ABSTRACT
The lack of a sensitive, linear detector was probably the greatest single impediment to the evolution of liquid chromatography (LC) in the years past. The development of LC detectors proved to be far more difficult than their gas chromatography (GC) counterparts. Unfortunately, very low concentrations of solute vapor in a gas modify the physical properties of the gas to a far greater extent than the same concentration of solute will modify the physical properties of a liquid. Nevertheless, despite the sensitivity problems, many LC detectors have been developed over the past 30 years, based on a variety of different sensing principles. During the 1950s, 1960s, and 1970s a considerable number of sensing methods were examined with a view to their being developed into an LC detector. However, the field has narrowed, and today, most LC separations are monitored by one of four detectors: the UV detector, the fluorescence detector, the electrical conductivity detector, and the refractive index detector. Other detectors have found certain areas of application; the high sensitivity of the electrochemical detector to those substances that readily oxidize or reduce has been used for certain types of trace analysis; the so-called molecular weight detector that functions on the basis of scattered light measurement has also found use in the detection of large molecular weight biopolymers. However, the four detectors mentioned satisfy the needs of most contemporary analytical separations.
