How do you read a Certificate of Analysis (COA)?

TL;DR

• Lab accreditation (ISO/IEC 17025) and test method must be stated.
• Batch number and sampling date uniquely link the COA to the product.
• Total THC = THCA × 0.877 + Δ9-THC — don't accept Δ9-THC alone.
• Missing panels (pesticides, heavy metals, microbiology) are a red flag.

Header data: lab, batch, date

A credible COA names the testing lab with its accreditation number (in Switzerland usually ISO/IEC 17025 via the Swiss Accreditation Service SAS or a foreign equivalent), the sampling date, and a batch number that matches the packaging. Without a link to the actual batch, the document is at best a generic template — not proof for the product in your hand.

Total THC, decarboxylation and LOD/LOQ

Raw cannabis flower contains mostly THCA, the acidic precursor of THC. Only heating (smoking, vaporising, baking) decarboxylates THCA into psychoactive Δ9-THC, using a conversion factor of 0.877 (mass loss from CO₂ release). A credible COA therefore reports 'total THC' as THCA × 0.877 + Δ9-THC. LOD (limit of detection) and LOQ (limit of quantification) should also be stated — values below LOQ are listed as 'ND' or '<LOQ', not an exact zero.

Which panels are often missing?

Many cheap COAs show only cannabinoids, the least expensive test. Pesticide, heavy-metal and microbiology panels are more critical — pricier but more health-relevant. Switzerland has no uniform legal requirement for CBD products to disclose every panel; cantonal chemists run spot checks. A complete COA should cover at least cannabinoids, pesticides, heavy metals and microbial counts.

The Swiss one percent limit in the test report

In Switzerland, there is a clear legal limit: cannabis products are only marketable and do not fall under the Narcotics Act if the total THC content is below one percent. For consumers and retailers, looking at the COA is therefore the most important safeguard against criminal consequences. A reputable Swiss laboratory explicitly states this total value by calculating the acidic precursor THCA using the conversion factor and adding it to the active THC. If this value is even minimally above the tolerance limit, the product is legally considered an illegal narcotic.

The cantonal enforcement authorities and customs controls base their random checks exactly on these laboratory values. Since the cantons handle enforcement differently, only a seamless and batch-specific certificate of analysis provides reliable protection against complaints or seizures. Caution is particularly advised with imported products from other European countries, as lower limits often apply there and the analysis reports do not always correctly reflect the Swiss requirements for calculating the total THC content.

• Legal limit: The total THC content must strictly be below one percent to be considered legal.
• Basis of calculation: Swiss laboratories must correctly apply the legally defined formula for the total THC value.
• Legal certainty: A valid COA protects retailers and consumers from unintentional violations of the Narcotics Act.
• Cantonal differences: Enforcement can vary, which is why seamless proof for every batch is essential.

Comparison of analytical methods: HPLC versus GC

When reading a COA, your eye quickly falls on the analytical method used, usually abbreviated as HPLC or GC. High-performance liquid chromatography (HPLC) is today considered the gold standard for determining cannabinoids in the flower. The decisive advantage of this method is that the sample is analyzed at room temperature. As a result, the thermally unstable cannabinoid acids such as THCA and CBDA are preserved in their original form and can be measured separately, enabling a precise calculation of the actual total content.

In contrast, gas chromatography (GC) operates with high temperatures in the injector. Due to this exposure to heat, complete decarboxylation of the acids already takes place during the measurement. This means that a distinction between free THC and the acid form THCA in the raw state is no longer directly possible. For correct declaration under Swiss law, which requires a differentiated approach, the HPLC method is therefore the significantly more reliable and transparent choice on the analysis report.

• HPLC method: Enables gentle measurement at room temperature without artificial heat exposure.
• Precise separation: Acids (THCA) and neutral cannabinoids (THC) are recorded and reported separately.
• GC limitation: High temperatures lead to automatic decarboxylation during the measurement process.
• Method declaration: A transparent COA always states the method used directly next to the measurement results.

Terpene profiles and their interpretation

An often underestimated part of modern certificates of analysis is the terpene profile. Terpenes are volatile organic compounds responsible for the characteristic aroma and taste of the cannabis flower. Beyond sensory properties, scientific data indicate that terpenes can influence the effects of cannabinoids. A detailed COA lists the concentrations of the dominant terpenes such as myrcene, limonene, or beta-caryophyllene individually, usually expressed in milligrams per gram or as percentages.

The presence and distribution of these compounds allow conclusions to be drawn about the quality of drying and storage. Since terpenes are highly heat-sensitive and volatile, a low terpene value indicates improper processing or excessive storage. For consumers who value a specific spectrum of effects or a pure flavor profile, the terpene panel is therefore an indispensable indicator of the freshness and artisanal quality of the product.

• Aromatic diversity: Terpenes determine the aroma and contribute significantly to the characterization of the strain.
• Quality indicator: High terpene levels indicate gentle drying and optimal storage conditions.
• Synergistic effect: The combination of cannabinoids and terpenes influences the overall application profile.
• Volatility: A COA reliably indicates through low terpene levels whether a product has been stored too long or is too dry.

Microbiological limits and contaminants

In addition to the active ingredients, the purity of the product is crucial for health safety. A complete COA therefore contains detailed information on microbiological contamination such as moulds, yeasts and aerobic bacteria. These germs can get onto the flowers during cultivation, harvesting or packaging. Since cannabis is often inhaled, mould spores pose a serious risk to the respiratory tract, which is why compliance with strict limit values is essential.

In Switzerland, laboratories and cantonal control bodies base their standards on the guideline values for food or consumer goods. A reputable test report compares the measured colony-forming units (CFU) directly with the legally permissible maximum values. If these limit values are exceeded, the product may not be placed on the market in Switzerland. Consumers should therefore specifically ensure that the field for microbiological testing in the COA is marked as passed.

• Health protection: Microbiological tests for moulds and yeasts prevent risks during inhalation.
• Colony-forming units: The indication in CFU shows the exact load of living microorganisms.
• Statutory guideline values: Swiss laboratories compare the measured values with food safety requirements.
• Safety status: A passed purity test is recognizable by markings such as 'Pass' or 'Bestanden'.

FAQ