A simple and fast method to detect freebase cocaine in artificial saliva by square wave voltammetry (SWV) using carbon paste electrode

Bruno Ferreira,Leandro Oka Duarte,Juliana Midori Toia Katayama,Érica Naomi Oiye,Pedro Henrique Barros Oliva,Marcelo Firmino De Oliveira,Maria Fernanda Muzetti Ribeiro

doi:10.5599/jese.849

Bruno Ferreira, Leandro Oka Duarte + Show 5 more

Open Access

https://doi.org/10.5599/jese.849

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Abstract

The consequences of consuming and commercializing illicit drugs including cocaine, constitute a serious problem for authorities and the whole society. Cocaine is usually identified in the laboratory conditions by chromatographic or spectroscopic methods. Electrochemical techniques have also gained prominence because they are fast and easy to use, have many applications, and provide reproducible and reliable results. Therefore, in the present study, a voltammetric method was developed to detect freebase cocaine using carbon paste electrode and methanol as the main cocaine solvent. The developed method was applied to detect cocaine in the artificial saliva by the square wave voltammetry (SWV). The current values increased linearly with the concentration of cocaine, which afforded construction of the analytical curve. The limit of detection (LoD) and the limit of quantifycation (LoQ) were determined as 0.90 µg/mL and 2.41 µg/mL, respectively. For comparison purposes, HPLC-DAD chromatographic method was also applied to detect cocaine. The corresponding analytical curve gave LoD = 0.043 µg/mL and LoQ = 0.130 µg/mL. Although showing better analytical results, HPLC-DAD method could not detect cocaine in saliva samples without previous treatment, what makes the electrochemical method much more attractive for this type of detection.

Highlights

Cocaine is a natural substance that is commonly found in Erythroxylum coca leaves
From the gas chromatogram correlating the chromatographic peak with the mass spectrum (GC/mass spectrometry (MS)) of freebase cocaine in methanol shown in Figure 3, it can be concluded that there are no other organic compounds present in the sample
Identification of freebase cocaine fortified in artificial saliva using square wave voltammetry (SWV)

Summary

Introduction

Cocaine is a natural substance that is commonly found in Erythroxylum coca leaves. This plant is widely cultivated, sold, and distributed in South American countries 1. The routes of administration of cocaine rely on its chemical form. Freebase cocaine for instance, is usually consumed through smoking, while its salt form is consumed by intranasal or injecting administration 1. The cocaine has half-life of approximately one hour 1-3. When consumed, this drug can concentrate in the tissues, increasing its detection window. There are various literature studies involving cocaine detection in biological samples such as urine, plasma, and saliva 3

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