Cromatografia de Pigmentos Vegetais

Separação de clorofila e carotenoides usando cromatografia em papel

Qualitative Analysis Intermediate (High School) 60 min ~$8,00

Objetivo

Separar e identificar pigmentos vegetais usando cromatografia em papel, e calcular os valores de Rf para cada pigmento.

Contexto

Paper chromatography separates mixtures based on differential affinity for the stationary phase (paper) and mobile phase (solvent). Plant leaves contain multiple pigments: chlorophyll a (blue-green), chlorophyll b (yellow-green), xanthophylls (yellow), and carotenoids (orange). These pigments have different polarities, causing them to travel different distances up the paper as the solvent front advances.

Avisos de segurança

  • Acetone and petroleum ether are highly flammable — no open flames
  • Work in a well-ventilated area or fume hood
  • Avoid inhaling solvent vapors
  • Petroleum ether is a skin irritant

EPI necessário

goggles gloves lab_coat

Materiais

  • Fresh spinach leaves (5–10 leaves)
    Or other dark green leaves
  • Acetone or isopropanol (50 mL)
    Extraction solvent
  • Petroleum ether (30 mL)
    Chromatography solvent
  • Chromatography paper (2 strips)
    Whatman No. 1 or equivalent
  • Sand (1 teaspoon)
    For grinding

Equipamentos

Mortar and pestle Beaker (250 mL) with watch glass cover Pencil (not pen) Ruler Capillary tube Scissors

Procedimento

1

Grind spinach leaves with a pinch of sand and 5 mL acetone in a mortar until a deep green extract forms.

5 min Acetone is flammable
2

Draw a pencil line 2 cm from the bottom of the chromatography paper. Apply the extract using a capillary tube in a small spot. Let dry and reapply 3–4 times to concentrate.

10 min
3

Pour petroleum ether into the beaker to a depth of about 1 cm. Suspend the paper strip so the origin line is just above the solvent level.

5 min Work in fume hood
4

Cover the beaker with a watch glass and let the solvent rise by capillary action. Do not disturb until the solvent front is 1–2 cm from the top.

25 min
5

Remove the paper, immediately mark the solvent front with pencil. Let dry completely.

5 min
6

Identify the colored bands: carotenoids (orange, highest Rf), xanthophylls (yellow), chlorophyll a (blue-green), chlorophyll b (yellow-green, lowest Rf). Calculate Rf values for each band.

10 min

Resultados esperados

Four or more colored bands should be visible. Carotenoids (orange) travel farthest (Rf ≈ 0.9–0.95). Xanthophylls (yellow) at Rf ≈ 0.7. Chlorophyll a (blue-green) at Rf ≈ 0.5. Chlorophyll b (yellow-green) at Rf ≈ 0.4.

Limpeza

Allow all solvents to evaporate in the fume hood. Dispose of paper in general waste. Clean mortar and pestle thoroughly.

Detalhes

Categoria
Qualitative Analysis
Dificuldade
Intermediate (High School)
Duração
60 min
Custo estimado
$8,00
Passos
6
Materiais
5

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Frequently Asked Questions

What is the objective of Cromatografia de Pigmentos Vegetais?
Separar e identificar pigmentos vegetais usando cromatografia em papel, e calcular os valores de Rf para cada pigmento.
How difficult is Cromatografia de Pigmentos Vegetais?
This experiment is rated as Intermediate (High School). It takes approximately 60 minutes to complete.
What safety precautions are needed for Cromatografia de Pigmentos Vegetais?
Key safety precautions include: Acetone and petroleum ether are highly flammable — no open flames; Work in a well-ventilated area or fume hood; Avoid inhaling solvent vapors.
What materials are needed for Cromatografia de Pigmentos Vegetais?
The main materials required are: Fresh spinach leaves, Acetone or isopropanol, Petroleum ether, Chromatography paper, Sand.
What results should I expect from Cromatografia de Pigmentos Vegetais?
Four or more colored bands should be visible. Carotenoids (orange) travel farthest (Rf ≈ 0.9–0.95). Xanthophylls (yellow) at Rf ≈ 0.7. Chlorophyll a (blue-green) at Rf ≈ 0.5. Chlorophyll b (yellow-green) at Rf ≈ 0.4.