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Absorptive stripping voltammetry for cannabis detection.

Nissim R, Compton RG - Chem Cent J (2015)

Bottom Line: THC concentrations as low as 0.50 μM are detected in synthetic saliva solutions.The sensitivity of the sensor was 0.12 μA μM(-1), 0.84 μA μM(-1) and 0.067 μA μM(-1) for the stationary buffer, the stirred buffer and the saliva matrix, respectively. "Absorptive Stripping Voltammetry" can be reliably applied to the detection of Δ(9)-tetrahydrocannabinol, after suitable optimisation of the assay.Usefully low practical limits of detection can be achieved.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ UK.

ABSTRACT

Background: Given that Δ(9)-tetrahydrocannabinol, the active constituent of cannabis, has been shown to greatly reduce driving ability, thus being linked to many drug driving accidents, its reliable detection is of great importance.

Results: An optimised carbon paste electrode, fabricated from graphite powder and mineral oil, is utilised for the sensitive detection of Δ(9)-tetrahydrocannabinol (THC) in both aqueous solutions of pH 10.0 and in synthetic saliva solutions. "Absorptive Stripping Voltammetry" is exploited to that effect and the paste is used to pre-concentrate the carbon paste electrode with the target molecule. Practical limits of detection of 0.50 μM and 0.10 μM are determined for THC in stationary and stirred aqueous borate buffer solutions, respectively. Theoretical limits of detection are also calculated; values of 0.48 nM and 0.41 nM are determined for stationary and stirred THC aqueous borate buffer solutions, respectively. THC concentrations as low as 0.50 μM are detected in synthetic saliva solutions. The sensitivity of the sensor was 0.12 μA μM(-1), 0.84 μA μM(-1) and 0.067 μA μM(-1) for the stationary buffer, the stirred buffer and the saliva matrix, respectively.

Conclusions: "Absorptive Stripping Voltammetry" can be reliably applied to the detection of Δ(9)-tetrahydrocannabinol, after suitable optimisation of the assay. Usefully low practical limits of detection can be achieved.

No MeSH data available.


Related in: MedlinePlus

a Square wave voltammograms (frequency: 100 Hz, amplitude: 40 mV, step potential: 1 mV) for the oxidation of THC, seen at +0.37 V (vs. SCE), on the graphite/dioctyl phthalate paste electrode (black line) and the graphite/mineral oil paste electrode (red line). The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 80 μM THC, for 3 min. b Comparison of the peak currents obtained with the two carbon paste electrodes (black squares: graphite/dioctyl phthalate paste, red circles: graphite/mineral oil paste). The measurements were obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 7.0 – 80 μM THC, for 3 min. The errors relate to separate electrode preparations
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Fig1: a Square wave voltammograms (frequency: 100 Hz, amplitude: 40 mV, step potential: 1 mV) for the oxidation of THC, seen at +0.37 V (vs. SCE), on the graphite/dioctyl phthalate paste electrode (black line) and the graphite/mineral oil paste electrode (red line). The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 80 μM THC, for 3 min. b Comparison of the peak currents obtained with the two carbon paste electrodes (black squares: graphite/dioctyl phthalate paste, red circles: graphite/mineral oil paste). The measurements were obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 7.0 – 80 μM THC, for 3 min. The errors relate to separate electrode preparations

Mentions: Each carbon paste electrode was immersed for 3 min, under open circuit conditions, in a deoxygenated aqueous borate buffer solution of pH 10.0 that contained 7.0 – 80 μM THC and 0.1 M KCl as the supporting electrolyte. Each paste electrode was then transferred to a deoxygenated aqueous borate buffer solution of pH 10.0, which only contained 0.1 M KCl. Oxidative square wave voltammetric scans were then run, between +0.25 V and + 0.52 V (vs. SCE) for the graphite/dioctyl phthalate paste electrode and between +0.20 V and +0.60 V (vs. SCE) in the case of the graphite/mineral oil paste electrode. The frequency and step potential used were 100 Hz and 1 mV, respectively, while the amplitude was set to 40 mV. Peaks due to the oxidation of THC, as shown in Scheme 1 [17, 25, 26], were seen at peak potentials of +0.39 V and +0.37 V (vs. SCE) on the graphite/dioctyl phthalate and the graphite/mineral oil pastes respectively; typical responses are depicted in Fig. 1. Scheme 1 assumes that THC behaves like a typical phenol [17]; to the best of the author’s knowledge there is no literature reporting detection of further THC oxidation products.Scheme 1


Absorptive stripping voltammetry for cannabis detection.

Nissim R, Compton RG - Chem Cent J (2015)

a Square wave voltammograms (frequency: 100 Hz, amplitude: 40 mV, step potential: 1 mV) for the oxidation of THC, seen at +0.37 V (vs. SCE), on the graphite/dioctyl phthalate paste electrode (black line) and the graphite/mineral oil paste electrode (red line). The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 80 μM THC, for 3 min. b Comparison of the peak currents obtained with the two carbon paste electrodes (black squares: graphite/dioctyl phthalate paste, red circles: graphite/mineral oil paste). The measurements were obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 7.0 – 80 μM THC, for 3 min. The errors relate to separate electrode preparations
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493815&req=5

Fig1: a Square wave voltammograms (frequency: 100 Hz, amplitude: 40 mV, step potential: 1 mV) for the oxidation of THC, seen at +0.37 V (vs. SCE), on the graphite/dioctyl phthalate paste electrode (black line) and the graphite/mineral oil paste electrode (red line). The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 80 μM THC, for 3 min. b Comparison of the peak currents obtained with the two carbon paste electrodes (black squares: graphite/dioctyl phthalate paste, red circles: graphite/mineral oil paste). The measurements were obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 7.0 – 80 μM THC, for 3 min. The errors relate to separate electrode preparations
Mentions: Each carbon paste electrode was immersed for 3 min, under open circuit conditions, in a deoxygenated aqueous borate buffer solution of pH 10.0 that contained 7.0 – 80 μM THC and 0.1 M KCl as the supporting electrolyte. Each paste electrode was then transferred to a deoxygenated aqueous borate buffer solution of pH 10.0, which only contained 0.1 M KCl. Oxidative square wave voltammetric scans were then run, between +0.25 V and + 0.52 V (vs. SCE) for the graphite/dioctyl phthalate paste electrode and between +0.20 V and +0.60 V (vs. SCE) in the case of the graphite/mineral oil paste electrode. The frequency and step potential used were 100 Hz and 1 mV, respectively, while the amplitude was set to 40 mV. Peaks due to the oxidation of THC, as shown in Scheme 1 [17, 25, 26], were seen at peak potentials of +0.39 V and +0.37 V (vs. SCE) on the graphite/dioctyl phthalate and the graphite/mineral oil pastes respectively; typical responses are depicted in Fig. 1. Scheme 1 assumes that THC behaves like a typical phenol [17]; to the best of the author’s knowledge there is no literature reporting detection of further THC oxidation products.Scheme 1

Bottom Line: THC concentrations as low as 0.50 μM are detected in synthetic saliva solutions.The sensitivity of the sensor was 0.12 μA μM(-1), 0.84 μA μM(-1) and 0.067 μA μM(-1) for the stationary buffer, the stirred buffer and the saliva matrix, respectively. "Absorptive Stripping Voltammetry" can be reliably applied to the detection of Δ(9)-tetrahydrocannabinol, after suitable optimisation of the assay.Usefully low practical limits of detection can be achieved.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ UK.

ABSTRACT

Background: Given that Δ(9)-tetrahydrocannabinol, the active constituent of cannabis, has been shown to greatly reduce driving ability, thus being linked to many drug driving accidents, its reliable detection is of great importance.

Results: An optimised carbon paste electrode, fabricated from graphite powder and mineral oil, is utilised for the sensitive detection of Δ(9)-tetrahydrocannabinol (THC) in both aqueous solutions of pH 10.0 and in synthetic saliva solutions. "Absorptive Stripping Voltammetry" is exploited to that effect and the paste is used to pre-concentrate the carbon paste electrode with the target molecule. Practical limits of detection of 0.50 μM and 0.10 μM are determined for THC in stationary and stirred aqueous borate buffer solutions, respectively. Theoretical limits of detection are also calculated; values of 0.48 nM and 0.41 nM are determined for stationary and stirred THC aqueous borate buffer solutions, respectively. THC concentrations as low as 0.50 μM are detected in synthetic saliva solutions. The sensitivity of the sensor was 0.12 μA μM(-1), 0.84 μA μM(-1) and 0.067 μA μM(-1) for the stationary buffer, the stirred buffer and the saliva matrix, respectively.

Conclusions: "Absorptive Stripping Voltammetry" can be reliably applied to the detection of Δ(9)-tetrahydrocannabinol, after suitable optimisation of the assay. Usefully low practical limits of detection can be achieved.

No MeSH data available.


Related in: MedlinePlus