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SOP for pH Meter (Pico+)


Standard operating procedure of pH Meter (Pico+) including operation and calibration.

1.0  OBJECTIVE

       To describe the procedure for operation and calibration of pH meter (Pico+).

2.0  SCOPE

       This SOP is applicable for the operation and calibration of pH meter (Pico+).

3.0  RESPONSIBILITY

       Officer/ Executive - Quality Control

4.0  ACCOUNTABILITY

       Manager - Quality Control

5.0  PROCEDURE

5.1  Operation of pH meter

5.1.1  Ensure that the instrument is on clean and dry platform.
5.1.2  Ensure that the instrument is clean.
5.1.3  Switch on the main power supply to the instrument that displays reads 
                              “LABINDIA INSTRUMENT pH meter”.
5.1.4  Press mode, it will display “pH mode Press ENTER or MODE”
                               Press enter to entering in pH mode.
5.1.5  Ensure that the instrument is calibrated. (If the instrument is calibrated the display shows I on the right side of the display window, If instrument is not calibrated, display shows N on the right side of the display window).
5.1.6  If it is not calibrated, calibrate the instrument before use.
5.1.7  Remove the pH electrode from the storage solution and rinse it with purified water 2-3 times. Soak the excess water with tissue paper and insert the pH electrode and temperature sensor in the sample beaker.
5.1.8  Stir the sample solution keeping the pH electrode and resistant temperature detector immersed.
5.1.9  Allow stabilizing the pH and then record the pH. The display shows the pH of sample, temperature °C, mV and calibration status as I.
5.1.10  Press ENTER to take print of the observation.
5.1.11  Select the start mode By”.” Key.
5.1.12  If it is in standard mode the display will show “*”.
5.1.13  After completion of pH measurement rinse the electrode and temperature sensor with the purified water, soak the excess water with tissue paper and insert the pH electrode and temperature sensor in the storage solution (Buffer of pH 7 having 1 gm Potassium chloride in 100 ml).
5.1.14  After measurement enter details in usage log book.

5.2  Calibration of pH meter

5.2.1  Preparation of buffer solutions for standardization.
5.2.2  Buffer solution pH 1.68 : Dissolve 6.355 g of potassium tetra oxalate in sufficient distilled water to produce 500 ml. Mix thoroughly to get uniform concentration.
5.2.3  Buffer solution pH 4.01 : Dissolve 5.105 g of potassium hydrogen phthalate (previously dried at 110ºC for 2 hours) in sufficient distilled water to produce 500 ml. Mix thoroughly to get uniform concentration.
5.2.4  Buffer solution pH 6.87 : Dissolve 1.70 g of potassium dihydrogen phosphate and 1.775 g of anhydrous disodium hydrogen phosphate both previously dried at 110ºC to 130ºC for two hours, in sufficient distilled water to produce 500 ml. Mix thoroughly to get uniform concentration.
5.2.5  Buffer solution pH 9.18 : Dissolve 1.907 g of di-sodium tetra borate (previously dried at 110ºC for 2 hours) in sufficient distilled water to produce 500 ml. Mix thoroughly to get uniform concentration.
5.2.6  Buffer solution pH 12.45 : Shake an excess of Calcium Hydroxide with water, and decant at 25 ºC before use . Protect from absorption of Carbon dioxide.
5.2.7  Switch on the main power supply to the instrument that displays reads “LABINDIA INSTRUMENT pH meter”.
5.2.8  Allow the instrument to stabilize for at least 15 minutes before performing daily calibration.
5.2.9  Rinse the pH electrode with purified water 2-3 times; remove the excess water by soaking with tissue paper.
5.2.10  Press “MODE”, ‘ and then “ENTER” key respectively.
5.2.11  Press “ MEM CLEAR” then it will display ‘ Enter password’.
5.2.12  Enter password followed by pressing ‘ENTER’ it will display 
                                          ‘Memory Clear.
                                           1> Rdgs 2> Cal 3> All
5.2.13  Enter ‘3’ followed by pressing ‘ ENTER’ key, it will display memory is cleared. 
5.2.14  Press “CAL” key which displays “No Data then press ‘ ENTER’ key and enter password followed by pressing ‘ENTER’ key it will display 
                                          Calibration Mode
                                          1) stand. 2) calib”
5.2.15  Press the”1”key and then press the enter key. “Use Buffer (6.8-7.2)” will Appear, then Enter pH =
5.2.16  Enter 6.87 and press ‘ENTER respectively’. Press ‘ENTER’ key if stable pH appear on display.
5.2.17  “Calibration over” Appear followed by 
                                         “Calibration”. 
                                          Offset= 1>Y 2>N 
5.2.18  Check whether electrode off set is with in ± 30 Mv or out of ± 30 mV.
5.2.19  If electrode offset is out of limit (±30 mV) check the efficacy of buffer or probe and replace if necessary.
5.2.20  If offset is within limit press “ 1 ” or if offset is out of limit press “ 2 ”. 
5.2.21  When you press “ 1 ” Buffer < 6.5 or > 7.5 appear. 
                                          Enter pH= 
5.2.22  Remove the electrode and RTD from 6.87 pH buffer and rinse the electrode with purified water 2-3 times remove the excess water by soaking with tissue paper and insert the pH electrode and RTD in pH 4.01 buffers.
5.2.23  Enter 4.01 and press ‘ENTER’ key. Press ‘ENTER’ key if stable pH appear on display.
5.2.24  “Calibration over” appear followed by
                                         “Calibration’’
                                          Offset = 1>Y 2>N
5.2.25  You press “1 ” then Buffer > 7.5 Appear. Enter pH= 
5.2.26  Remove the electrode and RTD from 4.01 pH buffer and rinse the electrode with purified water 2-3 times remove the excess water by soaking with tissue paper and insert the pH electrode and RTD in pH 9.18 buffers.
5.2.27  Enter 9.18 and press “ENTER” key respectively 
                                         Press “ENTER” if stable pH appear on display. 
5.2.28  If slope is with in limit (i.e. 80% ~ 120%) display reads calibration over, otherwise display reads “Incorrect buffer probe faulty”.
5.2.29  Note down the readings of buffer 6.86, 4.01, 9.18 respectively as per operation procedure and note down the readings.
5.2.30  In case if we have to measure pH less than 3 or more than 10 then before use calibrate the instrument with buffer of pH 1.68 and buffer of pH 12.45 instead of Buffer of pH 4.01 and buffer of pH 9.18, respectively.
5.3  Frequency of calibration: Daily before use and after maintenance.
5.4  Storage of buffers: Buffer solution shall not be stored more than 7 days. Store the buffer solution in glass bottle; use the buffer solution if the buffer solution is clear during the storage.
5.5  Storage of electrode: Store the electrode in Buffer of pH 7 having 1 gm KCl in 100 ml. Change the storage solution weekly. Do not store the pH electrode in distilled water or purified water.

6.0  ABBREVIATION

6.1  SOP - Standard Operating Procedure




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