Scott test associated with multivariate image analysis: A more selective alternative for cocaine research in forensic laboratories

Souza, Diego Mendes de; Messias, Pedro Judah de Moura; Santos, Isabella da Silva; Ramalho, Eduardo Dias; Júnior, Ettore Ferrari; Morais, Pedro Augusto de Oliveira

doi:10.1016/j.forsciint.2022.111277

Cited by 7 publications

(10 citation statements)

References 41 publications

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“…Though the structures of lidocaine and cocaine are markedly different (Figure 1), they share a common feature of nonbonding electrons pairs available for Lewis acid‐base interactions with Co(II) via tertiary amine and carbonyl groups [3, 19]. As discussed by de Jong et al., [19] these shared features may explain similar appearing blue species interpreted as positive cobalt(II) thiocyanate bases test results for an array of organic bases.…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, the ratio of Scott's test reagent #1 to #2 was carefully monitored as excessive addition of HCl can result in the formation of a blue species that is likely tetrachlorocobaltate (II), CoCl 4 2− , which is soluble in polar solvents [33, 42–46]. Analyte and reagent amounts were scaled in tandem for larger experimental yields as done in reference [3]. Samples of cocaine hydrochloride, lidocaine hydrochloride monohydrate, and lidocaine were subjected to both classic and Scott's test.…”

Section: Methodsmentioning

confidence: 99%

“…, which is soluble in polar solvents [33,[42][43][44][45][46]. Analyte and reagent amounts were scaled in tandem for larger experimental yields as done in reference [3]. Samples of cocaine hydrochloride, lidocaine hydrochloride monohydrate, and lidocaine were subjected to both classic and Scott's test.…”

Section: Cobalt (Ii) Thiocyanate Testingmentioning

confidence: 99%

“…The litany of false positives for cobalt(II) thiocyanate-based tests has prompted numerous revisions in pursuit of increased selectivity, while retaining ease-of-use and screening speed. Updates to cobalt(II) thiocyanate tests range from the chemical (e.g., Scott's test) to the computational (e.g., incorporating multivariate image analysis) [3,5]. Stymying continued test improvement efforts are unsettled product structures and cobalt(II) thiocyanate reaction mechanisms [1,3,20].…”

Section: Introductionmentioning

confidence: 99%

“…Structures of cocaine and lidocaine are shown in Figure 1. Lidocaine is showcased herein as this local anesthetic is both a long-noted false-positive and oft-encountered adulterant in cocaine products [3,18,19]. The litany of false positives for cobalt(II) thiocyanate-based tests has prompted numerous revisions in pursuit of increased selectivity, while retaining ease-of-use and screening speed.…”

Section: Introductionmentioning

confidence: 99%

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

Burks,

Öhrström,

Amombo Noa

2023

Journal of Forensic Sciences

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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−)·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.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Cobalt (Ii) Thiocyanate Testingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Burks,

Öhrström,

Amombo Noa

2023

Journal of Forensic Sciences

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Multiphase electroextraction of malachite green from surface water and its determination using digital imaging and chemometric tools

Viana,

Kubáň,

Botelho

et al. 2024

Electrophoresis

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This study introduces a novel method for the quantification of malachite green (MG), a pervasive cationic dye, in surface water by synergizing multiphase electroextraction (MPEE) with digital image analysis (DIA) and partial least square discriminant analysis. Aimed at addressing the limitations of conventional DIA methods in terms of quantitation limits and selectivity, this study achieves a significant breakthrough in the preconcentration of MG using magnesium silicate as a novel sorbent. Demonstrating exceptional processing efficiency, the method allows for the analysis of 10 samples within 20 min, exhibiting remarkable sensitivity and specificity (over 0.95 and 0.90, respectively) across 156 samples in both training and test sets. Notably, the method detects MG at low concentrations (0.2 µg L−1) in complex matrices, highlighting its potential for broader application in environmental monitoring. This approach not only underscores the method's cost‐effectiveness and simplicity but also its precision, making it a valuable tool for the preliminary testing of MG in surface waters. This study underscores the synergy among MPEE, DIA, and chemometric tools, presenting a cost‐efficient and reliable alternative for the sensitive detection of water contaminants.

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Plastic antioxidants: A family of cocaine cutting agents analyzed by short column gas chromatography-mass spectrometry

Arantes

Silva

Caldas

2022

Journal of Chromatography A

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Scott test associated with multivariate image analysis: A more selective alternative for cocaine research in forensic laboratories

Cited by 7 publications

References 41 publications

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

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

Multiphase electroextraction of malachite green from surface water and its determination using digital imaging and chemometric tools

Plastic antioxidants: A family of cocaine cutting agents analyzed by short column gas chromatography-mass spectrometry

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