A method and system for increasing optical instrument calibration and prediction accuracy within and across different optical instrument platforms can include two main submethods or routines. The first routine can include one for correcting differences among optical instruments of different model types regardless of the manufacturer and correcting differences among optical instruments of the same model type. The second main routine or sub-method can include one for analyzing new samples of a product over time and maintaining prediction accuracy as compared to a reference method over time. The first routine can include a “TRANS” procedure, a “MIN” procedure, and checkcell tests. The second main routine provides techniques on how a product database can be cleaned, condensed, and expanded automatically as it is used by one or more different optical instruments.