牛奶是一种重要的消费品,具有很高的营养价值。由于滥用兽药而导致牛奶中兽药残留的存在可能会影响消费者的健康。在痕量化合物的质谱分析中,色谱共洗脱组分容易干扰获得的质谱信号,影响定性和定量分析的准确性。基质纯化是减少基质效应的一种有前途的方法。壳聚糖是一种天然生物聚合物,具有许多活性官能团,如氨基,乙酰基,和羟基;这些基团可以通过疏水和静电相互作用吸附脂质。壳聚糖还具有生产成本低的优点,化学性质稳定,和方便的修改。新型基于壳聚糖的材料是用于脂质纯化的有希望的候选物。在这项研究中,用三甲氧基十八烷基硅烷(C18-CSM)改性壳聚糖膜。C18-CSM通过一步水解制备,并用作分散固相萃取(DSPE)吸附剂,以在牛奶预处理过程中纯化基质。我们将C18-CSM与超高效液相色谱-四极杆/静电场轨道阱质谱(UHPLC-Q/ExactiveOrbitrapMS)相结合,建立了一种有效的氧氟沙星提取和测定方法,恩诺沙星,环丙沙星,地西泮,还有牛奶中的甲硝唑.C18-CSM使用扫描电子显微镜进行表征,傅里叶变换红外光谱,和水接触角测试。结果表明,该材料具有粗糙的表面和均匀致密的横截面。C18-CSM的水接触角为104°,表明其良好的疏水性。预处理条件(萃取溶剂,NaCl用量,提取频率,详细研究了影响五种兽药回收率的C18-CSM)剂量。建立了最佳工艺条件:5%甲酸,乙腈,1克NaCl,提取1次,20毫克C18-CSM。在HypersilGOLDVANQUISH色谱柱上进行分离(100mm×2.1mm,1.9μm)。流动相为0.1%甲酸水溶液和0.1%甲酸的乙腈溶液,并且以0.3mL/min的速率流动。进样体积为1μL,柱温保持在25℃。以正电喷雾电离模式进行质谱分析。为了验证净化材料的必要性,采用基质匹配标准曲线法研究基质效应.C18-CSM的使用将五种必需药物的基质效应从-22%-8.8%的范围降低到-13%-3.6%的范围,表明C18-CSM是一种高效的DSPE材料。在最优条件下,所开发的方法在0.5-100μg/L范围内显示出良好的线性,相关系数(r2)≥0.9970。检测限(LODs)和定量限(LOQs)分别为0.2μg/L和0.5μg/L,分别。为了评估该方法的准确性和精密度,我们准备了三个加标水平的牛奶样品(低,中等,和高)。五种兽药的回收率从79.5%到115%不等,日内和日间相对标准偏差分别为7.0%-13%(n=6)和1.3%-11%(n=3),分别。这项研究提供了一个简单的,准确,方法可靠,快速,同时测定牛奶中五种兽药的残留量。
Milk is an important consumer product with high nutritional value. The presence of veterinary drug residues in milk owing to the indiscriminate use of veterinary drugs may affect consumer health. In the mass spectrometric analysis of trace compounds, chromatographic co-eluting components easily interfere with the mass spectral signals obtained, affecting the accuracy of qualitative and quantitative analyses. Matrix purification is a promising method to reduce the matrix effect. Chitosan is a natural biopolymer with numerous active functional groups such as amino, acetyl, and hydroxyl groups; these groups can adsorb lipids through hydrophobic and electrostatic interactions. Chitosan also has the advantages of low production cost, stable chemical properties, and convenient modification. Novel chitosan-based materials are promising candidates for lipid purification. In this study, a chitosan membrane was modified with trimethoxyoctadecylsilane (C18-CSM). C18-CSM was prepared through one-step hydrolysis and used as a dispersive solid phase extraction (DSPE) adsorbent to purify the matrix during milk pretreatment. We combined C18-CSM with ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry (UHPLC-Q/Exactive Orbitrap MS) to develop an effective method for the extraction and determination of ofloxacin, enrofloxacin, ciprofloxacin, diazepam, and metronidazole in milk. C18-CSM was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle testing. The results indicated that the material has a rough surface and uniformly dense cross-section. The water contact angle of C18-CSM was 104°, indicating its good hydrophobicity. The pretreatment conditions (extraction solvent, dosage of NaCl, extraction frequency, and dosage of C18-CSM) that influenced the recoveries of the five veterinary drugs were investigated in detail. The optimal conditions were established as follows: 5% formic acid in acetonitrile, 1 g NaCl, extraction 1 time, 20 mg C18-CSM. Separation was performed on a Hypersil GOLD VANQUISH column (100 mm×2.1 mm, 1.9 μm). The mobile phase consisted of 0.1% formic acid aqueous solution and 0.1% formic acid in acetonitrile, and was flowed at a rate of 0.3 mL/min. The sample injection volume was 1 μL, and the column temperature was maintained at 25 ℃. Mass spectrometric analysis was performed in positive electrospray ionization mode. To verify the necessity of the purification material, the matrix effect was investigated using the matrix-matched standard curve method. The use of C18-CSM reduced the matrix effects of the five necessity drugs from the range of -22%-8.8% to the range of -13%-3.6%, indicating that C18-CSM is a highly efficient DSPE material. Under optimal conditions, the developed method showed good linearities within the range of 0.5-100 μg/L, with correlation coefficients (r2)≥0.9970. The limits of detection(LODs) and quantification (LOQs) were 0.2 μg/L and 0.5 μg/L, respectively. To assess the accuracy and precision of the method, we prepared milk samples with three spiked levels (low, medium, and high). The recoveries of the five veterinary drugs were ranged from 79.5% to 115%, and the intra-day and inter-day relative standard deviations were 7.0%-13% (n=6) and 1.3%-11% (n=3), respectively. This study provides a simple, accurate, and reliable method for the rapid and simultaneous determination of the five veterinary drug residues in milk.