Electrokinetic chromatogram

MEKC instrumentation is not different from the apparatus used for capillary zone electrophoresis (chapter 3.3.2). The only deviation is that the run buffer contains micelles. MEKC is sometimes also referred to as micellar electrokinetic capillary chromatography (MECC). The signals are recorded as an electrokinetic chromatogram with signal intensity versus time. 

Fig. 8.20. Effect of integration time on reconstructed ion chromatograms for the separation of PTH amino acids. Column, 250 x 0.075 mm i.d. packed with 3.5 pm/80 A Zorbax ODS eluents, (A) 2 mmol/1 ammonium acetate, pH 7.0, (B) 2 mmol/1 ammonium acetate, pH 7.0, 90% acetonitrile gradient elution with 30-80% B in 5 min flow rate of mobile phase through inlet reservoir, 100 pl/min applied voltage, 30 kV detection, ESI-MS, (a) 2, (b) 0.25 s/spectrum integration time sheath liquid, 0.2 mmol/1 ammonium acetate, pH 7.0, 90% methanol, 3 pl/min injection, electrokinetic, 2 kV, 2 s sample, PTH-asparagine, PTH-glutamine, PTH-threonine, PTH-glycine, PTH-tyrosine, PTH-alanine (in order of elution). (Reproduced from ref. [82] with permission of Elsevier Sciences B. V.).

Fig. 2 Separation of synthetic, protected tetrapeptide intermediates (9) A-methyl C- and N-protected tetrapeptide (10) non-A-methyl C- and N-protected tetrapeptide. The structures of these compounds is proprietary information and consequently cannot be disclosed. Detection wavelength of 210 nm with a 10-nm bandwidth and a 1-s rise time. Electrochromatography was performed on a 250 mm X 50 iJim i.d. spherisorb ODS-1 packed capillary using an acetonitrile-Tris (50 mmol/L, pH 7.8) buffer 80 20 v/v mobile phase, capillary temperature of 15°C, and an electrokinetic injection of 5 kV/15 s. (a) Synthetic mixture of protected tetrapeptides 9 and 10. Efficiency values of 124,000 and 131,000 plates/m were obtained for analytes 9 and 10, respectively, (b) Chromatogram of synthetically prepared 9, the presence of residual nonmethylated tetrapeptide (10) can be seen, (c) Chromatogram of synthetically prepared 9, spiked with 10% of the nonmethylated tetrapeptide (10). Efficiency values of 83,000 and 101,000 plates/m were obtained for analytes 9 and 10, respectively, (d) Chromatogram of synthetically prepared 9, the presence of residual nonmethylated tetrapeptide (10) can be clearly seen at the 3% level. Additional conditions are indicated in Ref. 38. (From Ref. 38 reproduced with permission of the authors and John Wiley and Sons, Inc.)...

Obtained chromatograms for each soil section, after the electrokinetic experiment with bare RVC anode and cathode are shown in Figure 6, and those for the RVC-TiCb anode with bare RVC cathode are shown in Figure 7. 

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