The sediment sample was air-dried and sieved. We extracted PEs using DCM in sediment and concentrated the extract to 2 ml. The extract was applied to a glass column filled with neutral alumina and eluted using 30 ml ethyl acetate. But the recovery was very low, less than 40%. Situation in the Lower alkyl chain esters such as DMP and DEP was more serious.
Difficult to say: they
1) either never get dissolved in the first place, to test this use more solvent and repeated extraction.
2) or got lost as they never came from the clean up column or
3) were evaporated during the evaporation processes.
All three is relatively easy to check.
Phtalates have a higher boiling point than DCM so the problem is not the evaporation process. They are easily soluble (which often makes them contaminant) and absolutely non polar compounds so they should not stay on the column.
I have 2 questions : why did you use alumina instead of silica gel ? Did you deactivate alumina ?
How did you sieve the sample ? It is possible that phthalates stay associated to the raw fraction.
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