Development of an HPLC multi-residue method for the determination of ten quinolones in bovine liver and porcine kidney according to the European Union Decision 2002/657/EC

A sensitive multi-residue analytical method was developed for the determination of ten quinolones: enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, oxolinic acid, nalidixic acid, and flumequine in bovine liver and porcine kidney. A simple liquid extraction step followed by a solid phase extraction clean up procedure was applied for the extraction of quinolones from liver and kidney tissues. Recoveries of the extraction varied between 82 and 88% for bovine liver and 92 and 95% for porcine kidney. Separation was performed on an ODS-3 PerfectSil Target (250 x 4 mm) 5 microm analytical column at 25 degrees C. The mobile phase consisted of a mixture of TFA 0.1%-CH(3)CN-CH(3)OH, delivered at a flow rate of 1.2 mL/min according to a gradient program. Elution of quinolones and the internal standard (caffeine, 7.5 ng/microL) was complete within 27 min. Photodiode array detection was used for monitoring the eluants at 275 and 255 nm. The method was fully validated according to the European Union Decision 2002/657/EC, determining linearity, selectivity, decision limit, detection capability, accuracy, and precision. The LODs of the specific method of quinolone determination in bovine liver varied between 3 and 7 microg/kg and in porcine kidney between 3 and 4 microg/kg.     

Confirmatory method for macrolide residues in bovine tissues by micro-liquid chromatography-tandem mass spectrometry

A new confirmatory method for three macrolides (tylosin, tilmicosin and erythromycin) in bovine muscle, liver and kidney by micro-LC-MS-MS using an atmospheric pressure ionisation source and an ionspray interface has been developed. Roxithromycin was used as internal standard. The molecular related ions, [M+2H]2+, at m/z 435 for tilmicosin, and [M+H]+, at m/z 734 and 916 for erythromycin and tylosin, respectively, were the precursor ions for collision-induced-dissociation and two diagnostic product ions for each macrolide were identified for the unambiguous confirmation by selected reaction monitoring LC-MS-MS. Precision values (relative standard deviations) were all below 14.9%, whereas the overall accuracy (relative error) ranged from -17.7 to -9.8% for tylosin, from -17.5 to -10.7% for tilmicosin and from -19.6 to -13.7% for erythromycin, in all the investigated bovine tissues. The limits of quantification were 30 (muscle) or 40 (liver, kidney) microg kg(-1), 20 (muscle) or 150 (liver, kidney) microg kg(-1), 50 (muscle, liver) or 80 (kidney) microg kg(-1), 20 (muscle, liver) or 50 (kidney) microg kg(-1) for tylosin, tilmicosin, erytromycin and roxithromycin, respectively.     

Simultaneous determination of 20 beta-agonists in pig muscle and liver by high-performance liquid chromatography/tandem mass spectrometry

A method was developed to determine 20 illegal residual beta-agonists in pork tissues, including muscle and liver simultaneously. The samples were hydrolyzed by beta-glucuronidase, purified by PCX SPE cartridges, and detected by HPLC coupled with electrospray ionization MS/MS operating in the positive ion mode. Matrix-fortified calibration was performed to compensate for the matrix effect and loss in sample preparation. Decision limit ranged from 0.05 to 0.23 microg/kg in muscle and 0.05 to 0.57 microg/kg in liver. Decision capacity ranged from 0.11 to 0.4 microg/kg in muscle and 0.16 to 0.79 microg/kg in liver. In Food Analysis Performance Assessment Scheme proficiency test 0287, a pig liver test material containing 13 beta-agonists was analyzed using the method developed, and clenbuterol and ractopamine were confirmed as being present. Z-scores for clenbuterol and ractopamine were 0.2 and 0.6, respectively.     

Validated method for determination of ultra-trace closantel residues in bovine tissues and milk by solid-phase extraction and liquid chromatography-electrospray ionization-tandem mass spectrometry

A liquid chromatographic-electrospray ionisation-tandem mass spectrometry method (LC-ESI-MS/MS) with solid extraction was developed and validated for the detection and determination of closantel residues in bovine tissues and milk. An acetonitrile-acetone mixture (80:20, v/v) was used for one-stage extraction of closantel residues in bovine tissues and milk samples, and the extract was cleaned by solid phase extraction with Oasis MAX cartridges. The mass spectrometer was operated in multiple reactions monitoring mode with negative electrospray interface. The limits of detection in different matrices were in the range of 0.008-0.009 microg/kg. The overall recoveries for bovine muscle, liver, kidney and milk samples spiked at four levels including MRL were in the range of 76.0-94.3%. The overall relative standard deviations were in the range of 3.57-8.61%. The linearity is satisfactory with a correlation coefficient (r(2)) of 0.9913-0.9987 at both concentration ranges of 0.02-100 microg/kg and 200-5000 microg/kg. The method is capable of identifying closantel residues at > or =0.02 microg/kg levels and was applied in the determination of closantel residues in animal origin foods.     

高效液相色谱-串联质谱法测定猪组织中的土拉霉素

建立了高效液相色谱-串联质谱法测定土拉霉素在猪肝脏、肾脏、肌肉、皮脂和肺脏中的残留检测方法,并初步探讨了土拉霉素的基质效应.样品用乙腈提取,涡旋振荡离心后经正己烷脱脂,C18固相萃取柱净化后,40℃氮气吹干,用50%乙腈定容.以Penomenex Luna C18柱为色谱柱,乙腈-2 mmol,/L乙酸铵水溶液(含0....     

Determination of eight sulfonamides in bovine kidney by liquid chromatography/tandem mass spectrometry with on-line extraction and sample clean-up

A sensitive, high performance liquid chromatography/tandem mass spectrometric (i.e. mass spectrometry/mass spectrometry; LC/MS/MS) method with on-line extraction and sample clean-up for the screening and confirmation of residues of sulfonamides in kidney is described. The sulfonamides are extracted from homogenized kidney with methanol. After centrifugation of the extract, an aliquot of the extract is directly injected on the LC/MS/MS system with further extraction and clean-up of the sample on-line. Detection of the analytes was achieved by positive electrospray ionization (ESI) followed by multiple reaction monitoring. For each sulfonamide the collisional decomposition of the protonated molecule to a common, abundant fragment ion was monitored. The method has been validated for sulfadimethoxine, sulfaquinoxaline, sulfamethazine, sulfamerazine, sulfathiazole, sulfamethoxazole, sulfadiazine and sulfapyridine. Calibration curves resulting from spiked blank kidney samples at the 10-200 microg/kg level showed good linear correlation. At the level of 50, 100 and 200 microg/kg both within- and between-day precision, as measured by relative standard deviation (RSD), were less than 16%. The limits of detection (LODs) ranged from 5 to 13.5 microg/kg. The recoveries ranged from 78 to 82%. The procedure provides a rapid, reliable and sensitive method for the determination of residues of sulfonamides in bovine kidney. The advantage of this method over existing methods is its decreased sample preparation and analysis time, which makes the method more suitable for routine analysis.     

A quantitative method for residues of macrolide antibiotics in porcine kidney by liquid chromatography/tandem mass spectrometry

An LC/MS/MS-based multiresidue quantitative method was developed for the macrolides erythromycin A, neospiramycin I, oleandomycin, spiramycin I, tilmicosin, and tylosin A in porcine kidney tissues. The Canadian Food Inspection Agency (CFIA) had as part of its analytical scope an LC/UV method for quantification of residues of two macrolide antibiotics, tilmicosin and tylosin A, in the kidney, liver, and muscle of cattle, swine, and poultry. The method could not reliably detect concentrations below 10 microg/kg. To increase the scope of the CFIA's analytical capabilities, a sensitive multiresidue quantitative method for macrolide residues in food animal tissues was required. Porcine kidney samples were extracted with acetonitrile and alkaline buffer and cleaned-up using silica-based C18 SPE cartridges. Sample extracts were analyzed using LC/MS/MS with positive electrospray ionization. Fitness for purpose was verified in a single-laboratory validation study using a second analyst. The working analytical range was 5 to 50 microg/kg. LOD and LOQ were 0.5 to 0.6 microg/kg and 1.5 to 3.0 microg/kg, respectively. Limits of identification were 0.5 to 2.0 microg/kg. Relative intermediate precisions were 8 to 17%. Average absolute recoveries were 68 to 76%.     

Application of ion-exchange cartridge clean-up in food analysis. VI. Determination of six penicillins in bovine tissues by liquid chromatography-electrospray ionization tandem mass spectrometry

A multiresidue analytical method was developed for the quantification of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine tissues using liquid chromatography- electrospray ionization tandem mass spectrometry (LC-ESI MS/MS) with a multiple reaction monitoring technique. Using the deuterated PCG and NFPC as internal standard was effective for improvement of repeatability and accuracy. We chose [M-H-141]- as a monitor ion of MRM analysis and [M-H]- as a precursor ion for each penicillin. Combination of an ion-exchange cartridge clean-up and ion-pair LC enable us to determine the residual penicillins using the standard curves made from standard solutions without the influence of sample matrix on the MS. The average recoveries of PCG, PCV, MPIPC, MCIPC, NFPC and MDIPC from bovine liver, kidney and muscle at the same concentrations as the tolerance levels of PCG (50 microg/kg) ranged from 77 to 101% with the coefficients of variation ranging from 0.7 to 4.2% (n = 5). The limits of quantification for the six penicillins were 2-10 microg/kg in bovine muscle, liver and kidney (S/N ratio >10).     

Multilaboratory trial for determination of ceftiofur residues in bovine and swine kidney and muscle,and bovine milk

A multilaboratory trial for determining ceftiofur-related residues in bovine and swine kidney and muscle, and bovine milk was conducted following regulatory guidelines of the U.S. Food and Drug Administration, Center for Veterinary Medicine. The methods convert all desfuroylceftiofur-related residues containing the intact beta-lactam ring to desfuroylceftiofur acetamide to establish ceftiofur residues in tissues. Four laboratories analyzed 5 sets of samples for each tissue. Each sample set consisted of a control/blank sample and 3 control samples fortified with ceftiofur at 0.5 Rm, Rm, and 2 Rm, respectively, where Rm is the U.S. tolerance assigned for ceftiofur residue in each tissue/matrix: 0.100 microg/mL for milk, 8.0 microg/g for kidney (both species), 1.0 microg/g for bovine muscle, and 2.0 microg/g for swine muscle. Each sample set also contained 2 samples of incurred-residue tissues (one > Rm and one < Rm) from animals treated with ceftiofur hydrochloride. All laboratories completed the method trial after a familiarization phase and test of system suitability in which they demonstrated > 80% recovery in pretrial fortified test samples. Results showed that the methods met all acceptable performance criteria for recovery, accuracy, and precision. Although sample preparation was easy, solid-phase extraction cartridge performance must be carefully evaluated before samples are processed. The liquid chromatography detection system was easily set up; however, the elution profile may require slight modifications. The procedures could clearly differentiate between violative (> Rm) and nonviolative (< Rm) ceftiofur residues. Participating laboratories found the procedures suitable for ceftiofur residue determination.     

Determination of quinolones in animal tissues and eggs by high-performance liquid chromatography with photodiode-array detection

A rapid, specific reversed-phase HPLC method is described, with solid-phase extraction, for assaying five quinolones (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin and marbofloxacin) with confirmative diode-array detection in samples of bovine kidney, muscle and eggs. The least efficient extraction was marbofloxacin from kidney tissue (64%). The lower detection limit for each quinolone was: enrofloxacin and ciprofloxacin, 1 ng; norfloxacin and difloxacin, 2 ng; marbofloxacin, 4 ng injected. The intra-day relative standard deviations were lower than 7.9% and lower than 8.6% for inter-day assays. These results indicate that the developed method had an acceptable precision.     

Determination of ractopamine in swine, bovine, and turkey tissues by HPLC with fluorescence detection: first action 2011.22

A candidate LC method proposed by the Expert Review Panel (ERP) for ractopamine was evaluated in a single-laboratory validation (SLV) study. The matrixes examined included bovine liver, kidney, muscle, and fat; swine liver, kidney, muscle, and fat; and turkey liver and muscle. Solution standards were shown to provide a linear response with an unweighted regression. The method demonstrated acceptable precision (HorRat, values 0.25 to 1.38) and recovery (75.4 to 88.8%) in all fortified matrixes. Method precision was verified with incurred residue tissues (bovine liver, kidney, and muscle; swine liver, kidney, and muscle; and turkey liver and muscle), which yielded RSDr values below 16% for all tissues and below 7% for most tissues. Estimated LOQ values ranged from 1.8 to 20.7 ng/g and support the utility of the method in the range of the maximum residue limits or tolerances for the various tissues. The data satisfy the requirements of the AOAC Stakeholder Panel on Veterinary Drug Residue for SLV studies, and the method was adopted Official Methods ofAnalysis First Action 2011.22 by the AOAC ERP on Veterinary Drug Residues.     

Sensitive liquid chromatography/tandem mass spectrometry method for the determination of two novel highly lipophilic anticancer drug candidates in rat plasma and tissues

A simple and sensitive liquid chromatography/electrospray ionization tandem mass spectrometry (LC‐ESI‐MS/MS) method was developed and validated for determination of two highly lipophilic anticancer drug candidates, LG1980 and GH501, in rat plasma and tissues (liver, kidney and femur bones). LG1980 and GH501 were extracted from rat plasma and tissue homogenates using liquid–liquid extraction. The method provided a linear range of 1.0–200.0 ng/mL for GH501 in plasma and LG1980 in plasma and liver. For both analytes in other tissue homogenates the linear range was 2.0–400.0 ng/mL. The method was validated with precision within 15% relative standard deviation, accuracy within 15% relative error and a consistent recovery. This method has been successfully applied in two preclinical studies for LG1980 and GH501 to determine their concentrations in rat plasma, liver, kidney and bone over 24 h after intravenous injection of compounds.     

Multiresidue method for simultaneous determination of ten quinolone antibacterial residues in multimatrix/multispecies animal tissues by liquid chromatography with fluorescence detection: single laboratory validation study

Quinolone antibacterials are veterinary drugs authorized for use in food animal production. The analysis of residual amounts of drugs in food from animal origin is important for quality control of products for consumers. For this purpose, Maximum Residue Limits (MRLs) have been set up by a European Union Council Regulation on Veterinary Drug Residues (No. 90/2377/EEC and subsequent), and 8 quinolones received MRLs at concentration levels depending on both the matrix and the animal species of interest. A method was developed for screening and confirming 10 quinolone residues (ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, flumequine, marbofloxacin, nalidixic acid, norfloxacin, oxolinic acid, sarafloxacin) in a wide variety of matrixes of different animal species. It involves extraction of the residues from the biological tissues/fluids by acidic aqueous solution, centrifugation and filtration prior to injection on a C18 narrow-bore column, and detection through a 3-step-mode fluorescence detector. The method was validated during a 2-week study for a set of 8 species-matrixes (i.e., bovine raw milk, bovine muscle, porcine muscle, porcine kidney, porcine liver, fish flesh and skin, poultry muscle, whole egg). Residues were quantified down to 15 microg/kg with limits of detection and quantitation ranging from 4 to 11 and 13 to 36 microg/kg, respectively, which are sufficient compared to the wide range of MRLs set for these substances (from 30 microg/kg for danofloxacin in milk to 1900 microg/kg for difloxacin in poultry liver). The limit of performance of the method in terms of CCalpha and CCbeta, the critical concentrations stated in the Decision No. 2002/657/EC and the ISO Standard No. 11843, has been calculated for the authorized (MRL) substances but only estimated in the case of the nonauthorized (non-MRL) substances.     

Simultaneous determination of betamethasone and dexamethasone residues in bovine liver by liquid chromatography/tandem mass spectrometry

In this study a new method for the simultaneous confirmation of betamethasone and dexamethasone residues in bovine liver is presented. A Quattro LCZ triple quadrupole mass spectrometer, equipped with an atmospheric pressure ionization (API) source, was coupled to a high performance liquid chromatograph (HPLC) system. Spiked liver samples were first extracted with acetonitrile, and the extracts were purified on C-18 columns. LC separations were performed on a Hypercarb column, with acetonitrile/water (90:10, v/v, +0.3% formic acid) as the mobile phase. Retention times for dexa- and betamethasone were 6.60 and 8.50 min, respectively. Fluorometholone had a retention time of 6.70 min and was used as the internal standard. The detection of the analytes was performed in the multiple reaction monitoring (MRM) mode. The assay was linear over the range of 0.5 to 8 microg/kg for both analytes. The estimated determination limits were 0.2 microg/kg for both beta- and dexamethasone and the quantification limits were 0.4 microg/kg for dexamethasone and 0.3 microg/kg for betamethasone. Analysis precision at 1, 2 and 4 microg/kg was lower than 6.1% (relative standard deviation, RSD) and accuracy was at least 97.5%. Recoveries at 1, 2 and 4 microg/kg ranged between 56 and 69%.     

Quantitative analysis of penicillins in porcine tissues, milk and animal feed using derivatisation with piperidine and stable isotope dilution liquid chromatography tandem mass spectrometry

Penicillins are used universally in both human and veterinary medicine. The European Union (EU) has established maximum residue levels (MRLs) for most ß-lactam antibiotics in milk and animal tissues and included them in the National Residue Monitoring Programs. In this study, a novel method is described for the determination and confirmation of eight penicillins in porcine tissues, milk and animal feed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). To prevent degradation of penicillin residues during workup, a derivatisation procedure was developed, by which penicillins were converted to stable piperidine derivatives. Deuterated piperidine derivatives were synthesised for all relevant penicillins, enabling the use of isotope dilution for accurate quantification. Penicillin residues were derivatised in the crude extract with piperidine and isolated using solid-phase extraction. The penicillin piperidine derivatives were determined by LC–MS/MS. The method was validated at the current MRLs, which range from 25–300 µg kg^?1 in muscle and kidney to 4–30 µg kg^?1 in milk as well as at the target value of 100 µg kg^?1 chosen for animal feed, according to the EU requirements for a quantitative confirmatory method. Accuracy ranged from 94–113% (muscle), 83–111% (kidney) and 87–103% (milk) to 88–116% (animal feed). Intra-day precision (relative standard deviation (RSD)_r) ranged from 5–13% (muscle, n?=?18), 4–17% (kidney, n?=?7) and 5–18% (milk, n?=?7) to 11–32% (animal feed, n?=?18). Inter-day precision (RSD_RL, n?=?18) ranged from 6–23% (muscle) to 11–36% (animal feed). From the results, it was concluded that the method was fit for purpose at the target MRLs in animal tissue and target levels for animal feed.     

Simultaneous determination of residues of dipyrone and its major metabolites in milk, bovine muscle, and porcine muscle by liquid chromatography/mass spectrometry

A new liquid chromatography/mass spectrometry (LC/MS) method for the determination of dipyrone (DIP) and the DIP-related residues 4-formylaminoantipyrine (FAA), 4-aminoantipyrine (AA), and 4-methylaminoantipyrine (MAA) in milk, bovine muscle, and porcine muscle is presented. The analytes are extracted from the sample with methanol and defatted with hexane. The methanol extracts are then concentrated and injected into the LC system. Compounds are determined by reversed-phase LC using an Inertsil ODS-3 column with ammonium formate-acetonitrile mobile phase and MS detection using positive-ion electrospray ionization. Calibration curves were linear between 0.02 and 0.20 microg/g matrix equivalent concentration for FAA, AA, and MAA, and between 0.2 and 2.0 microg/g for DIP. The relative standard deviations for measurements by the proposed method were <11% for milk and porcine samples, with slightly greater variability for bovine samples. Average recoveries ranged from 82 to 128%, depending on the compound and matrix involved. The method detection limits of FAA, AA, and MAA were <0.02 microg/g for all matrixes tested, while those of DIP were <0.13 microg/g. The proposed method is rapid, simple, and specific, allowing a single analyst to easily prepare over 20 samples in a regular working day.     

A new approach to the analysis of nicarbazin and ionophores in eggs by HPLC/MS/MS

An HPLC/MS/MS method has been developed and validated for the quantification and confirmation of nicarbazin and ionophores (lasalocid, monensin, salinomycin, and narasin) in eggs. Nicarbazin is determined in the negative electrospray mode with a basic mobile phase that supports creation of negative ions. Consequently, our ability to maintain instrument sensitivity over time has significantly improved. The analysis of the ionophores is done in the positive electrospray mode using ammonium buffer for HPLC separation. Monitoring ammonium adduct parent ions resulted in enhanced sensitivity and better reproducibility of the ionophore analysis. The validation of this improved HPLC/MS/MS method for the detection of nicarbazin and the ionophores demonstrated excellent precision of below 10% RSD and lower LOD values (microg/kg) for nicarbazin (0.018), lasalocid (0.015), monensin (0.015), salinomycin (0.033), and narasin (0.039).     

A new high-performance liquid chromatographic/electrospray ionization tandem mass spectrometric method for the simultaneous determination of cyclophosphamide, methotrexate and 5-fluorouracil as markers of surface contamination for occupational exposure monitoring

A new high-performance liquid chromatographic/electrospray ionization tandem mass spectrometric (HPLC/ESI-MS/MS) method was developed for the simultaneous quantification of 5-fluorouracil (5FU), methotrexate (MTX) and cyclophosphamide (CP) in environmental samples. These compounds, commonly used in the treatment of cancer, are recognized as genotoxic. In order to estimate the occupational exposure of hospital personnel handling these drugs, wipe samples were taken from the working surfaces and directly analyzed (with trophosphamide as internal standard) using a reversed-phase capillary column and MS/MS detection. This is the first HPLC/MS/MS method for the simultaneous determination of 5FU, MTX and CP. The present method offers high sensitivity, with detection limits of 1.1 microg l(-1) for MTX and CP and 33.3 microg l(-1) for 5FU, avoiding any sample preconcentration procedure. Rapidity, specificity, high accuracy (mean values between 92.4 and 99.9%) and precision (mean RSD values between 3.4 and 12.1%) make the method suitable for the routine determination of these three antineoplastic drugs.     

Determination of pesticides in apples by liquid chromatography with electrospray ionization tandem mass spectrometry and estimation of measurement uncertainty

A liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) method was developed and validated to determine 90 pesticides in apple samples. MS/MS data acquisition was achieved by applying multiple-reaction monitoring of 2 fragment ion transitions to provide a high degree of sensitivity and selectivity for both quantitation and confirmation. Matrix-matched standard calibration curves with the use of isotopically labeled standards (or a chemical analog) as internal standards were used to achieve the best accuracy for the method. Both a conventional method validation procedure and a designed experiment were applied to study the accuracy and precision of the method. A compiled computer program that provided a semiautomated procedure for handling a large number of calculations was used to calculate the overall recovery, intermediate precision, and measurement uncertainty (MU). In general, the overall recoveries from samples spiked at levels of 10, 50, and 80 microg/kg, ranged from 60.8 to 121.1%, intermediate precision was <10%, and MUs were <30%. Poor accuracy and/or repeatability was observed for pyridate and etofenprox. The method limits of detection based on a signal-to-noise ratio of >3 were usually <1 microg/kg (ppb), except those for aldicarb sulfoxide and pyridaphenthion, which were about 5 microg/kg.     

Determination of β-Blockers in Bovine and Porcine Tissues and Bovine Milk by High-Performance Liquid Chromatography – Tandem Mass Spectrometry

The illicit use of β-blockers in food-producing animals may induce the presence of these compounds in meat and milk. The presence of β-blockers in these foods is a safety issue. A simple and economic high-performance liquid chromatography – tandem mass spectrometry method was developed and validated for β-blockers in bovine and porcine muscle, kidney, liver, and bovine milk. The focus of the study was on the detection and quantitation of acebutolol, atenolol, betaxolol, carazolol, metoprolol, nadolol, penbutolol, and propranolol. Homogenized tissues were digested with glucuronidase/aryl sulfatase to release the analytes that were extracted with acetonitrile and purified using matrix solid-phase dispersion. For residues in milk, acidolysis and extraction utilized trichloroacetic acid and acetonitrile and the samples were purified using mixed-mode cation exchange solid phase extraction. Standard curves generated using homogenized tissues and milk matrices were linear with correlation coefficients exceeding 0.99. The limits of detection and quantification were 1?μg/kg and 2.5?μg/kg, respectively, for all analytes in the meat tissues. The corresponding values for milk were 0.2?μg/kg and 0.5?μg/kg. The average recoveries of the spiked samples were from 84.4 to 114.2% with the standard deviations of the intra- and inter-day assays from 2.0 to 14.6% and 2.9 to 18.7%, respectively. This method is simple, economical, and time-saving for the determination of β-blockers in bovine tissue, porcine tissue, and bovine milk.