Abstract

Systematic errors can occur in every chemical analysis independent of the method used. In general, the risk of systematic errors can be diminished by separation steps prior to the determination procedure. In sensor measurements systematic errors can be noticed only by anlysing real samples with a known concentration of the analyte with a great variety of matrices. The sources for such errors are manifold, although excellent reproducibility of the results is shown. The main reason for a systematically blased result in the field of chemo- and biosensors lies in the influence of the sample matrix on the sensor signal, which ought to be produced by the analyte only. Examples of strong matrix interferences on different sensor principles are presented and a classification of the most prominent systematic errors known in analytical chemistry is given. Apart from problems related to a lack of selectivity, which lead to a co-sensing of interferents, the matrix often influences the sensitivity (slope of the calibration curve) and/or the level of the blank signal in an unpredictable manner. Compensation methods, like the well-known blank-signal subtraction or differential sensor measurements, work properly only if certain conditions are fulfilled. The principle of signal additivity has to be proven and the invariance of the sensitivty has to be demonstrated in any case and for different matrice