6. Quality
Control
58
Instructions for Use for SUNRISE No. 30086638 Rev No. 2.9
2021-07
6.3.4
Instrument Precision with Liquid Samples
This procedure can be used to check the precision of the measurements from
one microplate to another.
Fill a new microplate with a freshly prepared Methyl Orange in 0.1 % Tween 20
solution, use different dilutions of the solution in each well so that a range of
optical densities is obtained. Make sure that the wells contain at least 200 µl.
Define a test run using the 492 nm filter and then measure the microplate at least
three times.
For each well calculate the following:
•
the average OD value
•
the highest and lowest values
•
the difference between the average, highest and lowest values
Example for a SUNRISE equipped with 4filter option
Readings 0.000 to 2.000 OD
The difference between the average and the highest and lowest values for the
same well should be /- (1.0 % + 0.010 OD)
e.g. 1.000 +/- 0.020 OD
Readings 2.001 to 3.000 OD
The difference between the average and the highest and lowest values for the
same well should be /- (1.5 % + 0.010 OD)
e.g. 2.400 +/- 0.046 OD
Readings above 3.000 OD
Readings above 3.000 OD are only used as an indication and the precision
cannot be guaranteed.
6.3.5
Instrument Linearity with Liquid Samples
The linearity for the instrument and application at the wavelength used can be
checked by using a dilution series of a solution.
The result depends on the purity of the dye used and the meniscus of the liquid in
the wells.
As a reference, dilution series of Methyl Orange in 0.1 % Tween 20 solution for
measurements at 492 nm can be used.
The dilution series should be within the range of 0.1 to 3.0 OD for a 4filter or
6filter instrument and within the range of 0.1 to 2.5 OD for a tuneable wavelength
instrument.
For other wavelengths, different solutions must be used.
250 ml of each dilution are then pipetted into the microplate, a minimum of at
least two samples should be used for each dilution to reduce the errors caused
by pipetting.
Make sure that the instrument is using the accuracy measurement mode.
The microplate is then measured and a linear regression of OD against
concentration is drawn from the average of the measured OD values.
Determine the unweighted residual square value R
2
of the regression line.
Typical residual square values for a standard application are equal or better than
R
2
= 0.998.
