Caffeine in Various Teas Using Chromatography Methods Analysis Lab Report

Question Description

Professor said, I only expect you to include the caffeine results for the 1st experiment you did. The second draft of the report will include results from both experiments.

Caffeine in Various Teas Using Chromatography Methods Analysis Lab Report
Caffeine in Various Teas Using Chromatography Methods Analysis Lab Report
Caffeine in Various Teas Using Chromatography Methods Analysis Lab Report

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Experiment: Analysis of Caffeine in Various Teas Using Chromatography Methods Investigation: The lab aims to measure the content of caffeine in different types of teas to determine which has the highest and lowest content of caffeine. Background: Caffeine is an important ingredient, also used as a flavoring agent to make drinks addictive. It has the effect of temporarily warding odd drowsiness and restoring alertness. Most experience no behavioral effects with less than 300mg caffeine, sleep is sensitive and can be disrupted by 200mg caffeine. Caffeine is a naturally occurring substance found in the leaves, seeds or fruits of various species. Caffeine is a central nervous system stimulant. Caffeine Content (per eight ounces serving) Black Tea: 40-70 mg Green Tea: 45-35 mg White Tea: 15-30 mg Oolong Tea: 37-55 mg Herbal Tea: None (made from dried flowers, leaves, etc. typically that are caffeine-free) Equipment: ● Magnetic Hot Plate ● Stirring Bar ● Volumetric Flask ● Methanol ● Discovery RP-AmideC1615 cm x 4.6 mm I.D, 5 um particles ● Dipotassium Phosphate ● 1,3,7-trimethylxanthine solid ● Analytical Mass Methodologies: Standard: Pure Caffeine (1,3,7-trimethylxanthine) solid: Standard solutions of 10, 20, 50, 70, 100 mg (1 mg/L = 1 ppm) Standard methods for Concentration: Goal is to use the calibration curve correlation of peak area to absorbance to evaluate the concentration within the tested teas. Sample Prep: For each of the three tea samples, brew each sample tea bag in 250 mL of boiled water. This solution will then be injected via syringe into the HPLC instrument. Liquid Chromatography Phase Technique Flow Rate Detection Injection Mobile Methanol: 25 mM K2HPO4, pH 7.0 1 mL / min UV, 254 nm 10 uL Stationary Discovery RP AmideC1615 cm x 4.6 mm I.D, 5 um particles 1 mL / min UV, 254 nm 10 uL Standard Operating procedure: Turn power to HPLC by pressing the switch behind the main HPLC unit If there are air bubbles… Turn the metal knob to the left on the bottom middle-left of the instrument then press the purge button to purge air from mobile phase line [50% DI water, 50% Methanol]. After the process was done, tighten the knob prior to advancing the system operation Select composition of mobile phase by first pressing “%ABC” then using the cursor, increase, decrease, and select keys modify the compositions of solutions A ( DI water: 75%) and B (Methanol: 25%) with a flow rate of 1 mL/min. Turn on the AD20 Absorbance detector, and set the conditions to “high”, ensure the wavelength is at 254 nm. Turn the metal knob below the lever on the left side of the HPLC to the left. Then press the purge button on the instrument to allow the solutions to be transferred through the absorbance detector. Ensure the injection slot is in the load position and inject sample with the X syringe at capacity Turn the injection valve to inject. The software should start the detection automatically. Wait 1 minute then turn the injection valve to load again and remove the syringe. The software should automatically save the data for each run. Remember to record the file name for the data recording for each runs. ...
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Clari (413)
University of Virginia

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