Liquid Chromatography Detectors - Transport Detectors > The Modified Moving Wire Detector > Page 68


Figure 44  The Separation of Blood Liquids Employing Incremental Gradient Elution and Monitored by the Modified Moving Wire Detector

However, due to the limited number of compounds that were tested this relationship should be assumed only with caution. A chromatogram of blood lipids obtained by incremental gradient elution and monitored by the modified detector is shown in figure 44. As incremental gradient elution involves a program of 12 solvents ranging from hydrocarbons, chlorinated hydrocarbons, nitro-paraffins, esters, ketones and alcohols. This separation illustrates the versatility that is provided by this detector for solvent selection.

Van Dijk (37), attempted to improve the sensitivity of the detector by using a spray procedure for coating the wire. The column eluent entered an atomizer and spray from the nozzle was directed onto the wire. The spray partly concentrated the solute by evaporation and also increase the load on the wire. A linear dynamic range of about 3 x 103 was claimed for the system and a sensitivity increase of 50 over the original wire transport detector (probably about 3 x 10-6 g/ml).

Yang et al. (38) also used a thermal spray for coating the wire and also claimed an increased sensitivity. A heated chamber (through which the conduit from the column passed) was placed above a moving stainless steel belt. The solvent was rapidly brought to its boiling point resulting in spray leaving the exit of the conduit and coating the belt. Yang et al. also employed a photo-ionization detector and an electron capture detector as alternatives to the FID.