Gas Chromatography Detectors - Flow Sensitivity > Page 18


Thus, a knowledge of (NP) can be used in detector design when a particular sensitivity is the objective.


Flow Sensitivity

Flow sensitivity is another detector property that can have a significant effect on long term noise and, consequently, also on the detector MDC. Again it is the bulk property detectors that are the most likely exhibit high flow sensitivities (e.g., the katharometer). To reduce its flow sensitivity, the katharometer is usually fitted with a reference cell through which a flow of mobile phase also passes. The two sensors for the column flow and the reference flow are placed in the arms of a Wheatstone bridge so that any changes in flow rate are to a large extent compensated. The flow sensitivity (DQ) is defined in a similar manner to pressure sensitivity (i.e. mV/ml/min). The flow sensitivity can be used to calculate the flow change (NQ) that would provide a signal equivalent to the detector noise (ND),



A knowledge of (NQ) is also be utilized in detector sensor design to minimize long term noise.