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 2

HPTLC of reference samples M1, M2, and M3 (50-month-old) developed in system A—butanol/isopropanol/ethanol/water (5 : 3:2 : 1 v/v).