Experiment 46 The Quantitative Determination of Methyl Paraben in a Prepared Sample by HPLC

Experiment 46 The Quantitative Determination of Methyl Paraben in a Prepared Sample by HPLC 

Part A Determination of the Optimum Mobile Phase Composition 

Mobile phase compositions for this experiment are polar methanol-water mixtures in the ratios 90/10, 80/20, and 70/30 by volume. The stationary phase is C18. Prepare 200 mL of each mobile phase and then filter and degas each through 0.45-/./m filters with the aid of a vacuum (instructor will demonstrate). Slowly pour each (so as to avoid reaeration by splashing) into individual mobile phase reservoirs that are labeled appropriately. 

Obtain the sample from your instructor and filter it into a small vial using a syringe filter (instructor may choose to demonstrate). The sample is a solution of methyl, propyl, and butyl paraben in methanol. Record any identifying label in your notebook. 

Examine the HPLC instrument to which you are assigned. Find the inlet line to the pump and place the free end of this line in the reservoir containing the mobile phase with the 90/10 composition. Trace the path of the mobile phase from the reservoir, through the pump, injection valve, column, and detector, to the waste container so that you identify and recognize all components of the flow path. Turn on the pump and detector and begin pumping the mobile phase at a rate 

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