Capillaries dimensions

Numerous materials have been used to fabricate open tubular columns. Most early studies were conducted using stainless steel tubing and later nickel tubing of capillary dimensions [147-149]. These materials had rough inner surfaces (leading to non-uniform stationary phase films), metal and oxide impurities at their surface which were a cause of adsorption, tailing, and/or decomposition of polar solutes and because their walls were thick, thermal Inertia that prevented the use of fast temperature programming. None of these materials are widely used today. 

Because HPLC and HPCE are based on different physico-chemical principles, HPCE may be expected to address areas in which HPLC has shortcomings [884]. One such area is time of separation. In terms of speed of analysis, selectivity, quantitation, methods to control separation mechanism, orthogonality, CE performs better than conventional electrophoresis and varies from HPLC (Table 4.49). CE has very high efficiency compared to HPLC (up to two orders of magnitude) or GC. For typical capillary dimensions 105—106 theoretical plates are common in CE compared to 20 000 for a conventional HPLC column and... 

The melt flow rate of a polymer is the weight of polymer in grams that extrudes from a standard capillary die under a standard load, at a standard temperature, over a ten minute period. The term melt index is used exclusively for polyethylene melt flow rate is the preferred term for all other polymers, We measure melt flow rates using a piece of equipment called a melt indexer . The capillary dimensions, testing temperature, and load are specified for a given polymer by the National Institute for Standards and Testing. 

Fig. 3.172. Non-aqueous capillary electrophoresis with electrochemical detection of a dye mixture containing (a) 1.7 jUg/ml malachite green, (b) 0.70 jug/ml crystal violet, (c) 4.3 /ig/ml rhodamine B, and (d) 9.1 X 10-6 M ferrocene. Experimental conditions capillary dimensions, 95 cm X 75 pm i.d. running electrolyte, acetonitrile containing 1 M HAc and 10 mM NaAc electrokinetic injection, 20 s 5 kV separation voltage 20 kV applied detection potential, 1.55 V. Reprinted with permission from F.-M. Matysik [206].

From an instrument perspective, the simplest hydraulic approach to transport focused zones to the detector is by gravity mobilization.79 In this technique, focused proteins are transported toward the detection point using a difference in the levels of anolyte and catholyte contained in the reservoirs. The force generated by the liquid-height difference can be manipulated to be extremely small compared with pressure or vacuum. Flow velocity can also be modulated by changing the capillary dimensions or, in the case of large-bore capillaries, with internal diameters greater than 50 pm, by the addition of viscous polymers. 

Capillary dimensions length, length to detector, internal diameter, external... 

In Table 4, an overview is presented of the different experimental parameters of the CE analyses that are included in the analytical instructions part of the specific monographs mentioned above. Notice that the first 13 parameters (from capillary dimensions up to system suitability tests ) are those described in the FDA draft guidance for industry described in paragraph II From this overview it can be concluded that most experimental parameters required by the draft guidance are included in the specific monographs, currently published in the Ph.Eur. and USP. In the monograph for erythropoietin concentrated solution the injection parameters are not included. Only the injection mode (pressure or vacuum) is defined. Instead,... 

LW Tetler, PA Cooper, B Powell. Influence of capillary dimensions on the performance of a coaxial capillary electrophoresis-electrospray mass spectrometry interface. J Chromatogr A 700 21-26, 1995. 

An analysis of the PVP transport using open-ended capillary technique (with capillary dimensions 0.92 mm in diameter and 10 mm high) has in fact clearly demonstrated the time dependence of the apparent diffusion coefficient of the [3H]PVP 360 transport (Fig. 6). On the other hand, the transport behaviour of trace quantities... 

This unit describes a method for measuring the viscosity (r ) of Newtonian fluids. For a Newtonian fluid, viscosity is a constant at a given temperature and pressure, as defined in unit hi. i common liquids under ordinary circumstances behave in this way. Examples include pure fluids and solutions. Liquids which have suspended matter of sufficient size and concentration may deviate from Newtonian behavior. Examples of liquids exhibiting non-Newtonian behavior (unit hi. i) include polymer suspensions, emulsions, and fruit juices. Glass capillary viscometers are useful for the measurement of fluids, with the appropriate choice of capillary dimensions, for Newtonian fluids of viscosity up to 10 Pascals (Newtons m/sec 2) or 100 Poise (dynes cm/sec 2). Traditionally, these viscometers have been used in the oil industry. However, they have been adapted for use in the food industry and are commonly used for molecular weight prediction of food polymers in very dilute solutions (Daubert and Foegeding, 1998). There are three common types of capillary viscometers including Ubelohde, Ostwald, and Cannon-Fenske. These viscometers are often referred to as U-tube viscometers because they resemble the letter U (see Fig. HI.3.1). 

With hydrostatic injection mechanisms, injection reproducibility can be better than 1-2% RSD. The volume of sample loaded is a function of the capillary dimensions, the viscosity of the buffer, the applied pressure, and the time, and it can be calculated using... 

Fused silica capillaries are the most popular capillaries and are commercially available with internal diameters ranging from 10 to 200 pun, although the most commonly used capillary dimensions are 25, 50, and 75 /xm I.D. and 350-400 /xm O.D. To minimize distorting refractive index effects and light scattering with on-column optical detection, the ratio of the outer... 

Stationary phase Mobile phase Capillary dimensions Note... 

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