SPECTROPHOTOMETRIC DETERMINATION OF ALLURA-RED (R40) IN SOFT DRINK POWDERS USING THE UNIVERSAL CALIBRATION MATRIX FOR PARTIAL LEAST-SQUARESMULTIVARIATE METHOD

The Kool-Aid powders (Kraft General Foods) contain one or two of the f ollowing dyes: Allura Red (FD and C Red-40, R40), Sunset Yellow (FD an d C Yellow-6, Y6) Tartrazine (FD and C Yellow-5, Y5), Erythrosine B (F D and C Red-3, R3), Amaranth (FD and C Red-2, R2) and Brilliant Blue F CF (FD and C Blue 1, B1), depending on the taste of the drink. In this work the ''universal'' calibration matrix is proposed for the determi nation of R40 in soft drink powders by partial least squares method us ing spectrophotometric data. The training set of samples consists of 2 3 solutions: three of them contain only R40 at different concentration s and the rest of them are the binary mixtures of R40 with one of the following dyes: R3, R2, Y5 or Y6; all at the concentrations varying in the range 2-22 mg l(-1) (exception: R3 2-12 mg l(-1)). The good analy tical performance of R40 calibration was obtained (R(2)=0.9993, RMSD=0 .2125, REP=2.20%) and this calibration matrix was applied to the analy sis of the real samples containing only one dye (R40) and to the sampl es containing also other dyes, commonly used as the color additives in drink powders. The results obtained were compared with the results of the official spectrophotometric method and with the results of PLS al gorithm for different binary dye calibration matrices. A good statisti cal agreement was obtained in each case, which confirms that some inte rferences occurring in spectrophotometric determinations can be elimin ated using PLS algorithm and including some possibly interfering compo unds in calibration samples.