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Analytical Chemistry - Fluorometric method

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23. In developing a fluorometric method, you measure a standard Analyte at 3.00 ppm (w/w) in the matrix at three different pH values: 2,5,8. You then compare the effects of internal calibration by adding 2.00ppm Analyte to your matrix vs external calibration via pure standards and obtain the following data

pH= 2 Slope=2607
Intercept = 3466
Measured signal for 3.00ppm standard =12781
Signal after 2.00ppm spike =15611

pH= 5 Slope=2651
Intercept = 1232
Measured signal for 3.00ppm standard =9215
Signal after 2.00ppm spike =14503

pH= 8 Slope=434
Intercept = 1156
Measured signal for 3.00ppm standard =2205
Signal after 2.00ppm spike =2920
A) Derive the equations needed to solve the concentration from i) the straight line equation, y=mx+b and the measured signal 'S' for the external and ii) the data points (0,Ssignal), and (Cspike, Ssignal+spike).
B) Determine which pH condition has (I) little influence from the matrix, (II) decreased signal because of the matrix, and (III) false enhancement of signal from the matrix. Be sure to subtract the background signal!
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(A) At PH = 2
m = 2607, b=3466
y=mx+b
y= 2607x + 3466
y - 3466 = 2607x
x = (y - 3466)/2607

At PH = 5
m = 2651, ...

Solution Summary

A question involving the fluorometric method and the measure of a standard Analyte.

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