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Pyrolysis studies of silica-immobilized benzyl phenyl ether (≈PhOCH2Ph or ≈BPE), a model for related ether structures in fuel resources, have been conducted at 275−325 °C to examine the impact of restricted mass transport on the pyrolysis mechanism compared with previous studies in fluid phases. Significant rearrangement chemistry is observed for ≈BPE occurring through two competitive free-radical pathways that are both promoted by the diffusional constraints. One path involves recombination of incipient benzyl and surface-bound phenoxy radicals to form benzylphenol isomers, 10. The second, previously unreported rearrangement path for ≈BPE involves a 1,2-phenyl shift in an intermediate radical, ≈PhOCH·Ph, leading to formation of benzhydrol (8) and benzophenone (9) as principal products. The rearrangement products 8−10 typically account for ca. 50% of the pyrolysis products. However, the path selectivity is a sensitive function of ≈BPE surface coverage and the presence of spacer molecules that either facilitate or hinder hydrogen atom transfer steps on the surface.

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A thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) method was validated for the determination of volatile organic compounds collected on carbonaceous triple sorbent traps and applied to characterize samples of headspace gases collected from underground nuclear waste storage tanks at the U.S. Department of Energy's Hanford site, in Richland, WA. Method validation used vapor-phase standards generated from 25 target analytes, including alkanes, alkyl alcohols, alkyl ketones, alkylated aromatics, and alkyl nitriles. The target analytes represent a group of compounds identified in one of the most problematic tanks. TD/GC/MS was carried out with Hewlett-Packard 5972A or 5995 GC/MS systems with modified injectors. Performance was characterized based on desorption efficiency, reproducibility, stability, and linearity of the calibration, method detection limits, preanalytical holding time, and quality control limits for surrogate standard recoveries. Desorption efficiencies were all greater than 82%, and the majority of the analytes (23 out of 25) had reproducibility values less than 24% near the method detection levels. The method was applied to the analysis of a total of 305 samples collected from the headspaces of 48 underground waste storage tanks. Quality control procedures were implemented to monitor sampling and TD/GC/MS method. mean recovery ( 2 × σ n Pr [ S 2 e σ 2 2 (0.95, n -1) n -1 ] ) 0.95

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