River water samples were collected from Oued Madjerda (Tunisia).
The analytes of the samples were concentrated one hundred
times by rotary evaporation in accordance with previous study that
indicated the stability of the carbamate at this temperature [21]. Then
the water was filtered through 0.45 μm membrane. Until analysis the
filtered samples were stored in dark glass bottles at 4 °C.
methanol at concentrations ranging from10 ng/mL to 100 ng/mL. Three
SPE C-18 cartridges were used for this study. HPLC-grade methanol,
acetonitrile, and ultra-pure water were obtained from Labscan (Dublin,
Ireland). Formic acid and Ammonium formate were supplied by Sigma
Aldrich