methyl-3-quinoxaline-2-carboxylic-acid and quinoxaline-2-carboxylic-acid

A new molecularly imprinted polymer (MIP), selective for major metabolites of quinoxaline-1,4-dioxides, was prepared through bulk polymerisation using quinoxaline-2-carboxylic acid (QCA) as template, diethylaminoethylmethacrylate as functional monomer and ethylene glycol dimethacrylate as cross-linker in tetrahydrofuran. The synthesised MIP was characterised by Fourier transform infrared and adsorption experiments. MIP exhibited high affinity, fast kinetics for QCA and good selectivity for QCA and methyl-3-quinoxaline-2-carboxylic acid (MQCA). MIP obtained was used as a selective sorbent for molecularly imprinted solid phase extraction (MISPE) coupled with HPLC to detect QCA and MQCA. Under the optimal conditions, the limits of detection (S/N=3) of porcine, chicken and fish muscles were 0.1, 0.3, 0.1 μg/kg for QCA and 0.2, 0.3, 0.1 μg/kg for MQCA, respectively and good recoveries were obtained in the range from 60.0 to 119.4%. These results indicated the MISPE-HPLC procedure could be successfully used for the determination QCA and MQCA in animal muscles.

Topics: Animals; Chickens; Chromatography, High Pressure Liquid; Fishes; Food Contamination; Growth Substances; Meat; Molecular Imprinting; Molecular Structure; Muscle, Skeletal; Quinoxalines; Solid Phase Extraction; Swine

A new molecularly imprinted polymer (MIP), selective for major metabolites of quinoxaline-1,4-dioxides was firstly prepared by combining surface molecular imprinting technique with the sol-gel process. Methyl-3-quinoxaline-2-carboxylic acid (MQCA) was used as template, 3-aminopropyltriethoxysilane as functional monomer, and tetraethoxysilicane as cross-linker. The MIP was characterized by Fourier transform infrared and evaluated through static adsorption experiments. The results indicated that MIP had high adsorption capacity, fast binding kinetics for MQCA, and the polymer showed a high degree of cross-reactivity for quinoxaline-2-carboxylic acid (QCA). The MIP was then applied as a selective sorbent in an online solid phase extraction (SPE) coupled with high-performance liquid chromatography (HPLC). For a 50-mL sample solution, enrichment factors of 1,349 and 1,046 for QCA and MQCA, respectively, and limits of detection (S/N=3) of 0.8 and 2 ng L(-1) for QCA and MQCA, respectively, were obtained (corresponding to 0.02 and 0.04 ng g(-1) in solid samples for final 100 mL of sample solutions of 5 g of pork). The sample preparation protocol was simplified and only included one step extraction with acetonitrile (MeCN) after the release of target analytes through acidic hydrolysis without further sample cleanup. The new MIP-SPE-HPLC method was successfully applied to the quantification of trace QCA and MQCA in pork muscle with good recoveries ranging from 67% to 80% and RSD below 8%.

Topics: Adsorption; Animals; Chromatography, High Pressure Liquid; Meat; Molecular Imprinting; Muscles; Polymers; Quinoxalines; Silica Gel; Solid Phase Extraction; Swine

A method of high-performance liquid chromatography with UV detection has been established for simultaneous quantitative determination of quinoxaline-2-carboxylic acid (QCA) and methyl-3-quinoxaline-2-carboxylic acid (MQCA), the marker residues for carbadox (CBX) and olaquindox (OLA), respectively, in the muscles and livers of porcine and chicken and in the muscle of fish. Tissue samples were subject to acid hydrolysis followed by liquid-liquid extraction and Oasis MAX solid-phase extraction clean-up. The method was validated according to the EU Commission Decision 2002/657/EC. The decision limits (CCalpha) were 0.7-2.6microg/kg and the detection capabilities (CCbeta) were 1.3-5.6microg/kg for QCA and MQCA in tissues. The recoveries of QCA and MQCA, spiked at levels of 2-100microg/kg, were from 70 to 110%; the relative standard deviation values were <20%. This simple, fast and economic method could be applied to the monitoring for the possible misuse of CBX and OLA in animal edible tissue samples.

Topics: Animals; Chickens; Chromatography, High Pressure Liquid; Fishes; Liver; Muscles; Quinoxalines; Reproducibility of Results; Swine

A method is described for the quantitative determination of quinoxaline-2-carboxylic acid (QCA) and methyl-3-quinoxaline-2-carboxylic acid (MQCA), the metabolites that have been designated as the marker residues for the veterinary drugs, carbadox and olaquindox, respectively, in swine tissue. The method is suitable for use as a confirmatory method under EU National Surveillance Schemes. Porcine liver samples were subjected to protease digestion followed by liquid-liquid extraction. Further clean-up was performed by automated solid phase extraction (SPE) and was followed by a final liquid-liquid extraction step. Analysis was performed using a narrow bore column HPLC coupled to electrospray MS/MS, operated in positive ion mode. MS/MS product ions were monitored at m/z 102 and 75 amu for QCA, m/z 145 and 102 amu for MQCA and at m/z 106 and 152 amu for the d(4)-QCA and d(7)-MQCA internal standards, respectively. The method has been validated at 3.0, 10, 50 and 150 microg kg(-1) for both metabolites. The method performance characteristics-the decision limit (CCalpha) and the detection capability (CCbeta) have been determined for QCA at 0.4 and 1.2 microg kg(-1), respectively, and for MQCA at 0.7 and 3.6 microg kg(-1), respectively.

Topics: Animals; Biomarkers; Carbadox; Chromatography, Liquid; Drug Residues; Liver; Quinoxalines; Spectrometry, Mass, Electrospray Ionization; Swine