title: Two-dimensional thin-layer chromatographic method for the analysis of ochratoxin A in green coffee.
abstract: A low-cost thin-layer chromatographic method has been developed for the presumptive measurement of ochratoxin A (OTA) at 5 microg/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 microg/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 microg/kg was detected in any samples analyzed.
authors.affiliation: Analytical Chemistry Department, Institut Química de Sarrià (Ramon Llull University), Via Augusta 390, 08017 Barcelona, Spain. mvenben@iqs.es
authors.forename: Meritxell
authors.initials: M
authors.lastname: Ventura
authors.forename: Ivan
authors.initials: I
authors.lastname: Anaya
authors.forename: Francesc
authors.initials: F
authors.lastname: Broto-Puig
authors.forename: Montserrat
authors.initials: M
authors.lastname: Agut
authors.forename: Lluís
authors.initials: L
authors.lastname: Comellas
mesh_terms: D002855:Chromatography, Thin Layer / Q000379:methods*; D003069:Coffee / Q000737:chemistry*; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D005506:Food Contamination / Q000032:analysis*; D009793:Ochratoxins / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D003069:Coffee; D009793:Ochratoxins; C025589:ochratoxin A