FLOTATION-SPECTROPHOTOMETRIC DETERMINATION OF TRACE IRON(III) IN NATURAL-WATER SAMPLES WITH 2-CARBOETHOXY-1,3-INDANDIONE SODIUM-SALT

A flotation-spectrophotometric method for the separation and determina tion of Fe(III) in fresh and natural water samples has been developed. The method is based on the colored complex which is formed between Fe (III) and 2-carboethoxy-1,3-indandione sodium salt (CEIDNa). The color ed 1:3 (Fe: reagent) complex is quantitatively floated with oleic acid (HOL) surfactant in the pH range 3-6. The complex in the scum is meas ured directly for iron at lambda = 490 nm. Beer's law is obeyed over t he concentration range 2.8 - 39 mug of Fe(III) in 4 ml of HOL surfacta nt. The molar absorptivity is 0.65X10(4) l mol-1 cm-1. The different f actors affecting the flotation and determination of Fe(III) have been investigated. The determination of Fe(III) after selective flotation i ncreases the sensitivity and eliminates the effect of foreign ions. Th e method was successfully applied to detect as little as 1 ppb Fe in 2 0 ml samples of natural water after flotation with HOL surfactant.