Dispersive solid-phase extraction using multi-walled carbon nanotubes combined with liquid chromatography-mass spectrometry for the analysis of β-blockers: Experimental and theoretical studies

This manuscript presents a dispersive solid phase extraction (dSPE) method combined with liquid chromatography mass spectrometry (LC-MS/MS) to simultaneous determination and quantification of six beta-blockers in environmental water samples. The proposed method is based on a multi-walled carbon nanotubes (MWCNTs) as a sorbent, because of their remarkable sorption capacity. Crucial parameters which may affect extraction efficiency such as type and quantity of suitable sorbent, pH of sample solution and composition and volume of elution solvent were optimized. It was observed that the sorption efficiency of propranolol and acebutolol does not depend on the outer diameter of the carbon nanotube (CNTs). On the other hand, the lower sorption potential of atenolol and nadolol was clearly noticeable for CNTs with a larger outer diameter. To explain the observed differences in the sorption affinity depending on the outer diameter of the CNTs, a quantum-mechanical study for all beta-blocker structures was performed. Finally, it was considered that CNTs with outer diameter < 8 nm, in 10 min were an effective sorbent for all tested compounds. Analytes retained on CNTs surface were desorbed with use 10 mL of mixture containing ACN:ethyl acetate (1:1) (v/v) + 15% NH4OH. Under the selected conditions the recovery values were in the range between 67 and 93%. Quantitation limits of the method (LOQ) of dSPE-LC-MS/MS method were 0.005 mu g L-1 for deionized water matrix and 0.05 mu g L-1 for environmental water. The suitability of the optimized methodology for the extraction of six beta-blockers from environmental water samples was performed.