Experiment was HPLC analysis of benzoic acid and caffeine. Do some research and

Question

Experiment was HPLC analysis of benzoic acid and caffeine. Do some research and find two different compounds that could be used as internal standards for this method. Where do you expect them to elute relative to your analytes? Experiment was HPLC analysis of benzoic acid and caffeine. Do some research and find two different compounds that could be used as internal standards for this method. Where do you expect them to elute relative to your analytes? Experiment was HPLC analysis of benzoic acid and caffeine. Do some research and find two different compounds that could be used as internal standards for this method. Where do you expect them to elute relative to your analytes?

Explanation / Answer

A mobile phase was prepared with a ratio of 60/40 methanol/water. All solutions were prepared using HPLC grade solvents. Sodium phosphate was added as a buffer and the solution adjusted to a pH of 5.0.Solid benzoic acid is dissolved in the mobile phase to a concentration of 1100 ppm and degassed to prepare a stock standard solution, then stored and chilled at 1.8oC. Concentrations of 22, 44, 66, 88, and 110 ppm were diluted from the original sample mixture.

Caffeine was extracted from Vivarin tablets by the process of recrystallization. The tablets were dissolved in hot isopropyl alcohol and gravity filtered to remove insoluble impurities

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