A Novel Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotubes for Potentiometric Xipamide Determination

Abstract

Solid contact electrodes are widely used in analytical fields due to their outstanding performance over classical ones. However, they showed formation of a water layer affecting stability of those electrodes’ type. Herein, we develop a solid contact ion selective electrode to overcome this common drawback through application of multi-walled carbon nanotubes as a hydrophobic layer between the ion sensing membrane and a glassy carbon electrode. This fine modification improved stability of the electrode via preventing the formation of this water layer. The obtained potential was steady over 30 days with a drift of ∼0.8 mV h−1. The MWCNTs-modified electrode was used for determination of xipamide with a Nernstian slope of −56.01 over a linearity range of 1.0 × 10−5–1.0 × 10−2 mol l−1 and detection limit of 6.0 × 10−6 mol l−1. The proposed sensor was effectively applied for determination of the cited drug in its marketed pharmaceutical dosage form and spiked human plasma.

Two fabricated carbon paste electrodes for novel potentiometric determination of probenecid in dosage form and human plasma

“…pKa value of PRO≈3.5, therefore, it behaves as an anion at pH more than 4.5. Hence, TDAB was chosen as an anion exchanger to be incorporated into ion sensitive membrane cocktail 28 . It is noted that maximum selectivity and sensitivity were attained upon using TDAB in amount equivalent to 5.0 mg. Possible membrane saturation might be responsible for no additional enhancement upon adding larger amounts 1 .…”

“…4 . The potential drift of unmodified CPE is attributed to the replacement of PRO by furosemide leading to alteration in the composition of ions through membrane ions flow 28 .

Figure 4 Water layer test for PEDT-modified CPE and unmodified CPE where potential in (mV) was recorded in (A) 1.0 × 10 −4 mol/L probenecid solution and (B) 1.0 × 10 −2 mol/L furosemide solution.

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Facile fabrication of a portable PANI-NFs/c-MWCNT nano-composite electrochemical sensor for gefitinib: application to human plasma

“…18 This layer works as an electrolyte reservoir that alters the sample composition and destabilizes the standard potential. 18 A hydrophobic electron transducer interlayer such as conducting polymers or carbon nanotubes (CNTs) should be added at this interface to avoid formation of this water layer. Theoretically, SC-ISEs require an electron transducer layer to provide operationally stable potentials.…”

“…23 Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are the main types of CNT. 18 MWCNTs manifest important properties over SWCNTs such as huge surface area, high conductivity, ease of chemical modifiability, and their capacity to accelerate the rate of electron transfer on the electrode surface. Thus, they can be utilized either alone or in a nanocomposite combination in the fabrication of sensors and biosensors.…”

“…[15][16][17] SC-ISEs provide several benets, but there are also some limitations, including issues with reproducibility, membrane stability, and potential dri due to formation of a water layer at the interface between the solid contact surface and membrane. 18 This layer works as an electrolyte reservoir that alters the sample composition and destabilizes the standard potential. 18 A hydrophobic electron transducer interlayer such as conducting polymers or carbon nanotubes (CNTs) should be added at this interface to avoid formation of this water layer.…”