Analytical dosing pumps

As in the molecular beam experiment, the reactor volume, pumping speed, and rate of introduction of reactants have values which lead to a flux of reactants well defined in time. Strozier, however, simply doses gas into the vacuum system (reactor) rather than using a molecular beam. He studied CO oxidation, which has nonlinearities in the surface rate equation, so that computer rather than analytic solutions are necessary. The results are represented at constant frequency and varying temperature as shown in Fig. 8, which is a computer simulation (37). 

In all assays, aliquots are withdrawn from the receiving phase in defined time intervals and the concentration of the analyte is determined via a calibration curve (Figure 3b). Alternatively, the concentration in the receiving phase can be continuously monitored when a pump and a flow cuvette are available. For quantitative analysis, kinetic traces are measured for increasing carrier concentrations, and the obtained dose-response curves are analyzed with the Hill equation to reveal the EC50, which is the effective concentration needed to observe 50% of the maximal activity, and the Hill coefficient n (Figure 3c, Section 4.2). 

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