New optimization strategy based on mixed Quantitative Structure-Retention
Relationship (QSRR) model was proposed for improving the RP-HPLC separation
of aripiprazole and its impurities (IMP A-E). Firstly, experimental
parameters (EPs) (mobile phase composition and flow rate) were varied
according to Box-Behnken Design and afterwards, artificial neural network
(ANN) as QSRR model was built correlating EPs and selected molecular
descriptors (ovality, torsion energy and non-1,4-Van der Waals energy) with
analytes log-transformed retention time. Values of root mean square error
(RMSE) were used for ANNs quality estimation (0.0227, 0.0191 and 0.0230 for
training, verification and test set, respectively). Separations of critical
peak pairs on chromatogram (IMP A-B and IMP D-C) were optimized using ANNs
for which EPs served as inputs and log-transformed separation criteria s as
outputs. They were validated applying leave-one-out cross-validation (RMSE
values 0.065 and 0.056, respectively). Obtained ANNs were used for plotting
response surfaces upon which analyses chromatographic conditions resulting
in optimal analytes retention behaviour and optimal values of separation
criteria s were defined and they comprised of 54 % of methanol at the
beginning and 79 % of methanol at the end of gradient elution programme with
mobile phase flow rate of 460 ?L min-1.