Hi Hassan,  Your objective from the above question is not clear. But  U can feed the insects  with this isotopically labelled glucose, then after a known  time period , U can  treat the insects to kill them , grind / macerate them to get the extract,  centrifuge this extract ,purify this by some separation technique like  column chromatography , collect the fractions ,  evaporate them to get the concentrate  of  the  desired metabolite & then use the Chemical technique to get the C-13 NMR scan etc.  Dr Abid Aziz Ajaz. 

Thanks Dr Abid Aziz Ajaz for your answer, which solvent can I using  for make extract. I will use HPLC in my analysis.

Regards,