Integrated supercritical fluid extraction and online ICP-MS nano-gram determination of titanium(IV) using calixarene...

A selective and efficient method was developed for the extraction and trace determination of titanium(IV) using integrated supercritical fluid extraction (SFE) with calixarene hydroxamic acid (CC4AHA), coupled online with inductively coupled plasma mass spectrometry (ICP-MS). The extraction conditions were systematically optimized with respect to temperature, pressure, extraction time, acid molarity, and organic modifier to achieve quantitative recovery of Ti(IV). Optimal extraction was obtained at 50 °C and 17 MPa using dichloromethane-modified supercritical CO₂ in the presence of 8.0 M HCl with an extraction time of 5-6 min, yielding extraction efficiencies greater than 99.9%. Under the optimized conditions, the method showed excellent linearity over the concentration range of 0.23-2.18 ng mL^-1 with a correlation coefficient (R²) exceeding 0.999. The limits of detection and quantification were 0.78 ng mL^-1 and 2.34 ng mL^-1, respectively. Method precision, evaluated by repeatability studies, resulted in relative standard deviation values below 5%, while accuracy assessed through recovery experiments ranged from 96% to 104%. The proposed method was successfully applied to the determination of titanium in certified NBS geological reference materials and real samples, including steel, brass, and ilmenite, with results in good agreement with certified values. The developed SFE-ICP-MS approach offers a rapid, sensitive, and environmentally benign alternative for the ultra-trace determination of titanium in complex matrices.