SOP FOR OPERATION AND CALIBRATION OF DIGITAL AUTOMATIC KARL FISCHER (KF) TITRATOR
1.0 OBJECTIVE : This procedure is laid down to explain the mode of operation & calibration of Digital Automatic Karl Fischer Titrator. (Make: VEEGO, MODEL No. VEEGO/MATIC-D)
2.0 SCOPE : This procedure is applicable for measuring the water content in finished products and raw materials.
3.0 RESPONSIBILITY : QC Chemist, QC Officer, QC Executive, QC In charge.
5.0 PROCEDURE: : Specially Dried Methanol, Micro syringe, Measuring cylinder, KF reagent, Tissue paper.
5.1 PRECAUTION :
5.1.1 Always use clean & dry reservoir.
5.1.2 Never drop the magnetic rotor in the reaction beaker.
5.1.3 Never tighten the nuts of the beaker clamp excessively as it may crush the ground edge of the beaker or deform the beaker holding ring.
5.1.4 Always use specially dried methanol.
5.1.5 After completion of analysis, rinse the reservoir & magnet with methanol.
5.1.6 Add the sample carefully in the reservoir, sample adhere to the wall of the reservoir.
5.2 OPERATION PROCEDURE
5.2.1 Switch on the mains.
5.2.2 Rinse the reaction beaker with the specially dried methanol.
5.2.3 Pour specially dried methanol in the reaction beaker to the extent that the metals wires of electrodes are fully immersed in the methanol.
5.2.4 Keep a clean and dry magnet in the reaction beaker.
5.2.5 Close the reaction beaker immediately to prevent moisture.
5.2.6 Pour the K.F reagent in the bottle fitted with the adapter connected to dispenser unit (inlet).
5.2.7 Connect the platinum electrode to the sockets provided on the instrument.
5.2.8 Connect the Titrator to mains and adjust speed of magnetic stirrer such that the wired ends of the electrodes do not get exposed.
5.2.9 Press the ‘START’ button for a second and release. The titration will start and at the end point of titration beep sound will produced. Then press the “STOP” button. The digital display shows the consumption of Karl fisher reagent.
5.2.10 Take micro syringe and fill with distilled water and note the weight.
5.2.11 Stop the stirrer and remove the large rubber stopper of the reaction beaker and add accurately about 20 mg of water in to the methanol in the reaction beaker. Note the weight of syringe and calculate the weight of water. Care should be taken not to loose any part of water on the sidewall of the beaker or sensors.
5.1.12 Press <START> push button to set the display 0.00 ml.
5.2.13 The dispenser will again start operating and the display will show the volume of K.F. reagent being added. As before the operating will stop on reaching the end point and beep sound will produce.
5.2.14 Read the display and not it down. This reading indicated the volume of reagent in ml required to remove the water added by the micro syringe.
5.2.15 Calculate the factor as given below: –
Factor = Weight of water in mg
Volume of K.F reagent in ml
5.2.16 Factor should be between 4.5 and 6.5
5.2.17 Weigh accurately the sample mentioned in the monograph otherwise weigh 100mg of the sample and carefully add into the reservoir.
5.2.18 Now, titrate it with K.F reagent by pressing the ‘start’ button for a second and release. With this the red lamp will go ‘off’ and green lamp will become ‘on’. The dispenser will become active and the reagent with start entering the reaction beaker. The digital display will start indicating. The automatic operation will continue till the end point is reached with the green lamp going ‘off’ and the red lamp become on with the note of audio signal.
5.2.19.Calculate the water of sample as given below: –
Water% = Volume of K.F. Reagent in ml x Factor x100
Weight of sample in mg
5.2.20 After completion of analysis, drain the sample and rinse the reaction beaker with the methanol.
5.2.21 Do the Analysis activity entry in the logbook of K.F. Titrator (Annexure) and note down the Instrument ID in protocols of analysis.
5.3 CALIBRATION PROCEDURE :
5.3.1 For Calibration of dispensing volume of KF reagent , measure the volume in clean and dry measuring cylinder of 10 ml capacity (limits 8.0 ml ± 0.2 ml )
5.3.2 Perform the dispensing volume measurement in triplicate & record in Annex.
5.3.3 Calculate the KF factor as in operating procedure .
5.3.4 Take about 100 mg DST (Di-sodium tartrate dihydrate ) and add it in reaction vessel dissolve completely.
5.3.5 Titrate with KF Reagent up to beep sound.
5.3.6 Calculate the % of water content in DST by the KF factor (limits 15.60% to 15.80% and RSD of triplicate NMT 1%) & record in Annex. & affixed Calibration label.
5.3.7 After completion of calibration drain the reaction mixture content from the vessel and rinse the reaction vessel with the methanol and dry it.
DST : Di-sodium tartrate dehydrate)
K.F reagent : Karl fisher reagent.
RSD : Relative standard deviation
NMT : Not more than