Instrumental Analysis
Essay by Nida Khan • February 8, 2016 • Lab Report • 649 Words (3 Pages) • 1,067 Views
HPLC
By: Steven Parra, Lab Partner: Leo Garbar.
Completed on 11/15/10, Due 11/29/10.
Introduction:
High performance liquid chromatography is a useful analytical tool that allows for the separation, identification, and quantification of many different organic compounds. A HPLC system consists of a column that is filled with a stationary phase that can be ether polar or non-polar. This stationary phase is attractive to what is being passed through the column in the mobile phase. The retention time is the amount of time it takes the sample to run through the column, different compounds will have different retention times and therefore the identity of the compound of can be determined. Changes to the mobile phase as well as stationary phase will allow the separation of compounds even if they elute at the same times.
Objective:
To determine the amount of additives in diet soda and energy drinks by HPLC. To determine the amount of caffine in teas. To determine the parameters that affects the separation of compounds by HPLC. To use propagation of error to determine accuracy of prepared standards.
Equipment:
ThermoFisher Modular Spectra HPLC system, ChromeQuest 5.0 software to control instrument, Rheodyne Injection valve with 20-L loop, Xterra RP 18 column.
Reagents:
Methanol CAS #: 67-56-1
Caffine CAS #: 58-08-2
Benzoic acid CAS #: 65-85-0
Acetaminophen CAS #: 103-90-2
Acetic acid CAS #: 64-19-7
Acetylsalicylic acid CAS #: 50-78-2
I have read and understand the MSDS sheets for these compounds.
Chemical Reactions:
None.
Data:
Chromatograph for Black tea
[pic 1]
Chromatograph for green tea
[pic 2]
Chromatograph for Energy drink
[pic 3]
Chromatograph for Diet Soda
[pic 4]
Table of data for runs.
Sample | Retention time for caffeine (min) | Retention time for benzoic acid (min) | Peak area caffeine | Peak area Benzoic acid | W(1/2) Caffine | W(1/2) Benzoic acid |
Energy drink | 2.24 | 7.45 | 906010 | 140146 | 532947 | 82438 |
Diet soda | 2.23 | 7.42 | 1264931 | 1474130 | 744077 | 867135 |
Green tea | 2.29 | 7.47 | 1257888 | 2603 | 739934 | 1531 |
Black tea | 2.25 | 7.39 | 1930710 | 47758 | 1135711 | 28092 |
Table of values for sample runs
standard | Retention time | Peak area | Capacity factor (k) | Height of plates (H) | Number of plates (N) | Selectivity factor (α) |
Caffeine | 2.25 | 2500942 | 1.009 | 1.13x1013 | 1.29x10-11 | 3.33 |
Benzoic acid | 7.50 | 369411 | 5.69 | 2.27x1010 | 6.59x10-9 | .3 |
[pic 5]
Graph of benzoic acid standard.
[pic 6]
[pic 7]
Graphs provided courtesy of Dr. Hall.
Diet soda sample
Sample name | Caffeine Conc. (ppm) | Caffeine Conc. (mg/L) | Benzoic acid Conc. (ppm) | Benzoic acid Conc. (mg/L) |
Coca-Cola brand: Diet Coke | 125.73 | 125.73 | 437.00 | 437.00 |
Energy drink sample
Sample name | Caffeine Conc. (ppm) | Caffeine Conc. (mg/L) | Benzoic acid Conc. (ppm) | Benzoic acid Conc. (mg/L) |
FRS Healthy energy | 89.81 | 89.81 | 36.45 | 36.45 |
Amount of caffeine in the green and black teas
Sample | Caffeine Conc. (ppm) | Total mass of caffeine per tea bag (%) |
Nestlé green tea | 249.33 | 2.05 |
Lipton black tea | 192.31 | 1.26 |
Caffeine and Benzoic acids formula and interactions when being passed through the HPLC column.
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