Advantages and Pitfalls of Capillary Electrophoresis of Pharmaceutical Compounds and Their Enantiomers in Complex Samples: Comparison of Hydrodynamically Opened and Closed Systems

Abstract

Several research disciplines require fast, reliable and highly automated determination of pharmaceutically active compounds and their enantiomers in complex biological matrices. To address some of the challenges of Capillary Electrophoresis (CE), such as low concentration sensitivity and performance degradation linked to the adsorption and interference of matrix components, CE in a hydrodynamically closed system was evaluated using the model compounds Pindolol and Propranolol. Some established validation parameters such as repeatability of injection efficiency, resolution and sensitivity were used to assess its performance, and it was found to be broadly identical to that of hydrodynamically opened systems. While some reduction in separation efficiency was observed, this was mainly due to dispersion caused by injection and it had no impact on the ability to resolve enantiomers of model compounds even when spiked into complex biological matrix such as blood serum. An approximately 18- to 23-fold increase in concentration sensitivity due to the employment of wide bore capillaries was observed. This brings the sensitivity of CE to a level similar to that of liquid chromatography techniques. In addition to this benefit and unlike in hydrodynamically opened systems, suppression of electroosmotic flow, which is essential for hydrodynamically closed systems practically eliminates the matrix effects that are linked to protein adsorption.

Sensitivity enhancement in capillary electrophoresis and their applications for analyses of pharmaceutical and related biochemical substances

“…A wide range of detection techniques (e.g., spectrophotometry, spectrofluorometry, conductivity, MS, etc.) can be hyphenated to CE [14]. Nevertheless, improvement of detection sensitivity is of great interest in CE researches due to the limited sample injection volume (i.e., the tiny i.d.…”

“…Therefore, many ion sources have been developed to achieve this transition. The most commonly used ionization technique for liquid samples is ESI [5–49]. The integrated two‐phase electroextraction (EE), CE, and MS combine rapid sample extraction to enable high‐performance separation and sensitive detection of metabolites (i.e., leucine, isoleucine, adenosine, phenylalanine, and guanosine).…”

“…Other approaches to achieve better detection sensitivity include the use of capillaries with bubble (the extended light path) or Z‐type cells, especially for UV detection. An approximately 18‐ to23‐fold increase in sensitivity due to the employment of wide‐bore capillaries was observed [14]. This was mainly due to a 6.4‐fold increase of the optical path length.…”

Authenticity assessment of dairy products by capillary electrophoresis

“…Due to the short optical path in capillaries with a diameter of 25-75 μm, CZE in its classic configuration is known to have low sensitivity for many purposes [141] and many different solutions have been developed over the years to improve this aspect [142]. The authenticity assessment of dairy products via CZE of milk proteins can be considered as one of the few applications for which the sensitivity of CE "as is" may be adequate.…”

Comparison of 1D a 2D ITP‐MS performance parameters and application possibilities: Ultratrace determination of B vitamins in human urine

“…The use of bare-fused silica separation capillaries with I.D. between 25 and 100 μm [5][6][7], preventing a hydrodynamic flow of the solution due to capillary forces, is typical for the hydrodynamically open separation system. On the other hand, the ends of a separation capillary possessing higher I.D.…”