what is the washing solution you use? You can rinse with 5% HNO3 in distillated water. Never use HCl.

I hope that it will be help you.

Regards

Thanks Morin jean-charles

I use washing solution 2% HNO3 in deionized water.

But I have memory effect for Hg and Sb

There is no perfect solution but HCl (~0.7 M) is better than HNO3. You can perform a final rinse with pure H2O or diluted HNO3 to remove Cl before next sample. Take care of this: relative decrease of remaining concentration is slower as concentration decreases. It takes much more time to decrease from 1 ppb to 0.1 ppb than to decrease from 1 ppm to 0.1 ppm. This is because tubing acts as a poor chromatographic column where the adsorption sites number decreases when strength increases. The strongest adsorption sites are saturated for high concentrations and are not seen. For low concentrations, these sites release back slowly the adsorbed metal giving a larger memory effect. Hg appears a sticky metal because it is often analysed at low concentration. Fe has the same behaviour.

Thanks Remi Losno

But as you know the presence of Cl can affected in the detection of As.

If I use HCl as rinse solution in my multi elements determination as you say this don't cause an error with As?????

HCl is quickly removed by water or HNO3 and will not remain in tubing after rinse, but be aware of the presence of Cl in your samples!! Other thing: Hg must be in its highest oxidation state (HgII) in an oxidative solution (no dissolved organic molecules), otherwise you may form Hg(I) which is really an issue.

Remi Losno

I see that your answer is very clear and perfect, but the ICP-MS use mass per charge ratio (+1); to avoid mass interference resulting from double charge.

I agree with Sherif Elgammal before each analysis daily performance check was preformed to check sensitivity and also double charge percentage which must be less than 3% and oxide compounds percentage which must be less than 2.5%. Rémi Losno

I recommend to always use isotope dilution for Hg, otherwise it will be off compared to standard CVAAS measurement.

Thanks @ Lars-Eric Heimbürger-Boavida

How I can use isotope dilution for Hg in multi-elements determination.

This way not affect another elements detection??????

You can use commercially available enriched spike solutions (for instance 199 iHg), making sure they are clean and measured for small impurities.

Though if you are only interested in total Hg, i’d probably just go with a cheap CVAAS analysis for solids, or CVAFS fir aqueous solutions. Make sure your method is clean for Hg.

Thanks again @ Lars-Eric Heimbürger-Boavida

I know CVAAS and CVAFS are cheap instruments but these equipment are specified for Hg only.

I use ICP-MS for multi-elements determination included ( As, Pb. Cd, Fe, Cu, Hg, Sb, .............ect.) and the problem of the memory effect was appeared with only Sb and Hg.

I normally construct Hg calibration curves up to 20 ppb and use a 3 step rinsing program:

- 30 seconds HNO3 5%

- 20 seconds HCl 5%

- 10 seconds HNO3 5%

This normally eliminates memory effects for most metals, including Hg. I use He collision cell for most determinations, so I haven't had any issues with Cl- in As determinations

Thanks Jonatan Schlotthauer

In my analysis I construct Hg calibration curves up to 100 ppb and I also use 2% HNO3 according to you answer I can increase rinsing time as:

- 60 seconds HNO3 2%

- 30 seconds HCl 5%

- 30 seconds HNO3 2%

The purpose of the last rinsing step is to remove HCl from the system, which washes off very quickly (even with water), so maybe you don't need to increase the time of that rinsing step.

If you have a separate concentrated standard solution for Hg, I'd use it only in the lower standards (e.g.

Thanks Jonatan Schlotthauer

As suggested by Morin jean-charles .

You can increase the HCl concentration upto 2.5 to 3% and add atleast 100ppb of gold in rinse solution which will eliminate the memory effect for Hg and Sb too.

This has worked me perfectly u can try with this.

Tanks Raghuveer Yaganti

I will try this

Hi,

Read these articles:

JAAS,1998,13,843-54 Transient acid effects in ICP-AES and ICP-MS;

JAAS,1998,13,1249-56 The effect of nitric acid concentration and nebulizer gas flow rates on aerosol properties.

After a significant change in the concentration and type of acid in the solution introduced into the spectrometer, the signals stabilize after a longer time than after the solution with the same concentration of the same acid.

Thanks Zbigniew Jońca

Try this one

https://www.google.pl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwiB-ezgl7zhAhUIqIsKHe41DYEQFjAAegQIARAC&url=https%3A%2F%2Fwww.researchgate.net%2Ffile.PostFileLoader.html%3Fid%3D57f649bab0366d698b5bba93%26assetKey%3DAS%253A414175416340480%25401475758522276&usg=AOvVaw2no1gNmPtsdz6qqPpAz_Xv

Thanks Rafał Gałązka

Gold can be added to help reduce Hg sticking to the tubing of the ICP-MS. See

"Determination of mercury in potable water by ICP-MS using gold as a stabilising agent" by Allibone et al. 1999

Hi Mahmoud Ghuniem,

May I know the conclusion that u have made for the memory effect..