Development and Validation of an Effective Spectrophotometric Method for Simultaneous Determination of Synthetic Colorants After Cloud Point Extraction and Comparision with New Green HPLC Method
Authors: Üstün Özgür Mahmure , Delmidan Merve 
Published: January 2019

Abstract
Background: Synthetic colorants are largely used in the pharmaceutical products to increase the attractiveness of products and to help patients distinguish between pharmaceuticals. Despite their commercial advantages, synthetic colorants may, in some cases, have a negative impact on the human body. It is therefore imperative to measure the quantities in food products and pharmaceuticals with a fast, reliable, and sensitive method. Objective: The analyzed synthetic colorants in this study are Erythrosine [(E) E127], Quinoline Yellow [(QY) E104], and Indigo Carmine [(IC) E132]. The aim of this study was to develop and validate a new method for the preconcentration and simultaneous determination of these colorants in pharmaceutical preparations. Method: The developed method has many advantages such as novelty, sensitivity, cost effectiveness, speed, and environmental friendliness. This method is based on the cloud-point extraction (CPE) method coupled with first-derivative spectrophotometry (FDS). In the proposed method, QY, E, and IC were extracted from an aqueous solution by using mixed micelles of TritonX-100 and cetyltrimethylammonium bromide. The effect of the main parameters such as solution pH, surfactant and salt concentration, incubation time, and temperature on the CPE of colorants were investigated and optimized. Under the optimal conditions, the extracted surfactant-rich phase was diluted with acetone, and the first-derivative absorbance values were measured at wavelengths 408, 497, and 637 nm for QY, E, and IC, respectively. The CPE-FDS method was applied in the range of 1.0–6.0 μg/mL for E and QY, and 0.3–1.8 μg/mL for IC. Results: The results showed higher correlation coefficients of 0.9990–0.9993 for each colorant. Furthermore, the method was validated for precision and accuracy and assessed the colorants’ contents in the synthetic mixtures that contained different ratios of colorants and pharmaceutical samples. The LOD and LOQ values were 31.0 and 103.0 ng/mL for E, 57.0 and 190.0 ng/mL for QY, and 48.0 and 160.0 ng/mL for IC, respectively. The RSDs at the intermediate concentration level (1.2 μg/mL for IC and 3 μg/mL for QY and for E) were &lt;5%. The recovery values in different ratios of colorants were in the ranges of 90.42–101.14, 92.40–105.54, and 96.15–101.25% for E, IC, and QY, respectively. CPE-FDS was also successfully applied to the simultaneous analysis of the QY, IC, and E contents in the various pharmaceutical samples. The obtained results were statistically compared with those obtained by the green HPLC method that was previously reported by Yoshioka et al. and modified by us in this study. Conclusions: The data observed indicated that the CPE-FDS method does not require use of great samples for determination of trace amounts of E, IC, and QY and allows for the determination of analytes in high matrix effect samples such as suspension and syrup. The study concludes that the proposed CPE-FDS method could be considered an alternative to the existing chromatographical methods for the simultaneous determination of trace amounts of E, IC, and QY in pharmaceutical dosage forms for routine analysis. Highlights: A new and effective procedure, simultaneous determination, trace amounts of E, QY, and IC was developed. This is the first report that uses CPE coupled with FDS for the analysis of E, QY, and IC. CPE avoids the use of costly, hazardous, and flammable solvents in large quantities. FDS resolves two or three overlapping spectra and eliminates matrix interferences. CPE-FDS did not require use of large samples for determination of trace colorants.