Free tool · HPLC-UV potency · 228 nm
How we read a potency trace.
An HPLC-UV run of THC-dominant flower, drawn the way the instrument draws it. Each peak is a compound. Where it lands and how big it is tell a lab what to check next.
Twelve cannabinoids, in the order a C18 column separates them. Select one to read what its peak tells a lab, or read all twelve ↓
CBDVA cannabidivarinic acid · 1.88 min · not detected
First cannabinoid off the column. Usually absent in THC flower. When it is present, its peak has to clear the solvent front before anyone can quantify it.
CBDV cannabidivarin · 2.09 min · not detected
The neutral form of CBDVA. Not detected here, which is normal for THC-dominant flower.
CBDA cannabidiolic acid · 2.59 min · quantified
The acid form of CBD, so total CBD = CBD + 0.877 × CBDA. A small peak in THC flower; on hemp it is the headline.
CBGA cannabigerolic acid · 2.75 min · quantified
The precursor the plant makes THCA, CBDA and CBCA from. Often the second-largest peak in THC flower.
CBG cannabigerol · 2.91 min · quantified
CBGA after decarboxylation. CBDA, CBGA, CBG and CBD elute within half a minute of each other, so a small drift in the mobile phase can merge them.
CBD cannabidiol · 3.08 min · below LOQ
Near zero in THC-dominant flower. The peak is there, but its signal-to-noise is below the limit of quantitation, so the certificate reports <LOQ.
THCV tetrahydrocannabivarin · 3.39 min · below LOQ
The propyl cousin of Δ9‑THC. Its shorter side chain holds less tightly to C18, so it elutes more than two minutes before Δ9‑THC.
CBN cannabinol · 4.61 min · quantified
Forms as THC oxidizes. A growing CBN peak says the sample is old, or was stored warm or in light.
Δ9-THC delta-9-tetrahydrocannabinol · 5.82 min · quantified
The regulated compound. Fresh flower carries little; most of it forms when THCA is heated. Δ8‑THC elutes 0.18 min later, and the method has to keep the two apart.
Δ8-THC delta-8-tetrahydrocannabinol · 6.00 min · not detected
Not detected here. Δ8 and Δ9 differ only in where one double bond sits. That makes them a critical pair: a method that cannot resolve them reports one as the other.
CBC cannabichromene · 7.26 min · quantified
Minor in most flower. It elutes 0.35 min before THCA, the largest peak in the run, so an overloaded THCA peak can swallow it.
THCA tetrahydrocannabinolic acid · 7.61 min · quantified
The dominant peak in THC flower. Heat turns it into Δ9‑THC, so labs report total THC = Δ9‑THC + 0.877 × THCA. The 0.877 is the ratio of their molecular weights (314.5 / 358.5).
Peak by peakRetention times from a published C18 method
Twelve cannabinoids, in the order they leave the column.
On a reversed-phase C18 column the more polar compounds elute first. Order and times follow a published isocratic method; a different column or mobile phase moves the times, and can swap neighbors.
| # | Compound | RT, min | In this run | What it tells a lab |
|---|---|---|---|---|
| 01 | CBDVAcannabidivarinic acid | 1.88 | not detected | First cannabinoid off the column. Usually absent in THC flower. When it is present, its peak has to clear the solvent front before anyone can quantify it. |
| 02 | CBDVcannabidivarin | 2.09 | not detected | The neutral form of CBDVA. Not detected here, which is normal for THC-dominant flower. |
| 03 | CBDAcannabidiolic acid | 2.59 | quantified | The acid form of CBD, so total CBD = CBD + 0.877 × CBDA. A small peak in THC flower; on hemp it is the headline. |
| 04 | CBGAcannabigerolic acid | 2.75 | quantified | The precursor the plant makes THCA, CBDA and CBCA from. Often the second-largest peak in THC flower. |
| 05 | CBGcannabigerol | 2.91 | quantified | CBGA after decarboxylation. CBDA, CBGA, CBG and CBD elute within half a minute of each other, so a small drift in the mobile phase can merge them. |
| 06 | CBDcannabidiol | 3.08 | below LOQ | Near zero in THC-dominant flower. The peak is there, but its signal-to-noise is below the limit of quantitation, so the certificate reports <LOQ. |
| 07 | THCVtetrahydrocannabivarin | 3.39 | below LOQ | The propyl cousin of Δ9‑THC. Its shorter side chain holds less tightly to C18, so it elutes more than two minutes before Δ9‑THC. |
| 08 | CBNcannabinol | 4.61 | quantified | Forms as THC oxidizes. A growing CBN peak says the sample is old, or was stored warm or in light. |
| 09 | Δ9-THCdelta-9-tetrahydrocannabinol | 5.82 | quantified | The regulated compound. Fresh flower carries little; most of it forms when THCA is heated. Δ8‑THC elutes 0.18 min later, and the method has to keep the two apart. |
| 10 | Δ8-THCdelta-8-tetrahydrocannabinol | 6.00 | not detected | Not detected here. Δ8 and Δ9 differ only in where one double bond sits. That makes them a critical pair: a method that cannot resolve them reports one as the other. |
| 11 | CBCcannabichromene | 7.26 | quantified | Minor in most flower. It elutes 0.35 min before THCA, the largest peak in the run, so an overloaded THCA peak can swallow it. |
| 12 | THCAtetrahydrocannabinolic acid | 7.61 | quantified | The dominant peak in THC flower. Heat turns it into Δ9‑THC, so labs report total THC = Δ9‑THC + 0.877 × THCA. The 0.877 is the ratio of their molecular weights (314.5 / 358.5). |
Before we trust a run
Five checks before a potency number goes on a certificate.
- Resolution. The closest pairs, CBDA and CBGA early in the run and Δ9- and Δ8-THC later, separate to baseline: a resolution of 1.5 or better.
- Retention time. Every peak lands inside its window, set from the calibration standards. A peak outside its window is not identified, however close it looks.
- Calibration. A check standard run mid-sequence recovers within its limits, or the samples since the last good check run again.
- Carryover. A blank after the highest standard shows nothing where THCA elutes.
- Range. THCA falls inside the calibrated range. If it doesn’t, dilute and rerun; never extrapolate.
When one of these keeps failing, the fix is usually in the method or the instrument, not the spreadsheet. That’s the work we do on HPLC, GC and ICP-MS systems.
SourcesChecked 2026-09-28
- Elution order and retention times: Restek, “16 Cannabinoids on Raptor ARC-18 2.7 µm by LC-UV” ↗ (LC_GN0578), an isocratic C18 method with UV detection at 228 nm. Shimadzu Application News SSI-HPLC-016 shows the same order.
- Total THC = Δ9-THC + 0.877 × THCA: the factor is the ratio of the molecular weights (314.5 / 358.5), as written into the California DCC regulations ↗ (§15724).
- Peak heights are illustrative, typical of THC-dominant flower. The trace is not sample data.
Next stepFree, no pitch deck