KF titrator (volumetric) · Calibration procedure
Titre determination
Determines how many mg of water 1 mL of KF reagent reacts with, using a water standard such as sodium tartrate dihydrate.
PURPOSE
Why this is checked
Every KF result is volume × titre, so the titre must be known accurately. KF reagents slowly lose strength and pick up moisture, so the titre is determined regularly rather than taken from the label.
Frequency
Typically daily before use, when a new reagent bottle is opened and after any change in conditions, as defined in your SOP.
Learn how the KF titrator (volumetric) worksYOU WILL NEED
Standards & tools
- Sodium tartrate dihydrate, water content about 15.66% (theoretical), or a certified liquid water standard
- Calibrated analytical balance (readability 0.1 mg or better)
BEFORE YOU START
Prerequisites
- Fresh solvent in the cell and the cell conditioned
- Drift low and stable (for example below 20 µg/min)
- Sodium tartrate dihydrate dissolves slowly in methanol; allow enough stirring time or use a suitable solvent
PROCEDURE
Step by step
- 1Weigh about 150 mg of sodium tartrate dihydrate accurately by difference (this releases about 23 mg of water, using roughly half of a 10 mL burette at a 5 mg/mL titre).
- 2Add it to the conditioned cell and enter the exact mass.
- 3Titrate to the endpoint and record the volume consumed.
- 4Repeat to obtain at least three determinations.
- 5Calculate each titre, the mean and the %RSD.
RECORD
Example observation table
| Determination | Mass of sodium tartrate (mg) | Water present (mg) | Volume consumed (mL) | Titre (mg/mL) |
|---|---|---|---|---|
| 1 | 150.2 | 23.521 | 4.72 | 4.983 |
| 2 | 148.6 | 23.271 | 4.66 | 4.994 |
| 3 | 152.3 | 23.850 | 4.79 | 4.979 |
CALCULATION
How to calculate the result
Titre F (mg/mL) = (W × 0.1566) ÷ V, where W is the mass of sodium tartrate dihydrate (mg) and V is the volume consumed (mL)
- Determination 1: water present = 150.2 × 0.1566 = 23.521 mg
- F = 23.521 ÷ 4.72 = 4.983 mg/mL
- Mean of three = 4.985 mg/mL; %RSD = 0.15%
ACCEPTANCE CRITERIA
Pass if
- %RSD of the titre determinations not more than 1.0% (some SOPs use 0.5%).
- Titre within the range expected for the reagent (for a nominal 5 mg/mL reagent, typically about 4.5–5.5 mg/mL).
IF IT FAILS
What to do
- Check the drift and the cell for leaks, then repeat with fresh solvent.
- Check the standard is within its expiry and has been stored closed.
- If the titre is well below the expected value, the reagent may have absorbed moisture; replace it.
- Do not analyse samples until a valid titre is obtained.
MORE
Other KF titrator (volumetric) calibrations
In LimsPulse · Calibration Management
LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.