[tumblewush]

Just last week, I proposed research on the levels of lead, cadmium and chromium on the soil in a landfill here in my community as part of my undergraduate thesis, and I'm well aware of the problem that they had with my digestion method because I'm planning to look into lead.

I'm primarily digesting the soil using the average aqua regia mixture but of course this is going to be problematic for lead analysis because of precipitation (as of now I can only use the aqua regia method given the constraints, could have used triacid but we don't have a readily functional fume hood at the department at the moment (to be fixed), and we don't have a setup for perchloric digestion). I've looked up a few methods so that I can analyze the lead, and found a digestion that uses nitric acid (I'm planning to use this one, the result remains to be seen).

Just wanted to ask for some recommendations regarding what I could do, possible digestion methods that I could use. I know that there's no 100% efficient digestion, but any help regarding this would be appreciated.

[AWK]

After mineralization Pb is in the form of PbSO₄. This can be extracted in the form of complex with acetate, EDTA, TGS ...

[Corribus]

Are you doing this on a hot plate, or using something more sophisticated, like a microwave? You could also use an ashing oven, followed by acid digestion. What analytical method will you use to quantitate the lead? This may also impact the digestion method.

Your best resource for analysis of metals in environmental matrices is the EPA, which has published many standard methods for things like this. A quick google search "EPA lead analysis in soil" turns up a lot of hits.

E.g., take a look at this document, especially page 29 (this is for analysis of lead in soil deriving from lead paint).

https://www.epa.gov/sites/production/files/documents/92-006.pdf

The referred to SW-846 3050 method can be found here:

https://www.epa.gov/homeland-security-research/epa-method-3050b-acid-digestion-sediments-sludges-and-soils

This document gives very specific detail about how to digest soil samples for heavy metal analysis, including lead.

[tumblewush]

@AWK - My adviser initially suggested that I do the extractable form, and I'm taking that into consideration if all else fails. But does measuring the extractable account for total concentration?

@Corribus - Because of the limited resources at the university, I'm going to be doing this on a hot plate. And I'm going to be using FAAS to quantify the heavy metals that I'm going to be analyzing, forgot to mention this in the original post. Took a look at the links you gave me, and I'm going to give the method a test run at the lab with a few preliminary samples. Will be looking for more alternative methods as well.

[lohjxMARCUS]

Epa 3051. Digestiom using 9ml hno3 and 3mls hcl...both are concentrated solutions..will yield about ~90%