Evidence for the Hydration of Some Organic Compounds during Reverse-Phase HPLC Analysis

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Polar analytes can form reversible hydrates with water in reversed-phase HPLC eluents.
• Hydrate formation can influence analyte retention behavior and detection.

Purpose of the Study:

• To investigate methods for detecting hydrate formation of polar analytes during reversed-phase HPLC.
• To evaluate the utility of retention time approximations and spectroscopic parameters for hydrate detection.

Main Methods:

• Recurrent approximation of net retention times with varying eluent organic modifier content.
• Analysis of UV spectroscopic parameters (relative optical densities).
• Calculation of coefficients characterizing the dependence of analyte retention indices on eluent composition (dRI/dC).

Main Results:

• Deviations from linearity in retention time approximations indicate hydrate formation at high water content.
• UV spectroscopic parameters were found to be unreliable indicators of hydrate formation.
• The coefficient dRI/dC proved to be a highly informative criterion for detecting analyte hydration.

Conclusions:

• The dRI/dC coefficient effectively distinguishes between polar analytes that form hydrates and nonpolar compounds.
• Negative dRI/dC values are indicative of hydrate formation in polar analytes.
• This method provides a reliable additional criterion for identifying analyte hydration in HPLC.