Analytical Chemiluminescence/Lophine and pyrogallol

B2. Lophine and pyrogallol
These are the earliest-known chemiluminescence reagents. Lophine (2,4,5-triphenyl-1H-imidazole) exhibits lemon yellow chemiluminescence in solution and is one of the few long-lasting chemiluminescent molecules. It forms dimers that have piezochromic and photochromic properties. It has been proposed as an analytical reagent for trace metal ion detection. Lophine chemiluminescence was discovered by B. Radziszewski in 1877.

Pyrogallol is determined by means of chemiluminescence at 500 nm which accompanies the oxidation by hydrogen peroxide of autoxidized pyrogallol in the presence of chromium(III) and formaldehyde. Using air-segmented continuous flow analysis, the LOD (3s) was 6.0 × 10−9 mol dm−3 and the calibration was linear up to 10−4 mol dm−3. The method has the potential to be extended to other phenols The chemiluminescent oxidation of pyrogallol has been known for more than one hundred years.