Solvent removal is a very time consuming step in sample preparation, especially when completed by hand. Sacrificing hours on end holding a stream of nitrogen to a sample, one-by-one can have many negative effects on a production lab, leading to a considerable domino effect. The longer it takes to evaporate batches of samples, the less material a lab is able to process. The less material a lab processes leads to a decrease in productivity and throughput. This decrease in productivity leads to a decrease in profits. All the while, employees are dealing with frustration and a lack of job satisfaction. Having just one inefficient step in the process disturbs every other step thereafter.
The first inclination many people have to try and resolve this issue is to adjust the nitrogen flow in one way or another. Increasing the nitrogen flow may seem like a logical solution, but this may cause other issues like solvent splashing or excessive turbulence. More nitrogen does not always equal more evaporation. The same negative effects may result when adjusting the proximity of the nitrogen stream to the solvent's surface - holding the nitrogen too close to the solvent is a common cause of sample loss.
An efficient method used to speed up solvent removal is the addition of heat. Depending on the solvents being used (excluding heat sensitive solvents), the addition of heat can significantly increase the rate of evaporation.
As nitrogen is being blown down on the sample, it decreases the energy and slows down the movement of the molecules within the sample. This slows down the ability of the molecules to vaporize and break away from the sample. The addition of heat re-energizes the sample and boosts the movement of the sample's molecules, therefore re-increasing their ability to be vaporized. The combination of the two methods creates an optimal environment for concentration.
Heat is a very common feature of sample concentration equipment, with the most common sources being a water bath, dry bead bath (typically with aluminum or glass beads), or a heat block. With a wide variety of evaporation technologies on the market, all with varying benefits, it's often difficult to know which is best for your application. Learn more about how the most popular evaporation techniques can speed up your sample concentration.