Determination of ammonia in water and industrial effluent streams with the indophenol blue method using sequential injection analysis
ABSTRACT A suitable sequential injection analysis (SIA) analyser to monitor water quality in terms of the ammonia content in water and industrial effluent streams was developed. The system is fully computerised and is able to monitor ammonia in samples at a frequency of ca. 16 samples per hour with a relative standard deviation better than 1.8%. The calibration curve is linear between 0 and 50 mg l−1 which falls within the required analyte range. The levels of possible interferants in the water and industrial effluent streams were negligible to cause any interference on the proposed system.
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ABSTRACT: The use of the enzyme alanine dehydrogenase (AlaDH) for the determination of ammonium ion (NH(4)(+)) usually requires the addition of pyruvate substrate and reduced nicotinamide adenine dinucleotide (NADH) simultaneously to effect the reaction. This addition of reagents is inconvenient when an enzyme biosensor based on AlaDH is used. To resolve the problem, a novel reagentless amperometric biosensor using a stacked methacrylic membrane system coated onto a screen-printed carbon paste electrode (SPE) for NH(4)(+) ion determination is described. A mixture of pyruvate and NADH was immobilized in low molecular weight poly(2-hydroxyethyl methacrylate) (pHEMA) membrane, which was then deposited over a photocured pHEMA membrane (photoHEMA) containing alanine dehydrogenase (AlaDH) enzyme. Due to the enzymatic reaction of AlaDH and the pyruvate substrate, NH(4)(+) was consumed in the process and thus the signal from the electrocatalytic oxidation of NADH at an applied potential of +0.55 V was proportional to the NH(4)(+) ion concentration under optimal conditions. The stacked methacrylate membranes responded rapidly and linearly to changes in NH(4)(+) ion concentrations between 10-100 mM, with a detection limit of 0.18 mM NH(4)(+) ion. The reproducibility of the amperometrical NH(4)(+) biosensor yielded low relative standard deviations between 1.4-4.9%. The stacked membrane biosensor has been successfully applied to the determination of NH(4)(+) ion in spiked river water samples without pretreatment. A good correlation was found between the analytical results for NH(4)(+) obtained from the biosensor and the Nessler spectrophotometric method.Sensors 01/2011; 11(10):9344-60. · 1.95 Impact Factor
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ABSTRACT: A novel flow injection-gas-diffusion (GD-FI) system has been developed for the on-line analysis of ammonium ion in waters with fluorimetric detection, using an acceptor solution containing the Eosin-Bluish (EB) acid-base indicator. This, together with optimization of the process of gas transfer through the membrane, increases the sensitivity of the method to a considerable extent. Under optimum conditions, it is possible to determine the analyte within the 0.02-1.5 mg l(-1) range, with a limit of detection of 5 microg l(-1) and relative standard deviations (n = 12, [NH (4) (+) ] = 50 microg l(-1) and 0.05 microg l(-1)) of 3.4% and 3.0% respectively. The determination rate was 15 samples per hour.Journal of Fluorescence 08/2009; 20(1):55-65. · 1.79 Impact Factor
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ABSTRACT: Environmental Context. Eutrophication is a growing problem globally, and it has significant ecological and socio-economic consequences. Understanding the causes of eutrophication requires a knowledge of nutrient biogeochemistry in aquatic systems. Owing to the high spatial and temporal variability of nutrients in these systems, there is a need for autonomous in situ measurement techniques with rapid response and the ability to collect long-term data. Flow injection analysis is one technique that meets these demands. Abstract. Flow analysis offers a versatile and powerful approach to monitoring of the aquatic environment. The present review highlights the drivers for determining macro- and micro-nutrients in marine and fresh waters, and outlines the instrumental requirements for in situ instrumentation. The principles of flow analysis, specifically flow injection and derivative techniques, and the chemical bases for macro- and micro-nutrient detection are discussed, and key examples of suitable approaches are considered. The successful deployment of flow analysis nutrient monitoring systems for spatial and temporal measurements is illustrated by specific examples relating to surface transects, depth profiles and temporal deployments. Finally, the challenges and imperatives of research in this area are outlined.Environmental Chemistry - ENVIRON CHEM. 01/2006; 3(1).