Simultaneous determination of aluminum trioxide,silicon dioxide,and magnesium oxide in montmorillonite raw materials and their formulations using secondary microwave digestion inductively coupled plasma mass spectrometry technology
Objective:To establish a method for simultaneous determination of aluminum trioxide,silicon dioxide and magnesium oxide in montmorillonite and its preparations.Methods:The method was optimized and estab-lished for simultaneous determination of aluminum(27Al),silicon(28Si),and magnesium(24Mg)in montmoril-lonite using rhadium(103Rh)as the internal standard,a dilute nitric acid hydrofluoric acid saturated boric acid solution with secondary microwave digestion and inductively coupled plasma mass spectrometry(ICP-MS).The method was compared and analyzed with the EDTA volumetric method for the determination of aluminum trioxide,the muffle ignition combustion method for the determination of silicon dioxide and the AAS method for the determi-nation of magnesium oxide after melting samples of lithium metaborate in the USP.Results:The linear of alumi-num(Al)and silicon(Si)were in the range of 25-300 ng·mL-1.The linear of magnesium(Mg)was in the range of 20-240 ng·mL-1,r ≥0.999.The detection limits of Al,Si,and Mg were 0.49,1.30,0.71 ng·mL-1.The average recoveries were 99.7％-100.6％,99.9％-101.2％,99.8％-101.2％,and the average repeatability RSDs(n=6)were 0.3％-1.3％,0.4％-1.2％,and 0.4％-1.0％.The contents of aluminum trioxide,silicon dioxide and magnesium oxide in montmorillonite,montmorillonite powder,and mont-morillonite dispersion tablets were determined using the newly established method and the original standard meth-od,and the measurement results were basically consistent.Eight common peaks were identified from fingerprints of 10 batches of samples.The RSD values of relative retention time of 8 common peaks of chromotograms of sam-ples were all below 0.5％and the similarities were above 0.9.The contents of aluminum trioxide in montmorillon-ite were determined using the newly established method and the original standard method,which were 2.3％to 2.4％,2.0％to 2.2％,58.7％to 61.5％,55.3％to 59.4％,and 15.9％to 20.6％,14.6％to 19.4％,respectively.The results of the measurements were basically consistent for the determination of aluminum trioxide,silicon dioxide,and magnesium oxide content in montmorillonite raw materials and formulations.Conclusion:The newly established content determination method uses a combination of secondary microwave digestion and ICP-MS technology to determine the content of aluminum oxide,silicon dioxide,and magnesium oxide in montmoril-lonite samples.It is simple,fast,sensitive,and accurate,and can be used.
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