(ICP-MS) Food sample preparation&Clean up procedure.

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

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Hello,

I am a beginner using ICP-MS and having some troubles, there are :

1. I have a trouble to control some of metal contaminants. So, what is the most suitable method for clean up glassware (volumetric flask, pipette, and any glassware) and PE vial?

2. In national standard method, we use 5 mL of Nitric Acid concentrated (typically 65%) and 2% hydrogen peroxide and then diluted to 25 mL final volume (Nitric acid concentration = +/- 13%). Is it possible that we change the volume of Nitric Acid to 1 mL + 2 mL hydrogen peroxide + 4 mL water while digestion? So we have +/- below 3% Nitric acid concentration in final.

3. What is the effect of acid concentration in ICP-MS stability/sensitivity measurement?

Thank you for your kind response.
You need to keep the acid concentration of your samples and your calibration standards the same. If you calibrate with 2% acid and samples are 1% or 3% then you will have different results because it affects the ionization of the elements in the plasma.

We use disposable plastic vials for digestion to reduce contamination as much as possible(using a hot block digester). If you need to clean very highly contaminated glassware you can use aquaregia (nitric/hydrochloric) in concentrated form, but you must be very careful because of the fumes. Solvent or soap and water followed by DI water is good for removing light organic contamination, or sulfuric acid or a NOChromix solution for more difficult organic contamination. If you are analyzing for Chromium, Manganese or Potassium I would avoid Chromic Acid, or Potassium Permanganate solutions.
The past is there to guide us into the future, not to dwell in.
Hello Miranti,

To reduce blank levels and contamination you should avoid any glassware when working with ICP-MS, use metalfree PP bottles/tubes instead. You should also use ICP standards, many standards used in AA have quite high levels of other metals you usually don't detect in AA, but you will in ICP-MS.

The acid concentration will affect much more the nebulization efficiency than the ionization, but it will also result in a different instrumental response (signal) between samples and standards. Though, usually the internal standard corrects this effect. Nevertheless, I'd recommend to increase the dilution or reduce the acid amount used, depending on the sample amount you digest.

J
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