Lignosulfonate is tested for identity, composition and performance. Routine quality checks cover dry matter, lignosulfonate content, pH, water-insoluble matter, ash, sulphate, reducing sugars and the cation (calcium, sodium, magnesium). Identity is confirmed by UV absorption at about 280 nm and by infrared spectrum; food-grade material is also tested for molecular weight, degree of sulfonation and heavy metals.
Routine Quality Tests
| Test | What it tells you | Typical principle |
|---|---|---|
| Dry matter / moisture | Water content; powder grades are usually ≤5–8% moisture | Oven drying to constant weight (JECFA loss on drying: 105 °C, 24 h) |
| Lignosulphonate content | How much of the solids is active polymer | UV absorbance of a diluted solution against a reference, or gravimetric methods |
| pH | Acidity of a defined solution (often 10%) | pH meter |
| Water-insoluble matter | Undissolved residue such as fibre or salts | Filtration and drying of residue |
| Ash | Inorganic content including the cation | Ignition in a furnace |
| Sulphate | Inorganic sulfate from pulping chemicals | Gravimetric (barium sulfate) or ion chromatography |
| Reducing sugars | Residual wood sugars; affects setting and feed limits | Copper-reduction method or chromatography |
| Calcium, magnesium, sodium | Confirms the cation and hardness | Titration (EDTA), AAS or ICP |
Identity Tests
| Test | JECFA criterion for calcium lignosulfonate (40-65) |
|---|---|
| UV spectrum | Absorption maximum at 280 nm in a diluted solution adjusted to pH 2.0–2.2 |
| IR spectrum | Characteristic absorptions at 1210–1220, 1037 and 655 cm-1 |
| Solubility | Soluble in water, practically insoluble in organic solvents |
| pH | 2.7–3.3 (10% solution) |
| Weight-average molecular weight | 40,000–65,000 by SEC with light scattering |
| Degree of sulfonation | 0.3–0.7 (organic sulfur to methoxyl) |
Purity Tests for Food and Feed
| Parameter | JECFA calcium lignosulfonate (40-65) | Typical feed-grade data sheet |
|---|---|---|
| Reducing sugars | ≤5.0% (dry basis) | EU 1g565: ≤20% (dry matter) |
| Total ash | ≤14.0% (dry basis) | Stated on TDS |
| Lead | ≤2 mg/kg | For example ≤0.5 mg/kg (GAC-CaLS-Feed TDS) |
| Arsenic | ≤1 mg/kg | For example inorganic As ≤0.1 mg/kg (GAC-CaLS-Feed TDS) |
| Sulfite | ≤0.5% (dry basis) | — |
Performance Tests by Application
| Application | Common performance test |
|---|---|
| Concrete | Water reduction and setting time against a reference mix; mortar or concrete flow |
| Dye and pigment dispersion | Dispersion and filter tests, heat stability (for disperse dyes, e.g. GB/T 5541 double-filter-paper test) |
| Agrochemicals | Suspensibility and dispersibility (CIPAC MT 184, MT 174) |
| Feed pellets | Pellet durability index (ASAE S269 tumbling box, or Holmen tester) |
| Drilling fluids | Rheology (yield point, gel strength) and filtrate loss of a test mud |
| Binders | Green and dry strength of test pellets or briquettes |
Reading Results Correctly
- Check the basis: “dry basis” and “as is” values differ by the moisture content.
- Compare methods: lignosulfonate content and sugars depend strongly on the method used.
- A TDS gives typical values; the COA gives batch results. Agree which values are the contract specification.
Frequently Asked Questions
How is lignosulfonate content measured?
Most often by UV absorbance of a diluted solution at around 280 nm against a reference material. Because the result depends on the reference, values from different methods should not be compared directly.
What tests confirm that a product is lignosulfonate?
A UV maximum near 280 nm, characteristic infrared absorptions (JECFA lists 1210–1220, 1037 and 655 cm-1), water solubility and insolubility in organic solvents.
Which tests matter for concrete use?
Reducing sugars, water reduction and setting time in a trial mix, because sugars and low-molecular-weight fractions retard cement.
References
- FAO/WHO JECFA, Calcium lignosulfonate (40-65), specifications prepared at the 69th JECFA (2008), FAO JECFA Monographs 5
- Commission Implementing Regulation (EU) 2024/749 (lignosulphonate as a feed additive, identification number 1g565)
Related Pages
Questions about a specification, a test method or a trial: contact us or email info@greenagrochem.com.
