LIQUID CHROMATOGRAPHIC DETERMINATION OF SUGARS IN BEER BY EVAPORATIVE LIGHT SCATTERING DETECTION

Abstract
A liquid chromatographic method for the determination of mono- and oligosaccharides in beer was developed using a polymeric NH2 column, a water/acetonitrile gradient and an evaporative light scattering detector (ELSD). The flow rate was 1 ml/min and the column temperature 40°C. The optimum settings of the ELSD parameters were: voltage 600 V, temperature 90°C and nitrogen gas pressure 1.5 bar. The detection limit was about 5 mg/l for lower sugars and about 10 mg/l for higher ones. The detector response varied among different mono- and oligosaccharides, but it was linear up to a concentration of 0.25 g/l. Owing gradient elution, the separation power was much higher than with classical liquid chromatographic methods. Reproducibility of the detector response was not as good as with refractive index detection. Beer samples were prepared by injecting 0.5 ml of beer through a 500 mg C-18 solid-phase extraction tube and flushing the tube with water to make the final volume of each sample 10 ml. 10 μl of sample was injected into the liquid chromatograph. Recovery from beer ranged from 78% to 128% depending on the sugar and its amount added to beer. The highest variations were observed at low concentrations. Maltotetraose was found to be the most abundant sugar in beer, its concentration ranging from 0.7 to 8.4 g/l. The total amount of higher sugars (more than three monosaccharide units) was higher than that of lower ones.