Determination of Food Additives in a Beverage (Lab Report)

Determination of Food Additives in a Beverage (Lab Report)

Format of a lab report

• Abstract
• Introduction
• Results
• Discussion
• Conclusions
• References

Determination Of Food Additives In A Beverage

OUTLINE OF EXPERIMENT

Many food additives absorb radiation in the ultraviolet and/or visible region of the spectrum. This absorbance can be used to determine the concentration of an additive in a sample using external calibration (Tutorial topics 2 & 3).

However, additives may occur together and the absorbance by one could interfere with the absorbance of another.

A prior separation stage is necessary and the additives are first separated by High Performance Liquid Chromatography (HPLC) and then determined on-line using a UV and/or visible detector.

In this practical you will be analysing a beverage for the presence of four additives:

Tartrazine   (yellow colouring)

Saccharin     (artifical sweetener)

Vanillin        (flavouring)

Caffeine       (stimulant)

There are two stages to this practical:

• In the first part you will find out about the absorptiometric properties of each of the food additives.
• In the second part, you will separate a mixture of the additives by HPLC and quantify using an ultraviolet/visible detector.

AIMS OF THE EXPERIMENT

• To determine the wavelength of maximum absorbance and A(1% 1cm) for each of four food additives (tartrazine, saccharin, vanillin and caffeine).
• To select a wavelength at which all 4 compounds absorb, with a sensitivity suitable for the HPLC detector
• To quantify for each additive in a mixture using HPLC with UV/Vis detection and external calibration.
• To assess the separating power and the efficiency of the HPLC column for each of the four additives.

INTRODUCTION SECTION 20% – these are questions to be answered in the introduction – one whole page

• Why do some substances absorb ultraviolet and/or visible light
• What are the structures of these additives?
• What is the Beer-Lambert Law?
• What we mean by molar absorptivity and A(1%1cm)
• Why can these additives be separated by reverse phase by HPLC?
• How do we quantify for components separated by HPLC?
• How is resolution measured?
• How is the efficiency of the column for each component determined?
• What are the aims of the investigation?

 RESULTS 25%

The yellow highlighted areas in the method section are supposed to be calculated – please show working out

Tabulate all of your results clearly. Include the absorbance spectra and the HPLC chromatograms (I have done that already). Make sure that all tables and figures are fully labelled. Cross reference from tables to figures (in discussion section) e.g. “the data given in Table 4 is shown graphically in Figure 2”.

DISCUSSION 30%

Questions that you could address in your discussion:

• Are the graphs linear?
• Is there scatter about the line and error in plotting the best-fit?
• Is the Beer-Lambert Law obeyed?
  • Over what concentration range?
• What other sources of error are there?
• How accurate is the glassware?
• How could you improve precision (repeatability)?
• Did you have any problems during the experiment?
• Are there any improvements that you would like to suggest

CONCLUSIONS

State these clearly

• Re-address the aims of the experiment.
• Have the aims been met?
• Clearly state the result for each aim.