Ammonium Ion-selective Electrode Research Articles

Flexible ammonium ion-selective electrode based on inkjet-printed graphene solid contact

Miniaturization and mass-production of potentiometric sensor systems is paving the way towards distributed environmental sensing, on-body measurements and industrial process monitoring. Inkjet printing is gaining popularity as a highly adaptable and scalable production technique. Presented here is a scalable and low-cost route for flexible solid-contact ammonium ion-selective electrode fabrication by inkjet printing. Utilization of inkjet-printed melamine-intercalated graphene nanosheets as the solid-contact material significantly improved charge transport, while evading the detrimental water-layer formation. External polarization was investigated as a means of improving the inter-electrode reproducibility: the standard deviations of E0 values were reduced after electrode polarization, the linear region of the response was extended to the range 10−1–10−6 M of NH4Cl and LODs reduced to 0.88 ± 0.17 μM. Finally, we have shown that the electrodes are adequate for measurements in a complex real sample: ammonium concentration was determined in landfill leachate water, with less than 4 % deviation from the reference method.

Touch–based potentiometric sensors for simultaneous detection of urea and ammonium from fingertip sweat

Urea is a biomarker for diagnosis and management of multiple disorders. The measurement of urea could help in the diagnosis of patients with kidney dysfunction. Despite their attractive analytical performances, the existing urea measurement methods are still limited to sophisticated and time–consuming or require invasive blood sampling. Herein, a reliable noninvasive, simple, and disposable touch–based potentiometric sensor is fabricated for rapid monitoring of fingertip sweat urea. Novel touch–based urea detection relies on immobilized urease recognition and a solid–contact ammonium–ion–selective electrode, along with a screen–printed carbon working electrode modified carboxylated carbon nanotubes for enhancing sensor’s sensitivity. The fingertip sweat under sedentary rest conditions can be instantaneously collected on customized porous polyvinyl alcohol hydrogel transporting sweat to working electrode surface where the hydrolysis of urea is catalyzed, generating bicarbonate and ammonium. The resulting ammonium can be detected with ion–selective transducer, enabling indirect monitoring of sweat urea. Potential interference from co–existing ammonium in human sweat is addressed by developing a dual disposable potentiometric sensor, consisting of urea and ammonium sensors on a single strip platform allowing for simultaneous touch–based detection of sweat urea and ammonium. The resulting dual disposable sensing system offers rapid urea and ammonium monitoring within a group of healthy human subjects, along with a good correlation with R2 = 0.974 between the sweat urea and capillary blood urea levels. Additional confirmation among a broad sample of individuals along with the validation of sensor data through centralized laboratory tests will establish the practicality of simultaneously monitoring urea and ammonium levels.

Highly stable ammonium ion-selective electrodes based on one-pot synthesized gold nanoparticle-reduced graphene oxide as ion-to-electron transducers

An effective transducer for all-solid-state ion-selective electrodes (SC-ISEs) was developed based on gold nanoparticle-reduced graphene oxide (AuNP-rGO) hybrid material. The AuNP-rGO composite was synthesized via a simple, eco-friendly, and one-pot method with sodium citrate as the reducing agent and the stabilizer. The nanocomposite was deposited on the GC substrate via the drop-casting method and then covered with an ammonium ion-selective membrane (NH4+-ISM) to form the potentiometric electrode. The AuNP-rGO layer possessed a large surface area, high capacitance, and good hydrophobicity; thereby effectively enhancing the potential stability of the electrode without the formation of an aqueous layer. The electrode also exhibited a rapid potential response (<10 s) to NH4+ ions, an excellent Nernstian response with a slope of 56.94 (±1.57) mV/decade, a detection range of 10-5 − 10-2 M, and a detection limit of 3.80 × 10-6 M. The proposed electrode also exhibited outstanding properties including insensitivity to interferences (light, oxygen, carbon dioxide, and redox species), good reproducibility, and long operating life. The electrode has been successfully applied for NH4+ detection in real water samples, which makes it a promising alternative for developing effective and robust SC-ISEs.

A Solid-Contact for Ammonium Ion-Selective Electrodes Based on Gold Nanoparticle-Reduced Graphene Oxide Hybrid Material: One-Pot Synthesis Using Sodium Citrate as Green Reductant and Stabilizer

A Solid-Contact for Ammonium Ion-Selective Electrodes Based on Gold Nanoparticle-Reduced Graphene Oxide Hybrid Material: One-Pot Synthesis Using Sodium Citrate as Green Reductant and Stabilizer

Simultaneous Analysis of Ammonium and Nitrate Ions Levels with Potentiometric Multi-commutation Flow System Method

This study aims to develop a multi-commutation flow system method for simultaneous determination of ammonium ion and nitrate ion using two detectors, namely ammonium ion selective electrode and nitrate ion selective electrode. The multi-commutation flow system method uses two three way selenoide valves to adjust the sample flow and ISA solution. The selenoid valve alternately flows the sample and ISA solution to the ion selective electrode. Flow control by three way selenoid valves is controlled by LabView which is programmed in the computer. The computer is connected with Arduino and a relay that functions as an on-off switch on the three way valve selenoid. This method is then applied to measure the levels of ammonium ions and nitrate ions in well water samples. The performance of the multi-commutation flow system determined includes linearity, limit detection, sensitivity, repeatability, and recovery test. Ammonium analysis results show good performance with several criteria. Ammonium linearity value is 0,9991, ammonium detection limit value is 2,23 × 10-5 M, sensitivity of ion selective electrode ammonium is 45,39 mV per decade, the repeability value is less than 2% and the recovery percentage of ammonium is 115%. While the results of the nitrate analysis showed a linearity value of 0,9937, a nitrate detection limit value of 1,31 × 10-5 M, sensitivity of the ion selective electrode nitrate of -110,58 mV per decade, a repeatability value of less than 2% and a recovery percentage of 87% nitrate. Keywords: Flow Analysis, multi-commutation, ammonium, nitrat, simultaneous.

Reconstruction of corrupted datasets from ammonium-ISE sensors at WRRFs through merging with daily composite samples

Long-term, continuous datasets of high quality are important for instrumentation, control, and automation efforts of wastewater resources recovery facility (WRRFs). This study presents a methodology to increase the reliability of measurements from ammonium ion-selective electrodes (ISEs). This is done by correcting corrupted ISE data with a data source that often is available at WRRFs (volume-proportional composite samples). A yearlong measurement campaign showed that the existing standard protocols for sensor maintenance might still create corrupted dataset, with poor sensor recalibrations responsible for abrupt and unrealistic jumps in the measurements. The proposed automatic correction methodology removes both recalibration jumps and signal drift by using information from composite samples that already are taken for reporting to legal authorities. Results showed that the developed methodology provided a continuous, high-quality time series without the major data quality issues of the original signal. In fact, the signal was improved for 87% of days when a reference sample was available. The effect of correcting the data before use in a data-driven software sensor was also investigated. The corrected dataset led to noticeably smaller day-to-day variations in estimated NH4+ loads, and to large improvements on both median estimates and prediction bounds. The long time series allowed for an investigation of how much training data that is required to fit a software sensor, which provides estimates that are representative for the entire study period. The results showed that 8 weeks of data allowed for a good median estimate, while 16 weeks are required for obtaining good 80% prediction bounds. Overall, the proposed method can increase the applicability of relatively cheaper ISE sensors for ICA application within WRRFs.

Application of an ammonium ion-selective electrode for the real-time measurement of ammonia nitrogen based on pH and temperature compensation

Traditional methods for determining the ammonia nitrogen (NH3-N) concentration are the colorimetric method using Nessler’s reagent or salicylate. To prevent secondary pollution, minimise the time required for measurement, and reduce cation interference, new NH3-N measurement methods have been developed including fluorescence, gas phase molecular absorption spectrometry, and ammonia gas sensing electrode methods. However, in these techniques, the addition of a chemical reagent is unavoidable, so the real-time and accurate measurements of NH3-N are achieved hardly. In this study, we used an ammonium ion-selective electrode (ISE) for the real-time measurement of NH3-N with compensation for the ammonium ion (NH4+) component of the total NH3-N concentration. The basic mechanism is that an ammonium ISE can measure NH4+ concentration, and NH4+ ratio in NH3-N can be calculated based on pH and temperature. Experimental results indicate that the ammonium ISE exhibited near-Nernstian behaviour, having a fitted line with a slope of 56.4 mV/pNH4. The compensation effects and reproducibility are good. Furthermore, the difference in the temperature responses at different NH4+ concentrations agrees with the Nernst equation basically. Therefore, the proposed method can provide a real-time and environmentally friendly solution to determine NH3-N concentration.

Smartphone-Based Ammonium Ion Biosensor for Sweat Analysis

In this article, we present a smartphone-based biosensor for detection of the ammonium ion in sweat. The sensing system consists of a sample collection chip, an ammonium ion selective electrode by screen printing, a potential reading chip and a smartphone. When the sweat flows through the sensitive membrane, a membrane potential is generated which can be captured by the potential reading chip linked with the smartphone. The potential signal was then converted to concentration value by a calibration curve. The detection can be achieved within one minute with good repeatability, and the level of the ammonium ion in sweat can reflect the body state during exercise.

A Potentiometric Biosensor for Cyanide Detection using Immobilized Whole Cell Cyanide Dihydratase of Flavobacterium indicum MTCC 6936

A potentiometric biosensor for cyanide detection has been developed using whole cell cyanide dihydratase activity of Flavobacterium indicum coupled to an ammonium ion selective electrode. The cyanide dihydratase activity was optimum when 2% agar and cells in the amount of 0.175 mg/mL dry cell weight (dcw) were used for immobilization. The free and immobilized whole cell cyanide dihydratase of F. indicum exhibited maximum activity (0.192 U/mg dcw and 0.175 U/mg dcw, respectively) in 0.1 M sodium phosphate buffer (pH 8.0) at 35°C with 5 mM potassium cyanide. KM and Vmax for free and immobilized whole cell cyanide dihydratase were 5.25 mM, 0.33 U/mg dcw and 6.25 mM, 0.25 U/mg, respectively. The agar immobilized whole cell cyanide dihydratase was used as a biocomponent coupled to a potentiometer. A linear relationship was observed between response time and cyanide concentration. The cyanide concentration of 0.06 ppm could be detected using this potentiometric biosensor with a response time of 2 min. The developed potentiometric biosensor could be used for the detection of cyanide in industrial wastewater and food samples.

Development of a flow injection analytical system for short chain amide determination based on a tubular bioreactor and an ammonium sensor.

Pseudomonas aeruginosa (P. aeruginosa) possesses intracellular amidase activity, which catalyses the hydrolysis of short aliphatic amides producing NH4+, and has already been used along with an ammonium ion selective electrode for amide quantification. However, the incorporation of a biological membrane turned to be a challenging process and either the final arrangement was prone to amidase losses or the recovery of the sensor coating after the interaction took too long. In this article a flow injection system with an ammonium acoustic wave sensor is proposed, and after testing several different arrangements for the biological element, the ultimate choice consisted of the immobilization of a P. aeruginosa cell-free extract in the inner wall of a tubular glass reactor, which resulted in a reliable analytical system. Response times less than one minute and complete recovery in less than two minutes assured conveniently fast analysis. The analytical system, as long as the column was properly stored in HEPES buffer containing 2 mM β-mercaptoethanol and 1 mM benzamidine and refrigerated when not in use, could be used at least for 20 working days, along a period of one month, maintaining the initial sensitivity.

A novel inhibition based biosensor using urease nanoconjugate entrapped biocomposite membrane for potentiometric glyphosate detection

A potentiometric biosensor based on agarose-guar gum (A-G) entrapped bio-nanoconjugate of urease with gold nanoparticles (AUNps), has been reported for the first time for glyphosate detection. The biosensor is based on inhibition of urease activity by glyphosate, which was measured by direct potentiometry using ammonium ion selective electrode covered with A-G-urease nanoconjugate membrane. TEM and FTIR analysis revealed nanoconjugate formation and its immobilization in A-G matrix respectively. The composite biopolymer employed for immobilization yields thin, transparent, flexible membrane having superior mechanical strength and stability. It retains the maximum activity (92%) of urease with negligible leaching. The conjugation of urease with AUNps allows improvement in response characteristics for potentiometric measurement. The biosensor shows a linear response in the glyphosate concentration range from 0.5ppm–50ppm, with limit of detection at 0.5ppm, which covers maximum residual limit set by WHO for drinking water. The inhibition of catalytic activity of urease nanoconjugate by gyphosate was confirmed by FTIR analysis. The response of fabricated biosensor is selective towards glyphosate as against various other pesticides. The biosensor exhibits good performance in terms of reproducibility and prolonged storage stability of 180days. Thus, the present biosensor provides an alternative method for simple, selective and cost effective detection of glyphosate based on urease inhibition.

Preparation, characterization and application of urease nanoparticles for construction of an improved potentiometric urea biosensor

The nanoparticles (NPs) aggregates of commercial urease from jack beans (Canavalia ensiformis) were prepared by desolvation and glutaraldehyde crosslinking and functionalized by cysteamine dihydrochloride. These enzyme nanoparticles (ENPs) were characterized by transmission electron microscopy (TEM), UV and Fourier transform infrared (FTIR) spectroscopy. The TEM images of urease NPs showed their size in the range, 18–100nm with an average of 51.2nm. The ENPs were more active and stable with a longer shelf life than native enzyme molecules. The ENPs were immobilized onto chitosan (CHIT) activated nitrocellulose (NC) membrane via glutaraldehyde coupling with 32.22% retention of initial activity of free ureaseNPs with a conjugation yield of 1.63mg/cm2. This NC membrane was mounted at the lower/sensitive end of the ammonium ion selective electrode (AISE) with O-ring and then electrode was connected to a digital pH meter to construct a potentiometric urea biosensor. The biosensor exhibited optimum response within 10s at pH 5.5and 40°C. The biosensor was employed for measurement of potentiometric determination of urea in sera of apparently healthy and persons suffering from kidney disorders. The biosensor displayed a low detection limit of 1µM/L with a wide working range of 2–80µM/L (0.002–0.08mM) and sensitivity of 23mV/decade. The analytical recovery of added urea in serum was 106.33%. The within and between-batch coefficient of variations (CVs) of present biosensor were 0.18% and 0.32% respectively. There was a good correlation (r = 0.99) between sera urea values obtained by reference method (Enzymic colorimetric kit method) and the present biosensor. The biosensor had negligible interference from Na+,K+,NH+4 and Ca2+ but Mg2+,Cu2+ and ascorbic acid but had slight interference, which was overcome by specific ion selective electrode. The ENPs bound NC membrane was used maximally 8–9 times per day over a period of 180 days, when stored in 0.01M sodium acetate buffer pH 5.5 at 4°C.

An All-Solid-State Ammonium Ion-Selective Electrode Based on Polyaniline as Transducer and Poly (o-phenylenediamine) as Sensitive Membrane

An All-Solid-State Ammonium Ion-Selective Electrode Based on Polyaniline as Transducer and Poly (o-phenylenediamine) as Sensitive Membrane

Monitoring Ammonium Ions in Oral Microbiome

Ion selective electrodes are used to measure real time ionic concentrations in biological systems including bacterial biofilms. The beneficial bacteria in the oral microbiome plays an important role by producing ammonium ions in the presence of L-arginine and urea. The production of ammonium ions creates an alkaline environment which neutralizes the acidity caused by the pathogenic bacteria. The neutralization of acidity is important to prevent dental caries. Measuring the ammonium ion concentration gives important details about the activity of the beneficial bacteria in different environments. We developed a solid contact ammonium ion selective electrode to study the release of ammonium ions from the beneficial bacteria. The sensor had a nernstian response and a dynamic range of 10 µM to 100 µM and good selectivity against common interferants like Na+, K+, H+. The sensor was used to test the release of ammonium ions in the vicinity of pathological bacteria to study the neutralization of acidic environment. This study will help in determination of ammonium ion concentration required to maintain homeostasis in the oral microbiome. The characterization of ammonium ion sensor and the measurement of ammonium ions in the oral microbiome will be presented at the conference. Figure 1

A novel all-solid-state ammonium electrode with polyaniline and copolymer of aniline/2,5-dimethoxyaniline as transducers

From the centre outwards, the novel all-solid-state ammonium ion-selective electrode was composed of a silver wire as substrate, covered with conductive polyaniline (PANI), copolymer of aniline/2,5-dimethoxyaniline (CPANI) and ion selective membrane (ISM) layers. PANI was formed in-situ on the Ag wire by the cyclic voltammetry method, scanned from 0 to 0.45V in 0.1M aniline hydrochloride solution, and then dipped the electrode in the N,N-Dimethyl formamide (DMF) solution of CPANI and ISM sequentially. The scanning electron microscope (SEM) observation revealed that the PANI formed cross-linked slabs about 0.3–2.5μm in length and 0.3–0.6μm in thickness. Under the SEM, CPANI micro particles filled in the cross-linked PANI slabs. Bulk impedance of the transducer was between 100 and 200Ω, much lower than the poly (vinyl chloride) (PVC) based transducer in the previous work. Fabrication procedures, micro-structure, and the common resolvability of the CPANI and ISM in the DMF were all essential for reducing the cross-boundary resistance. Linear response range of the electrode was 10−4–10−1M, with a Nernst slope of 54.20–56.59mV/decade. The potential drifts of each decade were ±0.5mV within 400s. The response time was less than 1s and the lifetime was three months. The ammonium electrodes were used to test the ammonium in the waste water with pH value from 2.6 to 10.1, and the testing results were in agreement with those obtained by titration method and Nessler’s reagent colorimetry method. The ammonium electrode proposed in this paper is suitable for in-situ monitoring NH4+ content in the environment in a wide range of pH value.

Analysis of Potential Applicability of the Potentiometric Urea Biosensor to Real Samples

Since the production and use of chemical products are performing a marked growth, the charge, for fast and efficient mechanisms of environmental pollution control and monitoring, has increased. This charge has been made even more present in the rural scenario, especially with regard to fertilizers and nitrogen compounds, which have a high pollution potential. Several methods are used to urea determination, but usually they require a pretreatment or they are unsuitable for monitoring in situ. For this reason, urea biosensor can be a fast and cost-effective analytical technique to be used in extensive monitoring programs. Urea enzyme sensors based on potentiometric detection of ammonium ion, ammonia gas and carbon dioxide have been reported. In this study, the potential applicability of the potentiometric urea biosensor to real samples has been studied. The biocomponent used was jack beans, Canavalia ensiformis, a vegetal tissue rich in urease. The vegetal tissue was immobilized on nylon net by glutaraldehyde in order to improve the enzyme stability and the lifetime of the urea biosensor. Moreover, an ammonium ion-selective electrode was been chosen as the transducer. The instrument was applied to commercial urea fertilizer solutions and an environmental sample, the sugar-cane vinasse. The linear concentration range calibration curve was 1–20 ppm urea with a response time of 15 min. Urea biosensor could be reused for 70 days and the response was more than 95 % reproducible. Moreover, the urea biosensor was tested in real samples with qualitative promising responses.

An All Solid-State Creatinine Biosensor Based on Ammonium-Selective PVC-NH2 Membrane Electrode

An all solid-state polymeric membrane potentiometric biosensor has been developed for creatinine. The biosensor was based on all solid-state ammonium-selective electrode. The ammoniumselective electrode was prepared by using aminated poly(vinylchloride) together with nonaction and di-cyclohexyl-18-crown-6 as ionic conductivity enhancer. The ammonium-selective electrode exhibited almost a 52 ± 5 mV slope between 1 × 10 −1 and 8 × 10 −6 M concentration levels of ammonium. Creatininase was immobilized on the surface of the polymeric all solid-state ammonium ion-selective electrode using a simple one step glutaraldehyde covalent attachment method. Potentiometric characteristics of the biosensor were examined in phosphate (pH 6.00, 7.20 and 8.20), Tris-HCl buffer (pH 6.00, 7.20 and 8.20) buffer and physiological model solutions at different creatinine concentrations (10 × 10 −1 –10 × 10 −6 M). The linear working range and sensitivity of the biosensor were also determined. The creatinine biosensor is highly sensitive and stable in both buffer solutions. Under obtimized conditions, the biosensor showed a linear response between 1 × 10 −1 –8 × 10 −5 M creatinine in both buffers at pH 7.20.

Immobilization of the urease on eggshell membrane and its application in biosensor

Eggshell membrane is a natural material, essentially made up of protein fibers having flexibility in the aqueous solution and possessing gas and water permeability. It is used as a biomembrane for immobilization of urease for the development of a potentiometric urea biosensor. Eggshell membrane was treated with polyethyleneimine (PEI) to impart polycation characteristics. Urease was immobilized on the PEI treated eggshell membrane through adsorption. SEM study was carried out to observe the changes in surface morphology after immobilization. FTIR study of membrane was carried out to observe the changes in IR spectra after immobilization of enzyme. Immobilized membrane was associated with ammonium ion selective electrode. Biosensor exhibited sigmoidal responses for the urea concentration range from 0.5 to 10mM. The response time of the biosensor was 120s. A single membrane was reused for 270 reactions without loss of activity. The urease–eggshell membranes were stable for 2months when stored in buffer even at room temperature.

A non-destructive ammonium detection method as indicator for freshness for packed fish: Application on cod

This paper introduces a non-destructive method for monitoring headspace ammonium as an indicator for changes in the freshness status of packed fish. Electrodes in an aqueous phase in the package monitor changes in the concentration of ammonia produced in/on the packed fish and released in the headspace. The outputs of an ammonium ion-selective electrode (NH4+-ISE) were compared with the volatile amines content of the fish fillets. The method was tested in triplicate with fresh cod fillets stored between −0.5 and 1.9°C. Changes in the ammonia content of the fish could be monitored in the aqueous phase with the NH4+-ISE. The changes in the NH4+-ISE signal correlated with the content of volatile amines (TVB-N) in the cod fillets. This non-destructive method might be the basis for the development of an intelligent packaging for monitoring freshness of packed fish.

An Electrochemical Biosensor for Acrylamide Determination: Merits and Limitations

The present work reports the results concerning the development and implementation of the first electrochemical biosensor for acrylamide determination, based on a direct biochemical interaction between the analyte and intact bacterial cells, with intracellular enzymatic activity. The biological recognition element consisted of whole cells of Pseudomonas aeruginosa containing intracellular amidase activity, which catalyses the hydrolysis of acrylamide producing ammonium ion (NH4 + ) and acrylic acid. The transduction process was accomplished by means of an ammonium ion selective electrode. Whole cells were firstly immobilized on single discs of polymeric membranes, such as polyethersulphone, nylon and polycarbonate, which were, then, attached to the surface of the selective electrode. However, it was observed a significant loss of cells each time the biosensor was used, namely at the beginning of the assay, when the membranes were attached to the ammonium electrode, and after the assay, when removed for storage purposes. This evidence determined a premature decrease in the biosensor’s stability. Instead of using single membrane discs, a “sandwich” design, with two membrane discs was considered. This way the cells remain contained between the membranes, never contacting the electrode’s surface, preventing their premature loss. Consequently, the activity of the biosensor could be maintained for longer periods of time. The analytical performance of the biosensor was evaluated. The best results were obtained when polyethersulphone double membranes were used. A typical response of 120 mV (after 6 min reaction time), a Nernstian slope of 48 mV/decade, a limit of detection of 6.31×10 -4 M and a half-life time of 27 days, are examples of some