Synthesis Of Two Polysiloxane-based Stationary Phase Containing Nitrogen Atom And Their Chromatographic Performance Evalution

The polysiloxane stationary phase has the advantages of high column efficiency,good selectivity,easy coating and film formation,functional modification,etc.It has become one of the most commonly used gas chromatographic(GC)stationary phases.However,the development of polysiloxane stationary phase cannot meet the requirements of increasingly complicated separation and analysis work,and the development of stationary phase with good stability,long-term use and special separation performance is imminent.The carbazole group acts as a three rings fused aromatic hydrocarbon containing an N atom which has special ?-? stacking and dipole-dipole interaction with aromatic compounds,and hydrogen bond interaction with H-bonding analytes.The introduction of polar group as nitro and fluoro into the polysiloxane increases the polarizability of the stationary phase.Nitro-and fluoro-substituted tetraphenyl-phenyl groups are introduced into the long chain of polysiloxane to improve the polarizability of the stationary phase and the introducing of polar groups can increase the dipole-dipole,dipole-induced dipole and hydrogen bonding force between the stationary phase and analytes,the novel stationary phase was suitable for separating the aromatic and polar compounds and H-bonding analytes.The paper contains the following aspects of work:(1)Synthesis of linear hydrogen-containing polysiloxane and polymethylvinylsiloxane.Both polysiloxanes were synthesized through ring-opening polymerization,and the catalysts were acid and base,respectively.The raw materials were D4,D4H/D4Vi.(2)Synthesis of ethyl carbazole grafted polysiloxane.The vinyl carbazole was grafted onto the long chain of hydrogen-containing polysiloxane by hydrosilylation reaction and synthesized the ethyl carbazole grafted polysiloxane with graft ratios of 9%and 18%,respectively(ECP-9 and ECP-18).(3)Synthesis of 2,5-bis(4-nitrophenyl)-3,4-bis(3,5-difluorophenyl)phenyl graft polysiloxane(NDPP).1,2-bis(3,5-difluoromethylphenyl)-1,2-dione was synthesized by benzoin condensation and oxidized reaction with 3,5-difluorobenzaldehyde as the raw material.Subsequently,the product is subjected to aldol condensation with dibenzyl ketone to give 2,5-diphenyl-3,4-bis(3,5-difluorophenyl)cyclopentadienone.In order to introduce nitro group,2,5-bis(4-nitrophenyl)-3,4-bis(3,5-difluorophenyl)cyclopentadienone was obtained by nitration of cyclopentadienone at low temperature using nitric acid as nitrating agent.The product was grafted onto polymethylvinylsiloxane by Diels-Alder reaction,and the NDPP stationary phase witha grafting amount of 12.4%was synthesized.(4)Chromatographic properties of the ECP stationary phase.The operating temperatures of the ECP-9 and ECP-18 phases are 40-340? and 40-360?.The optimum carrier gas flow rate for ECP-9 and ECP-18 was between 8-15 cm/s.For lOm-long and 30m-long ECP-9 columns,the column efficiencies was 3090 plates/m and 3438 plates/m,respectively.For 10 m ECP-18 column,the column efficiency was 3428 plates/m,and the 30 m ECP-18 column has a column efficiency of 3700 plates/m.Both ECP-9 and ECP-18 were medium polarity stationary phases.(5)Chromatographic properties of the NDPP stationary phase.The maximum operating temperature of NDPP stationary phase was 365 ?,and the NDPP was a medium polarity stationary phase.The column efficiency of NDPP using naphthalene as a probe was 3700 plates/m(120 ?).(6)Separation performance evaluation of ECP and NDPP stationary phases.Based on the structural characteristics of the ECP stationary phase and the NDPP stationary phase,the two stationary phases were used for the separation of alcohol,substituted benzene,polycyclic aromatic hydrocarbons and fatty acid ester mixtures.The ECP stationary phase also separates the aromatic aldehyde mixture and uses commercial column DB-17 as a reference to demonstrate the specific selectivity of ECP-18.In separation of aromatic compounds,the difference in separation selectivity between ECP-9 and ECP-18 stationary phase was emphasized.The TFPP was employed for comparing to evaluate the particularity of NDPP stationary phase.Due to the introduction of nitro group,NDPP has obvious advantages in separating nitro-containing aromatic isomers.The xylene isomers can be completely separated on the NDPP stationary phase,especially ethylbenzene/p-xylene/m-xylene with similar boiling points which were co-eluted on DB-17 column.