Cobalt Thiocyanate
Definition
Co(SCN)2 in aqueous solution; the active reagent in the Scott test for cocaine. Cocaine forms a lipophilic blue complex with cobalt thiocyanate that partitions into organic solvents such as chloroform, whereas most other bases do not survive the HCl wash step and chloroform partition with the same colour.
- Formula
- Co(SCN)2 aqueous solution
- Test name
- Scott test
- Target analyte
- Cocaine
- Positive result
- Blue complex partitioning into chloroform
Common questions
Why does the Scott test include an HCl wash and chloroform partition step?+
Many bases can form a blue cobalt thiocyanate complex, so the HCl wash strips the complex back into the aqueous phase and most interfering compounds fail to re-partition into chloroform on re-basification, while cocaine's complex survives the cycle and reappears blue in the organic layer.
Is a positive cobalt thiocyanate result enough to confirm cocaine?+
No. Like other colour tests it is presumptive only, and a positive result must be followed by an instrumental confirmatory method such as GC-MS before the substance can be reported as cocaine.
Related terms
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