CAS: 7758-29-4
Core COA anchors: Assay • P2O5 • pH (1%)
Common audit fields: Lot • Methods • Limits
Scope note: Acceptance criteria should be defined by the destination market and the applicable standard. “Typical” values are reference ranges only.
Quick Answer
An STPP COA should confirm product identity (Na5P3O10, CAS 7758-29-4), grade (food vs industrial),
and traceability (batch/lot, dates, methods/standard). Most buyers first verify three numeric anchors:
assay (commonly ≥94.0%), P2O5 (commonly 57.0–59.0%), and
pH of 1% solution (commonly 9.5–10.0). Then check handling and quality indicators such as
moisture (often ≤0.5%) and water-insoluble matter (often ≤0.1%). For food-grade procurement, the COA should report
impurity controls (e.g., Pb, As, fluoride) required by the applicable standard.
Definition
A Certificate of Analysis (COA) is a batch-specific report listing measured test results for a product against specification limits.
For STPP, the COA commonly includes assay, P2O5, pH (1% solution), plus impurity and handling parameters
(e.g., insolubles, moisture, heavy metals) under a referenced standard and test method.
Operating or Technical Mechanism
1) The COA anchors correlate with functional phosphate content and alkalinity
Assay and P2O5 indicate effective phosphate content, while pH (1% solution) indicates alkalinity. Together they are used to screen batch-to-batch consistency for chelation and dispersion-related performance.
2) Handling parameters affect the effective concentration in use
Moisture influences caking and flowability; water-insoluble matter influences residue and haze risk. These values can affect dosing accuracy and process stability.
3) Impurity parameters define compliance suitability
For regulated uses, impurity items (e.g., Pb, As, fluoride) determine whether a batch meets food additive limits for the target market and category.
Required COA Fields (Minimum Set)
Minimum fields for an auditable COA:
Grade (food/industrial)
CAS / identity
Batch/Lot number
Manufacture date
Standard referenced
Test methods
Result + limit table
Unit clarity
Authorized signature
| Field | What to verify | Why it matters |
|---|---|---|
| Batch/Lot number | Present and unique | Links results to shipped material for traceability |
| Standard / methods | Listed (e.g., FCC/JECFA/GB, or supplier standard) | Ensures results are comparable and auditable |
| Results vs limits | Both values present (not results only) | Shows pass/fail basis rather than raw results |
| Units | % vs mg/kg clearly stated | Avoids interpretation errors in impurities |
| Authorized sign-off | Signature/stamp or verification method | Supports document credibility in audits |
3 Anchor Checks (Assay, P2O5, pH)
Common reference bands (examples):
- Assay (as Na5P3O10): ≥ 94.0%
- P2O5: 57.0–59.0%
- pH (1% solution): 9.5–10.0
| Anchor | What deviations can indicate | Next action |
|---|---|---|
| Assay low | Higher non-STPP salts, possible conversion differences | Confirm standard/method; verify suitability for target application |
| P2O5 out of band | Content inconsistency or different product/grade | Re-check product identity and document alignment |
| pH out of band | Alkalinity shift affecting behavior in some systems | Confirm test method (1% solution); evaluate process impact |
Impurity Items (Food-Grade Focus)
Food-grade acceptance depends on the destination market standard and product category. Below are common impurity items that may appear on a COA for regulated procurement.
| Impurity item | Typical unit | Example limit (standard-dependent) |
|---|---|---|
| Fluoride (F) | mg/kg | ≤ 50 mg/kg |
| Lead (Pb) | mg/kg | ≤ 4 mg/kg |
| Arsenic (As) | mg/kg | ≤ 3 mg/kg |
| Heavy metals (as Pb) (if used) | mg/kg | Limit varies by standard |
COA Acceptance Checklist (Copy/Paste)
Identity & traceability
- Product name matches: Sodium tripolyphosphate (STPP), Na5P3O10, CAS 7758-29-4
- Grade stated: food-grade vs industrial-grade
- Batch/Lot number present
- Manufacture date present
- Standard and/or test methods listed
- Results include spec limits (pass/fail basis)
- Units are explicit (% vs mg/kg)
- Authorized signature/stamp or verification method
Core anchors
- Assay meets acceptance band (example reference: ≥94.0%)
- P2O5 meets acceptance band (example reference: 57.0–59.0%)
- pH (1% solution) meets acceptance band (example reference: 9.5–10.0)
Handling & quality indicators
- Moisture meets acceptance band (example reference: ≤0.5%)
- Water-insoluble matter meets acceptance band (example reference: ≤0.1%)
- Particle size is stated if required by your process
Food-grade impurity items (if applicable)
- Fluoride (F) reported and within limit
- Pb and As reported and within limits
- Any additional items required by destination standard reported
Red Flags (Common COA Problems)
- No batch/lot number or mismatch with shipping documents
- No referenced methods/standard (results are not comparable)
- Results listed without limits (no pass/fail basis)
- Units missing for impurities (mg/kg vs ppm ambiguity)
- Food-grade claim without impurity items required by your standard
- COA covers a different product (e.g., SHMP/TSPP) due to template reuse
Short Practical Example
A QA reviewer receives an STPP COA intended for seafood soaking. The acceptance window is defined as:
assay ≥94.0%, P2O5 57–59%, pH (1%) 9.5–10.0,
moisture ≤0.5%, insolubles ≤0.1%, and the destination standard’s impurity requirements (Pb/As/F).
The COA is checked for lot number and referenced methods. If fluoride is not reported, the batch is placed on hold until an updated COA is provided.
FAQ
What is an STPP COA?
An STPP COA is a batch-specific report listing measured test results (e.g., assay, P2O5, pH, impurities) against specification limits under referenced methods/standard.
Which three values should be checked first?
Most buyers first check assay, P2O5, and pH (1% solution) because they screen identity and consistency quickly.
Why does the COA need a batch/lot number?
The batch/lot number links the test results to the shipped material and supports traceability for audits and claims handling.
What impurity items are common for food-grade STPP?
Food-grade COAs commonly report impurity controls such as Pb, As, and fluoride, depending on the applicable standard and destination market.
What if the COA lists results but not limits?
A COA without limits does not show pass/fail basis. For audits, request a COA format that includes both results and specification limits.
Can industrial-grade STPP be used in food applications if assay is high?
No. Food applications require impurity controls aligned to food additive standards. High assay alone does not ensure compliance.
Internal Link Suggestions
- STPP main hub (definition, uses, mechanisms)
- STPP Specification Explained (parameter meanings)
- Phosphate supplier (buyer overview)
- Food Grade STPP product page
- Industrial Grade STPP product page
This page focuses on COA verification. For parameter definitions, use the Specification Explained page; for applications and selection, use the STPP main hub.
