Quantitative analysis of elements (C, N, O, Al, Si and Fe) in polyamide with wavelength dispersive X-ray fluorescence spectrometry

Abstract

A wavelength dispersive X-ray fluorescence (WD-XRF) spectrometry combined with calibration curve method was established for simultaneously analyzing low-Z elements (C, N, O) and Al, Si, Fe in polyamide. To investigate the origin of plastic material causing deposition and blocking in instrument engines and pipelines, polyamide 6 (PA 6, an engineering plastic) was chosen as the study object on account of its common use in industry. The sample preparation with pressed powder disk has been developed for determination of six elements in PA 6. Pure Cu metal was used as the matrix and PA 6 was regarded as standard sample for C, N, O elements. PA 6 particles were firstly smashed to uniform powder in liquid nitrogen, and then mixed with inorganic standard powders (Fe2O3, Al2O3, SiO2, and Na2SiO3). The mixture was ground to obtain homogeneous calibration materials for WD-XRF analysis. The quantitative property of the calibration curve method for each element was reliable. The limits of detection (S/N≤3) of C, N, O, Al, Si and Fe using WD-XRF were 249, 120, 101, 6.2, 3.3, and 1.8 μg/g, respectively. To confirm the accuracy of the proposed WD-XRF calibration curve method, inductively coupled plasma optical emission spectroscopy (ICP-OES) detection for Al, Si, Fe and elemental analyzer (EA) analysis for C, N, O were utilized. A good correlation of the WD-XRF results with the measurements of ICP-OES and EA was observed.