Page 275 - Tandem Techniques

Page 259

observed. This rectangular shaped curve unambiguously confirms the purity of the chlorthalidone peak.
It should be pointed out that, to improve the confidence limits of purity assurance, the wavelengths
chosen to provide the confirming ratio should be based on the UV adsorption characteristics of the
substance concerned, relative to those of the most likely impurities to be present,

The chlorthalidone was isolated from a sample of
tablets and separated by a (C 18) reverse phase
on a column, 4.6 mm I.D., 3.3 cm long, using a
solvent mixture consisting of 35% methanol,
65% aqueous acetic acid solution (water containing
1% of acetic acid). The flow rate was 2 ml/min.
Figure 7.2
Dual Channel Plot from a Diode Array
Detector Confirming Peak Purity
Courtesy of the Perkin Elmer Corporation
Perhaps a more practical example of the use of the diode array detector to confirm the integrity of an
eluted peak, is afforded by the separation of the series of hydrocarbons shown in Figure 7.3. This
separation illustrates the results that are obtained when an impure peak is identified. It is seen that the
separation appears to be satisfactory and all the peaks represent