Chromatography 11. In order to maintain the quality of their packaged products,

Question

Chromatography

11. In order to maintain the quality of their packaged products, the Murdoch Tea and Coffee Company regularly conducts HPLC analysis of their raw ingredients to determine the levels of certain antioxidants and the caffeine content. Due to a fault in the HPLC software, results from analyses are being displayed as a data table instead of an easy to read chromatogram (a) Are the peaks for compounds 1 and 2 resolved and show how can you prove your answer? (b) Describe what you could do to reduce the overall analysis time for the analysis? Explain why this approach is likely to work. (c) The above analysis was performed using a C18 column. What is the likely order of elution using a cyano column with a mobile phase composition of 3:1 hexane:ethyl acetate? Explain how you came to your conclusion.

Explanation / Answer

1) We can find the resolved peaks by the following formula, for compound 1 and compound 2

RS=2[(tR)2(tR)1] / W2+W1

Where Rs= resolution

(tR)2= retention time of compound 2 = 11

(tR)1= retention time of compound 1 = 9.5

W2 = Peak width of compound 2 = 0.7

W1= Peak width of compound 1 = 0.35

Rs = 2(11-9.5) / 0.7-0.35 = 3 / 0.35 = 8.57

The peaks are resolved as Rs > 1

2) We can use use a shorter column length.

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