Matrix effects in PIXE analysis on liquid samples with an external beam

Studies on the variations of relative sensitivity in the external beam PIXE analysis of liquid samples due to the presence of large amounts of neighboring elements were carried out. Liquid samples, containing V,Mn,Fe,Co and As in different combination and added with large amounts of Cu up to 100 mg/ml, were exposed to an external proton beam. The experimental results are in good agreement with theoretically calculated values. It is found that the variations of relative sensitivity for elements of Z>=20 are less than 1% if the Cu-concentration is less than 5 mg/ml and thus correction is not necessary when the internal standard method of analysis is amployed. However, if liquid samples contain Cu of high concentrations than 5 mg/ml the matrix effect should be taken into consideration even if the internal standard method of analysis is employed. (Auth.)