4-16 Performance Verification
PROCEDURE
1. Create a 0.5% solution of Tween 20 and distilled water. As an example,
add 1 ml of Tween 20 to 200 ml of distilled water. Shake well for several
minutes.
2. Add 6 drops of yellow food coloring to the 200 ml of the 0.5% Tween
solution. This should give an absorbance of 1.4 to 2.0 absorbance units
when using 200 ml in the well. If you wish to attain an absorbance up to
3.0 OD, add 3 additional drops of food coloring (a total of 9 drops).
3. Stir well to ensure all the color is spread throughout the solution. This is
entirely a trial-and-error process. If it does not give enough absorbance,
add another drop of food coloring. The reader will display absorbance
units up to 3.000 absorbance units; it is specified to be linear to 2.000 **
absorbance units. (** This is a configurable value and may vary,
depending on the reader model.)
4. Set up a rack containing 10 tubes, numbered consecutively.
Table 4-2: Test Tube Dilutions
Tube Number 1 2 3 4 5 6 7 8 9 10
Volume of
Original
Solution (ml)
20 18 16 14 12 10 8 6 4 2
Volume of 0.5%
Tween Solution
(ml)
0 2 4 6 8 10 12 14 16 18
Absorbance
(Expected if
original solution
is 2.0 at 200 µl)
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
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