Soil extractants

Soil extracts are usually very complex. In water samples, humic and fulvic acids make analysis difficult, especially when polar substances are to be determined. Multidimensional chromatography can also make a significant contribution here to this type of analysis. 

Important developments in LC-GC have been made by Grob and co-workers (79-81) and by the Brinkman group (82-87), who have mainly studied the application of this technique to environmental analysis. This coupled technique has usually been applied to water, although air and soil extracts have also been analysed. 

Pyrocystis lunula (clone T37) can be grown under light-dark cycles as well as under continuous illumination at 20 2°C, in f/2 medium (Guillard and Ryther, 1962) with 0.5% soil extract instead of silicate (Guillard, 1974). The growth is somewhat slower and harvesting may be carried out about 40 days after inoculation, at a cell density of 15,000-20,000 cells/ml. 

Sediment soil Extract of sample with methylene chloride acetone (1 1) clean-up extract using Florisil column GC/ECD 0.002 pg/g (ppm) ( "endosulfan) 0.004 pg/g ( "endo-sulfan) 0.004 pg/g (endosulfan sulfate) No data Marsden et al. 1986... 

No TCDD could be detected in soil with a detection limit of less than 1 ppb. Gas chromatographic (GC) traces at the left of Figure 1 represent a soil which would have contained 5 ppb of TCDD traces at the right are the unamended soil extracts. Arrows indicate the position where TCDD would occur. At the bottom right is a trace of the extract from a soil amended at the 1 ppb TCDD level. 

Paper chromatography of inositol phosphates obtained from soil extracts is described. ... 

Mobilization of inicronutrients such as Zn, Mn, Cu, and Co and of heavy metals (Cd, Ni) in soil extraction experiments with root exudates isolated from various axenically grown plants is well documented (61,204-206) and has been related to the presence of complexing agents. 

Propanil and its metabolite in the n-hexane phase of the soil extract derived from Section 3.2.2(2) are passed through a Florisil column (previously activated at 300 °C overnight and deactivated with 2% water 2 g). Propanil residues are eluted with 20 mL of diethyl ether-n-hexane (1 1, v/v). 

A 20-g sample of air-dried soil is extracted with 100 mL of ethyl acetate in a flask shaker for 45 min. After shaking, the extract is decanted and separated. The soil is re-extracted with 100 mL of ethyl acetate for 45 min. The combined soil extracts are filtered through a Whatman No 1 filter paper and the filter cake is washed with an additional 20 mL of ethyl acetate. The extracts are evaporated nearly to dryness, under vacuum, using a rotary evaporator. The residue is dissolved in an appropriate volume before GC analysis. ... 

The GC/FID conditions were as follows column, 1.5% OV-17 (2 m x 3-mm i.d.) glass column N2 carrier gas flow rate, 45mLmin temperature of injection port, column and detector, 240,235 and 235 °C, respectively. The recoveries of these amino derivatives with fortification level ranging from 0.5 to lO.Omgkg" were 62-101% for chlornitrofen, 62-101% for nitrofen and 58-101% for chlomethoxyfen, and satisfactory recoveries from soil were obtained at high concentrations, but the recoveries at lower concentration averaged about 66% for the least recovered compound. Interference from other substances in the soil extracts derived from the acetylation reaction was negligible. 

Soil extraction solvent is prepared by dissolving 15.4 g of NH4OAC in IL of 0.125N aqueous HCl and mixing the resultant solution with 4 L of ACN. 

The extraction method for prohexadione-calcium in soil was developed using alluvial soil and volcanic ash soil. Extraction by shaking the soil with a mixture of 1N sulfuric acid-acetonitrile (1 3, v/v) and/or of 1N sulfuric acid-acetone (1 3, v/v) showed an acceptable extraction recovery efficiency. 

An efficient and reproducible extraction procedure is mandatory when analyzing agrochemicals in soil. An overview of common soil extraction techniques is given below. 

A commonly used extraction technique involves shaking soil with a suitable solvent on a mechanical shaker at about 300 rpm. After extraction, the soil extracts are collected by centrifugation followed by decantation or filtration. This technique could be used for any amount of soil samples (from 10 to >100g). Soil samples greater than 100 g require efficient agitation to achieve acceptable recoveries. 

Macroporous diatomaceous column (e.g.. Chem Elut column). The combined soil extract is concentrated to dryness under vacuum, the residue is dissolved in 15 mL of water and the solution is applied to a Chem Elut column. After charging for 20 min, acetamiprid is eluted with 100 mL of dichloromethane. The eluate is evaporated to... 

Extraction. Centrifuging the soil extract in the screw-capped vial can easily break the solvent emulsions that often form during extraction. The vial can survive up to 6000 centrifugation if rubber stoppers are inserted into the centrifuge cup to provide a flat base to protect the vials. The desired phase (usually the upper) can be easily removed with a pipet or, if it is to be discarded, it can be removed using a disposable pipet connected by tubing to a suction flask and a vacuum line. 

Soil is extracted twice with methanol-1 N hydrochloric acid (3 1, v/v), centrifuging between each extraction. An aliquot of the combined soil extract is diluted with acidified (pH 1)5% (w/v) sodium chloride solution and subjected to liquid-liquid partitioning with dichloromethane. The dichloromethane extract is evaporated and the residue is dissolved in mobile phase prior to quantitation by LC/MS/MS. 

After extracting fluthiacet-methyl from the soil extract with n-hexane, pass the residual aqueous layer through a dual cartridge of Sep-Pak Plus NH2 and Sep-Pak Plus C18 to adsorb the free form of fluthiacet-methyl on Sep-Pak Plus Gig. Remove the Sep-Pak Plus C18, wash it with 0.5% acetic acid and acetonitrile-water-acetic acid (20 80 0.5, v/v/v), elute with acetonitrile-water-acetic acid (50 50 0.5, v/v/v) and quantify the free form by HPLC. The operating conditions for HPLC are the same as those for fluthiacet-methyl, except that the mobile phase is acetonitrile-water-acetic acid (50 50 0.5, v/v/v) (retention time 8.8 min). 

Transfer the soil extract (from Section 6.1) into a 1000-mL separatory funnel, add 200 mL of water and 10 mL of saturated sodium chloride solution, and extract the sample with 100 mL of dichloromethane three times. Dry the dichloromethane extract with anhydrous sodium sulfate in a funnel in a similar manner as described for juice, pulp and rind, and collect the dried solution in a 500-mL round-bottom flask. Evaporate the dichloromethane under reduced pressure. Dissolve the residue in 3 mL of benzene. 

For soil. Extract 50 g (dry weight, containing about 5 g of the water) of the soil sample similarly as described above, using 95 mL of the distilled water. 

Adriano DC, Delaney MS, Hoyt GD, et al. 1977. Availability to plants and soil extraction of americium-241 as influenced by chelating agent, lime, and soil type. Environ Exp Bot 17 69-77. 

Improved Methods for Collection, Bioassay, Isolation, and Characterization of Compounds. Techniques used to characterize natural products are evolving rapidly as more sophisticated instrumentation is developed. Plant physiologists and chemists should work closely together on this aspect, since rapid and reproducable bioassays are essential at each step. There is no standard technique that will work effectively for every compound. Briefly, isolation of a compound involves extraction or collection in a appropriate solvent or adsorbant. Commonly used extraction solvents for plants are water or aqueous methanol in which either dried or live plant parts are soaked. After extracting the material for varying lengths of time, the exuded material is filtered or centrifuged before bioassay. Soil extraction is more difficult, since certain solvents (e.g. bases) may produce artifacts. 

Bloassays are useful tools for detecting physiological activity of substances (allelochemlcals) In plant and soil extracts and for following activity as extracts are purified and the components separated Into various fractions. Frequently, a bloassay detects physiological activity at concentrations much lower than the sensitivity of chemical tests. The choice of a bloassay depends upon the amount of chemical available for testing, the suspected physiological activity of the allelochemlcal, and the sensitivity... 

Soil Extract with distilled water, filter, pass through C18 sorbent, elute with chloroform, add internal standard GC/FID No data 66 7% Tomes et al. 1991... 

Soil Extract using ultrasonic vibrations GC/FID/FPD/MS No data No data Sawyer et al. 1992... 

Soil Extract with ethyl acetate, filter or separate, dry, concentrate GC/AFID No data No data Spanggord et al. 1979... 

Wolff MS Mount Sinai School of Medicine of CUNY, New York, NY Analytical support for comprehensive assessment of lead exposures body burden measures will include blood lead, plasma lead, ZPP, bone lead, representing multiple compartments for deposition of lead and widely variable rates of elimination measurement of total lead in soil extracts to validate quantitative measures National Institute of Environmental Health Sciences... 

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