Methods of organic analysis of coffee. II. Comparison of methods of caffeine determination in green coffee

Abstract

The micro Bailey-Andrew method (official of A. O. A. C, 1970) and the proposed reference method of Navellier et al. (1969) for determination of caffeine in coffee were studied. For the caffeine extraction and purification, it was followed the A. O. A. C. (1970) and Navellier et al. (1969) procedures, without modification, but for the caffeine estimation, the weight, total nitrogen, spectrofotometry with base line correction and the peak at 273 nm were used. The following conclusion could be drawn: a) the determination of caffeine by using the weight should not be applied by either methods, because it gave high values in comparison with nitrogen and spectrophotometry, and because of the high coeficient of variation. b) the extration and purification procedures used by Navellier don't remove all nitrogenous materials which interferes on the total nitrogen determination, whereas the Navellier spectrofotometry method gave similar results with the A. O. A. C. (1970) nitrogen and spectrophotometric determinations. c) no diference was found for nitrogen and spetrophotometric (with correction of base line) determination of caffeine when A. O. A. C. (1970) extraction and purification procedures were used.