Introduction
Principle
Matrix detector heads correct refraction differences between rinsing liquid and sample matrix, like sea water with H₂O.
Two wavelengths are measured: one near optimum absorption (Channel A) and one with complementary absorption (Channel B). The correction channel shows more matrix effect than the measurement channel.
Subtracting the correction channel from the measurement channel offsets refractive indexes, with Channel A retaining higher absorption for the color reaction. This reduces matrix effect on 'A - B' while maintaining absorption.
To nullify matrix effects, both channels must experience identical matrix influence, corrected by adding a factor to both channels;
Absorbance = (Factor A * Channel A) – (Factor B * Channel B)
The factor (F) equals the corrected peak height of the measurement channel divided by the corrected peak height of the correction channel.
Result is (A – B), which means (measurement channel – correction channel) the entire formula will be:
( FactorA * A + OffsetA ) Measurement Channel - ( FactorB * B + OffsetB ) Correction Channel
Next, calculate the factor (F) by dividing the Corrected Height of the measurement channel by the corrected height of the correction channel (Figure 10).
Position | Type1 | Corr. Height A | Corr. Height B | Factor |
|---|---|---|---|---|
1 | Peak1 | 33070 | 26140 | 1,27 |
2 | Peak2 | 33800 | 26560 | 1,27 |
3 | Peak3 | 34366 | 26809 | 1,28 |
Figure 10: Manually divided Factor of Channel A and B
Finally open the Matrix settings screen by clicking on the top right icon (Matrix settings) and insert the average factor in place of the correction factor of the correction channel B (Figure 3).
CHECK THE SAME STANDARDS AGAIN, THE BLANKS SHOULD NOW BE EQUAL TO THE BASELINE SINCE THE REFRACTIVE INDEX IS NULLIFIED. MAKE SURE TO CHANGE THE COLOR REAGENT TO MATCH THE METHOD.