Introduction
Every hemp brand navigating the November 12 compliance deadline is relying on laboratory testing to determine whether their products are compliant. But few brands — and even fewer retailers — understand what actually happens inside the lab when a hemp sample is tested for total THC.
This matters because the quality of testing varies significantly between labs. An ISO 17025-accredited lab performing a validated high-performance liquid chromatography (HPLC) method produces a fundamentally different and more reliable result than a non-accredited lab using an unvalidated method. Understanding the testing process helps buyers evaluate whether the COA they’re relying on is trustworthy — and understand why the accreditation status of the lab matters as much as the result itself.
Step 1: Sample Receipt and Chain of Custody Registration
The process begins before any chemistry happens. When a sample arrives at an ISO 17025-accredited hemp lab, the first step is formal receipt and registration into the lab’s chain of custody system.
The sample is assigned a unique accession number — the lab’s internal identifier for that specific sample submission. The receipt is documented: who submitted the sample, what the sample is described as, what tests are requested, when it was received, and the condition of the sample upon arrival (sealed container, intact packaging, no signs of tampering or degradation).
This registration step is what makes a COA independently verifiable — if you have the accession number, you can contact the lab and confirm that the result reported on the COA matches the result in their system for that accession number. Labs without this systematic receipt process cannot provide this verification.
Step 2: Sample Preparation
Hemp samples come in many physical forms: dried flower, crude extract, distillate, isolate, finished gummy, tincture, beverage. Each requires a specific sample preparation protocol to extract the cannabinoids into a form the analytical instrument can analyze.
For dried plant material (flower, biomass): The sample is typically ground and homogenized to create a representative composite, then extracted using an organic solvent (often ethanol or methanol) to dissolve the cannabinoids from the plant matrix.
For oil-based extracts (distillate, tinctures): The extract is typically diluted in an organic solvent to bring the cannabinoid concentrations into the calibrated range of the analytical instrument.
For solid-form products (gummies, capsules): Products are homogenized (blended, dissolved, or ground) before solvent extraction.
For beverages: The aqueous matrix requires additional extraction steps to separate cannabinoids from the water-based solution.
Sample preparation methodology significantly affects result accuracy. Inadequate homogenization of a non-uniform matrix (like a gummy with uneven cannabinoid distribution) can produce results that aren’t representative of the actual product. ISO 17025 accreditation requires that sample preparation methods be validated and documented.
Step 3: HPLC or HPLC-MS Analysis
The workhorse analytical method for hemp cannabinoid testing is High-Performance Liquid Chromatography (HPLC) — typically with UV/DAD detection or, in higher-specification labs, with mass spectrometry (HPLC-MS/MS).
How HPLC works: The prepared sample is injected into the HPLC system, where a mobile phase (liquid solvent) carries it through a stationary phase column. Different cannabinoid molecules travel through the column at different rates based on their chemical properties, separating from each other before detection.
UV/DAD detection: As each compound exits the column, it passes through a UV detector that measures absorbance at specific wavelengths. The detector generates a chromatogram — a graph of detector response versus time — with peaks corresponding to individual cannabinoids. Peak area is proportional to cannabinoid concentration.
Quantification: The lab compares peak areas against a calibration curve built from certified reference standards of known concentrations. This is how a peak area translates into a milligrams-per-gram or percentage cannabinoid result.
Why HPLC is preferred for total THC: Unlike GC (gas chromatography), HPLC does not decarboxylate THCA during analysis — meaning it can separately quantify both delta-9 THC and THCA, which is essential for the total THC calculation (delta-9 THC + THCA × 0.877).
Step 4: The Total THC Calculation
Once HPLC analysis produces separate results for delta-9 THC and THCA, the total THC calculation is applied:
Total THC = delta-9 THC + (THCA × 0.877)
The 0.877 factor represents the molecular weight conversion that occurs when THCA decarboxylates to delta-9 THC — losing a carboxyl group (CO₂ + H₂O). The factor is derived from the ratio of the molecular weights of delta-9 THC (314.46 g/mol) to THCA (358.48 g/mol): 314.46 / 358.48 = 0.877.
This calculation converts the THCA content into its delta-9 THC equivalent — the amount of psychoactive THC that would be present if the THCA were fully decarboxylated (e.g., by heating).
For compliance purposes, this total THC result (expressed in mg per container for finished products, or as a percentage by weight for bulk ingredients) is compared against the applicable standard.
Step 5: Result Review and COA Authorization
Before a COA is issued, ISO 17025 requirements mandate a result review process. A qualified reviewer (typically a senior analyst or laboratory director) checks:
- That the calibration curve was within acceptable parameters on the day of analysis
- That QC samples (blanks, duplicates, reference standards) were within acceptable ranges
- That the chromatography was clean (no interference peaks, baseline resolution between compounds)
- That the reported results match the instrument output without transcription errors
Only after this review does the COA get authorized and issued. The COA should include the accession number, the analyst name or identifier, the reviewer authorization, the analytical method reference, the instrument used, and the date of analysis.
What Makes One Lab’s Results More Reliable Than Another’s
All of the above steps can be done well or poorly. ISO 17025 accreditation is the systematic assurance that they’re being done well:
- Validated methods: The lab has demonstrated its methods produce accurate, repeatable results for hemp matrices
- Calibrated instruments: Equipment calibration is documented and current
- Qualified analysts: Personnel have documented training and competency
- QC program: Blanks, duplicates, and reference standards are run with every batch to catch instrument drift or method failure
- Document control: Records are maintained in a way that supports independent audit
A non-accredited lab may produce accurate results. But you have no independent assurance that their methods, instruments, or analysts meet any minimum standard. In an enforcement context, that distinction matters enormously.
🌿 LGH Perspective
At Low Gravity Hemp, we require ISO 17025-accredited lab COAs for every ingredient we supply — and we can walk our customers through the testing methodology documented on those COAs. Understanding what’s behind the number on a COA is how you evaluate whether that number is trustworthy. We’re happy to share our lab relationships and COA methodology with prospective customers who want to verify the quality of our documentation before placing an order.
Final Thoughts
Total THC testing is the evidentiary foundation of hemp compliance in 2026. Understanding how it works — from sample preparation through HPLC analysis to the total THC calculation and COA authorization — helps B2B buyers evaluate the COAs they’re relying on with the critical eye the compliance environment demands.
The number on the COA is only as trustworthy as the process that produced it.
Contact Low Gravity Hemp to review our testing methodology and source hemp ingredients with the lab documentation your compliance program requires.**
