Waters iKey - Manual (Page 7)

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[ CARE AND USE MANUAL ]
iKey
b. Mobile Phases
To maintain and ensure maximum iKey performance, use high quality chromatography solvents. Use only filtered and degassed mobile
phases. Filter all aqueous buffers prior to use through a 0.2 μm filter. Solvents containing suspended particulate materials will generally
clog the iKey ceramic substrate (analogous to clogging the inlet frit of an LC column). This may result in higher backpressure or distorted
peak shape. A table of recommended buffers is listed below:
Additive/Buffer pKa Buffer Range
Volatility (±1
pH unit)
Used for
Mass Spec
Comments
Acetic Acid 4.76 Volatile Yes
Maximum buffering obtained when used with
ammonium acetate salt. Used in 0.1–1.0% range.
Formic Acid 3.75 Volatile Yes
Maximum buffering obtained when used with
ammonium formate salt. Used in 0.1–1.0% range.
Acetate
(NH
4
CH
2
COOH)
4.76 3.76 – 5.76 Volatile Yes
Used in the 1–10 mM range. Note that sodium or
potassium salts are not volatile.
Formate
(NH
4
COOH)
3.75 2.75 – 4.75 Volatile Yes
Used in the 1–10 mM range. Note that sodium or
potassium salts are not volatile.
Additionally, the iKey lifetime will vary depending upon the operative temperature and pressure as well the type and concentration of
additive/buffer used.
c. pH Range
The recommended operating range for iKey is 1 to 7.
d. Pressure
iKeys can be operated at pressures up to 10000 psi (690 bar). Infusion and flow injection iKeys can be operated at at pressures up to
8000 psi (550 bar).
e. Temperature
Temperatures can be used to enhance selectivity, lower solvent viscosity, and increase mass transfer rates. When operating near the upper
pH limit for iKey, lower temperatures are recommended for higher iKey lifetime. iKey temperature limits are shown below:
Component Description
Ethylene bridged hybrid (BEH) 90 °C
Charged surface hybrid (CSH) 80 °C
High strength silica (HSS) 45 °C
Note: Working in combinations of extreme pH, temperature and pressure may result in reduced iKey lifetime.