Extra Column Dispersion - Chromatographic Apparatus for Trace Analysis > Page 59
Chromatographs with high mass sensitivity have been used extensively in trace analysis in pollution studies, toxicity monitoring, water analysis and in clinical testing. However, even with high mass sensitivity instrumentation, concentration devices are often necessary to monitor extremely low sample solute concentrations. Sample concentration can sometimes be carried out on the analytical column itself, but it is usually more effective to employ specific ancillary equipment. It should be noted that on-column concentration can not be used if there are substance present in the sample which will be retained on the column and eventually degrade its performance (e.g., blood cells in a blood sample, or foreign proteins that will precipitate in the solvent). An apparatus for concentrating sample of biological origin is shown in figure 29 (14).
Figure 29. Sample Concentration Apparatus for Sample of Biological Origin