Photometric analysis methods used to define the elements widely on the contents of 100 to 10 ^ -6%. In selecting and description of methods and techniques for determining the content of these interval most common interest metrological (correctness, convergence, reproducibility, sensitivity, detection limit, the lower limit of determining the content) and analytical (selectivity, Express) specifications, the availability of equipment and the possibility of automating the method of analysis.

photometric method for determining use different criteria: working interval defined concentrations, the nature of sample matrix, sensitivity, reproducibility, selectivity, practically defined limit the definition.

Kolorimetrichesky method of analysis much faster method of weighted mainly because there is no need office product reaction (filtering, washing, etc.).

Kolorimetrichesky analysis compared with the weighted much more sensitive and therefore more suitable for identifying small amounts of impurities. The number of substances 0.1 mg order can not be weighed on conventional analytical weights, but often can be easily identified by its colour in the solution.

Kolorimetrichesky method yields weighted on the accuracy of definition. However, the requirements for accuracy in the determination of small quantities of substances usually reduced even more so that the weight and volume methods of analysis in this case, too, are becoming less accurate. In addition, insufficient in some cases the accuracy of the colorimetric analysis was not with his principled basis, but not enough to develop techniques.

In a multicomponent spektroscop analysis, as in colorimetric, optical density measurements should be conducted on the comparison solution containing all reagents used to reduce systematic errors arising from impurities in themselves reagentah.

Photometric determination of both components present in the mixture, easily performed by any of the above analysis methods.

In spectroscopy, in fact, excluded error, which makes a substantial contribution to the overall error of the optical density measurements with colorimetric. In addition to this and other design features spectrophotometers allow, in some cases, improve accuracy and repeatability of measurements compared to normal spectroscopy.

In a derivative spectrophotometry is changing shape, with its spectral curve Differentiation. The use of differentiated spectrum (especially the second derivative) provides:

- To make significant strengthening of differentiated contrast curves than normal even with small changes monotony spectrum, resulting in easier analysis;
Multi-analysis systems;
- Significantly improve selectivity definitions ions in complex mixtures and dispersed systems;
- Crush background signal and thus exclude or reduce systematic errors caused by background neuchityvaemym.

So considered methods are very similar. But fotokolorimetric methods of analysis used to identify the elements of widely on the contents of 100 to 10 ^ -6%. It is more sensitive and to identify small amounts of impurities, but needs to be expanded over accuracy. This method is economically beneficial and is widely used in manufacturing.

Using absorption spectroscopy of the Infrared (from 8 to 30-35 microns) makes it possible to significantly improve selectivity and sensitivity analysis. Accuracy method is less than 1%. But devices based on this method, much more costly colorimeter.