Cold Vapour Atomic Fluorescence Spectroscopy
The method used by the laboratory was developed by the instrument manufacturer Milestone and follows the USEPA Method 7473: Mercury in Solids and Solutions by Thermal Decomposition, Amalgamation and Atomic Absorption Spectrophotometrypart of the SW846 method series. Method 7473 was specifically developed for use of the DMA-80 in RCRA compliance testing.
Milestone DMA-80 Mercury Analyzer
Samples are analyzed for mercury content using cold vapor atomic absorption spectrophotometry at 254 nm. Solid samples are weighed and liquid samples are measured volumetrically by pipetting into boats (quartz or nickel). The boats enter a chamber in the instrument where the sample is first dried and then thermally decomposed in a continuous flow of oxygen. The combustion products are carried off in the oxygen flow and are then further decomposed in a hot catalyst bed. Mercury vapors are trapped on a gold amalgamator tube and are subsequently desorbed for spectrophotometric quantitation.
Schematic of DMA-80 Instrument
Image from Milestone-General.com
Sample Analysis
Quartz sample boats used to load samples
Some advantages of using this type of instrument for mercury analysis:
- NO SAMPLE PREPARATION
The DMA-80 enables the operator to do direct determination of total mercury without the need for acid digestion or other wet chemistry sample treatment prior the analysis; this means no hazardous chemicals to purchase, handle and dispose.
- HIGH PRODUCTIVITY
Typical analysis time is 5 minutes. A dual-tray autosampler allows for unattended analysis of multiple samples.
- EXTREMELY LOW DETECTION LIMIT
Milestone’s Tri-Cell DMA-80 combines an innovative mercury measuring system with a unique optical path spectrophotometer, achieving a detection limit of 0.0015 ng of mercury.
- MATRIX-INDEPENDENT RESULTS
The DMA-80 is matrix-independent and can analyze both solid and aqueous samples with equal efficiency. A single method can be used to process organic and inorganic samples.
- EASE OF USE
All you need to do is weigh your sample, load it onto the built-in auto-sampler and press ‘start’. The DMA-80 is so simple to use that it can also be operated in the field, not only in the analytical laboratory.
- LOW RUNNING COST
The DMA-80 has been shown to save laboratories more than 70% in costs when compared to traditional mercury analysis techniques like CV-AAS.
- EASY MAINTENANCE
All the DMA-80’s components, such as the catalytic furnace, amalgamator and spectrophotometer, are easily accessible for routine maintenance and cleaning.
- US EPA AND ASTM METHODS AVAILABLE
The DMA-80 is fully compliant with US EPA method 7473 (Mercury in solids and solutions by thermal decomposition, amalgamation, and atomic absorption spectrophotometry) and with ASTM method D-6722-01 (Standard test method for total mercury in coal and coal combustion residues by direct combustion analysis).