A = logāā(Iā/I) = Īµ ā cA: without unit; Īµ: LĀ·molā»Ā¹Ā·cmā»Ā¹ ; ā: cm ; c: mol/L.
Use when: Monochromatic absorption, homogeneous medium, adapted linear domain.
Instrumental analysis
Understand the signal, calibration and determination of a concentration.
What is happening?
A device transforms a physical interaction into a measurable signal. UV-visible and colorimetry exploit absorption; ICP-OES measures atomic emissions, atomic absorption an absorption of free atoms, and XRF an X-ray fluorescence.
A calibration line links signal and concentration in a validated domain. The white, the interferences and the matrix condition the quality of the result: the BeerāLambert law does not describe all these devices indiscriminately.
The formulas, with their conditions.
S = a c + b ; c = (S ā b)/aS: signal; a: sensitivity; b: ordered to lāorigin.
Use when: Interpolation in the calibrated range; control the blank and the matrix.
Where is this principle used?
Mining laboratory
Measure elemental contents in solutions and prepared solids.
Pharmaceutical or water treatment plant
Check the composition and traces of impurities.
What to observe in the experiment
Calibrate with multiple concentrations, then measure an unknown within the range. Check the effect of a poorly corrected blank.
References and readings
This sheet explains the principles and their assumptions. Educational simulation can simplify the process; an industrial model requires suitable data and validation.
Have you understood the essentials?
Only one correct answer per question. Answer all three questions, then view the answer key.
Intu Lab Ā· Understanding sheet Ā· Kimba Christian