Overview
ISO 5510:1984 specifies a chemical method for the determination of available lysine in animal feeding stuffs. The standard covers a two-part analytical procedure: (1) hydrolysis of a ground test portion with hydrochloric acid to measure total lysine, and (2) derivatization of a second portion with 2,4-dinitrofluorobenzene (DNFB) to isolate and measure non‑available (blocked) lysine. Both lysine fractions are separated by column (ion‑exchange) chromatography and quantified by spectrometry at 570 nm; available lysine is reported as the difference between total and non‑available lysine.
Key topics and requirements
- Scope: Applies to animal feeds containing animal- or plant‑derived proteins; results are expressed as mass percent of the product as‑received.
- Principle: Acid hydrolysis for total lysine; DNFB dinitrophenylation under alkaline/ethanolic conditions to block available amino groups, then hydrolysis to quantify non‑available lysine.
- Primary reagents: DNFB in ethanol, hydrochloric acid (~6 mol/L), citrate buffer solutions (pH ~2.2 and pH ~5.28), sodium bicarbonate solution, ninhydrine reagent, lysine standard solution.
- Column chromatography: Uses a strongly acidic cation‑exchange resin (sulfonic groups); the standard specifies column dimensions and operating conditions (e.g., thermostatted column at 55 °C, typical pump flow ~50 mL/h).
- Detection: Spectrophotometric measurement at 570 nm after reaction with ninhydrine; typical fraction collection and lysine peak elution windows are described.
- Quality and repeatability: Two determinations from different test portions are required; the difference between paired results should not exceed 10% of their mean.
- Limitations: ISO 5510 notes the method can overestimate available lysine compared with biological assays; interpret results accordingly.
Applications and users
- Feed manufacturers and quality control laboratories: Routine testing of raw materials and finished feeds to assess lysine availability and nutritional quality.
- Animal nutritionists: Evaluating amino acid bioavailability for diet formulation.
- Regulatory and standardization bodies: Verifying compliance with feed composition specifications.
- Research labs: Comparative studies of processing effects (heat, Maillard reactions) on lysine availability.
Practical value: the standard provides a reproducible, instrument‑based protocol for quantifying available lysine using accessible chromatographic and spectrometric techniques, enabling feed producers and labs to monitor a key essential amino acid important for animal growth and performance.
Related standards
- ISO 5903 (determination of nitrogen for crude protein calculation)
- ISO 6497 / ISO 6498 (sampling and sample preparation for feed analysis)
- ISO 5983 (protein determination in feeding stuffs)
Keywords: ISO 5510:1984, available lysine, animal feeding stuffs, lysine determination, DNFB, column chromatography, spectrometry 570 nm, feed analysis, ion‑exchange resin.