The Scientist - 03.2020

03.2020 | THE SCIENTIST 53

derived products falls to states, creating
a patchwork of different testing require-
ments across the country. In addition,
state governments issue little to no guid-
ance about protocols for testing products
for either potency or safety. Instead, labs
have had to trailblaze the development of
their own methods.
Now, in a cannabis testing industry
that is only a few years old, it’s evident that
reports on potency can vary from lab to
lab, and recalls of contaminated products
happen across the country, threatening
consumer trust. “It’s not really at all like
any other industry I’ve worked in, in that
they’re still trying to work out proficiency
and certification standards,” notes Frank
Conrad, an analytical chemist formerly in
the biofuels industry who now runs Colo-
rado Green Lab, a consultancy firm for the
cannabis industry.

The strength of pot

Knowing the concentration of active

ingredients is crucial throughout the can-

nabis supply chain. Cultivators and retail-

ers want to know a product’s strength

because higher concentrations of CBD or

THC (the more psychoactive compound

of the two) usually mean higher prices.

Potency information is also important for

doctors who prescribe cannabis to their

patients and for recreational users who

wish to control the intensity of their high.

Labs are tasked with testing samples at

every stage of production—from the

whole plant to the manufactured prod-

uct, and often its final packaged form.

In the absence of federal guidance,

labs have had to develop and validate

their own methods of measuring the

concentrations of THC and CBD, and

distinguishing between them—a partic-

ular challenge due to the molecular sim-

ilarity of these two compounds to each

other and to other cannabis compounds.

Many labs have converged on a few ana-

lytical techniques, although the precise

details of each company’s procedure are

often proprietary. Hudalla, who runs the

Massachusetts-based cannabis testing

lab ProVerde Laboratories, says he reck-

ons that most use high-performance liq-

uid chromatography (HPLC) to measure

concentrations of THC and CBD, plus

their acidic precursors, tetrahydrocan-

nabinolic acid and cannabidiolic acid,

which degrade to THC and CBD upon

being heated through smoking or prepa-

ration for oil and edible products.

After the dried plant has been ground

up and doused in a solvent to extract can-

nabinoids, the residual fluid is fed into a

HPLC system which separates different

compounds by using pressure to force

the mixture through a granular material.

The technique is based on the principle

that molecules with different structures

take different amounts of time to pass

through this material. If done correctly,

the method allows chemists to separate

THC or CBD from terpenes, flavonoids,

and other cannabinoids and to detect

each compound’s concentration.

However, there are many accounts of

labs producing starkly different potency

measurements for the same products—

some results varying by as much as 40 per-

cent, according to a 2018 report by Mar-

ijuana Business Daily. Retailer Jerred

Kiloh, who owns a marijuana dispensary

in Los Angeles, has himself received very

different estimates from different labs

testing the same products. “That’s what

we deal with constantly,” he says.

Many experts blame this variability

on the lack of standardized methods for

determining marijuana potency. Lab pro-

tocols can differ in the specific solvents

or reagents used during extraction and

analysis. Then there are the instruments

themselves, which may come from dif-

ferent manufacturers and have different

calibration standards, potentially contrib-

uting additional variation.

Complicating matters further is the

variety of cannabis products on the mar-

ket, some of which are easier to analyze

than others. From CBD-containing tinc-

tures, lotions, and dog treats to THC-

infused chocolate bars and turkey pot

pie, each product needs to undergo a

custom cannabinoid extraction method

before its ingredients can be tested. Data

from California’s Bureau of Cannabis

Control suggest that the more complex

the product, the more likely it is to be

inaccurately labeled. In 2018, regula-

tors found that 10.6 percent of cannabis

flower samples, 20.4 percent of inhal-

able oils and waxes, and 32.9 percent

of edibles, tinctures, and lotions carried

labels with potency estimates that were

more than 10 percent different from the

true value.

Antonio Frazier, vice president of

operations at California-based testing

company CannaSafe, worries that these

inaccuracies—and the recalls that often

follow—make consumers wary of the

industry. “People have a hard time trust-

ing us,” he says.

A safety issue

The stakes are higher for contaminant

testing than for potency testing, as weed

contaminated during cultivation, pro-

cessing, or packaging could be dangerous,

especially for frail or immunocompro-

mised patients. For growers, this sort of

safety testing can be “make or break,” says

Frazier. A finding of contamination could

force them to discard entire batches worth

hundreds of thousands of dollars or more.

Luckily for testing companies and

consumers alike, safety testing is in prin-

ciple more straightforward than potency

evaluation because labs can turn to meth-

ods prescribed by federal agencies for

testing other botanical products. Labs

often isolate pesticides using liquid chro-

matography and then assess their concen-

trations using mass spectrometry, a tech-

nique suited to detecting the often tiny

traces of contaminants. Techniques such

as PCR and DNA sequencing are used to

look for biological contaminants such as

fungi and bacteria.

A more significant obstacle in cannabis

safety testing is uncertainty about what con-

Why would marijuana, espe-

cially as it’s being considered

medical—why would that not

be tested?

—Christopher Hudalla, ProVerde Laboratories