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Levamisole : a common adulterant in cocaine street samples hindering electrochemical detection of cocaine

(2018) ANALYTICAL CHEMISTRY. 90(8). p.5290-5297
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Abstract
The present work investigates the electrochemical determination of cocaine in the presence of levamisole, one of the most common adulterants found in cocaine street samples. Levamisole misleads cocaine color tests, giving a blue color (positive test) even in the absence of cocaine. Moreover, the electrochemical detection of cocaine is also affected by the presence of levamisole, with a suppression of the oxidation signal of cocaine. When levamisole is present in the sample in ratios higher than 1:1, the cocaine signal is no longer detected, thus leading to false negative results. Mass spectrometry and nuclear magnetic resonance were used to investigate if the signal suppression is due to the formation of a complex between cocaine and levamisole in bulk solution. Strategies to eliminate this suppressing effect are further suggested in this manuscript. In a first approach, the increase of the pH of the sample solution from pH 7 to pH 12 allowed the voltammetric determination of cocaine in the presence of levamisole in a concentration range from 10 to 5000 mu M at nonmodified graphite disposable electrodes with a detection limit of 5 mu M. In a second approach, the graphite electrode was cathodically pretreated, resulting in the presence of oxidation peaks of both cocaine and levamisole, with a detection limit for cocaine of 3 mu M over the linear range of concentrations from 10 to 2500 mu M. Both these strategies have been successfully applied for the simultaneous detection of cocaine and levamisole in three street samples on unmodified graphite disposable electrodes.
Keywords
GLASSY-CARBON ELECTRODES, VOLTAMMETRIC DETERMINATION, LIQUID-CHROMATOGRAPHY, CONFISCATED SAMPLES, QUANTIFICATION, PRETREATMENT, BIOSENSORS, GRAPHITE, PLATINUM, SENSOR

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Citation

Please use this url to cite or link to this publication:

Chicago
de Jong, Mats, Anca Florea, Anne-Mare de Vries, Alexander LN van Nuijs, Adrian Covaci, Filip Van Durme, José Martins, Nele Samyn, and Karolien De Wael. 2018. “Levamisole : a Common Adulterant in Cocaine Street Samples Hindering Electrochemical Detection of Cocaine.” Analytical Chemistry 90 (8): 5290–5297.
APA
de Jong, Mats, Florea, A., de Vries, A.-M., van Nuijs, A. L., Covaci, A., Van Durme, F., Martins, J., et al. (2018). Levamisole : a common adulterant in cocaine street samples hindering electrochemical detection of cocaine. ANALYTICAL CHEMISTRY, 90(8), 5290–5297.
Vancouver
1.
de Jong M, Florea A, de Vries A-M, van Nuijs AL, Covaci A, Van Durme F, et al. Levamisole : a common adulterant in cocaine street samples hindering electrochemical detection of cocaine. ANALYTICAL CHEMISTRY. 2018;90(8):5290–7.
MLA
de Jong, Mats et al. “Levamisole : a Common Adulterant in Cocaine Street Samples Hindering Electrochemical Detection of Cocaine.” ANALYTICAL CHEMISTRY 90.8 (2018): 5290–5297. Print.
@article{8555551,
  abstract     = {The present work investigates the electrochemical determination of cocaine in the presence of levamisole, one of the most common adulterants found in cocaine street samples. Levamisole misleads cocaine color tests, giving a blue color (positive test) even in the absence of cocaine. Moreover, the electrochemical detection of cocaine is also affected by the presence of levamisole, with a suppression of the oxidation signal of cocaine. When levamisole is present in the sample in ratios higher than 1:1, the cocaine signal is no longer detected, thus leading to false negative results. Mass spectrometry and nuclear magnetic resonance were used to investigate if the signal suppression is due to the formation of a complex between cocaine and levamisole in bulk solution. Strategies to eliminate this suppressing effect are further suggested in this manuscript. In a first approach, the increase of the pH of the sample solution from pH 7 to pH 12 allowed the voltammetric determination of cocaine in the presence of levamisole in a concentration range from 10 to 5000 mu M at nonmodified graphite disposable electrodes with a detection limit of 5 mu M. In a second approach, the graphite electrode was cathodically pretreated, resulting in the presence of oxidation peaks of both cocaine and levamisole, with a detection limit for cocaine of 3 mu M over the linear range of concentrations from 10 to 2500 mu M. Both these strategies have been successfully applied for the simultaneous detection of cocaine and levamisole in three street samples on unmodified graphite disposable electrodes.},
  author       = {de Jong, Mats and Florea, Anca and de Vries, Anne-Mare and van Nuijs, Alexander LN and Covaci, Adrian and Van Durme, Filip and Martins, José and Samyn, Nele and De Wael, Karolien},
  issn         = {0003-2700},
  journal      = {ANALYTICAL CHEMISTRY},
  keywords     = {GLASSY-CARBON ELECTRODES,VOLTAMMETRIC DETERMINATION,LIQUID-CHROMATOGRAPHY,CONFISCATED SAMPLES,QUANTIFICATION,PRETREATMENT,BIOSENSORS,GRAPHITE,PLATINUM,SENSOR},
  language     = {eng},
  number       = {8},
  pages        = {5290--5297},
  title        = {Levamisole : a common adulterant in cocaine street samples hindering electrochemical detection of cocaine},
  url          = {http://dx.doi.org/10.1021/acs.analchem.8b00204},
  volume       = {90},
  year         = {2018},
}

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