Individual sample conditioning in flow analysis. Determination of N-total in plant materials |
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Authors: | J M T Carneiro R S Honorato E A G Zagatto |
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Institution: | Centro de Energia Nuclear na Agricultura, Universidade de S?o Paulo, P.O. Box 96, Piracicaba SP 13400-970, Brazil e-mail: ezagatto@cena.usp.br, BR
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Abstract: | A flow-batch system allowing in-line individual sample matrix matching is proposed for analysis of sample lots with high
variability in acidity. The feasibility of the approach is demonstrated in the spectrophotometric determination of total nitrogen
in Kjeldahl digests, using a column with a slightly soluble reagent (AgCl). The solutions are sequentially injected by means
of an 8-port selecting valve and processed in a mixing chamber that is also used as a monitoring unit. The system yields reproducible
results (r.s.d. usually < 2.5%) and the sampling rate is 14 samples/h. The analytical curve is linear within 1.00 and 6.00%
N (dry basis), and the regression coefficient is > 0.999 (n = 6). Results are in agreement with certified values of standard
reference materials and with results obtained by conductometry.
Received: 5 April 2000 / Revised: 6 June 2000 / Accepted: 13 June 2000 |
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