PBTC, ATMP and HEDP: a procurement comparison

Use the following current manufacturer TDS references to compare chemical identity, covered form and content-reporting basis. Document and grade differences do not establish interchangeable application performance. These are screening references, not a ranking of treatment performance or confirmation of supply.

PBTC — liquid acid reference

Identity: 2-phosphonobutane-1,2,4-tricarboxylic acid, CAS 37971-36-1.
Covered form and content: liquid, 49.0–51.0% active acid.
Do not assume: this liquid-acid reference defines a salt grade or establishes equivalence to ATMP or HEDP in your application.
Review: PBTC specifications · PBTC liquid TDS (PDF) · PBTC supply-inquiry requirements.

ATMP — liquid acid reference

Identity: amino tri(methylene phosphonic acid), CAS 6419-19-8.
Covered form and content: liquid, 48.0–52.0% active acid.
Do not assume: these limits cover ATMP crystal powder or a sodium salt. A similar active-acid percentage to PBTC does not establish the same chemical identity or application performance.
Review: ATMP specifications · ATMP liquid TDS (PDF) · ATMP supply-inquiry requirements.

HEDP — separate liquid and powder references

Identity: 1-hydroxyethylidene-1,1-diphosphonic acid, CAS 2809-21-4.
Covered forms and content: liquid, at least 60.0% active acid; crystal powder, at least 98.0% as HEDP·H₂O on a monohydrate basis.
Do not assume: 98.0% monohydrate means 98.0% active acid, that liquid limits apply to powder, or that earlier catalogue grades add guarantees to the current TDS.
Review: HEDP grade specifications · HEDP liquid TDS (PDF) · HEDP powder TDS (PDF) · HEDP supply-inquiry requirements.

Confirm the identity

An acid and its salt forms may have different properties and requirements. Product names, CAS numbers and supplied forms should agree across the documents. HEDP acid, for example, should not be treated as interchangeable with its sodium salts.

Compare the reporting basis

The current manufacturer TDS for HEDP crystal powder specifies at least 98% on an HEDP monohydrate basis. An earlier catalogue separately listed at least 90% active acid. The current TDS does not repeat that separate active-acid guarantee; do not combine the two sources into a new specification, or relabel 98% monohydrate as 98% active acid. Compare HEDP specifications by grade.

Keep measurement conditions attached

The PBTC reference pH range of 1.5–2.0 applies to a 1% solution, while its density minimum of 1.270 g/cm³ is specified at 20°C. The QSY3100 reference gives pH for the undiluted product. A value without its test conditions is an incomplete comparison. Review PBTC specifications.

Compare impurity limits by grade

The earlier HEDP catalogue low-arsenic reference adds an arsenic maximum; its separate low-heavy-metal reference lists copper, cobalt, titanium and lead limits. These are retained as catalogue references and require a current grade specification before purchase. Do not combine the two tables into an unsupported all-purpose grade. A blank or dash in a source table does not mean zero.

Distinguish active acid, active component and solids

The PBTC and ATMP references report active acid, PAPEMP reports active component, and the polymer references report solids content. Preserve the named test and reporting basis when comparing supplier documents. Review PAPEMP or PAA / QSYW1000.

Check packaging and storage separately

A 1000 L IBC describes container volume; it does not establish a fixed net shipment weight. Confirm fill weight, grade and package on the quotation. Storage periods also vary: the reference sheets list 10 months for PAPEMP, HPAA and QSY3100, while PBTC and ATMP list 12 months under the stated storage conditions.

Validate in your process

A matching specification is one part of qualification. Evaluate the selected grade in your formulation and operating conditions, using agreed performance criteria. Manufacturer-reference tables support screening and do not replace your application tests.

Keep the evidence together

Use the current grade-specific TDS. Obtain the applicable SDS from H2Q for your product, destination and qualification requirements. Compare the relevant shipment COA with the agreed specification; a historical batch result is not a promise for a future shipment. Record the product, method, limits, batch and any approved commercial specification together.