Research On New Co-reactants Of Luminol Chemiluminescence System And Its Analytical Application

Chemiluminescence analysis is an analytical method based on the phenomenon of light emission generated by certain chemical reactions.It has been widely used in life science,drug analysis,clinical testing,environmental testing and other fields because of its high sensitivity,wide linear range,simple equipment and fast analysis speed.The thesis provides an introduction to new progress and technologies in chemiluminescence analysis in the last five years,including chemiluminescent coreactants,new materials for enhanced chemiluminescence,chemiluminescence energy transfer,chemiluminescence imaging analysis,and chemiluminescence with smart devices.In this thesis,the chemiluminescence behaviors of the coreactants like fluorescein,its derivatives and ascorbic acid for luminol reactions have been studied in detail.The flow injection analysis method for the determination of cobalt ion and ascorbic acid has been established,and its feasibility in the actual samples has been studied.Part one.Fluorescein and its derivatives react with luminol to produce chemiluminescence signal in the alkaline solution.The reaction system has the greatest chemiluminescence intensity in carbonate buffer solution.The chemiluminescence intensity increases about 23 times after adding 0.2 ?mol/L cobalt ions to luminol-DBF system,which shows high sensitivity and selectivity for cobalt ions detection.Under optimum conditions,the cobalt ion concentration in the range of 5?1000.0 nmol/L shows a good linear relationship with the chemiluminescence intensity,and the limit of detection is 1.8 nmol/L cobalt ion.The relative standard deviation was 3.2%in the eleven repeated measurements of 0.2 ?mol/L Co2+ solution,indicating an acceptable precision of the method.Such method is simple and inexpensive.It has been applied to the detection of cobalt ions in blue silica gel samples and has gotten good results.The chemiluminescence spectrum of this chemical reaction has two maximum emission wavelengths at 425 nm and 535 nm.The emission peak at 425 nm is the typical emission peak of luminol,and the emission at 535 nm refers to the maximum emission peak of dibromofluorescein.Therefore,a possible reaction mechanism has been proposed.An autoxidation reaction of fluorescein and its derivatives took place in the basic aqueous solution.The generated active oxygen radicals oxidized luminol to form the excited state of 3-aminophthaiic acid ion with Co2+ ions as catalyst,emitting the emission at wavelength 425 um.The formed excited state of 3-aminophthalic acid ion and 1O2 transferred their energy to DBF molecule,forming the excited molecule and emitting the emission at wavelength 535 um.Part two.Ascorbic acid reacts with luminol to generate chemiluminescence in the alkaline solution.As for the presence of cobalt ions the chemiluminescence intensity of the reaction has increased remarkably.According to this phenomenon,the flow injection chemiluminescence assay has been established for the determination of ascorbic acid.This method has a good response to ascorbic acid with a linear range of 1 to 1000.0 ng/mL.The limit of detection is 0.97 ng/mL ascorbic acid.The relative standard deviation was 3.2%in the eleven repeated measurements of 0.5 ?g/mL ascorbic acid solution.Meanwhile,the interference has been investigated for a variety of metal ions,amino acids,proteins,and biological small molecules.They all have not been observed significant effects on the chemiluminescence intensity.Such method is simple,sensitive and fast and has been applied to the detection of ascorbic acid in practical samples.In addition,possible reaction mechanisms have been proposed.In the alkaline media,ascorbic acid is oxidized by dissolved oxygen to dehydroascorbic acid,and luminol reacts with dehydroascorbic acid to form an excited state of the 3-aminophthalic acid ion.The excited state returns to the ground state and emitting the emission at 425 nm.In conclusion,this thesis has demonstrated that fluorescein and its derivatives,ascorbic acid,can act as coreactants for the luminol reaction system.Based on these,the luminol-DBF-Co(II)system and the luminol-ascorbic acid-Co(II)system have been established.These newly-developed systems enable the highly selective and highly sensitive detection of cobalt ions and ascorbic acid.Moreover,possible reaction mechanisms have been proposed.