Extra Column Dispersion - Chromatographic Apparatus for Trace Analysis > Page 61
The sensitivity of the total system was determined in the following manner, using very dilute solutions of acetophenone in water. Sample containing 1 ppm, 100 ppb, 10 ppb and 1 ppb were drawn into the open loop and the solute adsorbed on the packed loop. The results obtained are shown in figure 30. It is seen that the blank sample is quite clear and free from any peaks and the peak for acetophenone present a level of 1 ppm is completely off scale. The limit of detection appears to be about 10 ng which is equivalent to a 1 ml sample with a concentration of 10 ppb or a 10 ml sample having a concentration of 1 ppb. It is seen that the two peaks representing 10 ng of solute are roughly the same size although derived from two samples having and order of magnitude difference in concentration. This indicates that the extraction efficiency is very satisfactory for this type of work. The type of sampling system can also be used for blood analysis by direct sampling of blood or alternative blood serum.
The column length was 50 cm, the column I.D. 1 mm, the packing ODS-2 10 mm, the solvent 75% v/v methanol/25% v/v water at a flow rate of 40 ml/min.
Figure 30. Chromatograms Demonstrating the Sensitivity of the Microbore Column and Sampling System