Merck® Chromolith

FIGURE 6.6 Merck Chromolith monolithic RPLC column at 1 mL/min (top) and 2 mL/min with various injection volumes. Protein standards A = aprotinin, B = cytochrome C, C = carbonic anhydrase. 

The liquid chromatograph Zarghi et al. used consisted of a Wellchrom K-1001 pump, Rheodyne 7125 injector, Eurochrom 2000 integrator, and K2600 fluorescence detector. The stationary phase was a Merck Chromolith Performance RP-18e column (100 x 4.6 mm). The mobile phase consisted of 0.01M dibasic sodium phosphate buffer and acetonitrile (60 40 v/v) adjusted to pH 3.5. The flow rate was 2 mL/min. The detector operated at an excitation wavelength of 240 nm and an emission wavelength of 340 nm. Letrozole served as the internal standard (IS). 

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.)... 

Improvements in the selectivity of the separation of microcystins and nodnlarin have been achieved by selecting the most efficient stationary phase, with this aim (Spoof 2002) compared a monolithic C-bonded silica rod colnmn (Merck Chromolith) to particle-based C and antide C 18 18 16 sorbents in the HPLC separation of eight microcystins and nodularin-R. Two gradient mobile phases of aqneons trillnoroacetic acid modified with acetonitrile or methanol, different flow-rates, and different gradient lengths were tested. The performance of the Chromolith colunrn measured the resolution of some microcystin pairs. The selectivity, efficiency (peak width), and peak asymmetry equalled, or exceeded, the performance of traditional particle-based columns. The Chromolith 21 colnmn allowed a shorteiting of the total analysis time to 4.3 minutes with a flow rate of 4 ml/minute. 

Two main manufacturers of monolithic colunms are commercially available, i.e. Phenomenex Onyx (CIS, C8, HD-C18, Si) [37] and Merck Chromolith [38]. Some examples of the implementation of different chromatographic approaches combined with flow techniques are described below. 

Alnouti et al. (2005) used Symbiosis to measure propranolol and diclofenac in rat plasma. Twelve different SPE cartridges were screened. A C18 HD (2 x 10 mm inner diameter, Spark) was chosen because it provided the best recovery and peak shapes. When a Luna C18 (2.1 x 50 mm, 5 /an, Phenomenex) was used, the run time was 4 min it was 2 min when a monolithic Chromolith C18 (50 x 2.1 mm, Merck KgaA) column was used. 

Another approach is increasing throughput via a monolith analytical column. Vintiloiu et al. (2005) used a self-made RAM online SPE under turbulent flow conditions to measure rofecoxib, a cyclooxygenase-2 inhibitor, in rat plasma. They constructed a cartridge (0.76 x 50 mm) packed with LiChrosphere 60 RP-18 ADS particles (40 to 63 /an, Merck KgaA). The analytical column was a Chromolith Speed ROD (RP-18, 50 x 4.6 mm, Merck KgaA). The injection volume was... 

Phenyl (Cohesive Technologies), the polymer-based Oasis HLB (Waters), the Cyclone (Cohesive Technologies), and the porous graphitized carbon-based Hypercarb (ThermoHypersil, Cheshire, UK) Cohesive s 2300 system was the HTLC component. Merck s monolithic reversed-phased Chromolith Speed ROD (RP-C18 (50 x 4.6 mm) served as the analytical column. The Oasis HLB, Cyclone TFC, and Hypercarb yielded the best retention capacity and good elution efficiency and volume. Recovery was 42 to 94% with a sample volume of 10 mL. Run time was 14 min. LODs were 0.4 to 13 ng/L for most compounds. 

The absolute permeability (8 x 10 ° cm ) of currently available silica monoliths (Chromolith, Merck) is similar to that of columns packed with 9 jm particles [213], To increase efficiency, columns are usually packed with particles of 2, 3, and 5 jm, which possess absolute permeabilities of approximately 4x10 ", 9x10 ", and 2.5xl0" °cm, respectively. If we try to compare columns packed with 5 pm particles and monolithic columns with through-pores of an average size of 1.5 pm, we observe that the permeability of the monolithic columns is around three to four times larger than that of packed columns. 

Monolithic silica Cj3 reversed phase Chromolith RP-18 Merck KgaA 100 X 4.6 mm 50 X 4.6 mm 25x4.6 mm Swift RP analysis of small molecules... 

Monolithic silica Cj reversed phase Chromolith RP-8 Merck KgaA 100x4.6 mm Analysis of small molecules and hydrophobic peptides... 

Monolithic siUca Underivatized Chromolith Prep Si Merck KgaA 100x25 mm Preparative chromatography of small molecules... 

Monolithic silica C,8 reversed phase Chromolith CapRod Merck KgaA 150x0.1 mm Proteome research, analysis of peptides and protein digests... 

Figure 3-4. Pore size distribution of different HPLC materials. Allure Silica (Restek) Allure-PFPP (Restek), Prodigy-Silica (Phenomenex) Chromolith CIS (Merck KgaA, Germany) and research-type ordered silica with highly uniform pores of 50-A pore diameter.

Continuous beds including methacrylate-based disks CIM QA from BIA Separations (Figure 3.22) and SWIFT from Isco, acrylamide UNO monoliths from Bio-Rad, Ultimate polystyrene divinylbenzene disks from LC-Packings, cellulose-based Seprasorb monoliths from Sepragen and silica units Conchrom from Conchrom or Chromolith from Merck are also... 

Q, S, and E) Fractoflow, Chromolith Merck (Germany) Hollow fibers, monolithic rods Polyamide, silica lEX, RP... 

Fig. 3.3 SEM picture of a monolithic silica packing (Chromolith , Merck KGaA, Darmstadt, Germany).

One of the greatest challenges in monolith production is to increase the diameter. Presently, silica monoliths with a diameter of up to 50 mm can be produced. Commercial monolithic silica columns e.g. Chromolith columns of Merck KGaA possess a column permeability equivalent to a column packed with 15 xm particles, but show a column performance of a column packed with 5 xm beads. The major benefit of monolithic columns, however, is their robustness in use, their tailored pore structure and the tunable surface chemistry. 

Surprisingly, the first commercial monolith, Chromolith, introduced by Merck EKaA, is an analytical sized column, available as 50- and 100-mm x 4.6-mm i.d.25 The major advantage of Chromolith is the lower pressure drop, which is claimed by the manufacturer to have the performance of 3-pm particles and pressure drop of 5-pm particles (Figure 3.23). Attempts to manufacture smaller-diameter columns have met with considerable difficulties, particularly with the cladding or the external bonding of these preformed... 

In order to study reactions in liquid phase, it is necessary to develop new experimental techniques that will allow operando spectroscopy and transient studies of liquid phase heterogeneous catalytic reactions. Essential for such technique is a reactor module. Chromolith HPLC column (Merck) [1] with sihca foam in a polymer cartridge is suitable as a reactor for transient experiments because the high surface area silica foam can act as support with relatively low pressure drop. However, thermal stability of this HPLC column is limited to low temperatures because of the polymer housing (<150°C). It is... 

Herbicide separations were carried out using a Chromolith Performance RP-18e column with 100 mm x 4.6 mm from Merck, protected using Onyx SecurityGuard cartridges (4 x 3.0mm) from Phenomenex. All sample analysis were performed with a flow rate of 1 ml/min at gradient mode. The eluents were acetonitrile/water solutions (solution A 35/65 solution B 90/10), adjusted to pH = 2.8 using a formic acid solution (Panreac, 98%). 

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