It is important to dry the material because any water or moisture present in the material will add to the weight of the sample, which can lead to an overestimation of the amount of product that we collect. By drying the material, we can remove any water or moisture, which will give us a more accurate measurement of the actual amount of product that we collect. This is particularly important when working with materials that are hygroscopic and readily absorb water from the environment. In addition, the presence of moisture can also affect the purity and composition of the product, which can impact its quality and performance. Therefore, by drying the material before collecting the product, we can ensure that we are obtaining an accurate measurement of the product yield and quality.