Reversed-phase liquid chromatography frequently employs such organic solvents as methanol, acetonitrile or tetrahydrofuran. Although HPLC grade products of these types of solvents are available, it seems some users have trouble when using a reagent grade solvent instead of HPLC grade, leading to them wasting considerable amounts of time. How do the two solvent grades differ?
Reagent grade solvents contain larger quantity of impurities absorbing UV than HPLC grade solvents do, which makes it difficult to use them in gradient elution or trace analysis. Especially when detection is conducted in a short wavelength, significant differences appear in baseline noise or detection sensitivity. In some cases (or in some wavelengths) it could be feasible to use a reagent grade solvent but we recommend HPLC grade solvents to obtain a stable chromatogram.
Tetrahydrofuran easily generates peroxides. To compensate for this tendency, it is commonly mixed with antioxidants. The antioxidants cause a ghost peak so a solvent not containing antioxidants should be used in HPLC. The peroxides in tetrahydrofuran also have great impact on the baseline stability (with differences between grades greater than those of other organic solvents), which prompts a strong recommendation to use HPLC grade solvents with very small quantities of impurities.