Water for Capillary Electrophoresis
Impact of Water
In CE, water is used to prepare the buffers, blanks, standards, and to rinse the capillary. To enhance the performance of CE systems, it is important to use water that is free of contaminants.
Particles
The presence of particles in the water used to prepare the buffer may plug the capillaries.
Ions
To have reproducible results, the ionic strength of the buffer needs to stay constant from one run to another. The water used to prepare the buffers needs to have consistently low ionic contamination.
Organics
Water that is grossly contaminated with organics could cause spurious peaks to come out of the electropherogram, and/or cause the background to increase which could mean loss in sensitivity.
Experimental Results
Ultrapure water freshly delivered is suitable for CE analyses. Figure 1 is an electropherogram of an aqueous mixture of 12 nucleosides. The water used to prepare the mixture, buffers, wash solution, and the water used for rinsing came from a Merck water purification system delivering high purity water (Simplicity). When CE-grade bottled water is used, an identical chromatogram is obtained (not shown).
Figure 1. Electropherogram of an aqueous mixture of 12 nucleoside standards by CE with UV detection. Capillary: 50 µm (i.d.) × 48 cm (38 cm to detection window); Applied voltage: -15 kV; Detection at 254 nm; Temperature: 25°C; Sample injection: 0.5 psi, 10 s; Running buffer: 25 mM NaH2PO4, 25 mM Na2B4O7, 25 mM CTAB, pH = 9.50; Peak identification: 1 = adenosine, 2 = cytidine, 3 = guanosine, 4 = uridine, 5 = inosine, 6 = xanthosine, 7 = pseudouridine, 8 = N2- methylguanosine, 9 = N1-methyladenosine, 10 = 8-hydroxy-2’-deoxyguanosine, 11 = 5-hydroxymethyl-2’-deoxyuridine, 12 = N2,N2 -dimethylguanosine
More Information
- http://www.shsu.edu/~chm_tgc/sounds/flashfiles/CE.swf
- http://www.shsu.edu/~chm_tgc/primers/pdf/CE.pdf
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