Overview - ISO 19043:2023 (Natural rubber latex concentrate - Total phosphate)
ISO 19043:2023 specifies a spectrophotometric method for the determination of total phosphate content in natural rubber latex concentrate (principally from Hevea brasiliensis). The standard describes sample preparation, reagents, apparatus, calibration, measurement at 470 nm, calculation and reporting rules. It is intended for quality control, specification testing and laboratory analysis of concentrated natural rubber latex.
Key topics and technical requirements
- Scope limitation: Method is not necessarily suitable for latex from species other than Hevea brasiliensis.
- Principle: Coagulate ~20 g of concentrated latex with hydrochloric acid, separate serum, react residual phosphate with vanadate–molybdate reagent and measure absorbance at 470 nm.
- Reagents: Analytical-grade reagents including HCl (370 g/kg), vanadate molybdate reagent, and a potassium dihydrogen phosphate (KH2PO4) stock solution (500 mg·dm‑3) - commercially supplied or prepared.
- Apparatus: Analytical balance (0.1 mg), Class A volumetric pipettes (ISO 648), spectrophotometer set to 470 nm, and 8 µm filter paper (e.g., Whatman No.40).
- Calibration: Prepare a calibration curve from standard phosphate solutions (0–20 mg·dm‑3 final concentrations after reagent addition) and determine slope (S) for calculation.
- Procedure controls: Duplicate determinations from the same homogenized sample; the difference between duplicates shall not exceed 30 mg/kg. Results are reported as the mean of duplicate determinations.
- Expression & calculation: Phosphate content is calculated using measured absorbance, calibration slope, sample mass, total solids content and volumetric factors as specified in the standard.
- Precision: Annex A summarizes interlaboratory precision (ITP) data (ten labs in China and India, 2022) with repeatability/day‑to‑day repeatability and reproducibility figures.
Practical applications
- Quality control and specification testing in rubber manufacturing and latex concentrate production.
- Incoming raw-material inspection by rubber processors, latex concentrate suppliers, and independent testing laboratories.
- R&D and regulatory compliance where phosphate content affects stability, coagulation behaviour, or downstream processing of natural rubber latex.
Who should use ISO 19043:2023
- Laboratory analysts in rubber and latex testing labs
- QA/QC managers at latex concentrate producers and rubber goods manufacturers
- Technical staff in procurement and compliance evaluating latex feedstocks
Related standards
- ISO 124 - Latex, rubber - Determination of total solids content (used within ISO 19043 for solids correction)
- ISO 648 - Laboratory glassware - Single-volume pipettes (class A requirements)
- ISO 19983 - Determination of precision of test methods (precision evaluation referenced in Annex A)
Note: Users should observe normal laboratory safety practices and verify patent or proprietary reagent considerations where applicable.