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ABSTRACT
Silicon (Si) is classified as a beneficial element in higher plants. Although there is an abundance of literature on Si extraction and analysis in graminaceous crops such as rice and sugarcane, there is limited information on the validation of these methods for most dicotyledonous horticultural crops. These methods include gravimetric extraction, which requires a larger sample size the smaller the Si content in the test plant. A autoclave inductive digestion is considered effective by some and criticized by others due to the use of a strong oxidant and its sensitivity to the level of Si in the plant material. Microwave digestion method occurs in a closed system, which avoids contamination, is quick and results in a high recovery rate due to its high extraction temperature. The aim of this experiment was to validate Si measurement following microwave digestion using inductively coupled plasma optical emission spectrometry (ICP-OES) and molybdenum blue colorimetry. The recovery of Si additions as SiO2 was 82%-96% by ICP-OES and 85–94% by colorimetry. The recoveries did not differ between measurement methods (P > .05) but the ICP-OES results were more consistent. The limit of detection for Si determination by means of ICP-OES and that for the spectrophotometry method were 48 µg L−1 and 200 µg L−1, respectively.
Acknowledgments
The author wishes to thank the Agricultural Research Council: Institute Soil Climate Water for providing me with laboratory facility and technical assistance during the method validation phase. The author wishes to thank Mr T Matema from ARC for reviewing the methodology of this paper. The author also wishes to thank the National Research Funds and Citrus Research International for funding this research.