Development and validation of an immunochromatographic assay for the rapid detection of quinoxaline-2-carboxylic acid,the major metabolite of carbadox in the edible tissues of pigs

A new method was developed for the determination of quinoxaline-2-carboxylic acid, the marker residue of carbadox, in the edible tissues of food-producing animals using a colloidal gold probe-based immunochromatographic assay. The highly specific polyclonal antibody (PcAb), which was very sensitive to N-butylquinoxaline-2-carboxylic acid (BQCA) with an IC₅₀ value of 2.38?ng?ml^?1, was selected for the development of an immunochromatographic assay (ICA). Only 5?min were required to perform this assay; it had a visual detection limit of 25?ng?g^?1 for quinoxaline-2-carboxylic acid. The results of the analysis of quinoxaline-2-carboxylic acid in animal tissues using the immunochromatographic assay showed good agreement with those obtained by HPLC. In conclusion, the method was rapid and accurate for screening residues of carbadox in the edible tissues of food-producing animals.     

Development and validation of an indirect competitive enzyme-linked immunosorbent assay for monitoring quinoxaline-2-carboxylic acid in the edible tissues of animals

The feed drug additive carbadox is a suspected carcinogen and mutagen. To monitor effectively residues of carbadox in the edible tissues of food-producing animals, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) to detect quinoxaline-2-carboxylic acid, the marker residue of carbadox, was developed. Several haptens were synthesised and conjugated to the carrier protein. Nine female New Zealand white rabbits were immunised with the immunising conjugates to produce polyclonal antibodies according to the designed schemes of immunisation. The highly specific antibody that was very sensitive to N-butylquinoxaline-2-carboxamide with an IC(50) value of 7.75 μg l(-1) was selected for the development of an ic-ELISA. The standard curves based on the N-butylquinoxaline-2-carboxamide matrix calibration ranged from 0.2 to 51.2 μg l(-1). The decision limit and detection capability of the ic-ELISA were 0.60 and 0.83 μg kg(-1) for liver and 0.68 and 0.79 μg kg(-1) for muscle of swine, respectively. The recoveries were 57-108% with coefficients of variation of less than 20% when the quinoxaline-2-carboxylic acid was spiked into liver and muscle with the concentrations of 1.0-20.0 μg kg(-1). Excellent correlations between the results of the ic-ELISA and an HPLC method (r = 0.9956 - 0.9969) were observed for incurred tissues. These results suggest that the ic-ELISA is a sensitive, accurate and low-cost method that would be a useful tool for screening residues of carbadox in the edible tissues of food-producing animals.     

Development and validation of an indirect competitive enzyme-linked immunosorbent assay for monitoring quinoxaline-2-carboxylic acid in the edible tissues of animals

The feed drug additive carbadox is a suspected carcinogen and mutagen. To monitor effectively residues of carbadox in the edible tissues of food-producing animals, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) to detect quinoxaline-2-carboxylic acid, the marker residue of carbadox, was developed. Several haptens were synthesised and conjugated to the carrier protein. Nine female New Zealand white rabbits were immunised with the immunising conjugates to produce polyclonal antibodies according to the designed schemes of immunisation. The highly specific antibody that was very sensitive to N-butylquinoxaline-2-carboxamide with an IC₅₀ value of 7.75?µg?l^?1 was selected for the development of an ic-ELISA. The standard curves based on the N-butylquinoxaline-2-carboxamide matrix calibration ranged from 0.2 to 51.2?µg?l^?1. The decision limit and detection capability of the ic-ELISA were 0.60 and 0.83?µg?kg^?1 for liver and 0.68 and 0.79?µg?kg^?1 for muscle of swine, respectively. The recoveries were 57–108% with coefficients of variation of less than 20% when the quinoxaline-2-carboxylic acid was spiked into liver and muscle with the concentrations of 1.0–20.0?µg?kg^?1. Excellent correlations between the results of the ic-ELISA and an HPLC method (r?=?0.9956???0.9969) were observed for incurred tissues. These results suggest that the ic-ELISA is a sensitive, accurate and low-cost method that would be a useful tool for screening residues of carbadox in the edible tissues of food-producing animals.     

In vivo studies to highlight possible illegal treatments of rabbits with carbadox and olaquindox

For the treatment of rabbit dysentery and bacterial enteritis, veterinary practitioners often adopt veterinary medicinal products authorised for other food-producing species, but in some cases non-authorised drugs frequently used in the past, such as carbadox and olaquindox, might be illegally adopted. To verify the carbadox and olaquindox distribution and persistence in rabbit tissues, two independent in vivo studies were carried out. In the first study, 24 healthy rabbits received water medicated with carbadox at 100 mg l^?1 over a period 28 days, whereas in the second one, 24 healthy rabbits were administered water containing olaquindox at 100 mg l^?1. In each study rabbits were randomly assigned to four groups to be sacrificed respectively at 0, 5, 10 and 20 days from treatment withdrawal, for depletion studies. A control group of six animals was adopted for control and as a reservoir of blank tissues. Muscle and liver samples collected from each treated animal were stored at ?20°C pending the analysis. Sensitive and robust liquid chromatography-tandem mass spectrometry analytical methods were set up for the parent compounds and their main metabolites quinoxaline-2-carboxylic acid, desoxycarbadox and 3-methylquinoxaline-2-carboxylic acid to verify their residual. Data collected demonstrate that the combination of liver as target matrix, quinoxaline-2-carboxylic acid and 3-methylquinoxaline-2-carboxylic acid as marker residue and enzymatic digestion is strategic to evidence carbadox and/or olaquindox illegal treatments in rabbits, even 20 days after treatment withdrawal at concentration levels higher than 0.5 µg kg^?1. This findings suggests that liver should be proposed as target matrix for official control in national monitoring plan.     

Immunochromatographic Assay for Simultaneous and Quantitative Detection of 3-Methyl-Quinoxaline-2-Carboxylic Acid and Quinoxaline-2-Carboxylic Acid Residues in Animal Tissues Based on Highly Luminescent Quantum Dot Beads

Due to their potential adverse effects on human health, the use of carbadox and olaquindox in feedingstuffs was prohibited by the European Union since 1998. In this work, highly luminescent quantum dot beads (QBs) were synthesized by encapsulating CdSe/ZnS and used as novel fluorescent probes in the immunochromatographic assay (ICA) for simultaneous and quantitative determination of metabolites of olaquindox (3-methylquinoxaline-2-carboxylic acid, MQCA) and carbadox (quinoxaline-2-carboxylic, QCA). The fluorescence intensities of the test lines were recorded using a fluorescence strip reader. The 50% of inhibition for MQCA and QCA was shown to be 8.1 and 10.6 μg L^?1, respectively. The whole assay process can be accomplished within 10 min. The immunosensor was used to analyze spiked samples, and analyte intra- and inter-assay recovery rates ranged from 78.7 to 92.2% for MQCA and 80.6 to 95.8% for QCA, and coefficients of variation were all below 12%. The incurred tissues samples were assayed using both QB-based ICA and commercial ELISA kit and were further confirmed with LC-MS/MS. The QB-based ICA results exhibited good agreement with both commercial ELISA and LC-MS/MS methods.     

UPLC-MS/MS法测定金沙江水域鱼体中卡巴氧及喹乙醇代谢物

为建立一种白酒香型鉴别方法,以DB-WAX为色谱柱,样品加标后直接采用气相色谱（GC）法进样分析。结果表明,香气成分线性相关系数R2＞0.999,检测限＜5.11 mg/L,精密度试验结果的相对标准偏差（RSD）＜4.11%;平均回收率为80.20%～97.93%。采用偏最小二乘法（PLS）对不同香型白酒数据进行建模和预测,不同香型白酒样品在PLS得分图中能分开,利用训练集和验证集数据对模型进行验证,结果表明预测准确率较高,校正均方差（RMSEE）和预测均方差（RMSEP）值也说明PLS模型对不同白酒香型具有较强的预测性。该方法在判别白酒香型分析中具有较高的准确性。     

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.     

Quinoxaline-2-carboxylic acid in pigs: criteria to distinguish between the illegal use of carbadox and environmental contamination

Carbadox cannot be used in food-producing animals within the European Union following the adoption of Commission Regulation EC 2788/98/EC. Monitoring of the longest remaining residue—quinoxaline-2-carboxylic acid (QCA)—is the most effective way of enforcing the prohibition on its use. The study was under taken to determine if QCA could be passed from pig to pig following the exposure of unmedicated animals to housing that had previously contained medicated animals. Drug-withdrawal studies were also carried out on medicated animals. Distinction between treated animals and those exposed to QCA might be required by competent national authorities to determine whether a positive result for QCA in tissue is truly 'violative'. Comparison of the ratio concentrations of QCA in tissues and body fluids was made to determine if they could be used as criteria for discrimination between illegally treated animals and environmental contamination.     

Simultaneous determination of five quinoxaline-1,4-dioxides in animal feeds using an immunochromatographic strip

An immunochromatographic (ICG) strip was developed for the simultaneous quantitative determination of five quinoxaline-1,4-dioxides in animal feed. For this purpose, polyclonal antibodies (PcAb) with group-specific quinoxaline-1,4-dioxides were conjugated to colloidal gold particles as the detection reagent for ICG strips to test for quinoxaline-1,4-dioxides. This method achieved semi-quantitative detection of quinoxaline-1,4-dioxides within 5–10 min. The visual lower detection limits of the strip for quinocetone, cyadox, carbadox, mequindox and olaquindox were 10, 15, 15, 20 and 20 ng ml^?1, respectively. Using an ICG strip reader, the 50% inhibitions (IC₅₀ values) were calculated to be 9.1, 13.5, 16.6, 20.2 and 21.3 ng ml^?1 for quinocetone, cyadox, carbadox, mequindox and olaquindox, respectively. When used to analyse samples of animal feed, acceptable recovery rates of 77.5–99.5% and coefficients of variation (CVs) of 4.3–10.7% were obtained. Levels measured with the ICG strip for 10 spiked samples were confirmed by HPLC with a high correlation coefficient of 0.9965 (n = 10). In conclusion, the method was rapid and accurate for simultaneous determination of five quinoxaline-1,4-dioxides antibiotics in animal feed.     

Mass spectrometric analysis of muscle samples to detect potential antibiotic growth promoter misuse in broiler chickens

Mass spectrometric methods were developed and validated for the analysis in chicken muscle of a range of antibiotic growth promoters: spiramycin, tylosin, virginiamycin and bacitracin, and separately for two marker metabolites of carbadox (quinoxaline-2-carboxylic acid and 1,4-bisdesoxycarbadox), and a marker metabolite of olaquindox (3-methyl-quinoxaline-2-carboxylic acid). The use of these compounds as antibiotic growth promoters has been banned by the European Commission. This study aimed to develop methods to detect their residues in muscle samples as a means of checking for the use of these drugs during the rearing of broiler chickens. When fed growth-promoting doses for 6 days, spiramycin (31.4?μg?kg(-1)), tylosin (1.0?μg?kg(-1)), QCA (6.5?μg?kg(-1)), DCBX (71.2?μg?kg(-1)) and MQCA (0.2?μg?kg(-1)) could be detected in the muscle 0 days after the withdrawal of fortified feed. Only spiramycin could consistently be detected beyond a withdrawal period of 1?day. All analytes showed stability to a commercial cooking process, therefore raw or cooked muscle could be used for monitoring purposes.     

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.     

胶体金试纸条同时检测鲤鱼中7种苯并咪唑类药物的残留

为检测鲤鱼中苯并咪唑类药物残留,降低其对人体造成的危害,本文基于单克隆抗体之上建立胶体金试纸条检测方法。首先以2-甲氧基羰基氨基-3H-苯并咪唑-5-羧酸为半抗原,用活化酯法偶联蛋白质制备免疫原,免疫小鼠,进行细胞融合制备单克隆抗体,而后用合成的胶体金标记单克隆抗体制备胶体金试纸条。通过间接竞争ELSIA法(ic-ELISA)测得阿苯达唑、甲苯咪唑、阿苯达唑亚砜、阿苯达唑砜、芬苯达唑、氟苯咪唑、奥芬达唑的半抑制浓度(IC50)分别为0.44、0.16、3.47、5.62、0.62、0.10、5.77 ng/mL。胶体金试纸条在鲤鱼中的阿苯达唑、甲苯咪唑、阿苯达唑亚砜、阿苯达唑砜、芬苯达唑、氟苯咪唑、奥芬达唑的检测限分别为4、2、50、100、10、1、100 ng/g,检测时间为15 min。因此,该方法灵敏度高、成本低、速度快且无需仪器辅助,适宜现场大量鲤鱼样本的快速检测。     

Mass spectrometric analysis of muscle samples to detect potential antibiotic growth promoter misuse in broiler chickens

Mass spectrometric methods were developed and validated for the analysis in chicken muscle of a range of antibiotic growth promoters: spiramycin, tylosin, virginiamycin and bacitracin, and separately for two marker metabolites of carbadox (quinoxaline-2-carboxylic acid and 1,4-bisdesoxycarbadox), and a marker metabolite of olaquindox (3-methyl-quinoxaline-2-carboxylic acid). The use of these compounds as antibiotic growth promoters has been banned by the European Commission. This study aimed to develop methods to detect their residues in muscle samples as a means of checking for the use of these drugs during the rearing of broiler chickens. When fed growth-promoting doses for 6 days, spiramycin (31.4?µg?kg^?1), tylosin (1.0?µg?kg^?1), QCA (6.5?µg?kg^?1), DCBX (71.2?µg?kg^?1) and MQCA (0.2?µg?kg^?1) could be detected in the muscle 0 days after the withdrawal of fortified feed. Only spiramycin could consistently be detected beyond a withdrawal period of 1?day. All analytes showed stability to a commercial cooking process, therefore raw or cooked muscle could be used for monitoring purposes.     

Simultaneous Determination of Cyadox and Its Metabolites in Chicken Tissues by LC-MS/MS

A specific and sensitive LC-MS/MS method was firstly established for the simultaneous extraction and determination of cyadox and its three main metabolites—1,4-bisdesoxycyadox, 4-desoxycyadox, and quinoxaline-2-carboxylic acid—in chicken muscle, liver, kidney, and fat tissues. Samples were subjected to extraction using ethyl acetate and followed by acetonitrile–chloroform (1:4, v/v) and further purified by Oasis mixed mode anion exchange SPE cartridge. Analysis was performed on a C₁₈ column by detection with MS in multiple-reaction monitoring mode. A gradient elution program with 0.1 % formic acid solution, acetonitrile, and 1 % formic acid (adjusted to pH 8 with ammonia) was performed at a flow rate of 0.2 mL min^?1. The correlation coefficients (r) for each calibration curve are higher than 0.99 within the experimental concentration range. The recoveries of the four target analytes at three spiking levels of 2.5, 25 and 250 μg kg^?1 were between 74.5 and 93.8 %, with relative standard deviations less than 12 %. The decision limits (CCαs) of the four analytes in chicken edible tissues ranged from 0.3 to 1.5 μg kg^?1, and the detection capabilities (CCβs) were below 2.3 μg kg^?1. The developed method demonstrated a satisfactory applicability in incurred chicken tissue samples.     

基于量子点建立铅镉快速串联检测方法

将鼠抗Cd2＋-IEDTA单克隆抗体和鼠抗Pb2＋-IEDTA单克隆抗体分别与包载CdSe/CdS量子点聚苯乙烯微球偶联,建立一种可快速检测铅镉的量子点荧光定量串联卡及免疫层析竞争检测方法。串联卡的最佳反应时间为5?min,可检测的Pb2＋和Cd2＋质量浓度范围分别为1～500?ng/mL和1～400?ng/mL,检测变异系数小于10%;检测特异性良好,与其他金属离子无明显交叉反应;利用该方法与电感耦合等离子体-质谱（inductively coupled plasma-mass spectrometry,ICP-MS）法进行肉类食品检测对比,检测结果与ICP-MS相关性良好。该检测方法为同时定量检测铅镉提供快速简便的有效途径,适用于监测肉中Pb2＋和Cd2＋含量是否超标。     

Cloud-point extraction and reversed-phase high-performance liquid chromatography for the determination of synthetic phenolic antioxidants in edible oils

A cloud-point extraction (CPE) method using Triton X-114 (TX-114) nonionic surfactant was developed for the extraction and preconcentration of propyl gallate (PG), tertiary butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) from edible oils. The optimum conditions of CPE were 2.5% (v/v) TX-114, 0.5% (w/v) NaCl and 40 min equilibration time at 50 °C. The surfactant-rich phase was then analyzed by reversed-phase high-performance liquid chromatography with ultraviolet detection at 280 nm, using a gradient mobile phase consisting of methanol and 1.5% (v/v) acetic acid. Under the studied conditions, 4 synthetic phenolic antioxidants (SPAs) were successfully separated within 24 min. The limits of detection (LOD) were 1.9 ng mL(-1) for PG, 11 ng mL(-1) for TBHQ, 2.3 ng mL(-1) for BHA, and 5.9 ng mL(-1) for BHT. Recoveries of the SPAs spiked into edible oil were in the range 81% to 88%. The CPE method was shown to be potentially useful for the preconcentration of the target analytes, with a preconcentration factor of 14. Moreover, the method is simple, has high sensitivity, consumes much less solvent than traditional methods, and is environment-friendly. Practical Application: The method established in this article uses less organic solvent to extract SPAs from edible oils; it is simple, highly sensitive and results in no pollution to the environment.     

SPE-HPLC-MS/MS法检测动物源性运动食品中喹乙醇及卡巴氧代谢物残留

建立一种快速、高效的固相萃取-高效液相色谱-串联质谱法（SPE-HPLC-MS/MS）测定动物源性运动食品中的3-甲基-喹喔啉-2-羧酸（MQCA）及喹恶啉-2-羧酸（QCA）的方法。样品前处理采用碱水解提取MQCA和QCA,经PAX固相萃取柱（60 mg/3 mL）净化后检测。以乙腈-0.1%甲酸溶液为流动相,在质谱检测器的多反应监测（MRM）模式下进行分析。结果表明,MQCA和QCA在0.1～50.0 ng/mL质量浓度范围内线性关系良好,相关系数R2为0.999 6～0.999 8,检出限均为0.05 μg/kg,定量限均为0.20 μg/kg。平均加标回收率为83.67%～96.08%,精密度试验结果相对标准偏差（RSD）为1.75%～3.10%。该方法具有前处理简单、净化效果好、灵敏度高和检测速度快的优点,适用于动物源性运动食品中的MQCA及QCA残留量的检测。     

胶体金免疫层析试纸条快速检测水和玉米中阿特拉津的残留

本文以胶体金作为抗体标记物,建立了一种检测阿特拉津残留的免疫层析试纸条快速检测方法.该方法的检出限为2ng/mL,10min内可以得到检测结果.本文以自来水和玉米作为样品进行了添加回收实验,水样不需要任何前处理直接检测,水样的检出限为2 ng/mL;玉米样品经简单前处理后检测,玉米样品的检出限为40 ng/g,且该方法的检测结果与间接竞争ELISA方法的结果一致.该方法具有成本低、操作简单、灵敏度高、检测快速,结果易于判定等优点,适用于大量样品的现场筛选.     

高灵敏度磁荧光免疫层析试纸模式构建及在呕吐毒素检测中的应用

构建基于磁荧光纳米材料的免疫层析试纸模式,弥补现在免疫层析技术的不足,为更灵敏的免疫学快速检测提供技术支撑。以呕吐毒素（deoxynivalenol,DON）为靶标,采用溶剂热法制备羧基修饰的超顺磁颗粒,碳二亚胺法将磁颗粒、绿色荧光蛋白及DON单克隆抗体进行偶联,一步法制备磁荧光抗体探针,以DON人工抗原（DON-BSA）为检测线建立磁荧光免疫层析试纸。同时用胶体金标记DON单克隆抗体,以DON-BSA为检测线建立胶体金免疫层析试纸;制备的磁荧光抗体探针具有很好的磁性、荧光特性及抗体反应性,基于该探针成功制备了DON磁荧光免疫层析试纸,该试纸回归方程为y=－0.562x＋0.921,R2=0.990,IC50为5.611 ng/mL,检出限为1.089 ng/mL;制备了DON胶体金免疫层析试纸,该试纸裸眼检测灵敏度为500 ng/mL;定量检测回归方程为y=－0.543x＋1.485,R2=0.991,IC50为65.16 ng/mL,检出限为11.94 ng/mL。DON磁荧光免疫层析试纸的灵敏度是胶体金免疫层析试纸的10.96 倍。本实验建立的磁荧光免疫层析试纸模式可以同时实现样品的富集及荧光信号检测,提高检测灵敏度,并成功用于DON的检测,为磁荧光纳米颗粒广泛应用于免疫层析领域提供参考。     

The decrease of lasalocid residue in the edible tissues by silymarin supplementation of chicken diet

Widespread use of coccidiostats, in spite of beneficial control of protozoan infections in poultry, implies a risk of residues in edible tissues, and there is increasing interest in the development of strategies for prevention of veterinary drugs residue in food-producing animals. The aim of this study is assigned to clarify the impact of silymarin addendum in the diet on lasalocid concentration in the liver and breast muscles from the broiler. Four groups of chickens received a feed with lasalocid at levels between 75 and 200 mg kg^?1. Other four groups received a feed with lasalocid (75–200 mg kg^?1) plus silymarin. Significant differences of lasalocid concentrations between the liver and breast muscles were observed. Moreover, the chickens from the groups supplemented with silymarin shown significant decreases of lasalocid concentrations in the analysed tissues. The herbal substance did not counteract the ionophore in the treatment of coccidiosis and did not change biochemical parameters of blood. These findings suggest that silymarin might be used in chicken feeding in order to reduce the risk from lasalocid contamination of the broiler edible tissues.