Waters CORTECS - Page 5

5CORTECS and CORTECS Premier 2.7 µm Columns
[ CARE AND USE MANUAL ]
Table 2. Buffer Recommendations for Using CORTECS Columns
Additive/Buffer pK
a
Buffer
Range
Volatility
(±1 pH Unit)
Used for
Mass
Spec
Comments
TFA 0.3 — Volatile Yes
Ion pair additive, can suppress MS signal,
used in the 0.02–0.1% range.
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
3
CO
2
) 4.76 3.76–5.76 Volatile Yes
Used in the 1–10 mM range.
Note: Sodium or potassium salts are not volatile.
Formate (NH
4
HCO
2
) 3.75 2.75–4.75 Volatile Yes
Used in the 1–10 mM range.
Note: Sodium or potassium salts are not volatile.
Phosphate 1 2.15 1.15–3.15 Non-volatile No Traditional low pH buffer, good UV transparency.
Phosphate 2 7.2 6.20–8.20 Non-volatile No
Above pH 7, reduce temperature/concentration
and use a guard column to maximize lifetime.
Phosphate 3 12.3 11.3–13.3 Non-volatile No
Above pH 7, reduce temperature/concentration
and use a guard column to maximize lifetime.
4-Methylmorpholine ~8.4 7.4–9.4 Volatile Yes Generally used at 10 mM or less.
Ammonia (NH
4
OH)
Ammonium
bicarbonate
9.2
10.3 (HCO
3
-
)
9.2 (NH
4
+
)
8.2–10.2
8.2–11.3
Volatile
Volatile
Yes
Yes
Used in the 5–10 mM range (for MS work keep
source >150 ˚C). Adjust pH with ammonium
hydroxide or acetic acid. Good buffering
capacity at pH 10.
Note: Use ammonium bicarbonate (NH
4
HCO
3
),
not ammonium carbonate ((NH
4
)
2
CO
3
).
Ammonium (Acetate) 9.2 8.2–10.2 Volatile Yes Used in the 1–10 mM range.
Ammonium (Formate) 9.2 8.2–10.2 Volatile Yes Used in the 1–10 mM range.
Borate 9.2 8.2–10.2 Non-volatile No
Reduce temperature/concentration and use a
guard column to maximize lifetime.
CAPSO 9.7 8.7–10.7 Non-volatile No
Zwitterionic buffer, compatible with acetonitrile,
used in the 1–10 mM range. Low odor.
Glycine 2.4, 9.8 8.8–10.8 Non-volatile No
Zwitterionic buffer, can give longer
lifetimes than borate buffer.
1-Methylpiperidine 10.2 9.3–11.3 Volatile Yes Used in the 1–10 mM range.
CAPS 10.4 9.5–11.5 Non-volatile No
Zwitterionic buffer, compatible with acetonitrile,
used in the 1–10 mM range. Low odor.
Triethylamine
(as acetate salt)
10.7 9.7–11.7 Volatile Yes
Used in the 0.1-1.0% range. Volatile only when
titrated with acetic acid (not hydrochloric
or phosphoric). Used as ion-pair for DNA
analysis at pH 7–9.
Pyrrolidine 11.3 10.3–12.3 Volatile Yes Mild buffer, gives long lifetime.
Note: Working at the extremes of pH, temperature, and/or pressure will result in shorter column lifetimes.