Basically under indian subcontinent conditions there is limited resources to conduct research. The availablity of xray fluorescent spectroscopsy is rare. So anyone can tell me other instruments and method from which we could estimate the silicon content of soil?
Silicon estimation can be done in general by any of these methods - Gravimetric methods, Volumetric methods, Colorimetric methods, atomic absorption spectroscopy, flame photometry, atomic fluorescence spectroscopy, atomic mass spectrometry etc apart from X-ray fluorescence.
what are you interested in? Total Si or plant available/extractable Si?
Dear Chetan,
To estimation of Si, you can use Gravimetric, Volumetric, Colorimetric, atomic absorption spectroscopy, flame photometry, atomic fluorescence spectroscopy methods as it Mr. V N mentioned already. you can go through attached file, may be it would be positive for you.
Well professor Ewald I was interested in calculating both total Si and plant extractable Si but we are lacking atomic fluoresence spectroscopy in our university. Is there any other than this method to calculate silicon?
there is definitively no better choice than X-RF and this best after borate combustion.
Total SiO2 (silica) is estimated by total chemical analyses of soils using sodium carbonate fusion.
The soil/clay in 100 mesh are taken in Pt crucible and mixed well with podered sod carbonate (anhydrous) and put in furnace to a temp of ~1000 deg C.
The lump is dissolved in 6N HCl and filtered by Whatman filter 44 or others (ashless).
The yellow coloured dissolved salts are collected usually in 250 ml vol flask ...the materials collected in the filter paper is burnt in and weighed to get silica. From this value you can calculate Si.
Pl see Jacson's book of chemical analysis of soils
or
Norman F E Bear's chemistry book...at the end of the chapters this method is detailed. Good luck
The extraction and measurement of soil Si is well treated by previous contributors, However, if you want to measure available soils Si, at some tine you must measure Si in plants, which is what I address. First I say that XRF is still a good technique for plant Si; however XRF must be calibrated using chemical measures. Many plant species do not contain sufficient Si concentrations for gravimetric methods to be practical; consequently most plant Si measurements are done using the silicomolybdate reaction on extracted Si. Unless you use HF during acid digestion, Si recovery is low and variable. Ashing, followed by fusion with an alkaline flux such as Na2CO3 can give good recovery in the hands of experienced analysts. However, suspension of ground plant material in dilute HCl, with added HF, in a polythene bottle with warming (say overnight) is convenient and effective. For safety, XS HF is converted to fluoroborate by adding boric acid solution to the reaction bottle before colorimetry.
We consider 0.01 M CaCl2 extractable Si as soil available Si.
what is "soil available Si, dear Anoop? When addressing plant available Si you need to keep in mind that there are three general types in terms of Si uptake mechanism in the plant kingdom: active accumulators like Oryza and Equisetum specs., active excluders like Brassica specs. (and most of the monocots) and passive specs. like most of the Gramineae!
Good evening sir in our university we have only atomic absorption photometry how can estimate si content in soil if pdf is there about method please share me.
1-Measurement of Soluble Si : 2 g soil was poured into a 50 ml falcon tube, into which 20 ml of 0.01 M CaCl2 was added. Next the mixture was shaken at 180 rpm for 1 h and then centrifuged at 3000 rpm for 5 min. After that, it was immediately filtered, and the concentration of Si in the extract was read by using an atomic absorption spectrometer, Agilent AAS-240FS.
2- Measurement of Exchangeable Si : To determine this fraction, 20 ml of 0.5 M acetic acid was added to the falcon tube of the previous step and shaken at 180 rpm for 1 h. It was then centrifuged at 3000 rpm for 5min. The mixture obtained was immediately filtered, and the concentration of Si in the extract was read by using an atomic absorption spectrometer, Agilent AAS-240FS.
3- Measurement of Soil Amorphous Si : For this purpose, 40ml of 0.5Msodium carbonate was added
to the falcon tube of the second step, shaken at 180 rpm for 16 h, and centrifuged at 3000 rpm for 5 min. After that, it was immediately filtered, and the concentration of Si in the extract was read by using an atomic absorption spectrometer, Agilent AAS-240FS.
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