Determination of nequinate and buquinolate in livestock products using liquid chromatography-tandem mass spectrometry

We studied the simultaneous determination of nequinate and buquinolate, which are used as feed additives to prevent coccidiosis, by means of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The sample was extracted with acetonitrile, then loaded onto an HLB mini-column with 20% methanol. After clean-up with 20% methanol, the analytes were eluted with acetonitrile-methanol (1 : 1). The coccidiostats in the purified samples were determined using ESI-MRM mode LC-MS/MS with a sample matrix calibration curve. Mean recoveries of nequinate and buquinolate from 8 kinds of livestocks samples (chicken muscle, chicken liver, chicken heart, swine muscle, swine heart, cattle muscle, sheep muscle, egg) were in the range of 89.5% to 108.6%, and the relative standard deviation values were <20% (n=10) at the levels of 0.01 μg/g and 0.05 μg/g, respectively. The limits of quantification of these compounds were 0.001 μg/g in each sample.     

Determination and Confirmation of Chloramphenicol Residues in Swine Muscle and Liver

ABSTRACT: Average high-performance liquid chromatography (HPLC) recoveries of chloramphenicol (CAP) in swine muscle and liver ranged from 91.3 to 94.2% and 93.1 to 103.7%, respectively, with coefficients of variation ranging from 1.4 to 4.3% and 1.1 to 11.2% for each tissue sample. The method described was repeatable and reproducible in swine muscle and liver, with a limit of quantification of 15 ng/mL and a limit of detection estimated at 5 ng/mL. The limit of identification of CAP was 25 ng/mL, 5ng/mL, and 20 ng/mL for HPLC/PDA, GC/MS selected ion monitoring (SIM), and LC/MS analysis, respectively.     

Simultaneous determination of quinolones in foods by LC/MS/MS

A simple method was developed for the simultaneous determination of seven quinolones (enoxacin, ofloxacin, ciprofloxacin, danofloxacin, lomefloxacin, enrofloxacin and sarafloxacin) in foods using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The seven quinolones were extracted with acetonitrile containing 0.2% formic acid, and the extracted solution was cleaned up on a C18 cartridge. The extract was diluted with 5 mmol/L IPCC-MS3 for injection into the LC-ESI-MS/MS. The LC separation was carried out on an ODS column with gradient elution of 5 mmol/L IPCC-MS3-acetonitrile as the mobile phase. Mass spectral acquisition was done in the positive ion mode by applying selected reaction monitoring (SRM). The recoveries of the seven quinolones were mostly greater than 60% from foods fortified at 10 ng/g. The detection limits in foods were 2 ng/g for enoxacin and ciprofloxacin, and 1 ng/g for the other drugs. Twenty cattle muscle, 7 swine muscle, 9 chicken muscle, 16 milk, 19 prawn and 20 broiled eel samples from retail markets were analyzed by this method. Enrofloxacin and its metabolite ciprofloxacin were detected in 9 broiled eel at the level of trace (tr)-34 ng/g and tr-10 ng/g, respectively.     

Determination method for ractopamine in swine and cattle tissues using LC/MS

Simple and reliable methods using LC/MS have been developed for the determination of the beta-agonist ractopamine in swine and cattle tissues. Ractopamine was extracted with ethyl acetate from muscle and liver, and the ethyl acetate layer was evaporated to dryness. The residue was purified by partition with acetonitrile/n-hexane. In the case of fat, ractopamine was extracted and purified by partition with acetonitrile/n-hexane. The resulting acetonitrile solutions were evaporated to dryness. The residue was dissolved in methanol, and subjected to LC/MS. The LC separation was performed on a Wakosil-II 3C18HG column (150 x 3 mm i.d.) in isocratic mode with 0.05% trifluoroacetic acid-acetonitrile (80:20) as a mobile phase at a flow rate of 0.4 mL/min. The MS detection was performed in the selected ion recording (SIR) mode, with detection of the M + H+ ion of ractopamine (m/z 302) produced by electrospray ionization (ESI). The mean recoveries of the drug from swine muscle (0.01 microg fortified), fat (0.01 microg fortified) and liver (0.04 microg/g fortified) were 99.7%, 99.5% and 100.8%, and those from cattle samples were 108.3%, 97.0% and 109.4%, respectively. The relative standard deviations (RSDs) ranged from 0.1% to 9.5%. The limit of quantification (LOQ) of the drug was 1 ng/g.     

Determination of carbadox metabolites, quinoxaline-2-carboxylic acid and desoxycarbadox, in swine muscle and liver by liquid chromatography/mass spectrometry

A sensitive and selective method using liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) for the determination of carbadox metabolites, quinoxaline-2-carboxylic acid (QCA) and desoxycarbadox (Desoxy-CDX), in swine muscle and liver has been developed. The LC separation was performed on a Cadenza CD-C18 column (10 cm x 2 mm i.d.) with a gradient system of 0.01% acetic acid-acetonitrile as the mobile phase at a flow rate of 0.2 mL/min. Negative ionization produced the [M-H]- molecular ion of QCA. On the other hand, the positive mode produced the [M+H]+ ion of Desoxy-CDX. The calibration graphs for QCA and Desoxy-CDX were rectilinear from 0.01 to 0.5 ng with selected ion monitoring (SIM). The drugs were extracted with 0.3% metaphosphoric acid-methanol (7:3), and the extracts were cleaned up on an Oasis HLB cartridge (60 mg) and by liquid-liquid extraction. The recoveries of QCA and Desoxy-CDX from swine muscle and liver fortified at 2.5 and 5 ng/g were 70.2-86.3%, and the detection limits were 1 ng/g for both drugs.     

Development of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of glucocorticoid residues in edible tissues of swine,cattle, sheep,and chicken

A confirmatory and quantitative method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine the presence of eight glucocorticoids (prednisone, prednisolone, hydrocortisone, methylprednisolone, dexamethasone, betamethasone, beclomethasone, and fludrocortisone) in the muscles and livers of swine, cattle, and sheep and the muscle of chicken is described. After deconjugation in alkali media, samples were extracted with ethyl acetate for glucocorticoids followed by solid-phase extraction clean-up and reconstitution in the LC mobile phase. The hydrolysis procedure with sodium hydroxide was used to reduce handling time. A single-step solid-phase extraction method was optimized which is suitable for the clean-up of the compounds of interest in many diverse tissue matrices. LC separations were performed on a C₁₈ column with gradient elution using acetonitrile and water (containing 0.2% formic acid) and the two epimers betamethasone and dexamethasone were successfully separated. LC-electrospray ionization (ESI)-MS/MS in negative mode with selected reaction monitoring (SRM) mode was performed to improve method sensitivity and reduce matrix interference. Two SRM transitions were used for each compound. The recovery of glucocorticoids spiked at levels of 0.5–16 µg kg^?1 ranged from 55% to 107%; the between-day relative standard deviations were no more than 15%. The limits of quantification were 0.5–2.0 µg kg^?1 in muscle and 1–4 µg kg^?1 in liver. The optimized procedure was successfully applied to monitor the food at the 2008 Summer Olympics Games in Beijing, China, demonstrating the method to be simple, fast, robust, and suitable for identification and quantification of glucocorticoids residues in foods of animal origin.     

Residue analysis of metoclopramide in bovine and swine tissues by HPLC and administration experiment

A reversed-phase ion-pair HPLC method with ultraviolet detection has been developed for determination of metoclopramide (MCP) in bovine and swine muscle, liver, kidney, fat and intestine. MCP was extracted from samples with acetonitrile, and the extracts were cleaned up on an Oasis HLB cartridge (60 mg) after liquid-liquid extraction. The limit of detection of MCP was 0.002 microg/g and the limit of quantitation was 0.007 microg/g. Recoveries of MCP spiked at 0.03 ppm ranged from 74.1 to 93.3% for bovine tissues and from 86.1 to 92.7% for swine tissues. The present method was used for the analysis of bovine and swine tissues 1 day after withdrawal following drug administration. The MCP concentrations in all tissues were lower than the Japanese provisional MRLs.     

快速高分离液相色谱- 串联质谱法对肌肉组织中糖皮质激素残留的检测

建立采用快速高分离液相色谱- 串联质谱(UHPLC-MS2)技术检测肌肉组织中糖皮质激素残留的方法。样品经乙酸乙酯提取,固相萃取法净化,以C18 色谱柱(150mm × 2.1mm,3.5μm)为分离柱,水- 乙腈- 甲酸溶液为流动相进行梯度洗脱,快速高分离液相色谱- 串联质谱ESI 负离子模式进行检测。该方法线性范围为0.5～5ng/mL,线性相关系数R2 ≥ 0.9963,检测限：倍氯米松为1.0μg/kg,氢化可的松为2.0μg/kg,其余均为0.5μg/kg。平均回收率为82.75%～91.87%,相对标准偏差≤ 4.43%(n=5)。     

Simultaneous determination of five penicillins in muscle,liver and kidney from slaughtered animals using liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A simple and rapid method for the simultaneous determination of five penicillins (ampicillin, penicillin G, penicillin V, oxacillin and cloxacillin) in muscle, liver and kidney tissues using high-performance liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) was developed. Mass spectral acquisition was done in the negative ion mode by applying selected reaction monitoring (SRM). The five penicillins were extracted with water, and the extracted solution was cleaned up on a C18 cartridge. Phenethicillin was added as an internal standard, and the extract was diluted with water for injection into the LC-ESI-MS/MS. The recoveries of the five penicillins were in the range of 77.3-99.8% from muscle, liver and kidney fortified at 10-250 ng/g. The detection limits for ampicillin were 6 ng/g in muscle and kidney and 15 ng/g in liver. For penicillin G and penicillin V, the detection limits were 2 ng/g in muscle and kidney and 5 ng/g in liver. For oxacillin and cloxacillin, the detection limits were 4 ng/g in muscle and kidney and 10 ng/g in liver. Twenty-three muscle, fourteen liver and twenty-two kidney samples from the markets were analyzed by this method. No penicillins were detected in any sample.     

Rapid and sensitive enzyme-linked immunosorbent assay and immunochromatographic assay for the detection of chlortetracycline residues in edible animal tissues

Two rapid and sensitive enzyme-linked immunosorbent assays (ELISA) and an immunochromatographic assay (ICA) for the detection of chlortetracycline (CTC) residues in edible animal tissues were developed based on a monoclonal antibody (MAb) produced by using the chlortetracycline-bovine serum albumin (CTC-BSA) conjugate as the immunogen. A total of 50% inhibiting concentration (IC(50)) of the modified ELISA was 0.66 ng ml(-1) and the recoveries from spiked chicken muscle and liver were 78.8-92.2% and 80.3-90.2%, respectively. The corresponding coefficient variations (CVs) were 3.2-9.5% and 6.5-10.2%. The detection limit was 0.06 ng g(-1) in chicken muscle and 0.07 ng g(-1) in liver. However, the detection limit of ICA was 0.12 ng ml(-1), and the recoveries in negative samples spiked at concentrations of 10, 50 and 100 ng g(-1) ranged from 79.0% to 88.6% for muscle samples and from 75.2% to 87.0% for liver samples. The cut-off values for the test lines were 80 ng g(-1) and the analysis can be completed within 5-10 min. Comparisons with an HPLC method were performed by testing 200 swine muscle samples and chicken muscle samples from local markets, and an agreement rate of 99.5% was obtained between the three methods.     

Determination of streptomycin and dihydrostreptomycin in meat by liquid chromatography/mass spectrometry

A sensitive and selective method using liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) for the determination of aminoglycoside antibiotics, streptomycin and dihydrostreptomycin, in meat has been developed. The LC separation was performed on a TSK-gel Super ODS column (10 cm x 2 mm i.d.) using 5 mmol/L heptafluoro-n-butyric acid (HFBA)-acetonitrile (88:12) as the mobile phase at a flow rate of 0.18 mL/min. The positive ionization produced typical [M + H]+ molecular ions of both drugs (streptomycin m/z 582; dihydrostreptomycin m/z 584). The calibration graphs for streptomycin and dihydrostreptomycin were rectilinear from 0.25 to 25 ng with selected ion monitoring (SIM). The drugs were extracted with 1% metaphosphoric acid, and the extracts were added to 2 mL of 0.1 mol/L heptanesulfonic acid. The solution was cleaned up on a Bond Elut C18 (500 mg) cartridge. The recoveries of streptomycin and dihydrostreptomycin from swine and bovine muscle fortified at 0.2 microgram/g were 73.2-82.6%, and the detection limits were 0.01 microgram/g for both drugs.     

石斑鱼中阿维菌素类药物多残留测定及食用安全风险评估

建立高效液相色谱-串联质谱同时定量检测石斑鱼血浆、肌肉组织、肝脏组织中阿维菌素、伊维菌素、甲氨基阿维菌素苯甲酸盐方法。样品经乙腈提取,碱性氧化铝固相萃取柱和LC-C18固相萃取柱串联净化,Thermo Hypersil Gold C18色谱柱分离,10 mmol/L乙酸铵-0.1%甲酸溶液和乙腈梯度洗脱,电喷雾正离子模式下以多反应监测方式检测,基质匹配法外标定量。分别以环境水体中阿维菌素上下限质量浓度(4、8 ng/mL)、伊维菌素上下限质量浓度(6、12 ng/mL)作为受试质量浓度开展生物富集、消除实验,并对石斑鱼的食用安全进行了风险评估。结果表明,阿维菌素和伊维菌素在2.5~200 ng/mL范围内,甲氨基阿维菌素苯甲酸盐在0.25~20 ng/mL范围内,线性回归系数均大于0.99。方法检出限分别为2.5、2.5、0.25 ng/mL(血浆),1、1、0.1μg/kg(肌肉组织),2.5、2.5、0.25μg/kg(肝脏组织),方法定量限分别为5、5、0.5 ng/mL(血浆),2、2、0.2μg/kg(肌肉组织),5、5、0.5μg/kg(肝脏组织)。3个添加量的平均回收率为74.6%~93.6%,日内相对标准偏差为2.3%~10.9%,日间相对标准偏差为9.2%~12.6%。阿维菌素、伊维菌素均属于非生物累积性物质,在石斑鱼体内代谢规律相同,均按一级动力学过程从体内消除。本研究条件下,环境水体中药物质量浓度是石斑鱼肌肉组织中药物残留质量浓度及消除时间的重要因素。为保证食用安全,环境水体中阿维菌素质量浓度达到4~8 ng/mL时,石斑鱼浸浴72 h后安全食用时间为22 d;环境水体中伊维菌素质量浓度达到6~12 ng/mL时,石斑鱼浸浴72 h后安全食用时间为39 d。     

Determination of Baclofen Residue in Muscle,Liver, Kidney and Fat of Swine by Liquid Chromatography-Tandem Mass Spectrometry

Baclofen was illegally used in veterinary clinical medicine as a growth-promoting agent. To date, few methods have been developed for the monitoring of baclofen in animal tissues. In this study, a sensitive and efficient liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to identify and quantify baclofen in the muscle, liver, kidney, and fat of swine was developed and validated. Baclofen was extracted from tissues with ammonium acetate buffer (pH 5.2) and isolated with isopropyl-ethyl acetate (4:6, v/v). Then, a solid phase extraction using MCX cartridge was used to clean up the extracts. The elution was evaporated to dryness and reconstituted with water/methanol (90:10 v/v). All samples were determined by LC-MS/MS system through positive ionization in a multiple reaction monitoring (MRM) mode. The proposed method was validated by evaluation of specificity, linearity, recovery, accuracy, precision, LOD, and LOQ values according to Commission Decision 2002/657/EC. Estimated limit of quantification for baclofen in the muscle, liver, kidney, and fat of this method was 1.00 μg/kg, respectively. The mean intra- and inter-day assay accuracies fell within a range 88.5–93.9% and 86.2–93.2%, respectively. The mean intra- and inter-day precisions were 1.78 and 4.95% (RSD < 15%), respectively. The proposed method has proved to be suitable for accurate quantitative determination of baclofen for residue analysis.     

Development of a Monoclonal Antibody-Based Immunochromatographic Assay Detecting Ractopamine Residues in Swine Urine

A lateral-flow immunochromatographic assay (LFIA) using monoclonal antibody was developed for the rapid detection of ractopamine residues in swine urine. The assay procedure could be accomplished within 5 min, and the results of this qualitative one-step assay were evaluated visually according to whether test lines appeared or not. When applied to the swine urines, the detection limit and the half maximal inhibitory concentration (IC₅₀) of the lateral-flow immunochromatographic test strip under an optical density scanner were calculated to be 0.1?±?0.013 and 0.71?±?0.056 ng/mL, respectively. The cut-off level was observed with the naked eye of 1 ng/mL for detection of ractopamine residue in swine urine. Parallel analysis of swine urine samples with ractopamine showed comparable results obtained from the LFIA and LC-MS/MS. Therefore, the described lateral-flow test strip can be used as a reliable, rapid and cost-effective on-site screening technique for the determination of ractopamine residues in swine urine.     

Determination of pindone in animal products, fishery products, and honey by LC-MS/MS

A sensitive and selective analytical method for the determination of the rodenticide pindone in animal products, fishery products, and honey by LC-MS/MS was developed. Pindone was extracted with acidified acetone, and the crude extract was purified by liquid-liquid partitioning, followed by silica gel and ODS column chromatography. LC separation was performed on an ODS column with methanol/water containing ammonium acetate as the mobile phase, and detection was carried out using tandem mass spectrometry (MS/MS) with electrospray ionization (ESI) in the negative mode. The average recoveries from fortified bovine muscle, bovine liver, bovine fat, chicken muscle, salmon, eel, freshwater clam, egg, milk, and honey spiked at 0.001 mg/kg were in the range of 76-92%, and the relative standard deviations were 4-8%. The limit of quantitation (S/N≥10) of the developed method was 0.001 mg/kg for all the tested foods.     

通过型固相萃取净化-超高效液相色谱-串联质谱法检测鸡肉中23种磺胺类药物残留

建立了通过型固相萃取净化超高效液相色谱-串联质谱法同时检测鸡肉中23种磺胺类药物残留的分析方法。鸡肉样品经80%乙腈溶液（含0.2%甲酸）提取,Oasis PRiME HLB固相萃取柱进行净化,用Waters Acquity UPLC CSH C18色谱柱（100 mm×2.1 mm,1.7 μm）分离,以甲醇和0.1%甲酸溶液为流动相梯度洗脱,电喷雾源正离子扫描及依赖保留时间的多反应监测模式下（Scheduled MRM）检测,外标法定量。结果表明:23种磺胺类药物在线性范围0.2~20 ng/mL上有良好的线性关系,相关系数均大于0.9996;检出限为0.1~2.0 μg/kg,定量限为0.25~5.0 μg/kg;在1.0、2.0、5.0 μg/kg三个加标水平上平均回收率为66.12%~99.83%,相对标准偏差（RSD,n=6）为0.72%~10.36%;该方法操作简单、灵敏度高、重现性好,适用于鸡肉中多种磺胺类药物残留的检测。     

Determination of glycarbylamide based on formation of nickel chelate

A new and simple analytical method for glycarbylamide (GB) based on the formation of nickel chelate was developed. The proposed method is as follows: sample solution is mixed with 0.08 mmol/L nickel nitrate in 0.2 mol/L carbonate buffer (pH 9.0), and the absorbance is measured at 290 nm. Under the optimal conditions, GB could be determined in the concentration range from 0.13 microg/mL to 2.6 microg/mL (r = 0.9999). Using this method for HPLC post column reaction, GB levels in chicken liver extracts could be determined. The recovery of GB was 79.4% (RSD=2.6%, n=3) and the quantitation limit was 30 ng/g. The apparent molar extinction coefficient (epsilon) of the GB-nickel complex was 8.5 x 10(3). The molar ratio of the complex is GB: nickel ion = 2:1.     

Development of monoclonal-based enzyme-linked immunosorbent assay and immunochromatographic assay for lasalocid and semduramicin

Monoclonal antibodies (MAbs) against lasalocid and semduramicin were prepared using keyhole limpet hemocyanin conjugates for the immunization of mice. With these MAbs, we developed quantitative enzyme-linked immunosorbent assay (ELISA) methods for lasalocid and semduramicin. The ELISAs were quantitative in the ranges of 0.1-50 ng/mL for lasalocid and 0.05-12.5 ng/mL for semduramicin, and showed 50% inhibition concentrations of 1.2 ng/mL for lasalocid and 0.5 ng/mL for semduramicin. The coefficient of variations (CV%) of lasalocid were 0.3-4.4% for intra-assay and 0.5-5.1% for inter-assay and those of semduramicin were 0.1-4.6% for intra-assay and 0.3-5.2% for inter-assay. The detection limits for lasalocid and semduramicin were 10 ng/g and 5 ng/g in chicken liver and muscle, respectively. Based on the immunochromatographic method, rapid test kits for lasalocid and semduramicin were also developed. With these kits, the detection limits of lasalocid were 50 ng/mL for standard solution and 125 ng/g for chicken muscle, and those of semduramicin were 10 ng/mL for standard solution and 100 ng/g for chicken muscle.     

TurboFlow在线净化-液相色谱-串联质谱法测定畜禽肉中20 种（氟）喹诺酮类兽药残留量

建立TurboFlow在线净化-液相色谱-串联质谱测定畜禽肉中20 种（氟）喹诺酮类药物（（Fluoro） quinolones,（F）QNs）残留量的分析方法。样品用甲醇-乙腈（1∶1,V/V）进行均质提取,Cyclone-p在线净化柱 净化富集提取液中的（F）QNs,然后将富集所得分析物洗脱,转至Hypersil Gold C8分析柱,经色谱分离后,用 串联质谱检测。结果表明：西诺沙星、伊诺沙星和丹诺沙星在0.2～20.0 ng/mL的线性范围内线性良好,其余17 种 （F）QNs在0.1～10.0 ng/mL的线性范围内线性良好,且R2均大于0.99;西诺沙星、伊诺沙星和丹诺沙星的定量限为 2 μg/kg,其余17 种（F）QNs为1 μg/kg;20 种（F）QNs在3 个水平的添加回收率为85.4%～108.2%,相对标准偏差 为4.04%～8.57%。方法简单、快速、回收率高、重复性好,适用于动物源食品中（F）QNs的定量及确证检测。     

LC-MS/MS法测定水基胶中的3种异噻唑啉酮类防腐剂

建立了测定水基胶中3 种异噻唑啉酮的液相色谱-串联质谱(LC-MS/MS)方法。水基胶样品经水萃取、离心后进行LCMS/MS 分析,内标法定量。结果表明:MI、CMI 在浓度范围2.5~250 ng/mL、BIT 在浓度范围5~500 ng/mL 内,线性关系良好(R2 ≥ 0.9996),3 个加标水平的加标回收率在96.3%~109.6% 之间,平均相对标准偏差(RSD)在1.5%~6.7% 之间,方法的检出限(LOD)和定量限(LOQ)分别为0.011~0.015 mg/kg 和0.035~0.051 mg/kg。该方法适用于水基胶中MI、CMI、BIT 的快速测定。