Sherwood Scientific Limited
260 91 000
Issue 1
26
th
May 2010
ECN 613
17
Operation
(continued)
6.4 Concentration Methods
As stated, the majority of applications for the Colorimeter will be the
measurement of the concentration of an analyte either by:-
1.
Using a factor supplied by the test kit manufacturer.
2.
Comparison with a calibrator (or “standard”) of known concentration.
In the 260 series colorimeters, these two methods are respectively denoted as:-
1.
Factor Method
2.
Concentration Method
The ‘Method’ section within the Model 260’s Menu allows for methods to be
constructed, saved, recalled and operated for assistance with GLP and SOP
procedures. In addition, these ‘Methods’ allow the operator to enter sample
identifiers (names or numbers) for subsequent sample/result correlation.
Detailed illustration of the ‘Setup’ and “Running” of these method types is given
in Chapter 7 and 8 respectively of the Manual.
6.5 Time Based Measurements
Some measurements, particularly of clinical samples, require time to develop an
absorbing reactant, which then allows the presence of the analyte of interest to be
determined and quantified. These have two categories:-
6.5.1 End-Point Methods
Used when the colour needs time to develop but is then stable for, usually, at least
an hour.
6.5.2 Kinetic Measurements
This Procedure is used, for example, when the analyte is an enzyme which
catalyses a particular reaction. Higher concentrations of the analyte result in faster
rates of reaction. The rate of change of adsorption is calculated having measured
the adsorption at two different times in the constant rate period of the reaction
(pre-determined by the test kit manufacturer).
Both time based measurement types can be made using a known factor or in
comparison to a calibrator (or “Standard”), both supplied by the test kit
manufacturer.
