Analysis of riboflavin in beer by capillary electrophoresis/blue light emitting diode (LED)-induced fluorescence detection combined with a dynamic pH junction technique

A simple, inexpensive and reliable method for the routine analysis of riboflavin in beer by capillary electrophoresis-light emitting diode (CE-LED) induced fluorescence detection is described. A simple and straightforward sample preparation is involved and the method is based on an inexpensive blue LED as the light source combined with an on-line sample concentration technique. For this detection system, using a normal micellar electrokinetic chromatography (MEKC), stacking-MEKC and dynamic pH junction techniques, the detection limits were found to be 480, 20 and 1 ng mL⁻¹, respectively. In addition, the number of theoretical plates for riboflavin was determined to be 3.8×10⁴ by means of a dynamic pH junction and this was improved to 3.2×10⁶ when the dynamic pH junction-sweeping mode was applied. The concentrations of riboflavin in 12 samples of different types of commercial beer were found to be in the range of 130-280 ng mL⁻¹.