A forensic scientist investigated an unknown toxic plant extract, U\text{U}U, and four reference alkaloid standards, atropine (A\text{A}A), caffeine (C\text{C}C), nicotine (N\text{N}N), and strychnine (S\text{S}S), using thin-layer chromatography (TLC).
The resulting chromatogram is shown below:
a.[1]
Identify which of the four reference alkaloids is present in the unknown extract U\text{U}U.
b.[2]
Calculate the RfR_{\text{f}}Rf value of this reference alkaloid, using the equation:
Rf=distance moved by substancedistance moved by solvent frontR_{\text{f}} = \frac{\text{distance moved by substance}}{\text{distance moved by solvent front}}Rf=distance moved by solvent frontdistance moved by substance