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Abstract
A flow-injection analysis system for the rapid and sensitive fluorimetric determination of free cyanide is developed. The determination is based on oxidation of nonfluorescent thiamine to highly fluorescent thiochrome (λ ex/λ em = 370/440 nm) in alkaline medium by Cu2+ when CN− is present. After designing an appropriate manifold, the effects of chemical variables, FIA system parameters and temperature on the determination of CN− were studied in detail. Under optimum experimental conditions the working range was linear from 0.02 to 2.5 mg L−1 with a high sampling throughput of 120 h−1 at room temperature. The precision, in terms of relative standard deviations for ten replicates of analysis of 1.0 mg L−1 CN−, was 1.9%. Interference studies were performed with typical cations and anions in natural waters. CN− spiked in synthetic water samples was determined by this proposed FI method with good results. The composition of the reduced product [Cu+(CN−) n ]1− n was determined using an indirect method. In addition, results of cyclovoltammetric measurements of thiamine are reported which throw light on the electrochemical process.
Acknowledgment
The authors gratefully thank the DAAD (DEUTSCHER AKADEMISCHER AUSTAUSCHDIENST) for financial support of this work.