Study On Reagent-Free Ion Chromatography In Beverage Analysis

There are many methods for analysis of cations, anions, preservatives, sweeteners and iodide in berverage or mineral water, such as atom absorption spectrometry, ultraviolet-visible spectrometry, fluorescent spectrometry, enzyme methods, gas chromatography and high pressure liquid chromatography etc. IC technology develops rapidly in recent years, one of its outstanding accomplishment is the "no reagent only water" technology, which mainly consists two parts of the IC equipment-on-line eluent generator and membrane-based electrolytic suppressor device, only water is needed for the determination of ions, it's a green analytical technology. In this thesis, the applications of reagent-free IC and continuous self-regenerator suppressor in routine analysis of ingredients in beverage and mineral water have been studied. The main content and conclusions are as follow:1. On-line eluent generator, Ionpac CS16 cation exchange column and cation suppressor are used to determine seven cations in mineral water, the effect of suppression and CR-CTC for determination is studied, the detection limits for Li⁺, Na⁺, NH₄⁺ K⁺, Mg²⁺ , Ca²⁺ , Sr²⁺ are between 0.2μg/L-1.1μg/L, their regression equation linear coefficients are more than 0.9943, recoveries are between 94.0%-103.1%. it is discovered that suppression current makes little effect on peak shape and separation efficiency of univalent cations, but makes great effect on that of bivalent cation, the suppression current of 40mA can get minimium RSD and the biggest peak response; the experiment shows CR-CTC can decrease background conductivity and baseline drift; furthermore, a primary discussion is made for the mechanism of cation suppression, the relationship formula between cation response and suppression current is inferred, the relation shows suppression current affects peak response directly.2. An analytical method for determination of bromate in drinking water by ion exchange chromatography suppressed conductivity detection has been developed. A high capacity anion exchange column, IonPacAS11HC column was used, high purity KOH solution generated by eluent generator was used as eluent. Samples were pretreated by extraction with water, then purified by C18 columns, Onguard II Ag columns and Onguard II H columns in sequence to remove some organic substance and chloride, clean liquid was injected. The method enjoyed a wide linear range and good precision. The detection limit was 0.2μg/kg. The average recoveries were between 97.8%-104.8%, and the relative standard deviation (RSD %) was2.09%-3.94%. The results showed that the method was simple, accurate and might be good for application.