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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- )H2 O. 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(H2 O)2 (SCN)2 ]H2 O. The results presented herein enable reaction optimization to favor a desired product, whether ion pair or coordination species.
Cobalt(II) thiocyanate is an inorganic compound with the formula Co(SCN)2.[1] The anhydrous compound is a coordination polymer with a layered structure. The trihydrate, Co(SCN)2(H2O)3, is a isothiocyanate complex used in the cobalt thiocyanate test (or Scott test) for detecting cocaine. The test has been responsible for widespread false positives and false convictions.[2][3]
The hydrate may be prepared by the salt metathesis reactions, such as the reaction of aqueous cobalt(II) sulfate and barium thiocyanate to produce a barium sulfate precipitate, leaving the hydrate of Co(SCN)2 in solution:[4]
Detailed procedures for the cobalt thiocyanate test are available. The reagent consists of 2% cobalt thiocyanate dissolved in dilute acid.[5] Glycerol is often added to stabilise the cobalt complex, ensuring it only goes blue when in contact with an analyte and not due to drying.[6]
Addition of the cobalt thiocyanate reagent to cocaine hydrochloride results in the surface of the particles turning a bright blue (faint blue for cocaine base). The solution changes back to pink upon adding some hydrochloric acid. Addition of chloroform, results in a blue organic layer for both cocaine hydrochloride and cocaine base. Diphenhydramine and lidocaine also give blue organic layers. These compounds are known false positives for cocaine. Lidocaine is commonly used to adulterate or mimic cocaine due to its local anaesthetic effect.
Tens of thousands of people every year are sent to jail based on the results of a $2 roadside drug test. Widespread evidence shows that these tests routinely produce false positives. Why are police departments and prosecutors still using them?
Back in the 1970s, when Scott went to formulate his test for cocaine, chemists had been using a pink liquid called cobalt thiocyanate to help detect the drug for more than four decades. When cocaine combines with the liquid, a blue color forms. But errors plagued the tests, Scott said, because dozens of substances besides cocaine also produce a blue reaction.
Professor in the Department of Traumatolo-Orthopedics at UFRJ, Hand Surgery, Reconstructive Microsurgery, Bone and Connective Tumors, Occupational Physician, Lawyer, Postgraduate in Criminal Law and Criminal Procedural Law, Forensic Expert at PRPTC-Niteri (PCERJ), Brazil
This article is the result of examinations carried out on corpses, which were admitted to one of the Technical-Scientific Police services of the Civil Police of the State of Rio de Janeiro, whose deaths were suspected of being due to exogenous intoxication due to the use of a prohibited substance. (cocaine); aims to present a proposal for research on cocaine, in corpses suspected of death due to exogenous intoxication, carrying out an analysis of the material found in the nasal cavities, when the necropsy examination begins, providing a bias for the Coroner, regarding the visceral findings identified, as well as presenting proposals regarding requests for subsidiary toxicology research exams.
This test has good sensitivity, reacting with well diluted samples, however, it can react with other drugs such as diphenyldramine hydrochloride, chlorpromazine hydrochloride, promazine hydrochloride, scopolamine, dibucaine hydrochloride, promethazine and phencyclidine hydrochloride, powdered milk and yeast.2 Due to the possibility of a false positive result when other substances are analyzed, it is necessary to use spectroscopic techniques such as UV-VIS and/or ATR-FTIR as colorimetric solutions can act as a safe analytical method to eliminate inconclusive results or resolve problems of false positives. Furthermore, the use of the ATR-FTIR technique combined with PLS multivariate calibration is a promising method for quantifying the cocaine hydrochloride content in cocaine samples seized by the Brazilian police. It is always important to emphasize that the examination is only a presumptive examination, serving only to guide the Coroner on possible findings during the autopsy examination.
In our country, we use the modified test, using only Ammonium Thiocyanate and Cobalt Chloride which, in an immediate reaction, give the substance studied a cobalt blue color. In cases of positivity, with a blue color identified, the test is presumptive for the substance cocaine.3 Once the pre-test sample is positive, the rest of the material is separated, properly collected and stored; being sent for toxicology examination, as well as blood and fragments of viscera, providing elements for the certainty of the analyzed substance.
n the case of death due to violent death, there is a legal obligation to carry out a medical-legal examination, and, if the suspicion falls within the scope of poisoning, a toxicological examination is requested.4 Poisonings can be classified as criminal, legal (in the case of the death penalty), accidental (food poisoning, animal bites, accidental absorption of household products, medicines, among others) or voluntary (self-inflicted injuries, drug addiction, therapeutic). Depending on the objective of the case in question and the type of analysis intended, the most appropriate sample is selected and collected, the sample of choice for a given toxicological analysis. The biological samples that are the focus of toxicological analyzes routinely contain fragments of viscera, biological fluids obtained at necropsy. Within the scope of PCERJ, fragments of viscera are routinely collected, preferably the brain, stomach with contents, liver with gallbladder, kidney; Blood samples and, when possible, urine are also collected.
According to the Unodc World Drug Report 2022, around 284 million people between the ages of 15 and 64 used drugs around the world in 2020, an increase of 26% compared to the previous decade. In Brazil, consultations related to the consumption of hallucinogens grew 54% between the months of March and June 2022 when compared to the same period last year, according to data from the Unified Health System (SUS) made available by the Ministry of Health.5 In Brazil, 11,071 deaths were recorded in 2020, an increase of 24.2% compared to 2019, when the country had recorded 8,917 deaths resulting from drug use.6 Given such an alarming situation, it is expected that the number of deaths resulting from the use of drugs, especially cocaine, will increase proportionally. Therefore, these deaths will, without a doubt, be investigated and will end up in a morgue, and will then be studied by a Coroner. It is known that several complications are associated with cocaine abuse, the most frequent being cardiovascular, respiratory, neurological and gastrointestinal effects.
In the cardiovascular aspect, cocaine induces an increase in heart rate and ventricular contractility, causing an increase in blood pressure levels. Simultaneously, epicardial arterial vasoconstriction occurs, decreasing the oxygen supply to this organ. This vasoconstriction is due to the stimulation of adrenergic receptors, the release of endothelin and the decrease in nitric oxide production.7 These changes can lead to cardiac arrhythmias, tachycardia, ventricular fibrillation, myocardial ischemia, cardiomyopathies, acute myocardial infarction and death. From a Legal Medical point of view, the finding of visceral manifestations competing with asphyxial phenomena is a frequent finding in these cases, such as the presence of petechiae, fluid and dark blood, polyvisceral congestion, among others. In view of this finding, to allow a better interpretation of the autopsy findings, in these cases of death without an apparent cause, we began, in the cases already exemplified, to perform the modified Scott test in the autopsy room and, its positive result, allowed us to understand more naturally the possible cause of the etiology of the findings and the death event.
When starting the necropsy examination, with the use of a flashlight, in suspected cases, we investigate the nasal and oral cavities; In the event of identification of a foreign substance, it is collected using SWAB, with more than one always collected to perform the modified Scott test and the second, together with blood and viscera, sent to the sector of toxicology, to carry out an indeterminate toxicology research examination.
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