IUPAC names and chemical formula of the pesticides studied CompoundFormulaIUPAC
3.2.2. Extraction temperature
HS-SPME approach is a result of the balance the equilibrium between sample and headspace and between the headspace and the fiber. Extraction temperature affects these equilibria because it increases the Henry’s constant and vapor pressure of the analyte. So, it increases the concentration of the analyte in headspace. On the other hand, the temperature decreases distribution constant because adsorption is an Dinaciclib process. Hence, the effect of temperature was investigated, varying from 20 to 60 °C. As illustrated in Fig. 1b, the extraction ability for the both analytes was increased with increasing temperature from 20 to 50 °C. Thus, the extraction temperature of 50 °C was selected as the best temperature for subsequent analyses.
3.2.3. Salt effect
Addition of a certain amount of salt can decrease the solubility of the analytes in the aqueous sample and enhance the distribution constant of compounds between the aqueous phase and the headspace. Salt effect was evaluated in the NaCl concentration in range from 0 to 3 mol L−1. Fig. 1c shows base extraction efficiency increases with increasing the concentration of NaCl and then reaches a maximum in the presence of 2 mol L−1 NaCl and remains constant. The results indicate that addition of salt has a significant effect on extraction of both analytes. Thus, further analysis was carried out in 2 mol L−1 NaCl.