Difference Between Eluent and Eluate

Eluent vs Eluate
 

Chromatography is a widely used method for separating components from a mixture. This method uses a stationary phase and a mobile phase. Components of a mixture are carried through the stationary phase by the flow of mobile phase. In chromatography, separations are based on differences in migration rates among the mobile phase components. In a packed column, components are resolved by elution. The column consists of a narrow tube, which is packed with a solid that holds the stationary phase. The solid itself could be the stationary phase. Sometimes an inert solid, which holds the stationary phase, is used. Mobile phase can be introduced from top of the tube, and it will then occupy the spaces between the stationary phases. Initially, the solution mixture containing the components, which need to be resolved, is loaded into the column. For the loading, some of mobile phase can be used. According to the polarities, the components in the mixture will distribute between stationary phase and the mobile phase. Elution then occurs by forcing the sample components through the column by continuously adding fresh mobile phase. Time to time the components coming out of the column could be collected into test tubes. As the mobile phase, we can use solvent mixtures depending on the components we need to separate. By using a series of solvents according to a polarity gradient, we can separate all the components individually. Other than the above explained liquid chromatography method, we can also use gas chromatography to separate gaseous samples. In this instance, the mobile phase is a gas, which is known as the carrier gas.

Eluent

Eluent is the portion of the mobile phase, which carries the sample components with it. In liquid chromatography, eluent is the solvent used as the mobile phase. In gas chromatography, it is the carrier gas. Usually the eluent gas in gas chromatography is an inert/ un-reactive gas like helium or nitrogen. Eluent moves down the column containing the sample with it. Since eluent and the stationary phase have opposing polarities, eluent does not interact with the stationary phase. Therefore, its movement is independent. If the components in the sample have a similar polarity to the eluent, they have a high affinity to each other. This facilitates the movement of the sample.

Eluate

Eluate is what is coming out of the column. Usually this contains mobile phase and the analytes from the sample, which we wanted to separate. By changing the type of eluent that we are adding, we get eluate that contain different components of the sample. Then by removing the mobile phase (by evaporating), we can isolate the individual analytes which were in the sample.