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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 ca. +0.37 V (vs. SCE), on the graphite/mineral oil paste electrode. The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stirred solutions that contained 0.10 – 16 μM THC, for 5 min. b The increase of the peak current with increasing THC concentration (black squares) with the correlation line through the linear range (red line, R2 = 0.96). The lower practical limit of detection was determined as being 0.10 μM, while the slope of the calibration curve gave a value of 0.84 μA μM−1 for the sensitivity of the sensor. The errors relate to separate electrode preparations
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Fig3: a Square wave voltammograms (frequency: 100 Hz, amplitude: 40 mV, step potential: 1 mV) for the oxidation of THC, seen at ca. +0.37 V (vs. SCE), on the graphite/mineral oil paste electrode. The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stirred solutions that contained 0.10 – 16 μM THC, for 5 min. b The increase of the peak current with increasing THC concentration (black squares) with the correlation line through the linear range (red line, R2 = 0.96). The lower practical limit of detection was determined as being 0.10 μM, while the slope of the calibration curve gave a value of 0.84 μA μM−1 for the sensitivity of the sensor. The errors relate to separate electrode preparations

Mentions: The results obtained from the stationary THC solution are presented in Fig. 2a, where peaks corresponding to the oxidation of THC, as in Scheme 1, can be observed at a peak potential of ca. +0.35 V (vs. SCE). As can be seen in Fig. 2b, the peak current shows a linear increase with increasing THC concentration up to THC concentrations of 5.0 μM; the peak height then levels off and a plateau is reached when the THC concentration is further increased. Similarly, the results obtained from the stirred THC solution can be seen in Fig. 3a, where the THC oxidation peak is seen at a peak potential of +0.37 V (vs. SCE). As previously, the peak current increases as the concentration of THC is increased, this time reaching a plateau at 4.0 μM (Fig. 3b). The errors in the calibration curves relate to separate electrode preparations.Fig. 2


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 ca. +0.37 V (vs. SCE), on the graphite/mineral oil paste electrode. The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stirred solutions that contained 0.10 – 16 μM THC, for 5 min. b The increase of the peak current with increasing THC concentration (black squares) with the correlation line through the linear range (red line, R2 = 0.96). The lower practical limit of detection was determined as being 0.10 μM, while the slope of the calibration curve gave a value of 0.84 μA μM−1 for the sensitivity of the sensor. 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

Fig3: a Square wave voltammograms (frequency: 100 Hz, amplitude: 40 mV, step potential: 1 mV) for the oxidation of THC, seen at ca. +0.37 V (vs. SCE), on the graphite/mineral oil paste electrode. The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stirred solutions that contained 0.10 – 16 μM THC, for 5 min. b The increase of the peak current with increasing THC concentration (black squares) with the correlation line through the linear range (red line, R2 = 0.96). The lower practical limit of detection was determined as being 0.10 μM, while the slope of the calibration curve gave a value of 0.84 μA μM−1 for the sensitivity of the sensor. The errors relate to separate electrode preparations
Mentions: The results obtained from the stationary THC solution are presented in Fig. 2a, where peaks corresponding to the oxidation of THC, as in Scheme 1, can be observed at a peak potential of ca. +0.35 V (vs. SCE). As can be seen in Fig. 2b, the peak current shows a linear increase with increasing THC concentration up to THC concentrations of 5.0 μM; the peak height then levels off and a plateau is reached when the THC concentration is further increased. Similarly, the results obtained from the stirred THC solution can be seen in Fig. 3a, where the THC oxidation peak is seen at a peak potential of +0.37 V (vs. SCE). As previously, the peak current increases as the concentration of THC is increased, this time reaching a plateau at 4.0 μM (Fig. 3b). The errors in the calibration curves relate to separate electrode preparations.Fig. 2

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