We extract the available heavy metals from soils by DTPA (diethylen triamine penta acetic acid) solution buffered at pH 7.3 as described by Lindsay and Norvell (1978) , but when we inject the extractable in the Inactivity Coupled Plasma Emission (ICP 6200) , the system is turned off.
We want a recommended method for extracting the available soil heavy metals that is compatible with the (ICP 6200) system
DTPA (diethylen triamine penta acetic acid) solution buffered at pH 7.3 as described by Lindsay and Norvell (1978)is best method to extract metal. Do some modifications to obtain optimum yield. Acetate-ammonium buffer solution is also used for metal extraction. Metal solubilizers are needed to increase the extraction yield.
Your DTPA extracting solution is too high in salts, that shut off the plasma. Try to dilute your solution by 10 or 100 times with deionized water. Most ICP can read fairly low metal concentrations.
There are several types of solutions for the extraction of mobile forms of heavy metals (microelements) in soil. I have prepared a solution of 0.01 M EDTA with 1n CH3COONH4at pH 7, wich we obtained good results in simultaneous extraction of microelements with nutritional rol (Fe, Mn, Cu, Zn).
Perhaps it would help usig the sequential straction procedures techniques, as the BCR, Tessier, etc. It depends on what you need to determine.
There are several methods for one-step extraction of bavailable heavy metals, such as 5％ HNO3、1M HCl、0.05M EDTA、DTPA、CaCl2、NH4AC，0.11M HOAC
DTPA is generally used to extract the "soil available heavy metals" that can be used by the plants. If you really need that pool of heavy metals then you have to use the DTPA (whatever concentration you are using to get the optimum recovery) but before ICP analysis you need to dilute the extractant many fold using DI water as suggested by "Nguyen". Most of the ICPs can go to sub-ppb or ppt level (check the detection limit of your ICP).
If you want to use any other extractant to get the labile pool of heavy metals, you can read the following paper to get some idea of the extractants than can be used.
http://www.sciencedirect.com/science/article/pii/S0003267013007678
I suggest you adopt ecological methods, for example, look for plants in the region that have the characteristic of photoremediation. Ie having an ability to extract or accumulate heavy metals.
DTPA method is the best suitable method for extracting heavy metals. Please dilute it as mentioned by Nguyen Hue and also Mohammed Javed to get reliable results as most of the ICPs could detect up to ppb levels. Thanks.
DTPA method is a very good one if you are going to use AA or similar equipment. In case you use ICP, it is better to use diluted solutions of DTPA in order to find the appropriate matrix that doesn't interfere with the ICP measurement, once you have the optimum dilution you can apply to your samples. Furthermore, you can use BCR procedures or the first steps of a SEP (soluble+exchangeable fractiosn and, depending on your type of soil the OM labile fraction)
Another thing that you might check on is to see if you are using an Argon humidifier on the ICP. The use of the humidifier along with a glass concentric nebulizer will help with high salts samples. You might also check and see of they make a "high salts" torch for the ICP 6200 system). I am familiar with that system but know that some other ICPs have high salt torches (i.e. they are just usually a larger bore) and I have successfully ran samples with the larger bore torches when the small ones would not sustain a plasma.
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