On-line preconcentration system for vanadium determination in drinking water using FI-ICP-OES

WUILLOUD, RODOLFO G.; GÁSQUEZ, JOSÉ A.; SALONIA, JOSÉ A.; OLSINA, ROBERTO A.; MARTINEZ, LUIS D.

Concepción-Pucón

Simposio; SIXTH RIO SYMPOSIUM ON ATOMIC SPECTROMETRY; 2000

Universidad de Concepción

Vanadium compounds can be highly toxic to man and animals and their presence in the atmosphere is mainly due to the combustion of fossil fuels, which have important vanadium contents. However, vanadium is an essential trace element, possessing specific physiological functions and its determination is receiving increasing attention in pollution and nutritional studies. Since one of the routes of incorporation of vanadium into the human body is drinking water, its determination in this type of samples becomes very important. The concentration of V in drinking water is very low, in the order of a few ug/L, therefore are required powerful techniques and only few techniques show sufficient sensitivity.Inductively coupled plasma optical emission spectrometry (ICP-OES) or electrothermal atomisation atomic absorption spectrometry (ETAAS) are the most used techniques in the determination of traces of vanadium, the low level of vanadium concentration in water is not compatible with the detection limit of these techniques. In order to achieve accurate, reliable and sensitive results, preconcentrations and separations are needed when the concentrations of analyte elements in the sample are too low to be determined directly by ICP-OES.When preconcentration techniques are applied in batch mode, the time of analysis increases and the operations are usually too tedious to be compatible with the ICP-OES measurements. Furthermore, these procedures are not practical for application in routine analysis. This situation has been significantly improved utilising flow injection (FI) associated with ICP-OES.In order to be used as packing in preconcentration columns for FI, materials have to meet several requirements. Among these are: appropriate kinetic and mechanical conditions so that they can easily retain and elute the analyte and, capacity to perform several retention and elution runs without exhaustion of column material. XAD resins meet many of these requirements and have been used as supports for immobilisation of chelating agents and metal complexes.2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) forms stable complexes and has been used as a reagent in the spectrophotometric determination of numerous metallic ions, including vanadium. Therefore, the 5-Br-PADAP is a suitable reagent for vanadium preconcentration on a XAD resin.In the present work, a method for preconcentration and determination of vanadium using a microcolumn filled with a macroporous resin Amberlite XAD-7 is proposed. Vanadium was retained under the form of V-(5-Br-PADAP) complex. The determination was performed using ICP-OES associated with a FI methodology.The detection limit value for the preconcentration of 50 ml of aqueous solution of V was 0.04 ug/L with a relative standard deviation (RSD) of 2.5%, calculated with the peak heights obtained.The method was successfully applied to the determination of vanadium in drinking water samples.