Factors that affect sample purity

There are also many synthesis-related factors such as temperatures used, solvents, proper drying, and filtration that will affect the purity of your final product.

Even though, preparing a sample for a melting point analysis is not hard, there are some considerations to keep in mind, to avoid having biased measurements:

• The sample has to be dry, as the presence of water will create condensation and influence the reading of the melting point.

• The sample has to be well packed inside the tube. This is usually achieved by tapping the tube with the sample on the working bench. Remember to do it lightly, as the tube is made of glass, be gentle.

• Only 1-3 mm of the sample are required in the tube and if more samples are analyzed, it’s good practice to always use the same amount. Taller samples take extra heat to completely melt and usually display larger melting ranges than their shorter counterparts (and thus are less precise in their readout)

• The open ends of a sample capillary tube must be sealed for crystals that are hygroscopic (to avoid moisture uptake) or that sublimate at high temperatures (to avoid sample loss during testing.

• Ensure that the apparatus is switched on and is pre-heated to near the anticipated starting temp of the sample.