4 Steps to Read a COA: Minnesota Cannabis Testing for Consumers, Trainees

Sep 5, 2026 | Education

4 Steps to Read a COA: Minnesota Cannabis Testing for Consumers, Trainees

Trainee loading a sample into lab instrument

Cannabis lab testing verifies potency and screens for contaminants so products are safe, accurately labeled, and compliant with regulators. Labs run a mix of instruments, HPLC, GC-MS, LC-MS/MS, ICP-MS, and PCR, chosen for whichever analyte they’re chasing, then issue a Certificate of Analysis, or COA, that documents the results. The two signals worth trusting most are ISO/IEC 17025 accreditation and a COA with clear batch, method, and detection-limit information.

TL;DR:

  • A COA’s reliability depends on representative sampling across the batch and a strict chain of custody to ensure the sample reflects the entire product.
  • Labs use specific instruments like HPLC for potency and ICP-MS for metals, with accreditation and proficiency testing being critical indicators of trustworthy results.
  • Testing panels vary by product type, with concentrates requiring solvent checks and flower needing moisture and foreign material screening to prevent storage issues.
  • Detection limits are crucial, as “not detected” means below the lab’s threshold, not necessarily zero, affecting safety assumptions.
  • Regulatory standards for cannabis testing differ widely by state, making it essential to understand regional requirements and how they influence product legality and safety.

Table of Contents

What Labs Actually Test For in Cannabis Products

Every batch of cannabis that reaches a Minnesota shelf, or any legal market, is supposed to pass through a set of standard test panels before it’s sold. State regulators, including California’s Department of Cannabis Control, require labs to screen for cannabinoids, terpenes, residual solvents, pesticides, heavy metals, microbial impurities, mycotoxins, moisture content, and foreign material before a licensed testing laboratory can report results.

Potency testing measures cannabinoids like THC, THCA, CBD, CBDA, and CBN, plus a terpene profile that shapes flavor and aroma. Pesticide screening looks for dozens of compounds, and some carry outsized risk. Myclobutanil, a fungicide, converts into hydrogen cyanide gas when heated, which makes it a particular concern for anything meant to be smoked or vaporized.

Heavy-metal screening checks for lead, arsenic, cadmium, and mercury, elements that accumulate in cannabis plants from contaminated soil or water and build up in the body with repeated exposure. Microbial testing catches things like E. coli, Salmonella, and mold, while mycotoxin screening targets toxins produced by fungi such as Aspergillus, a genus that poses real danger to people with weakened immune systems, according to research on cannabis contaminants.

Not every panel applies equally to every product type:

  • Residual solvents matter most for concentrates and vape products made with butane, propane, or ethanol extraction.
  • Microbial and heavy-metal panels apply across the board, from flower to edibles to tinctures.
  • Moisture and water activity checks matter most for flower, where excess moisture invites mold growth during storage.
  • Foreign material inspection (hair, insects, packaging fragments) applies broadly but catches the most issues in hand-trimmed flower.

On a COA, you’ll usually see either a numeric result, a PASS or FAIL, or “ND” for not detected. ND doesn’t always mean zero. It means the lab didn’t find the substance above its detection threshold, a distinction that matters more than it looks. If you’re new to cannabis products generally, our guide to responsible cannabis consumption covers how potency numbers translate into real-world dosing.

Why Sampling and Chain of Custody Decide Whether a COA Means Anything

A COA is only as good as the sample it came from. Cannabis flower isn’t uniform. Potency and contaminant levels can shift noticeably between the top and bottom of a single plant, let alone across a batch of hundreds of pounds. That’s why representative sampling, pulling small amounts from multiple points across a batch rather than grabbing a handful from one spot, is the foundation every other test result rests on.

Chain of custody is the paper trail that follows a sample from the plant to the lab bench. Here’s roughly how it works:

  1. A licensed sampler collects material from designated points across the batch, following a documented protocol.
  2. Each sample gets labeled with a batch ID, collection date, and sampler identity, then sealed to prevent tampering.
  3. The sample travels to the lab with a transport log noting time, temperature, and handling.
  4. The lab logs receipt, confirms the seal is intact, and assigns an internal tracking number before testing begins.

California’s representative sampling checklist for distributors lays out exactly this kind of protocol, and most legal markets require something similar. Skipping steps, or “lab shopping” for a facility known to be lenient, undermines the entire system, because a COA built on a bad sample tells you nothing true about the batch you’re actually buying.

Pro Tip: Ask any licensed retailer for the batch ID and sample collection date printed on the COA, then confirm those match the product in front of you. If they don’t line up, that mismatch is reason enough to ask questions before you buy.

Technician securing sample for chain of custody

Anyone curious about the mechanics of specimen handling more broadly can look at protocols like specimen collection training for drugs of abuse testing, which covers chain-of-custody principles that echo across testing industries, not just cannabis.

The Instruments Behind Every Number on a COA

Different analytes need different tools, and the instrument listed in a lab’s method notes tells you something about how trustworthy a given number is.

High-Performance Liquid Chromatography (HPLC) is the preferred method for potency testing because it separates and measures cannabinoids without applying heat. That matters because heat converts THCA, the non-intoxicating acidic form of THC found in raw plant material, into active THC. A method that heats the sample during testing can distort the potency numbers on the label. Total THC is calculated using the formula THCA × 0.877 + THC, a conversion factor that accounts for the loss of a molecular group (carboxylic acid) during that heat-driven change.

Gas Chromatography (GC), GC-MS, and GC-MS/MS work well for volatile compounds like terpenes and some solvent residues, since these techniques do involve heat to vaporize the sample. That’s a fine trade-off for terpenes but a real limitation for cannabinoid potency, which is why the industry generally reserves HPLC for potency and GC-based methods for volatiles.

LC-MS/MS (liquid chromatography with tandem mass spectrometry) brings high sensitivity to pesticide and mycotoxin screening. The “tandem” part means the instrument fragments and confirms molecules in two stages, which cuts down on false positives compared to single-stage detection.

ICP-MS (inductively coupled plasma mass spectrometry) detects heavy metals at extraordinarily low concentrations, often down to parts-per-billion levels, which is necessary since lead and arsenic pose risks even in trace amounts.

PCR and qPCR (polymerase chain reaction) detect microbial DNA quickly, while older culture-based methods grow organisms over days to confirm they’re actually alive and viable. PCR is faster; culture methods confirm whether the pathogen was ever a real threat.

A few reporting terms show up on nearly every COA:

  • LOD (limit of detection): the smallest amount a method can reliably distinguish from background noise.
  • LOQ (limit of quantitation): the smallest amount a method can measure with confidence, not just detect.
  • ND: not detected, meaning the result fell below the LOD.
  • <LOQ: detected, but too low a level to report a precise number.

GC-MS pesticide screening commonly reaches detection sensitivity around 0.1 parts per million for many compounds, which is precise enough to catch residue levels far below what would cause acute harm, though it still leaves room for debate about chronic low-level exposure.

How Labs Prove Their Results Can Be Trusted

Accreditation is the difference between a lab you can trust and one that’s just printing numbers on letterhead. ISO/IEC 17025 is the international standard covering method validation, instrument calibration, staff training, and overall quality management for testing laboratories. A lab holding this accreditation has been independently audited on all four fronts, not just told to self-report.

Proficiency testing adds a second layer of accountability. NIST’s CannaQAP (Cannabis Laboratory Quality Assurance Program) sends identical samples to multiple labs and compares their results, exposing systematic differences in how labs measure the same material. These exercises have documented real inter-laboratory differences across cannabinoids, moisture, and toxic elements, which is exactly the kind of comparability problem the program exists to fix.

Even with strong methods, potency results can vary by noticeable percentage points between labs testing the same sample, a gap tied to differences in extraction technique, calibration standards, and instrument maintenance rather than sloppy work. Contaminant pass/fail results tend to be more consistent across labs than potency percentages, since a pass/fail threshold is a simpler comparison than a precise quantitative number.

Watch for these red flags on a lab report:

  • No accreditation number or certificate listed anywhere on the document.
  • Method notes that are vague or missing entirely (no mention of HPLC, GC-MS, or similar).
  • Potency numbers that round suspiciously to the same decimal across many different products.
  • No LOD/LOQ values listed for contaminant panels.

Reading a Certificate of Analysis: A Practical Checklist

A COA is a document you can actually learn to read in a few minutes once you know what to look for.

  1. Check the header. Confirm the lab’s name, license number, ISO/IEC 17025 accreditation status, batch or sample ID, and both the collection date and test date.
  2. Review potency lines. Look at THC, THCA, CBD, and total THC. If the total THC doesn’t roughly match the THCA × 0.877 + THC formula, or if numbers look biologically implausible (extremely high totals with no listed moisture content, for instance), treat that as a caution flag.
  3. Scan the safety panels. Confirm PASS, FAIL, or ND status for pesticides, heavy metals, and microbials, and check that units (ppm, ppb, CFU/g) are listed, not just bare numbers.
  4. Respond to a FAIL appropriately. Ask the retailer or producer for remediation documentation, request a re-test result, or simply decline the purchase if none of that is available.

How Long Cannabis Lab Testing Actually Takes

Standard turnaround for a full test panel typically runs anywhere from a few days to over a week, though that range shifts based on a handful of factors. Lab workload is the biggest driver. During harvest season, when cultivators across a region are all submitting batches at once, labs can back up and turnaround stretches out.

The complexity of the panel matters too. A basic potency screen using HPLC moves faster than a full compliance panel that also requires pesticide, heavy-metal, and microbial testing, since each of those adds its own instrument run and confirmation step. Retesting after a failed batch adds more time on top of the original process, since remediation efforts (like additional drying or an extraction step to strip out a contaminant) have to happen before a new sample can even be submitted.

Instrument availability plays a role as well. A lab running LC-MS/MS for pesticide confirmation can only process as many samples as it has instrument time for, and equipment maintenance or calibration checks can pull a machine offline for a portion of a day. For businesses, tight turnaround times are a genuine operational pressure, since product can’t legally reach shelves until it clears every required test. That pressure is part of why understanding this process is a real, marketable skill in the industry, not just background trivia for curious consumers.

Regulatory Standards Vary Sharply by Region

There is no single federal testing standard for cannabis in the United States, and that gap shapes almost everything about how labs operate. Each state that has legalized cannabis, medical or recreational, sets its own required panels, action limits for contaminants, and accreditation rules, which means a product tested and approved in one state might not clear the bar in another.

California’s Department of Cannabis Control, for example, spells out specific mandatory panels and reporting procedures that licensed labs must follow, down to how COAs get uploaded and tracked. Minnesota’s own regulatory framework, still maturing as the state’s adult-use market grows, draws on lessons from states that legalized earlier while adapting requirements to local priorities. Federal guidance that does exist, like the FDA’s residual solvent limits built for pharmaceutical products, gets borrowed and adapted by state cannabis regulators rather than applied directly, since cannabis itself remains federally restricted.

This patchwork means a COA that looks reassuring in one market context doesn’t automatically translate to another. Anyone buying, selling, or working with cannabis products across state lines needs to understand that the rules underneath the paperwork actually shift depending on where the product was grown, processed, and sold.

MNCC Perspective: Why Lab Literacy Belongs in Every Cannabis Career

We think reading a COA fluently is as much a job skill as trimming a plant or running a point-of-sale system, and honestly, it doesn’t get enough attention in conversations about cannabis careers. A cultivator who understands why heavy-metal levels spike in certain soil conditions grows a cleaner crop. A manufacturing technician who knows why residual solvents matter builds a safer extraction process. A retail worker who can explain an ND result to a customer builds real trust at the counter.

MNCC Perspective: Why Lab Literacy Belongs in Every Cannabis Career — overview diagram

That’s why training tracks in retail, cultivation, and manufacturing benefit from hands-on exposure to this material, not just lecture slides. Participants work through lab exercises, practice interpreting COA formats, and visit active cannabis businesses to see testing and compliance play out in a working facility, not just a classroom. If you’re curious how extraction and testing intersect, our page on cannabis concentrates in Minnesota is a good next stop.

We built our workforce training programs to be tuition-free through state grant funding, because we believe this kind of career-ready knowledge should be open to everyone, especially folks from communities that carried the weight of cannabis prohibition the longest. If you’re weighing a career in this industry, or you’re an employer looking for workers who understand compliance from the ground up, we encourage you to explore available training options.

— Minnesota Cannabis College

This article is general information, not a substitute for advice from a qualified doctor. Consult a qualified healthcare professional about your own circumstances before acting on anything here.

Sources

Disclaimer: This content is provided by Minnesota Cannabis College, a 501©(3) nonprofit organization, for educational and informational purposes only. Nothing in this post constitutes legal, medical, or financial advice, and no reader should act or refrain from acting on the basis of this content without seeking advice from a qualified professional. Cannabis laws and regulations are subject to change, and readers are responsible for verifying requirements applicable to their circumstances.