Dear Sir,

Please check these researchgate links and PDF attachments.

https://www.researchgate.net/post/Is_there_any_alternative_analysis_for_soil_Iron_oxides

https://www.researchgate.net/post/how_to_estimate_free_iron_oxides_in_soil

Dear Dilip,

Iron, though in small amounts, is one of the minerals required by plants for a healthy growth. This mineral element is utilized by plants in the following forms: ferrous or Fe+2, ferric or the Fe+3 and the chelated or conjugated type.

The available Fe extract with diethylenetriamine penta acetic acid and triethanolamine buffer (0.005 M DTPA+0.01 M CaC12+0.1 M TEA) according to (Lindsay and Norvell, 1978). 10 g air-dry soil (passing through a 2 mm sieve) into a 125 ml Erlenmeyer flask, add 20 ml extraction solution, shake for 2 hours and then filter the suspension. Flask containing all chemicals but without soil will include as blank. The concentration of available Fe, will read by atomic absorption spectrometer (AAS) by using appropriate lamp. Extractable Fe in soil calculating by following formula:

Fe ppm = (Fe ppm in extract−blank) x A\Wt Where: A= Total volume of the extract (ml) Wt= Weight of air dry soil sample (g)

In plant total Fe analyze by dry digestion extract. Weight one gram finely powdered sample will take in porcelain crucibles and place in a typical muffle furnace, and the temperature will increase from 400 to 550°C and this ashing process will continue for 5 hours after attaining 550°C after 5 hours. When the material cooled, add 5 ml HCl 2 N solution into ceramic cup and mix with a plastic rod. After 15-20 minutes make up the volume (50 ml) using distilled water. Mix thoroughly, allow to stand for 30 minutes and then filtrate. then read Fe on atomic absorption spectrometer (AAS) by using appropriate lamp . Extractable Fe in soil calculating by above formula. wt : Weight of dry plant sample (g).

The extraction of naturally occurring free iron oxides from soils and clays 

with oxalate solutions is distinctly photosensitive. Apparently wave-

lengths around 366 m~, the near ultra-violet region, are the most efficient; 

this radiation is predominant in the emission of a medium-pressure 

mercury arc lamp. A qualitative consideration of the dissolution process 

indicates that in all probability electron transfer from solute to solid via 

intermediary C.zO~- is involved. Such a mechanism may explain the 

attack of near-neutral oxalate solutions upon natural ferric oxides and 

the decomposition of the quite resistant hematite in slightly acid media, 

when irradiated. The reaction appears to be autocatalytic. Electron 

transfer utilizing thermal electrons may also explain the attack of dithio-

nite ions upon ferric oxides, which was shown to proceed in media above 

neutrality. Finally, a detailed description of the method is given, in-

cluding the application for estimating free iron oxides in particle-size 

fractions obtained during the course of mechanical analysis. 

The selective removal of naturally occurring iron-oxide (mostly 

ferric oxide) minerals, generally called free iron oxides, from soils 

and clays is frequently required. It represents a serious analytical 

problem, as many of the clay minerals are extremely sensitive to 

attack under the conditions most conducive to dissolution of iron 

oxides, namely at low pH. Several methods have been proposed for 

this purpose (Tamm, 1922; Dion, 1944; Jeffries, 1947; Roberts, 

1947; Deb, 1950; Aguilera and Jackson, 1953; Mitchell and 

Mackenzie, 1954; Mehra and Jackson, 1960), all based upon the 

conversion of ferric oxides to ferrous compounds easily soluble in 

suitable media not far from neutrality. The methods currently in 

popular use are the acid ammonium oxalate method of Tamm (1922) 

and the sodium dithionite method in one or other of its guises (Deb, 

1950; Aguilera and Jackson, 1953; Mitchell and Mackenzie, 1954; 

Mehra and Jackson, 1960). The former has been shown by Schofield 

(1950; see also Deb, 1950) to be photosensitive, but no photosen-

sitivity of the latter has been observed. Currently, there is no in-

formation about the kinetics of the solution process, but a recent 

investigation into a photochemical modification of the acid am-

monium oxalate extraction has enabled a tentative assessment of the 

mechanics of dissolution. 

Method development for the determination of iron in milligram amounts of rice plants (Oryza sativa L.) from cultivation experiments using graphite furnace atomic absorption spectrometry has been [ublished in Anal Bioanal Chem. 2003 Sep;377(1):165-72. Epub 2003 Jul 12.). please see this link for details https://www.ncbi.nlm.nih.gov/pubmed/12861434

Thanks, Dr Malhotra. But I am looking for method for extraction and analysis of active Fe and Mn in soils, not in plants.