1 Introduction

Ceftizoxime (CFX) has been proposed as the third descendant cephalosporin antibiotic, which activates against aerobic of the gram-positive and -negative bacteria and declines putrefaction via interference in the wall by rupturing the wall and thus decays the bacteria [1, 2]. In fact, CFX has been introduced as one of the active agents against putrefaction with the extensive uses the treatment of susceptible infection like lung infections, skin and soft tissue, bone, and joint infections and other abdominal infection. Therefore, it is of special significance to quantitatively detect the analgesics and antibiotics in the biological fluids for the drug metabolisms [3, 4].

Researchers have presented numerous procedures like chromatography [5,6,7] and spectrophotometry [8, 9] to detect CFX. Nonetheless, such compounds consisting of sulfur cannot be efficiently detected by spectrophotometry due to the lack of light absorption of the compounds by them [10, 11]; hence, their derivatization would be developed. In other hand, the above techniques include difficult extraction phases for analyzing the real sample. Additionally, multiple materials must be consumed [12, 13]. For this reason, experts in the field must provide rapid sensitive analytical techniques.

Currently, researchers have largely employed electro-analytical procedures to the biomedical and pharmaceutical analyses as the biological reactions in humans and electrochemical reactions at the interface of the solution electrode undergo the same set of the electron transfer pathways. Electrochemical methods, due to their rapid response, simplicity, low cost, higher sensitivity, real-time detection, and acceptable selectivity with in-situ analysis are considerably studied in the pharmaceutical major compounds with the electrochemical activities [14,15,16,17,18,19,20,21,22,23,24].

Modification of the surfaces of such sensors with nanomaterials can enhance these advantages [25, 26].

As a result of easier fabrication process, compatibility with diverse kinds of modifier, as well as renewability, CPEs are considerably employed as one of the proper matrices to prepare the modified electrodes. Additionally, the CPEs exhibit lower background currents than that of the noble metal electrodes or solid graphite [27,28,29,30,31,32].

Recently, nanomaterials have attracted increasing interest in different fields [33,34,35,36]. According to some studies, it is possible to design nanomaterials of the different types like single or hybrid/combinatorial nanostructures with distinct characteristics with the considerable differences from the common bulk materials. Nanosized materials the extensive uses for preparing electrochemical sensors due their large surface areas, unique electronic, structural, mechanical and catalytic properties [37,38,39]. Hence, it would be of special significance to illustrate electronic and physicochemical interactions at the interface of the nano-material based electrodes with the intended analytes in order thoroughly apply the potential of the modern electro chemical sensors [40,41,42,43,44,45,46,47,48].

According to some studies, hybrid materials enjoy a combination of the organic and inorganic elements for generating a synergic effect of the greater functions of specific components that act by themselves. Moreover, researchers have largely considered the metal–organic hybrids as the modified-electrode substances because of their large surface areas, proper pore volumes, available cages, higher biocompatibility as well as uniform structures [49, 50].

The ligands consisting of imidazole have been considered to be poorer π-acceptors and more acceptable π –donors than that of the analogous pyridine consisting of the ligands acting as a reasonable acceptor because of the nearly low-lying π*-orbitals. Moreover, the deprotonation of the amino N–H proton may result in the perturbation of the electronic features of the metal complexes via establishing a metal–ligand interaction [51,52,53,54]. Because of the existence of the nitrogen donor atoms, imidazole may have coordination with diverse transition metal ions. In addition, researchers have introduced copper as one of the rich and more cost-effective transition metal elements on Earth and therefore copper-based catalyst has been greatly examined to design an inexpensive electro-catalyst [55,56,57].

Furthermore, deprotonation/protonation of imidazole moiety on the copper complexes can largely regulate electrochemical and redox features of the copper complexes [58,59,60,61]. Here, we proposes the construction of an electrochemical sensor to detect CFX by modification of a carbon paste electrode with Cu(Him)2 and ionic liquid.

2 Experimental

2.1 Chemicals and Devices

Electrochemical properties were evaluated by Eco Chemie Autolab PGSTAT30 Potentiostat/Galvanostat System, the Netherlands. Then, we implemented a general purpose electrochemical system (GPES) software for monitoring the empirical conditions and applied conventional 3-electrodes cell at 25 ± 1 °C. Moreover, this research utilized the Ag/AgCl/KCl (3.0 M) electrode, the Cu (Him)2/ILCPE as well as a platinum wire as the reference, working and auxiliary electrodes, respectively. Finally, we applied Metrohm 710 pH-meter to measure pHs.

Element analysis EDX was carried out by using the MIRA3 instrument. Examination of X-ray diffraction (XRD) patterns could be done through the use of XRD device model X'Pert Pro made in the Netherlands. Scanning electron microscope (FE-SEM, MIRA III, Czech Republic) was used to determine the morphology of composition Cu(Him)2.

Purity common commercial products were the solvents and reagents employed in our research. Copper(II) sulfate, Imidazole (Him), Sodium bicarbonate (NaHCO3), were bought from Sigma-Aldrich and each reagent was of analytical grade. All other reagents and ceftizoxime were Merck (Darmstadt, Germany) with analytical grade. In addition, orthophosphoric acid as well as the respective salts (KH2PO4, K2HPO4, and K3PO4) with a pH ranging between 2.0 and 9.0 has been utilized to procure buffer solution (Table 1).

Table 1 Structural specifications of Cu(Him)2
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2.2 Preparation of Cu (Him)2

The preparation of Cu(Him)2 support was according to the literature. Briefly, a solution of Copper(II) sulfate (2.5 g, 10.1 mmol) into a 100 ml flask, Him (1.36 g, 20 mmol), and sodium bicarbonate (6.6 g, 78.56 mmol) were stirred for 3 h. The mixture is cooled to filter at environment temperature. The residue was washed with deionized water, to give the product as a blue powder. Then, we sealed autoclave and heated at 110 °C for 20 min.

2.3 Preparation of the Electrode

In this step, we mixed 10 mg of Cu (Him)2 nanoparticles, 900 mg of graphite powder, as well as a certain content of ionic liquid and liquid paraffin for making Cu (Him)2/ILCPE with a mortar and pestle. Afterwards, we poured the paste into the end of the glass tube (ca. 3.4 mm i.d. and 15 cm in length), and place a copper wire in paste for the electrical connection devices. Under certain circumstances, the excessive paste was pushed out of the tube and polished by a weighing paper for preparing a new surface.

In order to make comparisons, ionic liquid modified CPE (ILCPE) without Cu (Him)2, Cu (Him)2 carbon paste electrode (Cu (Him)2/CPE) without ionic liquid and unmodified CPE in the absence of both ionic liquid and Cu (Hin)2 NPs were similarly provided.

2.4 Procedure of Real Samples Preparation

CFX ampoule (with the labling 10 mg, Jaber Ebne Hayyan Pharmaceutical Company: Iran) was diluted with phosphate buffer solution (PBS) pH 5.0 and then, different amounts of the diluted solution was transferred into a 25 ml volumetric flask and diluted to the mark with the PBS at a pH of 5.0. Volume of CFX was analyzed by our procedure using the standard addition technique.

In the case of the urine samples, each sample was refrigerated shortly after collection. To perform the analyses, 10 ml of each sample was taken and centrifuged at 2000 rpm for a quarter, the supernatant was separated and filtered using a 0.45 µm filter paper. The solution was then transferred into and diluted to the mark in a 25 mL volumetric flask using PBS (pH = 5.0).Various amounts of SFX were spike into the samples for the purpose of analyses.

3 Results and Discussion

3.1 Characterization of Cu (Him)2 Nanoparticles

3.1.1 EDX Analyses of Cu(Him)2

The results of EDX show that all the elements; Cu, N and C in the sample are present. The weight percent of the elements Cu, N and C are 84.9, 9.11, 5.99 respectively. (Fig. 1 and Table 2).

Fig. 1
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EDX spectrum of Cu(Him)2 particles

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Table 2 Quantitative results EDX spectrum of Cu(Him)2 particles
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3.2 Analysis of the X-Ray Powder Diffraction

XRD profiles of Cu(Him)2 is shown in Fig. 2. The crystal phase is unique for Cu(Him)2. This pattern shows which Cu(Him)2 is pure crystalline phases without any impurities of the intermediates. As we have seen from the XRD pattern, this zeolite imidazole framework particle is well crystallized. This pattern shows the average size of particles about 15.6 nm.

Fig. 2
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Powder XRD pattern of the blue polymorph Cu(Him)2

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3.3 Sample Morphology

The surface morphologies of Cu(Him)2 particles were studied by FESEM and are shown in Fig. 3. From these figures can be seen all particles have nanotube structure and also samples average size are about 74 and 90 nm.

Fig. 3
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FESEM images of the Cu(Him)2

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3.4 Electrochemical Profile of the CFX on the Cu (Him)2 /ILCPE

Studies in the field have shown the dependence of the electro-chemical behaviour of CFX on the pH-value of the aqueous solutions. Hence, pH optimization would be of high importance for obtaining the electrocatalytic oxidation of CFX. It is notable that we examined the electro-chemical behaviour of CFX in 0.1 M PBS at various pH-values (2.0 < pH < 9.0) at the Cu(Him)2/ILCPE surface using CV. Furthermore, electro catalytic oxidation of CFX at the Cu(Him)2/ILCPE surface was acceptable in acidic condition as compared to the basic or neutral media. From the highest current obtained in acidic conditions, pH 5.0 was selected as an optimized pH to electro catalyze CFX oxidation over Cu(Him)2/ILCPE surface (Fig. 4). In addition, equal electron as well as proton contributed to the CFX electrochemical reaction at surface of Cu(Him)2/ILCPE through the Ep slope vs. pH plot (Fig. 5).

Fig. 4
figure 4

Current-pH curve for electrooxidation of 100.0 nM CFX at the surface of Cu(Him)2/ILCPE at various pH values (2.0–9.0) in 0.1 M phosphate buffered solution at a scan rate of 50 mV s−1

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Fig. 5
figure 5

E plot versus pH for electrooxidation of 100.0 nM CFX at the surface of Cu(Him)2/ILCPE at various pH values (2.0–9.0) in 0.1 M phosphate buffered solution at a scan rate of 50 mV s −1

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Figure 6 represents the CV response for electrochemical oxidation of 500.0 nM CFX at the unmodified CPE (curve a), Cu(Him)2/CPE (curve b), ILCPE (curve c) and Cu(Him)2/ILCPE (curve d).

Fig. 6
figure 6

CVs of bare CPE (a) Cu(Him)2/CPE (b) ILCPE (c) and Cu(Him)2/ILCPE (d) in exposure to CFX (500.0 nM) at the pH of 5.0 and the scan rate of 50 mV/s

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Figure 6 depicts the anodic peak potential of ~ 880 mV for CFX oxidation on the bare CPE surface (curve a) and 780 mV on the Cu(Him)2/ILCPE surface (curve d). As seen in the curves, the peak potential CFX oxidation on the surface of the modified electrode switched from 100 mV to the negative values in comparison to the surface of the bare electrode. With regard to the CFX oxidation on the surface of Cu(him)2/CPE (curve b) and Cu(Him)2/ILCPE (curve d), the anodic peak current enhanced on Cu(Him)2/ILCPE compared to the Cu(Him)2/CPE, which reveals the greater peak currents by ionic liquids (ILs) presence in the CPE. Researchers have shown several benefits for ILCPE like fast electron transfer, appropriate antifouling features, the catalytic nature of the ILs, as well as greater conductivity. Therefore, we put the IL mass into the paraffin oil and carbon which link the granules and observed that ILCPE conductivity significantly improved that matches our electrochemistry results. With regard to Fig. 6 (curves c & d), the oxidation peak current on the Cu(Him)2/ILCPE surface is higher than that on the Cu(Him)2/CPE surface. Moreover, we observed the Cu(Him)2on IL surface on the electrochemical response, which is possibly caused by the probable features of Cu(Him)2, such as the greater surface area, acceptable electrical conductivity and stronger chemical stability.

3.5 Effect of Scan Rate on the Results

In this step, we addressed the impacts of the rates of potential scan on the CFX oxidation current (Fig. 7) and showed the induced increase of the peak current via enhancing the potential scan rate. Moreover, we monitored diffusion in the oxidation processes, which was shown by linear dependence of the anodic peak current (Ip) on the square root of the potential scan rate (ν1/2).

Fig. 7
figure 7

CVs of Cu(Him)2/ILCPE 0.1 M PBS (pH 5.0) containing 500.0 nM of CFX at various scan rates; 1–9 correspond to 10, 20, 40, 80, 100, 200, 300, 400 and 500 mV s−1, respectively. Inset: variation of anodic peak current with square root of scan rate

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Tafel-plot based on the outputs of the ascending section of the curve for current–voltage registered at the scan rate equal to 10 mVs−1 for CFX as depicted in Fig. 8. The mentioned section that is also called voltammogram referred to the Tafel area has been influenced through the kinetics of electron transfer between Cu(Him)2/ILCPE and the substrate (CFX). Moreover, Tafel slopes of 0.1037 V was observed, showing the consistency with contribution of one electron at the rate determining step of the electrode procedure, assuming the charge transfer coefficient α = 0.43.

Fig. 8
figure 8

LSV (at 10 mV s−1) of a Cu(Him)2/ILCPE in 0.1 M PBS at a pH 5.0 consisting of 500.0 nM CFX. These points represent outputs applied in Tafel plot and inset presents the Tafel plot obtained from LSV

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3.6 Calibration Curve and LOD

It is possible to apply electro-oxidation peak currents of CFX at the surface of Cu(Him)2/ILCPE for CFX detection in the solution. It is well-known that greater sensitivity and specific features for analytical uses have been proposed as the advantages of differential pulse voltammetry (DPV), we utilized Cu(Him)2/ILCPE in 0.1 M PBS of various concentrations of CFX for DPV procedures (Fig. 9) (Step potential = 0.002 V, Modulation Amplitude = 0.02505 V). As seen in the figure, electro-catalytic peak current of the CFX oxidation at the surface of Cu(Him)2/ILCPE has a linear dependence on the CFX concentration above ranges from 2.0 to 1000.0 μM (with a correlation coefficient of 0.9996) whereas LOD (3σ) equalled 0.5 nM. Table 3 presents a comparison of electrochemical techniques for the detection of CFX at the prepared electrode in this work and some other works.

Fig. 9
figure 9

DPVs of Cu(Him)2/ILCPE in 0.1 M PBS (pH 5.0) consisting of various concentrations of CFX. 1–11 relative to 2.0, 7.5, 15.0, 30.0, 75.0, 100.0, 200.0, 400.0 600.0 and 800.0 and 1000.0 μM of CFX, respectively. The inset: the peak current plot as the function of CFX concentrations in ranges from 2.0–1000.0 µM

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Table 3 A comparison of electrochemical techniques for the detection of CFX at the prepared electrode in this work and some other works
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3.7 Real Sample Analysis

We applied this method to detect CFX in urine and CFX ampoule specimens for evaluating the utility of the modified electrode in the real samples. Moreover, we implemented the standard addition method. Table 4 reports the findings. As seen, CFX recoveries are reasonable and generalizability of the results has been shown with regard to the mean relative standard deviation (RSD).

Table 4 Ceftizoxime detection in real specimens via Cu(Him)2/ILCPE. Each concentration is expressed in μM (n = 3)
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4 Conclusion

The present research showed feasible quantification of the CFX concentration at the micromolar level by combining certain catalytic features of IL with the specific features of Cu (Him)2 NPs like a greater surface area in a carbon paste environment. Cu (Him)2/ILCPE sensor showed catalytic impact on the CFX oxidation via elevating its oxidation peak. The linear current response to CFX concentration was obtained to be from 2.0 to 1000.0 μM with a detection limit of 0.5 nM and a sensitivity of 0.0143 μA μM−1. Hence, researchers have designed a more sensitive electro-chemical technique to detect CFX in pharmaceutical and clinical samples. Such an electrode would offer specific advantages over the common electrodes due to easier construction processes, very good catalytic activities, simplicity as well as sensitivity. Hence, Cu(Him)2/ILCPE has shown to be highly promising for potential sensing utilizations.