Search

Quinoxaline derivatives are well-known N-heterocycles with pharmacological and fluorescence activities. Almost all quinoxaline derivatives with extensive π-conjugation have been introduced as fluorophores which emit blue and green light. For the first time, we designed and synthesized 6-chloro-2,3 di(Pyridine-2yl) quinoxaline (2-CPQ) as a pink fluorophore in acetonitrile medium by simple route at room temperature whitin 30 min. The synthesized quinoxaline was identified using

A simple, rapid and sensitive method was developed using silver nanoparticles (Ag-NPs) amplified flow-based peroxyoxalate chemiluminescence system to detect berberine, an anticancer agent. Berberine could dramatically sensitize the emission from oxidation reaction of bis (2,4,6-tricholorophenyl) oxalate (TCPO) with H 2 O 2 catalyzed by silver nanoparticles(Ag-NPs). Under optimized experimental conditions, CL intensity was found to be proportional to the concentration of berberine in the range from 5 × 10 −9 to 5 × 10 −7 mol L −1 (r > 0.9843, n = 8) was obtained with a detection limit of 8.7 × 10 −10 mol L −1 . Potential interference by common excipients was also studied. The relative standard deviation for 8 repetitive determinations was less than 3.4% and recoveries of 97.7% and 101.6% were obtained. The Ag nanoparticles were synthesized using Oxalis corniculata plant as green route and characterized using field emission scanning electron microscopy, particle size analyzer and UV–vis Spectroscopy. The method was successfully applied to detect berberine in pharmaceutical formulations.

The present study deals with first attempt to introduce safranin O as the fluorophore for peroxyoxalate chemiluminescence system. The reaction of bis-(2,4,6-trichlorophenyl) oxalate (TCPO) with H2O2 catalyzed by silver nanoparticles can transfer energy to safranin O via the formation of dioxetanedione intermediate and emits orange-red light. The relationship between CL intensity and the concentration of TCPO, fluorophore, hydrogen peroxide and nanocatalyst was investigated. The Ag nanoparticles were synthesized by chemical reduction method and characterized using scanning electron microscopy, particle size analyzer and UV-spectroscopy. Moreover, the system was applied successfully to detect a drug, 6-mercaptopurine (6-MP) in pharmaceuticals. Under optimum conditions, a linear working range for 6-MP concentrations from 5.5 × 10(-7) to 5.5 × 10(-5)mol L(-1) (r>0.9831, n=6) was obtained with a detection limit of 1.6 × 10(-7)mol L(-1). The relative standard deviation for 6 repetitive determinations was less than 3.8% and recoveries of 98% and 103% were obtained.

In the present work the chemiluminescence characteristics of a peroxyoxalate system using berberine as a novel fluorophore has been investigated. Berberine can accept energy via the formation of a dioxetane and emits intense yellow light. The characteristics of the chemiluminescence for this system under various concentrations of reagents including bis (trichlorophenyl)oxalate, sodium salicylate (as catalyst), hydrogen peroxide and the fluorophore were also studied. These parameters including the rise and fall rate constants for the chemiluminescence emission, theoretical and experimental maximum intensity, theoretical and experimental time to reach maximum intensity and total light yield emission were evaluated from intensity–time profiles using the pooled intermediate model by a non-linear least-squares curve fitting program, KINFIT.

In the present work, the effect of fsDNA (fish sperm DNA) on kinetic parameters of chemiluminescence (CL) of the luminol–hydrogen peroxide system catalyzed by Mn(III)–Tetrakis (4-sulfonatophenyl)-porphyrin was investigated. These parameters including pseudo first-order rise and fall rate constant for the chemiluminescence burst, maximum level intensity, time to reach maximum intensity, total light yield, and values of the intensity at maximum CL were evaluated by computer fitting of the resulted intensity–time plots. Results reveal that CL parameters are dramatically affected due to interaction of metalloporphyrin with DNA. In order to observe quenching effect of DNA on CL intensity, Stern–Volmer plot with kQ value of 1.18 × 105 M−1 was calculated in the quencher concentration range of 4 × 10−6–8.5 × 10−5 M.

Hypericin (HYP) molecule is a natural photoactive pigment, which plays a role as an effective photoreceptor in some plants of the Hypericum species (the most common of which is Saint John's Wort) and some insect species. The present work deals with the first attempt to the study of peroxyoxalate chemiluminescence (POCL) system in the presense of HYP as a natural fluorophore. Reaction of bis (2,4,6-trichlorophenyl) oxalate(TCPO)-H2O2-imidazole can transfer energy to a HYP via formation of dioxetane through the chemically initiated electron exchange luminescence (CIEEL) mechanism and can emits a very intense red light. The effects of HYP, hydrogen peroxide, TCPO and imidazole concentrations on kinetic chemiluminescence parameters were also studied. These para- meters including rise and fall rate constant for the chemiluminescence burst, theoretical and experimental maximum intensity, theoretical and experimental time to reach maximum intensity and total light yield emission were evaluated by using a pooled intermediate model for a non-linear least-squares curve fitting program, KINFIT. Moreover, quenching effect of two lipophilic natural antioxidant, Quercetin and b-carotene on it system was also investigated. The measurable concentra- tion range of 7 � 10 � 6 M to 7.5 � 10 � 5 M of antioxidants were evaluated from the proper Stern-Volmer plots with satisfactory RSD% and corresponding detection limits of 2.2 � 10 � 6 and 3.7 � 10 � 6 for b-carotene and quercetin respectively.

The present study deals with first attempt to introduce safranin O as the fluorophore for peroxyoxalate chemiluminescence system. The reaction of bis-(2,4,6-trichlorophenyl) oxalate (TCPO) with H2O2 catalyzed by silver nanoparticles can transfer energy to safranin O via the formation of dioxetanedione intermediate and emits orange-red light. The relationship between CL intensity and the concentration of TCPO, fluorophore, hydrogen peroxide and nanocatalyst was investigated. The Ag nanoparticles were synthesized by chemical reduction method and characterized using scanning electron microscopy, particle size analyzer and UV-spectroscopy. Moreover, the system was applied successfully to detect a drug, 6-mercaptopurine (6-MP) in pharmaceuticals. Under optimum conditions, a linear working range for 6-MP concentrations from 5.5 × 10(-7) to 5.5 × 10(-5)mol L(-1) (r0.9831, n=6) was obtained with a detection limit of 1.6 × 10(-7)mol L(-1). The relative standard deviation for 6 repetitive determinations was less than 3.8% and recoveries of 98% and 103% were obtained.

A simple, rapid and sensitive method was developed using ZnO nanoparticle (ZnO-NP) amplified flow-injection chemiluminescence to detect carvedilol, a non-cardioselective β-blocker. It has been found that carvedilol strongly inhibits the chemiluminescence of luminol–H 2 O 2 catalyzed by ZnO-NPs. Under optimum conditions, a linear working range for carvedilol concentrations from 5×10 −8 to 1.0×10 −6 mol L −1 ( r >0.9894, n =8) was obtained with a detection limit of 3.25×10 −9 mol L −1 . The relative standard deviation for 8 repetitive determinations was less than 2.9% and recoveries of 99% and 102% were obtained. ZnO-NPs were synthesized using a green mechanochemical route. Transmission electron microscopy and x-ray diffraction were used to characterize ZnO-NPs. The method was successfully applied to detect carvedilol in pharmaceutical formulations.

Herein, the effect of amino acid Glutathione (GSH) on Peroxyoxalate Chemiluminescence was studied for the first time. Hypericin (HYP) was employed as the efficient fluorophore. The investigated parameters included rise and fall rate constant for the chemiluminescence burst, theoretical and experimental maximum intensity, the time-needed to reach maximum intensity and the total light yield emission which theoretically was evaluated using the pooled intermediate model by a computerized non-linear least-squares curve fitting program (KINFIT). Furthermore, based on observed quenching effect of GSH, the Stern–Volmer plot in quencher concentration range of 2.8 × 10−6 to 3.4 × 10−5 M with KQ value of 1.59 × 104 was calculated. The bimolecular quenching rate constant (Kq) was also estimated about 2.8 × 1012 and M−1 S−1. Moreover the system was applied successfully to determine glutathione in biological samples.

The present work deals with an attempt to study the effect of human and bovine serum albumin on kinetic parameters of chemiluminescence of luminol-hydrogen peroxide system catalyzed by manganese tetrasulfonatophenyl porphyrin (MnTSPP). The investigated parameters involved pseudo-first-order rise and fall rate constant for the chemiluminescence burst, maximum level intensity, time to reach maximum intensity, total light yield, and values of the intensity at maximum CL which were evaluated by nonlinear least square program KINFIT. Because of interaction of metalloporphyrin with proteins, the CL parameters are drastically affected. The systems resulted in Stern-Volmer plots with 𝑘 𝑄 values of 3 . 1 7 × 1 0 5 and 3 . 7 × 1 0 5 M − 1 in the quencher concentration range of 1 . 5 × 1 0 − 6 to 1 . 5 × 1 0 − 5 M for human serum albumin (HSA) and bovine serum albumin (BSA), respectively.