Detection Of Organic Pollutants By Solid Phase Microextraction Based On Graphite Phase Carbon Nitride Materials

Graphite phase carbon nitride（g-C₃N₄）,a new graphene like material,has attracted much attention in the fields of gas storage,electrocatalysis,photocatalysis and biosensors because of its excellent thermochemical stability,good dispersion and non toxicity.g-C₃N₄ has a largeπconjugation system,which is formed by the covalent bonding of carbon and nitrogen through sp²hybridization.Due to its nitrogen-rich functional groups and electron delocalization property,g-C₃N₄ can effectively enrich trace organic components through complexation,π-πconjugation,hydrogen bonding,electrostatic interaction and hydrophobic interaction.At present,high-temperature calcination is the main preparation method of g-C₃N₄,which has the advantages of simple operation,cheap and easy availability of raw materials.In this paper,g-C₃N₄ materials were prepared by high temperature calcination with urea as carbon precursor.They were used as solid phase microextraction（SPME）coating to realize the sensitive detection of trace components in the sample,combined with gas chromatography（GC）and gas chromatography-mass spectrometry（GC-MS）.The main research contents are as follows:Using urea as carbon precursor,graphite phase carbon nitride with velvet morphology（V-g-C₃N₄）was prepared by high temperature one-step thermal condensation polymerization.The morphology,surface functional groups,crystal structure and specific surface area of the material were characterized by scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）,X-ray diffraction（XRD）and nitrogen adsorption desorption isotherm.Sol-gel technology was used to prepare SPME device with V-g-C₃N₄ as coating material.The extraction parameters and desorption parameters were optimized.Combined with GC,a new method suitable for analysis and detection of polycyclic aromatic hydrocarbons（PAHs）in real water samples was established.The method had a good linear relationship in the concentration range of 0.05-100μg/L,the detection limits（LODs）were 0.005-0.012μg/L,and the spiked recovery in real water samples was 85.94%-103.47%.The coating can be reused for up to 160times.The developed method realized the sensitive detection of trace PAHs in water samples.Oxygen doped graphite phase carbon nitride（O-g-C₃N₄）was prepared by high temperature thermal polycondensation with urea as carbon precursor and hydrogen peroxide as oxygen source.The crystal structure,morphology,element composition,surface functional groups and specific surface area of the material were characterized by XRD,SEM,EDS,FT-IR and nitrogen adsorption desorption isotherm.The material was loose and porous,and its specific surface area was higher than that of the g-C₃N₄ material prepared by directly calcining urea.Then,O-g-C₃N₄ coating was prepared by layer coating with sol-gel as adhesive,and a rapid and effective detection method for analysis of organic phosphate esters（OPEs）in water samples was established combined with GC-MS.The extraction time,extraction temperature,agitation speed,ionic strength,desorption temperature and desorption time were optimized,the method had a good linear relationship in the concentration range of 0.01-100μg/L,the LODs were0.001-0.003μg/L,the spiked recovery of the real water sample were 85.24%-99.73%,and the enrichment factor were 1145-3841.The developed method realized the sensitive analysis of OPEs in real water samples.