Fig. 2. Model system for determining bi-functional reagent efficiency in detecting
amino acids on paper substrate. Visible images obtained from L-leucine (0.0075 M in
30% dioxane in water mixture) treated stamp stamped on a Whatman filter paper,
which was cut in half, where each half was treated with different bi-functional reagent
chain derivative (0.01% w/v in dimethyl sulfoxide) followed by water rinse then postenhancement
with Ag-PD. The bi-functional reagent indicating carbon chain length
used is shown under each half image. The bottom right image where the right half was
treated with Ag-PD only was used as the control.