Peak compression in linear gradient elution liquid chromatography.

ABSTRACT

An expression for peak compression factor based on temporal peak widths is proposed which can be measured directly. The relationship between it and peak compression factor based on spatial peak widths is given. The experimental data presented in the Neue's work are reevaluated. The peak compression factor is recalculated by taking into account the curvature in the plot of logarithmic retention factor (lnk) vs. mobile phase composition (φ) and the variation in plate height (H) with φ. The lnk vs. φ plot is accounted for by quadratic solvent strength model (QSSM). The lnH vs. φ plot is accounted for by QSSM and a quadratic equation that accounts for the plot of logarithmic peak width obtained under isocratic elution (lnWI) vs. φ. By taking these two factors into account, the discrepancy between experimental and predicted values of peak width is reduced. This result confirms the Neue's conclusion that the anomalous peak broadening reported previously may be an artifact of the procedure to determine the theoretical value of peak width. Moreover, by assuming linear gradient elution, constant column efficiency, and general solvent strength, the relationship between peak compression factors obtained under ideal and real situation respectively is discussed.