Photoacoustic spectroscopy as a tool for determination of food dyes: comparison with first derivative spectrophotometry.

Photoacoustic spectroscopy (PAS) was applied as a method to quantify dyed food samples, and was compared with First Derivative Spectrophotometry (FDS). The dyes Brilliant Blue (B), Sunset Yellow (S) and Tartrazine (T), which are common food additives, were employed for the comparisons. Polyester-type Polyurethane (PU) foam was used for extraction of the dyes from a solution containing the food matrix. For the spectrophotometric determinations, the adsorbed dyes were recovered by using dimethylformamide. The PAS measurements were carried out directly on the PU foam. The PAS method showed greater sensitivity, with detection limits of 0.028 mg L(-1) and 0.086 mg L(-1) for S and T, respectively, in the S+T mixture, and of 0.012 mg L(-1) and 0.068 mg L(-1) for B and T, respectively, in the B+T mixture. The values of relative error obtained for all the dyes were small: approximately 0.3-3.6% for the spectrophotometer, and approximately 0.1-2.9% for the PAS method. The PAS technique can be applied to the determination of the selected dyes in commercial food products, with some advantages: it reduces the number of analysis steps, it is a "green" method with less chemical waste, a minimal sample amount is needed, and it is non-destructive.