Development and optimization of a spectrophotometric method with cloud point extraction for determination of gadolinium

This work describes a simple, sensible, and low-cost analytical method, based on cloud-point extraction (CPE) of the surfactant (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114), for the efficient extraction and sensible determination of gadolinium after its complexation with 1-(2-pyridylazo)-2-naphthol (PAN) and subsequent determination by ultraviolet-visible molecular absorption spectrophotometry at the wavelength of 556 nm. Full two-level and Doehlert experimental designs were applied to investigate and optimize the variables (pH, complexing concentration, and TX-114 concentration) involved in the extraction efficiency of Gd3+. The CPE was satisfactory for the determination of gadolinium with limits of detection (LoD) and quantification (LoQ) of 1.0 and 3.2 mu g L-1, respectively, as well as an enrichment factor of 9.4. Accuracy was confirmed by spike tests with recovery values between 98.4 and 78.3%. The precision was expressed as relative standard deviation (%RSD, n =3), being found: 2.3% (10 mu g L-1) and 2.7% (100 mu g L-1). The proposed analytical method is suitable for the determination of Gd in tap water and contrast agent solutions.