Length mobility

Fig. 15. Electrochromatograms obtained in columns coated with sol-gel composites (A) TEOS and (B) C8-TEOS/TEOS. (Reprinted with permission from [80]. Copyright 1999 American Chemical Society). Separation conditions fused silica capillary, 12 pm i.d., 60 cm total length, 40 cm active length, mobile phase 60/40 methanol/1 mmol/1 phosphate buffer, voltage 30 kV, electrokinetic injection 5 s at 6 kV, UV detection at 214 nm. Peaks toluene (1), naphthalene (2), and biphenyl (3)...

The band profiles are obtained as the change of concentration against time at the column outlet. To better understand the effect of mobile phase dispersion, column length, mobile phase velocity, and other parameters, we introduce some normalization. We can rewrite Equation 10.8, using... 

Fig. 4.17. Separation of a test mixture in a packed bed of 0.5 pm (C8) particles. Column packed bed of 15 cm in a capillary of 35 cm total length mobile phase 80 20 acetonitrile-50 mM Tris buffer at pH 8 separation voltage of 30 kV injection, 3 s at 300 V UV detection (220 nm).

Fig. 4.18. Plate height versus linear velocity for 9-(l-pyrene)nonanol, last eluting peak in electropherogram in the insert, obtained in a column packed with particles of about 0.5 pm diameter. Column 12 cm packed, 35 cm total length mobile phase 80 20 acetonitrile-50 mM Tris pH 8 voltage 27 kV.

Fig. 4.31. Separation of a test mixture on capillary columns packed by different methods (A) pressure packing, (B) by centripetal forces, using supercritical fluid, and by electrokinetic packing. Columns were 50 pm I.D., 20 cm packed (30 cm total length) mobile phase 80 20 acetonitrile-4 mmol/1 aqueous borate. Separation voltage of 20 kV. Solutes 1, thiourea 2, benzyl alcohol 3, biphenyl 4, dimethylnaphthalene 5, ethylnaphthalene 6, amylbenzene.

Fig. 6.24. Electrochromatographic separation of aromatic acids (a) and anilines (b) on monolithic capillary columns. (Reprinted with permission from [14]. Copyright 2000 Elsevier). Conditions monolithic poly(butyl methacrylate-co-ethylene dimethacrylate) stationary phase with 0.3 wt. % 2-acrylamido-2-methyl-l-propanesulfonic acid pore size, 750 nm UV detection at 215 nm voltage, 25 kV pressure in vials, 0.2 MPa injection, 5 kV for 3 s. (a) capillary column, 100 pm i.d. x 30 cm (25 cm active length) mobile phase, 60 40 vol./vol mixture of acetonitrile and 5 mmol/L phosphate buffer pH 2.4. Peaks 3,5-dihydroxybenzoic acid (1), 4-hydroxybenzoic acid (2), benzoic acid (3), 2-toluic acid (4), 4-chlorobenzoic acid (5), 4-bromobenzoic acid (6), 4-iodobenzoic acid (7). (b) capillary column, 100 pm i.d. x 28 cm (25 cm active length) mobile phase, 80 20 vol./vol mixture of acetonitrile and 10 mmol/L NaOH pH 12. Peaks 2-aminopyridine (1), 1,3,5-collidine (2), aniline (3), N-ethylaniline (4), N-butylaniline (5).

Fig. 6.28. Effect of the hydrophilicity of chiral monolithic columns on the electrochromatographic separation of N-(3,5-dinitrobenzoyl)leucine diallylamide enantiomers (Reprinted with permission from [13]. Copyright 2000 Wiley-VCH). Conditions monolithic column, 100 pm i.d. x 30 cm active length mobile phase, 80 20 vol./vol. mixture of acetonitrile and 5 mmol/L phosphate buffer pH 7 UV detection at 215 nm voltage, 25 kV pressure in vials, 0.2 MPa injection, 5 kV for 3 s. Stationary phase with butyl methacrylate (a), glycidyl methacrylate (b), and hydrolyzed glycidyl methacrylate (c).

Fig. 10.4. Separation of three types of ketones in 50 mM Tris-HCl buffer, pH 7.3 as the mobile phase with the poly(TBAAm-co-AMPS)-coated column. Conditions column, 750 mm x 25 pm i.d. (600 mm effective length) mobile phase, 50 mM Tris-HCl buffer, pH 7.3 field strength, 400 V/cm injection, 12 kV for 1 s at the side of the anode detection wavelength, 254 nm. Peak identification 1, acetone 2, acetophenone 3, butyrophenone. Reproduced with permission from Sawada and Jinno [11].

Figure 33 Electropherogram of threonine and glutamine enantiomers using an amino acid derivative CSP immobilized onto silica particles. Conditions fused silica capillary, 30 cm x 75 mm i.d., packed segment is 15 cm in length, mobile phase is 30/70 5 mM phosphate (pH 2.5)/acetonitrile, field strength is 0.83 kV/cm. For resulting resolution, see Table 2. (Reprinted from Ref. 142, with permission.)...

At low selectivity to achieve the same resolution, one has to use a longer column to increase efficiency and consequently operate under higher-pressure conditions. The relationship between the column length, mobile-phase viscosity, and the backpressure is given by equation (2-17), which is the variation of the Kozeny-Carman equation. Expression (2-17) predicts a linear increase of the backpressure with the increase of the flow rate, column length, and mobile phase viscosity. The decrease of the particle diameter, on the other hand, leads to the quadratic increase of the column backpressure. 

Fig. 1 Electrochromatogram of naphthalene (1), fluoranthene (2), benz[ 3f]anthracene (3), benzo[/ ]fluoranthene (4), and benzo[g/i/]perylene (5), using 1.5-/rm nonporous octadecylsilyl bonded (ODS) particles. Column dimensions 100-/rm i.d. X 6.5-cm packed length (10 cm total length). Mobile phase 70% acetonitrile in a 2-mM Tris solution applied voltage for separation 28 kV injection electrokinetic at 5 kV for 2 s. (Reprinted with permission from Ref. 1.)...

Equation 41 gives the electron acceleration in the channel in terms of the channel length, mobility, and electric field. Substituting in Equation 37, and using... 

The main factors affecting small penetrants permeability in polymeric material include free volume and its distribution, " density, tanperature and pressure, crystallinity," polymer chain length, mobility and packing, solute size, and affinity for the material. In addition, computational parameters used in the simulations such as the type of force field employed and the size of the model also affect the permeability value computed. An increase in tanperature generally leads to a decrease in the solubility and conversely for the diffusion. For all three physical quantities P, S, and D, the tanperature dependence can be described by a Van t Hoff-Arrhenius equation. In particular, for the solubility... 

The column is swept continuously by a carrier gas such as helium, hydrogen, nitrogen or argon. The sample is injected into the head of the column where it is vaporized and picked up by the carrier gas. In packed columns, the injected volume is on the order of a microliter, whereas in a capillary column a flow divider (split) is installed at the head of the column and only a tiny fraction of the volume injected, about one per cent, is carried into the column. The different components migrate through the length of the column by a continuous succession of equilibria between the stationary and mobile phases. The components are held up by their attraction for the stationary phase and their vaporization temperatures. 

The average linear velocity u of the mobile phase in terms of the column length L and the average linear velocity of eluent (which is measured by the transit time of a nonretained solute) is... 

A solute s capacity factor can be determined from a chromatogram by measuring the column s void time, f, and the solute s retention time, (see Figure 12.7). The mobile phase s average linear velocity, m, is equal to the length of the column, L, divided by the time required to elute a nonretained solute. 

To increase the number of theoretical plates without increasing the length of the column, it is necessary to decrease one or more of the terms in equation 12.27 or equation 12.28. The easiest way to accomplish this is by adjusting the velocity of the mobile phase. At a low mobile-phase velocity, column efficiency is limited by longitudinal diffusion, whereas at higher velocities efficiency is limited by the two mass transfer terms. As shown in Figure 12.15 (which is interpreted in terms of equation 12.28), the optimum mobile-phase velocity corresponds to a minimum in a plot of H as a function of u. 

First, solutes with larger electrophoretic mobilities (in the same direction as the electroosmotic flow) have greater efficiencies thus, smaller, more highly charged solutes are not only the first solutes to elute, but do so with greater efficiency. Second, efficiency in capillary electrophoresis is independent of the capillary s length. Typical theoretical plate counts are approximately 100,000-200,000 for capillary electrophoresis. 

In general, the longer a chromatographic column, the better will be the separation of mixture components. In modem gas chromatography, columns are usually made from quartz and tend to be very long (coiled), often 10-50 m, and narrow (0.1-1.0 mm, internal diameter) — hence their common name of capillary columns. The stationary phase is coated very thinly on the whole length of the inside wall of the capillary column. Typically, the mobile gas phase flows over the stationary phase in the column at a rate of about 1-2 ml/min. 

At the beginning of 1992, the largest Hquids pipelines in the United States, based on pipeline length, were Amoco Pipeline Co., 19,096 km Mobil Pipe Line Co., 15,026 km Exxon Pipeline Co., 14,983 km and Conoco Pipe Line Co., 12,980 km. Distances do not include 1316 km of the Trans-Alaska Pipeline with multiple ownership. In both 1991 and 1992, the product pipeline company with the most product deHveries was Colonial Pipeline with 104,990,000 m, more than double the amount deHvered by Santa Ee Pacific Pipelines, Inc. The top pipeline in terms of cmde oil deHveries was the Alyeska Pipeline Service Co., operator of the Trans-Alaska Pipeline System, with movement of 105,735,000 m (3). 

The location of exchangers is the key to maintenance. Usually the back head is kept at a distance of about three meters from the piperack support columns. Access equipment must be able to get in and remove the sheU cover and flange head. Access area must also be provided to handle and remove the sheU cover usually located under the piperack. The tube-pulling or rodding-out area must be kept clear to allow access to the channel end. This space should be at least equal to the tube length and about two meters from the tube sheet location. Tube removal space should be allowed for but is not mandatory if grade-mounted heat exchangers are used and mobile maintenance equipment employed to pick up the entire unit and transfer it to the repair shop. 

The determination of the bond lengths of the fully saturated heteroeyeles has been eomplieated by their eonformational mobility, whieh is eonsidered in Seetion 3.01.5.2. The data whieh have been provided by eleetron diffraetion are listed in Table 6 and show the expeeted trends eonsonant with inereasing size of heteroatom. 

Vertical Pumps In the chemical industiy, the term vertical process pump (Fig. 10-40) generally applies to a pump with a vertical shaft having a length from drive end to impeller of approximately 1 m (3.1 ft) minimum to 20 m (66 ft) or more. Vertical pumps are used as either wet-pit pumps (immersed) or dry-pit pumps (externally mounted) in conjunction with stationaiy or mobile tanlcj... 

The mixture of acetonitrile/water (1 1, v/v) was selected as most effective mobile phase. The optimum conditions for chromatography were the velocity of mobile phase utilization - 0,6 ml/min, the wave length in spectrophotometric detector - 254 nm. The linear dependence of the height of peack in chromathography from the TM concentration was observed in the range of 1-12.0 p.g/mL. 

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