Extra Column Dispersion - The Determination of Trace Organic Materials in Water > Page 63
The initial solvent was methanol/water (50:50), and the final solvent was pure methanol. A 400 ml sample loop was filed with serum which was displaced by 2 ml of saline into the packed loop. The packed loop was then washed with a further 2 ml of saline, followed by 2 ml of water and then placed in line with solvent programmer. The separation was developed over a period of 100 min.. It is seen that even in the absence of specific drugs or their metabolites the serum contains a large number low molecular weight compounds. It is apparent that if the system is to be used for diagnostic purposes, a more efficient column is necessary to provide improved resolution.
The Determination of Trace Organic Materials in Water
Trace analysis by sample concentration followed by separation on high mass sensitivity chromatographic instrumentation lends itself well to water analysis. The water, in almost any volume, can be pumped through a sample pre column packed with a suitable reverse phase and almost all organic material including organic ions will be extracted efficiently as a sharp band on the front of the sample trap. An example of the use of this procedure in the analysis of different water samples is shown in figure 32.
Column length 50 cm, column diameter 1 mm, packing ODS-2 10 mm, flow rate 40 ml/min., linear gradient over 1 hr from methanol/water (60:40) to pure methanol.
Figure 32. Chromatograms of Water Samples Employing Small Bore Columns in Conjunction with Low Dispersion Instrumentation.