Vertical-orifice capillary

The spherical foam films can be obtained by blowing a bubble from a vertical capillary tube. The principle of formation of such a bubble is illustrated in Fig. 2.22. A vertical capillary tube is placed in a vessel with the surfactant solution so that its upper orifice is close to the solution surface. When a gas (air) with a definite pressure is introduced into the tube over the solution surface a foam film is formed acquiring the shape of a hemisphere. 

The simplest stirrer is a magnetic bar that rotates at the bottom of the cell and causes a vertical flow of the solution. It is used in combination with the hanging, or static, mercury drop electrode. The downward flow of the solution tangentially passes by the drop. Hence, the current density is the highest near the equator of the drop and decreases toward the pole opposite to the capillary, as well as in the capillary shadow, i.e., near the orifice [5]. 

Figure 2.15 Schematic representation of C-API MS, with sample delivery enabled by capillary action. A short tapered silica capillary [length, 1 cm base o.d., 363 pm (or 323 pm without polyimide) tip o.d., 10 pm] was positioned vertically above an electrically isolated aluminum slide, with the outlet end placed orthogonal to the inlet of a metal capillary attached to the orifice of an ion trap mass spectrometer. The distance between the outlet of the silica capillary and the inlet of the metal capillary, attached to the MS orifice, was 1 mm. Before the measurements, the silica capillary was filled with a makeup solution [deionized water/acetonitrile (1 1, v/v)] by means of capillary action. The inlet end of the silica capillary was then dipped into a droplet of a sample (10///) put onto the surface of the aluminum slide. The inset provides an illustration of the hypothetical mechanism of C-API [109], Reproduced with permission from Hsieh, C.-H., Chang, C.-H., Urban, P.L, Chen, Y.-C. (201 i) Capillary Action-supported Contactless Atmospheric Pressure Ionization for the Combined Sampling and Mass Spectrometric Analysis of Biomolecules. Anal. Chem. 83 2866-2869. Copyright (2011) American Chemical Society. See colour plate section for colour figure...

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