Column-switching linked to large sample volumes to preconcentrate β-blockers at trace levels in environmental water

This paper describes about an automated on-line enrichment method for the simultaneous determination of seven β-blockers in river water using a short liquid chromatography column for preconcentration coupled with LC-DAD. The method performs the preconcentration of 30 mL of river water samples (5% organic modifier) using a 50 mm × 4.6 mm C18 column for enrichment and a 150 mm × 4.6 mm C18 column for separation, allowing the determination of β-blockers at trace levels in river water. The analytical procedure was developed by optimizing the breakthrough parameters (flow rate, time of preconcentration and percentage of organic modifier added to the sample) in order to achieve the maximum sensitivity, and by optimizing the mobile phase (composition and flow rate) to get adequate separation of the components in a reasonable analysis time. Under the optimized conditions, the method was validated with respect to linearity, precision, limits of detection, limits of quantification and accuracy. Detection and quantitation limits ranged between 0.1 and 3.1 and between 1.0 and 5.0 ng mL−1, respectively, whereas the RSD on inter-day precision was below 8%. e with the matrix effect in the determination of these drugs in river water samples, the standard addition methodology was successfully applied. Recoveries ranging from 81 to 115% proved the accuracy of the methodology proposed in this work.