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Amino Acid Fertilizer Specifications: Compare the Assay Basis
Compare powder percentages and liquid g/L without confusing total,free,dry-basis and supplied-material results.
A higher-looking amino-acid number is not automatically a more concentrated or more suitable fertilizer raw material. Before comparing quotations, identify what was measured, the unit and the supplied-material basis. A powder percentage and a liquid concentration in g/L cannot be ranked by reading their numbers alone.
Two real MOS catalogue routes illustrate the purchasing problem: 40% amino-acid powder and enzymatic amino-acid liquid. They provide source labels to clarify, not a controlled efficacy comparison. Keep each original specification and its preparation conditions attached to the enquiry.
Start with what the number actually measures
| Catalogue field | 40% powder source | Enzymatic liquid source | What remains to confirm |
|---|---|---|---|
| Total amino acids | ≥40% | ≥500 g/L | Analyte list, preparation, method and reporting basis |
| Free amino acids | ≥20% | 2–3% | Meaning of the percentage and whether methods are comparable |
| pH | 4–6 at 1% aqueous preparation | 4–6 at 1:10 dilution | Exact preparation and agreed comparison method |
| Density for mass conversion | Not a liquid conversion input | Not supplied in the reviewed specification | Measured density and temperature if a mass fraction is needed |
These are catalogue declarations, not today's lot results. The liquid's product name includes “50%”, but its reviewed total-amino-acid row is expressed as g/L. Do not silently replace that row with a mass-percentage claim. Likewise, ask whether powder percentages refer to supplied material or a dry basis; the answer changes a like-for-like comparison.
Convert volume to mass only with a valid density
For a liquid concentration C in g/L and density ρ in kg/L, the corresponding mass percentage is C ÷ (10 × ρ). The concentration and density must describe the same material under stated conditions. A density copied from another grade cannot resolve an incomplete COA.
For illustration only, suppose a sample measured exactly 500 g/L and had a measured density of 1.20 kg/L at the agreed temperature. One litre would contain 0.500 kg of the reported amino acids in 1.20 kg of solution: approximately 41.7% by mass. Those are hypothetical inputs, not a MOS batch measurement, a supplier density or a conversion of the catalogue's minimum into an actual assay.
Use a common basis before comparing cost per reported kilogram of amino acids. Even a correct calculation does not make different analytical definitions interchangeable. It also excludes other commercial and formulation factors unless those have been explicitly accounted for.
Free and total are analytical questions
“Free” and “total” need their method definitions. Free-amino-acid analysis generally concerns an extracted free fraction; a total result may involve hydrolysis and a defined analyte sum. Preparation can change what is reported. Do not subtract two unmatched results and label the difference a verified peptide content, or assume that a higher free fraction proves better field performance.
The public scope of ISO/DIS 25300 concerns free amino acids in fertilizers and identifies analytical approaches. It is a draft project, not proof that either MOS product was tested by it. The EU feed-analysis text separately describes free and total preparations within its own feed scope; that distinction is useful analytical context, not automatic approval of a feed method for these fertilizer matrices.
Ask the laboratory or supplier for sample preparation, hydrolysis where applicable, amino acids included or excluded, calibration and reporting basis. The practical objective is a method suitable for the actual matrix and purchasing specification, not merely a method name on a quotation.
Keep pH and the application trial on their own basis
Both catalogue pH ranges read 4–6, but the listed preparations differ. That does not establish equal concentrate acidity, buffer capacity or behaviour in a final fertilizer blend. Preserve 1% versus 1:10 and agree a common procedure if pH is a comparison criterion.
Incoming composition and application suitability are separate decisions. A representative formulation may still need compatibility, filtration, storage and intended-use evaluation. None of the quoted amino-acid thresholds establishes a universal crop dose, yield increase, organic approval or superiority of powder over liquid.
Make the quotation technically comparable
For the powder or enzymatic liquid, request a current lot COA with total/free definitions, units and methods. Specify the intended formulation and the sample acceptance plan; include density only where a liquid mass conversion is required. Add quantity, packaging and destination.