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 (0.1 mol L⁻¹, pH 5.5). At the above experimental conditions, calibration curve (E vs. log [ATR]) was linear (R² = 0.9977) in the concentration range of 1.0 × 10⁻⁹–1.0 × 10⁻³ mol L⁻¹ (0.0012–1209 mg L⁻¹) of ATR with a Nernstian slope of 58.14 ± 0.2 mV decade⁻¹, and detection limit of 1.0 × 10⁻⁹ mol L⁻¹ (0.0013 mg L⁻¹). After each injection of ATR to the buffer solution, the potential was stabilized in a very short time (average response time ~ 6 s) at 25 °C. The modified graphite paste electrode had a long lifetime (> 4 months). 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 40 mg per tablets, respectively. Finally, the electrode was used in potentiometric titration of ATR (1.0 × 10⁻³ mol L⁻¹) by CTAB (1.0 × 10⁻³ mol L⁻¹). Excellent accuracy (≈ 100%) was obtained from the volume of the titrant at the endpoint. - Graphical abstract: Graphite paste was modified with atorvastatin-CTAB (ATR-CTAB), ionic liquid (BMIMPF₆) and multiwalled carbon nanotubes (MWCNTs). It was used in potentiometric analysis of nanomolar concentrations of atorvastatin in different samples. The method had one of the lowest limits of detection (LOD) among the methods reported for the drug analysis. Excellent reproducibility and accuracy was obtained in complex matrices such as blood serum and urine. - Highlights: • Atorvastatin was determined by a potentiometric method. • A modified graphite paste electrode was constructed. • A wide linear concentration range was obtained (6 orders of magnitude). • Detection limit was 1 nM of atorvastatin. • Atorvastatin was determined in human blood serum and urine.