Analysis Of Metal Ions By Ion Chromatography With Indirect Ultraviolet Detection

An investigation into separation and determination of metal ions by ion chromatography with indirect ultraviolet detection was carried out.The purpose of this research is to develop simple and effective analysis methods to determine metal ions.This study mainly consisted of three parts:Firstly,an analytical method was developed for the separation and determination of alkali metal ions and ammonium by ion chromatography with indirect ultraviolet detection.Chromatographic separation of Li⁺,Na⁺,K⁺and NH₄⁺was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid-acid-organic solvent as the mobile phase,in which imidazolium ionic liquids acted as ultraviolet absorption reagent and eluting agent.The effects of imidazolium ionic liquids,acids,organic solvents and column temperature on the separation and determination of alkali metal ions and ammonium were investigated.The retention behaviors of four kinds of ions are discussed,and the mechanism of separation and detection are described.The optimized chromatographic conditions were selected by using 0.5 mmol/L[EMIm][BF₄]-7.0 mmol/L glycolic acid/acetonitrile?91:9,v/v?as mobile phase,detection wavelength of 220 nm.Under these conditions,baseline separation of Li⁺,Na⁺,K⁺and NH₄⁺were achieved within 13 min,and the detection limits were 0.02,0.11,0.30 and 0.06 mg/L,respectively.The relative standard deviations were less than 2.3%.The method was applied in the determination of mineral water and steamwater with spiked recoveries of 95.0%to 105.0%.A new separation and detection method of alkali metal ions and ammonium by ion chromatography with indirect ultraviolet detection method was developed.The application range of ionic liquid was expanded.Secondly,an analytical method was developed for the separation and determination of alkaline-earth metal ions by ion chromatography with indirect ultraviolet detection.Chromatographic separation of Mg²⁺,Ca²⁺and Sr²⁺was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid-acid as the mobile phase,in which imidazolium ionic liquid acted as ultraviolet absorption reagent.The effects of imidazolium ionic liquids,organic solvents and pH of the mobile phase on the separation and determination of alkaline-earth metal ions were investigated and the retention behaviors in ion chromatography were discussed.The optimized chromatographic conditions were selected by using 0.5 mmol/L[AMIm][BF₄]-0.5mmol/L oxalic acid as mobile phase,detection wavelength of 220 nm.Under these conditions,baseline separation of Mg²⁺,Ca²⁺and Sr²⁺were achieved within 14 min,and the detection limits were 0.06,0.12 and 0.23 mg/L,respectively.Relative standard deviations were less 1.9%.The method was applied in the determination of mineral water with spiked recoveries of 98.0%to 100.7%.A new separation and detection method of alkaline-earth metal ions was developed.The method is accurate,practicable and can meet the quantitative analysis requirements of alkaline-earth metal ions.Finally,the influence of different ultraviolet absorption reagents on the determination of transition metal ions by ion chromatography with indirect ultraviolet detection has been studied.Ultraviolet absorption reagents are divided into cationic,anionic and amphiprotic.Chromatographic separation of transition metal ions(Ni²⁺,Co²⁺,Mn²⁺,Cd²⁺and Cu²⁺)was performed on a carboxylic acid base cation exchange column using ultraviolet absorption reagents-acid as the mobile phase.The effects of different ultraviolet absorption reagents on the separation and determination of transition metal ions were investigated.The separation mechanisms are divided into ion exchange mechanism,forming ion pair mechanism,equilibrium disturbance mechanism.The separation mechanism with the cationic ultraviolet absorption reagent is mainly the ion exchange mechanism,the analyte peaks were negative peaks.The separation mechanism with anionic ultraviolet absorption reagent is mainly the mechanism of forming ion pair,the analyte peaks were positive peaks.The separation mechanism with amphiprotic ultraviolet absorption reagent is mainly the mechanism of the equilibrium disturbance,the analyte peaks could be positive or negative.In these three ultraviolet absorption reagents,the cationic ultraviolet absorption reagents?imidazolium ionic liquids and pyridinium ionic liquids?have the best effect for separation and detection of the transition metal ions by ion chromatography with indirect ultraviolet detection.