A polyvalent ¯ow injection system for multielemental spectrophotometric analysis of plant materials 1 F.V. Silva 2 , A.R.A. Nogueira a,* , G.B. Souza a , E.A.G. Zagatto b a Empresa Brasileira de Pesquisa Agropecua Âria ± Centro de Pesquisa de Pecua Âria do Sudeste, P.O. Box 339, Sa Äo Carlos SP 13560-970, Brazil b Centro de Energia Nuclear na Agricultura, Universidade de Sa Äo Paulo, Piracicaba SP, Brazil Received 5 December 1997; received in revised form 3 April 1998; accepted 8 April 1998 Abstract A polyvalent ¯ow injection system consisting of a single manifold suitable to perform different determinations after only minor adaptations was conceived. Its use is particularly attractive for laboratories processing a large number of samples including several analytes. The system was applied to spectrophotometric determination of iron, copper, manganese and zinc (micronutrients) as well as calcium, magnesium and phosphorus (macronutrients) in plants. With the proposed system, slight variations in the coef®cients of the calibration equations (usually <3%) were found after 4 h working periods. Results were precise (0.8%<r.s.d.<4.3%) and in agreement with certi®ed values of standard reference materials. The system was designed for spectrophotometric large scale analyses, and no major problem was observed, emphasising the stability, simplicity, robustness and versatility inherent to ¯ow systems. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Flow injection analysis; Polyvalent system; Plant analysis; Spectrophotometry 1. Introduction Requests for determination of iron, copper, man- ganese and zinc in plant materials are increasing mainly in view of their relevance in plant nutrition studies. The problem becomes critical in situations of low soil fertility and when more productive varieties with high mineral requirements are included to the productive system [1]. Regarding determinations of these micronutrients, proposals to improve sensitivity and to reduce the time required for analysis have been often presented [1]. Calcium, magnesium and phos- phorus determinations have also been increasingly solicited [2]. A number of analytical procedures for spectropho- tometric ¯ow injection determination of these ele- ments in plant materials have been developed [3±10], and a tendency towards a speci®c manifold for each analyte is pronounced, although some of them have been simultaneously determined [8±10]. A literature survey reveals that several of the above mentioned chemical species have been determined with similar manifolds which could be scaled. In this way, a polyvalent system could be designed and some of the previously established procedures adapted in a Analytica Chimica Acta 370 (1998) 39±46 *Corresponding author. Tel.: +55 16 2615611; fax: +55 16 2615754; e-mail: anarita@cppse.embrapa.br 1 This paper was presented at the Flow Analysis VII conference held in Piracicaba, Brazil from 23±26 August 1997. 2 Graduate student at Universidade Federal de Sa Äo Carlos SP (Brazil). 0003-2670/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved. PII S0003-2670(98)00242-6