Development of an accurate hand-held sensing platform for nitrite detection based on nitrogen-doped carbon dots.

As is well known, excessive nitrite can seriously pollute the environment and can harm human health. Although existing methods can be used to determine nitrite content, they still have some drawbacks, such as relatively complicated operation and expensive equipment. Herein, a hand-held sensing platform (HSP) for NO2- determination was developed. First, ammonia-rich nitrogen-doped carbon dots with orange-yellow emission were designed and synthesised, which were suitable as fluorescent probes because of their good optical properties and stability. Then, the HSP based on fluorescence using photoelectric conversion technology was designed and manufactured using three-dimensional printing technology. Under optimum conditions, the voltage (V/V0) of the proposed HSP showed good linearity for NO2- detection in the range of 10-500 µM, with a detection limit of 1.95 µM. This portable sensor showed good stability, accuracy and reliability in detecting actual water and meat samples, which may ensure food safety in practical applications. Moreover, the HSP is compact, portable and easily assembled and is suitable for on-site real-time detection, which shows great application potential and prospects.

Cerium vanadate/functionalized carbon nanofiber composite for the electrochemical detection of nitrite.

This study presents a facial and quick electrochemical sensor platform that offers remarkable water and food safety applications. The present work represents a study of the synthesis and characterization for efficient cerium vanadate (CeVO4) with a functionalized carbon nanofiber (f-CNF) decorated electrode, which is a highly effective electrode modifier for sensitive nitrite detection. The CeVO4 nanoparticles were synthesized using the facial hydrothermal technique, and a composite (CeVO4@f-CNF) was prepared using the sonication method. Afterward, the produced materials were confirmed with spectroscopic and microscopic analysis. The electrochemical behavior of nitrite was studied through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The DPV analysis depicts an excellent linear range of 0.1-1033 µM and a promising detection limit of 0.004 µM for the proposed electrode. The CeVO4@f-CNF electrode was applied to detect nitrite in water and meat samples. The proposed electrochemical sensor attributes the significant results towards the detection of nitrite.

Novel solution-gated transistor sensor-based SnO2 epitaxial thin films grown by pulsed laser deposition for nitrite detection.

A solution-gate controlled thin-film transistor with SnO2 epitaxial thin films (SnO2-SGTFT) is successfully utilized for highly sensitive detection of nitrite. The SnO2 films are deposited as channel materials on a c-plane sapphire (c-Al2O3) substrate through pulsed laser deposition (PLD), with superior crystal quality and out-of-plane atomic ordering. PtAu NPs/rGO nanocomposites are electrodeposited on a gold electrode to function as a transistor gate to further enhance the nitrite catalytic performance of the device. The change in effective gate voltage due to the electrooxidation of nitrite on the gate electrode is the primary sensing mechanism of the device. Based on the inherent amplification effect of transistors, the superior electrical properties of SnO2, and the high electrocatalytic activity of PtAu NPs/rGO, the SnO2-SGTFT sensor has a low detection limit of 0.1 nM and a wide linear detection range of 0.1 nM ~ 50 mM at VGS = 1.0 V. Furthermore, the sensor has excellent characteristics such as rapid response time, selectivity, and stability. The practicability of the device has been confirmed by the quantitative detection of nitrite in natural lake water. SnO2 epitaxial films grown by PLD provide a simple and efficient way to fabricate nitrite SnO2-SGTFT sensors in environmental monitoring and food safety, among others. It also provides a reference for the construction of other high-performance thin-film transistor sensors.

Non-enzymatic electrochemical sensor based on ionic liquid [BMIM][PF6] functionalized zirconium­copper bimetallic MOF composite for the detection of nitrite in food samples.

In this study, we developed an electrochemical sensor utilizing a composite material consisting of zirconium­copper bimetallic metal-organic framework functionalized with ionic liquid [BMIM][PF6]. This composite material was fabricated by simple wet impregnation method, which not only maintains excellent electrocatalytic activity but also enhances electron transfer rate and electroactive surface area. The ZrCu-MOF-818/ILs composite modified electrode has been demonstrated as an effective tool for the detection of nitrite. The electrode exhibited a remarkable limit of detection (LOD) of 0.148 µM and wide linear ranges of 6-3000 µM and 3000-5030 µM. It is worth noting that the sensor displayed excellent reproducibility and repeatability, with relative standard deviation (RSD) values of 1.06% and 1.37%, respectively. Furthermore, the proposed method was successfully applied for the detection of nitrite in tap water and pickle juice.

Anchoring CeF3 nanoparticles on porous carbon nanofibers as self-supporting electrodes for highly sensitive detection of nitrite.

Designing a working electrode is crucial for the reliable electrochemistry detection, which is applied to detect toxic and harmful substances sensitively and rapidly. Here we report the polytetrafluoroethylene decomposition-assisted electrospinning, a combination method for creating nanopore and synthesizing CeF3, to prepare the self-supporting electrode of CeF3 nanoparticles-anchored on porous carbon nanofibers (CeF3/PCNFs) for highly sensitive nitrite detection. The CeF3/PCNFs exhibits remarkable electroactivity toward nitrite detection, featuring a wide concentration range (0.5 µM-6 mM), low detection limit (10 nm) and high sensitivity (2093 µA mM-1 cm-2). It also exhibits excellent selectivity, stability and reproducibility, and powerful reliability for nitrite detection in saliva, pickles, sausages, chips, river water and tap water. This study provides a facile strategy to prepare the metal fluoride-based self-supporting electrode, which overcomes the disadvantages of chemically modified electrodes unstable and poorly reproducible, and is significant for clinical diagnosis, food safety and environmental monitoring.

A novel premixing strategy for highly sensitive detection of nitrite on paper-based analytical devices.

BACKGROUND: Nitrite has been involved in many food processing techniques and its excessive consumption is closely related to the development of different diseases. Therefore, highly sensitive detection of nitrite is significant to ensure food safety. RESULT: This study presents a simple and novel strategy for the highly sensitive detection of nitrite in food using paper-based analytical devices (PADs). In this proposed strategy, the nitrite present in the sample undergoes efficient diazotization when initially mixed with sulfanilamide solution before reacting with N-(1-naphthyl) ethylenediamine dihydrochloride (NED) coated on the detection region of the PAD, leading to the maximum production of colored azo compounds. Specifically, within the concentration range of 0.1-20 mg/L, the LOD and LOQ for the nitrite assay using the premixing strategy are determined as 0.053 mg/L and 0.18 mg/L, respectively which significantly surpass the corresponding values of 0.18 mg/L (LOD) and 0.61 mg/L (LOQ) achieved with the regular Griess reagent analysis. SIGNIFICANCE: The study highlights the critical importance of the premixing strategy in nitrite detection. Under optimized conditions, the strategy demonstrates an excellent limit of detection (LOD) and limit of quantification (LOQ) for nitrite detection in eight different meat samples. In addition to its high precision, the strategy is applicable in the field of nitrite analysis. This strategy could facilitate rapid and cost-effective nitrite analysis in real food samples, ensuring food safety and quality analysis.

A Portable Integrated Electrochemical Sensing System for On-Site Nitrite Detection in Food.

Ensuring an appropriate nitrite level in food is essential to keep the body healthy. However, it still remains a huge challenge to offer a portable and low-cost on-site food nitrite analysis without any expensive equipment. Herein, a portable integrated electrochemical sensing system (IESS) is developed to achieve rapid on-site nitrite detection in food, which is composed of a low-cost disposable microfluidic electrochemical patch for few-shot nitrite detection, and a reusable smartphone-assisted electronic device based on self-designed circuit board for signal processing and wireless transmission. The electrochemical patch based on MXene-Ti3C2Tx/multiwalled carbon nanotubes-cyanocobalamin (MXene/MWCNTs-VB12)-modified working electrode achieves high sensitivity of 10.533 µA mm-1 and low nitrite detection limit of 4.22 µm owing to strong electron transfer ability of hybrid MXene/MWCNTs conductive matrix and high nitrite selectivity of VB12 bionic enzyme-based ion-selective layer. Moreover, the portable IESS can rapidly collect pending testing samples through a microfluidic electrochemical patch within 1.0 s to conduct immediate nitrite analysis, and then wirelessly transmit data from a signal-processing electronic device to a smartphone via Bluetooth module. Consequently, this proposed portable IESS demonstrates rapid on-site nitrite analysis and wireless data transmission within one palm-sized electronic device, which would pave a new avenue in food safety and personal bespoke therapy.

A dual-mode nanoprobe based on silicon nanoparticles and Fe(II)-phenanthroline for the colorimetric and fluorescence determination of nitrite.

A fluorometric and colorimetric dual-modal nanoprobe (denoted as Fe2+-Phen/SiNPs) has been developed for selective and sensitive determination of nitrite (NO2-). The mechanism is based on fluorescence quenching between silicon nanoparticles (SiNPs) and Fe(II)-phenanthroline complex (Fe2+-Phen) via inner filter effect and redox. With the addition of increasing NO2-, Fe2+ is oxidized to Fe3+, recovering the fluorescence of SiNPs. Meanwhile, the color of the system gradually changes from orange-red to colorless, which enables colorimetric measurement. The NO2- concentration shows a wide linear relationship with fluorescence intensity from 0.1 to 1.0 mM (R2 = 0.9955) with a detection limit of 2.4 µM in the fluorometric method (excitation wavelength: 380 nm). By contrast, the linear range of the colorimetric method ranges from 0.01 to 0.35 mM (R2 = 0.9953) with a limit of detection of 6.8 µM (proposed selective absorbance: 510 nm). The probe has been successfully applied to nitrite determination in water, salted vegetables, and hams demonstrating broad application prospects for the determination of nitrite in complicated matrices.

Fabrication of FRET based nano sensor from biomass-derived fluorescent carbon quantum dots and naphthalimide for ratiometric detection of nitric oxide: To examine nitrite levels in meat samples.

Nitric oxide (NO) is a ubiquitous, gaseous, free radical signaling molecule which plays a key role in physiological and pathological processes. Literature reports revealed that the conventional methods such as colorimetry, electron paramagnetic resonance (EPR), electrochemical etc. to detect NO are costly, time consuming and lack resolution, particularly in aqueous or biological system. Thus, in this context, herein we have developed covalently linked biomass derived carbon quantum dots (CQDs) and naphthalimide based nano sensor system for FRET based ratiometric detection of nitric oxide (NO) in pure aqueous media. The CQDs derived from orange peels were characterized using UV-visible absorption, fluorescence spectroscopy, PXRD, TEM, FT-IR and zeta potential studies. Further, the obtained CQDs were functionalized with amine functionality, and subsequently linked with naphthalimide derivative (5) using terephthaldehyde through covalent bond formation. The conjugation of naphthalimide (5) and functionalized CQDs was studied using DLS, zeta potential, FT-IR and time resolved fluorescence spectroscopy. The excitation of developed nano sensor system at λex 360 nm results in fluorescence emission at λem 530 nm which establishes the FRET pair between the CQDs and naphthalimide unit. However, in the presence of NO, the observed FRET pair abolishes due to the cleavage of NO susceptible imine bond. The developed sensor demonstrates high selectivity towards NO with limit of detection (LOD) and limit of quantification (LOQ) of 15 nM and 50 nM respectively. Further, the developed sensor system was also utilized for indirect detection of nitrite (NO2-) in food samples for food safety and monitoring.

Bismuth-Decorated Honeycomb-like Carbon Nanofibers: An Active Electrocatalyst for the Construction of a Sensitive Nitrite Sensor.

The existence of carcinogenic nitrites in food and the natural environment has attracted much attention. Therefore, it is still urgent and necessary to develop nitrite sensors with higher sensitivity and selectivity and expand their applications in daily life to protect human health and environmental safety. Herein, one-dimensional honeycomb-like carbon nanofibers (HCNFs) were synthesized with electrospun technology, and their specific structure enabled controlled growth and highly dispersed bismuth nanoparticles (Bi NPs) on their surface, which endowed the obtained Bi/HCNFs with excellent electrocatalytic activity towards nitrite oxidation. By modifying Bi/HCNFs on the screen-printed electrode, the constructed Bi/HCNFs electrode (Bi/HCNFs-SPE) can be used for nitrite detection in one drop of solution, and exhibits higher sensitivity (1269.9 µA mM-1 cm-2) in a wide range of 0.1~800 µM with a lower detection limit (19 nM). Impressively, the Bi/HCNFs-SPE has been successfully used for nitrite detection in food and environment samples, and the satisfactory properties and recovery indicate its feasibility for further practical applications.

Emerging Two-Dimensional Materials-Based Electrochemical Sensors for Human Health and Environment Applications.

Two-dimensional materials (2DMs) have been vastly studied for various electrochemical sensors. Among these, the sensors that are directly related to human life and health are extremely important. Owing to their exclusive properties, 2DMs are vastly studied for electrochemical sensing. Here we have provided a selective overview of 2DMs-based electrochemical sensors that directly affect human life and health. We have explored graphene and its derivatives, transition metal dichalcogenide and MXenes-based electrochemical sensors for applications such as glucose detection in human blood, detection of nitrates and nitrites, and sensing of pesticides. We believe that the areas discussed here are extremely important and we have summarized the prominent reports on these significant areas together. We believe that our work will be able to provide guidelines for the evolution of electrochemical sensors in the future.

The Eschenmoser's Salt as a Formylation Agent for the Synthesis of Indolizinecarbaldehydes and Their Use for Colorimetric Nitrite Detection.

C-H bond formylation is the most immediate way to incorporate the versatile formyl group into (hetero)aromatics. However, the type of reagents and severe conditions involved in the classical formylation methods often curtail their application, especially in the presence of other functional groups. Herein, we present the Eschenmoser's salt, a commercially available (dimethylamino)methylating chemical, as a useful reagent for the C-H formylation of indolizines and other compounds. The method is straightforward and mild, furnishing indolizinecarbaldehydes in modest-to-good yields with exclusive and remote regioselectivity. Furthermore, these compounds can be easily transformed into push-pull dyes and are highly selective in the colorimetric detection of nitrite, a substance extensively employed as preservative in the food industry, the concentration of which is crucial to control to prevent harmful effects in living organisms. The assay is simple, allowing the naked-eye detection of nitrite in solution or on a cotton swab for a wide range of concentrations.

Bionic Enzyme-Assisted Ion-Selective Amperometric Biosensor Based on 3D Porous Conductive Matrix for Point-of-Care Nitrite Testing.

Nitrite plays a critical role in a variety of physiological processes and maintaining the nitrite level in an appropriate range is vital to keep healthy. Current nitrite analysis methods lack sensitivity and require tedious operations, which could not meet the need of point-of-care (POC) nitrite detection in precision medicine. Here we present a cyanocobalamin (VB12) bionic enzyme-assisted ion-selective amperometric biosensor based on 3D porous conductive matrix (PCM), which can facilitate rapid and accurate POC nitrite monitoring in complex biofluids. The experimental findings quantitatively demonstrate that the biosensor has a sensitivity of 64.08 µA/(mM·cm2), a wide linear range of 0.025-45 mM, and low limit of detection of 1 nM. Moreover, the developed VB12/BSA-PCM biosensor shows outstanding stability after 21 days with 2% decline in current signal, and high repeatability between batches with RSD of only 1.29%. Real salivary nitrite detection has been evaluated, and the results match well with the commercial nitrite analyzer. Thus, the bionic enzyme-assisted ion-selective amperometric biosensor proposed herein has potential utility as an affordable tool for POC detection and home-based healthcare.

Electrochemical Sensor Based on Iron(II) Phthalocyanine and Gold Nanoparticles for Nitrite Detection in Meat Products.

Nitrites are widely used in the food industry, particularly for the preservation of meat products. Controlling the nitrate content in food is an important task to ensure people's health is not at risk; therefore, the search for, and research of, new materials that will modify the electrodes in the electrochemical sensors that detect and control the nitrate content in food products is an urgent task. In this paper, we describe the electrochemical behavior of a glass carbon electrode (GCE), modified with a Fe(II) tetra-tert-butyl phthalocyanine film (FePc(tBu)4/GCE), and decorated with gold nanoparticles (Au/FePc(tBu)4/GCE); this electrode was deposited using gas-phase methods. The composition and morphology of such electrodes were examined using spectroscopy and electron microscopy methods, whereas the main electrochemical characteristics were determined using cyclic voltammetry (CV) and amperometry (CA) methods in the linear ranges of CV 0.25-2.5 mM, CA 2-120 µM in 0.1 M phosphate buffer (pH = 6.8). The results showed that the modification of bare GCEs, with a Au/FePc(tBu)4 heterostructure, provided a high surface-to-volume ratio, thus ensuring its high sensitivity to nitrite ions of 0.46 µAµM-1. The sensor based on the Au/FePc(tBu)4/GCE has a low limit of nitrite detection at 0.35 µM, good repeatability, and stability. The interference study showed that the proposed Au/FePc(tBu)4/GCE exhibited a selective response in the presence of interfering anions, and the analytical capability of the sensor was demonstrated by determining nitrite ions in real samples of meat products.

Rapid detection of nitrite based on nitrite-oxidizing bacteria biosensor and its application in surface water monitoring.

Timely and sensitive detection of nitrite is of great significance for human health protection and water pollution treatment. However, many biosensors can only determine the comprehensive toxicity of the water, and there are few electroactive biofilm (EAB) sensors for the specific detection of pollutants. Biofilms formed by bacteria with specific functions can improve the specificity of nitrite identification by biosensors. This study developed a novel, rapidly responding, high sensitivity (958.6 µAµM-1cm-2), wide detection range and anti-interference electrochemical biosensor based on electroactive nitrite-oxidizing bacteria. The biosensor could accurately detect nitrite in the range of 0.3-100 mg/L within 3 min by the cyclic voltammetry (CV) method. The bioelectrode could perform stable detection of nitrite over 200 cycles. The specificity of the biosensor for detecting nitrite was demonstrated by the presence of nitrite oxidizing bacteria (NOB) and nitrite oxidase enzyme (NXR) on the electrode biofilm. The biosensor performed well in wetlands and rivers, with an RSD <14.8% in the detection of nitrite at low concentrations, and further revealed the nitrification occurrence. Our study provided a feasible way for the development of a highly sensitive, rapidly responding and stable electrochemical biosensor, which also exhibited potential applications for long-term detection of nitrite and assessment of ecological function in surface water (rivers, lakes, wetlands, marshes, etc.).

Electrochemical Sensing of Nitrite Ions Using Modified Electrode by Poly 1,8-Diaminonaphthalene/Functionalized Multi-Walled Carbon Nanotubes.

A novel electrochemical sensor based on conducting polymer and multi-walled carbon nanotubes was reported for the detection of nitrite ions (NO2 -). The hybrid material poly 1,8-Diaminonaphthalene (poly 1,8-DAN)/functionalized multi-walled carbon nanotubes (f-MWCNT) was prepared by using a simple electrochemical approach which is based on the deposition of functionalized multi-walled carbon nanotubes (f-MWCNT) on the surface of the electrode followed by the electropolymerization of 1,8-DAN using cyclic voltammetry. The morphology and the electro-catalytic properties of the obtained electrodes were investigated with Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS) showing an improvement of the electronic transfer due to the synergic effect between the proprieties of poly 1,8-DAN and f-MWCNT. Under the optimum experimental conditions, the poly 1,8-DAN/f-MWCNT/CPE exhibited excellent electro-catalytic activity towards nitrite detection. The nitrite anodic peak potential decreased by 210 mV compared to the bare carbon paste electrode. The calibration plot of nitrite detection was linear in the range of concentration from 300 to 6500 nM with a low detection limit of 75 nM.

Ionogel-based hybrid polymer-paper handheld platform for nitrite and nitrate determination in water samples.

Nowadays, miniaturization and portability are crucial characteristics that need to be considered for the development of water monitoring systems. In particular, the use of handheld technology, including microfluidics, is exponentially expanding due to its versatility, reduction of reagents and minimization of waste, fast analysis times and portability. Here, a hybrid handheld miniaturized polymer platform with a paper-based microfluidic device was developed for the simultaneous detection of nitrite and nitrate in real samples from both, fresh and seawaters. The platform contains an ionogel-based colorimetric sensor for nitrite detection and a paper-based microfluidic device for the in situ conversion of nitrate to nitrite. The platform was fully characterized in terms of its viability as a portable, cheap and quick pollutant detector at the point of need. The calibration was carried out by multivariate analysis of the color of the sensing areas obtained from a taken picture of the device. The limits of detection and quantification, for nitrite were 0.47 and 0.68 mg L-1, while for nitrate were 2.3 and 3.4 mg L-1, found to be within the limits allowed by the environmental authorities, for these two pollutants. Finally, the platform was validated with real water samples, demonstrating its potential to monitor nitrite and nitrate concentrations on-site as a first surveillance step before performing extensive analysis.

A novel electrochemical sensor based on nitrite-oxidizing bacteria for highly specific and sensitive detection of nitrites.

Real-time nitrite control in water is necessary for environmental safety and human health, and has triggered the research and development of novel detection methods. Previous studies have made great progress on enzyme-free and enzyme electrochemical sensors. However, enzyme-free sensors have low selectivity and a complex preparation process, and enzyme sensors have short lifetimes, and these issues need to be addressed. In this work, we proposed for the first time a highly specific and sensitive biofilm sensor based on nitrite-oxidizing bacteria (NOB) for the bio-electrochemical detection of nitrite in water. The mechanism of nitrite detection was attributed to the competition of oxygen between aerobic respiration of the NOB and the cathode oxygen reduction on the carbon felt electrode, resulting in a decrease in current. This decrease in current (ΔI) had a linear relationship with the nitrite concentration in the range of 0.1 to 1 mg L-1 and 1 to 10 mg L-1, which was corresponding to the sensitivities of 48.62 and 2.24 µA mM-1 cm-2, respectively. And the limit of detection (LOD) was calculated to be 0.033 mg L-1 (2.39 µM) with a signal-to-noise ratio of 3. Moreover, several common interfering ions had no effect on the nitrite detection owing to the functional microbial species (NOB) and weakly electrochemical behavior of electrode at the low potential of -0.1 V, showing high specificity for nitrite detection of biofilm sensor. Therefore, the actual nitrified wastewater was well detected by the biofilm sensor. In addition, allylthiourea (ATU) took good effect on the resistance of the influence of ammonia oxidizing bacteria (AOB) in the biofilm sensor, maintaining the high selectivity of biofilm sensor in case the biofilm sensor was fouled with AOB. The biofilm sensor in our work showed good selectivity, sensitivity and stability in long-term detection.

A Novel Highly Sensitive Electrochemical Nitrite Sensor Based on a AuNPs/CS/Ti3C2 Nanocomposite.

Nitrite is common inorganic poison, which widely exists in various water bodies and seriously endangers human health. Therefore, it is very necessary to develop a fast and online method for the detection of nitrite. In this paper, we prepared an electrochemical sensor for highly sensitive and selective detection of nitrite, based on AuNPs/CS/MXene nanocomposite. The characterization of the nanocomposite was demonstrated by scanning electron microscopy (SEM), a transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, the fabricated electrode showed good performance with the linear range of 0.5-335.5 µM and 335.5-3355 µM, the limit of detection is 69 nM, and the sensitivity is 517.8 and 403.2 µA mM-1 cm-2. The fabricated sensors also show good anti-interference ability, repeatability, and stability, and have the potential for application in real samples.

Sensitive analytical detection of nitrite using an electrochemical sensor with STAB-functionalized Nb2C@MWCNTs for signal amplification.

An electrochemical sensor based on stearyl trimethyl ammonium bromide - functionalized niobium carbide@multi-walled carbon nanotubes (Nb2C@MWCNTs-STAB) for signal amplification was successfully constructed for sensitive detection of nitrite (NO2-). Niobium carbide@multi-walled carbon nanotubes (Nb2C@MWCNTs) with high electrical conductivity and water dispersibility were first prepared in a one-pot hydrothermal synthesis, after which cationic STAB was added to overcome the negative surface charge on the Nb2C@MWCNTs. The electrostatic attraction between Nb2C@MWCNTs-STAB and NO2- was improved by the STAB, which enhanced the sensitivity of the constructed sensor for NO2-. Under optimized conditions, Nb2C@MWCNTs-STAB/GCE exhibited excellent analytical performance for detection NO2- with two wide liner ranges (0.1-100 µmol L-1 and 100-2000 µmol L-1) and a limit of detection of 0.022 µmol L-1. Nitrite recovery tests in milk and spinach samples showed recoveries in the range of 89.82-104.52%. The NO2- residues in ham and pickled vegetable (cedrela sinensis) samples were analysed using the presented sensor and a spectrophotometric method, with no significant difference found between the results of the two methods.