žDilution error. Pipette a volume of more than 5 mL, and avoid using volu-

metric flasks of less than 25 mL.

žSonication.Theefficiencyofsonicationishighlyvariableanddepends

on various factors (e.g., condition of the sonication bath, level of water,

and position of flask in the sonication bath). Mechanical shaking is recom-

mended, instead, and is much more reproducible.

žMobile phase as sample solvent. If possible, always use mobile phase as the

sample solvent. This ensures the composition (e.g., percent organic, pH) of

sample solution matches that of mobile phase and reduces the chance of

any problem due to incompatibility of sample solvent and mobile phase.

Alternatively, always use sample solvent weaker than that of the mobile

phase to ensure that the chromatography is not deteriorated. For example,

in reversed-phase HPLC, use less organic solvent in the sample solvent than

in the mobile phase.