Pressure-assisted

Sephacryl gels were preswelled in H20(dest) -I- 0.01% Merthiolate. The diluted and degassed gels were then packed at medium pressure assisted by a pump-sucking eluent with a flow rate of approx 0.4 ml/min. 

The use of ultrasonic (US) radiation (typical range 20 to 850 kHz) to accelerate Diels-Alder reactions is undergoing continuous expansion. There is a parallelism between the ultrasonic and high pressure-assisted reactions. Ultrasonic radiations induce cavitation, that is, the formation and the collapse of microbubbles inside the liquid phase which is accompanied by the local generation of high temperature and high pressure [29]. Snyder and coworkers [30] published the first ultrasound-assisted Diels-Alder reactions that involved the cycloadditions of o-quinone 37 with appropriate dienes 38 to synthesize abietanoid diterpenes A-C (Scheme 4.7) isolated from the traditional Chinese medicine, Dan Shen, prepared from the roots of Salvia miltiorrhiza Bunge. 

Jia, Z., Ramstad, T., Zhong, M. Medium-throughput pfC, screening of pharmaceuticals by pressure-assisted capillary electrophoresis. Electrophoresis... 

R. B. Screening of octanol-water partition coefficients for pharmaceuticals by pressure-assisted microemulsion electrokinetic chromatography. 

Ishihama et al. [147] have describe a rapid screening method for determining pK values of pharmaceutical samples by pressure-assisted CE, coupled with a photodiode array detector. Each CE run was completed in less than 1 min, so a 96-well microtiter plate could be measured in one day. Determinations of the pKa values of 82 drugs illustrated this interesting new method. 

Ishihama, Y. Nakamura, M. Miwa, T. Kajima, T. Asakawa, N., A rapid method forpKa determination of drugs using pressure-assisted capillary electrophoresis with photodiode array detection in drug discovery, j. Pharm. Sci. 91, 933-942 (2002). 

Pressurization of the vials at both the inlet and the outlet ends of the CEC capillary column packed with particles to about 1.2 MPa is required to prevent formation of bubbles that lead to a noisy baseline. Typically, equal pressure of an inert gas such as nitrogen is applied to both vials to avoid flow that would otherwise occur resulting from the pressure difference. Hydraulic pressure applied only at the inlet end of the capillary column is occasionally used in pressure-assisted electrochromatography [38,39]. 

The pK screening methodology was further standardized and optimized for high-throughput measurements. Current developments are the use of a commercially available 96 capillary instrument including the corresponding evaluation software, the use of commercially available separation kits and pressure-assisted CE to shorten the run times. 

For the rapid pKa measurement with daily throughput of 96 compounds using a pressure-assisted mode with a photodiode array detector, the following modifications were required. 

Figure 4 presents an example of rapid pKa measurement using a pressure-assisted system in combination with a photodiode array (PDA) detector. The migration time of DMSO (EOF marker) was measured at 220 nm, whereas the migration time of the analyte, naphazoline, was measured at 270 nm. The CE run time as well as data analysis time was drastically reduced. Consequently, this system allows the analysis of more than 96 compounds in one day. The limitation of this method is the application to drugs without UV chromophore at more than 250 nm. In some cases, it was effective to remove DMSO by evaporation under vacuum followed by the addition of methanol or acetonitrile as a neutral marker. 

Capillary electrophoresis is one of the powerful tools for pA(, measurement, especially when the pressure-assisted CE system with PDA detector is employed. It allows one to measure pA(, values of more than 96 candidate drugs... 

Jia, Z., Mei, L., Lin, F., Huang, S. and Killion, R.B. (1007) Screening of octanol-water partition coefficients for pharmaceuticals by pressure-assisted microemulsion electrokinetic chromatography. Journal of Chromatography A, 2003, 203-208. 

Zong Q, Osmulski PA, Hagar LP (1995) High-Pressure-Assisted Reconstitution of Recombinant Chloroperoxidase. Biochemistry 34 12420... 

The possibility to obtain a uniformly dispersed composite powder was shown for the a-Fe-Al203 system where metal particles with an average size of 55 nm were formed in an amorphous/nano alumina matrix.18 Other studies attempting to obtain dense bulk composites based on the sol-gel route using conventional pressure-assisted sintering ( 1400°C and an applied force of 10 MPa) resulted in a coarse microstructure.16 However, if reaching theoretical density is not a necessary requirement, a porous ceramic microstructure containing nanometer-sized metal particles can be used as a catalytic material.19 Certain combinations of composite materials demand... 

Pressure-assisted chelating extraction (PACE) Novel technique for the digestion of metals in solid matrices 66... 

Wanekaya, A.K., S. Myung, and O.A. Sadik. 2002. Pressure assisted chelating extraction A novel technique for digesting metals in solid matrices. Analyst 127 1272-1276. 

The use of capillary electro-chromatography for the separation of etodolac and its metabolites has recently been reported [26, 27], Separation of etodolac was achieved using 3 different methods capillary HPLC, capillary electro-chromatography (CEC), and pressure assisted CEC. Fused-silica capillaries of 100 pm i.d. were packed with 5 pm octadecyl silica (Cig) under 400 bar pressure. The length of the packed capillaries was 24.5 cm. 

In another report, separation of etodolac and its metabolites was studied using three different capillary techniques, capillary HPLC, CEC, and pressure assisted CEC, with either UV detection or ion trap mass spectrometer [27]. Baseline separation of all compounds was achieved in different modes and conditions. 

As mentioned earlier, that it is possible to simultaneously apply a high hydraulic pressure at the inlet vial to drive the solvent through the column and an electrical field. This hybrid method combining both pressure and electrodriven liquid chromatography was first introduced by Tsuda [46] and is referred to as pressure assisted CEC or field assisted micro HPLC. Verheij et al. [47] used this the technique to couple CEC with MS. These authors also proposed the name pseudo-CEC for this technique. 

The section of the table topped by the heavy bar indicates the "packed CEC" region and it is these areas which are to be covered in this chapter. There is considerable scope for overlap between the described cells, and many further divisions of these artificial boundaries are possible, for example pressure-assisted electrochromatography (PEC) describes a continuum from pure CEC to pure pLC. 

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