Studies On The New Methods For The Determination Of Water Soluble Polymers And Dyes By Absorption, Fluorescence And Resonance Rayleigh Scattering Spectrometry

Spectrophotometric method and Fluorescence method are the effective molecular spectrum analysis methods,while resonance Rayleigh scattering(RRS) and resonance non-linear scattering(RNLS) are new techniques developed in 1990s.Due to their remarkable characteristics of high sensitivity and simple operation,they have attracted much attentions and have been extensively applied to the studies and determination of biological macromolecules,trace metal ions,nonmetal ions,nano- particles and pharmaceutical field.However,they are seldom applied to the studies of water soluble polymers and dyes.Therefore,in this thesis,we took polyvinylpyrrolidone(PVP), sodium polyacrylate(PAS) and triphenylmethane dyes as examples to develop new systems and new methods for the determination of them by absorption,fluorescence, RRS and RNLS methods.We mainly investigated the spectral characteristics,the optimum conditions and the influencing factors.And the reaction mechanisms were also discussed.The main investigated contents are as follows:1.Studies on the interactions of polyvinylpyrrolidone with eosin Y and their analytical applications by absorption,fluorescence and resonance Rayleigh scattering spectra(1) Fading spectrophotometric method for the determination of polyvinylpyrrolidone with eosin YIn weak acid medium,eosin Y(EY) had a strong absorption band in the visible light region,and the maximum absorption wavelength(λ_max) was at 517 nm.There was no light absorption of polyvinylpyrrolidone(PVP) in 250～700nm.When EY reacted with PVP to form a binding product,a fading reaction of EY appeared and the maximum fading wavelength was still located at 517 nm.At the same time,a smaller absorption peak was observed at 545 nm.The fading absorbance(ΔA) was directly proportional to the concentration of PVP in the range of 0.40～3.20μg/mL.The fading reaction had a high sensitivity.The molar absorptivity(e) was 6.4×10⁶ L·mol^-1·cm^-1 and the detection limit for PVP was 0.12μg/mL.The influencing factors for the reaction were studied,and the results showed the good selectivity.Based on above mentioned,a new fading spectrophotometric method for the determination of PVP with EY was developed.It was simple and rapid,and could be applied to the quantitative determination of PVP in beer samples.(2)Fluorescence quenching method for the determination of polyvinyipyrrolidone with eosin YIn pH 1.8～2.8 weak acid medium,polyvinylpyrrolidone(PVP) and eosin Y reacted to form a complex resulting in the fluorescence quenching of eosin Y(EY).The maximum quenching wavelength was at 542 nm.The fluorescence quenching(ΔF) was proportional to the concentration of polyvinylpyrrolidone in a certain range.The linear range,the detection limit and the correlation coefficient for PVP were 0.33～2.0μg/mL,99.6 ng/mL and 0.9994,respectively.The influences of the coexisting substances were tested and the results showed the good selectivity.Therefore,a new method based on fluorescence quenching of eosin Y by PVP for the determination of trace PVP was developed.The method was sensitive,simple and rapid,and it was applied to the determination of trace PVP in the beer with satisfactory results.The reaction mechanisms were also discussed.(3)Resonance Rayleigh scattering method for the determination of polyvinylpyrrolidone using eosin Y as the probeIn pH 2.9～3.4 weak acidic medium,resonance Rayleigh scattering(RRS) intensity of simple polyvinylpyrrolidone(PVP) or eosin Y(EY) was very weak.But when they reacted with each other to form a binding product,the RRS was enhanced greatly and a new RRS spectrum appeared.There were two scattering peaks at 276 nm and 320 nm. When 276 nm was chosen as the measurement wavelength,the linear range was 0.10～1.6μg/mL.The correlation coefficient was 0.9987 and the detection limit for PVP(K-30) was 28.7 ng/mL.In this work,the RRS spectral characteristics of PVP-EY system were studied.The optimum reaction conditions and the influencing factors were investigated.The effects of some foreign substances were tested which showed the good selectivity.A simple,quick,sensitive new RRS method was developed to determine PVP in the beer.In this work,the reaction mechanism and the binding mode of PVP with eosin Y were discussed through the changes of RRS,absorption and fluorescence spectra.2.Studies on the interactions of polyvinylpyrrolidone with sodium polyacrylate and their analytical applications by resonance Rayleigh scattering and resonance non-linear scattering spectra(1)Determination of trace amouts of polyvinylpyrrolidone using sodium polyacrylate as a probeIn 0.003～0.3 mol/L hydrochloric acid medium,the resonance Rayleigh scattering (RRS),the second-order scattering(SOS) and frequency-doubling scattering(FDS) of water-soluble polymer polyvinylpyrrolidone(PVP) or sodium polyacrylate(PAS) were very weak.When excess amouts of PAS and trace amouts of PVP formed the intermolecular compound,the three types of scattering were all greatly enhanced and the corresponding scattering spectra appeared.The maximum wavelength of RRS was located at 333 nm and another lower RRS peak was appeared at 548 nm.The maximum SOS and FDS peakes were located at 510 nm and 330 nm.In addition,there was a smaller FDS peak at 662 nm.At their respective maximum scattering wavelength,the scattering intensities(ΔI) were proportional to the concentration of PVP in the range of 0.4～2.8μg /mL(RRS),0.13～2.4μg/mL(FDS) and 0.23～2.4μg/mL(SOS).Three methods all had high sensitivities.The detection limits of PVP were 19.9 ng/mL(RRS),39.0 ng/mL(FDS) and 69.6 ng/mL(SOS).Three scattering methods could all be applied to the determination of trace PVP. (2)Determination of trace amouts of sodium polyacrylate using polyvinyipyrrolidone as a probeIn 0.0025～0.075 mol/L hydrochloric acid medium,excess amouts of Polyvinylpyrrolidone(PVP) and trace amouts of sodium polyacrylate(PAS) formed a compound,the resonance Rayleigh scattering(RRS),the second-order scattering(SOS) and frequency-doubling scattering(FDS) were all greatly enhanced.The maximum RRS wavelength was located at 332 nm and another lower RRS peak was at 551 nm. The maximum SOS and FDS peakes were at 510 nm and 330 nm,and there was a smaller FDS peak at 660 nm.At their respective maximum scattering wavelengths,the scattering intensities(ΔI) were proportional to the concentration of PAS in the range of 0.04～4.0μg/mL(RRS),0.22～3.2μg/mL(SOS) and 0.09～3.6μg/mL(FDS).Three methods had high sensitivity and the detection limits for PAS were 13.3 ng/mL(RRS), 25.9 ng/mL(FDS) and 92.4 ng/mL(SOS).Three scattering methods could be applied to the determination of trace PAS.3.Resonance Rayleigh scattering method for the determination of trace amounts of sodium polyacrylate using polyethylene glycol as a probeIn 0.025～0.10 mol/L hydrochloric acid solution,certain polyethylene glycols(PEG) with molecular weights bigger than 10000 were able to interact with the polyacrylate sodium(PAS) to form a compound resulting in the remarkable enhancement of resonance Rayleigh scattering(RRS).The maximum scattering wavelength was located at 560 nm and smaller peaks were at 482nm and 334 nm.Therefore,it was feasible to determine PAS using this kind of PEG as a probe by RRS method.The scattering intensity(ΔI) was directly proportional to the concentration of PAS in the range of 0.46～6.0μg/mL.The detection limit for PAS was 139.0 ng/mL.In this work, the RRS spectral characteristics of PAS-PEG system were studied.The optimum reaction conditions including pH,degree of polymerization of PEG and concentration of PEG,reaction time and ionic strength were investigated.The influences of some foreign substances were tested.The results showed that the method had a high sensitivity and a good selectivity.It could be applied to the determination of trace PAS. 4.Resonance Rayleigh scattering method for the determination of some basic triphenyimethane dyes using tungstate as a probeIn pH 4.2～6.0 HAc-NaAc buffer medium,The resonance Rayleigh scatterings(RRS) intensities of some basic triphenylmethane dyes(BTPMD) such as methyl violet(MV), Ethyl Violet(EV),crystal violet(CV),methyl green(MEG),iodine Green(IG), malachite Green(MG),light Green(BG) alone or tungstate alone radical anion solution were very weak.However,when the dyes were reacted with tungstate anion(WO₄^2-) tO form the ion-association complexes,RRS increased remarkably and new RRS spectra appeared.The reaction products of methyl violet,ethyl violet,and crystal violet with WO₄^2- had similar spectral characteristics and there were two strong RRS peaks at 330 nm and 560 nm.And the reaction products of methyl green,iodine green,malachite green,light green with WO₄^2- had similar spectral characteristics and there were three RRS peaks located at about 335 nm,450 nm and 580 nm,respectively. The scattering intensities of seven kinds of reaction products had great differences. Among them,malachite green system had highest sensitivity.The order of the rest systems were light green＞crystal violet＞ethyl violet＞methyl green＞iodine green＞methyl violet.The linear ranges and detection limits for above seven dyes were 0.06～2.78μg/mLand 18.1 ng/mL(MG),0.08～4.83μg/mL and 22.6 ng/mL(BG), 0.10～4.90μg/mL and 31.4 ng/mL(CV),0.14～2.95μg/mL and 40.5 ng/mL(EV), 0.17～3.70μg/mL and 50.2 ng/mL(MeG),0.22～5.70μg/mL and 67.1 ng/mL(IG), 0.25～7.30μg/mL and 76.3 ng/mL(MV).The methods were sensitive,simple and fast. Based on these,a new RRS method for the determination of basic triphenylmethane dyes using tungstate radical as the probe was developed.It was applied for the determination of malachite green residues in the flesh of with satisfactory results.