TABLE OF CONTENTS Construction of a calibration line using seven or more calibration points every time a sample (or batch of samples) is analysed can be a time-consuming and expensive process. Some alternative, shorter calibration procedures [11] are therefore discussed below. However, such procedures should only be applied after it has been established by use of the full calibration procedure described in Sections 4.7 and 4.8 that the calibration graph is linear over the range of interest.
Where previous experience shows that a linear calibration line which passes through the origin may be expected (calibration model 1, Section 4.6.1), a single calibration standard only may be used. The documented property value ( e.g. concentration) of the calibration standard is chosen to equal or somewhat exceed the maximum value likely to be encountered in the samples being analysed, whilst also being within the already-established linear range of the instrument. Provided the reagents used to prepare the sample for instrumental measurement do not give a significant instrument signal ( i.e. provided the sample blank is zero), then the analyte quantity in the sample may be calculated using the equation:
If the sample blank value is significant it must first be subtracted from the measured instrument signal values for the sample and calibrant before Eq. 4.21 is used.
Where it is known that the calibration plot is linear, but does not pass through the origin of the calibration graph...
