D Eluent Considerations; Introduction; Eluent Quality; Using Buffers Or Thf - Waters 515 HPLC Operator's Manual

Introduction

Eluent quality

Clean eluents are necessary to obtain reproducible results and operate your
HPLC system with minimal instrument maintenance. Dirty eluents can cause
baseline noise and drift and block eluent reservoir and inlet filters with
particulate matter. Always use HPLC-grade, degassed or sparged eluents to
ensure the best possible chromatographic results. Filter eluents through
0.45-µm filters before use.

Using buffers or THF

When you use aqueous buffers, adjust the pH, filter to remove insoluble
material, then blend with organic modifier as appropriate. When you use
unstabilized THF, ensure that your eluent is fresh. Previously opened bottles
of THF contain peroxide contaminants, which cause baseline drift.
Warning:
concentrated or taken to dryness.

Eluent miscibility

Before you change eluents, see the
page D-3 to determine the miscibility of the eluents to be used. When you
change eluents, keep in mind that:
• Changes involving two miscible eluents may be made directly.
• Changes involving two eluents that are not totally miscible (for example,
from chloroform to water), require an intermediate eluent (such as
methanol).
• Temperature affects eluent miscibility. If you are running a
high-temperature application, consider the effect of the higher
temperature on eluent solubility.
• Buffers dissolved in water may precipitate when mixed with organic
eluents.
D-2 Eluent Considerations
THF contaminants (peroxides) are potentially explosive if
table titled "Eluent miscibility" on