If I use 0.5 g soil + 9 ml HNO3 + 3 ml HCI for microwave digestion. And I take only 5 ml of supertant from this digest and dilute it to 25 ml, by adding 5 ml of 5 % KI and 5 % ascorbic acid for decreasing of As (V) to As (III) and the rest (15 ml) distilled water.
What would be my WF, VF, CF and DF?
I know that : Actual Conc. = Conc.* VF * DF * (CF/WF)
for AAS, however I am confusing WF,VF,CF,DF during calculation.
ICP-MS is one of the best tool for determining the As in digested soil sample.
If you could decipher your mysterious abbreviations (DF, WF, CF, VF). I might help you. Oh, by the way, what is Kl?
I know that ICP_MS is the best however, we do not have ICP-MS in our laboratories that is the reason I am using Atomic Absorption Spect. Dear Refal,
DF:Dilution factor, WF: Weight Factor, CF: Correction Factor , VF:Volume Factor
KI: Potassium ıodide
Another one method is available for determination of As in soil with the help of 0.5 M NaHCO3. This method suggested by Olsen et al (1954). Extracting the soil with 0.5M NaHCO3 and filterate with whatman 42 paper and the filterate will be measured by ICP-MS..
Dear Beste
Please, don't get me wrong, but I am under strong impression that you really like to complicate your life. First of all, why are you using reversed aqua regia instead aqua regia? There is an ISO standard for this ISO 12914:2012 Soil quality -- Microwave-assisted extraction of the aqua regia soluble fraction for the determination of elements.
Why do you take only 5 ml of supernatant? Why do you add KI and ascorbic acid. Why do you want to decrease As (V) to As (III)? Oxidation state does not matter in this case. You are performing total content analysis not speciation analysis. Addition of the additional reagents is not necessary. It is only additional work for you and it may have an influence on the analysis result (matrix effect, interferences). Please reconsider your digestion procedure.
Content calculation issue. Calculate the content of the element in the following way:
concentration from AAS*12/sample weight*5
Just be careful about the final unit whether it is mg/kg or ug/kg It depends in which units you have programmed in your AAS.
Hope this helps, but in case of further questions, please feel free to ask.
Just one remark about ICP-MS. It is a great machine but in case of arsenic and aqua regia or hydrochloric acid or chlorides, you have to be very careful. Arsenic is very vulnerable to interferences.
Also measuring As in 0,5M NaHCO3 is quite a challenge due to the strong matrix effect
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