ICP_Operations_Guide_2016

Elemental and Matrix Compatibility M

ulti-Element Standard Blends

1 Nitric Acid Matrices Most analysts prefer nitric acid (HNO 3

) 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, HNO 3 is very popular in acid digestion sample preparations. The elements that are stable/soluble and commonly diluted in aqueous/HNO 3 are shaded in red below: 1. Os should never be mixed with HNO 3 due to the formation of the very volatile OsO 4 . 2. Cl is oxidized to molecular Cl 2 which is volatile and adsorbs on plastic. 3. Br and I are oxidized to molecular Br 2 and I 2 which adsorb onto plastic. 4. Dilutions of Hg and Au in HNO 3 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 Ag 0 . F denotes that the element can be diluted in HNO 3 if complexed with F-. Cl denotes that the element can be diluted in HNO 3 if complexed with Cl-. HF denotes that the element should have excess HF present when diluted with HNO 3 . T denotes that the tartaric acid complex can be diluted in HNO 3 . Hydrochloric Acid Matrices The use of hydrochloric acid (HCl) is the next most popular acid matrix. HCl is volatile and it is corrosive to the instrument and it's electronics therefore, exposure should be kept to a minimum. The elements that can be diluted in HCl are shaded in blue below:

1. Concentrated (35%) HCl will keep up to 100 μg/mL of Ag + in solution as the Ag(Cl) X-(X-1) complex. For more dilute solutions, the HCl can be lowered such that 10% HCl will keep up to 10 μg/mL Ag in solution. NOTE: The Ag(Cl) X-(X-1) complex is photosensitive and will reduce to Ag 0 when exposed to light. HNO 3 solutions of Ag + are not photosensitive.

2. Parts-per-billion (ppb) dilutions of Hg +2 in HCl are more stable to adsorption on the container walls than are dilutions in HNO 3 . F denotes that the element is more stable to hydrolysis if complexed with F-. In the case of Si and Ge the fluoride complex is generally considered a necessity.

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