Methyl anthraquinone, effect retention

The effect of temperature, and of temperature and pH on the retention of a selected group of compounds using a beta-cyclodextrin column was studied. The results indicated that a plot of Ink vs. 1/T gave linear relationships for anthraquinone, methyl anthraquinone, ethyl anthraquinone, naphthalene and biphenyl using a mobile phase of methanol/water. However, a non linear relationship was observed for a selected group of dipeptides employing a mobile phase of methanol/ammonium acetate at the following pH s 1, 5.5 and 7. The retention times decreased with an increase in the temperature of the column except that for certain dipeptides the retention times increased. The separation factor (a) values decreased by approximately 10 with increase in column temperature from 25°C to 77°C. 

EFFECT OF METHANOL IN THE ELUENT ON RETENTION. The effect of increasing the volume of the organic modifier, methanol, in the mobile phase on the retention of methyl anthraquinone and naphthalene is given in Figure i(. Methyl anthraquinone and napthalene are more soluble in methanol than in water so increasing the volume of methanol in the mobile phase should result in the increase in the solubility of both compounds, and as a result, a decrease in the retention time. Also, the presence of methanol in the mobile phase affects retention when cyclodextrin bonded columns are used. Methanol is much more tightly bound in the cyclodextrin cavity than... 

Figure Effect of volume of methanol in the eluent on the retention times of methyl anthraquinone (-0-) and naphthalene (-0-) using a B-cyclodextrin column, 4,6 x 100 mm, and a flow rate of 1 ml/min.

The effect of change in column temperature on the retention of anthraquinone, methyl- and ethylanthraquinones between 25°C and 55°C was a decrease of 75, 76 and 77 respectively. 

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