The flame photometric detector (FPD) allows sensitive and selective measurements of volatile sulphur and phosphorus compounds. The detection principle is the formation of excited sulphur (S2*) and excited hydrogen phosphorous oxide species (HPO*) in a reducing flame. A photomultiplier tube measures the characteristic chemiluminescent emission from these species. The optical filter can be changed to allow the photomultiplier to view light of 394 nm for sulphur measurement or 526 nm for phosphorus. The detector response to phosphor is linear, whereas the response to sulphur depends on the square of the concentration.
The flame in the FPD would typically require specialty gases grades of HiQ Synthetic air 5.5 (99.9995% purity and not more than 5 ppm total reported impurity level) and a high purity fuel gas such as HiQ Hydrogen 6.0 to function. Where the use of cylinder hydrogen is restricted, the HiQ® hydrogen generator is safe to operate, due to its small contained volume (< 40 ml). HiQ ® offers a broad range of high purity gas generators for in-house production of Hydrogen, Nitrogen, and Zero Air.