ASDA-Na4 Purchase Specification and Acceptance Checklist

Tetrasodium aspartate diacetate is a different purchase from the commodity chelants most buyers know. It is an amino-acid-derived, readily biodegradable molecule with a moderate affinity for calcium and magnesium and a useful selectivity for iron. The properties that make it worth specifying are also the properties a loose specification can hide. This article is written for procurement and quality staff at European formulators and mills who buy ASDA-Na4: what belongs in the specification, what the certificate of analysis should prove, and how to check a delivery before it enters production.

What the molecule is, in procurement terms

ASDA-Na4 is the tetrasodium salt of aspartic acid diacetic acid, supplied most often as an aqueous solution with a smaller spray-dried or granulated solid grade. The number that fixes identity is the CAS reference for tetrasodium aspartate diacetate; put it in the specification so that a substitution with a different salt, a partial EDTA blend, or a diluted product cannot slip through under the same name.

Form changes handling. A solution simplifies a liquid line but adds freight weight and freeze risk in a cold warehouse; a solid suits dry blends but must redisperse without lumps. State the form you expect, because the form changes the storage rules and the active-content basis you should quote against.

The specification lines that actually matter

A useful ASDA-Na4 specification runs further than active content. The lines below are the ones that decide whether a drum behaves in your process.

Parameter	What to request	Why it matters
Identity	CAS for tetrasodium aspartate diacetate	Stops grade substitution
Active content	Typical 38 to 47% as supplied; also per g active	Drives dose and cost
Appearance	Clear to pale liquid or free-flowing solid	First sign of degradation or contamination
pH (as supplied)	Within a stated band	Affects tank, pump and seal choice
Density	At a stated temperature	Needed for volume dosing
Colour	Gardner or APHA number	Tracks oxidation and residual feedstock
Iron	Low ppm limit	This is the metal ASDA must control
Residual intermediates	Limit by named method	Unreacted feedstock affects stability
Biodegradability	OECD 301 result or equivalent	Required for Ecolabel and green-claim support

Set the band, not just the typical value. A supplier can meet a typical figure while drifting across the tolerance every other batch; the band is what protects your line.

Active content: quote against the right basis

Active content is the line most often misread on a quote. A 47% solution and a 38% solution of the same salt are not interchangeable, and the gap is larger than the nine points suggests once you work it through to cost per kilogramme of active material.

Always state whether the figure is as supplied or per gram of active. Per gram of active is the honest basis for dose calculation, because your process cares about the chelant, not the water it arrived in. If a quote gives only as-supplied, convert it before comparing, and keep the conversion in the specification file so two buyers in two years read the same number.

Residual intermediates are the part suppliers skip

ASDA-Na4 is made by reacting aspartic acid with a chloroacetate or a related intermediate. Some unreacted intermediate in the finished product is normal; an uncontrolled amount is not. Residual chloroacetate in particular affects both stability and the toxicological profile you will defend to a customer.

Name the method in the specification. "Residual intermediates: limited" is not a specification; "residual chloroacetate: < X mg/kg by [named method]" is. Ask the supplier which method they use, and whether the limit is measured on every batch or only on a development sample. A limit that is never measured is a line on paper.

What the certificate of analysis should prove

A CoA is only as good as the methods behind it. Before you approve a supplier, read the CoA against these points:

• Methods are named, not implied. A value with no method cannot be audited and cannot be repeated when a batch misbehaves.

• Iron is reported, not assumed. ASDA-Na4 is bought partly for iron control; a CoA that omits iron tells you nothing about the property you paid for.

• The biodegradability claim has a test, not a slogan. OECD 301 (or an accepted equivalent) with a pass level is evidence; "readily biodegradable" printed on a cover sheet is marketing.

• The batch number ties to a retained sample. If a drum fails six months later, you need to trace it to the same lot the CoA describes.

Keep one approved CoA per grade as your reference, and treat any change in method or supplier site as a re-approval trigger.

Five traps in an ASDA-Na4 quote

1. As-supplied versus per-active confusion. Covered above; it is the most common way a cheap quote becomes an expensive one.

1. Undisclosed blend. A product labelled ASDA-Na4 that contains EDTA or citrate to hit a price is still sold under the ASDA name. Require the identity line and a heavy-metal profile that would expose a blend.

1. Freight quoted separately, late. Solution freight by sea is a real cost; a quote that hides it until after the order lands shifts the true cost to your landed price.

1. Freeze damage not covered. Solution that froze in transit can partial-crystallise; ask who owns the risk and what the acceptance window is on arrival.

1. No retest date. Without a retest date you cannot plan incoming inspection, and a drum at the back of the warehouse becomes an unknown.

How to check a delivery in five steps

A receiving check need not be slow to be useful. The steps below catch most of the failures that matter:

1. Match the documents. Batch number, CoA, and SDS agree, and the CAS on the CoA is the one in your specification.

1. Look at it. Colour, clarity and any sediment against the agreed appearance. A drawn sample in a clear jar beats a glance at the drum.

1. Check pH and density against the band, at the temperature stated on the CoA.

1. Run one confirmation test you trust — active content or iron by your own or a contract lab — on the first lot from any new supplier, then on a frequency you set.

1. Quarantine until cleared. Do not release to production on the lorry's paperwork alone. A short hold costs less than a line stoppage.

Questions to put to a supplier before you commit

• Which manufacturing route is used, and does it leave chloroacetate above your limit?

• Is the iron content measured on every batch, and at what detection level?

• What is the retest period, and what storage temperature keeps the product inside it?

• Can the supplier hold a second manufacturing site or a documented backup, so a single plant stoppage does not stop your line?

• What is the standard lead time to a named European port, and what packaging is available?

A second source is not only a commercial hedge. A second molecule that covers the same failure mode is a stronger one, because it protects against a raw-material shortage rather than only a supplier's calendar.

Frequently asked questions

Is ASDA-Na4 a drop-in replacement for EDTA? Not in most cases. It degrades more readily and is gentler on calcium and magnesium, so dose and co-builder choices usually change. Treat it as a reformulation, not a swap, and screen it in your own matrix.

What active-content basis should I quote against? Per gram of active, because that is what your dose maths uses. Keep the as-supplied figure for logistics and the per-active figure for formulation and cost.

How do I confirm biodegradability for a customer claim? Ask for the OECD 301 test report with the pass level and the exact test variant. A summary sentence on a data sheet is not enough when a retailer or a regulator asks.

Does the form I choose affect acceptance testing? Yes. A solution is checked by pH, density and clarity; a solid adds redispersibility and a moisture check. Write the form into the specification so the test plan matches the product.

What is the single most useful line to add to my spec? The identity CAS and the residual-intermediate limit by named method. Those two stop substitution and the failure mode suppliers are most likely to under-report.

Procurement decisions on amino-acid chelants are won on the specification, not the headline price. A short, well-chosen list of parameters — identity, active basis, iron, residual intermediates, biodegradability — protects your line and gives your supplier a clear target. For the application side, including water treatment, detergents and concrete retarding, see the technical notes on Yuanlian's chelation site, and contact Yuanlian Chemical for a current specification and sample.