The characteristic absorption of caffeine at 272 mg is utilized to measure quantitatively its presence in coffees and crude caffeine. Interfering impurities found in these samples are removed by treatment with heavy magnesium oxide and zinc ferrocyanide, plus in some cases permanganate oxidation.
A method for the detection and estimation of aflatoxin B1 in green coffee beans is described. According to the AOAC method, the toxin is extracted with aqueous methanol: hexane and the extract is cleaned up on a Celite column. The extract is further purified on a Florisil column and is then chromatographed on thin layer plates. The estimated limit of detection of the method is 2 μg aflatoxin/kg green coffee. About 75% aflatoxin B1 added to green coffee was recovered. The method was used in a survey of suspect samples of green coffee. No aflatoxin was detected in 58 samples originating in 10 producing countries. Preliminary studies with a new extraction solvent (dimethyl sulfoxide:benzene, 30:50) and a Florisil cleanup appear promising. About 85% aflatoxin B1 added to green coffee was recovered.
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