Simultaneous determination of the colorants tartrazine, ponceau 4R and sunset yellow FCF in foodstuffs by solid phase spectrophotometry using partial least squares multivariate calibration.

A method is proposed for the simultaneous determination of the colorants tartrazine (TT), sunset yellow FCF (SY) and ponceau 4R (PR) in foods. The colorants were fixed in Sephadex DEAE A-25 gel at pH 2.0 and then packed in a 1-mm silica cell. The spectra of the analytes fixed in the solid support were recorded between 400 and 800 nm against a blank and the partial least squares (PLS) multivariate calibration was used to obtain the results. The linear dynamic ranges of the calibration graphs were from 50.0 to 650.0 ng ml(-1) for the three colorants and these ranges were taking in account the optimisation of the calibration matrix using the PLS-1 algorithm. The experimental results showed that the optimum number of factors for the calibration matrix was four in all instances and the residual means standard deviation was 5.5267 for SY, 6.3878 for TT and 6.9816 for PR. The square of the correlation coefficients were 0.9977, 0.9978 and 0.9954 for SY, TT and PR respectively. The method was applied to the determination of the colorants in foods and results were compared with those obtained by means of HPLC as reference method. The results obtained can be considered as acceptable in most cases (eight of nine commercial samples). The relative standard deviations ranging between 0.5 and 10.8 for the commercial samples analysed.

Simultaneous determination of the colorants sunset yellow FCF and quinoline yellow by solid-phase spectrophotometry using partial least squares multivariate calibration.

A method for the simultaneous determination of the colorants Sunset Yellow FCF and Quinoline Yellow using solid-phase spectrophotometry is proposed. The colorants were isolated in Sephadex DEAE A-25 gel at pH 5.0, the gel-colorants system was packed in a 1 mm silica cell and spectra were recorded between 400 and 600 nm against a blank. Statistical results were obtained by partial least squares (PLS) multivariate calibration. The optimized matrix by using the PLS-2 method enables the determination of the colorants in artificial mixtures and commercial soft drinks.

A solid-phase spectrophotometric method for the determination of sulphathiazole.

A spectrophotometric method for the determination of sulphathiazole (ST) has been developed, based on solid-phase spectrophotometry. The influence of experimental variables on fixation on Sephadex SP C-25 is discussed. The applicable concentration range is 0.10-10.00 mg/l., with a relative standard deviation of 0.62% and a detection limit of 0.02 mg/l. The accuracy and precision of the method are reported. The proposed method has been satisfactorily applied to the determination of sulphathiazole in pharmaceuticals.