Cloud-Point Extraction and Fluorospectrophotometric Determination of Rhodamine B in Water Samples

摘要

A new micelle-mediated cloud point extraction method is described for the sensitive and selective determination of trace amounts of Rhodamine B by fluorospectrophotometry. The method is based on the cloud point extraction of Rhodamine B from aqueous solutions using [sodium dodecyl benzene sulfonate (SDBS)] anionic surfactants in neutral media. The method does not require any organic solvent in the extraction process. The extracted surfactant-rich phase is diluted with methanol and its fluorescence intensity is measured at 547 nm using a fluorospectrophotometer. The effects of different operating parameters such as the concentrations of surfactant and salt, temperature and pH on the cloud point extraction of Rhodamine B are studied and a set of optimum conditions are determined. Under the optimum conditions, a linear calibration graph ranging within 0.02-14 ng/mL of Rhodamine B in the initial solution with r = 0.9992 (n = 5) is obtained. The detection limit based on three times the standard deviation of the blank (3Sb) is 0.006 ng/mL (n = 11) and the relative standard deviation for 10 ng/mL of Rhodamine B is 3.1 % (n = 5). The method is used to detect Rhodamine B in a tap water sample and a contaminated water sample from a dyestuff factory.