48 February / March 2016
Using Micro-Elution SPE to Accelerate Sample Preparation for the Determination of Cannabis Use
by Thomas G. Carrell1 1
2 3 , Xiaolei Xie2 , Marta Kozak2 , Mike Oliver3
Thermo Fisher Scientific, West Palm Beach, FL 33407 Thermo Fisher Scientific, San Jose, CA 95134 Thermo Fisher Scientific, Runcorn, Cheshire, UK
Although urine testing has become routine in laboratories tasked with finding evidence for consumption of marijuana or other cannabis containing products, oral fluid is emerging as an attractive alternative due to its non-invasive sampling procedures. However, because drug and metabolite levels are very low in oral fluid, a very sensitive analytical method is required. In this article, we describe a new sample preparation procedure using micro-elution SPE that reduces the time and effort required to generate samples for LC-MS/MS analysis of THCA from both urine and oral fluid. The LC-MS/MS method has a Limit of Quantification (LOQ) for THCA below 1.5 ng/mL in urine and 10 pg/mL in oral fluid.
Introduction
Marijuana is one of the most commonly consumed drugs due to its psychoactive effects, and is therefore frequently found in forensic and toxicology analyses [1]. Although its use has been illegal for some time, marijuana and other forms of cannabis are being accepted around the world including some parts of the United States for medicinal and recreational use. Because of this widespread use, laboratories have a pressing need to rapidly and reliably analyse samples to detect marijuana and cannabis consumption.
THC ((-)-Δ9 -Tetrahydrocannibinol) is
the primary psychoactive component in marijuana and cannabis products. In the body, THC is metabolised to form THC-OH ((±)-11-Hydroxy-Δ9
-
Tetrahydrocannibinol), which is also psychoactive, and THCA ((±)-11-nor-9- Carboxy-Δ9
-Tetrahydrocannibinol), which is not. These metabolites persist for days following consumption, enabling their use as markers for recent cannabis use [2]. Blood can contain all three components, while urine typically contains only THCA. Oral fl uid can contain both THC and THCA. However, it is possible for THC to collect in oral fl uid from passive exposure in environments where marijuana is being smoked, and so THCA detection is therefore required to conclusively identify cannabis consumption from oral fl uid samples.
Chromatographic methods for the detection and quantifi cation of these compounds were originally developed based on GC-MS [3-4],
Figure 1. Workfl ows for the sample preparation of urine and oral fl uid for the analysis of THC and THCA.
however this approach requires extensive sample preparation and derivatisation prior to analysis. More recently, LC-MS/MS has become more widely available and accepted for these analyses, providing simplifi ed workfl ows through the elimination of the derivatisation step [5-6]. LC-MS/MS also allows fl exibility by enabling concurrent analysis for other drugs, extending the range of a single test.
Sample preparation plays a major role in any analysis involving biological fl uids or
tissues since there are many components in these matrices that are either incompatible with the analytical system or produce interferences with the target compounds. For example, blood contains a high concentration of proteins and phospholipids that can foul the analytical column and result in ion suppression during MS detection. Urine contains a high salt concentration that can precipitate throughout the system, especially at the ion source, necessitating frequent maintenance.
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