Determination of Boron and Silicon in Boron Ore by ICP-OES after Closed Digestion and Aluminum Trichloride Complexation

Boron ore is an important non-metallic strategic mineral resource. Besides boron, silicon (a major rock-forming element) also needs to be determined. For the determination of boron and silicon in boron ore by inductively coupled plasma-optical emission spectroscopy (ICP-OES), conventional sample pretreatment requires separate tests: boron is analyzed by closed acid digestion with a hydrofluoric acid-resistant injection system, while silicon is decomposed by alkali fusion. This study established a novel ICP-OES method for the simultaneous determination of boron and silicon in boron ore. Samples were digested in a closed HNO₃-HF-NH₄Cl mixed acid system, for matrix matching, 1.2 mL of 0.1 g/mL aluminum trichloride solution was added to the calibration standard series. The injection system was rinsed with dilute ammonia solution before ICP-OES analysis. The boron detection limit was 14.5 µg/g with a linear range of 0.0021%–20%, and the silicon detection limit was 5.94 µg/g with a linear range of 0.0008%–20%. The proposed method was verified using three certified reference materials including boromagnesium ore, boroiron ore and borosilicate, the results were in good agreement with the certified values. Five practical boron ore samples were tested, and the obtained data matched well with the results from separate detection specified in Method for Chemical Analysis of Boron Ore (DZ/T 0422.1-2022). The relative deviation for each element was ≤2.26%, and the relative standard deviation (RSD, n=7) was ≤2.35%. Closed digestion ensures complete decomposition of boron ore samples and avoids volatilization losses of BF₃ and SiF₄. Aluminum trichloride effectively complexes fluoride ions and protects the ICP-OES injection system from hydrofluoric acid corrosion.