Spektrophotometrische Analyse eines Gemisches

Auflösung eines Zweikomponentengemisches mittels simultaner Gleichungen

Colorimetry Advanced (University) 75 Min. ~$12,00

Ziel

Die Einzelkonzentrationen zweier Farbstoffe in einer gemischten Lösung durch Absorptionsmessungen bei zwei Wellenlängen und simultane Gleichungen bestimmen.

Hintergrund

When a solution contains two absorbing species with overlapping spectra, a single wavelength measurement cannot determine both concentrations. However, by measuring absorbance at two wavelengths (ideally the λmax of each component) and applying the additive property of absorbance (Beer-Lambert), a system of two simultaneous equations can be solved. This technique is the basis of multicomponent analysis in spectrophotometry.

Sicherheitswarnungen

  • Indicator dyes stain clothing
  • Handle cuvettes by frosted sides only to avoid fingerprints
  • Clean spills immediately

Erforderliche PSA

goggles lab_coat

Materialien

  • Methyl orange solution (0.01%) (100 mL)
    Component A
  • Bromothymol blue solution (0.01%) (100 mL)
    Component B
  • Unknown mixture of both dyes (50 mL)
    Prepared by instructor
  • Distilled water (200 mL)

Ausrüstung

UV-Vis spectrophotometer Cuvettes (matched pair) Volumetric flasks (50 mL, 6 total) Pipettes Calculator

Durchführung

1

Scan pure methyl orange from 350–700 nm. Record λmax (approximately 464 nm in acidic pH).

8 Min.
2

Scan pure bromothymol blue from 350–700 nm. Record λmax (approximately 615 nm at neutral pH).

7 Min.
3

Prepare 3 standard concentrations of each pure dye. Measure absorbance of each at both λmax values (464 and 615 nm).

15 Min.
4

Calculate the molar absorptivity (ε) for each dye at each wavelength from the standard curves: ε(A,464), ε(A,615), ε(B,464), ε(B,615).

15 Min.
5

Measure the absorbance of the unknown mixture at both wavelengths.

5 Min.
6

Set up the simultaneous equations: A(464) = ε(A,464)·C(A) + ε(B,464)·C(B), A(615) = ε(A,615)·C(A) + ε(B,615)·C(B). Solve for C(A) and C(B).

15 Min.
7

Verify your results by comparing the calculated total absorbance at several wavelengths with the measured mixture spectrum.

10 Min.

Erwartete Ergebnisse

The simultaneous equations yield positive concentrations for both dyes. The reconstructed spectrum (sum of individual contributions) should closely match the measured mixture spectrum, validating the Beer-Lambert additivity principle.

Aufräumen

Pour dilute dye solutions down the drain with running water. Rinse all cuvettes and volumetric flasks thoroughly.

Details

Kategorie
Colorimetry
Schwierigkeit
Advanced (University)
Dauer
75 Min.
Geschätzte Kosten
$12,00
Schritte
7
Materialien
4

Weitere Experimente

Analyse von Lebensmittelfarben durch Spektrophotometrie 60 min Eisenbestimmung in Wasser 75 min Kolorimetrische Glucosebestimmung 60 min Kolorimetrische Phosphatbestimmung 90 min Kolorimetrischer Proteintest (Bradford-Methode) 60 min Spektrophotometrische Bestimmung von Aspirin 75 min Verifikation des Lambert-Beer'schen Gesetzes 60 min

Frequently Asked Questions

What is the objective of Spektrophotometrische Analyse eines Gemisches?
Die Einzelkonzentrationen zweier Farbstoffe in einer gemischten Lösung durch Absorptionsmessungen bei zwei Wellenlängen und simultane Gleichungen bestimmen.
How difficult is Spektrophotometrische Analyse eines Gemisches?
This experiment is rated as Advanced (University). It takes approximately 75 minutes to complete.
What safety precautions are needed for Spektrophotometrische Analyse eines Gemisches?
Key safety precautions include: Indicator dyes stain clothing; Handle cuvettes by frosted sides only to avoid fingerprints; Clean spills immediately.
What materials are needed for Spektrophotometrische Analyse eines Gemisches?
The main materials required are: Methyl orange solution (0.01%), Bromothymol blue solution (0.01%), Unknown mixture of both dyes, Distilled water.
What results should I expect from Spektrophotometrische Analyse eines Gemisches?
The simultaneous equations yield positive concentrations for both dyes. The reconstructed spectrum (sum of individual contributions) should closely match the measured mixture spectrum, validating the Beer-Lambert additivity principle.