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- Posts: 1
- Joined: Tue Oct 06, 2020 7:33 pm
I'm trying to develop a HPLC-FLD method to determine aflatoxins B1, B2, G1 and G2 in peanut butter and animal feed. I'm dealing low recoveries when I analyse CRMs for both matrices (up to 60-70% for B1 and 50% for B2, G1 and G2 are ok) as well as spiked samples that I prepare (things here get worse with 30-40% recoveries for all four).
Regarding sample preparation
1. Weighting 50-150g sample and adding sodium chloride depending on sample weight.
2. Extracting aflatoxins with pure methanol
3. Mixing for 15 minutes in blender and filtering
4. Taking an aliquot of the extract and dilute with water
5. Passing it all through immunoaffinity columns according to suppliers instructions regarding the column. Eluting the aflatoxins with 2 mL of pure methanol and diluting it with water up to 4 mL
6. Ejecting to HPLC
Chromatography is ok I don't have separation problems and calibration plots are ok. Standard solutions are freshly prepared and stock solutions are checked for degradation with uv spectrometer before preparing standard solutions.
I have tried many variations on sample preparation (e.g. extraction with pure acetonitrile and different proportions of methanol/water, blending time, various sample weight, different immunoaffinity columns from various suppliers etc) and the results are the same.
I can't seem to find what the problem is and any help will be greatly appreciated!