Analysis of β-blockers in groundwater using large-volume injection coupled-column reversed-phase liquid chromatography with fluorescence detection and liquid chromatography time-of-flight mass spectrometry

Abstract

Atenolol, nadolol, metoprolol, bisoprolol and betaxolol were simultaneously determined in groundwater samples by large-volume injection coupled-column reversed-phase liquid chromatography with fluorescence detection (LVI-LC-LC-FD) and liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS). The LVI-LC-LC-FD method combines analyte isolation, preconcentration and determination into a single step. Significant reductions in costs for sample pre-treatment (solvent and solid phases for clean up) and method development times are also achieved. Using LC-TOF-MS, accurate mass measurements within 3 ppm error were obtained for all of the β-blockers studied. Empirical formula information can be obtained by this method, allowing the unequivocal identification of the target compounds in the samples. To increase the sensitivity, a solid-phase extraction step with Oasis MCX cartridge was carried out yielding recoveries of 79-114% (n=5) with RSD 2-7% for the LC-TOF-MS method. SPE gives a high purification of β-blockers compared with the existing methods. A 100% methanol wash was allowed for these compounds with no loss of analytes. Limit of quantification was 1-7 ng/L for LVI-LC-LC-FD and 0.25-5 ng/L for LC-TOF-MS. As a result of selective extraction and effective removal of coextractives, no matrix effect was observed in LVI-LC-LC-FD and LC-TOF-MS analyses. The methods were applied to detect and quantify β-blockers in groundwater samples of Almería (Spain).

Keywords: Coupled columns; Groundwater; LC; TOF-MS; β-Blockers.