Appeal 2007-0711
Reexamination 90/006,706
values and high α (chromatographic separation factor) values. For ibuprofen
especially, k’1 values reported using both Mobile Phases A and B were less
than 1, i.e., k’1 = 0.27 for Mobile Phase A (~5% 2-propanol/~95%
hexane/~0.1% acetic acid) and k’1 = 0.75 for Mobile Phase B (~20% 2-
propanol/~0.1% acetic acid/~0.1% triethylamine/~80% hexane)(Pirkle, col.
22, ll. 43-68).
Pirkle’s Table 16 (Pirkle, col. 29, Table 16), and the paragraph
immediately following Table 16 (Pirkle, col. 29, ll. 40-48), are significant
for a variety of reasons. First, Pirkle teaches that the higher the α
(chromatographic separation factor) value reported in Table 16 using a
common mobile phase (~20% 2-propanol/~80% hexane/~1 g/L ammonium
acetate) but different stationary phases (CSP-10 and CSP-2) in the
separation process, the “higher degree of chromatographic separation (α) of
the underivatized analytes” (Pirkle, col. 29, ll. 40-42, and Table 16).
Second, Pirkle teaches that, as the analyte capacity factors (k’s) decreased,
the α (chromatographic separation factor) values reported in Table 16
increased. “Analyte capacity factors (k’s), as apparent in Table 16, were
consistently less . . .” (Pirkle, col. 29, ll. 44-48, and Table 16). Therefore,
the data in Pirkle’s Table 16 suggests that the lower the analyte capacity
factor (k’) value, the “higher degree of chromatographic separation (α) of the
underivatized analytes” (Pirkle, col. 29, ll. 41-42; generally col. 29, ll. 6-48,
including the data in Table 16). Accordingly, we find in Pirkle that, at least
for separation of the chiral isomers of enantiomeric mixtures using an achiral
mobile phase solvent composition containing a chiral selector, the highest
degree of chromatographic separation of the chiral isomers is most likely to
be effected using mobile phase solvent compositions having the lowest
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