Simultaneous flow-injection flourimetric determination of ammonia and hydrazine with a novel mode of forming pH gradients

A flow injection configuration is suggested for the simultaneous determination of ammonia and hydrazine at the μg ml^?1 level by formation of zones of different pH. The analytes react with o-phthalaldehyde and mercaptoethanol to form fluorescent derivatives at different pH values. In addition to the normal flow method, a stopped flow method is proposed to increase the ranges that can be quantified. The analysis of samples containing hydrazine and ammonia in ratios between 0.3 and 70.0 is described.     

Flow-injection determination of ammonia in kjeldahl digests by gas diffusion and conductometry

A flow injection/conductometric method is proposed for determing ammonia in solutions obtained from Kjeldahl digestion. The method is based on diffusion of ammonia through a PTFE membrane from an alkaline (NaOH/EDTA) medium to a deionized water stream. The change in conductance of the deionized water stream is proportional to the ammonia concentration present in the digest. The effects of flow parameters, temperature and potential interferences are reported. Approximately 100 samples can be injected per hour; the precision is about 1%. Results for total nitrogen in vegetable tissues, animal feeds and fertilizers are in good agreement with those obtained by the usual distillation/titration method.     

Reversed flow injection spectrophotometric determination of trace amount of ammonia in natural water by oxidation of ammonia to nitrite

A new sensitive flow injection method for determination of ammonia in natural water samples have been developed, based on the oxidation of ammonia to nitrite by hypochlorite in the presence of large amount of potassium bromide. The oxidant solution obtained by on-line mixing of hypochlorite and potassium bromide was injected into a water carrier stream, and then mixed with sample stream. Ammonia in the sample solution was oxidized to nitrite. Nitrite was then determined by spectrophotometry with sulfanilamide and N-1-naphthylethylenediamine. By reversed injection of the oxidant solution, the interference of nitrite and turbidity of the sample can be removed. The linear range of the method for ammonia is 0.2-12 muM. The proposed method is simple and sensitive. It had been applied to the determination of ammonia in lake water samples. Recoveries of 95-104% were obtained.     

Determination of ammonia in beers by pervaporation flow injection analysis and spectrophotometric detection

A pervaporation flow injection (PFI) method is described for the determination of ammonia in beers. After injecting the sample into a NaOH donor solution, ammonia and other volatiles are transferred in the pervaporation unit from the donor stream to an acceptor stream containing sodium salicylate and nitroprusside, which subsequently mixes with alkaline sodium dichloroisocyanurate to allow the classical Berthelot reaction to take place. The blue-coloured complex formed is monitored spectrophotometrically at 655 nm. A linear calibration curve with a range of 0.1–40 mg l⁻¹ was obtained. The method has a detection limit of 0.05 mg l⁻¹ and is capable of a sampling frequency of 11 h⁻¹ at 4 mg l⁻¹ ammonia. It was applied successfully to the determination of ammonia in synthetic samples and unfiltered lager beers. The advantages of the present method over the ammonia ion-selective electrode method and the PFI system based on mixed indicator detection are discussed.     

Environmentally friendly method for determination of ammonia nitrogen in fertilisers and wastewaters based on flow injection-spectrophotometric detection using natural reagent from orchid flower

Crude aqueous extract from the orchid ‘Dendrobium Sonia earsakul’ was utilised as a natural product reagent in flow injection analysis (FIA) incorporating a gas diffusion unit (GD) for the determination of ammonia nitrogen. Sample solution was injected into a NaOH donor stream to generate ammonia gas (NH₃). In the GD unit, NH₃ diffused across a PTFE gas-permeable membrane into the acceptor stream of the orchid extract. As the result, the aqueous orchid reagent became more alkaline and its colour changed from purple to green. The change in the colour of orchid acceptor correlated with the concentration of ammonia nitrogen in the sample and its absorbance monitored by a spectrophotometer at 600 nm. Ammonia nitrogen in chemical fertiliser samples and wastewater samples from agricultural fields were determined and reported as %N (w/w) and mg N L^?1, respectively. For chemical fertilisers which contained high content of ammonia nitrogen, a flow rate of 1.0 mL min^?1 and injection volume of 100 µL were used with a linear range of 5–40 mmol L^?1 and detection limit of 2.12 mmol L^?1. However, a higher sensitivity was required for wastewater samples having low ammonia nitrogen content. The flow rate was reduced to 0.3 mL min^?1 and the injection volume increased to 1000 µL. As a result, detection limit of 0.76 mmol L^?1 was achieved with linear range of 1–5 mmol L^?1. The results of our method agreed well with that using the OPA method employing fluorescence detection.     

Isothermal distillation in flow injection analysis: Determination of total nitrogen in plant material

An isothermal distillation unit is incorporated in flow injection systems. The influence of surfactant, flow rates, alkalinity, ionic strength, collector stream pH, reagent concentration and sample volume in ammonia distillation are discussed. A method for the determination of total nitgrogen in plant digests employing Nessler reagent is proposed. This method, based on merging zones approach, is characterized by a sampling rate of 100 samples per hour, a precision better than 3%, a reagent consumption of only 100 μl per sample and virtually no base-line drift. The results agree with those obtained with the indophenol blue colorimetric method. The incorporation of isothermal distillation in flow systems with potentiometric measurement is also described.     

Analysis of wastewater for anionic and cationic nutrients by ion chromatography in a single run with sequential flow injection analysis

To prevent nutrient enrichment and, hence the undesirable ecological impacts, the nutrients monitored in wastewater samples include two anionic species, i.e., nitrate and orthophosphate, and a cationic species, ammonium. Ion chromatography (IC) is one of the popularly used techniques for determinations of nitrate and phosphate in these samples, whereas determination of ammonium in wastewater samples is typically done using manual or automated wet chemistry, e.g., flow injection analysis (FIA). We have developed a sequential IC–FIA method, using Lachat’s QC8000 IC system, which allows determinations of nitrate, phosphate and ammonia in a single injection. In this system, a QuikChem Small Suppressor cartridge is regenerated in between the samples. A sample is injected while leaving the suppressor off-line. Ammonium, a cation, elutes in the void volume of an anion-exchange column. The unsuppressed column effluent, exiting the conductivity flow cell, up to this point is used for FIA determination of ammonia. When ammonia exits the conductivity flow cell, a fully regenerated suppressor is brought in-line for conductometric detection of the anions. Analog data are simultaneously acquired from colorimetric and conductometric detectors, for the cationic and anionic nutrients, respectively. The method is accurate with spike recoveries in wastewater samples ranging from 91% for nitrate to 114% for chloride. It is precise with RSD values, for replicate analyses (n=7) of a mid-range standard, ranging from 0.4% for phosphate to 1% for nitrate.     

An aqueous ammonia sensor based on an inkjet-printed polyaniline nanoparticle-modified electrode

A sensor for the amperometric detection of aqueous ammonia was fabricated using the inkjet printing of dodecylbenzene sulfonate (DBSA)-doped polyaniline nanoparticles (nanoPANI) onto a screen-printed carbon paste electrode. The combination of the environmentally inert, aqueous nanoparticle dispersion with the inkjet printing technique allowed the rapid fabrication of sensors based on polyaniline that was not easily achievable in the past due to the lack of processability of bulk forms of the conducting polymer. The resulting modified electrode was characterised with respect to its operating pH and number of print layers and was found to perform optimally at near neutral pH with four nanoPANI inkjet-printed layers. The sensor was tested in a flow injection system for its response to aqueous ammonia using amperometric detection at -0.3 V vs. Ag/AgCl pseudo-reference and was found to have reproducibility to injections of ammonia of below 5% RSD and good sensitivity with an experimental detection limit of 20 microM and a theoretical detection limit of 3.17 microM (0.54 ppm). The sensor was also tested for its day-to-day stability and its response towards a range of interferents common to refrigerant waste waters. This system allows the rapid production of an ultra-low-cost, solid state, polyaniline-based aqueous ammonia sensor.     

全自动流动注射-分光光度法测定土壤中氨氮

传统的氯化钾溶液提取分光光度法测定土壤中氨氮时,需要加入硝普钠-苯酚显色剂混匀后一定时间再加入二氯异氰尿酸钠显色剂,这个过程中人为接触苯酚等有机试剂的时间较长,对人体和环境有一定的危害;且传统的比色法显色时间至少需要5h,显色时间较长,分析效率较低.应用全自动流动注射-分光光度法测定土壤中氨氮,考察了提取试剂的厂家、浓...     

Flie?injektionsanalyse in der Bodenuntersuchung und Pflanzenanalyse

Summary It could be shown that the flow injection technique can be well introduced in labs which need a high sample throughput without any loss of precision. For normal labs with agrochemical tasks it is possible to adapt the proposed flow injection methods for nitrogen and phosphorus. For the determination of ammonia in juices and musts flow injection is better in precision and faster than the conventional methods. The determination of nitrate in plant extracts can be performed without any clean-up of the crude extract by introducing a dialysis cell in the normal flow injection system. For the determination of proline and arginine methods were developed for flow injection. Both are selective with a high precision and crude plant extracts can be injected for determination. Flow diagrams and equipment parameters are described.     

Fluorescence Spectrophotometric Determination of Trace Ammonia

Measurement of trace ammonia (or ammonium ion) is important for environmental monitoring. Hiroshi Mikasa et al and Satoshi Sasaki et al had reported the determination of trace ammonia by flow injection analysis based on the reaction of ammonia and o-phthaiadehyde in the presence of 2-mercaptoethanol. The reaction equation is as follows.     

Action of gaseous ammonia and water on neodymium diphthalocyanine

The method of flow injection into the gas flow with detection of current resistance of the film was used to investigate the action of ammonia and water vapor on neodymium diphthalocyanine film. The value and sign of the electrophysical response are reversible at 18–22°C. When the film contacts with vapor, the current is changed within a few seconds, whereas the relaxation to the initial value when vapor is removed occurs within tens of seconds. The response parameters are suitable for developing effective sensors based on resistant films. No optical changes in the absorption spectra of the films were observed in the 400–800 nm region under the action of ammonia and water vapor. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1446–1447, July, 1998.     

Indirect Atomic Absorption Spectrometric Determination of Ammonia,Thiosulfate and Cyanide in an Unsegmented Flow System

Abstract

A flow injection analysis method (FIA), has been developed for the determination of cyanide, thiosulfate and ammonia by atomic absorption spectrometry (AAS). Aqueous solution of the analyte was injected into an on-line column containing glass beads and packed with silver chloride and deionized water was used as the carrier. The analyte dissolves the silver chloride and the dissolved silver complex is introduced to the nebulizer of the AAS. This method has proved to be sensitive, simple and precise. Detection limits of 1.0 × 10^?7 M, 5.0×10^?7 M and 5.0x10^?6M were obtained for thiosulfate, cyanide and ammonia, respectively. The precision of the technique was 2.0%, 2.4% and 1.4% in case of thiosulfate, cyanide and ammonia, respectively. The effects of flow rate and sample volume on the FIA/AAS signals are presented.     

A polypyrrole-based amperometric ammonia sensor

An ammonia sensor is described in this work. The sensing membrane is a thin layer of oxidized polypyrrole (PPy) on a platinum substrate. This sensor is used as the working electrode in a conventional three-electrode system for amperometric measurement of ammonia in aqueous solutions in the potential range of + 0.2 to + 0.4 V (vs. Ag/AgCl). Contact with ammonia causes a current to flow through the electrode. This current is proportional to the concentration of free ammonia in the solution and ammonium ions do not contribute to the measured signal. The signal is due to reduction of PPy by ammonia with subsequent oxidation of PPy by the external voltage source. The sensor is able to detect ammonia reproducibly at the muM level. The main interference is the doping effect of small anions such as Cl(-) and NO(3)(-), also giving a response on PPy at the mM level. This anionic response can, to a certain degree, be reduced by covering the polymer surface with dodecyl sulfate. The sensor gradually loses its activity when exposed to ammonia concentrations greater than 1 mM. The sensor has been tested by the flow injection analysis technique.     

Flow injection analysis : Part III. Comparison of continuous flow spectrophotometry and potentiometry for the rapid determination of the total nitrogen content in plant digests

The Berthelot reaction for the determination of ammonia by formation of indophenol blue, has been adapted to continuous flow spectrophotometry and the effects of acidity, temperature, ethanol content and sampling rate have been investigated; optimal conditions are described for the determination of nitrogen in Kjeldahl digests. Comparison of results obtained by this method, the air-gap electrode and classical distillation show no statistical difference at the 1% level, but the flow injection technique can be run at a much higher sampling rate (110–180 samples per h) than any other method and uses as little as 0.3 ml of digest per analysis.     

Determination of ammonia, ethanol and acetic acid in solution using membrane introduction mass spectrometry

Methods have been developed to allow applications of membrane introduction mass spectrometry (MIMS) to monitor solution phase components of fermentation broths using electron ionization. The solutions are transported by flow injection analysis (FIA) through a direct insertion membrane probe, fitted with a silicone membrane in the sheet configuration. Analytes of interest pass through the membrane and are ionized by electron implant ionization. The compounds monitored are ammonia, acetic acid, and ethanol, with ammonia being detected as the monochloramine derivative which is generated at pH 10 upon addition of hypochlorite. Quantitation is achieved using external standard solutions. The dynamic range for the quantification of ammonia is 2-8000 ppm, and for ethanol and acetic acid 10-1000 ppm. This method provides rapid detection of analytes of interest, on-line monitoring capabilities, and the advantage of electron ionization. The introduction of samples into the mass spectrometer is achieved readily and automatically, the response time is a few seconds, and there are no memory effects.     

Flow injection spectrophotometric or conductometric determination of ascorbic acid in a vitamin C tablet using permanganate or ammonia

Two simple flow injection (FI) procedures for the determination of ascorbic acid content in a vitamin C tablet are proposed: spectrophotometric involving injection into a stream of acidic potassium permanganate solution and monitoring its color change due to the redox reaction; FI conductometry based on the neutralization of ascorbic acid injected into a flowing ammonia solution yielding a change in conductivity. The procedures have been applied to the analysis of locally commercial vitamin C tablet samples. A through-put of at least 90 injections h⁻¹ can be achieved. The relative standard deviation was found to be 2.5% (for a 50 mg vitamin C tablet; n=7) for both. Results obtained by either procedure agree with a standard titrimetric method.     

Gas-diffusion separation and flow injection potentiometry

Summary The similarities and differences of the operation principle of gas-sensing electrodes and potentiometric detection coupled to gas-diffusion separation in flow injection analysis are discussed with special emphasis on selectivity and sensitivity aspects. Several examples of application are presented highlighting the improvements in detectability obtained by gas-diffusion flow injection potentiometry. High sensitivity determination of ammonium is achieved through accumulation of ammonia released from the sample stream in the small recipient volume of the gas-diffusion unit. A method for almost specific determination of cyanide is presented making use of gas-diffusion separation of hydrogen cyanide and potentiometric detection with a selective AgI membrane electrode. The interference of sulfide is totally prevented by its oxidation in the donor line. If applied to potentiometric measurement following gas diffusion separation an intrinsically non-selective metallic silver wire electrode turns out to enable the selective detection of sulfide with high sensitivity and fast response. A new approach for diffusive sampling and on-line detection of gas-phase contaminants is exemplified by the determination of NO_x.     

Simultaneous determination of amiodarone and its major metabolite desethylamiodarone in plasma, urine and tissues by high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatographic method for the simultaneous assay of amiodarone and desethylamiodarone in plasma, urine and tissues has been developed. The method for plasma samples and tissue samples after homogenizing with 50% ethanol, involves deproteinization with acetonitrile containing the internal standard followed by centrifugation and direct injection of the supernatant into the liquid chromatograph. The method for urine specimens includes extraction with a diisopropyl ether-acetonitrile (95:5, v/v) mixture at pH 7.0 using disposable Clin-Elut 1003 columns, followed by evaporation of the eluate, reconstitution of the residue in methanol-acetonitrile (1:2, v/v) mixture and injection into the chromatograph. Separation was obtained using a Radial-Pak C18 column operating in combination with a radial compression separation unit and a methanol-25% ammonia (99.3:0.7, v/v) mobile phase. A wavelength of 242 nm was used to monitor amiodarone, desethylamiodarone and the internal standard. The influence of the ammonia concentration in the mobile phase on the capacity factors of amiodarone, desethylamiodarone and two other potential metabolites, monoiodoamiodarone (L6355) and desiodoamiodarone (L3937) were investigated. Endogenous substances or a variety of drugs concomitantly used in amiodarone therapy did not interfere with the assay. The limit of sensitivity of the assay was 0.025 micrograms/ml with a precision of +/- 17%. The inter- and intra-day coefficient of variation for replicate analyses of spiked plasma samples was less than 6%. This method has been demonstrated to be suitable for pharmacokinetic and metabolism studies of amiodarone in man.     

示波流动注射分析

将流动注射技术应用于示波分析，建立了示波流动注射分析，即动态示波分析法。设计了适用于示波分析的流通池，提出电压反馈的示波新技术，研究了新方法的重现性、检测限及影响去极剂峰高的各种因素。实验表明：新方法重现性好、简便、快速、灵敏，为示波测定的实际应用提供了可行的途径。