US EPA

8256884 

Journal Article 

Indirect determination of cyanide ion in water by atomic absorption spectrophotometry (Indirect atomic absorption spectrophotometric method for the determination of anions with thiourea-copper (I) complex and its related compound (II) 

Matsueda, T 

1983 

1 

Bunseki Kagaku / Analysis Chemistry
ISSN: 0525-1931 

32 

6 

373-377 

English 

10.2116/bunsekikagaku.32.6_373 

A method was developed for the determination of cyanide ion in water. It is based on the extraction of the ion-pairs formed between cyanide ion and thiourea-copper (I) complex with methyl isobutyl ketone (MIBK). An addition of thiourea to an aqueous solution of copper (II) results in the formation of various thiourea-copper (I) complexes, which are ex-tractable into the MIBK as ion-pairs with cyanide ion. The extracted cyanide ion can be determined by measurement of copper in the MIBK layer by atomic absorption spectrophotometry. The effect of pH, the molar ratio of thiourea to copper (II), and the concentration of thiourea-copper (I) complex on the determination of cyanide ion were examined. The recommended procedure is as follows: In a 35 ml graduated test tube place a neutralized sample solution containing less than 25 µg of cyanide ion, add 2.5 ml of 1 M acetate buffer solution of pH 3.7, 1 ml of 0.075 M copper sulfate solution, and 1 ml of 0.3 M thiourea solution and then adjust the volume to 25 ml with water. Shake the mixture vigorously for several seconds and allow to stand for 5 min. Add 5 ml of MIBK and then shake the mixture for 1 min, and allow to stand for 5 min. Aspirate the MIBK layer directry to atomic absorption apparatus and measure the absorbance for copper. A linear relationship was observed between the absorbance and the amounts of cyanide ion in water in the range of (1~25) µg/25 ml. The precision (C. V.) was 1.7% for cyanide ion of 5µg/25 ml. The interference of metal cations was not so serious, but such anions as halides, nitrate, perchlorate, thiocyanate, and alkylbenzenesulfonate strongly interfered. The interferences were successfully removed by distillation. The cyanide ion in practical samples separated previously from foreign anions by distillation. The proposed method was applied to the determination of cyanide ion in waste water and synthetic samples. The values determined by the proposed method agreed very closely with those obtained by the spectrophotometric method. © 1983, The Japan Society for Analytical Chemistry. All rights reserved. 

atomic absorption spectrophotometry; determination of cyanide ion; ion-pair extraction of cyanide; thiourea-copper (I) complex