Cyclone | Long Pathlength Gas Cell

The cyclone™ is a standard long pathlength gas cell accessory designed with Borosilicate glass body and gold mirrors which are protected. They have been optimized using the latest optical modelling tools to give maximum signal-to-noise.

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Configurable long pathlength There are made to a specified pathlength within the ranges described below. Each of the four bodies permits a different range and has a different internal volume.
Adjustable mirror There is adjustable mirror carriage which can be fitted to Cyclone™ cells to enable the user to vary the pathlength throughout the specified range.

Features

Wide pathlength range (1m - 10m)
Vacuum to 15 p.s.i. operation
Ambient temperature operation
Borosilicate glass body
Anodised components
Gold mirrors (protected)
Viton or Kalrez 'O' ring seals
KBr, CaF2 or ZnSe windows
Purgeable transfer optics box
Benchmark series baseplate mounting

Optional Features

Additional mirror carriage assemblies
Vacuum / gas inlet & outlet taps
Pressure gauge
Desiccant storage caps
Purge bellows

Flexible specification long pathlength gas cells | Cyclone™ These cells are available with glass or metal cell bodies and can be set to a range of pathlengths.

Model	C2	C5 or T5	C10 or T10
Pathlength settings (m)	0.5-2.5 in 0.5 m steps	1.0-8.0 in 1.0 m steps	2.1-10.6 in 1.06 m steps
Base pathlength (mm)	125	250	264
Number of passes	4-20	4-32	8-40
Volume (L)	0.19	1.33	2.60

Which pathlength should I choose? The absorbance of a gas depends on the distance travelled by the IR light beam through the gas sample. The relationship between absorbance, A, concentration, C, and pathlength, L, is given by Beer’s Law: A = -log₁₀(I/I₀) = a.C.L Atmospheric concentrations of gases are usually expressed in C.L units of ppm.m – the number of molecules that would be encountered by the infrared beam across a 1.0 m path. A gas at 0.1 ppm atmospheric concentration will absorb as much IR light over a pathlength of 100 m as would the same gas at 1 ppm over 10 meters or at 10 ppm over 1 meter. To achieve optimal results, the pathlength of cell should be chosen to give absorbance values within the spectrometer’s linear range for a given concentration. The following table may be taken as a guide:

Gas name	formula	v (cm^-1)	ppm	absorbance within 1m pathlength
Carbon dioxide	CO₂	2360	100	0.40
Carbon monoxide	CO	2170	100	0.04
Methane	CH₄	3020	100	0.10
C₂ to C₆ n-alkanes		2960	100	0.10
Nitrogen dioxide	NO₂	1630	100	0.15
Nitric oxide	NO	1900	100	0.015
Sulfur dioxide	SO₂	1370	100	0.09
Hydrogen sulfide	H₂S	1300	1000	0.002
Ammonia	NH₃	960	100	0.12
Hydrogen chloride	HCl	2940	100	0.04
Water	H₂O	1650	1000	0.20
Vinyl chloride	CH₂CHCl	950, 900	100	0.06
Acetaldehyde	CH₃CHO	2750	100	0.015
Benzene	C₆H₆	670	10	0.09
Toluene	C₆H₅CH₃	730, 690	100	0.10
Methanol	CH₃OH	1040	100	0.10
Ethanol	CH₃CH₂OH	1050	100	0.05
Carbonyl sulfide	COS	2070	100	0.40
Nitrous oxide	N₂O	2235	100	0.15
Sulfur hexafluoride	SF₆	950	10	0.40