Effect of pH on inhibition and enhancement of luminol-H2O2-Co2+ chemiluminescence by phenolic compounds and amino acids.
The effect of pH on inhibition and enhancement of luminol-H2O2-Co2+ chemiluminescence (CL) by 18 phenolic compounds and 20 amino acids was studied. It was found that most of the tested compounds showed an inhibiting effect at lower pH and an enhancing effect at higher pH. At a midrange pH, for some phenolic compounds with two ortho-position -OH, both an inhibiting and an enhancing peak were simultaneously observed. UV-visible spectra of the tested phenolic compounds at different pH values were studied. The mechanism for CL inhibition and enhancement was proposed. It is likely that the competition of the -OH or the -NH2 group and other reducing groups in the molecules with luminol for O2*- led to the CL inhibition. A reaction of -COO(-) and quinone or ketone formed by phenolic compounds at higher pH via deprotonation with O2*- also resulted in the CL enhancement.
Cui
Hua
H
Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, People's Republic of China. hcui@ustc.edu.cn
Shi
Ming-Juan
MJ
Meng
Rong
R
Zhou
Jian
J
Lai
Chun-Ze
CZ
Lin
Xiang-Qin
XQ
D000596:Amino Acids / Q000737:chemistry* / Q000494:pharmacology; D016227:Benzoquinones / Q000737:chemistry; D002413:Cations, Divalent; D003035:Cobalt / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D062385:Hydroxybenzoates / Q000737:chemistry; D008163:Luminescent Measurements; D008165:Luminol / Q000737:chemistry* / Q000494:pharmacology; D010636:Phenols / Q000737:chemistry* / Q000494:pharmacology; D013053:Spectrophotometry / Q000379:methods
D000596:Amino Acids; D016227:Benzoquinones; D002413:Cations, Divalent; D062385:Hydroxybenzoates; D010636:Phenols; C009091:protocatechuic acid; D003035:Cobalt; C004532:quinone; D008165:Luminol; D006861:Hydrogen Peroxide