pH-mediated field-amplified sample stacking of pharmaceutical cations in high-ionic strength samples

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Capillary electrophoresis (CE) of physiological samples often suffers from poor resolution and efficiency due to destacking.
• Previous work focused on catecholamine stacking in artificial solutions, leaving other cationic compounds unexplored.

Purpose of the Study:

• To investigate the efficacy of pH-mediated sample stacking for enhancing the separation and detection of various cationic compounds in CE.
• To extend pH-mediated stacking to a broader range of cationic analytes beyond catecholamines.

Main Methods:

• pH-mediated acid stacking was applied to seven selected cationic compounds (eletriptan, dofetilide, doxazosin, sildenafil, UK-103,320, UK-202,581, and CP-122,288).
• Capillary electrophoretic behavior was compared between background electrolyte (BGE), Ringer's solution, and Ringer's solution with pH-mediated acid stacking.
• Peak heights and efficiencies were analyzed to quantify the stacking effect.

Main Results:

• Acid-stacked samples demonstrated markedly increased peak heights and efficiencies compared to unstacked samples.
• For eletriptan, peak efficiency increased from 72,000 plates (Ringer's) to 246,000 plates with acid stacking.
• pH-mediated acid stacking achieved a 10- to 27-fold sensitivity enhancement for the seven tested cations.

Conclusions:

• pH-mediated acid stacking is an effective technique for improving the sensitivity of capillary electrophoresis for a range of cationic compounds.
• This method overcomes limitations of destacking, offering significant improvements in peak resolution and efficiency.
• The findings support the broader applicability of pH-mediated stacking in the analysis of physiological samples.