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How it Works: Accelerated, Prep-Free Mercury Analysis

The determination of mercury has become a routine test in many analytical laboratories.

by Milestone
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Problem: The determination of mercury has become a routine test in many analytical laboratories. In the past, laboratories have had a choice of using either Cold Vapor Atomic Absorption (CVAA) or ICP-MS to do their mercury analysis. Although both techniques are effective, each requires tedious sample preparation prior to analysis. This is not only costly and labor-intensive but can be challenging due to the element’s volatile nature. In addition, both techniques allow the operator a relatively small dynamic range in which to work.

Solution: The DMA-80 Direct Mercury Analyzer (Milestone Inc.) is a bench-top mercury analyzer that requires no sample preparation steps and delivers results comparable to CVAA and ICP-MS in as little as five minutes per sample. The DMA-80, as referenced in U.S. EPA Method 7473, can be used for the determination of mercury in a variety of matrices including biological tissue, soils, coal and coal by-products and petrochemicals. Other methods which reference direct mercury analysis include U.S. EPA Draft Method 30 B and ASTM Method D6722-01.

The DMA-80 incorporates the following sequence: thermal decomposition, catalytic conversion, amalgamation, and atomic absorption spectrophotometry. A sample is simply weighed and loaded into the built-in autosampler. From here, the sample is placed inside a quartz tube where controlled heating first dries and then thermally decomposes the sample. A continuous flow of oxygen carries the decomposition products through a hot catalyst bed where halogens, nitrogen, and sulfur oxides are trapped. All mercury species are reduced to Hg(0) and then carried along, with reaction gases, to a gold amalgamator where the mercury is selectively trapped. All non-mercury vapors and decomposition products are flushed from the system. The amalgamator is then subsequently heated which releases all mercury vapors to the single beam, fixed wavelength atomic absorption spectrophotometer. There, absorbance is measured at 253.7 nm as a function of mercury content.

The DMA-80 has a dynamic range of 0.0015 ng – 1000 ng, enabling for a wide variety of applications. A forty position, removable autosampler allows for virtually limitless unattended analysis. The analyst can simply load the sample and press ‘START’. Because no sample preparation is required, there are substantial cost and labor savings and no chemical waste is generated.

The DMA-80 provides the laboratory with an easier, more cost-effective mercury analysis instrument. Comparative charts have shown that the DMA-80 saves the laboratory approximately 70 percent of costs when compared to CVAA—with comparable results.

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