MT2-Sp10-HPLC only - Schematics of the molecules used in...

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Name__________________ GSI ____________________ Page 7 of 8 Question 5) HPLC of Food Dyes Synthetic food dyes are cheap and very colorful, however some are irritating to the eyes and throat and others may even cause cancer. For this reason it is important to develop methods for analyzing the presence and concentration of dyes in food. Two HPLC methods are compared that both work well for the analysis of the food dyes. Method Stationary Phase Mobile Phase 1 Silica-C18 Phosphate buffer in H 2 O, Triton-X (soap) isocratic 2 Silica-C18 Methanol:Acetic Acid Buffer Gradient 10%-40% Methanol a) Of the two methods, which do you think is more green or environmentally friendly? Briefly explain. Examine the structures on the next page. The dye molecules are all ionic compounds with acid-base properties, similar to NaEDTA. Examine the chromatograms and resolution data with varying pH.
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Unformatted text preview: Schematics of the molecules used in Method 2 are shown below. The soap in the mobile phase forms a micelle around the dye molecules. Stationary phase particles Dye in water at pH7 Dye-soap complex b) At low pH the separation is very poor but raising the pH to ~7 helps the compounds to stick to the mobile phase. Please explain in terms of the structures above. c) Examine the flow rate data. The compounds separate quickly at a flow rate of 2 mL/min. The experimenters chose 1 mL/min for all the experiments. Why is this flow rate best? SiO 2 Dye Dye-2 Name__________________ GSI ____________________ Page 8 of 8 Data for the separation of food dyes. Dye Molecules order of elution: (1-tartrazine, 2-brilliant blue, 3-sunset yellow)...
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MT2-Sp10-HPLC only - Schematics of the molecules used in...

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