Alcohols column length

Columns lengths of 10-25 m with a 0.32-mm ID and 10-/tm film thickness are available commercially. These phases are ideal for the separation of analytes in aqueous solutions or trace analysis of residual water, because the hydrophobic nature of the polymer allows water to be eluted as a sharp peak. The upper operational temperature of 250°C makes these phases a good choice for the separation of polar light hydrocarbons and alcohols. At subambient temperatures oxygenated gases such as CO and C02 are separated without tailing. 

Figure 16.17 Simultaneous breakthrough profiles of 2-butanol and tert-amyl alcohol on a carbon column. Comparison of experimental (symbols) and calculated (hnes) profiles, (a) Column length, 82 cm Cq,i = Cq = 1 mg/mL. Calculated profiles with solid lines, kf2 = 1-95 X 10 cm/s dashed lines, fcy2 = 1-68 x 10 cm/s. (b) Column length 41 cm, Cq,i = Cq,2 = 1 mg/mL. Calculated profiles with solid lines. Dpi = 7.40 x 10 cm /s dotted lines. Dpi = 7.77 x 10 cm /s dashed lines. Dpi = 7.03 x 10 cm /s. Reproduced with permission from A.l. Liapis and D.W.T. Rippin, Chem. Eng. Sci., 33 (1978) 593 (Figs. 2 and 5).

Fig. 9.1. (A) Chromatogram of a ten

Z. Atamna, G.M. Muschik and H.J. Issaq, Effect of Alcohol Chain Length, Concentration and Polarity on Separations in High-Performance Liquid Chromatography Using BondedCyclodextrin Columns, J. Chromatogr., 499(1990)477. 

A limiting parameter for the choice of alcohol is viscosity. Most hybrid micellar phases obtained with alcohol addition have a higher viscosity than the corresponding micellar phase without alcohol. Viscosity increases dramatically with the alcohol chain length. The viscosity of the 0.285 M SDS phase was 1.65 cP producing a 95 kg/cm (9.5 MPa or 1400 p.s.i.) pressure at 1 mL/min with a 10 cm column. The viscosity of the 5% v/v pentanol SDS phase was 2.32 cP producing a 127 kg/cm (12.7 MPa or 1800 p.s.i.) pressure [25]. The viscosity of the 5% hexanol SDS phase was 11.8 cP which precluded its use at 1 mL/min. 0.5 mL/min flow rate was used. This has likely produced overestimated efficiencies for the hexanol points of Figure 6.4. 

Tetrahydrofuran may be purified by refluxing over solid potassium hydroxide, followed by distillation from lithium alu-miniun hydride. Tetrahydrofuran may be replaced by ethylene glycol dimethyl ether (dimethoxyethane). The submitter has indicated that either solvent may be freed conveniently from water, alcohols, and moderate amounts of peroxides by passing the commercial solvent through a column (2 in. diameter X 2-3 ft. length) of Linde Air Products Molecular Sieves (type 13A iQ- n. pellets), at a rate of approximately 100 ml. per minute. 

Methyl alcohol of very high purity can be obtained by fractional distillation using a column of 1-3 metres effective length and then refluxing with aluminium amalgam. It is then refluxed under a column packed with dehydrated copper sulphate, to remove ammonia. A sensitive test for acetone and formaldehyde is the addition of cone, mercuric cyanide solution, in 6N-sodium hydroxide. A white precipitate indicates ketone if it darkens on standing aldehyde is also present. (J. C. S., 127, 2552.)... 

There are two classes of stationary phases in SEC, one type for GFC and the other for GPC. Stationary phases for GFC are hydrophilic and include polydextrans, polyvinyl alcohol gel, and silica gel those for GPC are hydrophobic, typically cross-linked, rigid polystyrene-divinylbenzene gels. Generally, columns of 15 to 50 cm length are used, packed with 7- to 10-/t,m particles and with an internal diameter between 0.6 and 0.8 cm. In SEC, unlike in other chromatographic modes, the stationary phase is the primary factor controlling retention. 

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. 6.21. Electrochromatographic separation of benzene derivatives on monolithic capillary column prepared by UV initiated polymerization. Conditions capillary column, 100 pm i.d. x 25 cm active length stationary phase poly(butyl methacrylate-co-ethylene dimethaciylate) with 0.3 wt. % 2-acrylamido-2-methyl-l-propanesulfonic acid pore size, 296 nm mobile phase, 75 25 vol./vol mixture of acetonitrile and 5 mmol/L phosphate buffer pH 7 UV detection at 215 nm 25 kV pressure in vials, 0.2 MPa injection, 5 kV for 3 s. Peaks thiourea (1), benzyl alcohol (2), benzaldehyde (3), benzene (4), toluene (5), ethylbenzene (6), propylbenzene (7), butylbenzene (8), and amylbenzene (9).

---