| Mobile phase modification is widely used in ion chromatographic to increase the sensitivity and selectivity of ion detection.The technology of mobile phase modification has advantages such as simple operation,good selectivity,suitability for detection of a variety of inorganic and organic ions,and improvement of the analytical performance of the analyte,which has attracted increasing attention.Mobile phase modifiers have been widely applied in the analysis separation because they have stable physical and chemical characters,and can participate in the ion exchange process and improve the dissolve ability of the tested ions.In this study,the imidazole ionic liquids,amino acid ionic liquids,and hydroxypropyl-?-cyclodextrin were used as mobile phase modifiers for ion chromatography to establish a variety of methods for the separation and analysis of anions and cations.The main research content includes:1.Usage of 1-Butyl-3-methylimidazolium hexafluorophosphate as ion chromatography mobile phase modifier for the determination of nitrate and bromide ionsA research of the performance of five imidazolium-based ion liquids(ILs)(the bromides,tetrafluoroborates and hexafluorophosphates of 1-butyl,1-hexyl and 1-octyl-3-methylimidazolium)as additives of the ion exchange chromatographic(IEC)behavior of inorganic anion(NO3-)was studied.The results showed that the IL 1-butyl-3-methyl-imidazolium hexafluorophosphate([C4MIM][PF6])offered the most interesting feature of the separation of the inorganic anion,such as lower retention time and higher peak height.In order to separate anions effectively,the best condition was selected that 0.30 mmol L-1[C4MIM][PF6]in IEC mobile phase(3.2 mmol L-1 Na2CO3 + 1.0 mmol L-1 NaHCO3)for desperation of nitrate with the flow rate of 0.7 mLmin-1 at room temperature.Linear equations of nitrate and bromide were H =-0.02948 + 0.11060C,H =0.00331 + 0.09547C respectively.The limit of detection of nitrate and bromide were 4.4?g L-1 and 0.44?g L-1.In this work,nitrate in the water sample and bromide in flour sample were detected successfully..2.Usage of 1-Butyl-3-methylimidazolium hexafluorophosphate as additives in ion exchange chromatography for the analysis of alkali metal and alkaline earth metal ionsThe behavior of acids(citric acid,nitric acid,oxalic acid,tartaric acid)as a mobile phase and imidazolium ionic liquids(the bromides,tetrafluoroborates and hexafluorophosphates of 1-ethyl,1-butyl,and 1-hexyl-3-methylimidazolium)as additives in ion exchange chromatography for cations(Na+,K+,Mg2+,Ca2+)separation were studied.The results showed that nitric acid and 1-hexyl-3-methyl-imidazolium hexafluorophosphate offered the most interesting features in the separation of cations,such as lower retention time and better resolution.The selected optimal conditions were achieved by adding 0.10 mmol L-1 1-hexyl-3-methyl-imidazolium hexafluorophosphate in 4.0 mmol L-1 HNO3 mobile phase for the separation of four cations with the flow rate of 0.9 mL min-1 at room temperature(25-C).The linear regression equations of Na+,K+,Mg2+,Ca2+ were S = 4,4763c + 0.0209,S = 3.8903c-0.0087,S = 6.3974c-0.0173,and S =7.601 c-0.0339 and the limits of detection of Na',K+,Mg2+' Ca2+ were 0.296,4.98,0.0970,and 1.22 ?gL-1,respectively.In this work,four cations in samples were successfully detected.3.Usage of 1-hexyl-3-methylimidazolium glycine ionic liquid as ion exchange chromatography mobile phase modifier for the determination of Mg2+,Ca2+,Zn2+ and Fe3+In this experiment,four acids were used as the mobile phase of ion exchange chromatography to analyze cations,and nitric acid show the best character.The amino acid ionic liquid(AAIL)was then added in mobile phase to analyze the effect of AAIL on the retention time,peak height and resolution of detected cations.The results indicated that when the imidazole glycine ionic liquid(C6MIM][Gly])was used as the modifier in mobile phase,the retention time was reduced,peak shape was improved,resolution of analytes was optimized and the LOD was reduced effectively.The optimum conditions of this experiment were that adding 0.10 mmol L-1[C6MIM][Gly]in 4.0 mmol L-1 HNO3,the temperature of stationary phase was room temperature and the flow rate of mobile phase was 0.8 mLmin-1.Under these conditions,the peak area was proportional to the concentration of cations,and the linear equations of the magnesium,calcium,zinc,iron ion were S = 0.0126 + 4.4463 C,S =-0.0452 + 3.9224 C,S =-0.0241 + 7.461 C,S =-0.0213 + 6.3154 C,the detection limits were 0.96,3.58,2.12,0.57 ?gL-1.Furthermore,AAIL was successfully applied in determining cations in actual samples,showing its superior prospects in analytical chemistry.4.Usage of Hydroxypropyl-?-cyclodextrin as Ion Chromatography mobile phase modifier for the determination of Amino AcidsIn this experiment,?-cyclodextrin,hydroxypropyl-p-cyclodextrin,and[C2MIM][Gly]were used as mobile phase modifiers to detect four acids,and their effects on chromatographic properties of amino acids were analyzed and compared.The results indicated that hydroxypropyl-?-cyclodextrin can significantly increase the peak area of the analyte.The optimal conditions for this experiment were that 0.50 mmol L-1 hydroxypropyl-?-cyclodextrin was added in mobile phase,and the flow rate of mobile phase was 0.6 mL min-1,the temperature of column was 40?,The linear equations for arginine,alanine,leucine,and aspartic acid in this experiment were H = 0.0319+ 2.4223 c,H =-0.0729 + 3.5534 c,H =-0.0273 + 5.7234 c,H =-0.0269 + 5.3211 c,the detection limits were 0.0026,0.0068,0.0063,and 0.0099 ?gL-1,respectively.Amino acids in radix isatidis granules has been successfully determinated.At the same time,the fluorescence method and mass spectrometry were used to discuss the reaction mechanism and inclusion constants. |
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