A comparison between X‐ray fluorescence and dissolution methods employing lithium metaborate fusion for elemental analysis of soil clays

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Abstract
A method employing fusion of soil clay samples with lithium metaborate (1:5 ratio) in a furnace at 1050°C for 1 hr. subsequent dissolution of the fused sample in 4% HNO3. and elemental analysis for Si, Al, Fe, Ca, Mg, K, and Ti by atomic absorption spectrometry was compared with the X‐ray fluorescence (XRF) fused disc technique for analysis. Duplicated analyses were performed on 15 clay samples from soils of the southern U.S and three API reference samples. The mean total percent recovery by this method was excellent (100.14 ± 2.85). Elemental oxide quantities in terms of SiO2. Al2O3, Fe2O3, MgO, CaO and K2O determined by atomic absorption/flame emission (AA/FE) spectroscopy were in good agreement with values measured by x‐ray fluorescence (XRF) on the same subsamples (r = 0.89* to 0.98**). but somewhat more variable on subsamples seperated from different pretreatments (r = 0.70* to 0.97** ). The method, which has also been tested on 36 additional clay samples from a variety of Kentucky soils with total percent recoveries ranging from 96.5 ‐ 103.5%. demonstrated no bias due to mineralogy with respect to mixed, montmorillonitic. and siliceous classes. This technique presents numerous advantages over other elemental analysis techniques utilizing fusion, dissolution, or XRF spectroscopy with respect to time, effort and cost. With the introduction of inductively‐coupled plasma (ICP) emission spectroscopy. efficiency can be additionally improved.