4. Conclusions
A selective, fast and accurate HILIC method has been developed for the simultaneous determination of creatinine, uric and ascorbic acid in bovine milk and orange juice samples. The HILIC method used a Waters Spherisorb S5NH2 column and a mobile phase consisting of 50% acetonitrile and 50% of 10 mM phosphate buffer at pH 4.75 at a flow rate of 1.2 mL min 1 and a detection wavelength of 205 nm. This method has shown the advantages of the HILIC over reversed-phase HPLC methods for the determination of highly polar small organic compounds with good retention and without ion pairing agent requirement. Good linearity and sensitivity were obtained with this developed method. The detection limits for creatinine, uric and ascorbic acid were 0.045, 0.10 and 0.18 lgmL 1, respectively. The described method was successfully applied to the determination of creatinine, uric and ascorbic acid in bovine milk and orange juice samples. The bovine milk contains significant levels of creatinine and uric acid, which may contribute to the concentration of these metabolites in human fluids. The method has proved simple, robust and sensitive and can be also employed for the routine analysis of other food products and biofluids.