A new internal standard method coupled with the standard addition method for proton-induced X-ray emission analysis and its application determination of Cu, Zn, Rb and Sr in biological materials

Abstract

A new internal standard method coupled with the standard addition method for PIXE analysis has been developed. In its basic principle, this method is characterized by that a suitable element present initially in the sample is used as an internal standard, and further the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample contains W_a g of trace element A to be determined together with an element B which is usable as an internal standard, and when the comparative standard is prepared by adding an exactly known amount of element A, W ^*_a g, to the duplicated sample, the absolute concentration of W_a can easily be determined by the following equation even if the above sample and comparative standard are irradiated separately by a different number of protons W_a=W ^*_a /[(R^*/R)-1] where R and R^* are ratios of net photopeak counts due to the characteristic X-rays from the element A and B in the irradiated sample and comparative standard, respectively. The usefulness of the method was examined through determination of Cu, Zn, Rb and Sr in two biological materials, such as spinach and orchard leaves. As a result, this method was demonstrated to be sensitive, highly reproducible and reasonably accurate.