Chem R&E-Final Presentation
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Transcript of Chem R&E-Final Presentation
Observing the Effect of Polarity in the Separation of
Pigments Anish PrasannaJeremy RubinAradhana Vyas
Block A
Background
● Used to separate mixtures
● Multiple types
● Developed in the early 1900s
Problem
● Determine the best isopropyl alcohol to water ratio
● Polarity-chromatographic separation relationship
Why our project is important
● Chlorophyll often hides other pigments
● Is a sensitive method of detection
● Forensic Science
Paper Chromatography Introduction
● Chloroplast Pigments○ Chlorophyll a and b○ Anthocyanin○ Carotenoids
● Chromatographic Separation
http://chemwiki.ucdavis.edu/Analytical_Chemistry/Instrumental_Analysis/Chromatography
Basic Chromatography Terms
● Mobile Phase
● Stationary Phase
● Band Broadening Theory
● Solvent○ Solvent Front○ Solution
http://cellbiologyolm.stevegallik.org/aminoacids/page4
Basic Chemistry
● Molecular Polarity○ Hydrogen Bonding○ Dipole-Dipole Forces○ Dispersion Forces
● Solubility● Capillary Action● Cohesion/Adhesion
http://www.science.uwaterloo.ca/~cchieh/cact/c123/intermol.html
Ion Dipole H Bond Dipole- Dipole
Hexane Dipole- Induced Dipole Dispersion
Chemistry-Van Deemter Equation
● H=A+B/u+Cu○ Measures efficiency of chromatographic
separation○ H=Plate Height○ u=Velocity of Mobile Phase○ A=Eddy Diffusion○ B/u=Longitudinal Diffusion○ Cu=Mass Transfer
http://chemwiki.ucdavis.edu/Analytical_Chemistry/Instrumental_Analysis/Chromatography
Hypothesis and Null Hypothesis
● Hypothesis○ 3:1 solution will provide best separation
■ Isopropyl alcohol-greatest dispersion forces
■ Lowest polarity■ Polar compounds-short distances ■ Nonpolar compounds-long distances
● Null Hypothesis○ No relationship or relevance between
polarity and separation of pigments
Independent and Dependent Variables
Independent Variable● Ratio of 1 M isopropyl alcohol to 1 M water
○ 1:1○ 3:1○ 3:2
Dependent Variable● R(f) values of each pigment
○ no units● Number of pigments
Red Leaf Extract-Control
● Used as a standard
● Helped determine procedure
● Data collection
Materials Per Trial
● 3 test tubes● 3 mL of cranberry extract● 3 strips of chromatography paper ● Pipette and pipette pump● 18.5 mL 1 M C3H8O● 11.5 mL 1 M H2O● Parafilm● Pencil● 3 50 mL Erlenmeyer Flasks● Ruler
Experimental Setup
● Preparation of Isopropyl Alcohol/Water Solvent
● Preparation of Chromatogram
● Data Collection R(f)
Determining the Color of Anthocyanin
Done through the Dynamic Model (STELLA)
Total Data Collected
● Cranberry Extract○ 10 trials 1:1 ratio○ 11 trials 3:1 ratio○ 9 trials 3:2 ratio
● Red Leaf Extract (Control)○ 4 trials 1:1 ratio○ 2 trials 3:1 ratio○ 5 trials 3:2 ratio
Sample Calculation R(f) Value
● Distance traveled by solvent front d(s)=10.7● Distance traveled by compound d(c)=8.0036
○ R(f)=d(c)/d(s)■ =8.0036/10.7■ =0.748
● Average Pigments per chromatogram● Difference in R(f) values between pigments
○ Calculated through median and difference functions
Data Represented Through Median ● Average number of pigments per ratio
(median)● Average R(f) value of pigment number
(median)
Average Number of Pigments per Chromatogram
Difference in R(f) Values Between Pigments (Cranberry)
Difference in R(f) Values Between Pigments (Red Leaf)
Data Analysis
● Trends○ 3:2 ratio solvent resolved most pigments○ Red leaf extract separated more pigments
than cranberry extract○ Pigments 1 and 2 have greatest difference
in R(f) values ○ 3:2 ratio created largest differences in R(f)
values between chloroplast pigments
Problems Encountered
● Recording R(f) values from a chromatogram○ Distinguishing between two bands
○ Determining bands
○ Determining the furthest extent of the solvent front
● Determining when a chromatogram is finished○ Remaining solvent
How Problems Were Overcome
● Define standards for measuring R(f) values○ Measure to center of color band○ Solvent front-wetness of chromatogram○ Bands-variation in color
● Excess solvent in tubes-wait ten minutes for notable changes
Conclusions
○ 3:2 solvent mixture provided the most effective separation■ Largest difference in R(f) values■ Most pigments separated on chromatogram
○ Hypothesis is refuted○ Relationship between polarity and
chromatographic separation■ As the ratio of dispersion forces and dipole-
dipole becomes closer, the greater the separation of pigments
Future Improvements
● Create extract
● More trials
● Producing clearer results○ UV lamp○ Spectrophotometer ○ Longer chromatograms
Questions
● What are three of the most common pigments in plants?
● How does the polarity of the pigments determine how far they will travel up the chromatogram?
● By looking at the R(f) values of each pigment, how do you know when effective separation has been achieved?