Multiple Gas Analyzer #1 GC

• TCD, HID and FID-Methanizer detectors
• 10-port gas sampling valve and 1 ml sample loop
• On-column injector
• 6′ Molecular Sieve 13X + 6′ Silica Gel column
• Built-in “whisper quiet” air compressor
• 6-channel PeakSimple data system
• Options/Upgrades: additional gas sampling valve, additional detectors and additional columns

System Overview:

Your SRI Multiple Gas Analyzer #1 (MG#1) GC is pre-plumbed and ready to resolve H₂, O₂, N₂,
Methane, CO, Ethane, CO₂, Ethylene, NOx, Acetylene, Propane, Butanes, Pentanes, and C₆ through C₈. The basic version of the MG#1 has a TCD detector. It is possible to add an HID or an FID detector with an integrated Methanizer.

The MG#1 allows you to obtain complete analyses of the fixed and natural gases listed above with a single injection. The MG#1 achieves this using a 10-port gas sampling valve with a 1 ml sample loop in the heated valve oven, and two columns in the temperature programmable column oven.

Operation Theory:

10-Port Gas Sampling Valve Plumbing Connections

The valve, sample loop, and column combination are plumbed in a specific way to allow the MG#1 to
separate hydrogen, oxygen, nitrogen, methane, ethane, propanes, butanes, pentanes, carbon monoxide, and carbon dioxide with a single injection.

10-Port Gas Sampling Valve in the LOAD Position

A one-milliliter sample loop is
connected to the 10-port gas
sampling valve. When the valve
is in the LOAD position, sample
may be flowed through this loop
until the moment injection occurs (when the valve switches to the INJECT position).

At the beginning of the
chromatographic run, the valve is actuated to the INJECT position, depositing the sample loop contents into the carrier gas stream and directing it to the two analytical columns, which are connected in series through the 10-port valve.

The sample is deposited by the carrier gas stream first into the Silica Gel column, with the column oven holding at 40°C, where the ethane, propanes, butanes, pentanes, and carbon dioxide are retained. The remainder of the sample containing H₂ (or helium, whichever is not being used as a carrier), O₂, N₂, methane, and CO, continues onto the Molecular Sieve column. During a chromatographic run with the sampling valve in the INJECT position, the H₂ or helium, O₂, N₂, and methane components are the first to elute through the columns and into the detector. This is due to the Silica Gel’s long retention of C₂, CO₂, and higher hydrocarbons at 40°C.

The sampling valve is actuated back into the LOAD position immediately following the elution of the CO peak. This reverses the sequence of the columns before the detector and sends the components preparing to elute from the Silica Gel packed column (ethane, propane, etc.) to the detector without passing them through the Molecular Sieve packed column. At the same time, the Silica Gel packed column temperature is ramped to promote the rapid elution of the remaining components.

After the elution of the CO peak, the valve is switched back into the LOAD position, and the C₂, CO₂, and higher hydrocarbons come off the Silica Gel column.

The FID measures the C₁-C₆ hydrocarbons, plus CO and CO₂, which are converted to methane by the Methanizer in the FID jet.

The TCD measures hydrogen (0,1%), oxygen, nitrogen, methane, and other compounds whose concentrations are at least 200-500ppm (Helium as the carrier).

The built-in data system automates the process: the column oven temperature is controlled through a PeakSimple temperature program, and the sampling valve is controlled through a PeakSimple event table.