Determination of trace amounts of Brown HT as a food dye by a CPE-scanometry method

Abstract

In this study, trace amounts of Brown HT were extracted, pre-concentrated and determined by cloud point extraction-scanometry (CPE-scanometry) as a simple, fast and inexpensive method. The procedure is based on CPE of Brown HT from an aqueous solution, diluting the extracted surfactant-rich phase with ethanol to 500 L, transferring the appropriate volume to Plexiglas ® cells and scanning the cells. Then, the colour of each cell was analyzed by software written in visual basic (VB 6) into red, green and blue values. Effective parameters for the extraction efficiency, such as the pH of the system, the concentration of surfactant, the equilibration temperature and equilibration time, were investigated and optimized. Under optimal conditions, the calibration curve was linear in the range of 0.06-2.60 mg L −1. The detection limit of the proposed method was 0.04 mg L −1. In addition, the effects of some foreign species, including cations, anions and dyes, were investigated. The method was applied successfully for the determination of Brown HT in some water samples.

Cloud Point Extraction as a Method for Preconcentration of Metal Ions

“…If a solution in which the surfactant concentration is above the critical micellar concentration (CMC) is heated to a certain temperature (cloud point temperature, T C P E ), then the surfactant molecules form micelles that create an additional phase, which is manifested by turbidity of the solution, i.e. a cloud point is reached (Shokrollahi & Ahmadi 2017). This phase is called the surfactant-rich phase because it contains most of the surfactant, is heavier than the aqueous phase, and therefore separates the phases as shown in Figure 1.…”

Cloud point extraction procedure for preconcentration and determination of lead(II) ions using triton X-100 at room temperature

“…Different techniques, such as Solid Phase Extraction (SPE), Liquid-Liquid Extraction (LLE), Liquid-Liquid Microextraction (LLME) and coprecipitation techniques are widely used for preconcentration purposes (7)(8)(9). However, these conventional separation methods are usually time consuming and require relatively large amounts of high purity solvents which are often toxic and a special disposal method is needed (10). Cloud point extraction (CPE) is an attractive technique in recent decade, due to its several advantages such as low cost, safety (reduction of solvent consumption and exposure to toxic organic solvents), less stringent requirements for separation, higher preconcentration factor, easier manipulation and the duration of the procedure (11).…”

“…The CPE method has important practical application for separation and refocuses the analyte as a step before its determination, and after its formation in the water of a poorly soluble complex. CPE experiments reported previously (10)(11)(12)(13)(14) are based on behavior of nonionic surfactants, at their respective ″cloud point temperature″ when formation of ″surfactant-rich phase″ enables preconcentration of analyte. Nonionic surfactant solutions become turbid at their ″cloud point temperature″ and, consequently the micellar solution separates into two phases: a surfactant-rich phase and an essentially bulk aqueous phase (15).…”