COLORIMETRIC TECHNIQUE

This method used color indicator to examine the value PH of the media when adjustment is in progress. The indicator is added to the media with other prepared standard solution, the standard solution serve as a control agent when the medium is been adjusted the color of the media is compared with the color of the media until the media color matched with the standard solution that it the point of the desire result.

• GENERAL MEDICAL LABORATORY
• INTRODUCTION TO MEDICAL LABORATORY

To carry out this procedure there some apparatus used, this is listed bellow;

1. Comparator rack
2. Set of standard PH tube, i.e. made up of buffer solution and indicator
3. Comparator tube
4. Phenol red as indicator solution
5. 10M and 0.1M HCL, 10M and 1.0M and 0.1M NaOH
6. Micro-burrete
7. Pipette

• INTRODUCTION TO MEDICAL LABORATORY

PROCEDURE

i.                    Set six comparator tube in a comparator rack, in the first three of the tube add 5ml of the media and add 5ml of water to the remaining three.

ii.                  To the first tube of the media, add indicator as it is present in the standard PH volume

iii.                Make sure that the standard PH used should be bellow and above the required value, for example if the required value is 6.7PH then the standard pH tube to be used will be 6.6pH and 6.8pH value.

iv.                If the medium is too acidic then add 0.1M NaOH from a burette to fill the color, the color of the tube containing indicator and the medium, but if the medium is too alkaline, then add 0.1 HCL.

v.                  Measure the volume of acid or alkaline importantly in other to adjust the reaction of 5ml of the media placed in the tube.

vi.                Take two average reading and calculate the volume of acid or alkaline to be added to the medium and add the require volume of acid or alkali in the concentrated medium.

Mathematical aspect of it is that when 0.5ml of 0.1M HCL is needed to raise the pH of 5ml of the medium, then 2.5ml of 0.1MHCL is needed to raise the pH of 25ml of the medium, these happen continuously depend on the volume of the media. When the alkali or acid is added to the medium, mixed the compound very well and used the same technique explained above to check the pH value of the medium.