Purge and trap preconcentration for MC analysis

Pre-concentration of Mercury in Samples for Stable Isotope Analysis by Oxidation, Purge and Trap

The following procedure is used by the U.S. Geological Survey’s Mercury Research Laboratory (MRL) for the pre-concentration of low concentration or mass limited mercury (Hg) samples for analysis by multi-collector ICP-MS (MC-ICP-MS). This method is a modification of the U.S. EPA Method 1631 for measurement of mercury in water. There are two main steps to this method. The first step is mercury oxidation and then reduction, followed immediately by gaseous purge and gold-sand trap capture. The second step is the thermal desorption of the mercury collected onto a gold trap, and recapture into an acidic oxidizing solution. This method is suitable for aqueous digestions of sediment/soils, biological tissues, filter-passing water samples (< 1L), and suspended particulate matter captured on a capsule filter. Additionally, the thermal desorption step can be utilized as a stand alone process for the pre-concentration of Hg from air collected onto gold traps. Quality assurance and control protocols are employed throughout the sample preparation including: laboratory practices to prevent contamination, analysis of certified reference materials, and pre-concentration of a secondary isotope standard (NIST 3133) to ensure pre-concentration accuracy and precision.

Mercury Research Laboratory, 2019