Standard Operating Procedure pH METER
This SOP covers the operation procedure for the pH meter.
Procedure for general cleaning
- Ensure that the power supply to the instrument is switched OFF before cleaning.
- De dust the equipment daily externally with a clean dry cloth. Once a week remove adhered dust by wet mopping using a detergent solution. Afterward, wipe the surface with a clean dry cloth to remove traces of detergent. Precaution has to be taken to clean the instrument immediately with a dry cloth to remove the moisture.
- Switch on the instrument using power on/off switch in the rare of the instrument. Warm up the instrument for just a minute or two.
- Keep the SELECTOR in pH mode and the TEMP control knob at 25° C.
- The display should read 7.00, otherwise, adjust the pH to 7.00 by using the SET 7.0 knob and keep the SELECTOR in HOLD position and keep the push button in calibrate mode only.
- Wash the electrode with distilled water and wipe off the moisture. Dip the electrode in the sample beaker and stir the beaker for a while.
- Release the push button switch after minutes of stirring of the beaker and record the pH of the sample.
Preparation of standard buffer solution.
- Buffer pH 4.01
- Buffer pH 7.01
- Buffer pH 9.20.
Set the instrument by using pH 4.01 buffer solution and pH 9.20 buffer solutions. Repeat the previous operations. Take the 4.01 buffer into a suitable beaker and dip the electrode into it and stir for a
while release the push button to read the pH. > If it should read 4.01, otherwise adjust it to 4.01 by adjusting the Slope screw which is provided at the rear of the instrument.
Turn the SELECTOR to hold position and push the button to Read position. Take out the electrode and wash with water, wipe off the moisture. Take the 9.20 buffer into a suitable beaker and dip the electrode into it and stir for a while adjusting the SET BUFFER screw to 9.20.
Turn the SELECTOR to hold position and push the button to check position. Take out the electrode and wash with water, wipe off the moisture. Calibrate the instrument with a 7.01 buffer solution.
Take the 7.01 buffer solution into a suitable beaker and dip the electrode into it and stir for a while, release the push button to read the pH.
FREQUENCY OF CALIBRATION
► Calibrate the instrument every day before using the instrument
Before sample measurement Select two Buffer solutions for standardization whose difference in pH does not exceed 4 units and such that the expected pH of the material under test falls between them.
The integrated plastic housing and keypad are sealed to protect against accidental spills and splashes. The electrode holder arm is rapidly switched to both sides and swivels and articulates for convenient use and positioning.