50, and 150 μg kg^?1 with intra-day precisions ranging from 1.6% to 7.2%. The limit of quantitation (LOQ) was 1 μg kg^?1 for each analyte. Two hundred honey samples were analysed for the three analytes with AMPA and glyphosate being most frequently detected (99.0% and 98.5% of samples tested, respectively). The concentrations of glyphosate were found to range from <1 to 49.8 μg kg^?1 while those of its degradation product ranged from <1 to 50.1 μg kg^?1. The ratio of glyphosate to AMPA was found to vary significantly amongst the samples where both analytes were present above the LOQ. Glufosinate was detected in 125 of 200 samples up to a maximum concentration of 33.0 μg kg^?1.     

Determination of Pydiflumetofen Residues in Some Foods of Plant and Animal Origin by QuEChERS Extraction Combined with Ultra-Performance Liquid Chromatography–Tandem Mass

A rapid and effective analytical method for determination of pydiflumetofen residues in some foods of plant and animal origin (grapes, tomatoes, wheat, pork, milk, and eggs) was developed using a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation procedure followed by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS). Acetonitrile was served as the extraction solvent, and an octadecylsilane-dispersive solid-phase extraction (C18-dSPE) was used to cleanup the analyte, and then detected by UPLC–MS/MS. Pydiflumetofen was eluted within 3.0 min from the HSS T3 chromatography column connected to an electrospray ionization source in positive mode. The linearity of the method was excellent (R²?≥?0.992) in the pydiflumetofen concentration range of 10–1000 μg kg^?1. The recoveries of spiked pydiflumetofen (10, 100, and 1000 μg kg^?1) from the matrices were satisfactory, being between 72.0 and 110.3%, and all with relative standard deviation values of <?15.1%. The limit of quantification for pydiflumetofen was 10 μg kg^?1. This study provides a method for the routine monitoring of pydiflumetofen.     

A reliable,simple and cost-efficient TLC-HPLC method for simultaneously determining florfenicol and florfenicol amine in porcine urine: application to residue surveillance

ABSTRACT

Violative residues of florfenicol (FF) in porcine edible tissues pose a potential risk for human health. In this study, urine was selected as target matrix for routine residue monitoring of FF in pig, and a thin layer chromatography (TLC)-high-performance liquid chromatography (HPLC) method was developed for simultaneously determining FF and florfenicol amine (FFA) in porcine urine. The urine samples were extracted with ethyl acetate under alkaline environment. The extracts were enriched through evaporation, purified by TLC and analysed by HPLC at 225 nm. A Waters Symmetry C₁₈ column was used for the separation of the two analytes. The mobile phase was acetonitrile-phosphate buffer mixtures (33.3: 66.7, v/v), and was pumped at 0.6 mL/min. The TLC-HPLC method was well validated and successfully applied to residue depletion study. Good analytical specificity was confirmed by the lack of interfering peaks at the retention times of FF and FFA. The standard curves showed good linearity (FF: y = 143064x – 1045.3, r= 0.9999; FFA: y = 275826x + 1888.8, r= 0.9999) over the range of 0.0625–8 μg/mL. The precision ranged from 0.83% to 11.66% and 2.19% to 8.75% for intraday and interday determination, respectively. The corresponding accuracy ranged from ?13.38% to 10.78% and ?12.15% to 7.14%, respectively. The limits of quantification (LOQs) for FF and FFA were 0.125 μg/mL. The residue depletion study showed that the concentrations of FF and FFA in urine were higher than those in edible tissues at three time points. This method was reliable, simple and cost efficient, and could be used to monitor FF residues in porcine edible tissue without slaughtering animals. TLC showed excellent purification efficiency and is expected to solve matrix interferences in veterinary drug residue analysis.     

Oxytetracycline,tetracycline, chlortetracycline and doxycycline in pasteurised cow’s milk commercialised in Brazil

The aim of this study was to investigate the presence of tetracycline residues in pasteurised cow’s milk using high-performance liquid chromatography coupled with UV/VIS detection to determine the exposure of Brazilian’s population to antibiotic residues. One hundred samples collected from the State of Paraná, Brazil, were analysed. Three of these samples were contaminated at the following concentrations: 121.8 µg·kg^?1 for oxytetracycline, 93.5 µg·kg^?1 for tetracycline and 134.6 µg·kg^?1 for chlortetracycline (61.6 µg·kg^?1) and doxycycline (73.0 µg·kg^?1). The median tetracycline residue concentration found in the samples was 42.3 µg·kg^?1, and the estimated daily intake (EDI) was 0.05 µg Kg^?1 bw day^?1 in Brazil. These results demonstrate that the occurrence of tetracycline in Brazilian milk was low (3%) and only for 2% above the maximum residue limit, so the risk to the population from the presence of these residues in milk was low (<1% of the acceptable daily intake).     

Development of a Competitive Indirect Enzyme-Linked Immunosorbent Assay for Screening Phenylethanolamine A Residues in Pork Samples

Phenylethanolamine A (PEA), a new alternative β-agonist, has been illegally used in farming to promote the muscle growth in food-producing animals. In this study, a sensitive and convenient competitive indirect enzyme-linked immunosorbent assay (ciELISA) was developed for determination of PEA residues in pork samples. The produced antibody was highly specific to PEA and exhibited a negligible cross-reactivity toward some other β-agonists. The developed technique was characterized by the limit of detection below 0.08 μg kg^?1 and the IC₅₀ value of 0.93 pmol mL^?1 (0.32 ng mL^?1). Validation of the technique was done using artificially spiked and naturally contaminated pork samples. The recoveries ranged from 79.6 to 112.6 % for the samples spiked at levels of 0.1–5 μg kg^?1 with the variation coefficients below 15 %. The analysis of naturally contaminated samples showed that the obtained data corresponded with the data obtained by the LC-MS/MS. The developed ciELISA was shown to be a feasible highly sensitive and specific screening tool for PEA residue analysis.     

Determination of Pesticide Residues in Golden Berry (<Emphasis Type="Italic">Physalis peruviana</Emphasis> L<Emphasis Type="Italic">.</Emphasis>) by Modified QuEChERS Method and Ultra-High Performance Liquid Chromatography-Tandem Quadrupole Mass Spectrometry

A fast and effective multiresidue method for the determination of 42 pesticides in golden berry was developed and validated. A modified QuEChERS method was established for sample preparation followed by ultra-high performance liquid chromatographic-tandem mass spectrometry (UHPLC-MS/MS) determination with electrospray ionization in a triple quadrupole system. Validation results were satisfactory, since the method presented recoveries between 70 and 114 % with relative standard deviations (RSD) <20 % for blank samples spiked from 5 to 25 μg kg^?1. The method limit of detection and limit of quantification were 1.5 and 5 μg kg^?1 _, respectively. Matrix effect ranged from ?32 to 218 % and was compensated using matrix-matched calibration. Method linearity was established from 2.5 to 100 μg kg^?1 with r ² ≥ 0.99. The proposed method combines the advantages of a simple and fast sample preparation step by a modified QuEChERS method with the high selectivity and sensitivity of the UHPLC-MS/MS system using selected reaction monitoring. The method was successfully applied to commercial samples, proving to be an efficient alternative for routine analysis. From the 16 analyzed samples, 13 presented residues of one or more pesticides (carbendazim, chlorpyrifos ethyl, dimethoate, propamocarb, and tebuconazole) in the concentration range of 2.0 to 55.6 μg kg^?1.     

Co-occurrence of aflatoxins,ochratoxin A and citrinin in “egusi” melon (Colocynthis citrullus L.) seeds consumed in Ireland and the United Kingdom

The natural co-occurrence of aflatoxins (AFs), ochratoxin A (OTA) and citrinin (CIT) in melon seed samples obtained from retailers and households in Ireland and the United Kingdom (UK) was evaluated. AFs and OTA were determined by HPLC with fluorescence detection while CIT was analysed by HPLC-MS/MS. AFB₁ was detected in all (100%) samples (mean = 9.7 μg kg^?1; range = 0.2–66.5 μg kg^?1). Mean total AFs was 12.0 μg kg^?1 (range = 0.3–82 μg kg^?1). Commercially retailed samples showed a significantly higher AFB₁ contamination (p < 0.05) than the household samples. OTA occurred in 3 (13.6%) samples, while 4 (18.2%) were contaminated with CIT at very low levels. In this study, 68% of the melon seed samples were contaminated above the 2 μg kg^?1 EU limit for AFB₁ in oilseeds. These results highlight the need for the development of strategies to reduce AF contamination in “egusi” for human consumption.     

Simple detection of residual enrofloxacin in meat products using microparticles and biochips

A simple and sensitive method for detecting enrofloxacin, a major veterinary fluoroquinolone, was developed. Monoclonal antibody specific for enrofloxacin was immobilised on a chip and fluorescent dye-labelled microparticles were covalently bound to the enrofloxacin molecules. Enrofloxacin in solution competes with the microparticle-immobilised enrofloxacin (enroMPs) to bind to the antibody on the chip. The presence of enrofloxacin was verified by detecting the fluorescence of enrofloxacin-bound microparticles. Under optimum conditions, a high dynamic range was achieved at enrofloxacin concentrations ranging from 1 to 1000 μg kg^?1. The limits of detection and quantification for standard solutions were 5 and 20 μg kg^?1 respectively, which are markedly lower than the maximum residue limit. Using simple extraction methods, recoveries from fortified beef, pork and chicken samples were 43.4–62.3%. This novel method also enabled approximate quantification of enrofloxacin concentration: the enroMP signal intensity decreased with increasing enrofloxacin concentration. Because of its sensitivity, specificity, simplicity and rapidity, the method described herein will facilitate the detection and approximate quantification of enrofloxacin residues in foods in a high-throughput manner.     

Distribution of semduramicin in hen eggs and tissues after administration of cross-contaminated feed

Semduramicin is an ionophore coccidiostat used in the poultry industry as a feed additive. Cross-contamination of feeds for non-target animals with semduramicin is unavoidable. However, it is not known whether undesirable residues of semduramicin may occur in food after cross-contaminated feed is administered to animals. The aim of the work was to determine the levels of semduramicin in hen eggs (yolks and albumen) and tissues (liver, muscle, spleen, gizzard, ovarian yolks and ovaries) after administration of feed contaminated with 0.27 mg kg^?1 of this coccidiostat. The residues were determined using LC-MS/MS. The distribution pattern confirmed the high lipophilicity of semduramicin. Residues were found mainly in egg yolks (28.8 µg kg^?1), ovarian yolks (19.5 µg kg^?1) and liver (2.57 µg kg^?1), while hens’ muscle was free from semduramicin (LOD = 0.1 µg kg^?1). Among edible tissues, the maximum level (2 µg kg^?1) was exceeded only in the liver.     

The Modified New Two Plates Test for Detecting Tetracycline,Beta-Lactam,and Sulfonamide Antibiotic Residues in Kidney and Muscle of Cattle Slaughtered in North-East Benin

In Benin, veterinary antibiotics are widely used for cattle breeding. This livestock contributes to 57% of the locally produced meat. The aim of this study was to assess the impact of the large use of antibiotics by determining the contamination level with antibiotic residues in bovine meat, in North Benin. Kidney and muscle samples taken from 50 bovine carcasses in the 2 main slaughterhouses of Parakou were analyzed for the presence of antibiotic residues by a screening method modified from the “New Two Plates Test” (NTPT), to identify tetracyclines, sulfonamides, and beta-lactam groups of antibiotics. Thirteen kidney and muscle samples were subjected to liquid chromatography coupled to tandem mass spectrometry analysis for the confirmation of tetracycline and sulfonamide residues. After modified NTPT screening, tetracycline residues were identified in 54% of cattle carcasses while beta-lactam and sulfonamide residues were present, respectively, in 2 and 6% of sampled animals. The LC-MS/MS analysis confirmed the presence in the kidney tissue of oxytetracycline, epi-oxytetracycline, tetracycline, and epi-tetracycline at maximum levels, respectively, of 1380, 350, 190, and 230 μg kg^?1. Sulfamethazine residues were confirmed in one of cattle carcass at very high levels of 3900 μg kg^?1 in kidney and 2220 μg kg^?1 in muscle. Antibiotic residue levels were found above the maximum residue limit applied in the European legislation in 38% of the carcasses subjected to the LC-MS/MS analysis. These high levels of contamination with antibiotic residues are a potential threat for the health of consumers, and are of concern regarding the selection of antibiotic-resistant bacteria in animals and humans.     

LC-MS/MS-based determination of chloramphenicol,thiamphenicol, florfenicol and florfenicol amine in poultry meat from the Punjab-Pakistan

A simple, reliable and sensitive liquid chromatography-tandem mass spectrometry-based confirmatory method was redeveloped and validated for the simultaneous determination of chloramphenicol, thiamphenicol, florfenicol and florfenicol amine in chicken muscles. The analytes were extracted from minced chicken muscle with acetonitrile and ammoniated water mixture. A second extraction with ethyl acetate was followed by evaporation and dissolution of the residue in ammoniated methanol before defatting with n-hexane. Finally, the extract was further cleaned up by dispersive solid phase extraction using C-18 end-capped dispersive material. The validation protocol was adapted from the European Commission Decision 2002/657/EC and all the performance characteristics were successfully satisfied. The recoveries of all the analytes were found to be in the range of 86.4–108.1% and the precision values, within day and between days, ranged from 2.7% to 11% and 4.4% to 16.3%, respectively. The method was tested in various incurred samples and applied to analyse a wide range of random poultry market samples (n = 120) collected from three cities of the Punjab, Pakistan. Chloramphenicol and florfenicol residues were detected at low levels in less than 11% of the samples. Chloramphenicol was detected only in 4 samples with the concentration range of 0.17–0.477 µg kg^–1, whereas the levels of florfenicol/florfenicol amine residues detected in 9 samples ranged from 8.7 to 32.8 µg kg^–1. Moreover, most of the florfenicol residues were identified as tissue bound, extractable only after strong acid hydrolysis.