Test for non-linearity concerning linear calibrated chemical measurements

Linear calibrated chemical measurements are based on the assumption of linearity. Due to influences of matrices at real samples the condition of linearity can be violated. Therefore, a profound examination has to attach much importance on the linearity of calibration. However, different procedures have been applied for this purpose in literature. In order to examine linear calibration for non-linearity, a recently presented procedure is compared with conventional techniques. The associated statistical models and estimations are represented. The applicability of the different procedures is demonstrated in some practical examples, the determination of arsenic in surface water samples taken from different sites in abandoned mining areas in central Germany. Recommendations for using the indicators and tests of non-linearity are given.