|Principles of Operation|
The DMA-80 combines the techniques of thermal decomposition, catalytic conversion, amalgamation, and atomic absorption spectrophotometry. Controlled heating stages are implemented to first dry and then thermally decompose a sample introduced into a quartz tube. A continuous flow of oxygen carries the decomposition products through a catalyst bed where interferences are trapped. All mercury species are reduced to elemental Hg and are then carried along to a gold amalgamator where the mercury is selectively trapped. The system is purged and the amalgamator is subsequently heated which releases all mercury vapors to the single beam, fixed wavelength atomic absorption spectrophotometer. Here, absorbance measured at 253.7 nm is proportional to mercury content in the sample.
Analyzing a Sample using the DMA-80
Calibrating the DMA-80 is simple and can be performed using either liquid mercury standards or a solid Standard Reference Material (SRM). Since the DMA-80 is matrix independent, calibration standards and unknown samples don’t have to be matrix-matched. That means that the operator can analyze solid samples, for example coal and soil, using a liquid-based calibration. Calibrations are typically very stable and many users find they re-calibrate on a weekly, or in some cases, a bi-weekly basis.
Analyzing a sample with the DMA-80 is easy. Unlike other techniques like XRF, which require grinding or pressing prior to analysis, the DMA-80 requires absolutely no wet chemistry or processing - regardless of whether it’s a solid, powder, liquid, or gel. Simply weigh the sample into a quartz or nickel boat, enter the sample weight, and press ‘START’.