Monolithic columns temperature

Fig. 4. Effect of the flow velocity on the back pressure in a molded poly(glycidyl methacrylate-co-ethylene dimethacrylate) 100 mm x 8 mm monolithic column (Reprinted with permission from [62]. Copyright 1996 American Chemical Society). Conditions mobile phase tetrahy-drofuran polymerization mixture glycidyl methacrylate 24%, ethylene dimethacrylate 16%, cyclohexanol and dodecanol contents in mixtures 54/6%, temperature 80 °C (line 1), 54/6,70 °C (line 2), 54/6,55 °C (line 3), and 57/3,55 °C (line 4)...

Section II covers the latest trends in reducing sample preparation time, including direct sample infusion/injection and on-line solid phase extraction (SPE). In Section III, we focus on newer trends in stationary phases and how these phases hope to offer different selectivities compared to current CIS-based phases. Section IV briefly provides a few observations on how new detectors are increasing the versatility of HPLC. Finally, in Section V we examine monolithic columns, small particles packed in short columns, high-temperature LC, ultra high-pressure LC, and parallel injection techniques. 

FIGURE 14.5 Analysis of rainwater spiked with 0.3 mM H+, Na+, NHJ, K+, Ca +, Mg +. Column DS-coated monolithic stationary phase (Merck Chromolith, 50x4.6mm). Column temperature 35°C. Eluent 2mM ethylenediamine, 0.1 mM Li-DS, pH 6. Flow rate 4.0mL/min. Loop volume lOOpL. (From Xu, Q. et ah, J. Chromatogr. A, 1026, 191, 2004. Copyright 2004. With permission from Elsevier.)... 

Figure 29 Separation of the nonsteroidal anti-inflammatory drugs ibuprofen (peak 1), naproxen (2), ketoprofen (3), and suprofen (4) in anion-exchange CEC mode using a strong anion-exchange monolithic column. Conditions on-column alkylated monolith prepared from mixtures consisting of 8% 2-dimethylaminoethyl methacrylate, 24% 2-hydroxyethyl methacrylate, 8% ethylene dimethacrylate, 20% cyclohexanol, 40% 1-dodecanol UV-initiated polymerization at room temperature for 16 h cfpmode= 1423 nm. Column dimensions inner diameter 0.1 mm, total length 335 mm, effective length 250 mm. Mobile phase 0.4 mol/L acetic acid and 4 mmol/L triethylamine in acetonitrile/methanol (60/40), voltage -25 kV, injection -5 kV for 5 s, temperature 50°C, UV detection at 250 nm. (Reprinted from Ref. 127, with permission.)...

When UHPLC is available, it is additionally recommended to use a long column filled with sub 2 pm particles - possibly think also of core shell or monolith columns, see Chapter 5 - at a high flow, run a steep gradient and additionally increase the temperature. A trick that, with many similar components, often leads to good resolution and narrow peaks start with high %B and run a relatively flat gradient. For further information regarding peak capacity, see Chapter 3. 

Chromatograms of puUulans and proteins through the monolithic columns were recorded on a JASCO HPLC system (Jasco CO. Ltd., Tokyo, Japan) using PBS as eluent at room temperature. The flow rate was 0.2 ml/min. 

Plot of molecular weight Mpui vs elution volume v for pullulans (filled squares and solid curve) and proteins (open circles) eluted through the PHEMA-grafted monolithic column. The molecular weights of the proteins are the reduced values independently determined by pullulan-calibrated GPC. The arrow head shows the so-called ghost peak of the eluent. The flow rate was 0.2 ml/min with PBS as eluent at room temperature. The inset shows a cartoon illustrating two size-exclusion modes of the brush-modified monolith. 

Although Fields already mentioned the possible preparation of monolithic silica-based CEC columns, the lack of experimental data leads to the assumption that this option has not been tested [111]. In fact, it was Tanaka et al. who demonstrated the preparation of monolithic capillary columns using a sol-gel transition within an open capillary tube [99,112]. The trick was in the starting mixture that in addition to tetramethoxysilane and acetic acid also includes poly(ethylene oxide). The gel formed at room temperature was carefully washed with a variety of solvents and heated to 330 °C. The surface was then modified with octadecyl-trichlorosilane or octadecyldimethyl-A N-dimethylaminosilane to attach the hy-... 

Fig. 11. Separation of a mixture of organic solvents using 50 cm long 100 (left) and 320 pm i.d. (right) monolithic capillary columns (Reprinted with permission from [112]. Copyright 2000 Wiley-VCH). Conditions temperature gradient 120 - 300 °C, 20 °C/min, inlet pressure 0.55 MPa, split injection. Peaks methanol (1), ethanol (2), acetonitrile (3), acetone (4), 1-propanol (5), methyl ethyl ketone (6), 1-butanol (7),toluene (8), ethylbenzene (9),propylbenzene (10),butyl-benzene (11)...

Fig. 12. Separation of styrene oligomers by reversed-phase (left) and size-exclusion chromatography (right) (Reprinted with permission from [121]. Copyright 1996 American Chemical Society). Conditions (left) column, molded poly(styrene-co-divinylbenzene) monolith, 50 mm x 8 mm i.d., mobile phase, linear gradient from 60 to 30% water in tetrahydrofuran within 20 min, flow rate 1 ml/min, injection volume 20 pi UV detection, 254 nm (right) series of four 300 mm x 7.5 mm i.d. PL Gel columns (100 A, 500 A, 105 A, and Mixed C), mobile phase tetrahydrofuran, flow rate, 1 ml/min injection volume 100 pi, toluene added as a flow marker, UV detection, 254 nm temperature 25 °C,peak numbers correspond to the number of styrene units in the oligomers...

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