Stopped-flow high pressure system

Gluodenis, T.J., Tyson, J.E. Elow injection systems for directly coupling on-line digestion with analytical atomic spectrometry. Part 1. Dissolution of cocoa under stopped-flow, high-pressure conditions. J. Anal. At. Spectrom. 7, 301-306 (1992)... 

Other high-pressure stopped-flow/CL systems are based on special mixing modes, the main technical difference of which is that the CL observation cell... 

Figure 6 Schematic diagrams of atypical high-pressure SF-CL systems based on special mixing modes (a) system based on conventional propelling and stopping syringe and (b) system based on liquid chromatographic (LC) pumps and stopping the flow before the mixer (M). V, six-ports valve. (Adapted from Refs. 33 and 34.)...

The systems that we investigated in collaboration with others involved intermolecular and intramolecular electron-transfer reactions between ruthenium complexes and cytochrome c. We also studied a series of intermolecular reactions between chelated cobalt complexes and cytochrome c. A variety of high-pressure experimental techniques, including stopped-flow, flash-photolysis, pulse-radiolysis, and voltammetry, were employed in these investigations. As the following presentation shows, a remarkably good agreement was found between the volume data obtained with the aid of these different techniques, which clearly demonstrates the complementarity of these methods for the study of electron-transfer processes. 

High (linear) flow rates are reqnired to indnce turbulent mixing and to minimize the time between mixing and observation or quenching, known as the dead time . Due to the high flow rates, the pressure in the system increases. The working pressure of the mixing devices described above is maximally 10 bar (stopped-flow) and may be up to 20 bar in RFQ when viscous solutions are used. 

In many cases, the extraction process includes an additional, static extraction step. To this end, the outlet valve (OV in Fig. 6.10) is supplemented by an inlet valve (IV in Fig. 6.10) between the high-pressure pump and the extractor. Once the system has been pressurized, the inlet valve is closed, the high-pressure pump stopped and the oven temperature raised. After the desired temperature is reached, the system is maintained under a static regime with both valves closed, and then the valves are opened and the pump restarted to allow the solvent to flow over the dynamic extraction period. Several studies [147,150,153] have shown that a combination of both extraction modes can result in substantially improved extraction and shorter extraction times. This is commented on in greater detail in discussing specific applications below. 

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