Liquid injection sequence

A pulse test procedure [6] begins with an injection of a small pulse of the feed mixture to be separated into a desorbent stream flowing through a packed adsorbent column at a fixed flow rate and temperature. The on-line column effluent composition is then determined as a function of time or volume of desorbent passed by gas or liquid chromatography. Particularly important is the sequence and time when each of the feed components exit the packed adsorbent column because these characteristics describe the specific adsorbate and adsorbent interactions. By determining the interactions using the pulse test, the separation process can be optimized. 

The score plot in Figure 9.12 shows the whole start-up sequence empty bed, bed filling, injection of liquid urea, and production. The score plot for the process data can be seen in Figure 9.13. 

In the case of a liquid rocket (Figure 1.5), the propellant has to be injected into the combustion chamber in a controlled manner. Thus two storage tanks are required for storing the fuel and oxidizer. A supply system to introduce the fuel and oxidizer in controlled quantities in the proper sequence is also an additional requirement. The fuel and oxidizer are to be transferred to the storage tanks only... 

The older tall oil distillation columns used bubble cap trays. In new columns, structured packing is preferred. Because of the low pressure drop of structured packing, steam injection is no longer necessary. The low liquid holdup of this packing minimizes the reactions of the fatty and resin acids. A specific distillation sequence for vacuum columns using structured packing of Sulzer has been described (26). Depitching is carried out at a vacuum of... 

The aliquots of the solution-state chemical synthesis samples were directly injected into a standard HPLC-NMR probe by using a robotic liquid handler. The NMR software was used to automatically find and suppress the intense NMR signals from any non-deuterated solvents used, typically using the WET sequence [5]. Unlike the characterisation of impurities in organic compounds (see the next section) or drug metabolites (see the appropriate chapter in this volume) where the proportions of the analytes can be very different, combinatorial chemistry samples tend to be all of similar quantity and this simplifies the analysis in that it is not usually necessary to worry overly about carry-over of material from sample to sample, nor it is necessary to readjust the NMR spectrometer receiver gain after every sample, thus saving considerable machine time. 

Adsorption Chromatography. The principle of gas-solid or liquid-solid chromatography may be easily understood from equation 35. In a linear multicomponent system (several sorbates at low concentration in an inert carrier) the wave velocity for each component depends on its adsoiption equilibrium constant. Thus, if a pulse of the mixed sorbate is injected at the column inlet, the different species separate into bands wliich travel through the column at their characteristic velocities, and at the outlet of the column a sequence of peaks corresponding to the different species is detected. Measurement of the retention time (tl) under known flow conditions thus provides a simple means of determining the equilibrium constant (Henry constant) ... 

The basic components of the system are a liquid driver with only one carrier stream, a multi-port selection valve and a detector (Fig. 2.9). The valve is the heart of the sequential injection system and normally comprises 6—10 peripheral ports and a central port in a multi-position valve configuration. The central port is linked to a holding coil and the peripheral ports are connected to different solution aspiration tubes and transmission lines that are linked to different manifold components, e.g., detector and mixing chamber. Only one peripheral port is connected to the central port at any one time. Stream management inside the holding coil is accomplished by a bi-directional piston (or peristaltic) pump. The analyser is fully computer controlled and the injection volumes, residence times, delivery of solutions and analytical path lengths are selected based on a valve timing sequence and related flow rates. 

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