Trace Levels Determination of Ammonium by Flow Injection Analysis Using Gas‐Diffusion and Capacitively Coupled Contactless Conductivity Detection

Abstract

A sensitive analytical method based on gas-diffusion flow injection system for ammonium ion determination at trace levels with capacitively coupled contactless conductivity detection (C 4 D) is described. The effects of the chemical composition of the acceptor stream, operating frequency of the conductivity detector, acceptor and donor flow rates, injected volume, and some potential interferents were evaluated. By injecting 100 mL samples, the analytical method showed linear response for ammonium from 2.0 up to 100 mmol L À1 and a limit of detection of 0.8 mmol L À1(14 ppb). At a flow rate of 0.10 mL min À1 for the acceptor solution, an analytical throughput of 35 injections per hour was achieved. The new flow injection system was successfully applied for ammonium determination in rainwater from S¼o Paulo city.

Contactless conductivity detection for analytical techniques: Developments from 2010 to 2012

“…Applications of C 4 D without electrophoretic or chromatographic separation include flow injection analysis (FIA) , SI analysis , and other methods operating with liquid or even gaseous flows. FIA was also used in the testing of C 4 D on a microfluidic device using simple salt solutions at different concentrations .…”

“…Ammonium in the sample was volatilized when transported through the gas diffusion cell and trapped into an acidic acceptor solution on the other side of the cell. The acceptor solution was then directly delivered to the C 4 D for sensitive NH 4 + determination . A schematic of this system is shown in Fig.…”

“…Gas‐diffusion flow injection analysis system for the determination of dissolved ammonia reported by B raz et al . Reproduced with permission from W iley.…”

Conductometric determination of ammonium ion with a mobile drop

“…Conductometry, normally a nonselective technique, has been used with a FI-GDU system for measuring Kjeldahl Nitrogen in milk and chicken digests [5]. Contactless conductometry works particularly well with small bore tubing; this has also been used for NH þ 4 determination with a FI-GDU system [6]. Other automated flow methods, e.g., sequential injection [7], multi syringe FI [8,9], and multi-commutation FI [10,11] have all been used with a GDU and spectrophotometric NH þ 4 determination.…”

Determination of Ammonium Concentration in Post-Process Waters from Underground Coal Gasification

“…Determination of ammonium by flow injection analysis with gaseous diffusion (FIA-GD) and spectrophotometric detection allows avoid matrix problems, therefore it became very popular among different FIA methods [6,7]. However, many other flow systems for determination of ammonium with different kinds of detection [8][9][10][11][12] or flow systems coupled with other methods are also presented in literature [13,14]. FIA-GD is a technique based on injection of a liquid sample volume into a moving non-segmented carrier stream.…”