John,

I find that a lot of false positive identifications are made when the residue is present at very low levels. You mention the low abundance of the alkanes in Exhibit 4, for example. E1618 does not have much guidance as to how to judge what constitutes a "significant" amount of residue, which I think leads to a lot of these incorrect conclusions. Apart from oxygenated products, there is little in the standard that quantifies how much one should actually be looking for. Were there ever any discussions in the committee about making explicit reporting thresholds or similar?