Spectrophotometric determination of Cu(II) with sequential injection analysis

A sensitive method is presented for the determination of the synthetic antioxidant butylated hydroxyanisole (BHA) based on the dansylation process of the phenolic hydroxy group. The fluorescence developed can be measured directly without previous extraction or chromatographic separation of the labelled fluorescent compound. It is shown the effect of numerous experimental variables affecting the fluorescence intensity and the signal-to-noise ratio of the dansyl derivative. The compound was determined over the range 0.05-5 mug ml(-1), with a relative S.D. of 3.8% (300 ng ml(-1)) and a detection limit of 52 ng ml(-1). The selectivity conferred by the dansylation reaction has permitted to avoid the interference of normally accompanying antioxidants, such as butylated hydroxytoluene (BHT), due to steric impediment. The stability of the DNS-derivative is well suited for the analysis of different foodstuffs.