Evaluation of the use of polyvinyl alcohol in the manufacture of pressed samples for X-ray fluorescence analysis

Abstract

The reliability of the results of X-ray fluorescence analysis (XRF), which is widely used in determination of the elemental composition of various materials, largely depends on the quality of sample preparation. When producing pressed tablets for X-ray fluorescence analysis of trace elements, a binder is often used in a powder form, which requires significant time for thorough homogenization. We present the results of applicating a polyvinyl alcohol solution as a binder in the manufacture of pressed samples without using a substrate in determination of microelements by XRF. The parameters for obtaining a durable tablet with a homogeneous composition that matches the condition of minimum impact on the intensity of the analytical lines of the elements being determined are presented. It is shown that the optimal sample weight for the proposed method of producing pressed tablets is 7 g with the addition of polyvinyl alcohol in a ratio of 7:1, the optimal drying time for the tablet after pressing is 1 hour. The calculated variation coefficients of the analytical signal (<2%) indicate the homogeneity of the produced tablets. The maximum values of standard deviations of pressed tablets for the selected ranges of elements are much less than acceptable, which confirms the validity of the proposed method of sample preparation. It is also shown that during long-term storage and repeated measurements, pressed tablets with the polyvinyl alcohol solution retain their original structure and intensity of analytical lines of elements. The accuracy of measurements in the subsequent determination of rock-forming elements is consistent with their certified contents. The results obtained can be used to reduce the time spent on getting a representative pressed sample when using polyvinyl alcohol, determining elements without additional support (coating films), microelement and silicate analyzes from one sample.