Chromatography
Gel Permeation / Size-Exclusion Chromatography (GPC / SEC)
Separates molecules by their size in solution rather than by chemistry, so large molecules elute first. Used for polymer molecular-weight distribution and for protein aggregates in biologics.
- Pharmaceutical
- Biopharmaceutical
- Polymers & plastics
- Food (polysaccharides)
- Cosmetics
- Chemicals
TROUBLESHOOTING
Common problems, causes and fixes
Molecular weights drifting between runs
Likely causes
- • Flow rate variation
- • Temperature change
- • Column ageing
What to do
- • Verify flow and use a flow marker correction
- • Control column and detector temperature
- • Re-run calibration standards; replace the column if needed
Late-eluting tail or peaks after total permeation
Likely causes
- • Adsorption of sample to the packing
- • Wrong salt concentration or pH
What to do
- • Increase ionic strength or adjust pH as the method allows
- • Use a column with a more inert surface
Unstable RI baseline
Likely causes
- • Reference cell not purged
- • Temperature fluctuation
- • Mobile phase not degassed or changing
What to do
- • Purge the reference cell with fresh mobile phase
- • Stabilise room and detector temperature
- • Degas and use a single mobile-phase batch
Increasing back-pressure
Likely causes
- • Undissolved sample or gel particles
- • Microbial growth in aqueous systems
What to do
- • Filter samples; dissolve more completely
- • Use fresh buffer with an antimicrobial agent for storage
Unexpected aggregate peak in protein samples
Likely causes
- • Sample handling (shaking, freeze–thaw)
- • Carry-over from a previous sample
What to do
- • Handle samples gently and as per stability data
- • Run blanks and clean the injector
In LimsPulse · Calibration Management
Keep every GPC / SEC in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.