| Abstract: | For spectrochemical analyses, calibration is a basic operation generally necessary for quantitative determinations. It yields the calibration function and by inversion the analytical function which is not directly accessible.—In the following, a scheme is developed in order to find-according to different methods of analysis-the respective suitable calibration function: it should give an expectable standard deviation as small as possible for the estimated content, it should, if possible, be linear and it should be applicable in a range of content as large as possible. The condition of Part I of this paper is the constant standard deviation for the measuring quantity in this range.-The scheme is examined by five analytical examples: for trace analyses (OES-ICP and AAS) the simple relationship between the intensity I and the concentration c is linear anyhow and yields a constant absolute standard deviation not dependent on the trace content. For analyses over a large range of concentration, a double-logarithmic transformation leads to linearity and constant relative standard deviation (OES with Laser). If physical matrix effects are existing, for example in surface analysis (ISS) the ‘binary-ratio method’ is recommended; in this case, the relative standard deviation is proportional to (1 - c). For XRF of main and additional components, the non-linear regression of the equation of Beattie and Brissey is to be realized with √I-values. |
