Low-cost and green dispersive solid phase extraction of hydrophilic compounds using titanium dioxide nanoparticles

Selective extraction of hydrophilic compounds is a challenging task for analytical laboratories. In an attempt to address this issue, application of titanium dioxide nanoparticles as a dispersive solid phase extraction sorbent was investigated. In the study, three model analytes were used for method optimization: flavin mononucleotide, thiamine monophosphate and thiamine pyrophosphate. The influence of various parameters on sorption and desorption process was evaluated. Under optimized conditions, the sorption was performed in a presence of 1 M formic acid (pH 1.9) for 10 min under vortex stirring providing efficiency up to 94%. The influence of salt content in sample matrix was found to be negligible while the organic solvent presence slightly improved the sorption efficiency. Elution of analytes from TiO2 sorbent was obtained with both aqueous ammonia and phosphate buffer (pH 11.8) solutions. Under optimized conditions dispersive solid phase extraction method was shown to provide high selectivity with extraction recoveries > 89.0% for studied compounds. The susceptibility of the method on various matrices was assayed for extraction of model analytes from enriched tap water, milk, apple juice and human urine samples. Moreover, the methodology was applied for phospholipids removal from pharmaceutical formulation (lecithin microemulsion) of propofol. Due to the utilization of titanium dioxide nanoparticles, the cost of sample preparation step was estimated to be about 0.1 Euro per sample, providing > 100-fold reduction of the price for typical analysis using titanium dioxide microspheres.