基于信息熵理论，以5-吗啉甲基-3-氨基-2-口恶唑烷基酮（AMOZ）、3-氨基-2-口恶唑烷基酮（AOZ）、1-氨基-2-乙内酰（AHD）和氨基脲（SEM）等4种硝基呋喃类代谢物回收率综合评分M为评价指标，采用单因素和响应面试验优化了淡水鱼中硝基呋喃类代谢物残留检测的衍生条件。淡水鱼样品用盐酸溶液水解后加入适量内标溶液，用350 μL 0.05 mol·L^-1邻硝基苯甲醛（衍生试剂）溶液（介质为甲醇）于46℃避光振荡衍生2.5 h。将所得溶液酸度调节至pH 7.4±0.2，用乙酸乙酯提取2次。收集提取液，氮吹至干，加入正己烷用于除杂，50%（体积分数）乙腈溶液用于复溶残渣，离心，取下层相过滤，滤液用超高效液相色谱-串联质谱法分析。在色谱分析中，以Agilent Zorbax RRHD Eclipse Plus C₁₈色谱柱（100 mm×2.1 mm，1.8 μm）分离，体积比1∶1的0.1%（体积分数）甲酸溶液和乙腈的混合溶液等度洗脱。在质谱分析中，以大气压电喷雾离子源电离，多反应监测（MRM）模式检测。在定量分析时，以基质匹配法以及内标法降低基质干扰和提高方法的灵敏度。结果显示：因素衍生试剂体积、衍生温度和衍生时间以及交互因素衍生试剂体积与衍生温度对回收率综合评分M的影响极显著（p<0.01），最优衍生条件下二次多项式模型的预测值（M_预测=1.020 4）和试验值（M_试验=0.999 2）基本一致；4种硝基呋喃类代谢物工作曲线的线性范围均为0.02~50.00 μg·L^-1，检出限（3S/N）为0.02~0.19 μg·kg^-1。按照标准加入法进行回收试验，回收率为85.1%~116%，测定值的相对标准偏差（n=5）为0.64%~9.8%。方法用于55批实际样品的分析，AOZ、AMOZ和SEM检出率分别为1.82%，1.82%和3.64%，其中AOZ和AMOZ的最高检出量分别为0.24，0.13 μg·kg^-1，SEM的检出量在测定下限以下。

Based on the information entropy theory, the recovery comprehensive score M of the 4 nitrofuran metabolites, including 5-morpholinomethyl-3-amino-2-oxazolidinone (AMOZ), 3-amino-2-oxazolidinone (AOZ), 1-aminohydantoin hydrochloride (AHD) and semicarbazide hydrochloride (SEM), was used as the evaluation index to optimize the derivatization conditions for the detection of nitrofuran metabolites residues in freshwater fish by single factor and response surface tests. The freshwater fish sample was hydrolyzed by hydrochloric acid solution, and internal standards solution was added. Then, 350 μL of 0.05 mol·L^-1 ortho nitrobenzaldehyde (derivatization reagent) solution with methanol as the medium was added, and derivatization reaction was made by oscillation at 46℃ under the light proof condition for 2.5 h. The acidity of the solution obtained was adjust to pH 7.4 ± 0.2, and extraction was made twice by ethyl acetate. The extract was collected, and blown to dryness by nitrogen. n-Hexane was added for impurity removal, and 50% (volume fraction) acetonitrile solution was added for redissolving the residue. After centrifugation, the lower phase was taken for filtration, and the filtrate was analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry. In chromatographic analysis, Agilent Zorbax RRHD Eclipse Plus C₁₈ chromatographic column (100 mm×2.1 mm, 1.8 μm) was used for separation, and the mixed solution composed of 0.1% (volume fraction) formic acid solution and acetonitrile at volume ratio of 1:1 was used for isocratic elution. In mass spectrometry analysis, atmospheric pressure spray ion source was used for ionization, and multiple reaction monitoring (MRM) mode was used for detection. In quantitative analysis, matrix matching and internal standard methods were used to reduce matrix interference and improve the sensitivity of the method. It was shown that factors of derivatization reagent volume, derivatization temperature, and derivatization time, as well as the interaction factor of derivatization reagent volume and derivatization temperature, had a significant effect on the recovery comprehensive score M (P<0.01). Under the optimal derivatization conditions, the test value of the quadratic polynomial model (M_test=1.020 4) and the prediction value (M_prediction=0.999 2) were basically consistent. The linear ranges of the working curves for the 4 nitrofuran metabolites were found in the same range of 0.02-50.00 μg·L^-1, with detection limits (3S/N) in the range of 0.02-0.19 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 85.1%-116%, and RSDs (n=5) of the determined values ranged from 0.64% to 9.8%. The proposed method was used for the analysis of 55 batches of actual samples, and the detection rates of AOZ, AMOZ, and SEM were 1.82%, 1.82%, and 3.64%, respectively. The highest detection amounts of AOZ and AMOZ were 0.24, 0.13 μg·kg^-1, and the detection amount of SEM was below the lower limit of determination.