Titration Tips Using Karl Fischer Instrumentation
General Purpose, Volumetric Karl Fischer Titrations
The information listed below is intended for informational purposes only and based on experiences performing analytical titrations using typical one-component systems.
Thermo Scientific Orion AF8 Advanced Karl Fischer Titrator
- To extend reagent tube life, draw titre through tube using a disposable syringe prior to beginning titrations (before selecting “yes” at the “Is Vessel Ready?” prompt). When concluding titrations, allow instrument to drain reagent only to the point where reagent is no longer present in the elastic section of the tubing assembly. The result will be reduced wear on the reagent tube by the pump rotor assembly.
- Always ensure the tube life counter is accurate. The manufacturer recommends a tube life of 20 liters for accurate and representative results. If the counter does not match reagent delivered, variable results can be obtained and will be observed in elevated steps/mg during instrument calibration. Approximately > 3500 steps during individual standard replicates and approximately > 125 steps/mg in as-determined water content per standard replicate.
- The titration vessel and glass sealing plate should be cleaned with a non-aqueous solution (e.g. methanol) and the grease seal replaced for titrations extending longer than 4 hours, to minimize contamination by foreign moisture.
- For high volume applications, a larger waste solvent reservoir (e.g. 4 L) can be used to minimize empty/discard of spent solvent. Exposure of the waste reservoir assembly to the atmosphere introduces variability in results until a complete reconditioning cycle is achieved. Note: the level of waste in the solvent reservoir should not exceed the height of working medium in the titration vessel. Back pressure and contamination of the titration vessel with waste solvent though the drain line will result.
- Refill sample solvent supply reservoir and empty waste solvent reservoir before vessel contents are reconditioned to equilibrium in preparation for titration.
- Rinse glassware, including supply and waste reservoirs, with a non-aqueous solution prior to sample solvent makeup.