Function and design
multi N/C 2100S (duo, pharma)
34
Limit of detection
The detection limit of the calibration specifies the lowest concentration for which a veri-
fication is possible with a given probability.
Limit of determination
The determination limit of the calibration specifies the lowest concentration that can be
differentiated quantitatively from the zero point with a given probability.
3.6.5
Other calculations
For all measurements where multiple injections are carried out, the average value (AV),
the standard deviation (SD) and the variation coefficient (VC) are calculated and dis-
played. For each sample, a tenfold determination can be carried out as a maximum.
Outlier selection
The control and analysis software can automatically select outliers. The user can specify
a maximum limit for the variation coefficient or even for the standard deviation for this.
The analyzer performs the minimum number of measurements specified in the method.
If the distribution of the measured values is then above the specified maximum value
(SD or VC), additional injections are carried out from the same sample until the specified
maximum number of measurements has been reached.
After each measurement, the software determines the variation coefficient and standard
deviation for all combinations of the measured values. If the variation coefficient or the
standard deviation of at least one combination is smaller than the specified maximum
value, no further measurements are carried out.
The software determines the analysis result from the combination of measured values
with the smallest variation coefficient or the smallest standard deviation. The unused
measurements are considered outliers and deleted.
If carbon and nitrogen are detected in parallel, the outlier selection takes place sepa-
rately for each parameter.
Average value
The average value of the final result is calculated from the concentrations determined
for the individual detections after eliminating the outliers.
3.7
Blank values
3.7.1
Water blank values
Preparation water blank value
Especially for measurements with low TOC concentrations (µg/l range), the TOC content
of the water used to prepare the standard solutions must be taken into account. The
concentration of the standard solution and the TOC blank value of the preparation water
are often within the same range. This blank value can be taken into account during cali-
bration.
The TOC content of the preparation water is measured separately before the calibration.
The software then subtracts the average integral determined for the preparation water
for each measuring point of the calibration from the determined gross integral.
I
Net
= I
Gross
– I
Preparation water
The software determines the calibration function from the net integrals. Mathemati-
cally, this corresponds to a parallel movement of the calibration line.
The software also takes the preparation water blank value into account when determin-
ing the daily factor.
