2.3. Analytical procedure

The analytical methods used in environmental monitoring have greatly evolved. Inductively coupled plasma mass spectrometer offers fast multielement capabilities, a high dynamic range, and excellent detection limits in a large number of matrices. It can be used for a variety of aqueous samples like natural waters or environmental samples that can be dissolved [11, 12]. The mass spectrometry with inductively coupled plasma (ICP‐MS) is among the most successful existing methods applied when concentrations of trace and ultra‐trace elements (under ppb) are envisaged [13].

For this work, measurements were performed with a mass spectrometer ICP‐MS model Elan DRC‐e, Perkin Elmer, with the following characteristics: detection limit 0.001–0.01 µg L−<sup>1</sup> ; resolution <0.5 at 10% peak height; abundance sensitivity 1–5 × 10−<sup>7</sup> ; and precision: <2% at 20 min. The performance of an ICP‐MS instrument strongly depends on the operating conditions. Working parameters for plasma were chosen so as to obtain a good compromise between high sensitivity and low oxide levels. The following instrumental parameters of Elan DRC‐e spectrometer were set: 0.92 L min−<sup>1</sup> nebulizer gas flow (NEB); 1.2 L min−<sup>1</sup> auxiliary gas flow (AGF); 15 L min−<sup>1</sup> plasma gas flow (PGF); 1100 W. ICP RF Power; 0.0 quadrupole rod offset; and 70.00 discriminator threshold.
