Спектрофотометрический анализ смеси

Разделение двухкомпонентной смеси с помощью системы одновременных уравнений

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

Цель

Определить индивидуальные концентрации двух красителей в смешанном растворе, используя измерения поглощения на двух длинах волн и систему одновременных уравнений.

Предпосылки

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.

Предупреждения по безопасности

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

Требуемые СИЗ

goggles lab_coat

Материалы

  • 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)

Оборудование

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

Процедура

1

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

8 мин
2

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

7 мин
3

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

15 мин
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 мин
5

Measure the absorbance of the unknown mixture at both wavelengths.

5 мин
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 мин
7

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

10 мин

Ожидаемые результаты

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.

Уборка

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

Детали

Категория
Colorimetry
Сложность
Advanced (University)
Продолжительность
75 мин
Прим. стоимость
$12,00
Шаги
7
Материалы
4

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Frequently Asked Questions

What is the objective of Спектрофотометрический анализ смеси?
Определить индивидуальные концентрации двух красителей в смешанном растворе, используя измерения поглощения на двух длинах волн и систему одновременных уравнений.
How difficult is Спектрофотометрический анализ смеси?
This experiment is rated as Advanced (University). It takes approximately 75 minutes to complete.
What safety precautions are needed for Спектрофотометрический анализ смеси?
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 Спектрофотометрический анализ смеси?
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 Спектрофотометрический анализ смеси?
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.