ISO 4052:1983

The method consists in extracting of the caffeine from a test portion, in an ammoniacal medium, successive purifying, with diethyl ether, on two chromatographic columns, the first in an alkaline medium, the second in an acid medium, followed by elution by chloroform. Spectrometric measurement of the eluate at the wavelength of maximum absorbance (in the ultraviolet region). A first figure shows examples of chromatographic columns. A second figure gives an example of spectrometric measurement.