Brooks Rand Instruments

Model MERX-M - Automated Mercury Systems



In use at Brooks Rand Labs since 2006 and introduced commercially in 2007, MERX is the world’s first commercial automated analytical system based on US EPA Method 1630 for methylmercury analysis. Around the world, numerous national environmental agencies and leading universities have quickly embraced MERX as an easy-to-use, robust, and reliable system that delivers high quality data.

  • Ultra-low level – All MERX systems undergo rigorous QC testing to ensure they achieve an instrument detection limit of
  • Wide linear range – quantifiable range of 5000x (0.005 ng/L – 25 ng/L)
  • Reduced carryover contamination – With the patent pending gas-pressurized liquid handling system, the purge gas not only transfers the ethylated sample to the purge vessel, but also continues to flow through the sample vial and transfer line to remove any residual volatile mercury compounds, thus allowing the next sample to be processed immediately without a rinse cycle.
  • Sharper peaks – The patent pending ballistic trap heating releases the ethylated mercury species instantly, resulting in sharper peaks and improved GC separation.
  • Fast – MERX utilizes a multiple trap configuration, such that all three traps are in use simultaneously at different stages in the analytical process, resulting in runs every 6.5 minutes or less.
  • Less maintenance – With the “pump-free” MERX system, there is no pump maintenance or constant requirements for tubing replacement. MERX has only a few replacement parts, which are all easily accessible and designed for longevity. Trap sets average over 4000 runs and most other replacement parts last much longer.

Methylmercury Methodology

Sample Preparation
Prior to analysis, samples are prepared as per normal methylmercury methodology, typically distillation for water (US EPA 1630), extraction for sediment or digestion for tissue.

Vial Loading
Prepared samples are added to 40 mL vials with Teflon® lined septa caps. Samples are buffered to pH 4.9, ethylated with the addition of NaBEt4, topped off with DI water, capped, shaken and loaded into the autosampler.

Software Setup
Sample information is entered into Mercury Guru™ software, settings are selected, and then sample analysis begins. MERX does the rest!

Liquid Handling
As each vial is pierced, the liquid is automatically transferred via gas pressure to a purge vessel where N2 gas volatilizes ethylated Hg species to a Tenax® trap.

Trap Processing
The first trap is dried while another trap collects ethylated Hg species from the next vial. After drying, another vial is purged onto a third trap, while the second is dried, and the first trap, now dry, is ballistically heated to thermally release the Hg species in an argon carrier gas stream.

GC Separation
The released Hg species are separated on a GC column and then thermally reduced to elemental mercury.

CVAFS Detection
Mercury is detected using the Brooks Rand Model III cold vapor atomic fluorescence spectrophotometer (CVAFS) with patented optics for enhanced sensitivity.

Data Processing
Mercury Guru™ software integrates the detector signal and calculates results based on calibration and sample volume information. QC results are automatically flagged based on user defined criteria.

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