DIN 38402-51:2015-09

This standard specifies several calibration strategies for physico-chemical and chemical analytical methods and the calculation of analytical results. The general framework for linear calibration is given so that reference can be made to it in the individual standards for analytical methods for water, wastewater and sludge analysis. Calibration is the prerequisite for the quantitative determination of analytes using physico-chemical and chemical methods. Since there is a linear relationship between information value and sample content in many measuring methods, simple linear regression is usually used. Since the publication of DIN 38402-51 in 1986, considerable progress has been made in instrumental analysis, which has led to a number of different calibration strategies being developed in order to make optimum use of the possibilities offered by the instrumentation. The theoretical statistical condition that simple linear regression may only be applied if there is variance homogeneity over the selected working range, limited the calibration range of many analytical methods to a maximum of one decade. Since estimation of the measurement uncertainty was done by calculating the confidence interval in DIN 38402-51:1986, the requirement for variance homogeneity had to be met. In the meantime, other methods independent of calibration have been established for estimating the measurement uncertainty (for example, DIN ISO 11352). The calibration strategies described in this standard allow the analyst to individually determine the calibration effort as a function of specified requirements. Since the procedure described in the previous edition (DIN 38402-51:1986) can still be useful for special purposes (for example, method validation), it is retained in the normative part of the Annex. This document has been prepared by Working Group NA 119-01-03-06-05 AK "Kalibrierung von Analysenverfahren" ("Calibration of analytical methods") of Working Committee NA 119-01-03 AA "Wasseruntersuchung" ("Water examination") of DIN Standards Committee Water Practice (NAW).