Research On Magnetic Solid Phase Extraction Method Based On Polydopamine

Sample pretreatment is a critical and essential step in almost all analytical procedures,especially for the analysis of samples with complex matrices.Dopamine molecules can easily self-polymerize under weak alkaline conditions,leading to a facile deposition of polydopamine（PDA）coatings on various surfaces.Since 2011,PDA chemistry has become one of the most attractive areas within the materials field,and undergone significant expansion in its applications.Various PDA-derived adsorbents have also been applied to sample preparation.Chapter one:Recent advancements in the use of PDA-derived adsorbents for sample pretreatment were summarized.This review emphasizes the most recent progress in the use of PDA in sorption-based extraction over the period 2012–2017.This review starts with discussions on various composite sorbents fabricated by PDA modification,then summarizes the operating modes of these extraction methods,and classifies them from the perspective of analyte categories;it finally ends with a discussion on some PDA analogs and future perspectives.Chapter two:A selective and accurate high performance liquid chromatography-mass spectrometry（HPLC-MS）method based on magnetic solid-phase extraction（MSPE）and isotope-coded derivatization was developed and validated.The magnetic polydopamine（Fe₃O₄@PDA）were prepared as sorbents for enrichemnt of ten ultraviolet（UV）filters from domestic wastewater samples.The obtained extract and standards were labeled by a pair of isotope-coded derivatization reagents d0-/d3-10-methylacridone-2-sulfonyl chloride（d₀-/d₃-MASC）,respectively.The quantification of UV filters was achieved by calculation of the peak area ratios of d₀-MASC/d₃-MASC labeled derivatives.The isotope-coded derivatization strategy was confirmed to be effective in reducing matrix effect and improving sensitivity.Excellent linearity is established with the correlation coefficients>0.9922.The limits of detection（LODs）were in the range of 0.24-0.51 nmol/L,and the limits of quantitation（LOQs）were in the range of 0.80-1.70 nmol/L.The developed method has been successfully applied to the quantification of UV filters in domestic wastewater samples with recoveries ranging from 97.2%to 103.6%.Chapter three:We have established an isotope labeling protocol for determining parabens in wastewater,based on a pair of isotope-coded derivatization reagents,by high performance liquid chromatography（LC）and electrospray mass spectrometry（ESI-MS）.The pair of reagents used in our work were d₀-MASC（light form）and d₃-MASC（heavy form）.d₀-MASC and d₃-MASC could easily derivatize parabens at 55°C for 7.5 min in the mixture of bicarbonate and acetonitrile（1:1v/v）.It is shown that the derivatization offers 1–2 orders of magnitude signal enhancement over underivatized counterparts.The global isotope internal standard technology was employed for quantification analysis with d3-MASC-paraben as internal standard for corresponding d0-MASC-paraben.In addition,homologous internal standard was simultaneously used to correct derivatization processes.The obtained double internal standard calibration curves for parabens were linear over the range of 1-500 nmol L-1（r>0.997）.The isotope-coded derivatization based quantification method was precise and practical with RSD≤3.6%and accuracy ranged 96.5 to104.7%.The proposed method has also been successfully applied to the quantification of parabens in domestic sewage samples with precisions≤5.2%and recoveries≥87.9%.Five kinds of paraben including methylparaben,ethylparaben,propylparaben,butylparaben,and benzylparaben were detected in the tested samples.The quantitative results indicated that parabens were at nmol/L level or lower,and ethylparaben were the most abundant,followed by methylparaben,propylparaben and butylparaben.It has been demonstrated that the isotope-coded derivatization reagents are useful for accurate quantification of analytes having target functional groups in real samples.Chapter four:A highly sensitive high performance liquid chromatography-fluorescence detection（HPLC-FLD）method for determination of acidic drugs in water samples was established by using MSPE and chemical derivatization.Firstly,the magnetic metal-organic framework material（Fe₃O₄@PDA@MOF）was successfully prepared.The Fe₃O₄@PDA@MOF materials have great magnetocaloricity,superhydrophilicity and high specific surface area.Therefore,it has great potential as MSPE adsorbent.Three kinds of acidic drugs were selected as the target analytes.The optimal extraction efficiency was achieved by optimizing the extraction parameters,including the pH of the sample,the amount of adsorbent,the adsorption and elution time,and the type of eluting solvent.In addition,the 4-Nitro-7-piperazino-2,1,3-benzoxadiazole（NBD-Pz）is used as a derivatization reagent,and it can react easily with acidic drugs with the aid of condensing agents.The obtained derivatives exhibit strong fluorescence atλex/λem=278/445 nm,which greatly improves the sensitivity of the method.