Analysis Of Aromatic Carboxylic Acids As Well As The Application Of Ionic Liquids In High Performance Liquid Chromatography

An investigation into analysis of aromatic carboxylic acids as well as the application of ionic liquids in high performance liquid chromatography was carried out. The purpose of this research is to establish simple, accurate, fast and less contaminative methods to determine aromatic carboxylic acids and to develop the application of ionic liquids in high performance liquid chromatography.Firstly, an analytical method based on reverse phase high performance liquid chromatography was established for the simultaneous separation and determination of six aromatic carboxylic acids, including benzoic acid, salicylic acid, phthalic acid, p-amino benzoic acid, p-hydroxyl salicylic acid and o-methyl benzoic acid. The separation of the six aromatic carboxylic acids was performed on a ZORBAX ODS column. The detection of the six aromatic carboxylic acids was carried out by ultraviolet (UV) detection. The influences of composition of mobile phase, elution gradient and detection wavelength on the separation and determination of the six aromatic carboxylic acids were investigated. Under the optimum chromatographic conditions, the six aromatic carboxylic acids were successfully separated in 25 min. The detection limits of the tested components were from 0.21 to 0.99 mg/L. The method has been used to determine two kinds of pharmaceutical. Recoveries of spiked components were between 99.7% and 100.1%. and the relative standard deviations were less than 0.6%.Secondly, an analytical method based on reverse phase high performance liquid chromatography was established for the determination of salicylic acid. The chromatographic separation of salicylic acid was performed on a ZORBAX ODS column. The detection of salicylic acid was carried out by ultraviolet (UV) detection. The comparison of three different mobile phases was performed. The effects of detection wavelength, concentrations, pH value and length of alkyl chain on different ionic liquids on the separation and determination of salicylic acid were investigated. Under the optimum chromatographic conditions, the retention time of salicylic acid was about 4.4 min. The detection limit of salicylic acid was 0.059 mg/L. The method has been successfully used to determine the content of salicylic acid in the pharmaceutical of Zujunqing Tinctura. The average recovery of spiked component was 99.9%, and the relative standard deviation was 0.11%.Thirdly, an analytical method based on reverse phase high performance liquid chromatography was established for the separation and determination of the isomers of amino benzoic acid, including o-, m-,p-amino benzoic acid, and the essential feature of the method is that 1-alkyl-3-methylimidazolium salts are used as mobile phase additives. The separation of the o-, m-,p-amino benzoic acid was performed on a ZORBAX ODS column. The detection of the o-, m-,p-amino benzoic acid was carried out by ultraviolet (UV) detection. The effects of the detection wavelength, pH value, length of alkyl chain on different ionic liquids, and the concentrations on the separation and determination of these analytes were performed. Under the optimum chromatographic conditions, the o-, m-,p-amino benzoic acid were successfully separated within 4 min. The detection limits of the o-, m-,p-amino benzoic acid were from 0.045 to 0.077 mg/L. The method has been successfully used to determine the content of p-amino benzoic acid in the pharmaceutical of Bromine mitag Procaine Injection. Recoveries of spiked components were between 99.8% and 100%, and the relative standard deviations were less than 0.2 %.Finally, a method was developed for the determination of tetramethyl ammonium ion by reverse phase high performance liquid chromatography with indirect ultraviolet (UV) detection. Chromatographic separation was performed on a ZORBAX ODS reverse phase column and chromatographic detection was carried out by indirect UV detection using ionic liquids+organic solvents (acetonitrile or methanol) as mobile phase. The effects of the ultraviolet detection wavelength and mobile phases on the separation and determination of tetramethyl ammonium ion were investigated. Under the optimum chromatographic conditions, the retention time of tetramethyl ammonium ion was about 5.9 min. The detection limit of tetramethyl ammonium ion was 2.60 mg/L. The method has been applied to the determination of tetramethyl ammonium ion in ionic liquid tetramethyl ammonium bromide. The recovery of tetramethyl ammonium ion after spiking was 99.27%. and the relative standard deviation was 0.24%.