Direct Mass Spectrometry Determination And Photocatalytical Degradation Research On Phthalate Esters

Phthalate esters?PAEs?have been widely detected in natural environment as new type environmental pollutants.As a series of synthetic organic matters,PAEs are mainly used as raw materials for cosmetics,plastic plasticizers and construction materials.PAEs are not chemically bonded to the ploymersin the matrix,but by hydrogen bond or van der Waals force.Over time,PAEs can leach from the matrix and enter the surrounding environment,causing environmental pollution and damaging the health of creatures and humans.Therefore,in recent years,the migration,detection and degradation of PAEs in the water environment have attracted extensive attention from researchers.At present,the detection techniques of PAEs in water sample have been fully studied,the detection methodinclude gas chromatography,liquid chromatography,gas chromatography mass spectrometry and liquid chromatography mass spectrometry.But the traditional detection techniques require complex sample pretreatment,consume a large amount of organic solvents,easily cause secondary pollution and slow detection speed,which difficultly satisfied the high-throughput sampleanalysisrequirements.electrosprayextractiveionizationmass spectrometry?EESI-MS?is an emerging atmospheric pressure mass spectrometry technique developed in recent years.EESI-MS can rapidly detect samples under normal pressure condition,without complex sample pretreatment,which provide an effective method for in-stu,on-line detection for samples.Meanwhile,researches shows that photocatalytic degradation is an important degradation techniques of PAEs in water environment,and it can remove PAEs efficiently,but the research on the intermediate products and mechanisms of photocatalytic process of PAEs are not completed.Based on the above research background,four phthalate esters?DMP,DEP,DBP,DEHP?with the highest detection rate and concentration in environment were selected as the target compounds.In this study EESI-MS were used to establish a rapid detected method for determination of PAEs in water samples.And using EESI-MS to analyze the intermediate products and mechanisms of the PAEs photocatalytic degradation process based on CuO/TiO₂ catalyst.Firstly,four PAEs were detected by EESI-MS under the positive detection mode and carried qualitative analysis.Some experimental conditions of PAEs determination were investigated systematically,including temperature of ion-transport tube,electrospray voltage,sample solution injection rate and the composition of extractant.Under the optimal conditions,analyzing the linear relationship between PAEs concentration and intensity of secondary characteristic peak.And the quantitative analysis method of PAEs were established.Then,the 5.0 wt%CuO/TiO₂ was prepared following the wet impregnation method,and the photocatalytic degradation experiments of PAEs were carried under ultraviolet light.Investigating the influencing factor of photocatalytic degradation experiments,including the initial pH of the system,catalyst dosage and the light conditions,and the kinetic model of PAEs photocatalytic degradation were explored.Finally,taking DBP as an example,the intermediate products of DBP photocatalytic degradation were determined by EESI-MS.The possible chemical reactions were analyzed according to the intermediate products,and the photocatalytic degradation mechanism of DBP was speculated.The results showed that four PAEs were determined by EESI-MS,and all of them existed in the form of bonding a proton H under the positive detection mode.The collision-induced dissociation?CID?experiments of[M+H]⁺were carried,the results were consistent with literature reports and eliminated the false positive signal.The optimal conditions for detection of PAEs were defined as ion transport capillary temperature 300?,electrospray voltage 3.0 kV,sample solution rate of 8?L/min and extractant for the methanol/water/acetic acid?40:40:20,V/V/V?.The intensity of characteristic peak possessed a good linearity with the concentration of PAEs,and the correlation coefficient of R²>0.98,the recoveries were93.84%¹06.57%and the relative standard deviation were 2.42%¹0.04%.Under ultraviolet light,the photocatalytic experiments of PAEs were carried by 5.0 wt%CuO/TiO₂.The optimal experimental conditions for photocatalytic degradation were determined as follows:Under the ultraviolet light,the initial pH of the system was set as 6 and the catalyst dosage was 20 mg and the degradation efficiency are75.7%⁸8.2%.The photocatalytic degradation of four PAEs were in accordance with first-order reaction kinetic model.The intermediates of DBP photocatalytic degradation reaction include butyl phthalate,butyl benzoate,phthalic acid,benzoic acid,etc.The photocatalytic mechanism of DBP is oxidation decomposition reaction by·OH.In this study,the rapid mass spectrometry determination method of PAEs we established has provide a new method reference for rapid qualitative and quantitative analyze the environmental pollutants.Meanwhile,it is of great to deeply understand the photocatalytic degradation process of PAEs.And providing the theoretical basis for the environmental behavior and ecological risk assessment of PAEs in the environment.