Flow injection system with gas diffusion for the sequential determination of total nitrogen and phosphorus in vegetables |
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Authors: | Jose´ L F C Lima Antoacutenio O S S Rangel M Renata S Souto |
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Institution: | (1) CEQUP/Departamento de Química- Física, Faculdade de Farmácia, Rua Aníbal Cunha 164, P-4050 Porto, Portugal, PT;(2) Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200 Porto, Portugal, PT |
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Abstract: | A flow injection system was developed for the sequential determination of total nitrogen and phosphorus in digests of vegetables
using potentiometric and spectrophotometric detection systems, respectively. A tubular ammonium selective electrode with a
sensor system composed of nonactin/monactin in tris(2-ethylhexyl) phosphate was used. The selectivity limitations of this
electrode were overcome by the inclusion of a gas-diffusion unit in the system that separated ammonium from the rest of the
sample matrix and allowed the determination of total nitrogen and phosphorus by the partition of the sample plug between two
streams.
The results obtained with the developed FIA system were in good agreement with those of the reference methods. Sampling rates
from 40 to 60 samples per hour and relative standard deviations below 3.5% were achieved.
Received: 17 October 1996/Revised: 21 November 1996/Accepted: 27 November 1996 |
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