Accurate Terpene Analysis

By April 2, 2019 April 7th, 2019 Science
Accurate Terpene Analysis

How to Accurately Quantify Terpenes in Hemp Products

Accurately identifying and quantifying terpenes in hemp has proven to be a uniquely challenging analysis. This is accomplished by: (1) properly identifying the terpene of interest and (2) precise quantitation. Both parameters are mutually inclusive of one another and both are necessary to generate a correct terpene “fingerprint”. Here’s how we control each of these parameters.

Identification

To accurately quantitate hemp terpenes, proper instrumentation is paramount. The most common way is to use Gas Chromatograph with Flame Ionization Detection (GC/FID).

The analysis of simple matrices; e.g. Pharmaceutical products, works well using GC/FID due to the low background interference, but that changes when applied to hemp.

There are hundreds of phytochemicals contained within the hemp plant and this natural matrix presents a chromatographic challenge when using GC/FID.

Flame Ionization detects virtually everything in the sample – not to be confused with identifying everything in the sample.

To solve this issue, GC with tandem Mass Spectrometry (GC/MS) is a great tool for this analysis. GC/MS allows us to filter out the unwanted “noise” from our analysis, thereby accurately identifying terpenes of interest and generating an accurate fingerprint. Testing terpene content with GC/MS allows us to generate three levels of confirmation: (1) chromatographic retention time, (2) molecular parent mass, and (3) daughter/ fragment ion mass. This eliminates the potential for false identification for each terpene analyzed.

Mass Spec (GC/MS) vs. Flame Ionization (GC/FID)

Below is an example of a chromatogram for a hemp product. On the right, we see the chromatogram using Flame Ionization (FID). Notice the amount of “interference” at the base of the diagram. This can cause false positives and call into question the validity of the result. Through the use of Mass Spec, we can filter out this unwanted “noise” and have positive confirmation of the analytes.

Quantitation

Once we’ve selected the correct instrumentation, filtered out the unwanted chromatographic interference through mass selection, and confirmed identification of the terpenes, the real challenge begins – quantifying each terpene. What does that mean and how is that accomplished?

Fundamentals of Quantitation

To properly quantitate an unknown compound, first a linearity curve using a known standard concentrations is generated for that individual compound. Once that linearity curve has been prepared, the compound in the unknown is measured against the standard linearity curve to determine the concentration of the unknown compound.

Linearity Curve
Terpenes Quantitation

Each terpene compound has a unique signal response using GC/MS. Therefore, to properly quantitate terpenes in a sample, 6-point linearity curves are generated for each terpene and spiked into a comparable matrix. Multiply that by each of the 22 terpenes your looking at 132 data points of standards – every day of analysis!

Terpene Linearity Curve
Terpenes Recovery

Aside from the sheer volume of analysis, the 6-point linearity curve described above performs well when prepared as standards, also expressed as “neat” standards. In other words, when the terpene standards are prepared at different concentrations in a solvent such as methanol, a predictive linearity graph is easily accomplished. However, when spiking those same terpenes into a complex matrix such as hemp, drastic changes occur.

Significant differences are observed in both the GC and the MS when analyzing neat standards versus matrices with exceptionally high background noise, such as hemp. Not only is chromatographic interference insurmountable if using FID, but the chemical properties inherent in hemp trigger a complete overhaul of method parameters when transferring from neat standards analysis to hemp analysis.

Summary

Achieving the correct analytical result is not a trivial task. Critical factors include equipment selection, instrument method parameters, and method extraction optimization. Guidance from the FDA-regulated Pharmaceutical Industry’s cGMP framework provides a clear path to make scientifically justified method validation decisions that will stand up to legal scrutiny.

To that end, we’ve accomplished the most comprehensive and robust Terpene method validation in the industry, resulting in the first truly quantitative Terpene analysis. We’ve changed the game on Terpene analysis. For the first time, you have a resource to arrive at the correct Terpene value and have scientific legitimacy to support it.

To learn about more about our Terpene Profile testing service, click here: