Millipore Spectroquant Multy Operating Manual page 254

5.6 User methods
The software provides two possibilities for saving user-specific
methods in the instrument. For the user-concentration method
(section 5.6.1), prepared standards are measured and the
instrument defines the programming. The programme "User
polynomials" (section 5.6.2) enables the user to specify polyno-
mials and thus also, on the one hand, to correctly enter poly-
nomials of higher orders and, on the other, to better control
the course of the curves and to maintain the quality of the
prepared standards.
5.6.1 User-concentration method
Up to ten specific user-concentration methods can be entered
and stored. This requires two to 14 standards of known con-
centrations and a zero factor (distilled water or a reagent
blind). The accuracy of the method rises in direct proportion to
the number of standard solutions measured. It is thus advisable
to user five to ten standard concentrations spread equidistantly
over the measuring range. The standards should be measured in
the rising sequence of the concentrations, from the lightest to
the darkest colour. The limits for "Underrange" and "Over-
range" are set at -2600 mAbs* and 2600 mAbs*.
After a user-concentration method is called up, the concentra-
tions of the lowest and highest standards measured are shown
on the display as the measuring-range limits.
In actual fact the lower limit of the measuring range is given
either by the nonlinearity of the calibration function or by the
limit of determination. The limit of determination is the lowest
concentration of an analyte that can be quantitatively deter-
mined with a defined probability (e.g. 99 %). The upper limit of
the measuring range is defined as the point at which there is
no longer any linear correlation between the concentration and
the absorbance. (The exact determination of the actual limits
of the measuring range can be taken from the corresponding
literature references.)
The sample should, where necessary, be diluted to ideally lie in
the middle of the working range (measurement with the lowest
error).
*1000 mAbs = 1 Abs = 1 E
Chapter 5.6 | Page 1 of 13