An Anion‐Exchange Sorbent as a Support for Voltammetric Determination of the Ionic Form of Ti(IV) in Soil Extracts

Agricultural and industrial applications of fertilizers containing titanium components lead to the release of ionic Ti(IV) and TiO ₂ into the soil environment, making them mobile and potentially bioavailable. The ionic mobile form has a low content, and interference during the measurement should be expected. Adsorptive stripping voltammetry (AdSV) allows for distinguishing Ti(IV) from TiO ₂ (even in the form of nanoparticles) in soil extracts (0.01 mol L ⁻¹ HCl—stabilization of the ionic form), but the matrix effect often causes an increased LOD value and may render measurements impossible. To overcome this limitation, a solid‐phase extraction technique in a batch mode (Dowex 1 X8) was proposed. Ionic Ti(IV) in the form of a Ti(IV)‐mandelic acid (Ti(IV)‐MA) complex was selectively retained on an anion‐exchange resin and then quantitatively leached with a hydrochloric acid solution. Handling the Ti(IV)‐MA complex rather than the Ti(IV) chloride complex as the retained compound limits potential hydrolysis. The Ti(IV)‐MA complex was directly used in AdSV. The proposed procedure allowed for subnanogram determination in a voltammetric cell, with an LOD recalculated for the subsample ( t _d  = 60 s) equal to 0.084 µg L ⁻¹ (1.4 µg L ⁻¹ in soil extract). The determination of 0.6 ng Ti(IV) (300 µL of eluate in a 10 mL cell) resulted in 101%–115% recovery, confirming the reliability of the separation method.