Determination of trigonelline, nicotinic acid, and caffeine in Yunnan Arabica coffee by microwave-assisted extraction and HPLC with two columns in series.

摘要

A simple, rapid method was developed for simultaneous extraction of trigonelline, nicotinic acid and caffeine from coffee, and separation by 2 chromatographic columns in series. Trigonelline, nicotinic acid and caffeine were obtained by microwave-assisted extraction (MAE). The optimal conditions selected were 3 min, 200 psi and 120 degrees C. Chromatographic separation was performed with 2 columns in series, polyaromatic hydrocarbon C18 (250 x 4.6 mm id, 5 mum particle size) and Bondapak NH2 (300 x 3.9 mm id, 5 mum particle size). Isocratic elution was conducted with 0.02M phosphoric acid-methanol (70 + 30, v/v) mobile phase at a flow rate of 0.8 ml/min. Good recoveries and RSD values were found for all analytes in the matrix. The LOD of the 3 compounds was 0.02 mg/l and the LOQ was 0.005% in the matrix. Concn. of trigonelline, nicotinic acid and caffeine in instant coffee, roasted coffee and raw coffee (Yunnan Arabica coffee) were assessed by MAE and hot water extraction; correlation coeff. between concn. of the 3 compounds obtained were close to 1.