Advanced Functionalized CeO2/Al2O3 Nanocomposite Sensor for Determination of Opioid Medication Tramadol Hydrochloride in Pharmaceutical Formulations

Background: The exceptional characteristics of cerium oxide (CeO2) and aluminum oxide (Al2O3) nanoscales have inspired significant attention to those nanocomposites as possible electroactive resources for applications of sensing and biosensing. Methods: In this research, an innovative new factionalized CeO2/Al2O3 nanocomposite membrane sensor was presented to assess tramadol hydrochloride (TRD) in marketable products. Results: Tramadol-phosphomolybdate (TRD-PM) was formed by mixing tramadol hydrochloride and phosphomolybdic acid (PMA) in the attendance of polymeric matrix and o-nitrophenyloctyl ether solvent mediator. With 1.0 × 10−10–1.0 × 10−2 mol L−1 as a range of linearity and EmV = (57.567 ± 0.2) log [TRD] + 676.29 as a regression equation, the functionalized sensor using TRD-PM-CeO2/Al2O3 nanocomposite showed great selectivity and sensitivity for the discriminating and measurement of TRD. Using the regression equation EmV = (52.143 ± 0.4) log [TRD] + 431.45, the unmodified coated wire sensor of TRD-PM, on the other hand, showed a Nernstian response between 1.0 × 10−6 and 1.0 × 10−2 mol L−1, Using the methodology’s specified guidelines, the proposed improved potentiometric system was validated against several criteria. Conclusion: The suggested method is suitable for the determination of TRD in its products.


Introduction
The evolution of modified sensing and biosensing probes has been aided by advances in nanoscience technologies and nanomaterial engineering, which have opened up new fields in scientific inquiry. The recent research has concentrated on the creation of nanocomposites rather than single nanoparticles. Because of their interfacial interactions, these nanocomposites frequently have various nanoscale domains, which produce synergistic effects [1]. Chemical resistance, high conductivity, biocompatibility, and flexibility are just a few of the advantages that nanocomposites have over traditional polymers [2]. Recent advancements in scientific domains such as Recent advancements in scientific domains, such as industry [3], biology [4], and material science [5] need the creation of innovative sensing knowledge that associates low power consumption, compactness, and high tangible sensitivity.
Nanocomposite is a high-activity nanostructure that offers a wide range of engineering and combining options. Their potential is so great that can be effectively utilized in a diversity of sensing and biosensing approaches [6], due to their expanding requirement and speedy inquiry to be in the fabrication of sensors; indeed, they have emerged as viable options for addressing the disadvantages of micro composites. Additionally, these materials have exceptional structures and optical properties which are not seen in traditional types [7]. Furthermore, nanocomposite production is regarded as a critical step in the formation of a huge number of electronics [8,9], systems of drug targeting [10,11], medicinal, and immunosensing probes [12].  Tramadol's extended-release pills and capsules are only prescribed for those who are likely to require pain relief 24 h a day; it belongs to the opiate (narcotic) analgesics class of drugs [41].
Several analytical approaches, such as spectroscopic [42], chromatographic separation [43][44][45], and electrochemical methods [46,47], have previously been used to assess and quantify TRD. Although these previously published methods had good sensitivity and selectivity for TRD detection, the reminder had some drawbacks, such as requiring a long analytical time, a high level of operating skills, and the use of huge volumes of solvents.
The goal of this research was to develop a modified metal oxide (CeO 2 /Al 2 O 3 ) nanocomposite coated wire sensor that could detect TRD in commercial items with high sensitivity and selectivity. To improve the sensitivity and selectivity of the potentiometric modified sensor, a new technique based on utilizing the exceptional physical, chemical, optical, and conductive features of the chosen metal oxides has been proposed. The integration of CeO 2 /Al 2 O 3 in a polymeric matrix will have an impact on the suggested sensor's sensitivity and selectivity for the selected drug. Method validation follows ICH criteria [48] to confirm the indicated method's analytical appropriateness. In addition, a comparison was made between the CeO 2 /Al 2 O 3 nanocomposite coated membrane sensor proposed and the normally built kind.

Preparation of TRD-PM Electroactive Material
The electroactive complex TRD-PM was made by combining similar volumes (50 mL) of aqueous TRD and PMA solution with an equimolar concentration (1.0 × 10 −2 mol L −1 ) of TRD. A greenish TRD-PM precipitate was formed. The precipitate was cleaned with Milli Q water and kept to dry overnight after being filtered with Whatman filter paper No. 41.

Synthesis of CeO 2 and Al 2 O 3 Nanoparticles
CeO 2 NPs were synthesized by the preparation of 50 mL of 0.5 mol L −1 of cerium nitrate hexahydrate in Milli Q water as a precursor solution. With constant stirring and at ambient temperature, 2.0 mol L −1 of NaOH was dripped slowly. The addition was performed within 30 min. The mixture was centrifuged at 2500 rpm for 10 min. The precipitate was collected using Whatman filter paper No. 1, then rinsed thoroughly with Milli Q water. The formed CeO 2 NPs were dried for 6 h at 100 • C. To evaporate the water, the formed nanoparticles were calcinated in a furnace oven at 600 • C for 4 h.
A sol-gel method was used to synthesize Al 2 O 3 NPs by mixing 50 mL of aluminum nitrate (2.0 mol L −1 ) with 20 mL of citric acid and the mixture was stirred at 250 rpm for 30 min. The prepared solution was heated under magnetic stirring at 60 • C for a further 30 min until the formation of while gel. The formed gel was heated to 80 • C under continuous stirring until a transparent gel was formed. The resulting nanoparticles were filtered after 10 min centrifugation at 2500 rpm. The collected Al 2 O 3 NPs were washed three times with Milli-Q water, oven-dried at 90 • C for 12 h, and thereafter sintered for 4 h at 600 • C.

Preparation of Standard TRD Solution
A TRD standard solution (0.1 mol L −1 ) was made by adding 2.998 g of TRD authentic powder to deionized water (100 mL). The analytical testing samples were diluted in the range of 1.0 × 1.0 −10 -1.0 × 10 −2 mol L −1 using the same solvent.

Sensor Design and Membrane Composition
A Typical (TRD-PM) sensor was designed using mixing-electroactive substances (TRD-PM, 10 mg), (PVC, 190 mg), and o-NPOE, 0.35 mL plasticizer in 5 mL of THF. The resulting cocktail was placed into a rounded dish and allowed to gently evaporate at room temperature. Deionized water, followed by acetone, was used to polish and clean the aluminum wire's tip. The wire's tip had been cleaned. The cleaned tip of the wire was submerged in the polymeric membrane solution (TRD-PM) many times until a coated membrane formed on its surface. Additional clean Al wire was dipped three times in the polymeric solution of CeO 2 /Al 2 O nanocomposite to generate a thin layer membrane on its surface for the modified sensor. After allowing the sensor to dry, it was dipped multiple times in the aforementioned polymeric (TRD-PM) solution until it formed a homogenous covered membrane. The cell assembly: Al wire/coated membrane/test solution/Ag/AgCl reference electrode was used in both constructed sensors. The potentiometric system and the functionalized TRD-PM-CeO 2 /Al 2 O 3 nanocomposite sensor were illustrated, as shown in Figure 2.

Calibration Graph
The potential readings (mV) of (TRD-PM) and (TRD-PM-CeO 2 /Al 2 O 3 ) nanocomposite sensors were measured and graphed versus -logarithm TRD concentrations (mol L −1 ). The linearity was estimated separately using TRD standard solutions (50 mL) in the concentration range 1.0 × 10 −10 -1.0 × 10 −2 mol L −1 and the constructed functional TRD-PM or TRD-PM-CeO 2 /Al 2 O 3 sensors were used and the applied reference one was (Ag/AgCl) electrode. The membrane surface should be cleaned using Milli-Q water and dried with soft paper before each measurement.

Calibration Graph
The potential readings (mV) of (TRD-PM) and (TRD-PM-CeO2/Al2O3) nanocomposite sensors were measured and graphed versus -logarithm TRD concentrations (mol L −1 ). The linearity was estimated separately using TRD standard solutions (50 mL) in the concentration range 1.0 × 10 −10-1.0 × 10 −2 mol L −1 and the constructed functional TRD-PM or TRD-PM-CeO2/Al2O3 sensors were used and the applied reference one was (Ag/AgCl) electrode. The membrane surface should be cleaned using Milli-Q water and dried with soft paper before each measurement.

Optimization of Analytical Conditions
The pH of the examined solutions can have a substantial impact on the potential response of the coated wire sensors that have been designed. The suitable pH range using TRD (1.0 × 10 −5 mol L −1 ) solution was measured using TRD-PM and modified TRD-PM-CeO2/Al2O3 nanocomposite sensors were measured. The acidity and alkalinity of the test sample were adjusted using 0.1 mol L −1 of hydrochloric acid and sodium hydroxide. The pH graphs were created by plotting the change in potential vs. pH.
Selectivity of the studied TRD sensors was monitored by exploiting a separate solution approach [49]. The selectivity coefficient of each sensor for TRD and various foreign substances and additives such cations (Na + , K + , Ag + , Mg 2+ , Ca 2+ , Zn 2+ , and Fe 3+ ), sugars (lactose, Fructose, and starch), amino acids (histidine, glycine, lysine, and tryptophan) have been tested. The selectivity of the suggested sensors was measured using 1.0 × 10 −3 mol L −1 solution of TRD and interferent species, separately. The tolerable value (KpotTRD + ) was estimated from the previously reported equation [49].
The response time was determined by recording the dynamic sensors response of the investigated TRD solution, using a TRD working concentration range.

Quantification of Tramadol Hydrochloride ® Capsules
The content of 10 tramadol hydrochloride ® capsules (50 mg/capsules) was mixed well and weighed. A precise amount (0.2998 g in 50 mL Milli-Q water) was centrifuged (5 min at 1500 rpm), and the co-formulated components were removed by filtering. Deionized water was used to complete the clear solution to be 100 mL. The same solvent was used to dilute the resulting TRD solution (1.0 × 10 −2 mol L −1 ) to prepare the working samples in the range of 1.0 × 10 −5 -1.0 × 10 −2 and 1.0 × 10 −10 -1.0 × 10 −2 mol L −1 . The investigated drug was quantified in commercial capsules using the developed TRD-PM and functionalized TRD-PM-CeO2/Al2O3 nanocomposite sensors independently.

Optimization of Analytical Conditions
The pH of the examined solutions can have a substantial impact on the potential response of the coated wire sensors that have been designed. The suitable pH range using TRD (1.0 × 10 −5 mol L −1 ) solution was measured using TRD-PM and modified TRD-PM-CeO 2 /Al 2 O 3 nanocomposite sensors were measured. The acidity and alkalinity of the test sample were adjusted using 0.1 mol L −1 of hydrochloric acid and sodium hydroxide. The pH graphs were created by plotting the change in potential vs. pH.
Selectivity of the studied TRD sensors was monitored by exploiting a separate solution approach [49]. The selectivity coefficient of each sensor for TRD and various foreign substances and additives such cations (Na + , K + , Ag + , Mg 2+ , Ca 2+ , Zn 2+ , and Fe 3+ ), sugars (lactose, Fructose, and starch), amino acids (histidine, glycine, lysine, and tryptophan) have been tested. The selectivity of the suggested sensors was measured using 1.0 × 10 −3 mol L −1 solution of TRD and interferent species, separately. The tolerable value (K pot TRD + ) was estimated from the previously reported equation [49].
The response time was determined by recording the dynamic sensors response of the investigated TRD solution, using a TRD working concentration range.

Quantification of Tramadol Hydrochloride ® Capsules
The content of 10 tramadol hydrochloride ® capsules (50 mg/capsules) was mixed well and weighed. A precise amount (0.2998 g in 50 mL Milli-Q water) was centrifuged (5 min at 1500 rpm), and the co-formulated components were removed by filtering. Deionized water was used to complete the clear solution to be 100 mL. The same solvent was used to dilute the resulting TRD solution (1.0 × 10 −2 mol L −1 ) to prepare the working samples in the range of 1.0 × 10 −5 -1.0 × 10 −2 and 1.0 × 10 −10 -1.0 × 10 −2 mol L −1 . The investigated drug was quantified in commercial capsules using the developed TRD-PM and functionalized TRD-PM-CeO 2 /Al 2 O 3 nanocomposite sensors independently.

Characterization of CeO 2 /Al 2 O 3 Nanocomposite
Various spectroscopic investigations such as XRD, UV-Vis, FT-IR, and EDX were performed to characterize and confirm the formation of the synthesized CeO 2 /Al 2 O 3 nanocomposite. The UV-Vis analysis is one of the top appropriate and helpful ways for principal validation of the form, size, and stability of designed nanoparticles in their aqueous suspensions. The optical absorbance spectra of CeO 2 , Al 2 O 3 , and CeO 2 /Al 2 O 3 nanocomposite were measured at 200-600 nm and exhibited three large absorption peaks at 320, 240, and 402 nm for CeO 2 NPs, Al 2 O 3 NPs, and CeO 2 /Al 2 O 3 nanocomposite, respectively ( Figure 3).
composite. The UV-Vis analysis is one of the top appropriate and helpful ways for principal validation of the form, size, and stability of designed nanoparticles in their aqueous suspensions. The optical absorbance spectra of CeO2, Al2O3, and CeO2/Al2O3 nanocomposite were measured at 200-600 nm and exhibited three large absorption peaks at 320, 240, and 402 nm for CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite, respectively ( Figure  3). The produced bandgaps of the metal oxide nanoparticles were determined obeying the formula: where h, c, and λ are Planck's constant, light velocity, and absorption wavelength, respectively. On applying the Tauc plot function, the estimated optical bandgaps energy of CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite were found to be 3.36, 3.68, and 2.70 eV, respectively [50,51] (Figure 4a-c). Because of redshift, the bandgap energy difference between CeO2NPs and CeO2/Al2O3 nanocomposite was 0.66 eV, while the gap energy difference between Al2O3NPs and CeO2/Al2O3 nanocomposite was 0.97 eV. The decrease in bandgap energy in CeO2/Al2O3 nanocomposite improves the electron active sites to the entire movement on the Al2O3 surface, and their interaction might speed up the oxidation process. The surface plasmon resonance improves radiation penetration, creates scattering probability, and supplies the surface with a reduction form. These activities entail the formation of holes and the separation of electrons on the surface, which improves the oxidation process. Furthermore, changes in the dielectric matrix have been shown to influence the position of the SPR's absorbance peak. The effective dielectric function of the matrix is known to have a direct relationship with the refractive index. A rise in the refractive index is promoted by the crystallization of CeO2NPs (n = 2.20) to (n = 3.54), and AL2O3NPs (n = 1.33) to (n = 1.76). This adjustment causes a red shift in the absorbance peak due to an increase in the dielectric function values [52]. The produced bandgaps of the metal oxide nanoparticles were determined obeying the formula: where h, c, and λ are Planck's constant, light velocity, and absorption wavelength, respectively. On applying the Tauc plot function, the estimated optical bandgaps energy of CeO 2 NPs, Al 2 O 3 NPs, and CeO 2 /Al 2 O 3 nanocomposite were found to be 3.  [53]. The FT-IR spectrum of the Al 2 O 3 NPs is described in Figure 5b.      [53]. The FT-IR spectrum of the Al2O3NPs is described in Figure 5b.
where D, λ, β, and θ represent crystallite size, wavelength, the half-width of the diffraction peak, and the diffraction angle of the highest peak, respectively [56]. The broad absorption bands, appeared at 3466 cm −1 and 1632 cm −1 , resulted from stretching and bending O-H vibration of absorbed water, respectively. The stretching vibration of Al-OH bond appeared to correspond another band observed at 1362 cm −1 . The peaks at 832 cm −1 and 586 cm −1 correspond to the Al-O bond [54]. The CeO2/Al2O3 nanocomposite spectrum displayed various absorption bands at 3464 cm −1 (O-H), 2374 cm −1 (O=C=O of the carbon dioxide), and 1630 cm −1 (O-H vibration mode of water). The formation of CeO2/Al2O3 nanocomposite was confirmed by the appearance of stretching vibration peaks at 562 and 832 cm −1 (Figure 5c). The shift of the peaks in the nanocomposite spectrum to 562 and 832 cm −1 indicating the incorporation of CeO2 nanoparticles on the surface of Al2O3 nanoparticles.
The XRD patterns of CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite were scanned from 10-80 degrees with a 2θ min-1 scan rate. The XRD pattern of CeO2NPs showed different intensity peaks corresponding to crystal planes at 28.41° (1 1 1) (Figure 6c). Moreover, the Scherer equation was used to calculate the average size of CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite by obeying: where D, λ, β, and θ represent crystallite size, wavelength, the half-width of the diffraction peak, and the diffraction angle of the highest peak, respectively [56]. The average crystallite size obtained for CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite was found to be 17.35 nm, 18.80 nm, and 21.66 nm, respectively. The dislocation density (δ) is identified as the length of dislocation lines per unit volume of the crystal, which reflects number of defects in the sample and is estimated using the following equation [57]. The dislocation density (δ) is identified as the length of dislocation lines per unit volume of the crystal, which reflects number of defects in the sample and is estimated using the following equation [57].
where the crystallite size is donated by D. The dislocation density of CeO2NPs and Al2O3NPs at room temperature was found to be 6.94 × 10 −3 and 1.31 × 10 −3 (nm) −2 , respectively. The equation [58] was used to calculate the length of Ce-O and Al-O bond. The values in the above equation expressed as ''u" the potion in the wurtzite shape and can be determined by measuring the displacement of the atom with respect to the next atom along the axis ''c".
Where u is the positional parameter in the wurtzite structure and is a measure of the amount by which each atom is displaced according to the next along the 'c' axis. 'u' is given by the equation: The Ce-O and Al-O bond lengths were calculated to be 1.869Å and 1.987Å, respectively. The estimated values matched the unit cell of Ce-O and Al-O bond lengths [59,60].
The dynamic light scattering (DLS) method was applied to measure the mean sizeaverage diameter (d.nm) and the size distribution by the intensity of the synthesized CeO 2 NPs and Al 2 O 3 NPs. The particle size distribution of CeO 2 NPs and Al 2 O 3 NPs was measured using a particle size analyzer Zetasizer Ultra (Malvern Panalytical Ltd., Malvern, UK). As demonstrated in Figure 7a,b, the particle size distribution of CeO 2 NPs and Al 2 O 3 NPs was about 93.6 ± 2.4 and 104.5 ± 0.6 nm, respectively.
Al2O3NPs at room temperature was found to be 6.94 × 10 and 1.31 × 10 (nm) , respectively. The equation [58] was used to calculate the length of Ce-O and Al-O bond.
The values in the above equation expressed as ''u'' the potion in the wurtzite shape and can be determined by measuring the displacement of the atom with respect to the next atom along the axis ''c''.
Where u is the positional parameter in the wurtzite structure and is a measure of the amount by which each atom is displaced according to the next along the 'c' axis. 'u' is given by the equation: The Ce-O and Al-O bond lengths were calculated to be 1.869Å and 1.987Å, respectively. The estimated values matched the unit cell of Ce-O and Al-O bond lengths [59,60].
The dynamic light scattering (DLS) method was applied to measure the mean sizeaverage diameter (d.nm) and the size distribution by the intensity of the synthesized CeO2NPs and Al2O3NPs. The particle size distribution of CeO2NPs and Al2O3NPs was measured using a particle size analyzer Zetasizer Ultra (Malvern Panalytical Ltd., Malvern, UK). As demonstrated in Figure 7a,b, the particle size distribution of CeO2NPs and Al2O3NPs was about 93.6 ± 2.4 and 104.5 ± 0.6 nm, respectively. The size distribution profiles of CeO2NPs and Al2O3NPs exhibited one remarkable peak for each with intensities 90.8%, 96.7%, respectively, with a polydispersity index (PdI) 0.284 and 0.354 for CeO2NPs and Al2O3NPs, respectively, suggesting that the synthesized nano metal oxides had a little agglomeration [61]. The zeta potential of pre-synthesized CeO2NPs and Al2O3NPs with negative values of about −25.5 and −17.6 mV indicated a strong negative charge (Figure 8a,b). The negative surface zeta potential of CeO2NPs and Al2O3NPs suggests their reduction in metal oxide nanoparticles. The size distribution profiles of CeO 2 NPs and Al 2 O 3 NPs exhibited one remarkable peak for each with intensities 90.8%, 96.7%, respectively, with a polydispersity index (PdI) 0.284 and 0.354 for CeO 2 NPs and Al 2 O 3 NPs, respectively, suggesting that the synthesized nano metal oxides had a little agglomeration [61]. The zeta potential of pre-synthesized CeO 2 NPs and Al 2 O 3 NPs with negative values of about −25.5 and −17.6 mV indicated a strong negative charge (Figure 8a,b). The negative surface zeta potential of CeO 2 NPs and Al 2 O 3 NPs suggests their reduction in metal oxide nanoparticles.
The surface morphology, and elemental presence in the pre-synthesized CeO 2 NPs, Al 2 O 3 NPs, and CeO 2 /Al 2 O 3 nanocomposite was visualized by SEM coupled with EDX (Figure 9a-c). The images of SEM showed that most of the synthesized CeO 2 NPs were cubic fluorite in shape (Figure 9a), whereas, the SEM images of the pre-synthesized Al 2 O 3 NPs revealed quasi-spherical shape in (Figure 9b); however, in the synthesized CeO 2 /Al 2 O 3 nanocomposite, the surface of Al 2 O 3 was clustered by CeO 2 NPs, the shape was changed to the lattice arrangement of the nanocomposite (Figure 9c)  The surface morphology, and elemental presence in the pre-synthesized CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite was visualized by SEM coupled with EDX (Figure 9a-c). The images of SEM showed that most of the synthesized CeO2NPs were cubic fluorite in shape (Figure 9a), whereas, the SEM images of the pre-synthesized Al2O3NPs revealed quasi-spherical shape in (Figure 9b); however, in the synthesized CeO2/Al2O3 nanocomposite, the surface of Al2O3 was clustered by CeO2NPs, the shape was changed to the lattice arrangement of the nanocomposite (Figure 9c). Thus, CeO2/Al2O3 nanocomposite was rounded in shape with an average of size 100 nm. The elemental composition of CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite measured by EDX showed the presence of Ce with a weight percentage 80.42% and atomic percentage 33.35% and O with 19.58% and 66.65%, respectively.
The EDX spectrum of Al2O3NPs confirmed the presence of weight % (79.78% and 20.22%) and atomic % (39.91% and 60.09%) for Al and O, respectively; however, CeO2/Al2O3 nanocomposite spectrum showed the presence of Ce, Al, and O elements with weights of 5.54%, 67.21%, and 27.25%, atomic percentage of 1.27%, 39.41%, and 59.32%, respectively. The atomic arrangement of pre-synthesized CeO2NPs, Al2O3NPs, and CeO2/Al2O3 nanocomposite was evaluated by EDX mapping analysis. Figure 9a also showed the mapping of CeO2NPs, where Ce ions are spread over the O, while the mapping images of Al2O3NPs showed mutual spreading of Al and O ( Figure 9b); however, CeO2/Al2O3 nanocomposite mapping spectrum exhibited the content of Al was higher than Ce and O (Figure 9c). Furthermore, the decoration of Ce with Al and O atoms was noticed in the mapping analysis of CeO2/Al2O3 nanocomposite.

Performance Response of the Suggested Sensors
TRD interacts with PMA to form the TRD-PM complex, which is extremely stable and soluble in THF. THF was used to combine the membrane cocktail to create the conventional TRD-PM and functionalized coated wire TRD-PM-CeO2/Al2O3NPs nanocomposite sensors. The application of (o-NPOE, = 24) with a high dielectric constant increases membrane complex uniform solubility and computability with the polymeric phase of the membrane; it also improves the sensor's selectivity coefficient by providing a mechanical property for the covered membrane [62]. The potential responses of TRD-PM and TRD-PM-CeO2/Al2O3NPs nanocomposite were described in Table 1 Figure 9b); however, CeO 2 /Al 2 O 3 nanocomposite mapping spectrum exhibited the content of Al was higher than Ce and O (Figure 9c). Furthermore, the decoration of Ce with Al and O atoms was noticed in the mapping analysis of CeO 2 /Al 2 O 3 nanocomposite.

Performance Response of the Suggested Sensors
TRD interacts with PMA to form the TRD-PM complex, which is extremely stable and soluble in THF. THF was used to combine the membrane cocktail to create the conventional TRD-PM and functionalized coated wire TRD-PM-CeO 2 /Al 2 O 3 NPs nanocomposite sensors. The application of (o-NPOE, = 24) with a high dielectric constant increases membrane complex uniform solubility and computability with the polymeric phase of the membrane; it also improves the sensor's selectivity coefficient by providing a mechanical property for the covered membrane [62]. The potential responses of TRD-PM and TRD-PM-CeO 2 /Al 2 O 3 NPs nanocomposite were described in Table 1   The dynamic responsiveness of the created TRD-PM conventional and functionalized TRD-PM-CeO 2 /Al 2 O 3 NPs nanocomposite sensors was examined under ideal experimental environments to identify differences between the time of instant potential and the value of its steady-state (1 mV). The above-mentioned conventional and functionalized sensors had dynamic responses of 60 and 35 s, respectively. The sensor enhanced with metal oxide nanocomposite has a faster response time and more mechanical stability than the standard sensor. The electrical conductivity of the modified sensor towards detection of TRD in the sample is improved by the functionalization of the membrane with metal oxides nanocomposite (high surface area: volume ratio) and their new advanced features. Furthermore, when nanoparticles are utilized as conductive materials in sensing systems, the nanocomposite's remarkable electrical and capacity features, including significant charge transfer at nanomaterial interfaces, are critical [65].  The dynamic responsiveness of the created TRD-PM conventional and functionalized TRD-PM-CeO2/Al2O3NPs nanocomposite sensors was examined under ideal experimental environments to identify differences between the time of instant potential and the value of its steady-state (1 mV). The above-mentioned conventional and functionalized sensors had dynamic responses of 60 and 35 s, respectively. The sensor enhanced with metal oxide nanocomposite has a faster response time and more mechanical stability than the standard sensor. The electrical conductivity of the modified sensor towards detection of TRD in the sample is improved by the functionalization of the membrane with metal oxides nanocomposite (high surface area: volume ratio) and their new advanced features. Furthermore, when nanoparticles are utilized as conductive materials in sensing systems, the nanocomposite's remarkable electrical and capacity features, including significant charge transfer at nanomaterial interfaces, are critical [65].
The hydrogen ion concentration has a significant impact on the membrane sensor's potential response. Thus, determining the appropriate pH range where hydrogen ions have no effect on the coated membrane sensor's potential response is critical. The results The hydrogen ion concentration has a significant impact on the membrane sensor's potential response. Thus, determining the appropriate pH range where hydrogen ions have no effect on the coated membrane sensor's potential response is critical. The results revealed that the response of TRD-PM and TRD-PM-CeO 2 /Al 2 O 3 NPs nanocomposite sensors are unaffected in the pH range 2-7, and that can be easily predicted using the developed sensors in this pH range ( Figure 11). The protonated ion-pair complex was formed at high [H + ] in an acidic medium (pH 2), and the sensor potential readings were marginally augmented as a result of low responsiveness to TRD ions; meanwhile, in alkaline medium (pH > 7) where [OH − ] is high, the potential readings were progressively reduced due to the competition between TRD ions and OH-ions. Consequently, this decreases interactions between the investigated drug ions and sites of ion-pair on the sensor membrane [66]. revealed that the response of TRD-PM and TRD-PM-CeO2/Al2O3NPs nanocomposite sensors are unaffected in the pH range 2-7, and that can be easily predicted using the developed sensors in this pH range ( Figure 11). The protonated ion-pair complex was formed at high [H + ] in an acidic medium (pH 2), and the sensor potential readings were marginally augmented as a result of low responsiveness to TRD ions; meanwhile, in alkaline medium (pH > 7) where [OH -] is high, the potential readings were progressively reduced due to the competition between TRD ions and OH-ions. Consequently, this decreases interactions between the investigated drug ions and sites of ion-pair on the sensor membrane [66]. A separate solution approach [67] was employed to assess the effect of interference of several foreign constituents on the coefficient of selectivity of the developed TRD sensors. The functionalized TRD-PM-CeO2/Al2O3 nanocomposite sensor exhibited high selec- A separate solution approach [67] was employed to assess the effect of interference of several foreign constituents on the coefficient of selectivity of the developed TRD sensors. The functionalized TRD-PM-CeO 2 /Al 2 O 3 nanocomposite sensor exhibited high selectivity towards the detection of TRD. The extraordinary physicochemical properties of the produced CeO 2 /Al 2 O 3 NPs, as well as their large interfacial area, improve the conductivity of the modified sensor and therefore its selectivity for TRD ions. Furthermore, the free energy transfer of ions (TRD + ) created between the active sites in the membrane and the working solution is referred to by the TRD coated membrane selectivity. The evaluated cations, sugars, and amino acids caused no interference. As a result, using the modified TRD sensor for TRD determination provided high selectivity and tolerance ( Table 2).

Quantification of TRD in Bulk Form
The TRD drug was determined in its authentic samples using the designed conventional TRD-PM and TRD-PM-CeO 2 /Al 2 O 3 sensors, and the findings were expressed as 98.80 ± 0.9% and 99.81 ± 0.2%, respectively ( Table 3). The use of functionalized TRD-PM-CeO 2 /Al 2 O 3 sensor containing CeO 2 NPs (~23) and Al 2 O 3 NPs (~7.8-11.1) improved the dynamic detection of the TRD solution.

Validation of the Suggested Method
The guideline of the International Council for Harmonization of Technical Requirements for Pharmaceuticals (ICH) [48]   To study the accuracy of designed sensors, 9 authentic TRD concentrations in the range of 1.0 × 10 −6 -1.0 × 10 −2 and 1.0 × 10 −10 -1.0 × 10 −2 mol L −1 were used. The accuracy of the suggested potentiometric approach was expressed as mean percentage recoveries of 98.56 ± 0.8% and 99.85 ± 0.2% for TRD-PM and TRD-PM-CeO 2 /Al 2 O 3 nanocomposite, respectively (Table 4). Intermediate precision experiments were also used to investigate the precision of the suggested functionalized potentiometric TRD-PM-CeO 2 /Al 2 O 3 nanocomposite system. For the two, the recorded data were found as a percentage relative standard deviation (% RSD) of 0.2% and 0.4%, for intra-day and inter-day assays, respectively (Table 5). Table 4. Accuracy results of the analysis of TRD samples using conventional and functionalized TRD-PM and TRD-PM-CeO 2 /Al 2 O 3 nanocomposite coated wire sensors.  The potentiometric system's robustness was tested by altering the pH of working solutions to 7 ± 0.5, which was a minor change in the procedure parameter. The obtained percentage recoveries for the standard and functionalized TRD coated wire sensors were 98.35 ± 0.5% and 99.66 ± 0.3%, respectively (Table 1). To prove the ruggedness of the proposed technique, TRD samples were analyzed using a different pH-meter (Metrohm model-744) in another laboratory and by a different analyst. For the above designed TRD-PM and TRD-PM-CeO 2 /Al 2 O 3 nanocomposite sensors, the mean percentage recoveries were found to be 98.83 ± 0.7 and 99.72 ± 0.4 percent, respectively ( Table 1). The results of technique validation were in suitable accordance with those obtained using the suggested system, with no notable variations.

Estimation of TRD in Tramadol hydrochloride ® Capsules
The examined TRD was determined utilizing the designed TRD-PM and TRD-PM-CeO 2 / Al 2 O 3 nanocomposite in its marketed capsules tramadol hydrochloride ® (50 mg/capsule). The % recoveries of TRD were obtained by the regression equations using the potential readings of the working solutions 1.0 × 10 −6 -1.0 × 10 −2 and 1.0 × 10 −10 -1.0 × 10 −2 mol L −1 . For the above-mentioned sensors, the recorded results were 98.77 ± 0.8% and 99.63 ± 0.5%, respectively. The obtained findings were compared to the approach provided by Shawish et al. [68] using the Student's t-test and F-test [69] and revealed that the developed sensor had outstanding sensitivity and selectivity for the determination of TRD (Table 6). The dielectric constant is an important criterion for determining a material's ability to hold charges [70]. Electronics and sensors frequently use metal oxides with a high dielectric constant. They allow for the exertion of an electrostatic field and hence the storage of charges because they do not allow for the flow of charges through them [71]. The electrical, optical, and conductive capabilities of the functionalized sensor might all be improved by combining metal oxide nanoparticles with a polymeric medium in nanocomposites. Changes in the shape and size of the particles have a big impact on these qualities. As previously addressed, nanoparticles can act as a conductive connection between the polymeric chains, resulting in an increase in the composites' electrical conductance [72,73]. The efficiency of the designed functionalized TRD-PM-CeO 2 /Al 2 O 3 nanocomposite sensor was compared to that of previously constructed sensors [69,73,74] (Table 7). The modified sensor had a higher sensitivity than the published sensors for detecting TRD, with a detection range of 1.0 × 10 −10 -1.0 × 10 −2 and a LOD of 5.0 × 10 −11 mol L −1 . The most significant component in developing ultrasensitive sensors with required features is the choice of nanostructured materials and sensor design method. The surface-to-volume ratio, which is a critical component in enhancing contact reactions on the overall electrical conductivity of nanomaterials, is determined by the shape and size of the nanoparticles utilized. Thus, due to the great chemical stability of these nanomaterials, the nanoscale morphology will affect not only the sensitivity of the sensor but also the dynamic responsiveness and long-term stability of the sensor. The molecular structure and polymeric media, such as crystallinity and long-chain polymer, may influence the electrical conductivity of metal oxide nanocomposite-fabricated sensors [75]. Table 7. Comparative results between the suggested conventional and functionalized TRD-PM and TRD-PM-CeO 2 /Al 2 O 3 nanocomposite coated wire sensors.

Conclusions
The current study describes a simple and ultrasensitive functionalized TRD-PM-CeO 2 / Al 2 O 3 nanocomposite potentiometric sensor for determining TRD in authentic powder and commercial formulations that was successfully built. The modified sensor had a large surface area-tovolume ratio, which gave it excellent sensitivity in the detection of TRD with linear relationships in the concentration ranges 1.0 × 10 −6 -1.0 × 10 −2 and 1.0 × 10 −10 -1.0 × 10 −2 mol L −1 , and low detection limits of 5.0 × 10 −6 and 5.0 × 10 −11 mol L −1 for the conventional and functionalized sensors, respectively, with least square regression equations EmV = (52.143 ± 0.4) log [TRD] + 431.45 and EmV = (57.567 ± 0.2) log [TRD] +676.29 for the above described TRD sensors, respectively. The results of the proposed method were statistically assessed and compared to those of sensors that had previously been reported. The modified TRD-PM-CeO 2 /Al 2 O 3 nanocomposite was shown to have a substantially greater potential response than the standard kind. Furthermore, coating the sensor's surface with a modified layer of metal oxide nanocomposite polymeric membrane improves the sensor's electroconductivity and quantification of the tested TRD in capsules, with a mean percentage recovery of 99.63 ± 0.5 percent for the TRD-PM-CeO 2 /Al 2 O 3 nanocomposite sensor, indicating high sensitivity and selectivity. As a result, the use of metal oxide nanocomposite in the construction of polymeric sensors opens up a promising avenue for the development of unique modified potentiometric sensors. Data Availability Statement: The collected data from the current study was included in the text.