I made 3 standard solutions (50-100-250 ppb) by using multi elements standard solutions for ICP(1000mg/l) in order to calibrate and determine silver ion (other metals and heavy metals) in river water and tea leaves, it looks like this method is not applicable since I didn't get any result even after adding silver nitrate in small amount. In fact I need to get the result for trace amount of silver. I mean I can not adding more silver solution
I think Atomic Absorption Spectrometry (AAS) is the better method for trace analysis. One can analyse about 70 metals by using AAS. Only one has to have proper set of hollow cathode lamps.
The concentrations are low for many elements using ICP optical emission but huge by environmental water standards. Do you have access to ICP-MS?
I agree with Mr. PaulMilham, Hence very low concentration work with the ICP-OES, Better to go with ICP-MS.
Dear Dr ghalebi
If the expense of experiment is not matter for you , choosing ICP is better but Atomic absorption spectroscopy is ideal too as you can determining many elements especially trace heavy metals by it.
Thanks to all friends
In response to Sir Paul I should say, I do not have access to ICP-MS, I just can use ICP-OES and low concentration of preparing samples is my problem to analyze. In fact, what is your suggestion to use Standard addition method or do Calibration curve ( at least 3 point) for determine heavy metals by using ICP-OES?, actually this is my main question.
Thank so much
For very low concentration of Ag AAS was not successful. We used ICP-MS and worked fine.
You can select the standards properly, concentrate the samples and analyzed by ICP-AAS.
Hello Mina, with ICP emission, pre-concentration will be essential. You have a choice of techniques, but they all require testing to show how well they apply to the key elements in your samples. That is where spiking will come into play.
If the total salt concentration is small, evaporative concentration, say 10-fold, would be useful, and since you seem interested in 'totals', the concentrated sample could be acidified to match your standards. Matrix matching is important for accuracy.
If the total salt concentration is high, pre-concentration and separation from the matrix by ion exchange, spe, or complexation and extraction into an 'immiscible' organic phase are the common techniques.
Best wishes, Paul.
Thank you very much Mr.Paul, it is full description and useful...I will follow your suggestions...pre-concentration is the important point you mentioned....
Best regard, Mina.
Silver is a rather tricky element. ICP-OES as well as AAS are able to detect the concentration you are looking for. Also when using ICP-MS you will meet the same problems you are describing, even at the much better detection limits of the device. Silver has a high tendency to be adsorbed by the material of vessels, especially in low concentrations (as in your case). Depending on your vessel material and the previous history of use, and the age of the material you will find a rather fast decrease of Ag-conc in the standard solution. You can try it out: using lab glass will give no usable results (calibration curve changes from one hour to the other, and finally disappears); normal PTFE is a sintered material, which develops microfissures by aging. So also PTFE will bias the calibration curve (stability for some hours possible). The only material I found to be usable is PFA. In contrast to PTFE this is an injection molding material with extremely smooth surface. Please use freshly prepared standard dilutions anyway; when storing for several days do some crosscheck between new and old solution. Prepare Ag standards as a stand-alone series; do not add other elements from other standard stock so;utions – they might contain chlorides. (additional question: are you sure that during sample preparation and digestion there were no chlorides (e.g. from soil or plant material) to interfere with silver?).
Good luck
D. Zachmann
Hi
Dear all I use ICP-OES 2100DV Perkin Elmer
for Ag I take -328.068 nm wavelenght, Plasma view Axial
Twister Spray Chamber with Helix 50 ml cyclonic.
Plasma 15 L/min
Aux 0.2 L/min
Neb 0.65 L/min
Power(watts) 1300
Sample flow rate 1.5 ml
Calib curve - 0 ( blank), 10ppb, 50 ppb, 100 ppb
For example I show you results for Ag in QC VKI LL2 5.02 ppb
http://www.eurofins.dk/media/2815/ll2-13-3-0304_dk.pdf
Best regards
Silver can be difficult to measure if you sample contains salt, as silver readily forms AgCl, which can precipitate on the pump and uptake tubing, and never reach the plasma. You didn't mention your acid matrix, but using lots of HCl (10%) may be needed to keep it solublized.
Try the references in the follow-up replies to question posed at this link:
https://listserv.syr.edu/scripts/wa.exe?A2=PLASMACHEM-L;5e4a41df.1508
Information at https://www.inorganicventures.com/periodic-table may also be helpful.
Matthew
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