Different analytical methodologies for the preconcentration and determination of trace chromium by XRF in medicinal herbs with effects on metabolism

Abstract

The essentiality of chromium and the disturbances that its deficiency produces in humans are of interest, have the detection and determination of chromium in drugs of vegetable origin used in phytotherapy are of great importance. With the purpose of improving the sensitivity by increasing the peak-to-background ratios in trace element determinations by x-ray fluorescence (XRF) analysis in biological samples, the high concentration of lower atomic number elements (C, H, O, N) must be removed. These elements can produce non-specific enhancement and absorption effects on the characteristic radiation of the elements of interest. The analytical methodologies for eliminating interferences were realized in different ways in solid and liquid samples. In the first case, the assay was done on dried and calcined herbs and the variables related to the method such as drying time, grinding time, calcination time, calcination temperaure, quantity of ash for pellet preparation, pressure for pellet preparation, etc, were studied. In the second case, two methods were evaluated: (a) lixiviation with different acids or acids mixtures and (b) infusion or brewing of medicinal herbs. In both cases, it was necessary to develop a preconcentration method for the determination of Cr by XRF. The optimum parameters for preconcentration and thin-film preparation were also studied. The methodologies were applied with very good results to the determination of trace Cr in the medicinal herb Taraxacum officinale and in synthetic samples.