On-line analysis & monitoring of sulfur compounds in natural gas and gaseous fuels for hazardous area

  • Model: MEDOR® Exp CSA
  • Manufacturer: Chromatotec

The MEDOR® Exp is an industrial gas chromatograph for the analysis and monitoring of sulfur compounds in natural gas and gaseous fuels: H 2S, Mercaptans, Sulfides.

Two versions exist: ppm range or ppb range

Targetted compounds:
  • In standard : THT / H2S / DMS / Mercaptans: MM / EM / IPM / TBM /NPM
  • In option: 2 BM / IBM / NBM

Main applications:

  • Impurities detection in Natural Gas / LPG / Propane / Butane
  • Propellant gas
  • Catalyzer protection

Chromatotec’s MEDOR Exp: Online Sulfur Monitoring for Hazardous Areas

The CHROMATOTEC® MEDOR® Exp offers continuous online analysis of sulfur compounds in natural and biogas feeds, with detection limits as low as 1 ppb. The system analyzes all naturally occurring sulfur compounds like H2S, methyl and ethyl mercaptans, and various odorant blends. It leverages proven GC technology, refined over 35 years, for odorization, quality control, and safety applications across diverse processes.
The MEDOR Exp is an automatic and isothermal gas chromatograph dedicated to analyzing sulfur compounds (H2S, mercaptans, and sulfides) in various matrices. It comes in two versions:
  • MEDOR Exp ppm: Measures sulfur concentrations at ppm levels.
  • MEDOR Exp ppb: Measures sulfur concentrations at ppb levels.

Operating Principle:

  • Designed for hazardous areas with Ex enclosure.
  • Continuously monitors internal temperature and pressure.
  • Automatic valve injects samples using a loop.
  • Detection employs a gas-liquid reaction for high specificity, eliminating interferences.
  • Sulfur-specific detector boasts a lifespan exceeding 10 years.

Key Features:

  • Complies with ASTM D7493-08: Standard Test Method for Online Measurement of Sulfur Compounds in Natural Gas and Gaseous Fuels.
  • Fully automatic and continuous online analyzer housed in a hazardous area enclosure.
  • Integrated industrial computer for on-site data processing.
  • Stores chromatograms with timestamps for traceability.
  • Utilizes VISTACHROM® software, a Chromatotec-developed system enabling:
  • Remote monitoring and injection control.
  • Full traceability with onboard archiving of results.
  • Setting up and controlling QC (Quality Control) and threshold alarms.
  • Exporting data in various formats (MODBUS / MGS1 / 4-20mA / 0-10V).
  • MEDOR® Exp: Online Sulfur Monitoring in Hazardous Zones


Odorization Application : The MEDOR® Exp is designed to monitor all commercially available odorant and mercaptan blends. It facilitates continuous analysis and control of odorant injection systems in natural gas, landfill gas, and biogas facilities. The integrated software automatically transfers all results and data to a host system.
Process Monitoring – Gas Cleaning & Desulfurization : Processes involving sulfur removal, such as landfill or biogas treatment before pipeline injection, necessitate meticulous monitoring and control. With a detection limit as low as 1 ppb H2S, the MEDOR® Exp provides unparalleled security for process monitoring.
The internal multiplexer allows for monitoring both pre- and post-treatment stages using a single analysis system. VistaChrom, the integrated software, features concentration-based alarm thresholds that trigger safety measures in case of process failures.
Natural gas destined for cracking processes can be effortlessly monitored automatically to safeguard catalytic plants. The internal permeation system offers automatic validation of results and data.
Pipeline Quality Control: The MEDOR® Exp is widely used for monitoring sulfur content in natural gas storage and transportation. Unodorized gas can be analyzed for natural sulfur species before and during transport or storage.

Standards & Certifications of MEDOR Exp

Conforms to ASTM D7493-08, ISO 6362/2, DIN 51855
CSA Certified: Class 1 Division 2 Group C&D


  • CSA International Class 1 Div 1, group B, C & D with inert purge
  • External multiple stream selector (up to 16 streams controlled by the analyzer)
  • Calculation modules (Average / Statistics / Odor index…)
  • Electric selection valve to reduce air consumption
  • 24 V DC power supply, can work on battery or solar panel
  • Vortex cooler (air consumption: depending of internal t°)
  • Inert purge with N2 for low consumption of purge gas with X – purge (can work on N2 cylinders)
  • Internal electric heater and/or cooler for temperature regulation of the Exp Cabinet with thermal insulation
Detection limits:
  • MEDOR® Exp ppm:
    • H2S: 0,1 ppm (0,14 mg/m3)
  • MEDOR® Exp ppb:
    • H2S: 5 ppb (7,0 µg/m3) or DMS: 2 ppb (5,1 µg/m3)


Range adjustable, depending on application:
  • 0/10 or 0/100 or 0/1000 ppm or ppb
  • Calculation: total sulfur, total mercaptans…


Relative Standard Deviation:
  • RSD < 3% on concentration over 48H.
  • RSD < 0.5% on retention time over 48H


Cycle Time: H2S 120 s
H2S/TOS/TS 120 s
THT 180s (if only THT)
H2S, MM, EM 300s
H2S, mercaptans, THT 720 s
H2S, mercaptans, THT 900 s with CALIB for validation of each analysis
  • Embedd industrial computer Windows® based with LCD display
  • 32 GB of hardware storage on SSD memory
  • MODBUS communication protocol
  • 4-20mA
  • Ethernet
  • 3G module (optional)


Gas supply for GC operation:
  • Carrier: zero air or N2 (3 bar): 4 ml/min. Use N2 if THT is present
  • CALIB: air or N2 50 ml/min
  • Sample inlet 1 bar: 80 ml/min
  • Pneumatic valve: 90 ml/commutation (0 ml in option)


Gas supply for Exp cabinet:

  • If air used for dilution: 30 l/min in continue
  • If nitrogen used for dilution: 500 l to purge the cabinet and < 0,5 l/min in continue to maintain overpressure


Power supply:

  • Main: 230V / 115V or 50/60 Hz
  • 24 V DC in option


Electrical consumption:

  • 150 VA without options


Dimensions and Weight:

  • Height: 800 mm
  • Width: 600 mm
  • Depth: 300 mm
  • Net weight: 40 kg


To order:


Upon request



TSP Industrial GC 866 Exp


Brochure MEDOR Exp


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