Introduction: In the present study, a sensitive and selective liquid chromatographytandem mass spectrometry (LC-MS/MS) method was described for the determination of ceftiofur (CEF) in cow milk and pharmaceutical preparations. CEF is an antibiotic compound, which is commonly used in the treatment of animal diseases such as respiratory system, soft tissue, and foot infections, as well as postpartum acute puerperal metritis. One of the critical features of CEF is its prescription while breastfeeding cows; in accordance, its quantitative estimation is essential to assess its residual amounts.

Methods: In the method reported herein, after simple protein precipitation using acetonitrile, the pre-treated samples were introduced into an LC-MS/MS instrument equipped with a Chromolith® High-Resolution RP-18 series HPLC column (100 mm × 4.6 mm from Merck KGaA, Germany). Electrospray ionization was employed as the ionization source in the triple-quadrupole tandem mass spectrometer.

Results: For the calibration method using solvent-based standards, LOQ was 3.038 ng/mL, 12.15 ng/mL, and LOD was 1.215 ng/mL and 6.076 ng/mL for ESI+ and ESI- modes, respectively. On the other hand, for the method of matrix-matched standards, LOQ was 1.701 ng/mL, 10.13 ng/mL, and LOD was 0.486 ng/mL and 5.929 ng/mL for ESI+ and ESI- modes, respectively as obtained from signal to noise ratio.

Conclusion: Applicability of both positive and negative ion modes was tested, and the analyte was detected via multiple reaction monitoring. The distorting effects of the milk matrix on the MS ionization and quantitation of CEF were overcome by using matrix-matched calibration for the first time.

简介：在本研究中，描述了一种灵敏且选择性的液相色谱串联质谱 (LC-MS/MS) 方法，用于测定牛奶和药物制剂中的头孢噻呋 (CEF)。CEF是一种抗生素化合物，常用于治疗呼吸系统、软组织、足部感染等动物疾病，以及产后急性产褥期子宫炎。CEF 的关键特征之一是它在母乳喂养奶牛时的处方；因此，其定量估计对于评估其剩余金额至关重要。

方法：在本文报道的方法中，在使用乙腈进行简单的蛋白质沉淀后，将预处理的样品引入配备 Chromolith® 高分辨率 RP-18 系列 HPLC 柱（100 mm × 4.6 mm）的 LC-MS/MS 仪器中。来自德国默克公司）。在三重四极杆串联质谱仪中采用电喷雾电离作为电离源。

结果：对于使用基于溶剂的标准品的校准方法，ESI+ 和 ESI- 模式的 LOQ 为 3.038 ng/mL、12.15 ng/mL，LOD 分别为 1.215 ng/mL 和 6.076 ng/mL。另一方面，对于基质匹配标准品的方法，从信号获得的 ESI+ 和 ESI- 模式的 LOQ 分别为 1.701 ng/mL、10.13 ng/mL，LOD 分别为 0.486 ng/mL 和 5.929 ng/mL噪声比。

结论：测试了正负离子模式的适用性，并通过多反应监测检测了分析物。首次使用基质匹配校准克服了牛奶基质对 CEF 的 MS 电离和定量的失真影响。