Structure-luminescence correlations in the oxybarbiturates

Abstract

The ultraviolet absorption spectra, fluorescence and phosphorescence excitation and emission spectra of sixteen barbiturates and certain model compounds have been examined and correlated. The structure of the fluorescent dianion in the 5,5-disubstituted barbiturates was shown. Phosphorescence was observed at a lower wavelength than that of the prompt fluorescence at room temperature for those barbiturates containing a 5-phenyl substituent. The fluorescence derived from the dianionic form of the heterocyclic ring, whereas the phosphorescence derived from the aromatic nucleus. The effects of steric interactions and pH on the phosphorescence of the phenyl substituted barbiturates are discussed. Detection limits at room temperature and at 77 K for the barbiturates in common use have been determined.

An Enolisable Barbiturate with Adjustable Hydrogen‐Bonding Structure for UV/Vis Detection of Nucleic Acid Bases and Related Compounds

“…The acidity of the NH proton is caused by the delocalisation of the charge over the barbituric acid function, which is strengthened by the electron‐withdrawing NO 2 substituent. In the literature, comparable dianionic species and their stabilisation have been discussed in a large number of investigations, with the p K A values found lying between 12.5 (barbituric acid) and 13.5 (5‐ tert ‐butylbarbituric acid) 15b–f…”

Luminescence determination of pharmaceuticals of the tetrahydrocarbazole, carbazole, and 1,4-benzodiazepine class

“…Luminescence analysis is particularly useful in the analysis of drugs in biological fluids where sensitivity and specificity are of paramount importance. The technique has been successfully used in the determination of a number of drug classes, such as the antimalarials (34,35), cannabinols (36), hallucinogens (37), barbiturates (38), antihistamines (39), sulfonamides (40), and vitamins (41). A recent review (42) also shows its utility in Clinical Chemistry; hence the versatility of the technique is well documented.…”

Identification of barbiturates by chemical ionization and mass-analyzed ion kinetic energy spectrometry

“…The final volume was 25 µ . After the addition of 2 mg of finely powdered K2CO3, the solutions were refluxed for 1 h using a microrefluxer (13). Twelve solutions were refluxed at the same time (one blank with Br-Mmc).…”

“…Numerous techniques have been employed for the identification of barbiturates (1-3). Recent reviews (4, 5) and current applications of some of these techniques are reported in the literature: thin-layer chromatography (6)(7)(8)(9), color profile test (10), microphase extraction (11), luminescence (12,13), high speed ion-exchange chromatography (14), nuclear magnetic resonance (15), and high pressure liquid chromatography (16,17). Preeminent among methods of barbiturate analysis has been gas-liquid chromatography (GC).…”