On the Influence of Additives and Modifiers on the Chiral HPLC Separation of the Enantiomers of Nicotine

The influence of additives and modifiers on the chiral HPLC separation of the nicotine enantiomers using UV/Vis detection is discussed. Selected alcohols as modifiers and selected amines as additives were found to have a significant effect on the resolution and retention times of nicotine enantiomers even to the point of eliminating component elution. Systematic variations in the concentration of ethanol, methanol, and isopropanol, as modifiers, along with variations in the concentration of diethylamine, triethylamine, tributylamine, ethylenediamine, isopropylamine, as additives, revealed that the average resolution (R) of the nicotine enantiomers ranged from 2.9 to 7.57, using a mobile phase flow rate of 0.80 mL/min. The average retention times of the nicotine enantiomer pairs ranged from 7.64 and 8.34 min to 13.47 and 14.97 min, with the S(-) enantiomer eluting first. As expected, faster flow rates of 1.0 mL/min reduced retention times by approximately 1-2 min, with a slight decrease in the R values. The %RSD values for both resolution and retention times consistently remained below 2%. The detection limits for the enantiomers were approximately 5 μg/mL. The optimized method successfully detected one part in 100 for the minor R(+) enantiomer in the presence of the dominate S(-) enantiomer and adhered to all established QuEChERS method protocols.