Digestion of Pb-alloy for ICP-OES analysis

[mpotocni]

Hello everybody,
I am looking for a disgestion procedure of Pb-alloy, so that we can measure the elements with ICP-OES.
Pb should be removed, that it doesn't contaminate the system.

So far we used HCl for digestion, but the results weren't very good.

Elements of interest are: Sn Sb Bi Cu Cd As Zn Ni Ag Tl Al Te

I hope anyone can help me.

Thank you very much!

 

[Kevin McHugh]

Try aqua regia, it is a mixture of nitric acid and hydrochloric acid. I forget the ratio, you'd have yo google that. I'm not sure what you mean lead contaminates the system. ICP is commonly used for lead analysis.

 

[mpotocni]

Thank you, I'll try. Sometimes we have problems with measurements of solutions with high content of Pb or some other elements. Intensities of internal standard decrease and during rinses don't increase again (to the level at the beginning of the measurement).

Thank you for help again.

 

[Kevin McHugh]

Are you looking for trace elements in a lead matrix?

 

[mpotocni]

Hello,
I'm looking for these elements in approx. these concentrations:
Ag 20 mg/kg
Al 50 mg/kg
As 10 mg/kg
Bi 250 mg/kg
Cd 90 mg/kg
Cu 80 mg/kg
Ni 2 mg/kg
Sb 80 mg/kg
Sn 450 mg/kg
Te 200 mg/kg
Tl 3 mg/kg
Zn 70 mg/kg
Ca 60 mg/kg

Matrix is Pb, and I don't need the concentration of Pb.

Thank you!

 

[Kevin McHugh]

OK, I see the problem. If possible, you would like to digest the sample, and selectively precipitate or separate the lead from interfering with the other analytes. Have you looked at ion selective membranes? There may be a commercial product for this application. My suggestion is to get with the techies from your ICP manufacturer. They are usually up to speed on state of the art separation technology for elemental analysis.

 

[Borek]

If the amounts of other things are so low I am not convinced selective precipitation will work - I would expect coprecipitation to remove substantial part of the cations you are interested in.

Just intuition, not backed by a quotable research.

 

[Kevin McHugh]

If the amounts of other things are so low I am not convinced selective precipitation will work - I would expect coprecipitation to remove substantial part of the cations you are interested in.

Just intuition, not backed by a quotable research.

You are correct. Most anything that will precipitate lead will precipitate some of the analytes as well.

 

[mpotocni]

Thank you, yes, I don't want other analytes to precipitate.

What do you think of these 2 procedures of digestion:

1. Tartaric acid+nitric acid
2. HCl
Filter Lead precipitate.
(will probably also other analytes precipitate or not?)

Or:

1. Tartaric acid+nitric acid
(A lot of lead? Any other problems occur?)

And measure by ICP-OES.

Thank you.

 

[Kevin McHugh]

Does you anaysis have to be done by ICP? Do you have access to a mass spec? PIXE (proton induced x-ray emission) analysis is a decent way to go, but IMO it is a better qualitative tool than an analytical one (I'm sure some folks would argue that). The nitric and hydrochloric make aqua regia which will dissolve all but the most intractable metals (e.g. titanium dioxide). I'm not sure about the solubility of the tartrate salts, you'd have to look that up.

 

[mpotocni]

Thank you for response,

I only have access to ICP-OES.
Some company suggested that I use water: HNO3=1:1. I'll try and see what happens.

With aqua regia we didn't get good results.

 

[Kevin McHugh]

How have you prepared your standards? Which elements is lead interfering with, it can't be all of them. I am not familiar with all the elements listed, but the nitrates should be soluble. Have you tried doping your standards with lead to find the exact interferences?

 

[mpotocni]

We still have to check interferences, but at first we wanted to find digestion procedure.

Adding tartaric acid+nitric acid and then HCl seems to give good results.

Thank you.

 

[MRBlizzard]

A different method might be Atomic Absorption Spectroscopy.

https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy

 

[Kevin McHugh]

I think you'd run into the same interference problems with flame AA as ICP. The only difference in the two methods is the method of excitation.