Study On Environmental Determination Of Carbonyls Pollutants

The carbonyls that exist in either the atmosphere or water body are harmful to human beings.The traditional determination method uses a chemical reaction between carbonyls and2,4-dinitrophenylhydrazine?DNPH?to produce strong UV-absorbing derivatives for sampling carbonyls prior to their separation and determination by HPLC.However,the“bottleneck”problem of excess derivating agent 2,4-DNPH limits the improvement of sensitivity by co-eluting with carbonyl-DNPH derivatives during chromatography separation.In addition,the existence of a large number of 2,4-DNPH shall limit the degree of pre-concentration of the target sample,because the 2,4-DNPH residual will cause the co-precipitation of Cs-DNPH with the reduction of solvent.Due to the poor pre-concentration factor,the low abundant carbonyls are difficult to be determined.To solve the problems,the molecularly imprinted polymers?MIPs?that have specific adsorption to 2,4-DNPH have been prepared with 2,4–dinitroaniline?2,4-DNAN?as dummy template in the present work.Based on the MIPs,the molecularly imprinted solid phase extraction?MISPE?and monolith in-tube solid phase microextraction?IT-SPME?doped with magnetic molecularly imprinted polymers?MMIPs?were made for the rapid detection of Cs in the air and water body respectively.This paper was divided into two parts.In the first section,a method was developed for the selectivily determination of Cs in ambient PM2.5 by coupling MISPE with HPLC.The effects of template molecular,preparation methods,cross-linking agents and solvents on the recognition property of MIPs were investigated.To enrich Cs-DNPH as much as possible,the optimal extraction conditions were investigated.It is found that the MIPs can only specifically recognize the target molecule in the low polarity solutions by comparing the extraction efficiency of toluene,dichloromethane,chloroform,methanol,and acetonitrile.Under the optimized conditions,the MISPE can eliminate the excessive 2,4-DNPH in air PM2.5 samples.The derived sample can be concentrated fully while the sensitivity increased greatly on account of the elimination of background interference.By coupling MISPE and HPLC,the developed method has been used to study the concentration and resource of 14carbonyls of PM 2.5 during the spring in Guangzhou Higher Education Mega Center.Results showed that the total concentration of carbonyls,especially multi-carbon carbonyl,in PM 2.5increased with the level of air pollution.The content of isovaleraldehyde has been observed to rise sharply to account for 21%of total 14 carbonyls in the haze days.And a high positive correlation between isovaleraldehyde and propionaldehyde was found either in normal days or haze days.The results of correlation analysis showed that anthropogenic emissions have contributed to the abnormally high levels of carbonyls in ambient PM 2.5 in haze days.Possessing high concentration in haze weather,and the nearly zero gas-solid ratio,it is possible that isovaleraldehyde can be used as the indicator for haze weather.In the second part,a new method combining magnetism-reinforced molecular imprinting microextraction technique and non-aqueous capillary electrophoresis?NACE?was developed for the aldehyde detection in water body.With 2,4-DNAN as a dummy template,the magnetic molecular imprinting polymers?MMIPs?based monolith in-tube solid-phase microextraction?IT-SPME?column was prepared.The MMIPs-IT-SPME showed high extraction capacity and well selectivity to 2,4-DNPH.The superfluous 2,4-DNPH can be eliminated efficiently from aldehydes-DNPH solution completely.A series of critical parameters affecting the extraction performance have been investigated detailed.The effects of functional monomer as well as the doping amount of MMIPs were investigated.From adsorption/desorption and BET experiments,it is shown that the MMIP-IT-SPME columns possesses the monodispersed mesoporous structure,and the improved hydrophilicity owing to the Fe₃O₄ doping.As a result,the desorption efficiency of aldehyde-DNPH in toluene is higher on MMIP-IT-SPME than non-magnetic MIP-IT-SPME.Results also reveal that the exertion of the magnetic field in desorption steps can favor the release of the aldehyde-DNPH compounds,but not damage the special retention capacity of the SPME column to 2,4DNPH.The extraction efficiency has enhanced from 63.83%,70.31%,62.67%,65.84%to 99.77%,97.37%,89.75%,87.28%respectively for the tested aldehydes including formaldehyde,acetaldehyde,propionaldehyde,butyraldehyde under the 45Gs magnetic field.Furthermore,a NACE method was developed.Borax and SDS were selected as electrolyte and surfactant respectively and the mixture of formamide and methanol?7:3,v/v?was selected as the solvent.The effects of the concentration of Borax and SDS were explored regarding the separation performance.It is found that the analytes can be separated effectively with SDS at 120 mM and Borax at 40mM.By coupling with NACE,the highly hydrophobic effluent can be analyzed directly,and need not be redissolved in the water-soluble organic solvent.The method was applied to the river near Biochemistry building and tap water.Results show that,the tap water meets the standards for drinking water quality?GB5749-2006?,however,the formaldehyde in river is far beyond the standards,it is necessary to strengthen the monitoring for the river.