Cellulose mini-membranes modified with TiO₂ for separation, determination, and speciation of arsenates and selenites

Sorptive and selective mini-membranes based on TiO₂ directly synthesized onto cellulose filters (TiO₂@cellulose) have been developed. The in situ synthesis of TiO₂@cellulose applied is simple and economically advantageous. The obtained membranes can be useful for (1) separating arsenic(V) and selenium(IV) from other ions and organic matter, (2) speciation of arsenic and selenium, and (3) determining ulratraces of these ions in water samples. The membranes exhibit good stability and high maximum adsorption capacities for Se(IV) (71 mg g^-1) and As(V) (41 mg g^-1). A monolayer chemical adsorption of analytes on the membranes was confirmed. The structure of membranes was examined with scanning electron microscopy, x-ray diffractometry, and micro energy-dispersive x-ray fluorescence spectrometry (μ-EDXRF). The membranes were characterized by homogenous distribution of TiO₂ onto cellulose. The TiO₂@cellulose was used as a new sorbent in micro-solid phase extraction for determination of Se(IV) and As(V) by EDXRF. Using direct analysis of mini-membranes after sorption of analytes avoids the elution step. Thus, the proposed procedure is an attractive and solvent-free option for quantitative monitoring of Se(IV) and As(V) in different materials. Both analytes were quantitatively and simultaneously separated/determined from samples at pH 2 with very good recovery (close to 100%), precision (4.5%), and detection limits (0.4 ng mL^-1 Se and 0.25 ng mL^-1 As). TiO₂@cellulose membranes were applied to water analysis. Graphical-abstract Effective method for determination of ultra trace arsenates and selenites using cellulose-based sorbent.