Theory of Operation

Sulfur Chemiluminescence Detector

The Agilent model 355 Sulfur Chemiluminescence Detector (SCD) is a sulfur-selective detector for gas chromatography. Operation of the SCD is based on the chemiluminescence (light-producing reaction) from the reaction of ozone with sulfur monoxide (SO) produced from combustion of the analyte:

Sulfur compound (analyte) → SO + H2O + other products

SO + O3 → SO2 + O2 + hη (<300–400 nm)

A vacuum pump pulls the combustion products into a reaction cell at low pressure, where excess ozone is added. Light produced from the subsequent reaction is optically filtered and detected with a blue-sensitive photomultiplier tube and the signal is amplified for display or output to a data system. Figure 1 is a pneumatic flow diagram that illustrates how the components of the system are integrated.

The Detector has an enclosed, dedicated (Dual Plasma) Burner designed to enhance production of the SO intermediate. This Dual Plasma Burner mounts in the detector port of the GC. A Dual Plasma Controller provides temperature control and gas-flow regulation to operate the Dual Plasma Burner.

The Agilent model 355 SCD provides high sensitivity (<0.5 pg S/sec), with linear and equimolar response over four orders of magnitude (per Sulfur atom) while maintaining high selectivity over common solvents. The Agilent SCD is compatible with most commercially available gas chromatographs.

Nitrogen Chemiluminescence Detector

Operation of the Agilent model 255 Nitrogen Chemiluminescence Detector is based on the chemiluminescence or light-producing reaction of ozone with nitric oxide formed from combustion. Reacting nitric oxide with ozone results in the formation of electronically excited nitrogen dioxide. The excited nitrogen dioxide emits light, a chemiluminescence reaction, in the red and infrared region of the spectrum. The light emitted is directly proportionally to the amount of nitrogen in the sample,

NO + O3 NO2 NO2 + hη (>800 nm)

The light (hη) emitted by the chemical reaction is optically filtered and detected by a photomultiplier tube. The signal from the photomultiplier tube is amplified for display or output to a data system. Organic compounds containing nitrogen react to form nitric oxide, carbon dioxide, and water.

H2/O2		→
---------------			NO + CO2	+ H2O
R-N + O2	Δ

Operation and Maintenance Manual