Analysis of microcontaminants in aqueous samples by fully automated on-line solid-phase extraction-gas chromatography-mass selective detection.

The trace-level analysis of unknown organic pollutants in water requires the use of fast and sensitive methods which also provide structural information. In the present study, an on-line technique was used which combines sample preparation by means of solid-phase extraction (SPE) on a small precolumn packed with a hydrophobic phase, and capillary gas chromatography (GC) with mass spectrometric (MS) detection. Sample preparation was carried out in a fully automated SPE module which was connected to the GC system via an on-column interface. The on-column interface was selected because of its wide application range. The mass spectrometer was preferably used in the full-scan acquisition mode because of the intended identification. The total system including the SPE module, was controlled by the MS software which allowed unattended analysis of a series of samples. The feasibility of on-line SPE-GC-MS was demonstrated by analysing a variety of surface water samples in order to detect and identify non-target compounds. With a sample volume of only 10 ml various micropollutants could be identified, and also quantified, at levels below 0.1 μg/l. The system proved to be flexible, and the sample preparation could easily be adapted to analyse organochlorine pesticides by adding 30 vol.% of methanol to the raw sample. Samples were taken from several European (Aries, Greece; Ebro, Spain; Meuse, Netherlands; Nitra, Slovakia; Rhine, Germany; Thames, UK; Varta, Poland) and American (Sacramento, USA; Amazon, Brazil) rivers. An example of the identification of unknown microcontaminants in waste water is also presented, which is further evidence of the robustness and flexibility of the SPE-GC-MS analyzer.