Hanna Instruments HI 901 - Manual (Page 60)

5-20
METHODS
Filtered Derivatives:
Filtered Derivatives is an optional feature for equivalence point recognition.
This option adds a filtering procedure in the 1 st and 2 nd derivative computation algorithm
that reduces the influence of pH or mV noise.
The Filtered Derivatives option can be enabled by selecting YES in the Filtered Derivatives
Option screen.
Noise can appear due to:
• Chemical system properties (sample, titrant, solvent), such as slow chemical reactions
or unbuffered samples such as wastewater, tap water, wine.
• Electrode response.
• Incorrect method parameters settings such as Signal Stability, Stirring Speed, etc.
• Too small titrant doses.
Note: Even if false equivalence point detection has been highly diminished, a shift of the end
point volume might sometimes occur due to filtering. The shift is often at the level of
1 or 2 doses from the real equivalence point volume. For fast titrations and small
doses this is a useful option.
5.5.5 Pre-Titration Volume
During a regular titration, the equivalence point is reached after many doses are dispensed.
Most of these doses simply take up extra time while having no relevance for equivalence
point detection.
Pre-titration volume adds a large initial dose to jump directly to the proximity of the equivalence
point.
This first dose occurs after the pre-titration stir time is completed.