In so many publications, ICP-OES (inductively coupled plasma optical emission spectrometry) has been used for the calculation of nanoparticles concentration. Is it the right way? I feel that ICP-OES can do elemental analysis. Expecting your views.
Agnishwar Girigoswami
Both ICP-OES and ICP-MS are highly recommended for multi-elemental analysis. In your case, you are looking for specific elements and your target is to determine their concentrations. Consequentl, you only need to prepare your samples to be compatible with ICP standards then analyze your samples
After nanoparticle digestion, yes you can use icp to determine ion concentration.
Omar Gonzalez-Ortega , yes. After digestion, it will not be nanoparticles. Then, its a wrong method to calculate nanoparticles concentration.
Well I do not think is wrong if you mean mass/volume as concentration. What you cannot determine using icp is number of nps/volume.
Exactly, nps/vol can not be detrmined. This is needed for the concentration determination. Even unreacted metal ions also will contribute in the mass/vol. There is difference between Ag+ and silver nanoparticles or Au3+ and gold nanoparticles etc. Am I clear?
Unreacted ions should be removed before digestion. As I say you can determine mass/volume not nps/volume.
If you have representative standards for your samples, you can then analyze your samples in the same method
Dear Agnishwar Girigoswami
That depends a lot on the samples. If the size- (or rather mass-) distribution of metallic particles is well known and there is no significant contribution from dissolved metals of the same type in solution you can estimate the number concentration from the mass concentration of the element(s) determined in the suspension or digestion of the NPs. I would assume that determining the accurate mass distribution is the major challenge for most NP samples/suspensions, because most methods determine a (hydrodynamic) diameter, which is then used to calculate the volume and mass by assuming a sphere. Differences in NP shapes (and/or composition) will thus lead to additional uncertainty in the mass distribution.
You may check the publications for technical details on how the number concentrations were derived. I agree that many publications do not seem to realize how important it is to supply these data.
As opposed to what has been mentioned previously though, particles < 100 nm diameter will usually not differ substantially in their response in ICPOES (or even in ICPMS) when compared to dissolved ions. Using ions in solutions will thus allow for an adequate calibration for such metal-NP suspensions too.
Bodo Hattendorf there are so many factors to consider as you said. Thank you for your valuable input.
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