Optimised separation of endogenous urinary components using cyclodextrin-modified micellar electrokinetic capillary chromatography

In this study both native and chemically modified cyclodextrins (CDs) were investigated as buffer additives to improve the micellar electrokinetic cap illary chromatography (MEKC) separation of endogenous bioanalytes in human urine. The following CDs were investigated: alpha, beta, gamma-CDs; hydroxy propyl-alpha-CD, hydroxypropyl-beta-CD, methylated beta-CD, sulphated beta- CD, sulphobutyl ether-beta-CD and hydroxypropyl-gamma-CD. The separations w ere compared to MEKC without additives. The best improvement in peak resolu tion and separation of urine components was observed with the sulphated bet a-CD. A four-factor three-level full factorial design study was conducted o n voltage, temperature, pH and sulphated beta-CD molarity. The optimum cond itions were 25 mM sodium tetraborate, pH 9.5, 75 mM sodium dodecyl sulphate (SDS) and 6.25 mM sulphated beta-CD and were able to resolve 70 peaks from a urine pool in 12 min. These optimum conditions have been successfully ap plied to a number of clinical samples.