Dynamic mass separation systems

Dynamic mass separation systems use the fact that ions with different masses (accelerated with the same voltage) possess several velocities and consequently their flight times are different. There are about 50 dynamic separation systems known2 using several types of ion movements (linear straight ahead, linear periodic or circular periodic as a function of the electric or magnetic sector field applied). The simplest dynamic mass separation system is a linear time-of-flight (ToF) mass analyzer, and a widely applied mass separation system is the quadrupole analyzer. 

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Ion separation systems can be classified as static ion separation systems and dynamic ion separation systems .1,2 The proposed classification is related to the time dependence of the mass spectrometric ion separation systems during the separation process of the ions. 

Dynamic ion separation systems are based on another physical principle and use the different flight time of ions with different masses and different velocity (e.g., in ToF mass analyzers). In addition, in dynamic ion separation systems there is a time dependent variation of one or more system parameters, e.g., changing of electrical or/and magnetic field strengths, which means the ion motion during the measurement procedure is crucial for the mass spectrometric analysis. 

In order to better understand the detailed dynamics of this system, an investigation of the unimolecular dissociation of the proton-bound methoxide dimer was undertaken. The data are readily obtained from high-pressure mass spectrometric determinations of the temperature dependence of the association equilibrium constant, coupled with measurements of the temperature dependence of the bimolecular rate constant for formation of the association adduct. These latter measurements have been shown previously to be an excellent method for elucidating the details of potential energy surfaces that have intermediate barriers near the energy of separated reactants. The interpretation of the bimolecular rate data in terms of reaction scheme (3) is most revealing. Application of the steady-state approximation to the chemically activated intermediate, [(CH30)2lT"], shows that. 

Separation Dynamics. The mass transport dynamics of the system were examined with respect to extraction, back extraction, and time interval between extraction and back extraction. Concentration gradients limited by diffusion rate must be considered that is, equilibrium with homogenous concentrations of analyte does not describe this system. 

The outcome of a separation depends on fluid dynamics, mass transfer, and chemical kinetics within the system, with the relative importance of each changing with experimental conditions [1]. Porous chromatographic supports are commonly used because they present more surface area per bed volume than nonporous... 

Inherent in all RPC and HlC investigations with peptides or proteins is the question of the end use to which the separated products will be applied. If the task involves purification solely for subsequent primary structure determination (i.e., essentially an analytical task at a semi-preparative scale), then control over preservation of bioactivity may not be necessarily relevant. Obviously, with a new or partially characterized protein, recovery of the component of interest with high mass and bioactivity balance is essential. For preparative methods where subsequent biological uses are contemplated, it is similarly mandatory that the design of the RPC or HlC separation system specifically address recovery issues. High recovery of bioactivity can usually be satisfied without sacrificing the obvious demands of selectivity through proper attention to the physicochemical consequences of the dynamic behavior of the polypeptide or protein of interest in bulk solution and at liquid-solid interfaces. 

When investigating a binary polymer blend system, if the polymer mixture is quenched into an immiscible state then the stable blend will separate into A-rich and B-rich domains, and coarsen with time. In the present study, the system was assumed to be diffusion-controlled and there was no predominant dynamic mass flow. Rather, the composition profile was determined by the free energy minimization, as stated above. 

In the static theory of chemical interaction the perturbation of the energy and the eigenfunctions Ufe( ) is determined with fixed positions of the nuclei. The relative distances R of the atomic centres of mass are hereby not considered as dynamic variables, but as parameters. Then the total perturbed energy of the system, Ek R), becomes a function of the parameter R, and correspondingly the eigenfunction is, except on the dynamical variables separately dependent upon R fc(0... 

Particle methods (Molecular Dynamics, Dissipative Particle Dynamics, Multi-Particle Collision Dynamics) simulate a system of interacting mass points, and therefore thermal fluctuations are always present. The particles may have size and structure or they may be just point particles. In the former case, the finite solvent size results in an additional potential of mean force between the beads. The solvent structure extends over unphysically large length scales, because the proper separation of scale between solute and solvent is not computationally realizable. In dynamic simulations of systems in thermal equilibrium [43], solvent structure requires that the system be equilibrated with the solvent in place, whereas for a structureless solvent the solute system can be equilibrated by itself, with substantial computational savings [43]. Finally, lattice models have a (rigorously) known solvent viscosity, whereas for particle methods the existing analytical expressions are only approximations (which however usually work quite well). 

The present book is devoted to both the experimentally tested micro reactors and micro reaction systems described in current scientific literature as well as the corresponding processes. It will become apparent that many micro reactors at first sight simply consist of a multitude of parallel channels. However, a closer look reveals that the details of fluid dynamics or heat and mass transfer often determine their performance. For this reason, besides the description of the equipment and processes referred to above, this book contains a separate chapter on modeling and simulation of transport phenomena in micro reactors. 

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