4: Food Dye Chromatography
- Page ID
- 514166
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- To use paper chromatography to separate and characterize common food dyes by measuring their \(R_f\) values.
- To analyze the dyes extracted from candy coatings and identify them by comparison to known standards.
INTRODUCTION
Most substances we encounter daily are mixtures, not pure compounds. Similarly, chemicals synthesized in laboratories often contain impurities such as reaction byproducts or leftover reactants. Consequently, a significant focus in chemistry is developing methods to separate and identify the components of mixtures.
Many separation techniques exploit physical differences among mixture components. For example, filtration separates substances in different physical states (e.g., solids from liquids), centrifugation uses differences in density, and distillation takes advantage of variations in boiling points. In this experiment, we will use paper chromatography to separate and analyze a mixture of food dyes.
Chromatography techniques involve three key components:
- Analyte: The mixture to be separated.
- Mobile phase: A liquid or gas that carries the analyte through the system.
- Stationary phase: A porous material that interacts with the analyte, slowing its movement.
Separation occurs because components of the mixture interact differently with the stationary phase. Components with stronger interactions move more slowly, while those with weaker interactions move faster, allowing the mixture to separate. These interactions are influenced by specific physical properties and experimental conditions, which can help isolate individual components.
Paper chromatography is a simple type of liquid chromatography that uses paper as the stationary phase. The analyte is applied near the bottom of the paper, which is then placed upright in a tank containing the mobile phase, with the paper’s edge submerged. Capillary action draws the mobile phase up the paper, carrying the analyte. Due to varying interactions with the stationary phase, different components of the mixture travel at different speeds. The separation is complete when the solvent front (the furthest point reached by the mobile phase) nears the top of the paper.
The separation is analyzed by measuring how far each component travels relative to the solvent front. This ratio, the Rf value, is unique for each substance under specific conditions and can be used to identify the components.
In this experiment, you will use paper chromatography to calculate Rf values for common food dyes and analyze the dyes in candy coatings. By comparing Rf values and colors, you will identify the dyes present in the mixtures.
- 4.1: Food Dye Chromatography - Experiment
- This page covers safety precautions for handling food dyes and flammable substances, lists required equipment and chemicals for chromatography, and details an experimental procedure in five parts. These include preparing the developing tank and solutions, applying dye to chromatography paper, and developing the chromatogram. It emphasizes careful measurement and responsible disposal of chemical waste following instructor guidelines.
- 4.2: Food Dye Chromatography - Pre-lab
- This page covers chromatography, detailing the roles of the stationary (fixed material) and mobile phases (solvent). It emphasizes the importance of identifying these phases in laboratory experiments and explains how to calculate the Rf value of various dyes in chromatograms, guiding students to measure and evaluate dye separation efficiency.
- 4.3: Food Dye Chromatography - Data and Report
- This page outlines a data collection method for analyzing standard and M&M dye characteristics through chromatography, detailing measurements of dye and solvent movement. It includes tables for recording data and offers post-lab questions to encourage student reflection on practical aspects of chromatography, such as marking techniques, spot size importance, Rf value range, and solvent front timing considerations.