Hi everybody.
I was trying to analyse Ivermectin in a pharmaceutical product, but when I ran the standard it does not appear any peak (I'm using the USP 39 method for ivermectin).
I tried to modify the column and the mobile phase but it didn't appear anyway.
So I decide to check if the ivermectine was disolving correctly in methanol by analysing its UV spectrum and I found that there was no the expected spectrum, instead I got a weird signal (I have attached a photo).
So my question is: could it mean that the standard has degraded? or probably it could be a UV lamp problem?
By the way, the sample looked like it has the ivermectin compared to other analysis from months ago (obviously I cannot be sure unless I compare it with the standar).
It may be that your lamp died. When was the last time it was replaced?
The lamp is stily in its life time. If you can notice, the blank (Methanol) gives a expected spectrum (210nm), but the ivermectin gives a noise-like spectrum. The concentration was 1mg/mL, today I'm going to try to read it at a lower concentration.
Yes. Your concentration is far too high. Absorbance > 3 is not valid at all. The strange peaks may be noise of the detector. Your spectrum needs to be below 2, better around 1. By the way, your methanol seems to be too dirty. You need a UV or HPLC grade quality. The signal of methanol should be very low in your wavelength range.
I ran the ivermectin at 0.04mg/mL and the spectrum went very well. I will keep the advice of not to pass the 2. Also I changed the solvent used (I looked like the bottle somehow had contaminated even being HPLC grade) and the peak at least appear. Thank you very much for your help. I appreciate it too much.
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