*2.3. Sample Analysis*

#### 2.3.1. Neonicotinoid Residues Analysis in Sugar Beet Plants and Soil

The determination of neonicotinoid residues in sugar beet plants and soil was performed by an accredited laboratory by liquid chromatography/tandem mass spectrometry (LC -MS/MS) using acetonitrile extraction and the QuEChERS method (EN 15662: 2008). The limit of quantification (LOQ) for this method is 0.01 mg/kg. The neonicotinoids were extracted from the homogenized sample with acetonitrile. Neonicotinoids, imidacloprid, thiamethoxam, and clothianidin were determined using the LC -MS/MS technique applied to the filtered extract with the Agilent Technologies 6460 Triple Quad LC/MS apparatus. Thiamethoxam is converted to clothianidin in soil and plant tissues, therefore the thiamethoxam residues were determined as the sum of thiamethoxam and clothianidin [30].
