Potentiometric determination of total nitrogen in soils by flow injection analysis with a gas-diffusion unit

• Type: Article in International Scientific Journal
• Date: 1996

Authors

Ferreira, AMR (Author) Other; Lima, JLFC (Author) FFUP; Rangel, AOSS (Author) Other

Journal

Title: Australian Journal of Soil Research

Vol. 34

Pages: 503-510

ISSN: 0004-9573

Publisher: Commonwealth Scientific and Industrial Research Organization Publishing

Indexing

ISI Web of Knowledge - 13 Citations

Scopus - 16 Citations

Other information

Authenticus ID: P-001-F09

DOI: 10.1071/sr9960503

Abstract (EN): A flow injection analysis (FIA) system incorporating a gas-diffusion unit and a potentiometric detector was developed for the determination of total nitrogen in soil digests. The solutions obtained from the Kjeldahl digestion of the soil samples were injected in the FIA system where ammonium was converted into ammonia. This gas diffused through a gas-permeable membrane to a buffer acceptor stream, allowing the separation of the gas from the rest of the sample. Once in contact with the buffer solution, ammonia was reconverted into ammonium and finally led to a tubular ammonium ion-selective electrode constructed for this purpose. The potentiometric detector is a PVC tubular selective electrode without inner reference solution, and with the sensor system composed of monactin in Tris (2-ethylhexyl) phosphate. Good agreement was obtained between the results provided with the developed FIA system and those from the classical Kjeldahl distillation/titration step, with relative deviations between the 2 methods always < 5%. A sampling rate of 80 determinations/h was achieved with good reproducibility for consecutive injections of soil digests (coefficients of variation < 3%).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8