Primesep columns from SIELC
Primesep columns are highly versatile. Where traditional stationary phase design worked to minimize "unwanted" secondary interactions, SIELC's SWITCH Phase® Technology precisely controls the type and strength of those interactions to offer unparalleled selectivity.
Primesep 100 (4.6 × 150 mm)
- Flow:
- 1.0 mL/min
- Detection:
- UV 250 nm
- Mobile phase:
- MeCN 15%, H₂SO₄ 0.15%
Primesep C (4.6 × 50 mm)
- Flow:
- 1.0 mL/min
- Detection:
- ELSD
- Mobile phase:
- MeOH / NH₄ acetate, 60/40, 20 mM, pH 5.0
Primesep SB (3.0 × 50 mm)
- Flow:
- 0.5 mL/min
- Detection:
- UV 270, 325 nm
- Mobile phase:
- MeCN gradient 50–80% in 5 min, 5 min hold, AcOH 0.1
Mixed-mode stationary phases
A stationary phase that provides more than one strong, controllable mode of interaction is a mixed-mode stationary phase, and this is where Primesep columns get their versatility.
A good reverse-phase column typically has only one mode of selection: hydrophobic interaction. That limits its usefulness. Polar compounds are hard to retain, closely related compounds are hard to separate, and samples with compounds of very different polarity need long analysis times.
Primesep columns offer several modes of interaction depending on the functional group attached to the stationary phase. Four of the most common are shown below.
SWITCH Phase® Technology
SWITCH Phase® Technology gives even greater control over selectivity. Every functional group in the Primesep range has its own pKa, so it can be ionized or non-ionized depending on the pH of the mobile phase.
If the mobile phase pH is close to or above the transition value of the Primesep C functional group, the column works as a mixed-mode ion-exchange and reverse-phase column. Below that value, it works as a reverse-phase column with a non-ionized functional group.
| Cation exchange column | pKa of embedded carboxylic acid | Basic compounds separated |
|---|---|---|
| Primesep 500 | 5.0 | Strong bases, metals |
| Primesep C | 3.5 | Strong bases, dibases |
| Primesep 200 | 2.0 | Strong bases, dibases |
| Primesep 100 | 1.0 | Weak and medium bases, amino acids, metals |
| Primesep A | 0 | Weak bases, amino acids, metals |
For example, the same Primesep C column separates caffeine, benzylamine and phenol differently either side of its transition point:
pH above Primesep C transition point
- Column:
- Primesep C (4.6 × 150 mm)
- Flow:
- 1.0 mL/min
- Detection:
- UV 210 nm
- Mobile phase:
- Water/MeCN 60/40, ammonium acetate 20 mM, pH 5.0
pH below Primesep C transition point
- Column:
- Primesep C (4.6 × 150 mm)
- Flow:
- 1.0 mL/min
- Detection:
- UV 210 nm
- Mobile phase:
- Water/MeCN/TFA 60/40/0.1, pH 2.0