Modified cobalt thiocyanate presumptive color test for ketamine hydrochloride

A new presumptive color test for ketamine hydrochloride is reported. The test is a modification of the cobalt thiocyanate test currently used for cocaine and involves basifying samples rather than acidifying them. The two-step procedure for liquids and three-step procedure for powdered samples are straightforward, definitive, and utilize reagents commonly used in forensic drug analysis. The test works on ketamine hydrochloride in both powder and liquid form and has a sensitivity of c. 1.25 mg. Performing the test with numerous other controlled substances and related chemicals demonstrates the test to be highly selective.     

Clarifying the complex chemistry of cobalt(II) thiocyanate-based tests for cocaine using single-crystal X-ray diffraction and spectroscopic techniques

Cobalt(II) thiocyanate-based tests are routinely used to screen cocaine products, with the formation of a blue species interpreted as a positive response. An array of other organic bases has been identified as false positives – including well-documented cocaine product adulterant lidocaine and its salt. False positives prompt continued test development, though improvements are hindered by unresolved product structures and reaction pathways. Toward greater clarity, cobalt(II) thiocyanate reactions with cocaine hydrochloride, along with lidocaine and its salt, were investigated using multiple analytical techniques. Reactions involving cocaine hydrochloride yielded glassy, amorphous blue material while reactions of lidocaine hydrochloride monohydrate produced larger, needle-like crystals whose structure was determined via single-crystal X-ray diffraction to be an ion pair (Hlidocaine⁺)₂([Co(SCN)₄]²⁻)·H₂O. While the blue precipitate isolated from reactions involving cocaine hydrochloride was unsuitable for crystallographic structure determination, comparative ultraviolet–visible, attenuated total reflectance infrared, and Raman spectroscopic analysis – along with elemental analysis – supports that this solid is comprised of a comparable ion pair (Hcocaine⁺)₂[Co(SCN)₄]²⁻. Pink crystals isolated from lidocaine reaction vessels were identified as coordination compounds cis-[CoL₂(SCN)₂] and trans-[CoL₂(SCN)₂] where L = lidocaine, while pink crystals from both cocaine hydrochloride and lidocaine hydrochloride monohydrate reaction vessels were the coordination polymer trans-[Co(H₂O)₂(SCN)₂]·H₂O. The results presented herein enable reaction optimization to favor a desired product, whether ion pair or coordination species.