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- Posts: 6
- Joined: Mon Jan 22, 2018 5:48 am
Posting in this forum to check if anyone of you could help! I am attempting the European Pharmacopeia method of analysis for assay and related substances of Lactulose (a dissaccharide). The following setup was used:
- Waters System 600-717 Plus-2414 (RID)
- Phenomenax 250 mm x 4.6 mm, 5 micron NH2 Column
- Column and Detector temp: 38C
- Sensitivity: 128
- Mobile Phase: ACN:Buffer(Sodium dihydrogen phosphate) = 80:20 (tried 82:18 too but worse)
- Flow rate: 1.0 ml/min
- Injection vol: 20 microlitre
However, from the chromatograms, I've observed:
- delayed retention time of Lactulose peak
- slight fronting of the lactulose peak
- unable to detect epilactose peak which is crucial for my system suitability of related substance analysis
- baseline noise, making it hard to detect other sugar impurities.
- high assay values (possibly due to merging of some impurities peak??)
Wondering if you guys have any idea on how to solve this. I have monitored the system under purge mode for 10% methanol and my mobile phase for about 30 mins and 1-2 hours respectively but seems like that didn't help much.
I've read that most sugar analysis does not use buffer in the mobile phase composition. Is it true and if so, why?
Your advice are much appreciated!