ISO 5810:1982

Overview

ISO 5810:1982 specifies a potentiometric titration method for determining the chloride content of starches and derived products. The method uses a standard volumetric silver nitrate (AgNO3) solution and potentiometric end‑point detection. It is not applicable to cationic starches or amyloids that are soluble when cold (their high viscosity prevents correct stirring). The result is reported as sodium chloride (NaCl) percentage by mass.

Key topics and technical requirements

• Principle: Potentiometric titration of a solution or suspension of the sample with standard AgNO3; end‑point is the inflection point of the potentiometric curve.
• Reagents: Concentrated nitric acid (HNO3) and standard volumetric silver nitrate solution (typical concentrations 0.05 mol·L–1 or 0.02 mol·L–1).
• Electrodes and instrumentation:
  • Silver/silver chloride indicator electrode (can be prepared or purchased).
  • Suitable reference electrode.
  • Potentiometer or pH‑meter with millivolt scale and calibration.
  • Variable‑speed stirrer to ensure homogeneous suspension.
• Apparatus: Standard laboratory glassware (beakers, 1 mL pipettes complying with ISO 648, 10 mL burettes complying with ISO 385/2), analytical balance.

• Sample preparation and test portions: Samples must be homogenized. Test portion mass is chosen by expected chloride content: