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 3

HPTLC of reference samples A1.2, A2.2, and A3.2 (39-month-old) developed in system A—butanol/isopropanol/ethanol/water (5 : 3:2 : 1 v/v).