Liquid adsorption on a substrate has great applications in ink jet printing as well as micro/nano fabrication. In this letter, we focus on obtaining a better understanding of the pinning-dewetting phenomenon through solubility measurements during droplet evaporation. The physical adsorption/penetration of liquid on the substrate material is considered to he responsible for the pinning of the three-phase contact line. Once the adsorption surrounding the contact line reaches equilibrium, dewetting occurs and the droplet shrinks. The absorption kinetics of water molecules on different substrates was monitored. An analytical technique was developed to measure the threshold adsorption density of trace solvents on these substrates including different polymers, silicon, and gold.