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Sampling error in small-bore sheathless capillary electrophoresis/electrospray-ionization mass spectrometry
G A Valaskovic1, F W McLafferty
1Baker Laboratory of Chemistry, Cornell University, Ithaca, NY 14853, USA.
Rapid Communications in Mass Spectrometry : RCM
|January 1, 1996
Summary
Two sources of systematic error in sheathless capillary electrophoresis/electrospray were identified. Hydrodynamic flow from evaporation can underestimate injection size by 50%, while electrospray pull can overestimate sampling volume by 15%.
Area of Science:
- Analytical Chemistry
- Separation Science
Background:
- Sheathless capillary electrophoresis/electrospray interfaces are susceptible to systematic errors.
- Induced hydrodynamic flow can significantly impact quantitative electrokinetic sampling.
Purpose of the Study:
- To characterize two previously unreported sources of systematic error in sheathless capillary electrophoresis/electrospray.
- To quantify the impact of these errors on injection size and sampling volume.
Main Methods:
- Utilized a sheathless interface constructed from 5 microns i.d. capillary columns and 2-5 microns i.d. electrospray tips.
- Investigated hydrodynamic flow induced by solvent evaporation and electrostatic pull from electrospray.
Main Results:
- Evaporation-induced flow can lead to a 50% underestimation of injection size, correctable by immersing the tip in buffer.
- Electrospray pull can reduce migration times, causing up to a 15% overestimation of sampling volume in 5 microns i.d. capillaries.
Conclusions:
- Identified and quantified two key sources of hydrodynamic flow in sheathless capillary electrophoresis/electrospray.
- Developed strategies to mitigate these errors for more accurate quantitative electrokinetic sampling.