A Certificate of Analysis is supposed to be proof. Proof that the green tea extract you are about to pay for — and put inside a product your customers will consume — is exactly what the supplier claims it is.
In practice, for a significant proportion of green tea extract CoAs circulating in the global supply chain, the document is something different. It is a commercially optimized summary of selected analytical data, generated under method conditions chosen to produce favorable numbers, from a sample that may or may not represent the batch you will receive.
Every item on the checklist below represents a specific failure mode — a real analytical gap, a genuine regulatory risk, or a documented fraud vector. For the financial model quantifying what bad CoAs cost, see our 2026 EGCG True Cost Analysis. For the analytical deep-dive on HPLC fraud methods, see our HPLC-DAD Forensic Audit Guide.
Identity — Confirming You Are Buying What You Think You Are Buying
1.1 Botanical Identity Declaration
The CoA must state the full Latin binomial: Camellia sinensis (L.) Kuntze, with plant part (leaf) and variety specified. If the CoA states only "Green Tea Extract" without botanical source information, it is non-compliant with USP General Chapter ⟨561⟩ Articles of Botanical Origin.
1.2 Country of Origin and Harvest Season
Country of origin matters for heavy metal baseline risk, pesticide residue profiles, and catechin composition. Spring harvest material from Zhejiang typically yields higher EGCG proportions than summer or autumn harvest. If country of origin is omitted, geochemical contaminant risk cannot be assessed.
1.3 Extraction Ratio and Solvent Declaration
The CoA should state the extraction ratio (e.g., 10:1) and all extraction solvents. If the supplier declares their process "proprietary," ask specifically whether any ICH Q3C Class 2 solvents — toluene, dichloromethane, methanol — were used at any stage. Refusal to answer is a disqualifying signal.
Section 2Purity and Assay — The Numbers That Define What You Are Paying For
2.1 The Purity Calculation Method
This is where the majority of green tea extract CoA fraud is embedded and invisible unless you know to look for it. "98% EGCG purity" can mean three fundamentally different things:
| Calculation Method | What Is Measured | Typical Result | Honest? |
|---|---|---|---|
| Total catechins as EGCG equivalents | Sum of all catechin peaks as single value | 96-99% | ❌ Misleading |
| Single-compound EGCG, as-is basis | EGCG area / total area, no moisture correction | 88-94% | ✅ Honest |
| Single-compound EGCG, anhydrous basis | EGCG area / total area, moisture-corrected | 92-98% | ✅ Pharmacopeial Standard |
❌ Critical — Method Must Be Explicitly Stated
The CoA must state: "EGCG assay: X.X% (single-compound EGCG, anhydrous basis, by HPLC per USP ⟨561⟩)." If it states only "EGCG: 98%" without method qualification, it is an unverifiable number. This is individually disqualifying.
2.2 HPLC Method Parameters
| Parameter | Required Information | Red Flag |
|---|---|---|
| Column | Manufacturer, model, 250 × 4.6 mm, ≤ 5 µm particle size | "C18 column" with no detail |
| Mobile phase | Exact composition (e.g., acetonitrile / 0.1% phosphoric acid) | "Acetonitrile/water" without modifier |
| Gradient | Full table with all time points and %B values | "Gradient" with no table |
| Runtime | Total minutes. If < 25 min apply maximum scrutiny | Not stated |
| Detection | Wavelength AND type (UV or DAD) | "UV 280 nm" without specifying type |
| Column temperature | °C (typically 30°C ± 1°C) | Not stated |
| Injection volume | µL | Not stated |
2.3 System Suitability — The Quality Control of the Quality Control
Per USP ⟨621⟩ Chromatography, system suitability parameters must be determined and met before any sample analysis is reported.
| Parameter | Required Value | What It Proves |
|---|---|---|
| Resolution (Rs) EGCG/GCG | ≥ 2.0 — Non-negotiable | GCG is fully separated and not co-counted as EGCG |
| Theoretical plates (N) | ≥ 10,000 for EGCG peak | Column generates sufficient efficiency |
| Tailing factor (T) | 0.8-1.5 for EGCG peak | Symmetrical peak shape, no column degradation |
| %RSD of replicates | ≤ 2.0% (n ≥ 5) | Instrument precision within control |
| Reference standard lot | USP CRS lot number or equivalent | Quantification traceable to certified standard |
⚠️ Rs Is the Single Most Important Number on Any EGCG CoA
If Rs is not on the CoA, the EGCG/GCG pair was not resolved. If Rs < 2.0, GCG is partially or fully co-counted as EGCG — inflating purity by 2-8%. A CoA without this value is analytically unvalidated regardless of what purity number it reports.
2.4 Individual Catechin Quantification — The Fingerprint That Exposes Fraud
| Catechin | Expected Range in 98% EGCG | Concern If... |
|---|---|---|
| EGCG | 95.0-98.5% | > 99.5% → suspect spiking or synthetic material |
| GCG | 0.3-2.0% | = 0.0% → method cannot resolve epimers. Disqualifying. |
| ECG | 0.2-1.5% | = 0.0% → suspect method or authenticity issue |
| EGC | 0.1-0.8% | = 0.0% → same concern as ECG |
| EC | < 0.3% | Absence alone not conclusive |
| Caffeine | < 0.5% | > 1.0% → incomplete decaffeination or exogenous addition |
Under EU Regulation 2022/2340, the 800 mg daily catechin limit applies to ALL catechins combined. A supplier who reports only EGCG provides analytically insufficient data for EU compliance calculation.
2.5 Moisture / Loss on Drying
A sample with 5% moisture reporting "98% EGCG" is only 93.1% on an anhydrous basis. Without moisture data, the purity basis is unverifiable. Expected LOD for properly dried and packaged 98% EGCG: ≤ 4.0%. Chen et al. (2001, DOI: 10.1021/jf000970h) demonstrated solid-state EGCG with > 4% moisture undergoes measurable epimerization at 25°C within 90 days.
Section 3Contaminant Testing — The Compliance Layer Most CoAs Fail
3.1 Heavy Metals — Total vs. Speciated
🔬 The Total Arsenic Problem
EU Regulation 2023/915 enforces limits for inorganic arsenic (iAs: As³⁺ + As⁵⁺) — the IARC Group 1 carcinogenic fraction — not total arsenic. A sample reporting "Total As = 0.8 ppm" could contain iAs at 0.05 ppm or 0.6 ppm. Standard ICP-MS cannot distinguish them. Speciation requires HPLC-ICP-MS or HG-AAS per EN 16802:2016.
| Metal | Required Test | Required Method | Insufficient |
|---|---|---|---|
| Arsenic (inorganic) | iAs by speciation | HPLC-ICP-MS or HG-AAS per EN 16802 | "Total As" by ICP-MS |
| Lead (Pb) | Pb by ICP-MS, LOQ ≤ 0.05 ppm | ICP-MS per USP ⟨2232⟩ | "Heavy metals < 10 ppm" by USP ⟨231⟩ |
| Cadmium (Cd) | Cd by ICP-MS | USP ⟨2232⟩ | Absent from CoA |
| Mercury (Hg) | Hg by CV-AAS or ICP-MS | USP ⟨2232⟩ | Absent from CoA |
⚠️ California Proposition 65 Lead Risk
The Prop 65 MADL for lead (reproductive toxicity) is 0.5 µg/day. Green tea extract at 0.8 ppm lead with a 600 mg daily serving delivers 0.48 µg lead/day — 96% of the MADL. One batch at 0.9 ppm (still USP-compliant) crosses the line. Settlement demands: $50,000-150,000. Semi-quantitative USP ⟨231⟩ testing cannot detect at this resolution. Demand quantitative ICP-MS with LOQ ≤ 0.05 ppm plus a MADL calculation at your serving size.
3.2 Residual Solvents — ICH Q3C Classification
| ICH Class | Key Solvents in EGCG Processing | Limit | Method |
|---|---|---|---|
| Class 2 — Limit Tightly | Toluene (PDE 8.9 mg/day), DCM (PDE 6.0 mg/day), Methanol (PDE 30 mg/day) | Per ICH Q3C Table 1 | GC-FID or GC-MS per USP ⟨467⟩ |
| Class 3 — Preferred | Ethyl acetate, Ethanol, n-Heptane, Acetone | ≤ 5,000 ppm each | GC-FID per USP ⟨467⟩ |
3.3 Microbiological Panel
| Test | Acceptable Limit | Why It Matters |
|---|---|---|
| Total aerobic plate count (TPC) | ≤ 10,000 CFU/g | General microbial load indicator |
| Total yeast and mold | ≤ 1,000 CFU/g | Mold can produce mycotoxins |
| Escherichia coli | Absent / 10g | Fecal contamination indicator |
| Salmonella spp. | Absent / 25g | USP ⟨2021⟩ and EU Reg 2073/2005 |
| Staphylococcus aureus | Absent/g or < 100 CFU/g | Toxin-producing pathogen |
| Pseudomonas aeruginosa | Absent/g | Required for immunocompromised populations |
Stability, Shelf Life, and Storage — The Time Dimension of Quality
4.1 Manufacturing Date vs. Repackaging Date vs. CoA Issue Date
| Date Type | What It Means | Validity |
|---|---|---|
| Manufacturing date | When the EGCG powder was produced and dried | ✅ Essential — epimerization clock starts here |
| Repackaging date | When a distributor transferred from bulk drum to smaller units | ❌ Irrelevant to stability |
| CoA issue date | When the laboratory generated the PDF document | ⚠️ Only valid for the sample tested on that date |
Wang et al. (2008, DOI: 10.1021/jf0730338) established the EGCG epimerization activation energy at 93.7 kJ/mol. At 25°C/60% RH, a 98% EGCG batch loses approximately 3.5% purity over 12 months. A supplier who cannot provide the exact manufacturing date is hiding how old the material is.
4.2 ICH Q1A Stability Data and Storage Conditions
A "shelf life: 24 months" claim on a CoA without supporting ICH Q1A stability data is an assertion without evidence. Stability data must be generated under:
- Accelerated conditions: 40°C ± 2°C / 75% RH ± 5%, for 6 months
- Long-term conditions: 25°C ± 2°C / 60% RH ± 5%, for 36 months
Storage conditions on the CoA must be quantitative: temperature in °C and humidity in %RH. "Store in a cool, dry place" is unenforceable and non-compliant with pharmacopeial standards.
Section 5Regulatory Compliance Documentation
5.1 EU Regulation 2022/2340 Compliance Statement
For green tea extract intended for EU food supplement markets, the CoA package must include documentation confirming compliance with EU Regulation 2022/2340 — specifically individual catechin breakdown data enabling calculation of total daily catechin exposure at the intended serving size against the 800 mg limit. If a supplier cannot provide catechin speciation data, they are not equipped to support EU market entry.
5.2 GMP Certificate Verification
The CoA must be issued on letterhead identifying the manufacturing site — not a trading company or distributor. The GMP certificate must include: issuing body, certificate number, scope of certification, and expiry date. "GMP certified" without these details is unverifiable.
5.3 FDA 21 CFR Part 111 Identity Testing
Under 21 CFR Part 111.75, dietary supplement manufacturers must verify incoming component identity using at least one specific test before use. Filing a supplier's CoA without independent verification does not satisfy this requirement. Reliance on an unverified CoA is a Form 483 observation waiting to happen.
Master ChecklistThe 30-Point CoA Audit — Binary Pass/Fail
Any single failure on items 4, 10, 15, 21, or 22 is individually disqualifying regardless of total score.
| # | Check Item | Pass Criteria | Action if Fail |
|---|---|---|---|
| Section 1 — Identity | |||
| 1 | Latin binomial and plant part stated | Camellia sinensis (L.) Kuntze, leaf | Request corrected CoA |
| 2 | Country of origin stated | Specific country and province | Request clarification |
| 3 | Extraction solvents disclosed | Solvents named by ICH class | Request SOP disclosure |
| Section 2 — Purity and Assay | |||
| 4 ★ | Purity calculation method stated | "Single-compound EGCG, anhydrous basis, HPLC per USP ⟨561⟩" | ❌ Individually disqualifying |
| 5 | HPLC column fully specified | Manufacturer, dimensions, particle size ≤ 5 µm | Request full method |
| 6 | Mobile phase composition stated | Full composition with concentrations | Request full method |
| 7 | Gradient table provided | All time points and %B values | Request full method |
| 8 | Runtime ≥ 25 minutes | Yes | Apply heightened scrutiny |
| 9 | Detection type stated | HPLC-DAD preferred; UV with DAD purity data acceptable | Request DAD peak purity |
| 10 ★ | System suitability: Rs EGCG/GCG ≥ 2.0 | ≥ 2.0 per USP ⟨621⟩ | ❌ Individually disqualifying — CoA is invalid |
| 11 | System suitability: N (plates) ≥ 10,000 | ≥ 10,000 for EGCG peak | Request column specification |
| 12 | System suitability: Tailing factor 0.8-1.5 | 0.8-1.5 | Investigate column condition |
| 13 | System suitability: %RSD ≤ 2.0% | ≤ 2.0% (n ≥ 5) | Request raw injection data |
| 14 | Reference standard lot number | USP CRS lot or equivalent | Request standard certificate |
| 15 ★ | GCG explicitly quantified with numerical value | Numerical value, typical 0.3-2.0% | ❌ Individually disqualifying — Not Detected is invalid |
| 16 | EGC quantified | Numerical value, typical 0.1-0.8% | Suspect method or authenticity |
| 17 | ECG quantified | Numerical value, typical 0.2-1.5% | Same concern |
| 18 | EC quantified | Numerical value, typical < 0.3% | Same concern |
| 19 | Caffeine quantified | < 0.5% for 98% EGCG | > 1.0% requires explanation |
| 20 | Moisture / LOD reported | ≤ 4.0% with method stated | Request Karl Fischer data |
| Section 3 — Contaminants | |||
| 21 ★ | Inorganic arsenic speciation | iAs by HPLC-ICP-MS or HG-AAS | ❌ Individually disqualifying for EU markets |
| 22 ★ | Lead by quantitative ICP-MS | Pb in ppm, LOQ ≤ 0.05 ppm | ❌ Individually disqualifying for CA market |
| 23 | Cadmium and Mercury quantified | Both by ICP-MS per USP ⟨2232⟩ | Request complete heavy metal panel |
| 24 | Residual solvents panel | GC-FID/MS per USP ⟨467⟩, Class 2 < limits | No data = cannot verify solvent safety |
| 25 | Pathogen testing: Salmonella, E. coli, S. aureus | Each individually tested and reported | TPC only = incomplete |
| 26 | Pesticide residue framework stated | EU MRLs or USP ⟨561⟩, specific substances listed | "Compliant" alone = not a result |
| Section 4 — Stability and Logistics | |||
| 27 | Manufacturing date (exact) | Exact date, not best-before or CoA issue date | Demand in writing before PO |
| 28 | ICH Q1A stability data on file | Accelerated (40°C/75% RH) + long-term (25°C/60% RH) | 24-month claim without data = unsupported |
| 29 | Storage conditions quantitative | °C and %RH specified | "Cool dry place" = unenforceable |
| Section 5 — Regulatory | |||
| 30 | GMP certificate verifiable | Issuing body, number, scope, expiry date | "GMP certified" alone = unverifiable |
★ Items marked with star are individually disqualifying regardless of total score.
Blue Eye Biotech StandardWhat Blue Eye Biotech Co., Ltd. Provides as Standard
✅ All 30 Items — Included on Every Batch Including 500g Trial Orders
The 30-point checklist above was built from Blue Eye Biotech Co., Ltd.'s own internal QC standard. We publish it because we are confident every batch we ship passes it — and because publishing it accelerates the elimination of suppliers who cannot.
| Documentation Item | Generic CoA (Legacy Supplier) | Blueeyes Bio Standard CoA |
|---|---|---|
| Purity calculation method | ❌ "Purity: 98%" | ✅ Single-compound EGCG, anhydrous basis, per USP ⟨561⟩ |
| HPLC-DAD chromatogram | ❌ Rarely provided | ✅ Full chromatogram with integration markers |
| System suitability (Rs, N, T, %RSD) | ❌ Never provided | ✅ Rs ≥ 2.0, N ≥ 10,000, T 0.8-1.5, %RSD ≤ 1.5% |
| DAD peak purity index | ❌ UV only | ✅ Peak purity index > 0.9990 |
| GCG quantified | ❌ Absent or Not Detected | ✅ Numerical value per batch (typical 0.3-1.0%) |
| Six-catechin profile | ❌ EGCG only | ✅ EGCG, GCG, EGC, ECG, EC, caffeine — all quantified |
| Inorganic arsenic speciation | ❌ "Total As < 1 ppm" | ✅ iAs by HPLC-ICP-MS, LOQ 0.02 ppm |
| Lead with Prop 65 MADL calculation | ❌ "Heavy metals < 10 ppm" | ✅ Pb by ICP-MS (LOQ 0.02 ppm), MADL calc at your serving size |
| Residual solvents | ❌ Not tested or not disclosed | ✅ GC-FID per USP ⟨467⟩, Class 3 only, Class 2 < LOD |
| Raw chromatographic data files | ❌ Never | ✅ .lcd / .cdf available on request |
| Manufacturing date | ❌ "Best before 2028" | ✅ Exact date, typically < 30 days from dispatch |
| EU 2022/2340 compliance documentation | ❌ Not provided | ✅ Pre-formatted, English and German |
| German BfR-aligned label templates | ❌ Not provided | ✅ Hepatotoxicity warnings, take with meals advisory |
Run the Checklist on Your Current Supplier — Then Compare
Request a sample CoA package from Blue Eye Biotech Co., Ltd. and apply the 30-point audit. Every item passes. 500g minimum order. DDP air freight to US, EU, UK, Singapore, Thailand. 28-40 days manufacturing to delivery.
References
- Wang R, Zhou W, Jiang X. Reaction Kinetics of Degradation and Epimerization of Epigallocatechin Gallate (EGCG). J Agric Food Chem. 2008;56(8):2694-2701. DOI: 10.1021/jf0730338
- Chen ZY et al. Stabilizing Effect of Ascorbic Acid on Green Tea Catechins. J Agric Food Chem. 2001;49(1):477-482. DOI: 10.1021/jf000970h
- European Commission. Commission Regulation (EU) 2022/2340 of 30 November 2022. EUR-Lex Full Text
- European Commission. Commission Regulation (EU) 2023/915 of 25 April 2023. EUR-Lex Full Text
- U.S. FDA. Import Alert Database. FDA.gov
- U.S. FDA. New Dietary Ingredient Notifications — Guidance for Industry. FDA.gov
- United States Pharmacopeia. General Chapters: ⟨561⟩ Articles of Botanical Origin; ⟨621⟩ Chromatography; ⟨2232⟩ Elemental Contaminants; ⟨467⟩ Residual Solvents.
- European Pharmacopoeia. Monograph 2799 Green Tea Extract Refined and Standardised; Section 2.2.29 Liquid Chromatography.
- ICH Q3C(R8): Guideline for Residual Solvents. ICH Q1A(R2): Stability Testing.
- EFSA Panel on Food Additives and Nutrient Sources. Scientific Opinion on Green Tea Catechins. EFSA Journal. 2018;16(4):5239.
