from a group of samples tested, is it true that the highest rf is the first the be eluted? If so, why is that?
The concept of "retention factor" (RF) is commonly used in chromatography to describe the movement of different compounds during the separation process. In general, the higher the RF value, the less strongly a compound is retained by the stationary phase and the faster it elutes (moves) through the system.
To answer your question, it is not necessarily true that the highest RF compound will always be the first to be eluted. The elution order depends on various factors, including the properties of the compounds, the type of stationary phase, and the mobile phase used in the chromatographic technique.
However, in certain cases, it is possible for compounds with higher RF values to elute earlier. This can happen if the stationary phase interacts less strongly with the compounds having higher RF values, allowing them to pass through the system more quickly. Conversely, compounds with lower RF values tend to interact more strongly with the stationary phase and take longer to elute.
It's important to note that the elution order is not solely determined by the RF values. Other factors, such as the composition of the mobile phase, the column dimensions, and the temperature, can also influence the separation and elution order of compounds in chromatography.
To determine the elution order of compounds in a particular system, experimental testing is usually required. By analyzing a group of samples using the chosen chromatographic technique and comparing the elution times or retention times of the compounds, you can establish the relative order in which they are eluted.