Effect of MWCNT as SPE packing material for the separation of chiral emerging contaminants

Abstract

Nowadays the emerging pollutants have a great concern, and between them the most studied are pharmaceutical drugs. These chiral compound often exhibit different effects in pharmacological activity, transport mechanism, metabolism pathway and toxicity. Specifically, β-blockers are sold and administered as a racemic mixture, but the (S) enantiomer is pharmacologically active one. Paradoxically, the (R) enantiomer is the one which has negative and toxic effects. Carboxylated multiwalled carbon nanotubes (cMWCNT) have shown interesting characteristics as enantioselective packing or stationary phase material in separative methods. The aim of this work was develop a method able to separate a racemic mixture of emerging pollutants. The studied analytes were β-blockers (pindolol, propranolol and labetalol) commonly used in the treatment of heart rhythm disorders. We performed a separation procedure using carboxylated and non-carboxylated multiwalled carbon nanotubes (ncMWCNT) as SPE packing material. For the assembly of the columns, 2.7 to 12 mg of MWCNT was weighed and the elution solution was water. On the back of the column a 0.45 μ filter was placed to retain MWCNT. The analytes were determined using an HPLC system with a C18 column and the mobile phase used was Acetinitrilo/NH4HCO3 (50:50), pH 10 with a PDA detector. The results showed that using ncMWCNT there were not separation for any of the studied analytes. In the case of cMWCNT the results for the three studied analytes were different. In the case of labetalol there was not separation, however for propranolol the separation was not so evident, and the result may be improved with some simple changes in the eluent. But, for pindolol the separation was very clear. The preliminary conclusions of the work were that cMWCNT could be an interesting and economic alternative for the separation of chiral drugs. The next step is the molecular study of the interaction the three drugs with the cMWCNT.