Flow-through cell detection description

A complete description of the flow-through detector, including operating conditions, should be provided. In spectrophotometry, the flow cell is usually distinct from the detector therefore, its description, including light optical fibres (if relevant), is required. It is important to specify the inner volume and optical path length of the flow cell and, for specific applications, e.g., multi-site detection [114], information about its illuminated portion is also relevant. In luminometric procedures, the shape of the flow cell as well as its arrangement in relation to the detector should also be reported. 

A variety of experimental techniques have been used for the determination of uptake coefficients and especially Knudsen cells and flow tubes have found most application [42]. Knudsen cells are low-pressure reactors in which the rate of interaction with the surface (solid or liquid) is measured relative to the escape through an aperture, which can readily be calibrated, thus putting the gas-surface rate measurement on an absolute basis. Usually, a mass spectrometer detection system monitors the disappearance of reactant species, as well as the appearance of gas-phase products. The timescale of Knudsen cell experiments ranges from a few seconds to h lindens of seconds. A description of Knudsen cell applied to low temperature studies is given [66,67]. 

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