The chloroamide compound 1,3,4,6-tetrachloro-7,8-diphenyl-2,5-diiminoglycoluril (S-330) was found to be a strong reactant in dermal formulations for the decontamination of sulfur mustard (HD). In this report, we present analytical methodologies applicable to the characterization, purity determination and quantitation of S-330 in bulk material or formulations. High-performance liquid chromatography-mass spectrometry (LC-MS) coupled with atmospheric pressure chemical ionization (APCI) interface or ultraviolet detector and nuclear magnetic spectroscopy (NMR) were used to identify and characterize S-330 and impurities in the synthetic lots or degradation products in formulations. Bulk synthesis using a chlorination process has yielded a product of 90% purity. The major impurity has been separated and identified structurally as the trichloro analog of S-330. Higher purity S-330 can be made using column chromatography, but this does not appear to be economical for large-scale production. Factors affecting the stability of S-330 in topical formulations include water content, pH, alcohols and UV light. Chloroamide S-330 decomposes at 50-60ΨC and is not amenable for GC analysis. The HPLC technique is superior to NMR or active chlorine assay in the purity determination for S-330 in bulk material or formulations. In topical formulations containing S-330, 5-10% of water can be tolerated, but alcohols and acidic and basic conditions should be avoided.