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色谱 1995
On- Column Sample Stacking of Weakly Acidic Compounds in Micellar Electrokinetic Chromatography
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Abstract:
n-column sample stacking is an effective way to increase injection volurne in high performance capillaryclcctrophoresi:separation,and thus is an easy approach to enhance detection sensitivity.It has been extensivcly studied in capillary zone electrophoresis.In micellar electrokinetic chromatography,as we know,onereport by Y.Z. LIU and his colleague in 1994 has described on- column sample stacking for neutralmolectiles.In this paper,we proposed a simple and easy method to stack on-column samples of weakly acidiccornpounds In miccller electrokinetic chromatography. For stacking of weakly acidic compounds,the principleof the method is that pH valuc of 10mmol/L sodium dodecyl sulfate solution used as sample solvent is adjust-cd to less than pKa- 1(here pKa is the lowest one of te:tacidic compounds)by the addition of low concen-trdrtion of buffcr. so.that acidic compounds exist mainly in species of neutral molecules and is resolved in mi-celles. and that as soon as running voltage is applied,micelles carry sample molecules to the boundary be-twL2Cn sample zone and run buffer,and samples are stacked tbere,For the stacking of basic(or cationic)compounds,pH value of:ample solvent(low concentratioii of micelles and low concentration of buffer)is ad-justed to hlgher than pKw- pKb 1(where pKw is thermodynamic constant for water,and pKb is the great-ext one of the tested compounds),so that the compounds exist mainly in molecular species and can bestacked.On- column stacking is simply performed by dissolving samples in 10mmol/L of sodium dodecyl sul-fatc plus 5mmol/L or less of buffer at the required pH value,The proposed stacking technique is demonstrated and proved by micellar electrokinetic chromatography separation of 7 barbiturates.
