This article describes methods to quantify urea-formaldehyde (UF) resin and phenol-formaldehyde (PF) resin contents in medium density fiberboard (MDF) using a wavelength dispersive X-ray fluorescence spectrometer (WDXRF). The methods are based on the principle that a specific metallic element shows its characteristic X-ray fluorescence spectrum, the intensity of which is correlated quantitatively to its concentration. In the case of UF-blended MDF fiber, 2.4% copper sulfate pentahydrate CuSO4.5H2O (based on resin solids) was premixed with the resin as a labeling agent. Quantification of copper ion was performed using XRF. Based on calibrations with laboratory-prepared standard fiber samples of known UF resin and copper quantities, the results of XRF measurements were converted to resin loading rates. In the case of PF-blended fiber, the PF resin contents in the MDF fiber samples were successfully quantified by measuring the existing sodium ion Na+ in the resol resin with XRF. Linear calibration curves between fluorescence intensity of copper or sodium and resin content were established respectively for UF and PF resins. Test results show that the methods were precise and reliable
