ICP-OES: HNO3- or HCl-matrix?

[hydra]

Dear all,

I have water samples (regular, run of the mill dilute river water)
that I plan to analyze for alkali and alkali earth metals using ICP-
OES. Some of these samples are in 1% HCl matrix, which may cause
corrosion to the equipment and, for all I know, cause interferences.
Would I be better off adding concentrated HNO3 to my samples that are
currently in 1% HCl or just leaving them as are? I'm hoping that
adding the nitric acid will convert the Cl- to Cl2(g) but I'm not sure
if that will actually happen. My concerns are mainly about
interferences and possible matrix effect of the HCl, but also about
corrosion since I'll be running a lot of samples. Any insight or
advice is warmly appreciated.

[Marvin]

Post by hydra
Dear all,
I have water samples (regular, run of the mill dilute river water)
that I plan to analyze for alkali and alkali earth metals using ICP-
OES. Some of these samples are in 1% HCl matrix, which may cause
corrosion to the equipment and, for all I know, cause interferences.
Would I be better off adding concentrated HNO3 to my samples that are
currently in 1% HCl or just leaving them as are? I'm hoping that
adding the nitric acid will convert the Cl- to Cl2(g) but I'm not sure
if that will actually happen. My concerns are mainly about
interferences and possible matrix effect of the HCl, but also about
corrosion since I'll be running a lot of samples. Any insight or
advice is warmly appreciated.

Mixing concentrated HCl and HNO3 makes aqua regia, not Cl2.
Mixing the dilute acids won't either. It will add ot the
corrosion. And I don't know what matrix effects it will
decrease.

[Samite Alchemist]

HCl is no problem on ICP. The standard prep (EPA) for aqueous samples
uses HCl and HNO3. Just depends on what you are trying to keep in
solution.

ICP-MS is another story. Chlorides cause many polyatomic
interferences.

This much is true: HCl solutions tend to corrode exposed metal
surfaces. To minimize corrosion from airborne vapors, leave solutions
capped until ready to analyze.

[JJ]

Alkali metals are not the best by ICP, AA tends to be better. But
water samples tend to be high enough no problem. You do not need to
add acid at all for alkali metals - completely ionized anyway. Water
that is high in alkalis will give you some background issues. An ICP
worth anything can handle these acids no problem. Alloy analyses are
run with aqua regia, etc. all the time (it is routine in our labs). HF
solutions (silicon in aluminum etc.) - no glass but that is easy
enough. This is a simple analysis especially if this is just tap
waters. Ion chromatography is prefferd by many.

Post by hydra
Dear all,
I have water samples (regular, run of the mill dilute river water)
that I plan to analyze for alkali and alkali earth metals using ICP-
OES. Some of these samples are in 1% HCl matrix, which may cause
corrosion to the equipment and, for all I know, cause interferences.
Would I be better off adding concentrated HNO3 to my samples that are
currently in 1% HCl or just leaving them as are? I'm hoping that
adding the nitric acid will convert the Cl- to Cl2(g) but I'm not sure
if that will actually happen. My concerns are mainly about
interferences and possible matrix effect of the HCl, but also about
corrosion since I'll be running a lot of samples. Any insight or
advice is warmly appreciated.