In-tube solid-phase microextraction-capillary liquid chromatography as a solution for the screening analysis of organophosphorus pesticides in untreated environmental water samples

This paper describes a method for the selective screening of organophosphorus pesticides in water. In-tube solid-phase microextraction (SPME) in an open capillary column coupled to capillary liquid chromatography (LC) with UV detection has been used to effect preconcentration, separation and detection of the analytes in the same assembly. For in-tube SPME two capillary columns of the same length and different internal diameters and coating thicknesses have been tested and compared, a 30 cm × 0.25 mm I.D., 0.25 μm thickness coating column, and a 30 cm × 0.1 mm I.D., 0.1 μm of coating thickness column. In both columns the coating was 95% dimethylpolysiloxane (PDMS)-5% diphenylpolysiloxane. The proposed methodology provided limits of detections (LODs) for the tested organophosphorus pesticides in the 0.1–10 μg/L range, whereas the direct injection of the samples onto the capillary LC system provided LODs in the 50–1000 μg/L range. The sensitivity of the proposed in-tube SPME-capillary LC method is adequate to monitorize the analyte levels in drinking water. Several triazines, polycyclic aromatic hydrocarbons (PAHs), nonylphenol, organochloride pesticides or polybrominated diphenyl ethers (PBDEs) have been evaluated as possible interferents. The reliability of the described method is demonstrated by analysing different real water samples.