-PYRIDYLAZO)-5-(N-PROPYL-N-SULFOPROPYLAMINO)PHENOL AS A NEW ANALYTICAL REAGENT FOR FLOW-INJECTION SPECTROPHOTOMETRIC DETERMINATION OF TRACEVANADIUM(V)

A flow injection method using 2-(5-nitro-2-pyridylazo)-5- (N-propyl-N- sulfopropylamino)phenol-(Nitro-PAPS) as a new chromogenic reagent is p resented for sensitive and rapid determination of vanadium. Nitro-PAPS reacts with vanadium(V) in weakly acidic medium to form a water solub le complex of molar absorptivity of 8.0 x 10(4) L mol(-1) cm(-1) at 59 2 nm (maximum absorption wavelength), which permits the straightforwar d application of a flow injection system to the sensitive determinatio n of vanadium. Under the optimum conditions established, a linear cali bration graph was obtained in the range 1-120 ng mL(-1). The relative standard deviation for 60 ng mL(-1) vanadium was 2.2% (n = 5) and the limit of detection was 1 ng mL(-1). The sample throughput is about 40 h(-1). Most inorganic and organic anions examined did not interfere ev en at concentrations of 3000-6000 times of vanadium. Interference from cobalt(II), copper(II) and nickel(II) at 200 ng mL(-1) levels can be overcome by the addition of N-(dithio-carboxy)sarcosine. The recoverie s for each 20 and 10 ng mL(-1) vanadium added to the river water were 98 and 97%, respectively.