SOP for Operation of Potentiometer (Metrohm)

OBJECTIVE 

To provide procedures to be followed when operating the potentiometer. 

SCOPE 

This procedure shall apply to the potentiometer in the QC Laboratory. 

RESPONSIBILITY 

• It is the responsibility of the QC Executive operating the apparatus to follow the procedure fully. 
• It is the responsibility of the QC Manager to make sure that the procedure is followed fully and without deviating.

PROCEDURE

1.  Switching the Instrument ON and OFF

• Switch on the instrument by Pressing the red [STOP] key. 
• As soon as the burette unit has been recognized the following message appears: “You must configure the new burette unit before using it”. Confirm the message with [OK]. 
• The request to carry out the PREP function appears and confirms the message with [OK] and the main dialog is displayed. 
• Switch off the instrument by pressing down the red [STOP] key. A progress bar is displayed and if the key is released during this time, then the instrument will not be switched off. 

ALSO READ: SOP for Operation and Calibration Procedure for Analytical Balance

2.  Adding And Configuring A Solution

• The burette unit must be attached before carrying out the instructions listed below and the Exchange unit proceeds by sliding the exchange unit from the front of the 848 Titrino Plus and pushing all to the rear (back). It must snap in audibly. 
• In the main dialog, select Menu with the arrow keys [↑] or [↓] and confirm with [OK]. The main menu opens. 
• With the arrow key [↓], select the menu item System and confirm with [OK]. The system dialog opens 
• Select the menu item Solution and confirm with [OK]. The list of the configured solutions is displayed. 
• Define the name of the solution with the arrow keys by selecting the required character and pressing [OK] to apply it in the text line and apply the name with Accept or [BACK], the text editor is closed and the name is displayed in the properties dialog. 
• Select the parameter Concentration and open the editing dialog with [OK]. Enter the concentration of titrant and apply with accept or [BACK]. 
• Select the parameter Concentration unit and use [OK] to open the list of available units and select the desired unit with [OK]. Repeating pressing on [BACK] will switch you to the main dialog.

3.  Creating a Titration Method 

• Open the method table by selecting Method in the main dialog. Confirm with [OK], the method table is opened. 
• Select New and press [OK], and the dialog New Method is displayed. 
• Select the titration mode by pressing Mode and pressing [OK] and apply the default value DET with [BACK]. 
• Select Measured Quantity value pH with [BACK] and return to the main dialog by pressing [BACK]. The method template DET_pH is now loaded and is displayed in the main dialog under Method. 
• In the main dialog, select Menu and confirm with [Ok} and select the menu item Parameters and confirm with [OK] in order to select a solution required in the titration. 
• Select titration parameters and confirm with [OK]. Select the parameter Solution and confirm with [OK], the list of the configured solutions is displayed. 
• Select the newly configured solution and apply with [Ok], with [BACK], and return to the dialog Parameters. 
• Open the dialog Stop conditions by selecting the menu item Stop conditions and open the corresponding dialog with [OK]. Define the stop volume by entering a value corresponding to the cylinder volume of the dosing unit used and apply with Accept or [BACK]. 
• Stop EP and Volume after EP must be kept 9 and 1 respectively, by applying Accept or [BACK] and [BACK] to switch to the Parameters. 
• Select the menu item Calculation and open the corresponding dialog with [OK] and for each titration up to five (R1, R2, R3, R4, & R5) can be calculated. 
• Select the line R1: for the first result and press [OK], in this dialog the properties for the result are defined. Select the Result name press [OK] and enter the designation for the result, e.g. “Content%”; apply the name with Accept or [BACK].
• Enter the formula by selecting line R1 = and press [OK]. The formula for the calculation of the result is entered here. The formula editor consists of an input field, a sequence of numbers, mathematical operators, various variables, and functions. With the arrow keys you can move the cursor within the lines and with [OK] you can insert the selected character or the corresponding variables into the input field. 

i.e. R1= (EP1 * CONC * equivalent weight * ATW)/COO 

• Apply the formula with Accept or [BACK]. Click twice on [BACK] to switch to the dialog Parameters.
• Define the report output by selecting Results, Curve, and Calculations/Statistics and confirm with [OK] in each case. Select one and confirm with [OK] in each case.
• With [BACK], return/switch to the dialog Parameters.
• Enter the sample identification by switching to the main dialog with [BACK] if necessary. By selecting the line ID1 and pressing [OK] you will enter the sample designation (e.g. Aspirin) and apply with Accept or [BACK].
• Selecting the line ID2 and pressing [OK] you will enter further sample designation (e.g. Batch number) and apply with Accept or [BACK].
• Enter the sample size by selecting the line Sample size and pressing [OK]. Enter a value and apply with Accept or [BACK].
• Select the line Unit and press [OK]; select the unit for the sample size press [BACK] or [OK].

4.  Carrying out a Determination (Titration) 

• First, the exchange unit with the titrant has to be prepared. The tubbings must be rinsed and bubble-free this is done by a function known as dosing.
• Place an empty beaker on the stirrer, on the main dialog, select Menu, and press [OK] then select Manual Control and press [OK]. 
• Select the line Dosing and press [OK] the following message is displayed. “Check the burette tip. It should point to a vessel. Do you want to continue?” confirm the message with [OK]. The function PREP is being carried out and the tubbings of the exchange unit are automatically rinsed. With [BACK] you will exit the Manual control 
• Rinse the electrode and the burette tip with water from a spray bottle.
• Place the sample beaker on the stirrer and immerse the electrode by lowering the electrode holder into the sample and also placing a stirring bar into the sample.
• The determination starts by pressing the [START] key, and the individual steps of the method are displayed.
• After the titration, a report is printed out automatically.

ABBREVIATION

QC: Quality Control

QA: Quality Assurance

ANNEXURE

Nil

REVISION HISTORY 

Nil

ALSO READ: SOP for Operation of Shimadzu UV–1800 UV Spectrophotometer