Liquid Chromatography Lab Report

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Name :SiphesihleGamede
Student number : 213571124
Experiment : #10
Date : 4 March 2015
Experiment Name : High Performance Liquid Chromatography (HPLC), Quantification of caffeine in various drinks

Aim
The aim of this experiment was to ascertain the concentration levels of caffeine in cola soft drink samples such as coke, monster and red bull by utilising the internal standard method using HPLC. The experiment was also aimed at investigating the use of solid phase extraction for sample clean-up.

Figure 1.1 shows a skematic diagram of an HPLC system. Figure 1.2 shows a skematic diagram of a solid phase extraction system.

Introductory Questions
Define SPE and explain the role of each of the steps used to prepare the SPE cartridge for the isolation of the analyte.
Solid phase extraction (SPE) is an extraction method that uses a liquid and solid phase to isolate a single analyte or a specific type of analyte from a solution. It is usually used to clean up a sample before using a chromatographic or other analytical method to quantify the amount of analyte(s) in the sample.
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One of the reasons why SPE is a suitable technique for this analysis is the fact that there should be higher recoveries (% recoveries)since both caffeine and theophylline are polar compounds, with theophylline being more polar than caffeine which tells us that caffeine will have the longer retention time than theophylline. Other reasons include advantages such as SPE provides cleaner extracts and is easier to automate compared to other extraction…show more content…
There is a mathematical treatment called the ‘Fourier transformation’ and it is used to produce a spectrum and to interpret the data, hence the name FTIR spectroscopy. In general, infrared spectroscopy measures the ability of certain molecules to absorb infrared radiation. The radiation beam passes through a sample and then through a detector where the signal being produced is a function of optical path difference called an interferogram. The design of the FTIR is in such a way as to allow the use of capillary columns which produce sharper

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