● Not measuring the correct volume of blood due to poor technique or using a wet or chipped pipette.
● When using anticoagulated venous blood, not mixing the sample sufficiently.
● Not ensuring that the optical surfaces of a
cuvette are clean and dry and there are no air bubbles in the solution.
● Not protecting a colorimeter or haemoglobin meter from direct sunlight and not checking the performance of an instrument or maintaining it
as instructed by the manufacturer. A common error when using a filter colorimeter is using a glass filter which is not clean.
● Not checking a diluting fluid such as Drabkin’s for signs of deterioration as explained in the HiCN techniques.
Technique to prevent cuvette-related errors
1. Hold a clean cuvette only by its frosted (matt) or ridged sides. When transferring a solution to a cuvette, allow the fluid to run down the inside wall of the cuvette. This will help to avoid air bubbles in the solution. Do not fill a cuvette more than three quarters full.
2. Using a tissue or soft clean cloth, wipe clean the clear optical surfaces of the cuvette.
Carefully insert the cuvette in the colorimeter or haemoglobin meter (optical surfaces facing the light source).
Note: Ensure a solution is at room temperature before reading its absorbance otherwise condensation will form on the outside of the cuvette which will give an incorrect reading.
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