BTEX OMA-300 Measuring Aromatic Hydrocarbons

The composition of pipeline natural gas varies widely by source but typically reflects a mixture of simple hydrocarbons, some inert gases, and often trace amounts of aromatic hydrocarbons. Benzene, toluene, ethylbenzene, and xylene(s) are common aromatics, collectively known at “BTEX” components, whose concentrations may be measured independently (speciation) or in total. The measurement of these aromatics may be necessary to meet compliance, safety, or tariff limits.

Fortunately, aromatic hydrocarbons have strong absorbance in the ultraviolet range and can be easily measured through spectroscopic methods. The laboratory standard ASTM method D1017-51 uses UV spectroscopy for aromatic hydrocarbon analysis. The OMA-300 system takes the same principle and brings it to the field for continuous, fast-response analysis on site. Using a dispersive UVVis spectrophotometer, the OMA continuously measures absorbance at each integer wavelength in the 200-300 nm range — the spectral region in which common aromatic hydrocarbons have very prominent, distinct absorbance curves. This allows the OMA-300 to easily differentiate the absorbance of each compound from the total sample absorbance.


  • Dispersive UV-Vis absorbance spectrophotometer
  • Ultra-safe fiber optic design with dedicated sample flow cell
  • Wide dynamic range due to photodiode array
  • 316 SS NEMA 4X Enclosure
  • Measurement Cell


  • Measurement cell located independent from power
  • Continuously measures aromatic hydrocarbon concentrations
  • No toxic/corrosive sample fluid in analyzer enclosure
  • No error due to absorbance saturation
  • Solid state device with no moving parts
  • Low Maintenance
  • Additional software upgrades available for additional measured chemicals (up to 4 total)



Measurement Principle Dispersive UV-Vis/SW-NIR absorbance spectrophotometry
Detector nova IITM Spectrophotometer
Data sheet: htt://
Spectral Range 200-800 nm (UV-Vis model) or 400-1100 nm (SW-NIR model)
Light Source Standard: pulsed xenon lamp with average 5 year lifespan (dependent on application)
Fiber Optic Cables Standard: 600 μm core 1.8 meter fiber optic cables (qty = 2)
Data sheet:
Sample Medium Gas or liquid
Sample Introduction Standard: stainless steel 316L flow cell with application-dependent path length
Options in data sheet:
Photometric Accuracy ±0.004 AU at 220 nm
Response Time 1-5 seconds
Sensitivity ±0.1 % full scale
Sample Temperature Standard: -20 to 70 °C (-4 to 158 °F)
Sample Pressure (max) Using standard flow cell: 206 bar (3000 psi)
Analyzer Environment Indoor/Outdoor (no shelter required)
Ambient Temperature Standard: 0 to 35 °C (32 to 95 °F)
Optional: -20 to 55 °C (-4 to 131 °F)
To avoid radiational heating, use of a sunshade is recommended for systems installed in direct sunlight.
Electrical Requirements 85 to 264 VAC 47 to 63 Hz
Power Consumption 45 watts
Outputs/Communication 1x galvanically isolated 4-20mA analog output per measured analyte
2x digital outputs for fault and SCS control
Optional: Modbus TCP/IP; RS-232; RS-485; Fieldbus; Profibus; HART; more
I/O Electronics Voltage/Current Interface Module (i.e. I/O Board)
Data sheet:
Accuracy Custom measurement ranges available; example ranges below. Accuracy specifications represent headspace gas sample analysis validated with span gas.
Benzene (C6H6) 0-50 ppm: ±2 ppm
0-100 ppm: ±1% full scale
0-10,000 ppm: ±1% full scale
Toluene (CH3) 0-50 ppm: ±2 ppm
0-100 ppm: ±1% full scale
0-10,000 ppm: ±1% full scale
Xylene (C8H10) 0-50 ppm: ±2 ppm
0-100 ppm: ±1% full scale
0-10,000 ppm: ±1% full scale