Analysis of beverages and bacterial nutrient media by hydrophilic interaction liquid chromatography using zwitterionic stationary phases

Novel stationary phases with various zwitterionic fragments in the structure of the functional layer with different degrees of branching were used for the determination of organic acids, sugars, nucleosides, and vitamins in various samples. A decrease in efficiency with an increase in the branching degree of the resin’s functional layer was observed for all studied classes of analytes. Therefore, the least branched stationary phase obtained using 1,4-butanediol diglycidyle ether (B) and glycine (G) was used for the determination of nucleosides and nucleobases in bacterial nutrient media. Complete resolution of water-soluble vitamins, namely, thiamine and nicotinamide was achieved on a resin with a more branched layer containing taurine in its inner part. It was established for organic acids that the decrease in efficiency with increasing branching degree is compensated by increasing the strength and an amount of acidic groups in the zwitterion structure. As a result, the stationary phase with taurine (T) and iminodiacetic acid (IDA) in the structure of a branched layer was selected for determining organic acids in various beverages exhibiting superior separation capability and exceeding the performance of the known commercially available phases. The use of taurine for creating a hyperbranched layer also positively affected carbohydrate separation due to improved selectivity and increased efficiency. Consequently, the resin with glycine in the inner layer and taurine in the outer layer was used for rapid carbohydrate determination in sweetened beverages. Analyte identification was performed by comparing retention times with those of peaks in standard solutions. The calibration range was chosen based on the expected content in analyzed samples as well as analyte solubility in aqueous-organic mobile phases. Accuracy was evaluated by spike recovery experiment. The concentrations of compounds of different classes found with using novel stationary phases in real samples corresponded to those declared by manufacturers.