The application of dispersive liquid-liquid microextraction in the analyses of the fatty acid profile in bovine milk in response to changes in body condition score.

Dispersive liquid-liquid microextraction (DLLME) was used prior to gas chromatography flame ionization detection (GC-FID) for the extraction of five fatty acids from milk taken from cows with different body condition scores. Optimum extraction conditions were: 300 μL of chloroform (extraction solvent), and 1 mL methanol (dispersive solvent). The procedure was optimised using Design of Experiments (DoE). The analytes were separated on a GC capillary column containing a polyethylene glycol stationary phase (15 m × 0.53 mm × 1.2 μm). Enrichment factors were in the range of 8-15 and limit of detection (LOD) was 0.04 μg/mL. Calibration graphs showed good linearity with coefficients of determination higher than 0.994% and relative standard deviations lower than 7%. This method provided a simple and rapid derivatisation and extraction method for the determination of fatty acids in bovine milk. It showed that there was a significant difference in the palmitic acid content of milk from cows that had an optimum body condition score (10.85 mg/mL) compared to cows that had a high body condition score (5.73 mg/mL).