Detection of hydrazine, methylhydrazine, and isoniazid by capillary electrophoresis with a palladium-modified microdisk array electrode

Phenothiazine-based fluorescent probes for the detection of hydrazine in environment and living cells

As an important chemical raw material, hydrazine brings convenience to people's lives and provides opportunities for human development. However, the misuse or leakage of hydrazine has brought pollution to the environment, including water, soil and living organisms. At the same time, hydrazine poses a potential threat to human health as a carcinogen. Despite the enormous challenges, it is crucial to develop an effective method to detect hydrazine in environmental samples. In this work, we have synthesized a series of probes based on phenothiazine fluorophore by the introduction of different substituents and developed a novel probe for the detection of hydrazine. The probe is capable of detecting hydrazine in aqueous solutions with high sensitivity and selectivity, and can be easily fabricated into paper test strips for use in in situ samples. In addition, the probe is effective in detecting hydrazine in water, soil, cells, and zebrafish, providing an excellent tool for detecting hydrazine in the environment.

Unique Reaction-Based Polynorbornene Sensing Probes for Ultrasensitive Detection of Hydrazine in Both Environmental and Biological Systems

Hydrazine-mediated formation of 1,4-phthalazinedione analogues from phthalimide-like components has been utilized to formulate fluorescent probe NorTh. A turn-on fluorescent process has been evaluated to detect hydrazine in a highly selective manner by a small molecular probe NorTh and its homopolymer Poly-NorTh. Both these probes have been evaluated as excellent candidates for nanomolar level detection of hydrazine with a time frame of <15 min, which is rapid in terms of real application. Due to the reaction-based detection process, we have achieved high selectivity for our probes toward the identification of hydrazine in the presence of metal ions, anions, amino acids, and various amines. Limit of detection values are 16 and 35 nM for NorTh and Poly-NorTh, respectively, which are well below the permissible limit given by WHO and EPA. Poly-NorTh has been utilized to detect hydrazine in environmental water samples, soil samples, and biological samples to establish the applicability of our probes in real-field scenarios. We introduce an easy-to-synthesize, cheap, and small molecular probe and its polymer for ultrafast, highly selective, and sensitive detection of hydrazine in all possible mediums to counter the hydrazine toxicity through fluorescence turn-on signal output.

InterDILI: interpretable prediction of drug-induced liver injury through permutation feature importance and attention mechanism

Safety is one of the important factors constraining the distribution of clinical drugs on the market. Drug-induced liver injury (DILI) is the leading cause of safety problems produced by drug side effects. Therefore, the DILI risk of approved drugs and potential drug candidates should be assessed. Currently, in vivo and in vitro methods are used to test DILI risk, but both methods are labor-intensive, time-consuming, and expensive. To overcome these problems, many in silico methods for DILI prediction have been suggested. Previous studies have shown that DILI prediction models can be utilized as prescreening tools, and they achieved a good performance. However, there are still limitations in interpreting the prediction results. Therefore, this study focused on interpreting the model prediction to analyze which features could potentially cause DILI. For this, five publicly available datasets were collected to train and test the model. Then, various machine learning methods were applied using substructure and physicochemical descriptors as inputs and the DILI label as the output. The interpretation of feature importance was analyzed by recognizing the following general-to-specific patterns: (i) identifying general important features of the overall DILI predictions, and (ii) highlighting specific molecular substructures which were highly related to the DILI prediction for each compound. The results indicated that the model not only captured the previously known properties to be related to DILI but also proposed a new DILI potential substructural of physicochemical properties. The models for the DILI prediction achieved an area under the receiver operating characteristic (AUROC) of 0.88-0.97 and an area under the Precision-Recall curve (AUPRC) of 0.81-0.95. From this, we hope the proposed models can help identify the potential DILI risk of drug candidates at an early stage and offer valuable insights for drug development.

Orthogonal Chemical Reporter Strategy Enables Sensitive and Specific SERS Detection of Hydrazine Derivatives

Hydrazine and its derivatives are well-known environmental hazards and biological carcinogens; therefore, there is a great need for a powerful workflow solution for protecting the public from unexpected exposure to toxic contaminants. Recently, functional surface-enhanced Raman scattering (SERS) exhibits enormous benefits in sensing trace biochemical substances due to its fingerprint-like identification of individual molecules, making it an ideal method for detecting and quantifying hydrazine. Herein, for the first time, we integrated the orthogonal chemical reporter strategy with SERS to build an intelligent hydrazine detection platform (orthogonal chemical SERS, ocSERS), in which 4-mercaptobenzaldehyde was incorporated on a nanoimprinted gold nanopillar array, which acted as an orthogonal coupling partner of hydrazine to form Raman active benzaldehyde hydrazone, allowing for sensitively detecting hydrazine with a detection limit of 10^-13 M in complex circumstances. Particularly, ocSERS could effectively identify the carcinogen N-nitrosodimethylamine (NDMA) after its reduction to dimethylhydrazine (UDMH), enabling ultrasensitive detection of UDMH (10^-13 M). Importantly, ocSERS could not only monitor elevated levels of NDMA in ranitidine due to improper storage but also quantify NDMA in urine and blood after oral administration of NDMA-containing drugs, thereby preventing NDMA overexposure. Therefore, ocSERS represents the first click SERS sensor and may open up a new analytical field.

Substituent derivatives of benzothiazole-based fluorescence probes for hydrazine with conspicuous luminescence properties: A theoretical study

In the present work, four probe molecules for detecting hydrazine have been designed based on the 2-(4-Acetoxy-3-benzothiazole-2-yl-phenyl)-4-methyl-thiazole- 5-carboxylic acid ethyl ester (HP1) to investigate the influence of the amino and cyano groups on the excited-state intramolecular proton transfer (ESIPT) behavior and photophysical properties. The changes in hydrogen bond strength indicate that the intramolecular hydrogen bond of all probe products is enhanced upon photoexcitation. Frontier molecular orbitals (FMOs) and natural bond orbital (NBO) reveal the driving force of ESIPT. In addition, the potential energy curves and transition state theory explain the reason for the single fluorescence phenomenon in the experiment. The simulated absorption and fluorescence spectra of HP1 and its product (HPP1) are completely consistent with the experimental results, which also verify the viewpoint. Meanwhile the cyano derivative HPP4 exhibits a larger Stokes-shift (201 nm) than that of HPP1 (145 nm) and has the same low energy barrier as HPP1. These excellent properties allow HPP4 to be a fluorescent probe with superior performance than the original molecule. In conclusion, this work can provide a theoretical basis for the design and synthesis of more sensitive fluorescent probes for the detection of hydrazine.

A new ratiometric switch "two-way" detects hydrazine and hypochlorite via a "dye-release" mechanism with a PBMC bioimaging study

A new ratiometric fluorescent probe (E)-2-(benzo[d]thiazol-2-yl)-3-(8-methoxyquinolin-2-yl)acrylonitrile (HQCN) was synthesised by the perfect blending of quinoline and a 2-benzothiazoleacetonitrile unit. In a mixed aqueous solution, HQCN reacts with hydrazine (N₂H₄) to give a new product 2-(hydrazonomethyl)-8-methoxyquinoline along with the liberation of the 2-benzothiazoleacetonitrile moiety. In contrast, the reaction of hypochlorite ions (OCl^-) with the probe gives 8-methoxyquinoline-2-carbaldehyde. In both cases, the chemodosimetric approaches of hydrazine and hypochlorite selectively occur at the olefinic carbon but give two different products with two different outputs, as observed from the fluorescence study exhibiting signals at 455 nm and 500 nm for hydrazine and hypochlorite, respectively. A UV-vis spectroscopy study also depicts a distinct change in the spectrum of HQCN in the presence of hydrazine and hypochlorite. The hydrazinolysis of HQCN exhibits a prominent chromogenic as well as ratiometric fluorescence change with a 165 nm left-shift in the fluorescence spectrum. Similarly, the probe in hand (HQCN) can selectively detect hypochlorite in a ratiometric manner with a shift of 120 nm, as observed from the fluorescence emission spectra. HQCN can detect hydrazine and OCl^- as low as 2.25 × 10^-8 M and 3.46 × 10^-8 M, respectively, as evaluated from the fluorescence experiments again. The excited state behaviour of the probe HQCN and the chemodosimetric products with hydrazine and hypochlorite are studied by the nanosecond time-resolved fluorescence technique. Computational studies (DFT and TDDFT) with the probe and the hydrazine and hypochlorite products were also performed. The observations made in the fluorescence imaging studies with human blood cells manifest that HQCN can be employed to monitor hydrazine and OCl^- in human peripheral blood mononuclear cells (PBMCs). It is indeed a rare case that the single probe HQCN is found to be successfully able to detect hydrazine and hypochlorite in PBMCs, with two different outputs.

A dual-mode visual detector for toxic hydrazine

Hydrazine (N₂H₄) is one of the commonly used chemical reagents in numerous industries and applications but its toxicity to humans poses a need to develop simple visual detection methods. Herein, we demonstrate a novel dual-mode system to detect and simultaneously consume hydrazine in vapour and solution by using a small photoresponsive molecule that has altered optical response (both colourimetric and fluorescent) after reacting with hydrazine.

A small photoresponsive molecule changes colour from blue to colourless when exposed to hydrazine vapours. It also becomes emissive providing two convenient ways of detecting the presence of this toxic chemical.

Identification of amphetamine as a stimulant drug by pristine and doped C70 fullerenes: a DFT/TDDFT investigation

The density functional theory (DFT) was used to examine the electronic reactivity and sensitivity of a pristine, Si, and Al-doped fullerene C₇₀ with AM drug. AM drug has been shown to be physically absorbed by its N-head on the pristine C₇₀ with an adsorption energy of about - 1.09 kcal/mol and to have no impact on the electric conductivity of that cluster. The atom substitution of Si and Al for C atoms at C₇₀ significantly increases C₇₀ fullerene reactivity, with adsorption energy predictions of approximately - 31.09 and - 45.59 kcal/mol, respectively. The energy difference of LUMO and HOMO, i.e., Eg from C₇₀ fullerene, significantly affects AM drug. Significant LUMO destabilization in Al-C₇₀ by adsorption of the drug AM boosts the electrical conductivity of Al-C₇₀ while generating electric signals that are related to the environmental presence of AM drug. Hence, Al-doped C₇₀ is demonstrated to be an effective electronic AM drug sensor. In contrast to Si-C₇₀ fullerene, significant AM-drug adsorption effects on Fermi and Si-C₇₀ work functions make Si-C₇₀ an Ф-type candidate for AM drug sensor applications. The time-dependent theory of the functional density shows that the AM/Al-C₇₀ complex is steadily situated at a maximum peak of 784.15 nm.

Colorimetric recognition of hydrazine in aqueous solution by a bromophenol blue-tethered ion-pair-like ratiometric probe

Hydrazine or hydrazine hydrate (N₂H₄·H₂O) is a potential neurotoxin and has several mutagenic effects in physiological systems. Therefore, the development of synthetic organic probes that are sensitive and selective to hydrazine is of tremendous importance. Unfortunately, however, the hydrazine-selective sensing probes that rely upon minimum usage of the organic solvents (≤5%, v/v) are still rarer. In this work, an ion-pair-like mono acetate derivative of bromophenol blue has been developed as a fairly selective ratiometric probe for the naked-eye recognition of hydrazine in a solution of tris buffer and EtOH (19:1, v/v) at physiological pH. The chromogenic signalling relies upon hydrazine-induced cleavage of an ester moiety of the probe to its resonance stabilized quinonoid form, resulting in momentous variations in its spectrophotometric profile. Meanwhile, the colour of the probe solution changed from mustard yellow to blue within few minutes. This sensing assay could be successfully applied in the recognition of hydrazine in real environmental and pharmaceutical samples with satisfactory recoveries. Given the cost-effectiveness, simplicity and versatility, for instance, direct analysis of colorimetric probes, it is reasonable to propose that the present method can serve as a complementary method for prompt inspection of hydrazine in boiler feed water.

Electrochemical Detection of Hydrazine by Carbon Paste Electrode Modified with Ferrocene Derivatives, Ionic Liquid, and CoS2-Carbon Nanotube Nanocomposite

The electrocatalytic performance of carbon paste electrode (CPE) modified with ferrocene-derivative (ethyl2-(4-ferrocenyl[1,2,3]triazol-1-yl)acetate), ionic liquid (n-hexyl-3-methylimidazolium hexafluorophosphate), and CoS2-carbon nanotube nanocomposite (EFTA/IL/CoS2-CNT/CPE) was investigated for the electrocatalytic detection of hydrazine. CoS2-CNT nanocomposite was characterized by field emission scanning electron microscopy, X-ray powder diffraction, and transmission electron microscopy. According to the results of cyclic voltammetry, the EFTA/IL/CoS2-CNT-integrated CPE has been accompanied by greater catalytic activities for hydrazine oxidation compared to the other electrodes in phosphate buffer solution at a pH 7.0 as a result of the synergistic impact of fused ferrocene-derivative, IL, and nanocomposite. The sensor responded linearly with increasing concentration of hydrazine from 0.03 to 500.0 μM with a higher sensitivity (0.073 μA μM-1) and lower limit of detection (LOD, 0.015 μM). Furthermore, reasonable reproducibility, lengthy stability, and excellent selectivity were also attained for the proposed sensor. Finally, EFTA/IL/CoS2-CNT/CPE was applied for the detection of hydrazine in water samples, and good recoveries varied from 96.7 to 103.0%.

A xanthene-based novel colorimetric and fluorometric chemosensor for the detection of hydrazine and its application in the bio-imaging of live cells

An efficient xanthene-based colorimetric and fluorometric probe (MXI) for the selective detection of hydrazine in solution and in living cells.

Rational design of a novel turn-on fluorescent probe for the detection and bioimaging of hydrazine with barbituric acid as a recognition group

A novel turn-on fluorescent probe with barbituric acid as a unique recognition group has been rationally designed and synthesized using a facile method for detecting hydrazine.

Rapid switch-on fluorescent detection of nanomolar-level hydrazine in water by a diacetoxy-functionalized MOF: application in paper strips and environmental samples

A diacetoxy-functionalized Zr-based metal–organic framework was employed for the selective, ultra-sensitive, turn-on fluorescent detection of hydrazine in an aqueous medium.

A New Fluorescent Turn-on Dual Interaction Position Probe for Determination of Hydrazine

Hydrazine is an important catalyst and chemical raw material. But it is highly toxic and potentially carcinogenic. We designed a new hydrazine probe based on a synergistic effect by introducing acetate and phthalimide into 2-phenyl-benzimidazole (PBI). Comparative experiments proved that "the dual position interaction" had a "synergistic effect" on fluorescence enhancement. The fluorescence enhancement caused by the probe (15.0 fold) is much larger than the sum of the fluorescence enhancement of the two monomer compounds (2.6 and 1.4 folds, respectively). A theoretical calculation showed an inhibition of the PET process and a recovery of the ICT process led to a fluorescence enhancement. The probe was specific to hydrazine and showed a linear response to it in the concentrations range of 0.2 - 200 μM with a LOD of 0.062 μM (1.99 ppb). Moreover, the probe could detect hydrazine in tap water; the recovery of hydrazine from the tap water was between 98.86 - 103.28%.

Graphite/Ag/AgCl nanocomposite as a new and highly efficient electrocatalyst for selective electroxidation of oxalic acid and its assay in real samples

Herein, graphite/Ag/AgCl nanocomposite is introduced as a new electrocatalyst material for the electrocatalytic oxidation of oxalic acid. Graphite/Ag/AgCl was synthesized by electroless deposition of nano-sized metallic silver and then silver chloride on graphite powder. The material obtained was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Energy-dispersive X-ray spectroscopy. The nanocomposite was mixed with n-eicosane as binder and used as carbon paste electrode for electrocatalytic oxidation of oxalic acid (OA). The graphite/Ag/AgCl nanocomposite electrode showed good catalytic activity for the electroxidation of oxalic acid in H₃PO₄ solution (0.05 mol L^-1), leading to a distinct decrease in anodic overpotential (100 mV) and a substantial increase in anodic peak current (about 10 times), in comparison with the unmodified carbon paste electrode. Using the developed nanocomposite electrode and differential pulse voltammetry method, it became possible to determine oxalic acid in the concentration range of 0.01-0.75 mmol L^-1 with detection limit of 3.7 × 10^-6 mol L^-1. The electrode showed very high sensitivity of 1341.3 μA mM^-1 cm^-2 which is remarkably better than the previously reported oxalic acid sensors. Thanks to high sensitivity and good selectivity of the electrode, the proposed method was successfully applied for the determination of OA in human urine and spinach samples. The satisfactory results obtained, confirmed the applicability of this sensor in the practical analysis.

Turn-on fluorescence sensing of hydrazine using MnO2 nanotube-decorated g-C3N4 nanosheets

The cost and time efficient preparation strategy is developed for the preparation of g-C₃N₄ nanosheets using urea and the challenges of g-C₃N₄ toward hydrazine sensing are addressed via the modification of g-C₃N₄ nanosheets with MnO₂ nanotubes.

A coumarin chalcone ratiometric fluorescent probe for hydrazine based on deprotection, addition and subsequent cyclization mechanism

A coumarin chalcone derivative with a levulinic acid terminal group acts as a ratiometric fluorescent probe for hydrazine based on deprotection, addition and a subsequent cyclization reaction mechanism.

A Dicyanomethylene-4H-Pyran Based NIR Ratiometric Fluorescent Probe for Diazane and its Bioimaging

A near-infrared ICT-based fluorescent probe LX was successfully obtained. LX which detection limit is low as 22.2 nm shows excellent selectivity and high sensitivity to diazane. LX can selectively detected diazane from other species over a wide pH (3-10) range. A obvious color change of solution from yellow to orange can be found, allowing the naked eye to detect. The sensing mechanism was reasonably detected by ESI-MS and DFT calculations. In addition, LX succeed in the visualization of diazane in living cells and the detection of diazane in water samples.

A probe with double acetoxyl moieties for hydrazine and its application in living cells

As a common chemical reductant, hydrazine has been widely used in various fields. However, its high toxicity to human and environment have also attracted people's attention. In this work, a new fluorescence "turn-on" probe based on coumarin for hydrazine was successfully synthesized. The probe with double acetoxyl moieties as the reaction sites can obtain the detection limit as low as 2.98 nM for the detection of hydrazine in distilled water, which was lower than the U.S. Environmental Protection Agency standard (10 ppb). In addition, it also responded obvious fluorescence enhancement and high selectivity to hydrazine over other molecules. Furthermore, this probe could visualize the hydrazine in living cells.

A chromogenic and fluorogenic rhodol-based chemosensor for hydrazine detection and its application in live cell bioimaging

A rhodol-based fluorescent probe has been developed as a selective hydrazine chemosensor using levulinate as a recognition site. The rhodol levulinate probe (RL) demonstrated high selectivity and sensitivity toward hydrazine among other molecules. The chromogenic response of RL solution to hydrazine from colorless to pink could be readily observed by the naked eye, while strong fluorescence emission could be monitored upon excitation at 525 nm. The detection process occurred via a ring-opening process of the spirolactone initiated by hydrazinolysis, triggering the fluorescence emission with a 53-fold enhancement. The probe rapidly reacted with hydrazine in aqueous medium with the detection limit of 26 nM (0.83 ppb), lower than the threshold limit value (TLV) of 10 ppb suggested by the U.S. Environmental Protection Agency. Furthermore, RL-impregnated paper strips could detect hydrazine vapor. For biological applicability of RL, its membrane-permeable property led to bioimaging of hydrazine in live HepG2 cells by confocal fluorescence microscopy.

A novel fluorescein-based "turn-on" probe for the detection of hydrazine and its application in living cells

We constructed a novel probe for hydrazine detection based on ICT and PET mechanism. Phthalimide and acetyl ester groups were used as the recognition units. Addition of hydrazine produced a turn-on fluorescence at 525nm along with the fluorescent color change from dark to yellow. The probe could selectively detect hydrazine over other related interfering species. The detection limit of the probe for hydrazine was calculated to be 0.057μM which was lower than the EPA standard (0.320μM). Furthermore, the probe could also be applied for the imaging of hydrazine in living cells.

Carbon dots derived from carboxymethylcellulose for sensing isoniazid and H2O2

Herein, blue-fluorescence carbon dots (CDs) derived from carboxymethylcellulose have been innovatively synthesized with well-distributed sizes.

Europium ion post-functionalized zirconium metal–organic frameworks as luminescent probes for effectively sensing hydrazine hydrate

We describe a highly sensitive chemical sensor for the detection of the hydrazine hydrate. The chemical sensor was synthesized by simply doping a UiO-66 type metal–organic framework (MOF) with Eu³⁺ through a well-known post-synthetic modification method. The Eu³⁺@MOF was characterized by powder X-ray diffraction (PXRD), nitrogen gas adsorption isotherm measurements, FTIR, and ICP-MS. This luminescent probe exhibits strong emission intensity, and more significantly, displays various merits, such as high selectivity with notable photoluminescence quenching effect, rapid response time, and remarkable sensitivity with low detection of limit for hydrazine recognition. Under the optimal experimental conditions, hydrazine hydrate can be detected by this method in concentrations as low as 0.18 μM, which is much lower than the threshold limit value (10 ppb, ≈0.3 μM) of hydrazine exposure recommended by the U.S. Environmental Protection Agency (EPA). More interestingly, a portable film sensing device derived from this MOF display quick response to hydrazine hydrate within 90 s. A possible luminescent quenching mechanism for hydrazine hydrate was also investigated.

A luminescent metal–organic framework have been realized for efficiently sensing hydrazine hydrate.

A rhodol-based fluorescent chemosensor for hydrazine and its application in live cell bioimaging

A rhodol cinnamate fluorescent chemosensor (RC) has been developed for selective detection of hydrazine (N₂H₄). In aqueous medium, the rhodol-based probe exhibited high selectivity for hydrazine among other molecules. The addition of hydrazine triggered a fluorescence emission with 48-fold enhancement based on hydrazinolysis and a subsequent ring-opening process. The chemical probe also displayed a selective colorimetric response toward N₂H₄ from colorless solution to pink, readily observed by the naked eye. The detection limit of RC for hydrazine was calculated to be 300nM (9.6ppb). RC is membrane permeable and was successfully demonstrated to detect hydrazine in live HepG2 cells by confocal fluorescence microscopy.

A highly selective long-wavelength fluorescent probe for hydrazine and its application in living cell imaging

A highly selective long-wavelength turn-on fluorescent probe has been developed for the detection of N₂H₄. The probe was prepared by conjugation the tricyanofuran-based D-π-A system with a recognizing moiety of acetyl group. In the presence of N₂H₄, the probe can be effectively hydrazinolysized and produce a turn-on fluorescent emission at 610nm as well as a large red-shift in the absorption spectrum corresponding to a color change from yellow to blue. The sensing mechanism was confirmed by HPLC, MS, UV-vis, emission spectroscopic and theoretical calculation studies. The probe displayed high selectivity and sensitivity for N₂H₄ with a LOD (limit of detection) of 0.16μM. Moreover, the probe was successfully utilized for the detection of hydrazine in living cells.

An Enzyme-Induced Novel Biosensor for the Sensitive Electrochemical Determination of Isoniazid

In this present work, a glassy carbon electrode (GCE) was modified primarily with multiwalled carbon nanotubes (MWCNTs) and a composite of MWCNTs and titanium oxide nanoparticles (TiO₂NPs). The enzyme horseradish peroxidase (HRP) was immobilized to enhance the sensing ability of GCE. The proposed biosensor was used for the sensitive determination of isoniazid (INZ) in various pharmaceutical samples. The electrochemical behaviour of the developed MWCNT-TiO₂NPs-HRP-GCE biosensor was studied by using cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry (TGA) and transmission electron microscopy (TEM) techniques were used to characterize the developed sensor. Phosphate buffer solution (PBS) with pH 7 was used as supporting electrolyte in the present investigation. The cyclic voltammetric results revealed that the increment of anodic peak currents for the enzyme-induced sensor was almost 8-fold greater than that of a bare GCE. The DPV technique exhibited good limit of detection and limit of quantification values, viz., 0.0335 μM and 0.1118 μM, respectively. Moreover, the developed sensor showed long-lasting stability and repeatability without any interferents. This strongly indicates that the fabricated sensor shows outstanding electrochemical performance towards INZ, with excellent selectivity and sensitivity. The developed sensor was successfully applied to pharmaceutical samples and gave good percentages of recoveries.

Electrochemical hydrogen peroxide sensor based on carbon supported Cu@Pt core-shell nanoparticles

The Cu@Pt/C nanocomposites have been synthesized via two-step reduction method. Electrochemical observations showed that the Cu@Pt/C had better electrocatalytic activity for the reduction of hydrogen peroxide than Pt/C, with a wide linear range between 0.50μM and 32.56mM, a high sensitivity of 351.3μAmM^-1cm^-2, and a low detection limit of 0.15μM (signal/noise=3). Furthermore, the sensor based on Cu@Pt/C has potential applications due to its excellent long-time stability, good reproducibility and acceptable selectivity.

Observation of Single Pt Nanoparticle Collisions: Enhanced Electrocatalytic Activity on a Pd Ultramicroelectrode

Single Pt nanoparticle (NP) collisions on an electrode surface were detected by using an electrocatalytic amplification method with a Pd ultramicroelectrode (UME). Pd is not a preferred material for UMEs for the detection of single Pt NP collisions, because Pd shows similar electrocatalytic activity compared with Pt for hydrazine oxidation, thus resulting in a high background current level. However, a Pt NP colliding on the Pd UME shows greatly enhanced activity compared with a Pt NP on an inert UME, such as a Au UME, which is usually used for the detection of single Pt NP collisions. The use of an electroactive UME material instead of an inert one facilitated the study of single-NP activity on the various solid supports, which is important in many NP applications.

Consequences of New Approach to Chemical Stability Tests to Active Pharmaceutical Ingredients

There is a great need of broaden look on stability tests of active pharmaceutical ingredients (APIs) in comparison with current requirements contained in pharmacopeia. By usage of many modern analytical methods the conception of monitoring the changes of APIs during initial stage of their exposure to harmful factors has been developed. New knowledge must be acquired in terms of identification of each degradation products, especially volatile ones. Further research as toxicology prediction during in silico studies of determined and identified degradation products is necessary. In silico methods are known as computational toxicology or computer-assisted technologies which are used for predicting toxicology of pharmaceutical substances such as impurities or degradation products. This is a specialized software and databases intended to calculate probability of genotoxicity or mutagenicity of these substances through a chemical structure-based screening process and algorithm specific to a given software program. Applying of new analytical approach is proposed as the usage of PAT tools, XRD, HS-SPME GC-MS/MS, LC-MS/MS for stability testing. Described improvements should be taken into account in case of each drug existing already in the market as well as being implemented as new one.

Hydrophobicity effects in iron polypyridyl complex electrocatalysis within Nafion thin-film electrodes

Four polypyridyl redox catalysts Fe(bp)₃²⁺, Fe(ph)₃²⁺, Fe(dm)₃²⁺, and Fe(tm)₃²⁺ (with bp, ph, dm, and tm representing 2,2′-bipyridine, 1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine, and 3,4,7,8-tetramethyl-1,10-phenanthroline, respectively) are investigated for the electrocatalytic oxidation of three analytes (nitrite, arsenite, and isoniazid).

A highly sensitive fluorescent probe for detection of hydrazine in gas and solution phases based on the Gabriel mechanism and its bioimaging

A new probe 2-benzo[1,2,5]thiadiazol-4-yl-isoindole-1,3-dione (BTI) based on the Gabriel reaction was developed for hydrazine which shows promising selectivity towards hydrazine over other analytes.

Electrochemical flow injection analysis of hydrazine in an excess of an active pharmaceutical ingredient: achieving pharmaceutical detection limits electrochemically

The quantification of genotoxic impurities (GIs) such as hydrazine (HZ) is of critical importance in the pharmaceutical industry in order to uphold drug safety. HZ is a particularly intractable GI and its detection represents a significant technical challenge. Here, we present, for the first time, the use of electrochemical analysis to achieve the required detection limits by the pharmaceutical industry for the detection of HZ in the presence of a large excess of a common active pharmaceutical ingredient (API), acetaminophen (ACM) which itself is redox active, typical of many APIs. A flow injection analysis approach with electrochemical detection (FIA-EC) is utilized, in conjunction with a coplanar boron doped diamond (BDD) microband electrode, insulated in an insulating diamond platform for durability and integrated into a two piece flow cell. In order to separate the electrochemical signature for HZ such that it is not obscured by that of the ACM (present in excess), the BDD electrode is functionalized with Pt nanoparticles (NPs) to significantly shift the half wave potential for HZ oxidation to less positive potentials. Microstereolithography was used to fabricate flow cells with defined hydrodynamics which minimize dispersion of the analyte and optimize detection sensitivity. Importantly, the Pt NPs were shown to be stable under flow, and a limit of detection of 64.5 nM or 0.274 ppm for HZ with respect to the ACM, present in excess, was achieved. This represents the first electrochemical approach which surpasses the required detection limits set by the pharmaceutical industry for HZ detection in the presence of an API and paves the wave for online analysis and application to other GI and API systems.

The simultaneous determination of omethoate and dichlorvos pesticides in grain samples using a palladium and graphene composite modified glassy carbon electrode

An electrochemical sensor based on a palladium (Pd) and graphene (Gr) composite modified GCE was fabricated, characterised and used for the simultaneous determination of OMT and DCV in grain samples.

A BODIPY/pyrene-based chemodosimetric fluorescent chemosensor for selective sensing of hydrazine in the gas and aqueous solution state and its imaging in living cells

A BODIPY-based pyrenebutyrate-linked (BPB) chromogenic and fluorogenic probe was synthesized and characterized for the specific detection of hydrazine.

Stable manganese carbonyl radicals as a rapid colorimetric thiol and hydrazine sensor

A stable manganese carbonyl radical serves as a rapid and sensitive colorimetric sensor for thiols and hydrazines.