Calibration in Flow Analysis

The proper implementation of calibration is to a large extent determined by careful and correct preparation of calibration solutions and samples for measurements. This is especially important in trace analysis because even the smallest errors, random or systematic, at the laboratory stage of the calibration procedure can significantly influence the precision and accuracy of the obtained results. 

The techniques used in flow analysis can help overcome these problems. The natural peculiarities of flow techniques are conducive to proper and efficient preparation of calibration solutions and, therefore, in obtaining reliable analytical results in trace analysis. These techniques have been successfully examined and are widely employed for a range of analytical purposes. They are also widely used to perform calibration by a variety of procedures, implementation of which in the traditional way is not possible. 

In this way, it is possible to collect measurement data enabling calibration using the set of standards method. In order to implement other calibration methods, the tube installed directly behind the valve can be used to deliver standard solutions to the injected segment of sample (standard addition method), or to merge with the injected solutions of sample and standards the internal standard solution (the internal standard method) or an appropriate reagent (indirect method). In these cases, the flow technique contributes to more efficient and economic preparation of complex calibration solutions than the traditional mode. 

Selected Calibration Procedures in Flow Analysis In recent decades there have been great developments in various fields of flow analysis, including a number of interesting and specific proposals for the flow mode of analysis calibration. These allow implementation of the various methods of calibration in accordance with procedures that are often completely different from those that analysts use in their everyday work [4, 5]. The advantage of these approaches compared with the procedures existing in traditional analysis relies not only on more efficient, automated implementation of full calibration (and thus also the complete analytical procedure), but also on the opportunities for more efficient use of the registered analytical signals to obtain richer measurement information. 

One of the tasks that can be accomplished relatively easily in flow analysis is the creation of conditions that allow a series of measurement results to be obtained using only a single standard solution (and not several standard solutions). A classic example is the network calibration method, performed using a flow system made up of a network of tubes of different lengths connected to each other prior to the detector (Fig. 3.10a) [6]. In this system, the injected segment of standard solution is 

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