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How to improve chromatographic performance using ultrapure water
The purity of the solvent used for the mobile phase is one of many factors affecting the quality of chromatographic data obtained from high-performance liquid chromatography (HPLC). A typical reversed-phase HPLC gradient elution requires equilibration of the column to the initial conditions with several column volumes of the weak (aqueous) solvent. Organic contaminants in the aqueous solvent will adsorb at the head of the column and can cause interferences in the succeeding chromatograms, such as massive baseline shifts and the appearance of extraneous peaks. This study illustrates how two different sources of water used as solvent in the gradient elution of a drug mixture affect chromatographic performance over time. The solvents being compared are commercially available HPLC-grade bottled water without total oxidizable carbon (TOC) specifications and freshly delivered ultrapure water with a TOC level of 05 ppb. Comparing the chromatograms of preconcentrated water by analytical HPLC shows that bottled HPLC-grade water contains many more organic solutes than does freshly delivered ultrapure water, suggesting that these contaminating solutes can contribute to baseline variability and poor chromatographic performance when bottled water is used as a mobile phase in HPLC separations.