[Determination of anions in liquid crystal samples by UV-photolysis-ion chromatography]

A new method for the determination of anions in liquid crystal samples by UV-photolysis-ion chromatography was developed. The sample pretreatment method, the photolytic conditions and the chromatographic parameters were optimized. The results indicate that there have five anions (F-, Cl-, NO2-, Br-, I-) in the liquid crystal sample. By the filtration with the Dionex OnGuard RP and P cartridges, most of the organic compounds in the photolyzed sample solution can be removed. In the process of photolysis, the efficiency can be remarkably enhanced by the adding of H2O2. Iodide in the liquid crystal sample can be accurately determined by adding of 0.1 mmol/L NaOH. In the five anions, fluoride, choloride, nitrite and bromide can get their maximal responses when the photolysis time is 2 h. With the strongest reducibility, iodide only needs 1.5 h to get the highest response. The separation of the five anions was accomplished with Dionex IonPac AS16 column and the determination can be completed in 25 min. The recoveries for the five anions were between 85.1% and 111.5%.