MATRIX-ENHANCED CALIBRATION PROCEDURE FOR MULTIVARIATE CALIBRATION MODELS WITH NEAR-INFRARED SPECTRA

A novel method is introduced for developing calibration models for the spectroscopic measurement of chemical concentrations in an aqueous en vironment. To demonstrate this matrix-enhanced calibration procedure, we developed calibration models to quantitate glucose and glutamine co ncentrations in an insect cell culture medium that is a complex mixtur e of more than 20 components, with three components that manifest sign ificant concentration changes. Accurate calibration models were genera ted for glucose and glutamine by using a calibration data set composed of 60 samples containing the analytes dissolved in an aqueous buffer along with as few as tao samples of the analytes dissolved in culture medium. Standard errors of prediction were 1.0 mM for glucose and 0.35 mM for glutamine. The matrix-enhanced method was also applied to cult ure medium samples collected during the course of a second bioreactor run. Addition of three culture medium samples to a buffer calibration I educed glucose prediction errors from 3.8 mM to 1.0 mM; addition of two culture medium samples reduced glutamine prediction errors from 1. 6 mM to 0.76 mM. Results from this study suggest that spectroscopic ca libration models can be developed front a relatively simple set of sam ples provided that some account for variations in the sample matrix.