Testing For Handling Errors; Determination Of Sample Influences - wtw photolab S12 Operating Instructions Manual

5 Analytical Quality Assurance (AQA)

5.2.5 Testing for Handling Errors

The user's own mode of operation must also be subjected to an exact
analysis.
The following questions may serve as a guide in this regard:
•
Is the test kit optimal for the measurement assignment in question?
•
Is the test kit's measuring range suitable?
•
Were the operating instructions for the test followed?
•
Was the sample volume correct?
•
Was the pipette handled properly?
•
Was a new pipette tip used?
•
Is the pH of the sample and measurement solution correct?
•
Was the reaction time adhered to?
•
Does the sample and reagent temperature lie within the correct range?
•
Is the cell clean and free from scratches?
•
Has the expiry date for the test kit been exceeded?
5.3 Determination of Sample Influences (matrix effects)
The influence of other substances contained in the sample may, under
certain cir cumstances, be so great that their recovery rates lie in the region
of several percent. It is recommended to check for any influence by using
the addition solution contain ed in the Spectroquant
A defined quantity of the addition solution (R-2), which contains a known
concen tration of the respective analyte, is added to the sample and the
recovery rate is de termined. The following difference is then calculated:
Result (sample + addition solution) – Result (sample)
If the calculated difference is equal to the concen tration of analyte of addi-
tion solution that was add ed, the recovery rate is 100 %. If the difference
is less than 90 %, then a matrix inter ference is present.
Release 01/2012
®
CombiCheck pack.
photoLab ® Series
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