Combination of a Green and a Traditional Method for Estimating Relative and Absolute Ink Age: A Case Study of Ballpoint Pen Ink Dating in Vietnam

Figure 4

HPTLC of questioned samples A1.1, A2.1, and A3.1 developed in system A—butanol/isopropanol/ethanol/water (5 : 3:2 : 1 v/v).