Cloud point extraction and spectrophotometric determination of amaranth in food samples using nonionic surfactant Triton X-100 and tetrabutylammonium hydrogen sulfate

Cloud point extraction methodology was successfully employed for preconcentration of trace amounts of amaranth prior to its determination by spectrophotometry. The method was based on the extraction of amaranth as an ion pair with tetrabutylammonium ion from aqueous solution using Triton X-100 as non-ionic surfactant. The extracted surfactant rich phase was diluted with ethanol and its absorbance was measured at 518 nm by a spectophotometer. An optimum set of surfactant concentration, pH, equilibration temperature and time, tetrabutylammonium hydrogen sulfate and salt concentration were obtained. The calibration graph was linear in the range of 20–1600 ng ml−1 of amaranth in the initial solution with r = 0.9993 (n = 12). Detection limit based on three times the standard deviation of the blank (3Sb) was 13.0 ng ml−1 (n = 10), and the relative standard deviation (R.S.D) for 100 and 1000 ng ml−1 of amaranth was 4.2 and 1.4% (n = 10), respectively. The proposed procedure was applied to the determination of amaranth in different food samples.