+1 862 207 3288 Virtual Lab Experiment
Chocolate is a popular snack throughout South America, North America and Europe. In addition to its high energy content (33% fat and 47% sugar)
chocolate packs an extra punch with the stimulant caffeine and its biochemical precursor theobromine. Theobromine comes from the Greek word meaning
“food of the gods” and it is a diuretic, smooth muscle relaxant, cardiac stimulant, and vasodilator. Caffeine is a central nervous system stimulant.
Too much caffeine is harmful for many people, and in a small fraction of the population even small amounts of caffeine cannot be tolerated. How much
caffeine is in a chocolate anyway? And how does that amount of caffeine compare with the amount of caffeine found in a cup of regular coffee?
For this thought experiment you will design an analytical chemistry method using equipment and reagents selected from a master list (see below). The
goal is to determine the amount of caffeine in a regular size chocolate bar and an 8 oz. cup of coffee. The second goal is to determine if coffee
and chocolate have the same amount of caffeine per serving or not. You need to describe in detail the following:
1. A hypothesis
2. A very detailed step-by-step experimental protocol that includes chemical standards and calibration curves to measure the amount of caffeine
& theobromine in the samples. The experiment is designed using some (not all!) reagents and equipment provided in the master list below.
3. Two fictitious data sets (one for a chocolate bar and one for coffee) which you decide will either support or refute your hypothesis
4. Statistical analysis of the fictitious data
5. A clear, balanced conclusion
Master List of reagents and equipment
Lab notebook, pen (not pencil!) and scotch tape
Computer running Windows 7 with Microsoft Excel 2010 and Microsoft Word 2010
1 regular sized dark chocolate bar
1 8 oz. cup of regular brew coffee
Ceramic mortar and pestle
Blender
Fridge
Freezer
Electronic analytical balance capable of measuring mass down to 0.10 mg
5, 10, 25, 50 and 100 mL burets
1,2,5,10,25,50,100,200,250,500,1000, & 2000 mL volumetric flasks
0.2-2, 1-10, 2.5-25, 10-100, & 100-1000 uL adjustable micropipette with matching disposable tips
1,10,50,100 & 500 uL Hamilton syringes
Fritted-glass funnel with electronic air pump
Conical funnel and filter paper
Syringes and 0.45 micrometer filter
50, 100, 500 & 1000 mL beakers
50,100,500, & 1000 mL Erlenmeyer flasks
Vacuum desiccator
A copious supply of tap water
A copious supply of double distilled water
Hot plate
Pure standard of 50% caffeine (w/v) in water
Pure standard of 50% theobromine (w/v) in water
500 mL container of petroleum ether
Centrifuge with disposable centrifuge tubes
Chromatography pump with UV detector
SiO2 solid phase matrix column
C18 solid phase matrix column
Sephadex G-10 size exclusion column; Sephadex G-25 size exclusion column; Sephadex G-50 size exclusion column; Sephadex G-100 size exclusion column
chromatography column packed with anti-caffeine antibody coated beads
acidic solvent (79 ml water: 20 ml methanol: 1 ml acetic acid)
basic solvent (79 ml water:20 ml methanol: 1 ml NaOH)
phosphate buffered saline, pH = 7.4
Of course you may use the internet and primary literature to help you design your scientific protocol. Your major challenge is taking the time and
mental effort to address every aspect of the experiment that you can – try to anticipate potential challenges, inefficiencies, sample loss, and loss
of analyte. The more detailed and comprehensive you are in your description the better.
Don’t underestimate the fictitious data set you are going to generate for this project. Based on your internet research you need to make the data
realistic. Once you have the data you are going to need to use Excel to do statistical analysis. You will also need to be cognizant of the number
of significant digits. Don’t forget to show standard deviations for your mean values and explain to me the rationale you used to decide which
statistical method was best for comparing the chocolate vs. the coffee data.
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Virtual Lab Experiment (75 points):
Students will be given the challenge of designing an experimental pathway to isolate and quantify the amount of analyte in two (perhaps more) complex
mixtures in order to test a scientific hypothesis. The student plays the role of experimenter to build the experiment from the ground up. This is a
thought experiment. The goal is to learn how to mentally work through the steps in designing a useful experiment, well before any physical work is
done. The benefits of thinking ahead include saving the experimenter time and energy, and staying within the budget of the laboratory. The student
will be given the following tools: 1) a working hypothesis, 2) the conclusion that the data shows a significant difference from the null hypothesis,
and 3) an extensive list of reagents, methods and equipment. The goal is to learn how to: 1) design a relevant experiment, 2) describe in a stepwise
manner a detailed path to implement the experiment with some of the listed reagents, methods and equipment, and 3) describe the expected appearance
of the results (data) that would justify the non-null conclusion. A one page background (with at least 3 references) to put this experiment into
context is also required.
The length of the Virtual Lab Experiment should be at least 5 pages, 12 pt font, double spaced with one inch margins on each side; lists, tables,
and simple diagrams are encouraged.
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