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.