Dissolution methods for the determination of silicon in plant samples with inductively coupled plasma atomic emission spectrometry (ICP-AES) were examined. Plant samples (0.1 g) ashed by an electric furnace at 700°C were dissolved by three methods: an acid dissolution method, where the ashes were dissolved with a hydrochloric acid solution; an alkaline dissolution method, where the ashes were dissolved with a sodium carbonate solution; and an alkaline fusion method, where the ashes were fused with sodium carbonate salt. The effect of evaporation after dissolution was also examined. It was found that evaporation exerted a critical effect on the analytical results of silicon, i.e., complete evaporation reduced the results to about half that obtained with incomplete evaporation. Two tea leaf samples (commercial and sampled) with a low silicon concentration could be dissolved by all three methods when the resultant solution was followed by incomplete evaporation. The reproducibility of the silicon concentration with the alkaline dissolution method and acid dissolution method was about 3%, and the recovery of silicon after both methods was more than 95%. In the case of Magnolia leaves with a high silicon concentration, the alkaline dissolution method gave a greater concentration of silicon with better precision (5%) than the alkaline fusion method.
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