Application Of Fiber-optic Sensing Based On Chemometrics In The Adsorption Of Flavonoids And Other Compounds

Compared with gas-phase adsorption,liquid-phase adsorption makes the system relatively complicated due to the addition of solvent.At present,detection of liquid-phase adsorption process is still utilizing the manual sampling.So,for ultra-fast and ultra-slow adsorption,and the adsorption processes of special systems such as small volume,volatile and multi-component cannot be accurately measured.On the basis of the previous work,the in-situ monitoring of small volume and fast adsorption/desorption process is realized by using the fiber-optic sensing system.Therefore,based on a large amount of adsorption spectral data provided by the in-situ detection system,the adsorption kinetics behavior of each component in the multi-component mixed solution and honey were studied in combination with chemometrics.(1)A blade type SPME coating was prepared on glass slides,and2,4-dichlorophenoxyacetic acid(2,4-D)adsorption on solid-phase microextraction(SPME)coating were monitored by in-situ fiber-optic sensing.The effect of reusing of SPME coating,temperature and initial concentration on the adsorption behavior of2,4-D on SPME coating were investigated.The pseudo-second-order kinetic model was found to be the most suitable for describing 2,4-D adsorption on SPME coating.The thermodynamic parameters indicate that 2,4-D adsorption at low concentration by the SPME coating was an exothermic and spontaneous process.Under the same conditions,molecularly imprinted polymers(MIPs)coating has higher adsorption capacity and faster adsorption rate than non-imprinted polymers(NIPs)SPME coating.MIPs SPME coating has a good separation and enrichment factor for 2,4-D in complex matrix.(2)The six channels fiber-optic sensing system overcomes the shortcomings of traditional manual sampling and decrease the measurement error owing to the fast desorption rate.The desorption process of rutin on 14 kinds of macroporous adsorption resins(MARs)was monitored in-situ.The experimental data was investingated by the four models.The pseudo-second-order model was confirmed to be more suitable for describing the desorption behavior of rutin on MARs,and the desorption was mainly divided into three consecutive steps.The effect of temperature on desorption rate was investigated.The MARs were selected according to relevant parameters such as adsorption capacity,desorption capacity,adsorption rate and desorption rate.AB-8,LTX-052 and HPD300 resins were effective in the separation and purification of rutin.(3)UV-vis spectrophotometric method was combined with chemometrics algorithms establish simultaneous determination of liquid-phase adsorption kinetics of multi-component.Partial least squares(PLS),stepwise regression and multi-way partial least squares(N-PLS)models were established by using the original spectrum and processed spectrum pretreated by two different methods.The prediction results were validated by high performance liquid chromatography(HPLC).N-PLS model showed the best prediction ability and the prediction relative error was within 9%.This method lays a foundation for in-situ detection of multicomponent liquid-phase adsorption.(4)AB-8 resin and honey samples were studied.The spectrum data were obtained by fiber-optic sensing in-situ from desorption process.PLS,stepwise regression and N-PLS models were established,using HPLC as an external verification method.The desorption kinetics of rutin and quercetin from honey on AB-8 resin was measured in-situ by fiber-optic sensing combined with chemometrics.This method is fast and low cost,and provides a simple and effective method for in-situ detection of multicomponent liquid-phase adsorption/desorption kinetics.