Samples Containing Magnesium

Hydrolytic Stability and Preferred Matrices

• Mg hydrolysis is detectable in water just before precipitation of Mg (OH)₂ at a pH of ~ 9.5. When diluting Mg standards, pre-acidified water is not required.
• Mg(OH)₂ is one of the least soluble Mg compounds. Solubility issues should be of concern for water solutions containing Mg and fluoride, carbonate, phosphate, borate, arsenite, and arsenate. Increased acidity improves solubility of the above salts.
• The fixed alkali and other alkaline earth hydroxides precipitate Mg⁺² as white gelatinous Mg(OH)₂.
• The following table shows the improvements in stability of Mg⁺² with different complexing agents. The pH where precipitation begins is shown for 0.1 M solutions of each complexing agent:

• Mg can be mixed with any of the elements at high concentrations (200 to 2000 µg/mL) with the exception of the fluoride containing elements (Ti, Zr, Hf, Nb, Ta, W, Si, Ge, Sn, Sb, Mo) and arsenic. Moderate to low levels (≤ 100 µg/mL) can be mixed with all of the elements.
• Mg has a relatively simple emission spectrum. A popular Mg emission line is the 280.270 nm line with a DL of ~ 0.00006 µg/mL (axial view) because of it's relative freedom from spectral interference combined with high sensitivity.

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