Calibration transfer of partial least squares jet fuel property models using a segmented virtual standards slope-bias correction method

Abstract

Fifteen pure molecular chemicals were used to transfer near-IR partial least squares (PLS) models of jet fuel properties between two dispersive near-IR instruments by a novel calibration transfer, standardization, method. PLS was applied to establish models for quantitative analysis of jet fuels properties. The modeled jet fuel properties include: API gravity; %aromatics; cetane index; density; distillation temperatures for 10%, 20%, 50% and 90% recovered volume; flashpoint; freeze point, %hydrogen content; %saturates; and viscosity. The transfer of the PLS models requires that spectra of only 15 pure chemicals be acquired on the primary and secondary instruments. The spectra of the chemicals are then segmented into distinct spectral regions which are subsequently used to digitally construct spectra of virtual standards which mimic jet fuel spectra in the training set. The resulting virtual standards for the primary and secondary instruments are then predicted using the PLS models, and the prediction values are regressed to provide a simple but effective slope and bias correction for transfer. SVSSB calibration transfer of 7 jet fuels properties shows better performance than PDS, for example, in the case of cetane index Root Mean Square Error of Prediction (RMSEP c) of SVSSB and PDS corrected secondary instrument relative to primary instrument prediction are 0.19 and 0.27 respectively. SVSSB and PDS show comparable performance of the other 6 jet fuel properties. For example, RMSEP c of SVSSB and PDS corrected secondary of % hydrogen content of secondary instrument relative to the primary instrument prediction are 0.015 and 0.014 respectively. The Segmented Virtual Standards Slope and Bias Method (SVSSB) performs as well as using real jet fuel standards to generate a slope and bias correction, and also as well as conventional Piecewise Direct Standardization (PDS), while eliminating the need to maintain either the complex fuel standards or the primary instrument.