Comparison of different mass spectrometric techniques combined with liquid chromatography for confirmation of pesticides in environmental water based on the use of identification points.

Three mass spectrometric techniques have been used and compared for the confirmation of the presence of several pesticides that had been detected in environmental water samples by a previously reported SPE-LC-MS/MS screening method. The 2002/657/EC European Comission Decision establishes the need to obtain at least three identification points (IPs) in order to confirm organic residues and contaminants in live animals and animal products. In this paper, a similar approach has been applied for confirmation of pesticides in water samples, using triple quadrupole mass spectrometry (QqQ), time-of-flight mass spectrometry (TOF), and hybrid quadrupole time-of-flight mass spectrometry (QTOF) to achieve the required IPs. The number of IPs collected, the sensitivity, and the practical advantages and disadvantages of these techniques have been discussed. In summary, the QqQ instrument allowed the confirmation of detected pesticides even at very low concentrations (ng/L) achieving between four and five IPs when adding confirmatory transitions. The direct confirmation with a TOF instrument was only feasible for those compounds showing sufficient sensitivity, isotopic pattern, or easy in-source fragmentation. In other cases, the required IPs could be reached by adding IPs earned with this technique to those obtained from the MS/MS screening method. Finally, the use of a QTOF instrument allowed obtaining up to 20 IPs in a single run at relatively high concentrations (submicrograms per liter) as no "ion shopping" was required. Additionally, the application of TOF and QTOF techniques made it possible to detect some nontarget organic contaminants, which were not included in the screening method.