Recently, i am trying to detect ion contents in soil. The soil contains much aluminum and iron. I use 1 mL of nitric acid to digest the soil samples of 1g. This is conventional method to extract or digest ash. However, i failed to gain aluminum and iron information from ICP-AES.
What kinds of methods are suitable for testing soil sample which contains much aluminum and iron? I am thinking i should combine nitric acid and hydrochloric acid to prepare the ICP-AES samples for these test. But i do not know the dosage of acid, I need your help!
Sincerely!
Note:the soil was prior burned at 575 oC to remove organic matters.
Dear Kanhaiya Lal
Thank you for your reply. Yeah, we have microwave equipment to do the digestion. I am wondering if i should combined nitric acid and hydrochloric acid to prepare the ICP-AES samples for these test. Nitric acid only might not be useful for testing Fe and Al ions.
Dear Wu,
The soil, precisely the clay particles, is basically composed of alumino-silicate minerals, which is arranged in typical crystalline structure. Unless you break the basic structure of clay or soil, aluminium can not be extracted from it. For this, digestion of soil samples with a mixture of HF-HClO4 is recommended. Neither HNO3 alone nor a combination of HNO3 and HCl can be able to break this complex structure. Further, HF is corrosive to borosilicate glasswares. Thus, the digestion procedure should be carried out in platinum-ware. This digestion is sufficient for analyses of all kind of elements present in soil.
For analyses, very small quantity of soil samples ranging from 0.1 to 0.3 g is sufficient.
Since soil contains very large amount of aluminium and iron, the digested samples should diluted to a great extent before quantification in ICP-AES.
For details, I would recommend this book:
Jackson, ML (1971). Soil chemical analysis. Prentice Hall
Note: You don't need to burn the soil samples for determination of aluminium and iron.
With regards,
Sovan Debnath
Dear Debnath
Thank you for your kindly reply. The material we want to analyze is ash which burned in 575 oC. Because we want to know the ion component which involved in biomass. So the burning step might be required. I know HF and HCLO4 method, but for analyzed Al and Fe in ash, if HF is necessary? Could I use HCl and HCLO4 or HNO4 and HCLO4 to do the test? HF is too dangerous for our laboratory to use. Yeah, the first time i do the test, the capillary column was blocked due to low dilution multiples. Thank you for your kindly reminder!
Dear Wu,
The best mass of soil to acid digest is 0.5 g of your dry soil.
You can combine 2 mL of nitric acid (14,64 M) and 6 mL of hydrochloric acid (12 M) and incubate for 16 h. Then, you can heat your samples on a DigiPREP microwave for about 190 minutes (different heating phases). Filtrate and then complete to 50 ml before quantification on a ICP-AES.
Best regards,
Ramez Saad (Ph.D)
Reference: ISO NF 11464 and 11446
- Badges
- Science topic
- Similar topics
- Agriculture
- Soil Science
- Soil