thiacloprid

[chimist]

hello
I am a student at master programe. My thesis subject is determination of thiacloprid residues in hazelnut. I have to use HPLC-UV.

I had investigated this subject in internet and I found that BAYER have a methot for this case. at that study,hazelnut is extracted with acetone/water(3/1) but acetone has a UV absorbance at 260 nm, and thiaclopridhas a UV absorbance at 242 nm. Even if I evaporate that acetone there is also found residue acetone in my extract and that acetone has made interference to my thiacloprid. Because of this I cannot use acetone for extraction, and I cannot understand how Bayer can use acetone for extraction?
After that I tried to use acetonitrile/water(3/1) in extraction step, then I applied this exract to chem elut column which is a column used for solid phase extraction. I eluted column with cyclohexane/ethylacetate (1/1) and I evaporated this eluent to dryness. When I dissolved with with mobile phaseI saw that there was no thiacloprid. they were fly. after my pesticide disappeard I try different solvents but I cannot solved the probleme.

subsequently, I tried another technic: and I continued step by step, thus I could found in which step I am losing thiacloprid. and I saw that when I spiked thiaclopid onto hazelnut, thiacloprid is hold on to hazelnut. and I cannot broke the bond between hazelnut and thiacloprid.
please help me
how can I break that bond?

[HW Mueller]

Stick with the Bayer method, if that is not a HPLC method then convert it to one, and/or get rid of all acetone by using azeotropes, for instance: hexane/acetone = 59%/41% , or acetone/pentane = 20/80. (Add a bit more than that % hexane or whatever, then there should be only a trace of the added solvent, if any, left).