title: A multi-pumping flow-based procedure with improved sensitivity for the spectrophotometric determination of acid-dissociable cyanide in natural waters.
abstract: An analytical procedure with improved sensitivity was developed for cyanide determination in natural waters, exploiting the reaction with the complex of Cu(I) with 2,2'-biquinoline 4,4'-dicarboxylic acid (BCA). The flow system was based on the multi-pumping approach and long pathlength spectrophotometry with a flow cell based on a Teflon AF 2400(®) liquid core waveguide was exploited to increase sensitivity. A linear response was achieved from 5 to 200μg L(-1), with coefficient of variation of 1.5% (n=10). The detection limit and the sampling rate were 2μg L(-1) (99.7% confidence level), and 22h(-1), respectively. Per determination, 48ng of Cu(II), 5μg of ascorbic acid and 0.9μg of BCA were consumed. As high as 100mg L(-1) thiocyanate, nitrite or sulfite did not affect cyanide determination. Sulfide did not interfere at concentrations lower than 40 and 200μg L(-1) before or after sample pretreatment with hydrogen peroxide. The results for natural waters samples agreed with those obtained by a fluorimetric flow-based procedure at the 95% confidence level. The proposed procedure is then a reliable, fast and environmentally friendly alternative for cyanide determination in natural waters.
authors.affiliation: Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, 13400-970, PO Box 96, Piracicaba, SP, Brazil.
authors.forename: Rejane M
authors.initials: RM
authors.lastname: Frizzarin
authors.forename: Fábio R P
authors.initials: FR
authors.lastname: Rocha