Part IV. Optimizing the Solvent, Temperature, and Microwave Power

Investigation 17: Optimizing the Microwave Power (Part A)

In Investigation 16, we found that the optimum temperature is 70°C when using a solvent that is 80% methanol and 20% water (by volume) to extract a 3.00-g sample of Danshen for 5.00 min using 60.0 mL of solvent and a microwave power of 800 W. Next, we turn our attention to optimizing the microwave's power.

In a microwave extraction, temperature is controlled by applying short pulses of microwave radiation. The length of the applied pulse depends on the microwave's power, with a greater microwave power requiring shorter pulses to maintain the temperature. An increase in microwave power can improve extraction efficiency by increasing the breakdown of plant tissue, or it can decrease extraction efficiency by causing localized overheating of samples.

Investigation 17. Propose a set of experiments that will effectively and efficiently allow you to optimize the microwave power using the solvent and temperature selected in Investigation 16. What range of microwave powers will you explore given that the power is adjustable between the limits of 0 W and 1000 W? How many samples will you run? Explain the reasons for the range of microwave powers and the number of samples you selected.