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Replicative helicases are closed protein rings and require loader proteins for assembly on DNA at origins of DNA replication. Multiple copies of the bacterial DnaC or the phage λP loader proteins bind to the closed planar ring of the DnaB replicative helicase and trigger its reconfiguration into an open spiral conformation wherein an internal chamber becomes accessible for entry to physiologically produced single stranded DNA at the replication origin. Although a great deal was learned from a previously determined cryo-EM structure of theE. coliDnaB helicase bound to the phage helicase loader λP (BP), the pentameric λP ensemble was not well resolved and this stymied deeper insights. We revised have the BP structure using X-ray and AlphaFold determined structures to interpret a 2.8Å cryo-EM density map. We find that the λP ensemble adopts a profoundly asymmetric configuration; one copy of λP, which is visualized in full, binds at the top and bottom of the open DnaB spiral; presence of a single breach in the DnaB open spiral means that the remaining four copies of λP must adopt distinct, and currently unknown, conformations. Although DnaB’s internal chamber remains accessible to entry of ssDNA, the λP protomer whose binding site spans the breach effectively blocks the path into the inner chamber and gives rise to an autoinhibited configuration for the BP complex. Comparisons of the λP and DnaC bound complexes of the DnaB helicase shed new light on how the two loaders, though unrelated in sequence or structure, converged on the same ring-opening mechanism. The autoinhibited conformation of the BP complex suggests structural changes that must accompany recruitment to the initiator protein complex at the replication origin.

This work outlines a simple fabricated microneedle electrode for sensitive and real sample monitoring of plant polyphenolics. The electrode was fabricated by layer-by-layer assembly (LBL) with nanocomposite of carbon nanotubes (CNT) and cellulose nanocrystals (CNC) as the first layer, followed by polyaniline (PANI), and finally, the 3-(glycidyloxypropyl)trimethoxysilane (GOPS) layer as the binding agent. The microneedle electrodes were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The developed microneedle electrodes were successfully applied for the capacitive detection of gallic acid (GA) and chlorogenic acid (CA) as polyphenol model compounds. The microneedle electrode was also used to quantify polyphenols in orange juice. The electrochemical capacitance responses were linearly proportional to the concentrations of GA and CA in the range of 0.1-87.23 μg/mL for GA and 0.1-78.01 μg/mL for CA. The calculated detection limits (LOD) for GA and CA were found to be 0.29 ± 0.2 μg/mL and 0.34 ± 0.2 μg/mL respectively. As minimally invasive technology, microneedle electrodes were found to be promising for successful in situ screening of antioxidants in different fruit matrices. The microneedle electrodes were also applied to the depth profiling of antioxidant content in fruit samples. Graphical abstract.

This paper demonstrates a non-enzymatic biomimetric flexible sweat sensor. Fabricated by multi-layered assembly, the layers comprised a conductive nanoporous carbon nanotube-cellulose nanocrystals (CNC/CNT) porous films entrained with poly (N-isopropylacrylamide) (pNIPAM) based microgel. The pNIPAM microgels based sensor films are effective for detection of ionic strength. The pNIPAM microgels coated with lactate imprinted poly (aniline/phenylboronic acid) (pANI/PBA) moieties switch off their responsivity to NaCl and instead effectively respond to lactate. As such, the printed pNIPAM microgels have been demonstrated as flexible capacitive sensor for multiplex detection of electrolyte (e.g. NaCl) and lactate levels in sweat analysis. The linear concentration range obtained for pNIPAM @CNC/CNT sensor in response to NaCl was 3–80 mM, with a limit of detection (LOD) of 0.23 mM NaCl. The lactate imprinted pANI/PBA- pNIPAM @CNC/CNT sensor resulted in a linear range of 1 mM-25 mM, and a LOD of 0.10 mM, an order of magnitude higher than the non-imprinted form. For both analytes, the sensor precision ranged from 0.5-5.0%, indicative of the overall reliability and validity. The fabricated flexible sensors were demonstrated to be effective in quantitation of electrolytes (principally NaCl) and lactate in a real sweat sample.

In spite of single nanomaterials, nanocomposites have come to be the superior modifying materials for electrochemical sensing. Herein, the highly sophisticated and sensitive voltammetric sensor of polypyrrole/cerium oxide/glassy carbon electrode (Ppyr/CeO2/GCE) has been fabricated for the electrochemical analysis of flupirtine maleate (FPM). Prior to the fabrication, the synthetic Ppyr/CeO2 material and its constituents viz., Ppyr and CeO2 were spectrally characterized by FTIR, XRD, and SEM to confirm the successful synthesis. After the fabrication of the Ppyr/CeO2/GCE sensor, it together with its corresponding forms i.e., CeO2/GCE and Ppyr/GCE including bare GCE was characterized by voltammetry and electrochemical impedance spectroscopy (EIS). The electrode characteristics such as charge transfer resistance, heterogeneous electron transfer (HET) rate constant, ($$k_{{{\text{eff}}}}^{0}$$) and surface area suggest that the designed electrochemical sensor has got the conductivity (sensitivity) par excellence as compared to CeO2/GCE, Ppyr/GCE and bare GCE. The fabricated probe after characterization was optimized for the detection of the FPM by voltammetry and found to show a direct correlation between the oxidation current and the FPM concentration varying from 100 ng mL−1 to 500 ng mL−1 having correlation coefficient (r2) of 0.9940. By measuring the calibration curve, the fabricated Ppyr/CeO2/GCE sensor was found to reach the minimum limit of detection (LOD) i.e., 26.76 ng mL−1 and minimum limit of quantification (LOQ) i.e., 89.20 ng mL−1, for FPM, thereby showing the sensitivity par excellence in terms of conductivity. Fabrication of Ppyr/CeO2/GCE voltammetric sensor

The present study demonstrates the use of highly stable single-molecule enzyme nanocapsules (SMENs) instead of traditional native enzyme as biorecognition element in enzyme-based biosensors. The main purpose of this study is to resolve the major obstacle and challenge in the biosensor field, i.e., the poor stability of enzyme-based biosensors, including thermal stability, organic solvent tolerance, long-term operational stability, etc. Highly active and robust SMENs of glucose oxidase (GOx, as a model enzyme) were synthesized (nGOx) using an in situ polymerization strategy in an aqueous environment. The particle-size distribution, transmission electron microscopic (TEM) images, and UV-vis spectral characterization revealed the formation of a thin polymer layer around each enzyme molecule. The polymer shell effectively stabilized the GOx enzyme core while enabling rapid substrate transportation, resulting in a new class of biocatalytic nanocapsules. Multiple covalent attachments between a thin polymer layer and an enzyme molecule strengthened the encapsulated GOx molecule. Encapsulation created a favorable microenvironment to avoid any structural dissociation at high temperature and helped to retain essential water during the organic solvent operation. The present work reports a study implementing nGOx SMENs as highly stable nano(bio)sensors for point-of-care diagnostic applications. Prepared nGOx SMENs manifested significantly improved thermal stability (even at 65 °C) and organic solvent tolerance without any compromise in biocatalytic activity. For example, the native GOx-based biosensor lost its catalytic activity for glucose after 4 h of incubation at high temperature (65 °C), while the nGOx/N-CNTs-Chi/GCE nano(bio)sensor maintained ∼56% of its original catalytic activity for glucose oxidation. The proposed SMENs-based nano(bio)sensors with robust stability in variable working environment could promote the development and applications of biosensors in point-of care diagnostics, biomedical detection, wearable devices, implantable equipment, and biofuel cells.

Graphdiyne (GDY), a new two-dimensional all-carbon allotrope composed of benzene rings and alkyne unites, was successfully synthesized via a crossing-coupling reaction with much intriguing properties especially highly π-conjugated structure, attractive electronic and chemical properties, good biocompatibility and dispersion in aqueous solution. The as-prepared graphdiyne was explored for the first time as an extremely attractive matrix for tyrosinase (a model enzyme) immobilization to construct a mediator-free GDY-based biosensor for rapid detection of bisphenol A (BPA). The response of GDY-based tyrosinase biosensor is linear over the range of 1.0 × 10−7 to 3.5 × 10−6 mol L−1 with a high sensitivity of 2990.8 mA cm−2 M−1 and a low detection limit of 24 nmol L−1. The proposed GDY-based tyrosinase biosensor exhibited better analytical performances for BPA detection than CNTs and graphene based biosensors. The excellent performance of the biosensor should partially be ascribed to the strong π-π interactions between graphdiyne and BPA, which could enrich available BPA concentration on the electrode to react with tyrosinase. The robust GDY-based tyrosinase biosensor was used for BPA detection in drinking bottles and tap water with satisfactory results. As a new 2D all-carbon nanomaterial, graphdiyne is proved to be a powerful electrochemical enzyme biosensor platform for biomolecules (as recognition elements) immobilization and biosensor fabrication, and provides great application prospect for biomedical detection and environmental analyses.

This article demonstrates a non-enzymatic biomimetic adrenaline capacitive sensor fabricated inexpensively by layer-by-layer (LbL) assembly. The LbL assembly consists of polydimethylsiloxane (PDMS) substrate, carbon nanotube-cellulose nanocrystals (CNC/CNT) nanofilms (first layer) with adrenaline imprinted poly (aniline/phenylboronic acid) (pANI/PBA) moieties (second layer). The flexible sensor has been effectively demonstrated for high sensitivity and selectivity in capacitive detection of adrenaline standard and adrenaline in real zebra fish brain sample. The molecularly imprinted adrenaline sensor exhibited linear response between 0.001 μM and 100 μM with a correlation coefficient of 0.9738 and detection limit (LOD) of 0.001 μM. The developed sensor demonstrated high adrenaline selectivity and good sensor to sensor reproducibility of 15.7% for molecularly imprinted films. The sensor precision for triplicate standard runs for different adrenaline concentrations ranged from 0.5 to 5.0%, indicative of the overall reliability and validity of the device. The inexpensive sensor remains stable over time, responding proportionately to doses of adrenaline, and as such effective as a dosimetric sensor for near real time continuous monitoring. Frugal in sample consumption (50 μL), the study suggested the practical utilization of the developed biosensor towards adrenaline detection in biological fluids.

The present work reports the preparation of advanced functional nanostructures based on cobalt oxide supported mesoporous carbon framework (Co3O4@MCF) for electrochemical biosensing. Co3O4@MCF was synthesized by simple hythrothermal & pyrolysis method and further characterized by various microscopic and spectroscopic techniques. The transmission electron microscopic (TEM) images show the lattice fringes of crystalline Co3O4 with interlayer spacing of 0.24 nm. The characteristic 311 plane in X-ray diffraction (XRD) studies further confirmed the presence of crystalline Co3O4 on carbon frameworks. Reflection of prominent A1g peak along with D and G band in raman spectra confirmed the successful fabrication of Co3O4@MCF nanocomposite. Prepared Co3O4@MCF manifested great porosity, good biocompatibility and large surface area which allowed effective immobilization of glucose oxidase (GOx) onto its surface using chitosan (Chi) as a binder. Thus, a nanocomposite (Co3O4@MCF-Chi-GOx) modified glassy carbon electrode (GCE) was fabricated for highly selective detection of glucose using amperometry and cyclic voltammetry. The Co3O4@MCF-Chi-GOx/GCE electrode exhibited excellent biosensing performance for glucose monitoring with detection limit of (LOD) of 107.70 μM and reproducibility of 4.7% RSD. Moreover, the biosensor holds great promise for its effective implications in point-of-care diagnostics of small biomolecules.

Hydrogels are hydrophilic polymeric networks prepared by physical or chemical cross-linking of gelator molecules under optimum conditions. Being sensitive to external stimuli, hydrogels are integrated into signal transduction systems for generating possible responses upon interaction with target analytes to study various physiochemical/biochemical molecular recognition processes. In recent times, polymer based hydrogel materials have emerged as unique electrode modifying materials providing highly permeable matrix for easy diffusion of analytes and rapid electron transport. Polymeric architectures of hydrogels can accommodate different nanomaterials within its matrix through suitable interactions to form hydrogel nanocomposites. Further, high biocompatibility of hydrogels facilitates facile encapsulation and cross-linking of bioreceptors (eg. nucleic acid, protein) into polymer matrix and helps to retain their bioactivity during practical applications. Polymer hydrogel materials enable easy prototyping of electrodes using novel printing technologies for designing next generation advanced, flexible and portable bioelectronics with excellent sensing performances. The present article focuses on the implication of polymer hydrogels as high performance electrode materials. Taking relevant examples, nanomaterials incorporated polymer hydrogel based chemical sensors and bioreceptors embedded biosensors have been discussed for electrochemical detection of different analytes. Preparation of hydrogel modified electrodes and state-of-the-art sensing mechanisms have been briefly emphasized. Concluding remarks and future prospects regarding fabrication of hydrogel based smart electronics have been provided at the end.

Core-shell nanomaterials (CSNs) have achieved huge popularity due to multifunctional properties achieved by manipulation of core or shell materials. This review highlights recent development in CSNs based sensing devices such as electrochemical sensors, optical sensors, wearable sensing devices, and gas adsorptive sensors, which find potential applications in numerous fields ranging from industrial, clinical, biological, environmental and food analysis. Furthermore, flexible and high deformation monitoring piezoresistive wearable sensors based on CSNs are found to be promising for monitoring of human physiological parameters and other body movements. Various synthetic strategies with a modern classification approach are explained with suitable examples. Several interesting properties of CSNs including high surface area, high conductivities, and high ion transport properties with biocompatibilities are best suited for developing ideal sensing devices. Future research directions with motivated research are highlighted in the conclusion part.

The novel tetraazo-bridged cobalt phthalocyanine polymer [poly(TazoCoPc)] was synthesized by oxy-bridge to extend the conjugation effect on the phthalocyanine molecule. Firstly, the ligand [phenyl-1,4-bisdiazenyl naphthalene-1-oxy] benzene 1,2-dicarbonitrile was prepared and it was characterized. Then, the polymeric phthalocyanine was prepared and characterized by elemental analysis, UV–vis, FTIR, TGA, XRD and electrochemistry. Polymeric phthalocyanine and carbon nanoparticles (CNP) were mixed and used for modifying the glassy carbon electrode to fabricate the electrochemical voltametric and amperometric nitrite sensor. Composite of phthalocyanine polymer and CNP exhibits enhanced electrocatalytic behaviour for the oxidation of nitrite compared to pure polymeric phthalocyanine. The fabricated amperometric sensor exhibits excellent analytical performance for nitrite detection in the concentration range of 20 nM to 1 μM with a detection limit of 6 nM (S/N = 3) and a sensitivity of 0.137 mA/μM. The modified composite electrode is highly selective and it didn’t show any interference effect even in presence of excess interfering ions such as Mg2+, SO42−, K+, CO32−, NO3-.

MXenes have been recognized as one of the amazing two-dimensional layered materials with unique layered morphology. This extraordinary material includes carbides, nitrides, and carbonitrides of early transition metal synthesized by exfoliation of selective MAX phases. MAX phase stands for Mn+1AXn, (MAX) where n is an integer 1, 2, or 3, M is an early transition metal, A is group 13 and 14 elements, and X is either carbon or nitrogen. MXenes have emerged as highly advanced sensing platforms, which can be ascribed to their high metallic conductivity, ion-transport properties, biocompatibility, large surface area, and ease of functionalization. MXene-based various sensors and biosensors have been now developed, which have contributed significantly in the field of healthcare monitoring, pollution affairs, security operations, and robotics and prosthetic devices. This chapter will include the application of MXene as ultraadvance detection interface in sensing applications. Owing to their superior sensing performances, an impressive research is highly anticipated in near future establishing MXene as next-generation sensing material.

Molecularly imprinted polymer was constructed for the first time through dummy imprinting strategy with homopiperonylamine as dummy template. The prepared dummy molecularly imprinted polymer (DMIP) showed high class selectivity towards the most popular amphetamine-type stimulants (ATSs) such as methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxy-amphetamine, and 3,4-methylenedioxy-N-ethylamphetamine with the imprinting factors of 2.280∼3.698 and selectivity factors of 1.654∼3.698. Moreover, ATSs could be rapidly adsorbed from water with the equilibrium time within 5 min. Hydrogen-bonding interaction between the amino groups of ATSs and carboxy on DMIP could be dominated adsorption mechanism. DMIP was employed as solid phase extraction (SPE) sorbents. Under the optimum extraction conditions, the method using DMIP-based SPE and high performance liquid chromatography-tandem mass spectrometry showed good linearity in the range of 0.025∼1.00 μmol L

Engineering the growth of MOFs on substrates at the nanometer or even the molecular level is of major interest for taking MOFs beyond their uses as bulk materials and creating multifunctional features with advanced applications. Herein we report the SiO2@ZIF-8 (core@shell) monodisperse nanospheres synthesized through a liquid-phase epitaxy stepwise growth (LPE) strategy. The controlled growth of ZIF-8 shell with nanometer-level precision could be achieved. The growth of the ZIF-8 shell can be adjusted by manipulating the influencing factors, such as growth circles, precursor solvent, precursor concentration, core size, synthesis temperature and implementation methods. The formation processes of ZIF-8 shell on the SiO2 surface using different precursor solvents were also deduced. The composite exhibited faster adsorption for bisphenol A with ultra-high adsorption capacity per unit ares compared to ZIF-8-only material. Such controlled growth of homogeneous ZIF-8 shell with nanometer-level precision is of paramount importance for the success of fabricating ZIFs layers in the channels ofmesoporous materialics. Further, this paves the way for integrated MOF materials to address a wide range of challenges in the areas of catalysis, rapid detection, adsorption and separation.

MXene has emerged as an amazing family of two dimensional (2D) layered materials and drawn great attention from researchers of diverse scientific fields. MXenes are the recent advancements of materials chemistry which include early transition metal carbides, nitrides and carbonitrides produced by exfoliation of selective MAX phases. MAX phase corresponds to the general formula Mn+1AXn (n = 1, 2, 3) where M represents early d-block transition metals, A stands for main group sp elements (specifically groups 13 and 14) and X is either C or N atoms. MXenes have left a prodigious impact on scientific communities with new technological advancements for a plethora of potential applications in the field of catalysis, clean energy, electronics, fuel cells, supercapacitors etc. With high metallic conductivity, hydrophilicity, low diffusion barrier, high ion transport properties, biocompatibility, large surface area and ease of functionalization, the MXenes act as fascinating interface for designing next generation detection systems exploiting their utilization in analytical chemistry. Recent progress in the field of MXenes emphasizing their significant role in analytical sensing has been well discussed in this review. Future perspectives with a motivated research in the field of MXenes based sensors have been focused at the end. The underlying goal of this review is to acquaint the readers with the sensing applications of MXenes and to document the latest advancements made in this area till date.

MXene-Ti 3 C 2 , as a new class of two-dimensional (2D) transition metal carbides (or nitrides), has been synthesized by exfoliating pristine Ti 3 AlC 2 phases with hydrofluoric acid. The SEM and XRD images show that the resultant MXene possesses a graphene-like 2D nanostructure. and the surface of MXene has been partially terminated with -OH, thus providing a favorable microenvironment for enzyme immobilization and retaining their bioactivity and stability. Considering the unique metallic conductivity, biocompatibility and good dispersion in aqueous phase, the as-prepared MXene was explored as a new matrix to immobilize tyrosinase (a model enzyme) for fabricating a mediator-free biosensor for ultrasensitive and rapid detection of phenol. The varying electrochemical measurements were used to investigate the electrochemical performance of MXene-based tyrosinase biosensors. The results revealed that the direct electron transfer between tyrosinase and electrode could be easily achieved via a surface-controlled electrochemical process. The fabricated MXene-based tyrosinase biosensors exhibited good analytical performance over a wide linear range from 0.05 to 15.5 μmol L −1 , with a low detection limit of 12 nmol L −1 and a sensitivity of 414.4 mA M −1 . The proposed biosensing approach also demonstrated good repeatability, reproducibility, long-term stability and high recovery for phenol detection in real water samples. With those excellent performances, MXene with graphene-like structure is proved to be a robust and versatile electrochemical biosensing platform for enzyme-based biosensors and biocatalysis, and has wide potential applications in biomedical detection and environmental analysis.

As one of the most important analytical techniques for accurate quantification of bisphenol compounds, liquid chromatography coupled to online electrospray ionization (ESI) tandem mass spectrometry exhibits relative weak ESI response in negative mode, which greatly reduces their sensitivity and limits their detection at trace levels, especially in complex samples such as blood. Based on the facilitated deprotonation of bisphenol molecule under alkaline condition, post-column injection of ammonium hydroxide (NH3·H2O) to mass spectrometer was explored to enhance the ionization efficiency of BPA and its eight analogs and improve their analytical sensitivity. Parameters effecting response intensity and stability were investigated, including mass concentration and flow rate of NH3·H2O. Under the optimal conditions with the addition of 2% (w/w) of NH3·H2O at 4 μL min−1, the instrument detection limits for bisphenol compounds were greatly lowered to 0.001–0.04 ng mL−1, which were 2–28.6 times lower than the result obtained without injecting NH3·H2O, except TBBPA (0.03 ng mL−1 in either case). The relative standard deviations (RSDs) for instrument repeatability of BPA and its analogs at three different concentration levels were in a range of 1.2–20%. Furthermore, a decreased matrix effects (90–111%) for bisphenols (except TBBPA) analysis in serum extracts were found compared with the result obtained without NH3·H2O injection (43–111%). The results demonstrated that the improved instrumental method coupled with suitable pretreatment techniques is more feasible to analyze bisphenol compounds in complex bio-samples.

With the emerging interest in layered transition metal dichalcogenides (TMDs), MoS2 has occupied a unique place in recent times as graphene (GR) analog. Development of novel state of the art electrochemical approaches at MoS2 modified working surfaces is an upcoming field and holds great promise for design and development of next generation sensing devices. Large available surface area, high biocompatibility and structural versatility of 2D/3D MoS2 nanostructures have produced numerous hybrid sensors and biosensors which have demonstrated their prominent role in biological, environmental, pharmaceutical, chemical, industrial and food analysis. A comprehensive and critical detail of recent advancements of MoS2 based sensors for real time applications have been presented in the present review. Overall conclusion related to sensing performances of MoS2 nanostructures and future needs to further exploit the unusual properties of mono and few layer of other TMDs for developing advance recognition systems have been concluded at the end.

Biomolecules are integral constituents of living beings which regulate numerous biochemical functions of the body. Analysis of various small molecules (metabolites, neurotransmitters, amino acids, vitamins) and macromolecules (nucleic acids, proteins) is of prime importance in modern time due to increasing disbalance in natural metabolism of human body. Irregularities and alteration in concentration of biomolecules lead to different kinds of genetic, metabolic and cancerous diseases which have created a great requirement of highly sensitive, accurate and stable detection systems for their quick and specific screening. In this review, redox interactions of biomolecules at carbon based electrode interfaces have been discussed using voltammetry. It is divided into subsections, starting with an introduction into the field and a description of its current state. This is followed by a large section describing carbon nanomaterials (CNs) based voltammetric sensors for different small biomolecules and macromolecules. The next section of the review gives conclusion, challenges and future perspectives in sensing biomolecules at CNs based electrodes. Advanced approaches for fabrication of portable integrated electrochemical devices for various point of care diagnostic applications have also been included at the end.

New multi-walled carbon nanotubes supported on Ti3C2–MXene and chitosan (chit) composite film–based electrochemical sensor for ifosfamide (IFO), acetaminophen (ACOP), domperidone (DOM), and sumatriptan (SUM) have been developed. Ti3C2–MXene was synthesized by a fluoride method. Structural and chemical characterizations suggested the successful preparation of Ti3C2–MXene with clearly seen layered morphology, defined 0 0 2 diffraction peak at 7.5° and complete absence of 1 0 4 plane at 39°. The electrochemical performance of the sensor was investigated by cyclic voltammetry and adsorptive stripping differential pulse voltammetry. The Ti3C2/MWCNT/Chit modified glassy carbon electrode exhibits enhanced electrocatalytic activities toward the oxidation of target analytes. Excellent conductivity, large surface area, and high catalytic properties of the Ti3C2–MXene showed synergistic effects with MWCNTs and helped in achieving low detection limits of targets with high selectivity and reproducibility. The assay allows determination of IFO, ACOP, DOM, and SUM in the concentration ranges 0.0011–1.0, 0.0042–7.1, 0.0046–7.3, and 0.0033–61 μM with low detection limits of 0.00031, 0.00028, 0.00034, and 0.00042 μM, respectively. The sensor was successfully applied for voltammetric screening of target analytes in urine and blood serum samples with recoveries > 95.21%. Schematic illustration of the synthesis of self-assembled MXene/MWCNT/chitosan nanocomposite is given and its application to the voltammetric determination of ifosfamide, acetaminophen, domperidone, and sumatriptan described.