Diffusion Of Ammonia Research Articles

Ammonia diffusion combustion and emission formation characteristics in a single cylinder two stroke engine

Liquid ammonia diffusion combustion (LADC) is an effective approach to achieving high ammonia energy ratio (AER) and combustion efficiency in engines. However, there is a lack of simulation studies of LADC mode in ammonia/diesel dual direct injection engines. To address this gap, the study develops a numerical model based on an independently modified marine two-stroke engine. This model analyzes the combustion performance of ammonia in LADC mode and the pollutant generation mechanisms in LADC mode across various AER conditions. The findings indicate that in the LADC mode, the liquid phase ammonia spray exhibits a concentrated distribution area, facilitating thorough combustion of ammonia fuel. The diesel mixture and flame are entrained into the liquid phase ammonia spray, facilitating multi point ignition. This process notably enhances combustion speed, thereby reducing overall combustion duration. In comparison to pure diesel combustion, soot emissions are reduced by 99 % under the LADC mode, and CA90 advanced by 11.8 °C A. In addition, when the AER range is from 50 % to 70 %, the engine exhibits favorable combustion and emission characteristics. By appropriately adjusting the liquid ammonia injection quantity, the indicated thermal efficiency improves by 10.7 %, the equivalent indication specific fuel consumption decreases by 13.9 %, and the emission such as NOx and soot can be also reduced effectively.

Preparation of NiCo-LDHs@rGO composites with improved electrochemical performance by ammonia diffusion method under closed conditions

Layered double hydroxides (LDHs) have been considered to be favorable pseudocapacitance electrodes due to their adjustable composition and low cost. The NiCo-LDHs@rGO (reduced graphene oxide) compositeswere prepared by the ammonia diffusion method. The conductivity of NiCo-LDHs was improved by composite rGO. When 30 mg of rGO was added, the specific capacitance reached 1920.5F/g at 1 A/g. When being assembled into an asymmetric two-electrode supercapacitor, an energy density of 50.5 Wh/kg was achieved at a power density of 900 W/kg. The NiCo-LDHs@rGO composite has significantly improved the electrochemical properties.

Experimental investigation on the turbulence flame autoignition characteristics of ammonia in a high-temperature co-flow

Ammonia has a promising future for transportation and industrial power as an innovative zero-carbon fuel because of the harsh emission laws in force and the pressing need of low carbon fuels. Thus, the aim of this work has been to investigate the autoignition characteristics of an ammonia turbulence flame under a high temperature co-flow, on the basis of an experimental platform. The morphology, lift height, and stability of an ammonia jet diffusion flame have been explored under different co-flow regimes (in terms of temperature and velocity) and fuel injection pressures. It was found that when the co-flow temperature augments, the ammonia jet can form a stable lifting flame. Moreover, the combustion stability of the ammonia flame increases significantly and the fluctuation of the lift height of the flame clearly decreases over time. Forming a stable ammonia jet lifting flame under high co-flow velocities and injection pressures requires a high co-flow temperature. The length, area, and perimeter of an ammonia jet diffusion combustion flame increase as the co-flow temperature increases. The distance from the point of autoignition to the central nozzle outlet and the ignition delay both decrease when the co-flow temperature augments. The lift height of an ammonia diffusion combustion flame gradually decreases as the co-flow temperature increases. Moreover, there is a critical temperature of 1173 K beyond which the decline slope of both the lift height and ignition delay decreases.

EXPLORING FACTORS AFFECTING NITROGEN ISOLATION BY CATION EXCHANGE MEMBRANE AND THEIR IMPLICATIONS FOR MICROBIAL FUEL CELL PERFORMANCE IN WASTEWATER TREATMENT

This study explores the utilization of a cation exchange membrane (CEM) in a microbial fuel cell (MFC) system to isolate nitrogen from wastewater influents. While employing a CEM in an MFC system has drawbacks, such as increased internal resistance and reduced power output, it also provides a means for optimal energy recovery from organics while allowing isolated nitrogen to be treated in subsequent steps. This study evaluated the diffusion of ammonium through CEM in a dual-chamber MFC under different operating conditions. Results indicated that the MFC reactor with CEM as a separator isolated 88-93% of the nitrogen input, demonstrating the feasibility of this approach for nitrogen separation in wastewater treatment applications. Factors affecting nitrogen isolation, including COD input at the anode, dissolved oxygen (DO) at the cathode, and external resistance (ER), are identified. Higher COD input at the anode and the DO at the cathode were found to enhance nitrogen separation, while increased ER had an adverse effect on nitrogen isolation capacity. Additionally, changes in the surface characteristics of the CEM during operation could impact nitrogen isolation, emphasizing the need for careful monitoring and maintenance of the CEM to ensure consistent performance over time. In conclusion, this study highlighted the potential of using a CEM in MFC systems for nitrogen isolation, provided insights into the factors affecting the efficacy of nitrogen separation, and underscored the need for monitoring and maintenance of the CEM. These results could significantly impact the development of more efficient and sustainable wastewater treatment using the MFC system.

Enhancement of Ni-NiO-CeO2 Interaction on Ni-CeO2/Al2O3-MgO Catalyst by Ammonia Vapor Diffusion Impregnation for CO2 Reforming of CH4.

Ni-based catalysts have been widely used for the CO2 reforming of methane (CRM) process, but deactivation is their main problem. This study created an alternative electronic Ni-NiO-CeO2 interaction on the surface of 5 wt% Ni-5 wt% CeO2/Al2O3-MgO (5Ni5Ce(xh)/MA) catalysts to enhance catalytic potential simultaneously with coke resistance for the CRM process. The Ni-NiO-CeO2 network was developed on Al2O3-MgO through layered double hydroxide synthesis via our ammonia vapor diffusion impregnation method. The physical properties of the fresh catalysts were analyzed employing FESEM, N2 physisorption, and XRD. The chemical properties on the catalyst surface were analyzed employing H2-TPR, XPS, H2-TPD, CO2-TPD, and O2-TPD. The CRM performances of reduced catalysts were evaluated at 600 °C under ambient pressure. Carbon deposits on spent catalysts were determined quantitatively and qualitatively by TPO, FESEM, and XRD. Compared to 5 wt% Ni-5 wt% CeO2/Al2O3-MgO prepared by the traditional impregnation method, the electronic interaction of the Ni-NiO-CeO2 network with the Al2O3-MgO support was constructed along the time of ammonia diffusion treatment. The electronic interaction in the Ni-NiO-CeO2 nanostructure of the treated catalyst develops surface hydroxyl sites with an efficient pathway of OH* and O* transfer that improves catalytic activities and coke oxidation.

Low concentration adsorption of ammonia using metal halide loaded biogas residue-based carbon materials

Treating wastewater with elevated ammonia nitrogen levels in garbage treatment plants is a global concern, with blow-off recognized as an efficient process for nitrogen removal. However, this method generates low-concentration ammonia, presenting a challenge for adequate recovery. This study addresses this issue by impregnating metal halides onto K2CO3-activated biogas residue to create composite materials tailored for adsorbing low-concentration ammonia. We systematically investigated the impact of activation parameters, metal halide type, loading capacity, and environmental conditions on the adsorption properties of the materials. Notably, at an activation temperature of 700 °C, utilizing copper chloride with a loading capacity of 30 %, the material exhibited a saturation adsorption capacity of 29.32 mg/g for 200 ppm NH3, with a breakthrough time of 45.6 min, significantly surpassing the untreated sample and demonstrated excellent regeneration performance. SEM, BET, and FTIR analyses revealed that the material provided dispersion sites for metal halides, promoted the complexation of metal halides and ammonia and retained pores for ammonia diffusion, thereby enhancing adsorption efficiency. This innovative approach contributes to waste utilization and ensures efficient ammonia recovery through metal halide-ammonia complexation.

Engineering 2D nano-sheet struvite by ethanol regulation for boosting flame retardant properties

Struvite exhibits versatile applications as both a slow-release fertilizer and an inorganic flame-retardant material. In this study, we present a successful synthesis method for producing nano-sheet struvite with a remarkably thin nanoscale thickness of 63 nm and an impressive specific surface area of 128.4 m2·g−1. Our approach involves a combination of ethanol supplementation and ammonia diffusion. By employing MgCl2·6H2O and NaH2PO4·2H2O as reactants, with a Mg2+:PO43- molar ratio of 1:2, and incorporating 50 vol% ethanol, we achieved optimal preparation conditions. Moreover, we determined that a reaction time of 20 min and a reaction pH ranging from 9.3 to 9.5 yielded the best results. The experimental results revealed that the nano-sheet variant of struvite exhibited exceptional physical barrier properties achieving a flame retardance rate of 92.6 %, surpassing other morphologies such as rod-like, butterfly-like, and needle-like variants. And the optimal usage amount of nano-sheet struvite on the wood surface was determined to be 8.5 × 10−3 g·cm−2. Furthermore, the mechanism of the ethanol solvent in the formation process of 2D nano-sheet struvite was preliminarily discussed, offering a viable approach for the preparation of struvite with high flame retardant performance.

Visualization study on the ignition and diffusion combustion process of liquid phase ammonia spray ignited by diesel jet in a constant volume vessel

Ammonia fueled engines applying diffusion combustion mode is expected to further improve the thermal and combustion efficiencies with high burning rate and high ammonia energy replacement. However, there is a lack of the fundamental studies about ammonia diffusion combustion characteristics. Therefore, the fundamental optical experiments of liquid phase ammonia spray and combustion, which is ignited by pilot diesel injection, were performed to investigate the ignition and diffusion combustion characteristics of liquid phase ammonia. According to the high-speed photography, interaction processes between the liquid phase ammonia spray and the diesel spray had been described, and the whole ignition and combustion processes were also recorded in detail. The discussion about the effect of diesel jet ignition location on ammonia ignition process shows that the effective ammonia ignition zone by diesel spray is the region of gas entrainment zone except for the liquid phase ammonia volume under evaporated condition, where the interval on ammonia spray axis is about 16 mm ∼ 35 mm away from the ammonia nozzle exit under the current experimental conditions, and the ammonia spray is failed to be ignited at any region out of the effective ignition zone. Moreover, the ammonia diffusion combustion characteristics under various ammonia injection durations reveals that the entrainment, including both the diesel flame and the surrounding ambient gas, into the effective ignition zone of liquid phase ammonia spray, is the effective way to achieve reliable ignition and the subsequent diffusion combustion of ammonia, which can increase the energy ratio (ammonia to pilot diesel) up to at least 2.9. Finally, based on the control of combustion mode of the pilot diesel, utilizing premixed diesel flame to induce the diffusion combustion of ammonia is proved to be an effective regulation scheme to enhance the performance of ammonia combustion under engine-like thermal conditions.

Preparation and electrochemical properties of NiCo-layered double hydroxide supercapacitor

Layered double hydroxides (LDHs) are favorable pseudocapacitance electrodes due to their adjustable composition and low cost. Here, a series of NiCo-LDHs were prepared by a novel ammonia diffusion method at room temperature. Compared with other synthesis methods, this method is a simple, green, original and effective method. The morphology, structure, and elemental composition of NiCo-LDH electrode materials were characterized and their electrochemical properties were tested. The optimal honeycomb NiCo-LDH shows a specific capacitance (Cs) of 1463.2F·g−1 at 1 A·g−1, and the rate capacity is 75.2 % at 20 A·g−1. Particularly, the Cs is still 87.9 % after 2000 charge–discharge cycles at a high current density of 20 A·g−1. In addition, the hybrid supercapacitor with NiCo-LDH//activated carbon (AC) could show an energy density of 23.4 Wh·kg−1 at a power density of 900 W·kg−1, along with 73.4 % capacity retention after 5000 cycles.

Extended Ensemble Molecular Dynamics Study of Ammonia-Cellulose I Complex Crystal Models: Free-Energy Landscape and Atomistic Pictures of Ammonia Diffusion in the Crystalline Phase.

Here, we report extended ensemble molecular dynamics simulations of ammonia-cellulose I complex crystal models to evaluate the diffusion behavior of the guest ammonia molecules and the potential of mean force (PMF), namely, the free energy change along the chosen reaction coordinate, for migration of an ammonia molecule in the crystal models. Accelerated molecular dynamics simulations confirmed that ammonia molecules almost exclusively diffused through the hydrophilic channel even when the crystal framework was retained. Adaptive steered molecular dynamics simulations detected distinct PMF peaks with heights of approximately 7 kcal/mol as the ammonia molecule passed through the cellulose-chain layers. Introducing hybrid quantum mechanical and molecular mechanics theory to the adaptive steered molecular dynamics simulation effectively lowered the heights of the PMF peaks to approximately 5 kcal/mol, accompanied by a slight decrease in the baseline. Removal of the ammonia molecules in the neighboring channels resulted in a continuous increase in the baseline for the migration of an ammonia molecule in the hydrophilic channel. When the halves of the crystal model were separated to widen the hydrophilic channel to 0.2 nm, the PMF profiles exhibited an unexpected increase. This resulted from water structuring in the expanded hydrophilic channel, which disappeared with further expansion of the hydrophilic channel to 0.3 nm.

Performance investigation of an electrochemical ammonia compressor stack

Electrochemical (EC) energy conversion has a critical role to play in the future of clean energy. As the world transitions away from fossil fuel energy sources, EC compression emerges as a promising technique for energy storage, specifically energy stored in the form of pressurized ammonia. The present study examines the performance of an ammonia EC compressor stack under steady-state operating conditions to demonstrate the technology's utility in such applications. Using hydrogen as a carrier gas, we examined the effect of pressure and current on the operation of an EC ammonia compressor stack. We found the total voltage increased significantly with increasing current but increased marginally with increasing pressure. We measured the flow rate leaving the cell and analyzed the composition of the effluent gas stream with gas chromatography. While the device provided useful compression work in all observed cases, back diffusion of ammonia hampered the performance, reducing the flow rate of the effluent fluid by as much as 67%. The maximum observed single-cell efficiency was 40% with respect to ideal isentropic compression. The ohmic losses associated with high current and the back diffusion effect are likely responsible for the low cell efficiency.

Multiscale modeling of ammonia adsorption on zinc sulfate-doped activated carbon: Sensitivity analysis, parameter identification, and model validation

In this study four models are developed and validated to describe the dynamic adsorption of ammonia on zinc sulfate-doped activated carbon, ranging from simple single-scale to complex multiscale models. They are based on equations for mass balance, thermodynamics, hydrodynamics, and adsorption kinetics. Since the values of the parameters are needed for the implementation of the models, the doped activated carbon is characterized and ammonia isotherms measurements are performed at three different temperatures, i.e., 288, 303, and 313 K. A method based on parameter sensitivity analysis is used to evaluate the estimability of the unknown parameters of the Toth isotherm equation. Experimental breakthrough curves were then measured at various ammonia concentrations and gas flow rates. These curves were used to determine the overall mass transfer and axial dispersion coefficients, as well as the effective and intracrystalline diffusion, involved in the model equations. The models were implemented and solved using Comsol Multiphysics®. The study showed that the adsorption process was limited by the diffusion of ammonia and adsorption on the zinc sulfate crystal. The models were validated using breakthrough curves different from those used for parameter identification. The agreement between model predictions and measurements was evaluated using performance indices and confirmed by a Kolmogorov-Smirnov statistical test.

Simultaneous ammonium and water recovery from landfill leachate using an integrated two-stage membrane distillation

Resources recovery from landfill leachate (LFL) has been attracting growing attention instead of merely purifying the wastewater. An integrated two-stage membrane distillation (ITMD) was proposed to simultaneously purify LFL and recover ammonia in this study. The results showed that organics could be always effectively rejected by the ITMD regardless of varying feed pH, with COD removal higher than 99%. With feed pH increased from 8.64 to 12, the ammonia migration (50–100%) and capture (36–75%) in LFL were considerably enhanced, boosting the separated ammonia enrichment to 1.3–1.7 times due to the improved ammonium diffusion. However, the corresponding membrane flux of the first MD stage decreased from 13.7 to 10.5 L/m2·h. Elevating feed pH caused the deprotonation of NOM and its binding with inorganic ions, constituting a complex fouling layer on the membrane surface in the first MD stage. In contrast, the membrane permeability and fouling of the second MD were not affected by feed pH adjustment because only volatiles passed through the first MD. More importantly, it was estimated that ITMD could obtain high-quality water and recover high-purity ammonium from LFL with relatively low ammonium concentration at an input cost of $ 2–3/m3, which was very competitive with existing techniques. These results demonstrated that the ITMD can be a valuable candidate strategy for simultaneous water purification and nutrient recovery from landfill leachate.

First principle study on transition metal ammine borohydrides with amphoteric hydrogen for hydrogen storage applications

Usually the ions of a particular element in solids either in positive or in negative oxidation states, which are influenced by their chemical circumstances. Thus, it is quiet interesting for an atom having both positive and negative oxidation states within the same structural framework in a particular compound. Our structural and chemical bonding analyses show that the hydrogen ions in the transition metal ammine borohydrides (TMABHs) with the chemical formula M(BH4)2(NH3)2 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) have both + and − oxidation states. Moreover, our detailed analyses show that the hydrogen present in these compounds have amphoteric behaviour with hydrogen closer to boron is in negative oxidation state and that closer to nitrogen is in the positive oxidation state. The spin-polarised van der Waals interaction included calculation show that all these materials except M = Zn are having finite magnetic moment at the transitions metal site with the anti−ferromagnetic ordering as ground state. The localised magnetic moment similar to those present in molecular magnet with large band gap value indicating that these transparent magnets may find application in novel devices. Our nudged elastic band calculation show that the migration barrier for ammonia diffusion in these materials are more than 1 eV and hence these compounds may be used for energy storage applications since they have high weight percentage of hydrogen. The confirmation of the presence of amphoteric behaviour of hydrogen in TMABHs has implication in designing volume efficient hydrides for hydrogen storage applications.

Paper sensor-based method using a portable 3D-printed platform and smartphone-assisted colorimetric detection for ammonia and sulfide monitoring in anaerobic digesters and wastewater

A simple and low-cost field-deployable method using paper sensors in combination with a 3D-printed portable platform to simultaneous determination of ammonia and sulfide has been developed. Ammonia and sulfide are harmful pollutants for the environment and important toxicants inhibiting anaerobic digestion, therefore, are key monitoring parameters during wastewater treatment. The sample preparation system consisted of a well microplate and sensor paper discs placed inside the microplate sealing system. Gas pervaporation and diffusion of ammonia and hydrogen sulfide across a Teflon membrane onto a paper discs, impregnated with bromothymol blue and methylene blue assay reagents, allowed the ammonia and sulfide determination, respectively. The detection system consisted in a 3D-printed photographic lightbox with LED plates and a smartphone. A code was developed in ImageJ for a fast colorimetric measurement of the digital images. Under optimal conditions, limits of detection of 1.3 and 1.7 mg L-1 and linear concentration ranges between 5 and 50 mg L-1 and 5–45 mg L-1, were obtained for ammonia and sulfide, respectively. The analysis of an anaerobic digester and wastewater samples revealed good precisions (RSDs < 10 %) and recoveries (91–105 %). This methodology shows advantages such as a high precision, a simple paper discs preparation and a reusable system.

A review on spherical crystallization: A novel technique in the field of particle engineering

In the production of tablets, the direct compression method is mostly used. In comparison to the traditional wet granulation approach, this cannot be used with sensitive pharmaceuticals and also has a lot more processing limitations. Spherical agglomeration is a novel method for creating pharmaceutical dosage forms that are immediately compressible, the process of spherical agglomeration, which improves the powder's qualities such as particle size, shape, flow characteristics, solubility, and bioavailability of pharmaceutical medicinal ingredients, includes transforming tiny crystals into a spherical shape. The spherical crystallization was improved for use with hydrophilic polymers in order to improve the dissolution properties of pharmaceuticals that are poorly water-soluble. The flow characteristics, particle size analysis, compression, and dissolution behaviour of the spherical agglomerates were also improved. Wet spherical agglomeration (WSA) and the quasiemulsion solvent diffusion method (QESD) are the two most used methods for crystallizing spheres. Additionally, these approaches have two additions: the ammonia diffusion system (ADS) and crystallo-coagglomeration (CCA).The neutralization technique is another method used in this procedure. Any of the aforementioned methods can be employed simultaneously for both crystallization and agglomeration. The crystal physical characteristics, including their shape, polymorphism detection using x-ray powder diffraction (XRD), and thermodynamic characteristics using differential scanning calorimetry (DSC), were examined.

SPHERICAL CRYSTALLIZATION: A TOOL TO IMPROVE SOLUBILITY OF DRUGS

Spherical crystallization is a technique in which crystallization and agglomeration are carried out synchronously in one step to form compact spherical form. The most common methods used in spherical agglomeration are quasi emulsion solvent diffusion method, ammonia diffusion system, neutralization technique and co-agglomeration. It succeeded to improve dissolution property of poorly soluble drugs. This can change drug powder properties such as flowability, wettability, packability, compressibility. It has wider applications in improvement of poorly compressible drugs; it has wider application in improvement of compressability of poorly compressible drugs, masking bitter taste of drugs, improving dissolution property, bioavailability and solubility of drugs. Agglomeration crystals converted into tablet forms thus helping us by saving time and reducing cost.

Ammonia crossover in thermally regenerative ammonia-based batteries for low-grade waste heat recovery

Ammonia crossover usually occurs in thermally regenerative ammonia-based batteries (TRABs) and significantly deteriorates the performance. In this study, the effect of ammonia crossover on the performance of TRABs and its influencing factors are studied. In addition, an ammonia-breathing thermally regenerative ammonia-based battery with an ammonia gas chamber (ATRB) is constructed by regulating the structure of the gas diffusion layer to control ammonia transfer in the anode. The results show that the cathode performance remarkably decreases with the increase of ammonia content in the cathode, and the amount of ammonia crossover increase with the rise of initial ammonia concentration, discharging current, and temperature. The visualization results show that TRAB with the ammonia diffusion layer can effectively alleviate the ammonia crossover by regulating ammonia transfer. The content of polytetrafluoroethylene (PTFE) in the gas diffusion layer significantly influences ammonia transfer to the porous anode and the cathode. The battery performance increases firstly and decreases later with the PTFE content, and an optimal PTFE content is 20%.

Synthesis of vacant graphitic carbon nitride in argon atmosphere and its utilization for photocatalytic hydrogen generation

Graphitic carbon nitride (C3N4) was synthesised from melamine at 550 °C for 4 h in the argon atmosphere and then was reheated for 1–3 h at 500 °C in argon. Two band gaps of 2.04 eV and 2.47 eV were observed in all the synthetized materials. Based on the results of elemental and photoluminescence analyses, the lower band gap was found to be caused by the formation of vacancies. Specific surface areas of the synthetized materials were 15–18 m2g−1 indicating that no thermal exfoliation occurred. The photocatalytic activity of these materials was tested for hydrogen generation. The best photocatalyst showed 3 times higher performance (1547 μmol/g) than bulk C3N4 synthetized in the air (547 μmol/g). This higher activity was explained by the presence of carbon (VC) and nitrogen (VN) vacancies grouped in their big complexes 2VC + 2VN (observed by positron annihilation spectroscopy). The effect of an inert gas on the synthesis of C3N4 was demonstrated using Graham´s law of ammonia diffusion. This study showed that the synthesis of C3N4 from nitrogen-rich precursors in the argon atmosphere led to the formation of vacancy complexes beneficial for hydrogen generation, which was not referred so far.

An improved reverse flow injection analysis (rFIA) technique for determination of nanomolar concentrations of ammonium in natural waters with automatic background fluorescence detection: Ammonification during a Karenia brevis bloom in Tampa Bay

Ammonium is the most energetically favorable form of inorganic nitrogen that phytoplankton can take up, and its availability often limits phytoplankton biomass. Recently, the majority of methods for quantification of ammonium at nanomolar concentrations have used the reaction between ammonium and o-phthaldialdehyde (OPA). Two different approaches have been employed. One involves gas diffusion of ammonia across a membrane. The other entails a more direct approach and utilizes sulfite as a reducing agent to form a fluorescent product. A benefit of the separation technique is that natural fluorescence of the samples does not yield a false positive signal, however membrane failure and clogging are challenging analytical problems. The direct reaction between the analyte and OPA, although devoid of problems associated with membranes, requires a correction for background fluorescence. This work presents the development of a reverse flow injection analysis (rFIA) method with automatic background fluorescence correction and a low detection limit, along with its application to measure underway ammonium concentrations in Tampa Bay during a bloom of the toxic dinoflagellate Karenia brevis with concurrent fish kills in June of 2021. During field testing elevated concentrations of ammonium were found to coincide with the largest number of observed floating dead fish and lethal K. brevis concentrations. The method employs a sulfite-formaldehyde reagent mixed with the sample into which an OPA reagent is injected and heated to activate fluorescence. Fluorescence of the sample is measured before the injection of OPA and at the peak of OPA injection, allowing for differentiation of the background fluorescence from the signal proportional to analyte. The detection limit and the limit of quantitation for this technique are 2.3 nM and 7.5 nM, respectively, and the coefficient of variation is 0.6% for replicate deionized water blanks (N = 10). Advantages of this method compared to techniques capable of both nanomolar detection of ammonium and improved accuracy via background fluorescence correction include a greater sample throughput, an increase in reported useful reagent lifetime, and the ability to quantify ammonium in coastal waters.