Determination of the mycotoxin moniliformin in cereals by high-performance liquid chromatography and fluorescence detection

The development of a selective and sensitive high-performance liquid chromatography-fluorescence assay for the determination of the mycotoxin moniliformin in plant extracts is described. By means of introducing a derivatization reaction with 1,2-diamino-4,5-dichlorobenzene (DDB) we succeeded in increasing the overall determination sensitivity and the chromatographic selectivity on a RP-HPLC system. Due to the phenolic character of the derivative a bathochromic UV shift from 315 to 330 nm (phenole-->phenolate) at pH 10-12 was observed. Moreover, and in contrast to the DDB reagent at pH 10-12 the moniliformin-DDB derivative showed fluorescence activity with lambda(Ex)=330 nm and lambda(Em)=440 nm, which led to the benefits that the excess of DDB did not have to be removed from the sample solution. The pH-shift was accomplished via on-line post-column effluent mixing of the RP-18 eluent using an auxiliary HPLC pump and a buffer of pH 12.00. The fluorescence detection enables the reduction of the determination limit of moniliformin from 0.05 (UV detection) to 0.02 mg/kg maize.