Hitachi U-5100 Instruction Manual page 81

Explanation 3-3 How to Set 6-cell Measurement Parameters without
Standard solution
Analyte of interest
Solvent
Cell
<1> <2>
STD1 STD2
Elements causing absorbance without using coloring reagent (not containing interfering substance)
A measured absorbance value is given as a total of absorptions due to various elements (cell,
solvent, coloring reagent, analyte of interest, interfering substance). In other words, this value
does not simply stand for an absorption due to the analyte alone.
For generating a calibration curve according to concentration levels 0, 1 and 2, solutions of
concentration levels 0, 1 and 2 are prepared for STD1, STD2 and STD3, respectively (see <1> to
<3> in the above figure). These STD's have absorptions due to cell, solvent and analyte.
However, the absorbance required for actual quantitation is the one deriving from the analyte.
Therefore, absorptions due to cell and solvent need to be subtracted (by auto zero operation).
In this case, auto zero is carried out with STD 1 and the absorbance values of STD1 to STD3 are
measured, thereby generating a calibration curve.
And, for sample quantitation, the concentration of the sample is determined using the absorbance
after exclusion of cell and solvent. When the absorption other than those due to cell and solvent
derives from the analyte alone, the determined concentration equals the concentration of the
analyte as illustrated at <4> in the above figure. For quantitation of this sample with 6 Cell Mode
set to Auto, the STD Autozero, SAMP. Autozero and Thru Zero are set to STD1, ON or OFF and
ON, respectively. (Refer to the measurement parameters in "A" of the following table.)
Standard solution
Analyte of interest
Solvent
Cell
<1> <2>
STD1 STD2
Elements causing absorbance without using coloring reagent (containing interfering substance)
Coloring Reagent
<3>
STD3
Interfering
substance
<3> <5>
STD3 Blank test
Solution
3 - 17
Sample solution
Absorbance of analyte
Absorbance-zero line by
auto zero with <1>
<4>
Sample
Sample solution
Absorbance of analyte
Absorbance-zero line by
auto zero with <5>
Absorbance-zero line by
auto zero with <1>
<4>
Sample
(interfering substance contained)
3.2.1