ABSTRACT
Contemporary liquid chromatographic procedures are now well developed, accurate and reliable and both high speed [1-3] and high resolution columns [2,4,5] have been available for some years. There are, at present, a veritable plethora of detectors available to the practicing chromatographer. In spite of this however, as already stated, the vast majority of contemporary LC analyses are carried out employing one of four detectors: namely, either some form of UV detector, the fluorescence detector, the electrical conductivity detector or, to a significantly lesser degree, the refractive index detector. There remains, notwithstanding, the need for a detector having greater versatility; a detector, for example, that concurrently monitors more than one property of the solute and thus increases the range of solutes types that can be sensed. In addition, such a detector could help confirm the identity of the eluted solute. The latter is often achieved by the use of "tandem" systems where an appropriate spectrometer is coupled directly to the chromatograph which provides spectra of each eluted solute. Such combinations can provide unambiguous solute identification and many systems are commercially available but can be rather expensive. Tandem systems will be discussed in a subsequent chapter. A less sophisticated solution is to use a diode array UV
absorption detector to provide UV spectra of each solute or to employ a series of different detectors in sequence, each monitoring a different physical or chemical property of the eluent. The former has limitations due to the restricted information provided by most UV spectra and, unfortunately, the latter can cause serious peak dispersion that may arise in the extensive connecting tubing that is necessary and also in each sensor cell. The latter system, nevertheless, has been used successfully for solute identification (6) where the chromatographic resolution is sufficient to tolerate the inevitable extracolumn dispersion that will occur. However, excess chromatographic resolution is not normally available, and thus the dispersion arising from the connection of a number of detectors in series or parallel is usually unacceptable and furthermore can also be very expensive.
