Postcolumn excitation of aflatoxins using cyclodextrins in liquid chromatography for food analysis.
Measurement of fluorescence increase was used for the comparative quantification of the effect that several cyclodextrins (alpha-, beta-, heptakis-2,6-beta-omicron-dimethyl- and gamma-) produce on the fluorescent response of aflatoxins B1 and G1. This constitutes a new chromatographic method with stability of the mobile phase, and shows general improvements in the chromatographic conditions with respect to other methods (especially those using an iodine reservoir as a postcolumn reactor). A C18-type column was used, with methanol-water (60:40, v/v) as the mobile phase. The excitation phase of the natural fluorescence of aflatoxins, a 10(-2) M solution of each cyclodextrin, was introduced postcolumn. The determination of the elution order aflatoxin G2 > G1 > B2 > B1 was performed for each phase in less than 15 min. As expected using an aqueous-alcoholic medium, an increase in the fluorescence response of aflatoxins with an unsaturated furanic ring was found to occur with all the cyclodextrins studied, except gamma-cyclodextrin. The observed increase was larger for heptakis-2,6-beta-omicron-dimethyl- than for beta-cyclodextrin (to our knowledge, the only cyclodextrin previously described in the literature to serve for the determination of aflatoxins). The difference is of the order of 70.1-fold in the case of aflatoxin G1 and 45.2-fold in the case of aflatoxin B1. The detection limit in the mobile phase used was determined (for aflatoxin B1) for beta-cyclodextrin and 2,6-beta-omicron-dimethylcyclodextrin (signal-to-noise ratio 1:3) to be 4 and 9 mg 1(-1), respectively.
Cepeda
A
A
Laboratorio de Higiene e Inspección de Alimentos, Universidad de Santiago de Compostela, Lugo, Spain.
Franco
C M
CM
Fente
C A
CA
Vázquez
B I
BI
Rodríguez
J L
JL
Prognon
P
P
Mahuzier
G
G
D016604:Aflatoxin B1 / Q000032:analysis; D000348:Aflatoxins / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods* / Q000706:statistics & numerical data; D003505:Cyclodextrins; D005453:Fluorescence; D005504:Food Analysis / Q000379:methods*; D005506:Food Contamination; D047392:beta-Cyclodextrins
D000348:Aflatoxins; D003505:Cyclodextrins; D047392:beta-Cyclodextrins; C027955:aflatoxin G1; C038119:heptakis(2,6-O-dimethyl)beta-cyclodextrin; D016604:Aflatoxin B1; C031215:betadex