Appearance potential methods, surface analysi

Height maps can be used for both qualitative and quantitative analyses. A surface plot of these can be used to determine the wetting mode of the droplet and the general appearance of the former liquid-gas interface. The larger the features of the former liquid-gas interface compared to the resolution of the method, the greater the potential for quantitative analysis. 

A thin film of oil-like material was visible after 28 d on the exterior surfaces of the SPMD membrane. Analysis of this film indicated that the triolein impurities, oleic acid and methyl oleate, were the major constituents. This external lipid film (Petty et al., 1993) appeared to contain imbibed particulates. Although the film was removed from the SPMDs by solvent rinsing and analyzed separately, some lipid-mediated desorption of particle-associated PCBs and subsequent diffusion into the SPMD may have occurred prior to solvent-removal of the film. This observation suggests the potential for SPMD concentrations to reflect both vapor phase concentrations and to a lesser extent, lipid-extracted particulate-associated residues (see Section 3.9.2.). Unfortunately, concentrations of more chlorinated congeners in particulates collected on GFFs from the NIOSH method were often below quantitation limits, because only a small volume of air was sampled (1 m ) using this active method. 

For the NP5 microporous active carbon there is anotlier peak located between 0.5 and 3 kJ mof, which represents tlie completion of the micropore filling process. A distinct minimum before this peak marks the value of the adsorption potential at the point at which the micropores are filled. The value of this minimum, a x(A), is given in Table 5 for the NP5 active carbon. This table gives also p/p o.x(Aj corresponding to A x(ap which marks on the adsorption isotlierm the value for the micropore volume VmxxA)- For instance, the APD method gave the micropore volume of 0.84 cm g for the NP5 carbon, which is close to that obtained by the tts-plot analysis (0.81 cm g ). This comparison shows that the APD-based analysis provides valuable information about surface and structure of active carbons. The minimum and inflection points that appear on the APD curves provide the values of the adsorption potentials, which correspond to the completion of the monolayer formation as well as the completion of the micropore filling. Thus, these values can be used to evaluate the total specific surface area and the micropore volume. 

---