Polarographic determination of the stability constant of the ternary complex formed between cocaine and cobalt thiocyanate

ABSTRACT

The interactions between cocaine -- Co(II) and thiocyanate (or dimethylglyoxime) have been studied by electrochemical means, assuming the existence of a ternary complex with the stoichiometry [(H₂O)₃Co(SCN)(C₁₇H₂₁NO₄)]⁺ and the absence of similar ternary species containing dimethylglyoxime. The formation constant of the complex has been evaluated by polarographic titrations because of the irreversibility of electrochemical processes. This relatively small value of 2.37 × 10⁵ is in agreement with the experimental conditions at which Scott's method is typically carried out to detect cocaine in solid samples by reaction with Co(II) thiocyanate.

KEYWORDS:

• Cocaine
• ternary complex of cobalt
• polarographic determination
• stability constant

Acknowledgments

Authors wish to thank the Delegación del Gobierno en Castilla y León for the kindly provision of the cocaine samples used in this work.

Disclosure statement

There are no financial or other relations that could lead to a conflict of interest.