Four simple, rapid, and accurate spectrophotometric methods were developed for the simultaneous determination of two food colorants, Carmoisine (E122) and Ponceau 4R (E124), in their binary mixtures and soft drinks. The first method is based on recording the first derivative curves and determining each component using the zero-crossing technique. The second method uses the first derivative of ratio spectra. The ratio spectra are obtained by dividing the absorption spectra of the binary mixture by that of one of the components. The third method, derivative differential procedure, is based on the measurement of difference absorptivities derivatized in first order of solution of drink samples in 0,1 N NaOH relative to that of an equimolar solution in 0,1 N HCl at wavelengths of 366 and 451 nm for Carmoisine and Ponceau 4R, respectively. The last method, based on the compensation method is presented for derivative spectrophotometric determination of E122 and E124 mixtures with overlapping spectra. By using ratios of the derivative maxima, the exact compensation of either component in the mixture can be achieved, followed by its determination. These proposed methods have been successfully applied to the binary mixtures and soft drinks and the results were statistically compared with the reference HPLC method (NMKL 130).

Sumac Leaves (SL) (Rhus Coriaria L. ) were investigated as an inexpensive and effective adsorbent for the adsorption of methylene blue (MB) from aqueous solution. The effects of initial dye concentration, initial solution pH, phases contact time, and adsorbent dose on the adsorption of MB on SL were investigated. The amount of dye adsorbed was found to vary with initial solution pH, Sumac Leaves dose, MB concentration, and phases contact time. The Langmuir and Freundlich adsorption models were evaluated using the experimental data and the experimental results showed that the Langmuir model fits better than the Freundlich model. The maximum adsorption capacity was found to be 151.69 mg/g from the Langmuir isotherm model at 25°C. The value of the monolayer saturation capacity of SL was comparable to the adsorption capacities of some other adsorbent materials for MB. The adsorption rate data were analyzed according to the pseudo-first order kinetic and pseudo-second order kinetic models and intraparticle diffusion model. It was found that kinetic followed a pseudo-second order model.

A simple, rapid, and sensitive spectrophotometric method was developed for the simultaneous determination of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) concentration in pharmaceutical preparations and chewing gums, without prior separation steps, using the H-point standard addition method (HPSAM).The concentration of one antioxidant was calculated by overlapping spectra at two appropriately selected wavelengths at which the interferent, other antioxidant, should has the same absorbance value. Absorbances at two pairs of wavelengths, 265 and 288 nm (with BHA as analyte) or 288 and 293 nm (with BHT as analyte) were monitored, while adding standard solutions of BHA or BHT, respectively. Calibration graphs were determined at 4–20 μgml–1(r = 0.9981) for BHA and 20–100 μgml–1(r = 0.9940) for BHT in binary mixtures. The proposed method was tested and validated using various parameters according to ICH guidelines. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.48 and 1.51 μgml–1for BHA and 0.72 and 2.41 μgml–1for BHT, respectively. The percentage recovery ranges were 100.44–102.50 % for BHA and 96.45–100.04 % for BHT, with relative standard deviations (RSD) less than 1.48 % indicating reasonable repeatability of the method. The intra-day and inter-day precision tests showed reliable RSD values (< 2 %). The results obtained using HPSAM were statistically compared with results obtained using the derivative spectrophotometric method that was previously reported by us, showing high similarity between results.