Application of enriched stable ¹⁹⁶Hg isotope for monitoring the stability of total mercury in water samples

Abstract

A novel tool for the investigation of stability of total mercury in water samples is presented. The study focuses on the application of enriched ¹⁹⁶Hg stable isotopic reagent for the stability studies. Natural abundance of ¹⁹⁶Hg in water samples is only 0.15%. Thus, the use of the ¹⁹⁶Hg isotope spike represents a major advantage, when it can be assumed that all the measured isotope is the same as is accurately added by the analyst, and the change in its mass concentration can be followed simply and reliably. Tests were carried out with industrial waste water and two type of the natural water. Cold vapour (CV) inductively coupled plasma mass spectrometer (ICP-MS) technique was applied for the mercury measurements. Monitoring was continued for approximately 100 days. It is commonly advised that the measurement for total mercury in water samples should be carried out within 14 days. In this study the samples were observed to be stable for more than three months, if they were stored at a temperature of 4–6°C. The results of this stability study were in line with the guidance presented in EPA standard 1631. However, the samples were noticed to be stable for a much longer time than is presented in the standard method ISO 17852.

Keywords:

• total mercury
• stability study
• storage time
• enriched isotope
• water sample

Acknowledgement

Keijo Tervonen and Markku Ilmakunnas are acknowledged for their invaluable work during sampling and the sample preparation stages.

Additional information

Funding

This work has been partly supported by Graduate School ‘Functional materials and technologies’ receiving funding from the European Social Fund under project 1.2.0401.09-0079 at the University of Tartu, Estonia and partly by the registered association ‘Maa- ja vesitekniikan tuki ry’.