Two-dimensional thin-layer chromatographic method for the analysis of ochratoxin A in green coffee

Meritxell Ventura, Ivan Anaya, Francesc Broto-Puig, Montserrat Agut, Lluís Comellas

Research output: Indexed journal article Articlepeer-review

22 Citations (Scopus)

Abstract

A low-cost thin-layer chromatographic method has been developed for the presumptive measurement of ochratoxin A (OTA) at 5 μg/kg in green coffee beans. The analytical method consisted of extracting OTA by shaking the beans with a mixture of methanol and aqueous sodium bicarbonate solution, which was then purified by liquid-liquid partition into toluene. OTA was separated by normal-phase two-dimensional thin-layer chromatography and detected by visual estimation of fluorescence intensity under a UV lamp at 365 nm. The chromatography solvents were toluene-methanol-formic acid (8:2:0.03) for the first development and petroleum ether-ethyl acetate-formic acid (8:10:1) for the second dimension development. This method was tested with uncontaminated green coffee bean samples spiked with an OTA standard at four different concentrations (5, 10, 20, and 30 μg/kg). The method is rapid, simple, and very easy to implement in coffee-producing countries. It is highly selective and does not involve the use of chlorinated solvents in the sample extraction step. This inexpensive method has been applied to different types of green coffee samples from various countries (Zimbabwe, Brazil, India, Uganda, Colombia, and Indonesia) and different manufacturers, and no OTA below the detection limit of 5 μg/kg was detected in any samples analyzed.

Original languageEnglish
Pages (from-to)1920-1922
Number of pages3
JournalJournal of Food Protection
Volume68
Issue number9
DOIs
Publication statusPublished - Sept 2005

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