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Softgel sample preparation for HPLC

Question asked by anto on Jun 13, 2019

Hi, I have to analyze curcumin and other actives in softgel of dietary supplements. I've already analyzed them using a small amount of the filler with good results. BTW my boss told me that a small amount of the analyte in the filler could interact with the shell, so I'd like to analyze the entire softgel by solving it in the flask.

As the best extraction solvent for curcumin is methanol, I've done 3 different tests:

1_put 1 softgel in the flask, add 100% methanol and sonicated for 40mins, then fill the flask, filter (0.45um) the sample and analyze with my usual HPLC method

2_put 1 softgel in the flask, add 100% water (to solve the softgel), sonicate for 40 min, fill the flask with water, filter (0.45um) and analyze with the usual method

3_1 ml of the sample prepared in the n.2 diluited in 10 ml of methanol, filter and analyze in hplc

I don't know if this is the right method (I don't want to use enyme extraction, or other kind of solvent, if possible) but I've tried to do as this!


the resuls are quite strange:

1_instead of the awaited 3 spikes I have 3 more spikes with the same UV spectrum

2_good chromatogram but very low area (as I thought, water is not a good extraction for curcumin)

3_good chromatogram but the result of the analysis is too different from the expected





what do you suggest me to analyze softgel capsules??