Univariate Linear Methods

The most used method for determining the concentration of an analyte is based on a univariate model where the measured signal intensity is linearly proportional to said concentration. The signal measured on the samples is compared with the one obtained from suitable standards of known composition to build a calibration curve. Laser-induced breakdown spectroscopy (LIBS) is not different in that, and most of the papers published in the literature use this relatively simple approach. The use of univariate calibration curves is still the most diffused method for the quantification of analytes in LIBS and, in most of the cases, it works perfectly. This simplest approach to quantitative analysis by LIBS and its application should always be evaluated before trying other, more advanced methods. The comprehension of the basic univariate approach to LIBS calibration is essential for understanding the peculiarity of LIBS, with respect to other spectroanalytical techniques, and eventually applying multivariate and/or nonlinear methods with a full comprehension of both the advantages and limitations of such approaches.