2003 Volume 89 Issue 9 Pages 920-926
Flow injection analysis of antimony in steels using a Teflon (PTFE) tube concentration method was investigated. Antimony reacted with chloride ions in hydrochloric acid solution to form a complex ion SbCl6-. The hexachloroantimony complex anion was adsorbed on the Teflon tube inner surface as ion pair, which was formed with Co(III) complex of 2-(5-chloro-2-pyridilylazo)-5-diethylaminophenol (Co-5-Cl-PADAP). The concentrated ion pair was eluted with 99% methanol, and then the absorbance of the eluate was measured at 560 nm. Excess reagent was adsorbed on the Teflon tube the same as the ion pair, so that reagent blank values were increased with excess reagent. Therefore, the conditions for the removal of excess reagent were examined. As a result, an 8% methanol solution was selected as a rinsing solution, and the removal was carried out for 3 min. The apparatus used in this flow system has four channels. One of them was a 99% methanol eluent. Others were a sample solution containing antimony, hydrochloric acid and sodium nitrite at 1.5 mllmin, a 3×10-5M Co-5-Cl-PADPAP solution at 0.2 m/lmin, and an 8% methanol at 1.3 mllmin. The calibration curve was constructed under optimum conditions by the proposed flow system. A linear relationship between the absorbance and antimony concentration was obtained over the range 0 to 50 ppb. The limits of detection and determination for antimony were 0.3 and 0.9 ppb, respectively. The determination results for antimony in steel certified reference materials showed good agreements with the certified values. The relative standard deviation for 20 ppb Sb was 0.9% (n= 6). The iron as matrix did not interfere with the determination of Sb up to a million-fold to antimony amount.