液相色谱-串联质谱测定鸡肉中喹乙醇残留标示物3-甲基喹恶啉-2-羧酸

建立了简便、灵敏、科学和可靠的液相色谱-串联质谱测定鸡肉中喹乙醇残留标示物3-甲基喹恶啉-2-羧酸（MQCA）的分析方法。采用给鸡灌服喹乙醇的方式，获得含MQCA的鸡肉试样，比较了酶解、酸解和碱解等方法水解鸡肉中MQCA的效率，实验表明，碱水解鸡肉组织得到最高含量的MQCA。样品经1.0 mol/L氢氧化钠溶液水解，正己烷除脂，MAX混合型阴离子交换固相萃取柱直接净化，采用C₁₈反相色谱柱分离，质谱选择反应监测模式检测。结果表明：MQCA在1.0~100 μg/L范围内线性关系良好，相关系数（r²）大于0.99；方法检出限为0.4 μg/kg。在1.0、5.0和50.0 μg/kg 3个添加水平下，采用外标法定量，MQCA的平均回收率为71.7%~82.4%，采用内标法定量，其回收率为96.3%~103.7%，相对标准偏差均小于6.0%。该方法适用于动物性食品中3-甲基喹恶啉-2-羧酸残留的日常监测。

Determination of 3-methylquinoxaline-2-carboxylic acid of olaquindox marker residue in chicken muscles by liquid chromatography-tandem mass spectrometry

A simple, sensitive, scientific and reproducible liquid chromatography-tandem mass spectrometric method was developed to determine 3-methylquinoxaline-2-carboxylic acid (MQCA) of olaquindox marker residue in chicken muscle tissues. The chickens were administered orally with olaquindox and used as positive samples. The approaches, enzyme, acid, and base hydrolysis, were adopted to digest MQCA in the medicated chicken muscles. The amounts of MQCA in the medicated chicken were determined and compared using different hydrolysis approaches. It was shown that the highest amount of MQCA was obtained for the base hydrolysis approach. Here, the sample was hydrolyzed with 1.0 mol/L NaOH solution, defatted with n-hexane, and purified with a mixed anion-exchange solid-phase extraction cartridge. The chromatographic separation was performed on a reversed-phase C₁₈ column and detected using mass spectrometry in selected reaction monitoring mode. The analyte showed good linearity in the range 1.0-100 μg/L. The correlation coefficient (r²) was greater than 0.99. The limit of detection of the proposed method was 0.4 μg/kg. At the three spiked levels of 1.0, 5.0 and 50.0 μg/kg, the average recoveries of MQCA were in range 71.7%-82.4% obtained using external standard calibration, and in range 96.3%-103.7% for internal standard calibration, with relative standard deviations below 6.0%. The proposed method is suitable for routinely monitoring of MQCA residues in animal-derived foods.