Determination of trace amounts of vanadium by UV-vis spectrophotometric after separation and preconcentration with modified natural clinoptilolite as a new sorbent.

Natural clinoptilolite was used as a sorbent material for solid phase extraction and preconcentration of vanadium. The clinoptilolite was first saturated with a cation such as nickel(II) and then modified with benzyldimethyltetradecyleammonium chloride (BDTA) for increasing sorption of 4-(2-pyridylazo)resorcinol (PAR). Vanadium-PAR complex was quantitatively retained on the sorbent by the column method at the pH range 6.2-7.0 at a flow rate of 1 mL min(-1). It was removed from the column with 5.0 mL of dimethylformamide solution at a flow rate of 0.8 mL min(-1) and determined by UV-vis spectrophotometry at lambda(max) = 550 nm. 0.031 microg of vanadium can be concentrated from 450 mL of aqueous sample (where detection limit as 0.07 ng mL(-1) with preconcentration factor of 90). Relative standard deviation for eight replicate determination of 5.0 microg of vanadium in final solution is 2.1%. The interference of number of anions and cations has been studied in detail to optimize the conditions and method was successfully applied for determination of all vanadium as V(IV) form in standard samples.