Pesticide Analysis in Cannabis and Hemp by Gas Chromatography

Introduction

Pesticide testing plays a vital role in ensuring the safety and integrity of cannabis and hemp products. As cultivation and production become legal in more regions, regulations around pesticide use are still catching up. Without consistent oversight, there’s a risk that harmful or banned compounds may be used during growth or processing and remain in the final product.

Testing for pesticide residues protects both producers and consumers. It confirms product safety, supports regulatory compliance, and helps build trust in legitimate, responsibly made cannabis products.

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The Challenge

Different regulations make consistent testing difficult

Regulations around pesticide use in cannabis vary widely, not only between countries but often from state to state. Some regions list hundreds of compounds that must be tested for, while others provide only general guidance or no formal limits at all.

This inconsistency makes it hard for producers and laboratories to apply a single, standardised testing method. A product that meets requirements in one market may fail in another. The only reliable approach is to screen for a broad range of pesticide residues with a method sensitive enough to detect multiple compound types at once.

Many pesticides used in cultivation and storage can remain in the plant and carry through to oils, edibles, and inhaled products. Without proper screening, there’s a risk that consumers could be exposed to harmful residues.

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The Solution

Using gas chromatography to detect pesticide residues in cannabis

Gas chromatography (GC) provides a reliable and efficient way to detect pesticide residues in cannabis and hemp. Using a Flame Ionisation Detector (FID), the Ellutia 200 Series GC can separate and quantify a wide range of pesticide compounds quickly and with excellent repeatability.

A liquid injection technique is used for this analysis. It captures both volatile and semi-volatile compounds effectively, making it ideal for pesticide screening. When paired with a liquid autosampler such as the EL3000A, multiple samples can be analysed automatically with consistent precision.

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This setup delivers the sensitivity needed for pesticide detection while maintaining the low running cost, simplicity, and throughput required for production or regulatory environments.

If you’d like an overview of how GC fits into cannabis testing workflows, take a look at the Cannabis Testing Buyers Guide.

Method Overview

How pesticide testing is performed using gas chromatography

Once the GC system is configured, the process of analysing pesticides is simple. A liquid sample of cannabis extract or concentrate is prepared and injected into the system. A pesticide standard mix is run first to confirm separation and detector response for each compound of interest. The GC then measures pesticide levels in the sample against those standards.

Because many pesticides are large, non-volatile molecules, liquid injection is preferred over headspace sampling. It ensures all components are represented in the sample and allows both volatile and semi-volatile compounds to be detected in a single run. Using hydrogen as the carrier gas and an EL-5 column provides strong separation and stable baselines across multiple compounds with very different properties.

For production or regulatory testing, an autosampler such as the EL3000A can automate injections, improving consistency between runs and allowing multiple samples to be processed unattended.

Typical GC Conditions

Injector temperature: 250 °C
Detector: FID
Detector temperature: 300 °C
Carrier gas: Hydrogen
Simulated constant flow: 3.5ml/min
Split flow: 70 ml/min
Column: EL-5 30 m × 0.25 mm × 0.25 µm

LC vs GC for Acidic and Neutral Cannabinoid Testing

Learn how gas chromatography can measure both acidic and neutral cannabinoids using a simple derivatisation step. This video explains the key differences between LC and GC approaches, how GC achieves total cannabinoid measurement, and what makes it a practical option for in-house testing.

Results and Reliability

What the analysis shows

The GC-FID method achieves clear separation and reliable detection of multiple pesticide compounds in a single analysis. Standard mixes show strong, stable peaks with low noise and no carry-over.

The results confirm that GC provides dependable screening data suitable for routine safety testing. When combined with Ellutia’s autosamplers and software, it forms an efficient and compact platform for pesticide analysis in cannabis and hemp laboratories.

Curious how this could work in your own lab?

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Get the full method and results

If you’d like to see the full details behind this testing method, you can download the complete application note. It includes chromatograms, calibration data, and the exact conditions used for the analysis. It’s a handy reference if you want to check your own setup or compare results.

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