Mercury Chemical Stability

By Paul Gaines, Ph.D.

The stability of mercury-containing solutions has been a topic of concern for all trace analysts performing Hg determinations. Our in-house stability studies have yielded the following conclusions.

Mercury Stability

1. Hg is stable in glass (only borosilicate glass studied) in 5% nitric acid at room temperature at all concentrations studied ( 0.05 to 1000 µg/mL) for 1 year.
2. Hg is stable in glass (only borosilicate glass studied) in 5% nitric acid at 4°C at 0.05 µg/mL for 14 months.
3. Hg is stable in glass (only borosilicate glass studied) in 5% nitric acid at room temperature at 5 µg/mL for 2 years and 8 months.
4. Hg appears to be stable in 10% v/v HCl in LDPE. A detailed stability study is in progress for 10% HCl Hg containing solutions.
5. Hg is stable in LDPE in a water / 5% absolute nitric acid matrix for at least 5 months.

Mercury Instability

1. Hg is not stable in MEBs containing Sb at the Tartrate.
2. Hg standards at 0.1, 1.0, 5, 10 and 100 µg/mL were studied in LDPE and it was found that Hg is lost. The loss at the 100 µg/mL is relatively small.
3. Hg looses up to 1 µg/mL Hg in LDPE over time. Therefore, Hg standards < 100 µg/mL should be packaged in borosilicate glass with a 5% nitric acid matrix.
4. The most dramatic result of Hg loss:
   In a comparison of 5 µg/mL Hg standards in 5% nitric acid stored at room temperature in glass and LDPE over a period of ~2.5 years, it was found that the glass was stable. The LDPE container lost greater than 99% of the Hg indicating amounts of Hg > 1 µg/mL can be lost in LDPE with time.

Analytical Properties of Mercury

Chemical Compatibility:  Stable in HNO₃. Avoid basic media forming insoluble carbonate. The sulfide, basic carbonate, oxalate, phosphate, arsenite, arsenate, and iodide are insoluble in water.

Stability:  2-100 ppb levels - stable in 10% HNO₃ packaged in borosilicate glass; NOT stable in 1% HNO₃ / LDPE container. 1-100 ppm levels stable in 7% HNO₃ packaged in borosilicate glass. 1000-10,000 ppm solutions are chemically stable for years in 5-10% HNO₃ / LDPE container.

Hg Containing Samples (Preparation & Solution):  Metal (soluble in HNO₃); HgO (soluble in HNO₃); Ores and Organic based (our documentation has more references to the preparation of Hg containing samples than any other element -- because these preparations are prone to error, we recommend you contact us HERE and we'll provide you with the necessary data for your specific sample type).