Hi everyone
I try to assess lead content in earthworms samples. He thought that the content in worms could be evaluated at a microwave system (190ºC, 45 minutes, 1ATM) with an acid mixture (1/3 HCl+HNO3) as a soil sample or a metal digestion of plants.
Although some authors apply this methodology or modified (microwave system but with 140 C for 7 h), other authors only make an acid digestion HCl+HNO3 but not in a microwave system... on a heating plate at 50º or 100ºC during 2 to 9 hours, filtrate with warthman paper and make to 50 or 100 ml of volume with ultrapure water like in a acid digestion to isotope analyses.
Which is the best method to assess the lead content in earthworms? Why this differences in methodology to assess lead content in earthworms?
Regards
Dear Andreas
I did some earthworms digestion in the past. I used microwave digestion in closed vessels with HNO3 and H202. I used three step digestion, first 190ºC, then 200ºC and finally 210ºC (each step for 5 minutes). To check the efficiency and correctness of your digestion, please use some Certified Reference Materials. Don't forget to let the earthworms empty their digestive tract prior to digestion, otherwise you will rather measure the content of lead in the soil that present there than in the tissue. Another issue is the drying. I used freeze drying before digestion. After that procedure there was no need for filtration as the solution was clear and free from precipitate.
The differences in the methods comes probably from different needs and different equipment that laboratories possess. If the laboratory does not have microwave digestion system, they will most likely use hot plate digestion. There is no ISO standard for that kind of analysis so people tend to create their own procedures.
Cheers
Rafal
The variation of methods should consider the chemical constituents found in given specific type of earthworms. The other heavy metals and chemicals consumed by earthworm have to be separated from lead.
Both microwave digestion in acid or acid digestion can be used for assessing lead contents in earthworms after clearing the gut contents. The adoption of different methods is mainly because of the standardized protocols and lab. facilities available.
I do not think , you need to adopt some special techniques of lead analysis in earthworm samples. Neither , you need any big optimisation in analysis. Simple conventional acid digestion or microwave digestion as per your availability will be good before analysis being carried out on AAS/ICP.
Either microwave 180 C 10 min in 5 mL HNO3 (this should be sufficient for a U.S. earthworm, lead should be soluble), then dilute into water. Or in a fluoropolymer (PFA)tube, for every gram earthworm, add 2 mL HNO3. Cover the tube, place it in a boiling water bath. Do not fill the tube more than half full and point it away from people. Heat 30 minutes.
O calente con microondas 180 C 10 min en 5 mL de HNO3 (esto debería ser suficiente para una lombriz de tierra de Estados Unidos, plomo debe ser soluble), luego diluir en agua. O en un tubo de fluoropolímero (PFA), por cada gramo de lombriz, agregar 2 mL de HNO3. Cubrir el tubo, colocarlo en un baño de agua hirviendo. No llenar el tubo más de la mitad y puntelo a fuera de otra gente. Calente 30 minutos y diluir.
Thank you for all !!
I see that every lab can apply any methods and not have a standardized methodology like a aqua regia for soil samples..
Thanks
dear dr. Andres Rodríguez-Seijo making empty their digestive tract prior to digestion and freeze drying before digestion then following the procedure described by Dr. Andres Rodríguez-Seijo would be a better choice I guess .
- Badges
- Science topic
- Similar topics
- Agricultural Science
- Soil Science
- Soil Analysis