Conductometric determination of ammonium by a multisyringe flow injection system applying gas diffusion

Abstract

A multisyringe flow injection system (MSFIA) coupled to a gas-diffusion cell has been developed for the conductometric determination of ammonium in different water samples. Operation strategies, membrane, reagent concentrations, and flow rates have been studied to optimize the sensitivity of detection and to fit the required working range. The proposed MSFIA system has been compared with former FIA and SIA systems using gas diffusion. The system was applied to the determination of ammonium in water samples of different matrices in order to evaluate its performance. These samples were coastal waters, pond waters, and compost aqueous extracts. Good recoveries of 102 ± 13% were obtained and no significant differences with the reference methods were found. The system can be used for a wide concentration range of ammonia, from 0.075 to 360 mg L⁻¹, without sample dilution and with a precision better than 2% of RSD. The throughput of the method was 32 injections per hour.

Keywords:

• ammonium
• multisyringe flow injection analysis
• gas diffusion
• conductometric detection
• natural waters

Acknowledgements

This work was supported by the Spanish ‘Ministerio de Ciencia e Innovación’, through the project CTQ2010-15541. C. Henríquez is very grateful to the ‘Conselleria d'Educació cultura I Universitat’ and the ‘Fondo Social Europeo’ for funding her PhD grant.