How to Read a Certificate of Analysis: Your Guide to Lab-Tested Herbal Quality

How to Read a Certificate of Analysis: Your Guide to Lab-Tested Herbal Quality

Last Updated: February 10, 2026

At Sacred Plant Co, we believe transparency begins where the lab meets the leaf. Every bag of herbs we ship carries a QR code linked directly to a certificate of analysis (COA), a document that proves your herbs were tested, verified, and safe before they ever left our facility. But transparency only works when you can actually read what you are looking at.

That commitment to verifiable quality is central to our regenerative philosophy. Plants grown in biologically active soil produce richer concentrations of secondary metabolites, the terpenes, flavonoids, and volatile oils that give herbs their medicinal potency.1 When soil microbiology thrives, plants express stronger defense chemistry. When that chemistry is then verified through third-party lab testing, you hold genuine proof of quality in your hands. You can explore the transparency in herbal safety that drives every decision we make, or dig into the Regen Ag Lab living soil metrics that document how we achieved a 400% increase in soil biology in a single season.

This guide walks you through each section of a certificate of analysis using our peppermint leaf (LOT # PPRL5202) as a real example. You will learn what every test measures, what the numbers mean, and which red flags to watch for when evaluating any herbal product.

What Is a Certificate of Analysis?

A certificate of analysis is a document issued by an accredited laboratory that verifies the identity, purity, and safety of a specific batch of herbal material. In the botanical industry, COAs serve as third-party proof that herbs meet established safety standards for microbial contamination, heavy metals, pesticides, and physical purity.

Every lot of herbs we offer undergoes independent testing before it reaches you. The COA you access via QR code allows you access to the exact lot number printed on your bag. This batch-specific testing matters because growing conditions, harvest timing, and processing methods vary between lots, even for the same plant species.

A COA tells you the botanical identity and lot number of the tested material, the physical characteristics like color, aroma, form, and particle size, the microbial load including bacteria, yeast, mold, and pathogens, the heavy metal concentrations for arsenic, cadmium, lead, and mercury, the foreign material inspection results from both visual and metal detection, and any certification status such as kosher, wildcrafted, or the sterilization method used.

The American Herbal Products Association (AHPA) publishes widely accepted microbial and heavy metal limits for botanical ingredients.2 Most reputable labs reference AHPA standards when determining pass/fail thresholds. Our testing follows AOAC International methods, which are recognized globally for food and botanical analysis.3

Material Information: Identity and Traceability

The top section of any COA establishes what material was tested, who tested it, and how to trace it back to your specific product. Our peppermint COA lists the material name as "Peppermint leaf" with the Latin binomial Mentha piperita. Latin names eliminate confusion. Common names vary by region, but Mentha piperita identifies one specific species recognized worldwide.

The lot number (PPRL5202 in this example) functions as the batch's unique identifier. When you scan the QR code on your bag, the lot number printed on the label must match the lot number on the COA. This matching process ensures you are viewing results for the exact material you purchased, not generic test results from a different batch.

Key material details include the plant part tested (leaf, root, flower), the processing form such as cut and sift, powder, or whole, the sterilization method used to reduce microbial load (steam, irradiation, or other methods), the manufacture date when the lot was processed and packaged, and the retest date marking shelf life expiration based on stability testing.

Our peppermint was steam treated, which uses pressurized steam to reduce microbial counts without chemical residues or irradiation. The manufacture date of February 6, 2025, paired with a three-year shelf life, means this lot should be retested by February 6, 2028. Proper storage in cool, dry conditions extends shelf life and preserves volatile oils. For detailed guidance on maintaining herb quality at home, our guide to buying, storing, and using herbs in bulk covers everything from container selection to temperature control.

How to Identify Premium Peppermint Leaf

Before any lab instrument touches the sample, trained technicians perform a sensory evaluation that catches problems machines can miss. This section of the COA documents what the herb looks like, smells like, and tastes like, and these observations serve as the first line of quality defense.

For peppermint leaf, the COA notes green to dark green color, minty and sweet aroma, and minty and fresh taste. High-quality dried peppermint should display a vibrant green to deep green hue, not grey or brown. Grey coloring signals oxidation from improper drying or extended storage, while brown suggests heat damage during processing. The leaves should feel crisp and snap cleanly when bent, not flex like a soft, stale leaf. A peppermint leaf that bends without breaking has absorbed excess moisture and may harbor microbial growth.

Aroma is the most telling sensory indicator. Premium peppermint releases a sharp, bright menthol note the moment you open the bag, with underlying sweet, herbaceous tones. A flat or musty smell indicates degraded volatile oils or possible mold contamination. When steeped, the flavor should register as cooling and clean on the palate, with a slight sweetness that lingers without bitterness. Bitter or chemical notes reveal contamination or improper processing.

The form listed as "cut and sift" tells you the particle size. Cut and sift means the leaves were chopped and sifted through screens to remove stems and achieve uniform sizing. This matters for extraction efficiency and tea brewing. Powdered herbs extract faster but lose volatile oils more quickly during storage. Whole leaves preserve aromatics longer but require more processing before use.

Microbial Testing: Understanding Colony Counts

Microbial testing measures the number and type of microorganisms present in a herbal sample, confirming that bacterial, yeast, and mold counts fall below established safety thresholds. This section often confuses first-time COA readers because the numbers seem enormous. Our peppermint shows a total plate count of 130,000 CFU/G against a limit of 10,000,000 CFU/G. That sounds like a lot of bacteria. It is, but context matters.

CFU/G stands for colony-forming units per gram. It measures how many viable microorganisms are present in a sample. One CFU represents a single bacterial cell or spore capable of reproducing into a visible colony on a petri dish. The testing method (Petrifilm AOAC 990.12) uses standardized growth media to culture and count these colonies.3

Plants grow in soil, which teems with microbes. Even after washing and drying, some environmental bacteria remain on botanical materials. The question is not whether bacteria exist but whether harmful pathogens are present and whether total counts exceed safe thresholds. Research on herbal safety suggests that total aerobic counts below 10 million CFU/G pose minimal risk for dried botanical materials intended for infusion.4

Each microbial test on the COA measures something specific. Total Plate Count captures all aerobic bacteria present, both harmless and potentially harmful. Yeast testing measures fungal organisms that can spoil herbs in humid conditions. Mold testing identifies filamentous fungi that produce visible growth and potential mycotoxins. Total Coliform serves as an indicator of fecal contamination or poor sanitation. E. coli testing identifies a specific pathogen indicating direct fecal contamination. Salmonella testing uses PCR for rapid detection of this dangerous pathogen.

Our peppermint passed all microbial tests with exceptional results. Yeast and mold came back below 10 CFU/G, which is the detection limit. That means the lab found virtually no fungal growth whatsoever. Total coliform measured 200 CFU/G against a limit of 1,000 CFU/G. Both E. coli and Salmonella tested completely negative, confirming zero pathogenic bacteria were detected in the sample.

Steam treatment, which this lot underwent, reduces microbial load significantly while preserving phytochemical content. The absence of pathogens and exceptionally low total counts indicate proper post-harvest handling, effective sterilization, and appropriate storage conditions throughout the supply chain.

Heavy Metal Testing: Safety Limits Explained

Heavy metal testing verifies that arsenic, cadmium, lead, and mercury concentrations in herbal material remain safely below established regulatory limits. Plants absorb minerals from soil, including trace heavy metals. Some metals like iron and zinc are essential nutrients. Others like lead and mercury are toxic even at low concentrations and accumulate in body tissues over time.

The COA lists four priority metals. California's Proposition 65 and international pharmacopeias set maximum daily intake limits for these contaminants in herbal products.5 AHPA's guidance policies provide the industry-standard framework that most reputable labs reference.2

Our peppermint heavy metal results for Lot PPRL5202 are as follows. Arsenic measured 0.07 PPM against a limit of 1 PPM, a clear pass. Cadmium was not detected at all against a limit of 1 PPM. Lead measured 0.11 PPM against a limit of 3 PPM. Mercury measured 0.02 PPM against a limit of 1 PPM. All four metals passed with results far below their respective limits.

PPM stands for "parts per million," a scientific way of expressing trace concentrations. One PPM equals one milligram per kilogram. So 0.07 PPM arsenic means just seven hundredths of one milligram in an entire kilogram of peppermint. That is roughly equivalent to one grain of sand dissolved in fifteen gallons of water. At typical serving sizes of 1 to 2 grams per cup of tea, you would be consuming only 0.00007 to 0.00014 milligrams of arsenic per serving, far less than what is naturally present in many fruits, vegetables, and even bottled waters.

The testing method (#C55 AOAC 2015.01) uses inductively coupled plasma mass spectrometry (ICP-MS), which can detect metals at extremely low concentrations.3 This sensitivity allows labs to catch contamination long before it reaches harmful levels.

Different regulatory bodies set different thresholds. AHPA recommends limits based on daily consumption patterns. WHO guidelines consider cumulative exposure from all dietary sources. More restrictive limits (like California Prop 65) aim to minimize any measurable risk over a lifetime of exposure. Labs typically test to the strictest standard applicable to their market. The fact that cadmium was not detected at all, meaning concentrations fell below the instrument's detection threshold, confirms that the growing conditions and soil quality produced an exceptionally clean crop.

Foreign Material Inspection: Purity Standards

Foreign material inspection uses visual examination and metal detection to verify that dried herbs contain no non-botanical contaminants above established limits. Labs examine samples in two categories: organic and inorganic foreign material.

Organic foreign material includes plant parts from other species, insect fragments, animal waste, or non-target portions of the correct plant (like stems mixed into leaf-only material). Our peppermint tested at less than 2.0% pieces by weight, meaning more than 98% of the sample consisted of pure peppermint leaf.

Inorganic foreign material covers soil, sand, rocks, glass, and metal fragments. The COA specifies detection limits: less than 4.0mm ferrous (iron-based), nonferrous (non-magnetic metals like aluminum), and stainless steel. Any metal fragments larger than 4mm would trigger a failure. Our peppermint passed with less than 2.0% inorganic material by weight.

Physical contaminants enter botanical materials during harvest, processing, or packaging. Proper cleaning, sifting, and metal detection eliminate most problems, but batch testing confirms these quality control steps worked as intended.

Certifications and Compliance Notes

The certifications section lists any special designations and compliance declarations for the tested lot, confirming processing standards and the absence of additives. Our peppermint is certified kosher, meaning it was processed according to Jewish dietary law under rabbinical supervision. Other certifications you might see on COAs include wildcrafted (harvested from natural habitats) or Fair Trade.

The bottom of our COA includes compliance statements: "No pesticides were used to grow this product. This product is free of any additives or preservatives. No solvents were used to produce this product, nor excipients." These declarations address common concerns about botanical processing. Some herbs undergo solvent extraction to concentrate active compounds. Others receive preservatives to extend shelf life or flowing agents to improve handling. Our peppermint contains none of these additives. What you see is what you get: leaves, steam treatment, and nothing else.

Storage instructions appear here too: "Store under cool, dry conditions in sealed container." This guidance is not arbitrary. Heat and humidity degrade volatile oils and promote microbial growth. Exposure to air oxidizes delicate compounds. Proper storage preserves the quality documented in the COA throughout the product's shelf life.

Red Flags to Watch For in Any COA

Knowing what a fraudulent, incomplete, or outdated COA looks like is just as important as understanding a passing one. Not every company provides transparent testing, and not every COA meets the same standards.

Missing Information: A legitimate COA includes testing methods, lot numbers, and pass/fail determinations. If any of these elements are absent, question the document's validity. Generic COAs that do not reference specific batch numbers or manufacture dates may not represent the actual product you received.

Failed Tests: Any result marked "FAIL" means the product exceeded safety limits. Microbial counts above thresholds suggest contamination or poor handling. Heavy metals above limits indicate unsafe exposure levels. Herbal suppliers should never release failed lots to consumers.

No Pathogen Testing: A COA that lists total plate count but omits E. coli and Salmonella testing is incomplete. Total counts tell you about overall microbial load, but only specific pathogen tests confirm the absence of harmful organisms.

Suspiciously Perfect Results: While passing all tests is ideal, results that show exactly zero for every measurement or round numbers across the board may indicate fabricated data. Real lab results include decimal places, detection limits, and some natural variation between samples.

Outdated Testing: Check the manufacture date and retest date. If the COA predates your purchase by years, you are not viewing results for your specific lot.

Missing AOAC Methods: Reputable labs cite standardized testing protocols. AOAC International methods are industry standard for food and botanical analysis.3 ISO methods are also acceptable. If testing methods are not listed or reference proprietary procedures, you cannot verify that appropriate scientific protocols were followed.

How We Use COAs at Sacred Plant Co

Every herb we stock undergoes third-party testing before we accept delivery, and we reject any material that fails microbial, heavy metal, or purity standards. Suppliers who consistently deliver clean material earn our continued business. Those who ship contaminated lots lose it.

Once herbs pass inspection and reach our facility, we assign batch numbers and print labels with QR codes. Scanning the code on your bag pulls up the exact COA for your lot. This system ensures full traceability from farm to cup. If you brew peppermint tea, you can verify that the leaves in your infuser came from lot PPRL5202, grown and tested exactly as documented.

We store COAs indefinitely in our database. Even years after purchase, you can return to the QR code and review the original test results. This permanent record supports transparency and gives you reference material if you want to compare testing between different lots or suppliers.

Some companies test only the first batch of a new herb and then skip testing for subsequent lots. We test every single batch because growing conditions change, weather affects harvests, and processing variables introduce risk. Batch-specific testing costs more, but it catches problems before they reach customers. That commitment to verification pairs with our broader philosophy. You can see the science behind our methods to understand how regenerative practices and rigorous testing work together.

Comparing Testing Standards Across Suppliers

Once you know how to read a COA, you can compare quality across suppliers by evaluating testing frequency, threshold strictness, pathogen screening methods, and document accessibility. Not all companies test to the same standards or provide equal transparency. Here is what to look for.

Testing Frequency: Does the company test every batch or only sample batches? Consistent testing demonstrates commitment to quality. Sporadic testing suggests cost-cutting.

Heavy Metal Thresholds: Some suppliers use lenient limits that would fail under stricter regulatory frameworks. Compare the listed limits to AHPA recommendations or California Prop 65 standards. Lower limits indicate more conservative safety margins.

Pathogen Screening: Basic testing might skip Salmonella or use less sensitive detection methods. PCR testing (like the BAX method referenced in our COA) detects pathogens more reliably than older culture-based techniques.

Accessibility: Can you easily access COAs before purchasing? QR codes on individual bags provide better traceability than batch numbers you must email to request. Some companies hide COAs behind customer service requests or provide only generic summaries rather than full lab reports.

Lab Accreditation: Third-party labs should hold ISO 17025 accreditation, which verifies their competence to perform specific tests.6 In-house testing by the supplier raises questions about objectivity and conflicts of interest.

Accessing Your COA

Every bag we ship includes a QR code printed on the label that links directly to the full certificate of analysis for your specific lot number. Use your smartphone camera to scan the code. It will open a webpage displaying the complete lab results for the exact material in your bag. You do not need to download an app or create an account.

We encourage you to save or print COAs for your records, especially if you are using herbs therapeutically and want to track which batches worked best for you. Lab results provide objective data you can share with healthcare practitioners who may be unfamiliar with botanical quality standards.

Understanding certificates of analysis transforms you from passive consumer to informed herbalist. When you know what to look for, you can verify safety, compare quality, and make purchasing decisions based on data rather than marketing claims.

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Certificate of Analysis FAQs

What is a Certificate of Analysis (COA)?

A Certificate of Analysis is a document issued by an accredited laboratory that verifies the identity, purity, and safety of a specific batch of material. For herbal products, COAs provide third-party proof that herbs meet established safety standards for microbial contamination, heavy metals, pesticides, and physical purity. Each COA corresponds to a specific lot number, ensuring batch-specific testing rather than generic results.

What does CFU/G mean on a COA?

CFU/G stands for colony-forming units per gram, a measure of how many viable microorganisms are present in a sample. One CFU represents a single bacterial cell or spore capable of reproducing into a visible colony on a petri dish. For dried herbs, total counts below 10 million CFU/G are considered safe. Plants naturally contain some soil microbes even after washing and drying, so the key is ensuring counts stay below safe thresholds and that harmful pathogens like E. coli and Salmonella are absent.

What does PPM mean in heavy metal testing?

PPM stands for parts per million, a unit that measures extremely small concentrations of a substance. One PPM equals one milligram per kilogram. For example, 0.07 PPM arsenic means just 0.07 milligrams of arsenic in one kilogram (1,000 grams) of herb. At typical serving sizes of 1 to 2 grams per cup of tea, you would be consuming only micrograms of these metals, well below any established safety threshold.

What are safe limits for heavy metals in herbs?

The American Herbal Products Association (AHPA) recommends the following limits for botanical ingredients: Arsenic at 1 PPM or less, Cadmium at 1 PPM or less, Lead at 3 PPM or less, Mercury at 1 PPM or less. Some regulatory bodies like California Proposition 65 set more restrictive limits. Reputable labs test to the strictest standard applicable to their market. Results well below these limits indicate exceptionally clean material.

Should E. coli and Salmonella always be negative on a COA?

Yes, both E. coli and Salmonella should always show "Negative" or "Not Detected" results on a herbal COA. These are pathogenic bacteria that indicate fecal contamination and can cause serious illness. Any positive result for these pathogens means the herb failed safety testing and should not be consumed. Labs typically use sensitive PCR testing methods (like the BAX method) to detect even trace amounts of these harmful organisms.

What is the difference between organic and inorganic foreign material?

Organic foreign material includes biological contaminants like plant parts from other species, insect fragments, or non-target portions of the correct plant. Inorganic foreign material covers non-biological contaminants like soil, sand, rocks, glass, and metal fragments. COAs test for both types and should show less than 2 to 4% by weight. Metal detection specifically checks for ferrous, nonferrous, and stainless steel particles above size limits (typically 4mm).

What red flags should I watch for in a COA?

Watch for these warning signs: missing testing methods or lot numbers, any tests marked "FAIL," absence of pathogen testing, suspiciously perfect results with all exact zeros, outdated testing that predates your purchase by years, and no AOAC or ISO method citations. Legitimate COAs include standardized testing protocols, show natural variation in results, and provide batch-specific documentation tied to your product's lot number.

Conclusion

A certificate of analysis is your window into everything that happened between the field and your cup. Once you understand what CFU/G and PPM actually mean, how microbial thresholds work, and what a clean heavy metal panel looks like, you stop taking quality on faith and start verifying it with data. That is exactly the kind of informed relationship we want you to have with your herbs.

Every bag we ship is backed by third-party lab verification. Every QR code on every label links to a real, batch-specific document. And every lot, without exception, must pass before it reaches our shelves. We built this system because we believe the herbs you put into your body deserve the same rigor you would expect from any medicine, and now you have the knowledge to confirm it for yourself.