Determination of Diclofenac in Bovine Milk at Low Levels Using Ultra High Performance Liquid Chromatography–Tandem Mass Spectrometry

Abstract

This paper reports on the development and validation of a simple, rapid, and sensitive ultra high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method to quantify low levels of diclofenac in bovine milk samples. The sample preparation procedure involves the milk deproteination by ethyl acetate in the presence of sodium acetate and silica at pH = 4.0 adjusted with acetic acid. The extract was evaporated, reconstituted, and injected into a chromatographic system prior to the analysis, which used a C18 column and mobile phase gradient elution. Data were acquired under MS tandem using positive electrospray (ESI) mode and multiple reaction monitoring (MRM). The calibration curve was linear across the concentration range of 0.05–5.00 ng mL−1 with LOD and LOQ of 0.015 and 0.048 ng mL−1, respectively. The proposed method provides acceptable values for repeatability (RSD < 18.8%), intermediary precision (RSD < 15.3%), and accuracy (−2.3–14.9%).