Determination of trigonelline in coffee powder and instant coffee by ultrasonic extraction and high performance liquid chromatography

A method of high performance liquid chromatography was established for the analysis of trigonelline in coffee powder and instant coffee. The separation was performed on a BondPak NH2 column (250 mm x 4.6 mm, 5 mu m). The mobile phase was methanol-water (82: 18, v/v) at a flow rate of 0.8 mL/min. The detection wavelength was set at 260 nm. The method had good linearity in the range of 1 - 40 mg/L (the correlation coefficient was 0.9998). The repeatability of the method was performed at one day, different days, and by two analysts. The accuracy of the method was evaluated by recovery study. The recoveries were more than 90% with the relative standard deviations less than 3%. The contents of trigonelline in samples were assessed with ultrasonic extraction and hot water extraction, separately, and the regression coefficient between trigonelline contents obtained under the two extraction methods was 0.9964. The method is simple, rapid, highly sensitive, and suitable for the analysis of trigonelline and quality control of coffee samples.