Liquid Chromatography Detectors - Introduction > Page 1

Introduction

Although chromatography was discovered late in the 1890s its development was almost negligible until the 1940s and this was largely due to the lack of an inline sensitive detector. The first, effective inline liquid chromatography (LC) detectors were the refractive index detector reported by Tiselius and Claesson (1) in 1942 and the conductivity detector described by Martin and Randall (2) in 1951. These two devices should have evoked a growth in LC development, but, in the early fifties, gas chromatography (GC) was invented which completely eclipsed the development of LC. It was not until the early 1960s that the renaissance of LC took place, initially based on the use of the refractive index of Tiselius and Claesson. Although a significant number of GC detectors were developed over two or three years, the development of LC detectors was much slower, largely due to the fact that low concentrations of solute in a liquid do not change the properties of a liquid nearly as much as they do a gas. In fact, the development of LC detectors was gradual and arduous.

In a similar way to the development of GC there has been a continuous interaction between improved detector performance and improved column performance. Initially, separations monitored by detectors with improved sensitivity permitted a precise column theory to be developed and experimentally substantiated. This allowed new columns to be designed with reduced dispersion and higher efficiencies. The improved efficiencies, however, produced small volume peaks, small, that is, compared with the volume of the detector sensor and the dispersion that took place in the conduits of the detector system.. As a consequence, the ultimate efficiency obtainable from the column was determined by the geometry of the fluid conduits of the detector and not its sensitivity. This provoked detector redesign, with smaller sensor volumes, different geometry and shorter connecting tubes between the column and sensor. In turn, these modifications allowed much smaller particles to be used in the column resulting in even lower column dispersion and higher efficiencies. In this way, just as in GC, detector design and column design have interacted over the years to a point where the performance of LC columns are now commensurate with those of GC columns.