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- Posts: 2
- Joined: Mon Mar 01, 2021 2:13 pm
I'm using a Shimadzu Prominance LC-20AR HPLC/FLU for ciprofloxacin detection. For stock solution I use Vetranal® ciprofloxacin analytical std. in Methanol (not the HCl form).
My problem is, when I try to measure the calibration points repetitions, the standard deviation of my data is bigger than 15%.
I tried with glass and nylon syringe filter with 2-12-24 ml rinsing volume.
The pH of the stock solution is ~5.6 so 48% of ciprofloxacin is in cationic form and 52% is in Zwitterionic form. My HPLC eluent is pH 2.3 in this pH ciprofloxacin is in cationic form.
(HPLC parameters: A: phosphoric acid pH 2,3, B: ACN; 72:28%; 1ml/min; inj.vol.:20 ul; T:35 °C, detector: ex: 280nm em: 450nm, Teknokroma Brisa C18 column)
Do you have any advice what should I try, to stabilize my measurements, or what could be the problem?
Thank you very much.