Hello,
I used following method for Soybean leaf tissue nutrient content analysis (Soybean leaf - 3rd full leaf from top, sampled at 50 days),
1) 0.5 g leaf tissue- oven dried, crushed thr 2 mm
2) Soaked in 5 ml HNO3 (conc 70%) over night. Next morning, heating at 125 C till digest of 2-3 ml remains in the beaker.
3) Cool and drop by drop addition of 5 ml H2O2 and heating at 80 C till moist residue remains.
Problem faced: Recommendation is to repeat addition of H2O2 till white or colourless residue remains. A cumulative of 30 ml H2O2 addition has been done, yet unable to get a complete white or colourless residue (approx yellowish residue 10% of initial amount still in the beaker)
Please give advice if there has been a error.
OR if it is not necessary to get colourless or white residue and I can just go ahead with the filtration after 2-3 repeat H2O2 addition.
OR any other digestion methods be followed?
Pls note, for this experiment I am in a very remote rural location, microwave digestion equipment or muffle furnace isnt available. Also have to cover 5 such locations, so sampling and acid digestion on site is feasible option. Once extracts made, I can store it and transport to lab in city for analysis with ICP.
Kindly guide me a feasible solution to deal with this situation.
Thanking you in anticipation
I think, as long as final digest is free of any turbidity , there is no harm with ICP-based analyzis..
You may repeat the Step 2 before proceed to Step 3. This is to ensure any residue is completely dissolve. After Step 3 you may need to filter before ICP. A clear solution will be good for ICP.
Wet digestion method for soybean leaf tissue analysis may be followed by Nitric and Perchloric acid( 10:4) .In a 100 ml of conical flax 5 ml of digestion mixture in a 0 .5 gram of plant sample should digested on a hot plant at about 250 degree centigrade till white fumes in the neck of the conical flax. Excess digestion mixture may be added for another 5 ml till the white fume evolved through conical flax Cool the conical flax and add distilled water of suitable amount in the conical flax contains digested sample . Filter with whatman no-42 filter paper in a 100 ml of conical flax or centrifuge for supernated liquid for estimation in ICP insturument.
Wet digestion method for Soybean leaf tissue analysis correction may be made for Filter with Whatman no 42 filter paper in a 100 ml of volumetric flax and make up to the mark with distilled water .and centrifuge for supernated liquid for estimation in ICP instrument.
Digestion should be done on a hot plate at about 250 degree centigrade till the white fumes evolved from the digestion mixture to complete the digestion.
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