Capillary electrophoresis in determination of inorganic anions in microbial fermentation processes; comparison with high-performance liquid chromatography

Capillary electrophoresis (CE) and isocratic high-performance liquid chromatographic (HPLC) methods were optimized and compared for the analysis of several inorganic anions using ultraviolet (UV) and refractive index (RI) detectors, respectively. The chromatographic methods were then applied to the analysis of samples from fermentation processes aimed at microbial purification of flue gases, in particular, anions originating from sulfur and nitrogen oxides. In the CE method, the concentration of electrolyte had a notable effect on the resolution, migration order, and migration times of the anions. The best resolution was achieved in 10 mM chromate with 0.5 mM tetradecyltrimethyl-ammonium bromide (TTAB) as S2O32- Cl--,Cl- NO2- NO3- SO42-, SO32-, PO43-, and CO32- were separated within 10 min. With the HPLC method (ION-120 anion analysis column), the combination of 3 mM salicylic acid and 5 mM Tris showed the best resolution for nitrate and nitrite. Sulfite and sulfate did not separate from each other under any of the conditions tested while the total time of chromatography was 25 min. The UV detection of CE was about 10 times more sensitive than the RI detection used in HPLC. The reproducibility of quantitative analysis data with HPLC was generally slightly better than with CE. A distinct advantage of CE is that pretreatment of samples is unnecessary.