Response to “comments on interrelationships between sensitivity and selectivity measures for spectroscopic analysis” by K. Faber et al.

A recent Tutorial [J.H. Kalivas, P.M. Lang, Chemom. Intell. Lab. Syst. 32 (1996) 135–149] discussed interrelationships between several sensitivity and selectivity measures set out in the literature with respect to the Beer-Lambert law. Recommendations by Kalivas and Lang were given for what they believed best captured local, i.e., analyte specific, sensitivity and selectivity information. In particular, the multivariate sensitivity measure proposed by Bergmann et al. [G. Bergmann, B. von Oepen, P. Zinn, Anal. Chem. 59 (1987) 2522–2526] was discerned as most suitable. Faber et al. [K. Faber, A. Lorber, B.R. Kowalski, Chemom. Intell. Lab. Syst., preceding article] give a different opinion on what they believe to be a better suited definition of sensitivity, namely, Lorberʹs definition [A. Lorber, A. Harel, Z. Goldbart, I.B. Brenner, Anal. Chem. 59 (1987) 1260–1266]. Unfortunately, Faber et al. do not accurately express our line of reasoning in support of the sensitivity definition proposed by Bergmann et al. Additionally, Faber et al. discuss specific calibration requirements for computation of Lorberʹs sensitivity measure and state that conditions presented in the article of Kalivas and Lang are incorrect. This paper considers ideologies for sensitivity measures for the Beer-Lambert law, addresses comments by Faber et al. regarding our reasoning for adoption of sensitivity as proposed by Bergmann et al., and further discusses computational conditions for Lorberʹs sensitivity. Some brief comments are given regarding Nth-order sensitivity.