Sequential injection analysis of selected components in liquid fertilizers

Abstract

Sequential injection has, over the past eight years, developed into a viable alternative to flow-injection, but its full potential has not yet been fully realized. It developed out of existing flow-injection methods when a need for mechanically simple and robust flow-injection methodology arose. In this study the development of this method is discussed with its numerous advantages and disadvantages over existing flow-injection methods. The theoretical basis on which this technique is based is outlined as well as parameters that influence the design of the manifold. With the manifold design principles established, the manifold is evaluated using real sample analysis, with liquid fertilizer as the source of selected elements. Adjustments made to existing flow-injection methods, for the determination of nitrite with sequential injection analysis, are discussed, while a new method is proposed for nitrate determination. The viability of solid-phase reductors and in situ preparation of reagents, combined with sequential injection analysis, is also studied.