Catecholamines Surface Enhanced Raman Spectroscopy

Surface-enhanced Raman scattering (SERS) effect is a special surface-enhancedoptical phenomena observed on some metallic nanostructure. The SERS techniquehas become an ultrasensitive and nondestructive analytical tool because of its highselectivity and sensitivity. At the moment, the SERS technique has been appliedcomprehensively in the research of surface science，biology,analytical scienceandmaterial science.Oxidation and decomposition are inherent problems frequentlyencountered in the SERS measurements, especially for organic orbiomolecules.Several physical ways like vacuum, inert atmosphere, low temperatureor low laser power,have been reported in the literature for reducing theseinterference. However, these approaches could not be employed conveniently forroutine analysis of SERSmeasurements. Apparently, development of new chemicalmethods with more operable performance should be significant for the effectiveelimination of oxidation and decomposition of analytes in the measurements.Dopamine and related catecholamines such as epinephrine and norepinephrineare important neurotransmitters in the nervous systems of invertebrates andvertebrates. Catecholamines is closely related to peoples health, and they are notonly directly take part in behavioral activities and participate in the regulation ofblood pressure, heart rate, breathing and sleep autonomic function, but also with anumber of functional disorders such as schizophrenic psychosis and depression. Theycan be explored in blood and urine. Therefore, it is an significant work to explore aneffectiveand accurate way for quantitative analysis with the catecholamines.This thesis chooses dopamine, epinephrine and norepinephrine as researchobjects. We prepared silver nanoparticles as SERS substrate. By forming complexes ofiron ions and catecholamines under appropriate conditions, we have establishedaneffectiveand convenient way toimprove the quality of SERS spectral informationofatecholamines.In addition, having considering the fact thatcatecholamines areoften coexistence with ascorbic acidin biological fluids,we also carried out aqualitative and quantitative analysis of dopamine, epinephrine and norepinephrine under the presence of ascorbic acid. The magnitude of the lowest concentration is~10-8mol/Land a good linear relationship can be obtained.This paper mainly covers the following aspects:(1) The impact of pH on theSERS spectra ofdopamine, epinephrine andnorepinephrine wasdiscussed,and an effective approach to avoid the decompositionof the catecholamines was put forwardby adjusting the pH of the solutiontoeliminatecarbonization interference.(2) By the additionof iron ions to form complexes with catecholamines, and theadjustmentof the pH of solution,we exploredand optimizedthe experimentalconditions for the qualitative and quantitative analysis ofcatecholamine by theRaman spectroscopic technique.(3) For the reason that catecholamines often coexist with ascorbic acid inbiological fluids, we also exploredand optimizedthe experimental conditions for theanalysis ofcatecholaminein the presence of ascorbic acid.Especially, the quantitativeanalysis dopamine in the presence of ascorbic acid was carried out by the Ramanspectroscopic technique.