DR Knapik: Please take a look at the following useful links:

https://www.researchgate.net/post/Is_it_necessary_to_prepare_samples_and_standard_solutions_in_HNO3_matrix_for_the_analysis_with_ICP_AES

https://www.hitachi-hightech.com/global/products/science/tech/ana/icp/descriptions/icp-oes.html

Short answer: Yes, matrix match your standards with your solutions.

Long answer: Yes it is "really hard", even with a uniform sample type. ICP is a great technique to measure many elements in a single sample, but that doesn't make it easy, if anything it should be harder because you are measuring many elements at once.

If you "know I should have matrix matched blanks, standards and samples", then you should. There are countless examples of why you should, and Ijaz Durrani has pointed out a question from 2014 which has a number of links.

Matrix effects are numerous, but can influence

• sample introduction
• nebuliser efficiency
• spray chamber efficiency
• droplet size
• viscosity of sample
• sample flow rate and so on.

That's before the spray particles even hit the plasma.

In the plasma different amounts of nitric acid, dissolved carbon and other solvents can influence

• ionization efficiency,
• create space charge effects
• plasma temperature
• recombination of multielemental species.

If the acid used to dissolve your samples contains a background of dissolved metals from the glass bottle it came in (hint: it does), but you didn't run a blank digestion sample or use the same acid in the standards, you cannot accurately quantify the metal contamination, let alone the metals in your sample.

I do not recall anyone using an ionization buffer in an ICPOES setting. More than likely, you will add more contamination than improve the signal.

Unless you are comparing radial ICPOES to axial ICPOES, the fact that matrix effects are different is really of no consequence, the effects are present and need to be considered. Check the peak settings of the selected wavelengths (shoulders, background in blank etc). Try a different acid mix (2% HNO3 vs 2% HCl) and see how different the background is.

Best of luck