Diesse Chorus - Titration in the Qualitative Tests

Manuale operativo CHORUS
94 Rev. 0 del 06/2012
Index
Negative Doubtful Positive
Index
( high value)
Index
( low value)
1
The OD is then compared to the acceptability upper and lower limits ( 100 – 1000 ) defined by the
method parameters. If OD
cal
complies with the parameters,
• OD
upper
≥ OD
cal
≥ OD
lower
Its value is stored in the memory; otherwise, either error Cal Low , or Cal High arises and the
calibration fails.
5.3.3 T ITRATION IN THE QUALITATIVE TESTS
The sample is processed with one strip of a test batch and its optical density is thus determined:
OD
sample
= OD3 – OD1
Then, Index parameter (Ndx) is evaluated, using the OD
cal
that was stored for the test batch, as
follows:
Index = OD
sample
/ OD
cal
The index value is used on a linear scale, as the one of the fig. 110, to evaluate whether it is positive,
negative or doubtful (doubt area).
In the final report the result appears as P, N, or D with the indication of the index value.
fig. 110
The range of doubt is defined symmetrically with respect to the unit, and the percentage is determined
in the method file. For ex.: if the percentage of doubt is 20%, it turns out that:
• if I
sample
> 1,2 Positive
• if I
sample
< 0,8 Negative
• if 1,2 ≥ I
sample
≥0,8 Doubtful