CETAC M-7600 Mercury Analyzer Operator's Manual

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Operator’s Manual Chapter 4: Using the Analyzer QuickTrace M-7600 Automated Mercury Analyzer Figure 4-1 QuickTrace M-7600 Block Diagram. Sample Introduction & Stannous Chloride Reactor Refer to Figure 4-1 to trace the path of liquids through the M-7600 System. An acidified digested aqueous sample from the autosampler is introduced, via peristaltic pump as Hg 2+ dissolved in solution. A reducing agent (10% stannous chloride in 7% HCl), is introduced via a parallel pump channel. The sample and reagent (SnCl 2) streams join at the mixing tee (1), and immediately enter the QuickTrace M-7600 tubing reactor (“Liquid Mix”). Sn 2+ reduces Hg 2+ in solution to Hg 0 while the mixture is en route to the Gas-Liquid separator (GLS). At this stage and prior to the GLS, the analyte is present as a finely dispersed emulsion of liquid (metallic) Hg 0 micro-droplets, in excess SnCl 2 solution. 76
CETAC QuickTrace M-7600 Mercury Analyzer Chapter 4: Using the Analyzer NOTE The CETAC QuickTrace M-7600 mercury analyzer measures inorganic mercury (free Hg 2+ or HgCl 2 , which is subject to efficient stannous chloride reduction in the QuickTrace M-7600 tubing reactor); using inorganic mercury standard solutions for instrument calibration. If insoluble mercury, bound mercury, or organomercurials are present in samples, an appropriate sample dissolution/digestion procedure will have to be employed to convert these other forms to free inorganic Hg 2+ or HgCl 2, prior to analysis with the QuickTrace M-7600. Gas-Liquid Separation The finely dispersed Hg 0 /SnCl 2 emulsion is introduced into the top of the GLS (Gas-Liquid Separator (2)). The Hg 0 /SnCl 2 emulsion flows over the frosted GLS center post in a relatively thin film, covering the entire post from top to bottom. A carrier gas simultaneously enters the bottom of the GLS tangentially (10). The carrier gas (Ar or N 2) swirls around the wetted center post and upwards toward the GLS gas exhaust port (11). Hg 0 droplets in the thin emulsion film quickly evaporate into the gas vortex surrounding the post. The carrier gas stream efficiently sweeps this Hg 0 vapor (along with some evaporated water) upward and out of the GLS gas exhaust (11), and on to the drying (12, 13) and optical section (14, 15) of the QuickTrace M-7600 for an absorbency measurement. The liquid water, containing excess reducing agent, acid, any non-participating “spectator ions,” and reaction by-products, finally drains out the bottom of the GLS (3) and is pumped to waste (4), (channels one & two). NOTE The GLS operates “empty” with no liquid level. The liquid spreads out as a film that wets the center post. At the bottom of the post, the film collects at a single point and is then continuously pumped to waste, so the “liquid level” should not rise in the GLS. Carrier Gas Refer again to Figure 4-1 on page 76 to trace the path of the carrier gas. A clean, dry carrier gas, such as UHP N 2 or Argon, must be supplied to the back of the instrument. The gas passes through fixed restrictors to produce primary flow rates in the range of 30-1000 mL/min at 825 kPa (120 psig). The carrier gas first enters the reference cell (6) to facilitate measurement of the incident radiant power (P 0) at 253.7nm. It exits (7) and passes through the GLS (10) to pick up Hg 0 vapor from the reduced sample. The carrier gas and Hg 0 vapor exit the GLS (11) and enter (12) a Perma Pure ® drying cartridge where water vapor is removed by a Nafion ® membrane (13). For the Perma Pure ® dryer, an auxiliary sweep gas from a restrictor (5A) enters an auxiliary port (17) and selectively removes water vapor from the dryer cartridge at 18. Finally, the dry Hg 0 /carrier gas mixture exits the dryer (13) and enters the sample cell (14B) for measurement of transmitted radiant power (P) at 253.7 nm. 77
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CETAC M-7600 Mercury Analyzer Opera
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Contents 1 Introduction ...........
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M-7600 Mercury Analyzer Operator's
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1 Introduction Overview The CETAC Q
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CETAC QuickTrace M-7600 Mercury Ana
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2 Preparing for Installation Instal
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6 Troubleshooting the Mercury Analy
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8 Glossary A Amperes, electrical cu
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ng Nanogram (10 -9 gram), mass or w
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Index autosampler data cables, 44,
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Manual Part Number 480195 Rev 2 Pri
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CETAC M-7600 Mercury Analyzer Operator's Manual

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