Application of carbon nanotubes-ionic liquid hybrid in a sensitive atorvastatin ion-selective electrode

Atorvastatin (ATR) was determined by a potentiometric method. The ion-pair of ATR and cetyltrimethylammonium bromide (CTAB) was used as a suitable ionophore. A graphite paste electrode was modified with ATR-CTAB ion-pair, multiwalled carbon nanotubes (MWCNTs), and an ionic liquid, 1-butyl-3-mtehyl-imidazolium hexafluorophosphate (BMIMPF6). The amounts of electrode ingredients were optimized (graphite powder: paraffin oil: ATR-CTAB: MWCNTs: BMIMPF6 (58:26:5:8:3 w/w%). Surface characterization was done by using scanning electron microscopy. The potential measurements were recorded at optimized pH by using acetate buffer solution (0.1molL(-1), pH5.5). At the above experimental conditions, calibration curve (E vs. log [ATR]) was linear (R(2)=0.9977) in the concentration range of 1.0×10(-9)-1.0×10(-3)molL(-1) (0.0012-1209mgL(-1)) of ATR with a Nernstian slope of 58.14±0.2mV decade(-1), and detection limit of 1.0×10(-9)molL(-1) (0.0013mgL(-1)). After each injection of ATR to the buffer solution, the potential was stabilized in a very short time (average response time~6s) at 25°C. The modified graphite paste electrode had a long lifetime (>4months). Recovery of the spiked drug to blood serum samples (95.3-98.2%) revealed the reliability of electrode response to ATR. Blood serum samples from consumers were analyzed by the proposed method; the results were comparable with those from HPLC standard method. The potentiometric analysis of ATR tablets by the proposed electrode resulted in a relative error of 0.8% and 1.5% for 20 and 40mg per tablets, respectively. Finally, the electrode was used in potentiometric titration of ATR (1.0×10(-3)molL(-1)) by CTAB (1.0×10(-3)molL(-1)). Excellent accuracy (≈100%) was obtained from the volume of the titrant at the endpoint.