Why might some amino acids not be visible on a chromatogram?

The correct answer relates to the phenomenon of overlapping components on the chromatogram. When amino acids are subjected to chromatographic separation, they are expected to travel along the stationary phase with the mobile phase. However, if multiple amino acids have similar affinities for the stationary phase, they can travel together and appear as a single spot on the chromatogram. This overlap can make it challenging to distinguish between the amino acids, leading to some being undetected or misidentified, obscuring their presence in the analysis.

In a practical context, overlapping can occur due to factors such as similar chemical structures or competitive interactions within the stationary phase. As a result, while the amino acids may be present, their indistinguishable nature on the chromatogram prevents visibility, leading to confusion in quantification and identification.

Other possible reasons for amino acids not being visible, such as being too dilute or degrading during the process, are more focused on concentration levels or stability rather than the inherent properties that lead to their visibility or invisibility on the chromatogram. Similarly, while some may not have traveled with the solvent front, this explanation does not encompass the interactive complexities of the stationary phase that can result in overlapping signals from different amino acids.