SOP For D.O. Meter. Standard Operating Procedure for D.O. Meter

CALIBRATION OF DO METER

  1. PROCEDURE:
    1. Operation
      1. Ensure the cleaning and calibration status of the instrument.
      1. Switch on the main supply.
      1. Switch ON the instrument with the help of the “ON”/ “OFF” switch provided at the back of instrument.
      1. Display shows the instrument make and software version.
      1. Fit the  membrane on the lower part of the electrolyte tube. Be careful to handle its membrane.
      1. Fit the ring on the electrolyte tube, covering sides of the membrane.
      1. Fill potassium chloride solution (7.5%) in the electrolyte tube to its top.
      1. Insert the electrode in the electrolyte tube and tightly screw it up. Now the probe is read for use.
    1. Precautions:
      1. 7.5% KCl solution acts as good electrolyte in DO probe. Presence of any other salt in electrolyte solution may damage the probe.
      1. The electrolyte tube should not contain any air bubble. If it is present, it will cause fluctuations in the readings.
      1. After initialization display shows
Select DO                         Temp Date                        Time
  1. Select D.O. option with the help of “DOWN” key and press Enter.
Select                                Read                            Cal
  1. Display shows
  1. Rinse the electrode with Ultra-Q water and wipe with tissue paper.
    1. Dip the electrode in the sample solution to measure the amount of dissolved oxygen.
    1. Select “Read” with the help of “DOWN” key and press Enter.
    1. The D.O meter shows the reading of dissolved oxygen in PPM (Parts per million) with temperature.
    1. In case any malfunctioning/breakdown is observed during operation then inform to QC-In charge and label the  instrument with tag ‘BREAKDOWN’ and further proceeded by raising the deviation. 
    1. Calibration Procedure
      1. Ensure that the instrument is clean before usage.
      1. Connect the three-pin plug to power supply and switch on the instrument.
      1. Turn instrument on to any operational position-1 hour before use to ensure stability of operation; meter should be left on until final measurement for day is completed.
      1. Enter to select and “ESC” to continue.
      1. Select the DO from main menu by placing cursor below DO using the UP and DOWN key and press ‘Enter’ key, Display shows
SELECT READ               CAL

      

  1. Move the cursor to CAL using UP key and press ‘Enter’.
    1. Display shows
DIP ELECTRODE IN DO SOLUTION READ               CAL

      

  1. Now insert the DO probe (& temperature probe into the zero DO solution i.e. 2% of sodium sulphite solution.
    1. Press ‘Enter’ key. (if Auto temperature compensation is desired, the temperature probe should be connected to the temperature-input socket and insert it along with the DO probe in DO solution.
    1. If the temperature probe is not attached, Display shows
Error! Check the Temp Probe READ               CAL

      

  1. Now either, attach the temperature probe to the temperature input socket, insert it into the solution and press ‘Enter’ key for the ATC operation or Press the ‘Esc’ key for manual temperature compensation. If ‘Esc’ key is pressed, the display shows.
Enter Temperature 25.0 °C

      

  1. If enter key is pressed the displayed temperature is selected, to change the temperature, press the UP/DOWN keys the temperature value can now be changed
    1. Use the UP/DOWN keys to set each digit & press ‘Enter key to accept it, after accepting the temperature, press ‘Enter’.
    1. If Enter key is pressed, this temperature value is accepted or if ESC is pressed, the value can be entered again. After enter the temperature, the display shows following screen with DO value blinking indicating the calibration mode.
    1. Pressed, the display shows.
DO   :  *   *  PPM °C  :  *   *  .  *

      

  1. The DO being displayed corresponds to the solution, the display blinks. Let the DO value stabilizers. Now press the ‘enter’ key
    1. Display shows.
Enter standard solution DO: 07.0 ppm °C  :  *   *  .  *

      

  1. Using the UP/DOWN keys select the corresponding digit’s value & press ‘Enter’ key to move to the next digit. Enter the value of the standard DO solution at the corresponding temperature. The DO solution value of Ultra pure water at different temperature is given below (provided by manufacturer).
  1. Display shows.
Dip Do Probe in Standard solution DO: 07.0 ppm °C  :  *   *  .  *

      

  1. Press ‘Enter’ key. Display shows:
    1. If Enter key is pressed, thi, this temperature value is accepted or if ‘Esc’ is pressed, the value can be entered again. After entering the temperature, this display shows following screen with DO value blinking indicating the calibration mode.
    1. Display shows.
Dip Do Probe in Standard solution DO: 07.0 ppm °C  :  *   *  .  *

      

  1. Press ‘ Enter’ key, Display shows:
    1. If ‘Enter’ key is pressed, this temperature value is accepted or if ‘Esc’ is pressed, the value can be entered again. After enter the temperature, the display shows following screen with DO value blinking indicating the calibration mode.
    1. Pressed, the display shows.
DO   :  *   *  PPM °C  :  *   *  .  *

      

  1. The DO being displayed corresponds to the solution, the display blinks. Let the DO value stabilize, now press the ‘Enter’ key.
    1. Display shows:
  1. Display shows.
CAL DATA WILL BE LOST OK! <Ent> °C  :  *   *  .  *

      

  1. Pressed ‘Enter’. The display shows.
    1. Display shows.
CALIBRATION DONE! °C  :  *   *  .  *

      

  1.   Cleaning
  2. Wipe the instrument with dry and clean lint free cloth.
  3. Use Ultra-Q water to clean the electrode before and after each sample measurement and wipe with tissue paper.
    1.   Preventive Maintenance
      1. Protect instrument from temperature changes that may result from exposure to direct sunlight or contact with ice or cold wind.
      1. There should be no bubbles of air behind membrane. Electrodes with pressure compensators should have the pressure compensation membrane moved in and out with the eraser end of a pencil to ensure that all bubbles are removed from pressure.

Bhanu Pratap Singh

BHANU PRATAP SINGH IS EXPERIENCED IN PHARMACEUTICAL, AUTHOR AND FOUNDER OF PHARMACEUTICAL GUIDESLINE (WWW.PHARMAGUIDESLINE.COM), A WIDELY READ PHARMACEUTICAL BLOG SINCE 2019. EMAIL:- INFO@PHARMAGUIDESLINE.COM

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