Advances in second-order calibration

Several multivariate methods are now available for the calibration of second‐order or hyphenated instruments (e.g. GC/MS). When applied to bilinear data, it has been shown that calibration can be performed in the presence of unknown interferences ‐ a significant advantage over first‐order calibration. In this paper, non‐bilinear rank annihilation (NBRA), a method which has the potential of handling, second‐order non‐bi‐linear data, is studied through theoretical analysis and computer simulation. It is found that the second‐order advantage can be carried over to non‐bilinear data if a property defined as net analyte rank (NAR) holds for the analyte of interest. The net analyte signal (NAS) is defined accordingly for second‐order calibration and the analogy to and difference from lower‐order calibration are discussed. With NAS, some analytical figures of merit such as signal‐to noise ratio, selectivity, sensitivity and limit of determination can be calculated for second order calibration. An application to MS/MS data is also given.