A rapid and simultaneous method for identification and quantification of pesticides residues in water samples
have been developed and applied to the analysis of real samples. Tap and San Francisco River water samples
were collected from Propria town and Aracaju city in the state of Sergipe, Brazil. A new single-drop
microextraction (SDME) followed by gas chromatography–mass spectrometry techniques were used to
determine the dimethoate, methyl parathion, ethion (organophosphates) and permethrin (pyrethroid)
pesticides in water samples. The parameters linearity, linear range, precision, accuracy, sensitivity and
robustness were studied for validation of the SDME/GC–MS method. An important point to this study is that
plots of relative response and logarithmic concentrations were used to verify that the measurements were
within the linear dynamic range of the method. In order to enhance high linearity of analytical curve, points
that do not belong to 95 to 105% of linear range were excluded. Recovery tests of pesticides in different water
samples (tap water and river water) were between 76.2 and 107% and this evaluation was used to
demonstrate the reliability of the method. For all pesticides the method showed the limits of detection (LOD)
in a range between 0.05 and 0.38 μg L−1 and the limit of quantification (LOQ) between 0.15 and 1.1 μg L−1. All
these parameters demonstrate high sensitivity of the developed method and the capability for detecting and
quantifying of low levels of pesticides in water samples.