Robust regression methods to calibrate a continuous flow analyzer in the colorimetric analysis of inorganic...

The presence of a salinity effect in the automated analysis of phosphorus in seawater performed by a phosphomolybdate complex can cause the inaccurate estimation of the true amount, because the calibration procedure performed by least-squares regression does not take into account the different analytical response of samples and standard solutions. The error arising from this salt effect is corrected by calibrating the autoanalyzer with robust regression methods (RRMs), which allow definition of the range of salinity in which the analytical response of the autoanalyzer is only dependent on the concentration of marine nutrients. The RRMs are especially helpful in the analysis of oligotrophic samples where the salinity effect is particularly relevant.