Novel Potentiometric Sensors Based on Multiwalled Carbon Nanotubes and $\beta$ -Cyclodextrin for Determination of Antipsychotic Sulpiride: Electrochemical and Surface Morphology Studies

In this approach, two novel modified carbon paste sensors were assembled for potentiometric assay of sulpiride (SLP). One sensor is based on the ion pair of SLP-phosphotungstic acid and incorporation with multiwalled carbon nanotubes (MWCNTs) called MWCPE and the second sensor based on β-cyclodextrin (β-CD) ionophore and sodium tetraphenylborate as anionic site additive called $\beta $ -CDCPE. Dibutyl phthalate was added as plasticizer. The characteristics of the suggested sensors showed responses in terms of Nernstian slopes 59 ± 0.7 and 59.5 ± 0.3 mV decade
^-1
in wide linear ranges from 1×10
^-6
to -1×10
^-2
mol·L
^-1
and from 1×10
^-5
to -1×10
^-2
mol·L
^-1
with low detection limits 3.5×10
^-7
and 5×10
^-6
mol·L
^-1
with very short response time 5 and 10 s and exhibit adequate operational long lifetime (22 and 17 weeks) for MWCPE and β-CDCPE, respectively. Both sensors response were pH independent in the range of 2-8 at 25 °C. For studying the ion-to-electron transducing ability of MWCNTs and β-CD on the sensor surface, the electrochemical impedance spectroscopy measurements were done. Scanning electron microscope and transmission electron microscope were used for studying the surface morphology of MWCPE sensor. The sensors showed adequate selectivity for SLP with respect to a large number of interfering species. Moreover, SLP ions were successfully determined in pure state, pharmaceutical preparations, and human urine with high accuracy and precision using these sensors.