A comparison of orthogonal signal correction and net analyte preprocessing methods. Theoretical and experimental study

A comparison is presented between orthogonal signal correction (OSC) and net analyte signal (NAS) calculations. It was shown that the latter can be used as a preprocessing method comparable to the former, before the application of partial least-squares (PLS) to the filtered data. When the number of factors used in the net analyte preprocessing (NAP) procedure increases, the subsequent application of PLS requires progressively less factors, a behavior comparable to OSC. If enough factors are extracted by either NAP or OSC methods, the remaining calibration problem is amenable to a classical least-squares solution, giving rise to two multivariate calibration methods named NAP/CLS and OSC/CLS. All methods are illustrated from cross-validation and external validation results for two experimental examples: (1) the determination of the antibiotic tetracycline in human serum, and (2) the quantitation of the nasal decongestant naphazoline in multicomponent pharmaceutical solutions.