O’Shaughnessy’s How Accurate is Potency Testing?

1 O Shaughnessy s Autumn 2011 17 continued on next pageHow Accurate is Potency Testing? RING TEST: A standard procedure in the analytical testing industry for external quality-control assurance, in which identical samples are sent to a variety of testing facilities in order to compare results. Want to know the Potency of your medicine? How much, if any CBD, does it contain? Has it been sprayed with dangerous pesticides? Is it infested by molds or bac-teria? The only way to answer these questions for sure is to have it tested by an analytical lab.

2 Many labs now offer testing services for the medical can-nabis industry. How Accurate are the results they provide? Our investigation was launched in the winter of 2010/11. An identical set of samples was submitted to 10 labs. The labs were asked to measure THC, CBD, and CBN, the three major cannabinoids for which testing is generally available. To encourage participation, the identity of the labs was kept confidential; in this report they are identified by numbers only (Lab 1, 2 etc.).In most cases, lab results were consistent to within 20% of each other.

3 To some degree, the differences in results might be explained by natural variations in the consistency of the cannabis samples used; to some degree, by differ-ences in lab procedures. In certain cases, there were glaring discrepancies suggesting laboratory error. Three of the 10 labs performed poorly on half the tests. Particularly in the case of liquid alcohol extracts, test results were troublingly inconsistent. Nevertheless, the general results showed good agreement between most lab results involving herbal sam-ples. Lab performance can be expected to improve in the future as the industry responds with improved were asked to examine six different samples: four herbal cannabis samples (A - D), and two liquid (ethanol) extracts (F - G).

4 The cannabis samples were taken from herbal material homogenized in a blender to minimize vari-ations in Potency . Samples were stored in a cool, dark room in tightly closed containers until sent to the labs. All testing was blinded: labs did not receive any information about the samples that could have skewed their analytical A, C, and D: replicatesThese samples were exactly identical, and intended to check the reproducibility of participating labs, including their extraction protocol, sample preparation, and analyti-cal methodology.

5 Samples consisted of roughly one-gram packets of a THC-rich cannabis mixture that had been ho-mogenized in a kitchen blender, followed by manual B: high CBDThis sample consisted of one gram of a similarly pre-pared mixture of CBD-rich herbal cannabis. The sample was intended to check for labs capability of identifying and quantifying F and G: extractsSamples F and G were alcohol tinctures of about one milliliter each. Both were prepared from a single CBD-rich herbal mixture. Material in Sample F was decarboxylated by heating in a closed glass jar at 100 C for 90 minutes before soaking in alcohol.

6 Sample G was prepared from the same material, but unheated. Samples were extracted in 99% pure ethanol for 12 minutes and filtered in cheese-cloth, then a coffee filter. These samples were intended to evaluate only the testing methodology of the participat-ing labs, by removing the need for extraction and sample kinds of lab equipment were used to test the samples. Five labs employed gas chromatography (GC), in which the sample is first vaporized under heat. The result-ing gases were subsequently analyzed either by means of a flame ionization detector (GC-FID, used by four labs), or a mass spectrometer (GC-MS, used by one).

7 Four labs used a technology known as high-pressure liq-uid chromatography (HPLC), in which the sample is ana-lyzed by forcing it at high pressure through long columns to separate its components. GC and HPLC are by far the leading technologies for cannabis testing . One lab used a third method, Thin Layer Chromatography (TLC), which is commonly used for qual-itative analysis (fingerprinting/profiling) of cannabis sam-ples. As a tool for quantification ( Potency testing ) it tends to be less Accurate , because the results are scored inexactly by visually judging the size or density of a spot.

8 Fresh herbal cannabis does not contain significant amounts of free THC. Instead, the plant produces its bio-logical precursor, THC-acid (THCA), which lacks THC s activity and is not psychoactive. The same is true for most other cannabinoids in the cannabis plant ( CBD is pres-ent as CBDA). Only after heating are THCA and CBDA converted into their more potent, non-acid forms, THC and CBD. This process is known as decarboxylation. When cannabis is smoked or cooked, the user mainly ingests activated, non-acid cannabinoids.

9 However, if cannabis is consumed raw or in an unheated oil or alco-hol extract, the cannabinoids remain in their natural acid form. The properties of cannabinoid acids have not been well investigated. Although THCA is not psychoactive, it is thought to have some medicinal it is performed at room temperature, HPLC an-alyzes cannabinoids in the chemical form in which they are actually present in the sample. For fresh herbal material, that means lots of THCA and a little free THC (as a result of spontaneous decarboxylation during harvest, process-ing and storage).

10 Consequently, labs using HPLC reported two different entries: THC and THCA. From this it is pos-sible to calculate the effective THC Total by adding the measured THC and THCA. In order to adjust for differ-ent molecular weights, the THCA measurements need to be multiplied by a factor of (one lab failed to do this correctly). The same applies to the measuring of CBD and contrast, when samples are analyzed by GC, the high temperature of the injector causes the cannabinoids in the sample to instantly decarboxylate, converting all THCA into THC before the sample enters the chromatographic column.