# Analytical Chemistry - Fluorometric method

(See attached file for full problem description)

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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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https://brainmass.com/chemistry/experimental-design-and-methods-in-chemistry/analytical-chemistry-fluorometric-method-50668

#### Solution Preview

(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.