Determination of five beta-blockers in wastewaters by coupled-column liquid chromatography and fluorescence detection

A simple multidimensional system for direct injection of large volumes has been developed for the determination of five beta-blockers (atenolol, nadolol, metoprolol, bisoprolol and betaxolol) in wastewater using fluorescence detection. A C18 50 mm × 4.6 mm i.d. column coupled to a RP Amide C16 150 mm × 4.6 mm i.d. column for analyte clean-up and determination were used, respectively. The capability of a first column for eliminating large, interfering molecules, combined with an optimised, coupled-column liquid chromatography separation procedure (LC-LC), large volume injection (LVI) and fluorescence detection (FD), gave excellent sensitivity and selectivity for the target analytes. The LVI-LC-LC-FD method combines analyte isolation, preconcentration and determination into a single step. Detection limits obtained in wastewater were lower than, or equal to, 0.0020 μg L−1. Limits of quantification (LOQs) obtained in the matrix according to IUPAC, ranged between 0.0052 and 0.0089 μg L−1, whereas LOQs calculated according to EURACHEM Guidance, varied between 0.4 and 0.6 μg L−1. Accuracy values ranged from 82 to 107% (n = 3) and relative standard deviation (RSD) values ranged from 0.8 to 9%. The LVI-LC-LC-FD method was applied for determining the target analytes in wastewater samples obtained in Almería (Spain).