However tempting it might be to obtain PEG assignment based on these mass matches, one must be aware of the limitations of this procedure. First, there may be two or more different chemical structures that would generate a nominal mass match for a single PEG distribution. For example, polyoxyethylene lauryl ether would be indistinguishable from structure VII in Figure , glycolic acid ethoxylate lauryl ether, another popular polymer additive (although these two polymers can be distinguished using high resolution mass measurements). The second (and perhaps more significant) problem is that the actual number of PEGs used as dispersants is significantly larger than those represented in Figure , and continues to grow; in addition to the linear structures, there are also branched polymers used as surfactants and dispersants in ink formulations (see, for example, U.S. patent 7,160,376 B2), and their distinction from linear polymer chains on the basis of a mass measurement alone is impossible.