On the GF-AAS determination of chromium in water samples

Determination of chromium in samples of water may be performed by GF-AAS that is capable of analyzing for very low concentrations in the range of micrograms per liter. Chromium belongs to the group of metals that are known to be toxic in high concentrations to humans, although it is also regarded as a nutrient, as an essential trace metal for humans. However, there is a risk of generating incorrect concentrations, if the general level of uncertainty of measurement were not established beforehand during the process of method validation. Determination of chromium in pure water is regarded as relatively uncomplicated but it is more difficult in saline solutions, owing to the influence of interferences. In the current investigations, interferences are disregarded with the aim of establishing all parameters that are required for the analytical laboratory to get a full overview of uncer-tainty of measurement and performance of the method itself. Guidelines of quality assurance recommend that the uncertainty of measurement should be calculated upon the basis of a single calibration line. However, recent investigations have indicated that uncertainties that were derived from pooled calibrations are more likely to be comparable to those found by repetitions of samples, which is beneficial to reliability and decision making.