Análisis Espectrofotométrico de una Mezcla

Resolución de una mezcla de dos componentes usando ecuaciones simultáneas

Colorimetry Advanced (University) 75 min ~$12,00

Objetivo

Determinar las concentraciones individuales de dos colorantes en una solución mixta usando mediciones de absorbancia a dos longitudes de onda y ecuaciones simultáneas.

Antecedentes

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.

Advertencias de seguridad

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

EPP requerido

goggles lab_coat

Materiales

  • 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)

Equipamiento

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

Procedimiento

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

Resultados esperados

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.

Limpieza

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

Detalles

Categoría
Colorimetry
Dificultad
Advanced (University)
Duración
75 min
Costo estimado
$12,00
Pasos
7
Materiales
4

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Frequently Asked Questions

What is the objective of Análisis Espectrofotométrico de una Mezcla?
Determinar las concentraciones individuales de dos colorantes en una solución mixta usando mediciones de absorbancia a dos longitudes de onda y ecuaciones simultáneas.
How difficult is Análisis Espectrofotométrico de una Mezcla?
This experiment is rated as Advanced (University). It takes approximately 75 minutes to complete.
What safety precautions are needed for Análisis Espectrofotométrico de una Mezcla?
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 Análisis Espectrofotométrico de una Mezcla?
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 Análisis Espectrofotométrico de una Mezcla?
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.