Bovine milk is an important source of energy, protein, essential vitamins, and minerals for humans. It lends itself to the manufacture of a range of dairy products. The concentration of vitamins, fatty acids, and amino acids present in milk have a marked influence on the nutritional and processability qualities of milk. Given that milk is a complex biological fluid, the analysis of these compounds presents a significant analytical challenge. The overarching aims of this study were to develop microextraction methods and chromatographic separations for the determination of selected compounds from bovine milk which would then be analysed by both High Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC) coupled to various detectors (UV, PDA, MS, FID). As the selected compounds are present in trace amounts significant enrichment was required, it was for this reason that Dispersive Liquid-Liquid Microextraction (DLLME) was utilised for the analysis. DLLME involves the rapid injection of an immiscible extraction solvent into an aqueous sample in the presence of a third dispersive solvent. The third dispersive solvent must be miscible with both the extraction and aqueous phase. Typical examples of dispersive solvents include: ACN, methanol, acetone. This produces a stable emulsion of comprised of micro-droplets of extractant into which the analyte rapidly partitions. Centrifugation of the ternary mixture facilitates recovery of the sedimented extraction solvent prior to analysis. The DLLME methods were optimised using chemometric techniques. The results of the analysis were then used to investigate the changes in fatty acid content over the lactation period (palmitic acid increased from 5.73 mg/mL to 10.85 mg/mL), the effect seaweed supplementation had on the vitamin content of bovine milk (delta tocopherol increased from 3.82 to 5.96 μg/mL), and the differences in free amino acid content between different classes of commercial milk samples (alanine, glycine, and glutamic acid increased during storage).
|Publication status||Unpublished - 2018|
- Chromatographic Analysis