For many years the photometric analysis techniques were dominating in most of ecological, sanitary, technological, and biochemical laboratories. However, as the requirements for the ultimate tolerable concentrations (UTC) have become more stringent, the luminescence techniques are being widely used for assaying many of the substances, especially for low detection concentration, and are preferable to the absorption photometric techniques due to the following advantages:
the high selectivity of the luminescence technique allows the number of the sample preparation stages to be reduced and the reliability of the assay to be enhanced (Zn, Cu, Al);
the high sensitivity of the technique allows operation with small-volume samples, thereby speeding up sample processing during each stage of the sample preparation, and reducing the consumption of reagents (surfactants, formaldehyde, Cd, Sn, Cr, Al, Cu);
it is possible to detect the components which are undetectable by the photometric technique because of their low UTC (phenols, As, B, Be, Se, U, B-vitamins) or need the use of a special-purpose IR-absorption photometer (petroleum hydrocarbons).