Introduction to Modern Liquid Chromatography || Appendix I: Properties of HPLC Solvents

✍ Scribed by Snyder, Lloyd R.; Kirkland, Joseph J.; Dolan, John W.

• Book ID: 101396906
• Publisher: John Wiley & Sons, Inc.
• Year: 2009
• Tongue: English
• Weight: 489 KB
• Edition: 3
• Category: Article
• ISBN: 0470167548
• DOI: 10.1002/9780470508183.app1

✦ Synopsis

PROPERTIES OF HPLC SOLVENTS

S olvents are used in HPLC for formulating mobile phases, for dissolving the sample, and for carrying out sample preparation. Mobile-phase solvents are of primary concern, because their properties must often fall within narrow limits for acceptable performance. However, these same properties also influence the choice of the sample-injection solvent and solvents used for sample preparation. Table .1 lists several solvent properties that can be important when selecting solvents for an HPLC application. Some of these properties have been discussed previously in one or more sections of this book (second column of Table .1). The present appendix contains several tables that list values of one or more solvent properties (third column of Table .1). A brief comment on each solvent property is given in the last column of Table .1; this serves as an introduction to following sections that deal with individual solvent properties.

I.1 SOLVENT-DETECTOR COMPATIBILITY

I.1.1 UV Detection

The mobile phase will preferably have an absorbance A < 0.2 AU at the wavelength used for detection of the sample; a lower absorbance may mean improved assay precision and better results with gradient elution, but higher absorbances may be acceptable for some isocratic separations. Table .2 summarizes values of solvent absorbance at different wavelengths (200-260 nm) for solvents that are used for RPC (exclusive of NARP). Very rarely, there may be a reason to use UV detection at a wavelength <200 nm, for the detection of solutes with low absorptivity at higher wavelengths.

Because water does not absorb at 200 nm or above, the absorbance of aqueous mobile phases that contain these solvents will equal the pure-solvent absorbance times the volume-fraction φ of the B-solvent in the mobile phase. For example, a mobile phase of 25% B would have the following absorbance values A for different B-solvents at 215 nm: ACN, 0.00 AU; MeOH, 0.09 AU; degassed MeOH, 0.05 AU; THF, 0.22 AU; IPA, 0.07 AU. Note that degassing methanol lowers the