Improvement of residual bilinearization by particle swarm optimization for achieving the second-order advantage with unfolded partial least-squares

The combination of unfolded partial least-squares (U-PLS) with residual bilinearization (RBL) provides a second-order multivariate calibration method capable of achieving the second-order advantage. RBL is performed by varying the test sample scores in order to minimize the residues of a combined U-PLS model for the calibrated components and a principal component model for the potential interferents. The sample scores are then employed to predict the analyte concentration, with regression coefficients taken from the calibration step. When the contribution of multiple potential interferents is severe, particle swarm optimization (PSO) helps in preventing RBL to be trapped by false minima, restoring its predictive ability and making it comparable to the standard parallel factor (PARAFAC) analysis. Both simulated and experimental systems are analyzed in order to show the potentiality of the new technique. Copyright (C) 2007 John Wiley & Sons, Ltd.