Injection system for fast capillary electrophoresis based on pressure regulation with flow restrictors

Abstract

A fast automated system for rapid electrophoretic separations in short conventional capillaries employing contactless conductivity detection is presented. The instrument is based on pneumatic pressurization and does not require a conventional pump. The required pressures and flow rates for the different steps of the injection and flushing processes are produced with the help of two flow restrictors. The device is implemented on a microfluidic breadboard with dimensions of ca. 13 × 20 cm and employs miniature valves. Nine inorganic cations, namely NH K , Na , Ca , Mg , Mn , Sr , Li , and Ba , could be separated in a capillary of 10 μm inner diameter and 6 cm effective length within 25 s. Following a reduction of the effective length to 4 cm, still five inorganic cations could be separated in a time span of 12 s. The repeatability of peak areas was better than 3.1 % and limits of detection between 3.5 and 5.5 μM were achieved.

A compact and high-performance setup of capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D)

“…There are several articles on the fundamental principles [5][6][7][8][9][10][11][12][13] of C 4 D and many reviews about the applications [14][15][16][17][18][19][20][21] of CE-C 4 D; Kubáň and Hauser have compiled a series of bi-yearly reviews on the developments of C 4 D dating back to 2009. [22][23][24][25][26][27][28][29] It has been proven that CE-C 4 D is a universal detection method for charged species and a powerful separation technique with high throughput, [30][31][32] short analysis time, [33][34][35] low sample consumption 19,36 and cost-effectiveness. 37-39 C 4 D is basically an electronic circuit, a feature that is beneficial for portable or miniature applications; the micro-CE-C 4 D is a more approachable alternative for routine water quality analysis and on-site analysis.…”

Improving hydrodynamic injection in capillary electrophoresis by using the integral of pressure

“…Another approach is to use an electromechanical pump to either increase the pressure in the sample reservoir (Figure 1B) or to reduce the pressure in the opposite reservoir. In FIA-CE, the injection is achieved by using the same pump that propels the liquids at the inlet of the CE capillary [10][11][12][13][14]. However, in regular CE instruments, the typical approach is to use an air pump to pressurize the sealed head space of the sample vial.…”

Low‐cost automated capillary electrophoresis instrument assembled from commercially available parts

“…Electrokinetic injection would simplify the procedure, but hydrodynamic injections should be employed to avoid a sampling bias. A possible approach to avoid direct manipulation of the capillary is to place its inlet end into a commercially available T‐piece, as described, for example, by Furter [36]. The sample is first transported into this device and then part of the plug is injected hydrodynamically into the capillary.…”

“…The required pressures, tubing diameters and lengths, as well as the timings for the different steps of the procedures, were optimized for the system by calculations based on the Hagen‐Poiseuille law and the hydraulic‐electric circuit analogy. Details on these procedures can be found in our previous publication [36]. Verification of the pressure profiles is possible by placing miniature hydraulic pressure sensors (available from LabSmith) at different positions in the manifold, but is not necessary for routine use.…”