Elemental and Matrix Compatibility

Questions around matrix and elemental compatibility are encountered by all of us on a regular basis. This section addresses this question. Only the most popular matrices will be presented here. Consult our Interactive Periodic Table for other matrices and more information on compatibilities. Technique and calculations will be discussed in part 3 of this guide.

Nitric Acid Matrices

Most analysts prefer nitric acid (HNO₃) matrices due to the solubility of the nitrates as well as its oxidizing ability and the relative freedom from chemical and spectral interferences as compared to acids containing Cl, S, F, or P. In addition, HNO₃ is very popular in acid digestion sample preparations.

The elements that are stable/soluble and commonly diluted in aqueous/HNO₃ are shaded in red below:

1. Os should never be mixed with HNO₃ due to the formation of the very volatile OsO₄.
2. Cl is oxidized to molecular Cl₂ which is volatile and adsorbs on plastic.
3. Br and I are oxidized to molecular Br₂ and I₂ which adsorb onto plastic.
4. Dilutions of Hg and Au in HNO₃ below 100 ppm should be stored in borosilicate glass due to Hg⁺² adsorption on plastic.
5. Not soluble above concentrations of 1000 µg/mL.
6. Trace levels of HCl or Cl- will form AgCl, which will photoreduce to Ag⁰.

F denotes that the element can be diluted in HNO₃ if complexed with F^-.

Cl denotes that the element can be diluted in HNO3 if complexed with Cl-.

HF denotes that the element should have excess HF present when diluted with HNO₃.

T denotes that the tartaric acid complex can be diluted in HNO₃.

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