Análise Espectrofotométrica de uma Mistura

Resolução de uma mistura de dois componentes usando equações simultâneas

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

Objetivo

Determinar as concentrações individuais de dois corantes em uma solução mista usando medições de absorbância em dois comprimentos de onda e equações simultâneas.

Contexto

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.

Avisos de segurança

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

EPI necessário

goggles lab_coat

Materiais

  • 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)

Equipamentos

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

Procedimento

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.

Limpeza

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

Detalhes

Categoria
Colorimetry
Dificuldade
Advanced (University)
Duração
75 min
Custo estimado
$12,00
Passos
7
Materiais
4

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Frequently Asked Questions

What is the objective of Análise Espectrofotométrica de uma Mistura?
Determinar as concentrações individuais de dois corantes em uma solução mista usando medições de absorbância em dois comprimentos de onda e equações simultâneas.
How difficult is Análise Espectrofotométrica de uma Mistura?
This experiment is rated as Advanced (University). It takes approximately 75 minutes to complete.
What safety precautions are needed for Análise Espectrofotométrica de uma Mistura?
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 Análise Espectrofotométrica de uma Mistura?
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 Análise Espectrofotométrica de uma Mistura?
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.