Topics - Sensors
In chromatography the term sensor
refers to the device that senses the presence of the solute in the column eluent and provides a signal (usually electrical in nature) that is a function of either the mass of solute or the concentration of solute passing through it. A chromatography detector consists of essentially two parts
, the sensor
and the modifying electronics
, the latter modifies the sensor signal and provides an output to a recorder or computer that is linearly related to the concentration or mass of solute passing through the sensor. The sensor may take the form of a light absorption cell as in the UV detector, a conductivity cell as in the electrical conductivity detector, a fluorescence cell in the fluorescence detector etc. The sensor will inevitably have an actual finite volume and this volume must be kept very small to avoid peak dispersion in the sensor. As a rule of thumb the sensor volume should be no greater than one third or the volume standard deviation of the narrowest peak to be eluted. The connecting tube to the sensor is also considered to be part of the sensor and must be kept short and of narrow diameter to reduce peak dispersion. If available, low dispersion tubing can be used effectively for column sensor connections.