A new approach to a complete robustness test of experimental nominal conditions of chemical testing procedures for internal analytical quality assessment

The resistance presented by a particular analytical method or procedure to the generation of biased results when subjected to slight modifications in nominal experimental conditions has traditionally been known as ruggedness (from an interlaboratory trial) or robustness (from an intralaboratory study). This paper develops a protocol for a complete study of robustness, using a simple statistical technique which does not require the performance of ANOVA. The method simply consists of the establishing of a standard calibration and the creation of experimental screening designs (saturated fractioned or Plackett–Burman factorials [R.L. Plackett, J.P. Burman, Biometrika 33 (1946) 305–325]). The various stages of the test are discussed and the proposed model is applied to the real data referring to a spectrofluorimetric method of determination of lithium.