INTRODUCING A NEW METHOD FOR THE DETERMINATION OF ULTRATRACE LEVELS OF V(V) AND V(IV) BASED ON A DUAL COLUMN FI-SPE-ET AAS SYSTEM

MANUELA KIM, MABEL TUDINO

Salvador, Bahía, Brasil

Simposio; 10th Rio Symposium on Atomic Spectrometry; 2008

There are few works devoted to inorganic vanadium speciation, mainly due to the complexity of vanadium chemistry (multiple oxidation states, hydrolysis, polimerization) and the low concentrations usually occurring in the nature. However, the different oxidation states play an important role in environmental chemistry as they influence the properties of vanadium as a toxic or a nutrient. In the present work, we present a speciation strategy based on a FI system (see Figures 1 and 2 for sample load and elution) holding two microcolumns set in parallel and filled with two different packaging materials: organic-inorganic hybrid mesoporous silica functionalized with 3-aminopropyl groups (APS20%) at pH 3 for V(V) sorption in anionic form (HVO4-), and mesoporous silica MCM-41 at pH 5 for V(IV) retention in cationic form (VO2+).  The sample, conditioned with HCl at pH=3, is loaded onto the system and both analytes are retained as follows: V(V) onto the first column and V(IV) onto the second after pH conditioning with ammonia. V(V) and V(IV) are then eluted with hydroxilammonium chloride 0.1 mol L-1 in HCl 0.5 mol L-1 . Two sequential analytical signals are obtained in the electrothermal atomizer: one corresponding to V(V) which is reduced by the eluent and released as a cation and another corresponding to V(IV) which is simply released by changing pH. Under optimized conditions analytical performance will be discused in terms of limit of detection, RSD%, sensitivity, microcolumns lifetime, etc.       Figure 1: FI system for sample loading into microcolumns. Adsorption flow rate: 1 mL min-1   Figure 2: FI system for sample elution into the vessels. Elution flow rate: 0.5 mL min-1