The conductivity meter is used to measure the conductivity in the solution. It is also known as an EC meter (Electrical conductivity meter). It consists of a probe. The probe is used to measure the conductivity of the solution. Two electrodes are fixed about 1 cm from each other. A small amp power current flows through the electrodes dipped in the solution, if the concentration of ions in the solution is high then the flow of current will be fast, hence the conductance is high. Operation and calibration are elaborated in the SOP for the conductivity meter.
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SOP FOR OPERATION & CALIBRATION OF CONDUCTIVITY METER.
1. Objective: To lay down a procedure for Operation & Calibration of Conductivity Meter
2. Scope: The procedure of this SOP shall be applicable to the Quality Control Department of XYZ Pharmaceuticals, City
3. Responsibility : Quality Control Chemist
4. Accountability : Quality Control Manager
5. Abbreviations :
S.O.P. :Standard Operating Procedure
QC : Quality Control
QA : Quality Assurance
6. General setting of conductivity meter :
6.1Â Â Connect the conductivity meter to the main supply rough the MAINS chord.
6.2Â Â Keep the POWER switch in the off position (The display will be fully off).
6.3  Connect a conductivity cell of suitable K value to the CELL – sockets (For the selection of cell constant K, refer to Sec. 6.0)
6.4 Connect the temperature probe to the TEMP socket.
6.5 Connect the optional printer if it is to be used. For operation with the printer, refer to sec. 12.
6.6 Switch on the instrument.
6.7 If there is previously stored data in memory display will be SyS – 306 for a moment and Str data / X.XX X.XX massage flashes alternately to indicate last stored data in the sequence of cell constant of conductivity cell and selected standard solution.
6.8 If there is no previously stored data in memory display will be SyS – 306 for a moment and the Put Std message will be displayed.
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7.0 Calibration of conductivity meter :
Calibration of the conductivity meter is performed by taking some steps, Preparation of Standard solution of KCl., selecting the KCl solution, and calculating the conductivity.
7.1 Preparation of STD. Kcl Sol.
Take 7.459 grams of dried KCI and dissolve it in some distilled water (-double distilled) in a one-liter measuring jar.
Fill the measuring jar to a one-liter mark with distilled water. This gives a 0.1 M KCI solution. 0.01 M KCI solution is prepared by diluting the 0.1 M KCI solution in the proportion of 1: 10.
0.01 M KCI solutions are prepared by diluting the 0.01 M KCI solution in the proportion of 1:10.
7.2 Selection of standard KCI solutions
As a rule of thumb, wherever measurement is based on comparison with a known standard, the standard chosen should be closer to the value under measurement.
In view of the above, Systronics Conductivity Meter Model 306, offers three standard solutions with which the unit can be standardized.
The conductivity and temperature co-efficient of the three at/around 25 deg C are given below :
Concentration at 25 deg CConductivity at 25 deg CTemp-co0.1 M KCI12.88 mS+1.90%0.01 M KCI1.413 mS+1.94%0.001 M KCI0.146 mS+2.04%conductivity-temperature-table
The above table can be used to calculate the conductivity (approx) at any other ambient temperature.
EXAMPLE: Calculation of conductivity of 0.01 KCI at 300C.
C 300C = C 250C + C 250C× 1.94 / 100 × (300C – 250C)
= 1.413 mS + 1.413 × 1.94/100 × 5
= 1.55 approx
Calibration frequency: Daily
Note: The procedure for operation and calibration of the conductivity meter provided in the SOP for the conductivity meter may vary in case of different make of the instrument.
References:
- SOP Guideline by D.H. Shah. (Book)
- Electrical conductivity meter-Wikipedia- The free encyclopedia.
