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The objective of this thesis is the quantification and qualification of neonicotinoid insecticides using thin-layer chromatography (TLC). Neonicotinoids are a relatively new form of pesticides, which have been proven to be extremely lethal to the honey bee, Apis mellifera. In this paper six forms of neonicotinoid insecticides (i.e. Acetamiprid, Thiacloprid, Imidacloprid, Clothianidin, Thaimethoxam, and Nitenpyram) are analysed. The initial steps are to first find a suitable mobile phase eluent, followed by the search for a reagent causing a luminescence effect of the neonicotinoids on a TLC plate. Subsequently, a calibration method is then used to find the detection limit of this TLC experiment. The aim is, therefore, to achieve a standard method of quantifying and qualifying neonicotinoids via TLC. Whilst a suitable mobile phase has been established, an optimal fluorescent reagent has yet to be found and more research on the subject must be carried out.
Limits of quantification of some neonicotinoid insecticides measured by thin-layer chromatography
(2012)
A simple method to quantify the neonicotinoid insecticides nitenpyram, thiamethoxam, acetamiprid, imidacloprid, thiacloprid and clothianidin directly on an HPTLC-plate is presented. As stationary phase silica gel 60 RP-18WF254 s plates were used and a mixture of methyl-t-butyl ether, 2-butanone, NH3 (25%) (5 + 2+0.1, v/v) was used as solvent. All neonicotinoid insecticides show light absorptions below 300 nm. The calculated limits of quantification (LOQ) by UV-detection are in the range from 12 ng to 26 ng on plate depending on the different insecticides.Nitenpyram can be stained using fast blue salt B, forming red zones. The observed LOQ is 25 ng on plate. Acetamiprid can be specifically stained using phenylglyoxylic acid forming a yellow/green fluorescent compound. The LOQ is 52 ng per spot.The compounds thiamethoxam, acetamiprid, thiacloprid and clothianidin can be transformed into blue fluorescing zones, using a relatively new staining solution. This consists of tetraphenylborate and HCl. This is the first publication mentioning that neonicotinoids undergo this reaction. The calculated limits of quantification are in the range from 10 ng to 27 ng on plate.A simple pre-treatment procedure using an acetonitrile extraction and a Chromabond SiOH clean up procedure leads to overall LOQs for bee samples of 48 to 108 µg/Kg. The method can be used to measure neonicotinoid contaminations of bees.