Multipurpose flow injection system. Part 1. Programmable dilutions and standard additions for plant digests analysis by inductively coupled plasma atomic emission spectrometry

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Abstract
A flexible flow injection system to perform multipurpose functions related to sample handling is proposed. The flow network consists of a sliding injector commutator, solenoid valves and other minor components. A dedicated microcomputer controls these devices, facilitating the definition of different flow configurations. Merging zones, zone sampling, intermittent flow, sequential injections, zone trapping and stopped flow are possible. On-line programmed dilutions and standard additions for simultaneous determinations on plant digests by inductively coupled plasma atomic emission spectrometry were chosen to demonstrate some features of the system. Sample dilutions were accomplished by confluence at different points along the analytical path through a proper programming of the solenoid valves. Standard additions were performed by merging the sample zone with an aliquot delivered from a trapped standard zone in a modified version of the zone sampling process. In order to minimize matrix effects from the nitric–perchloric acid digests, a sequential dilution procedure is proposed for the major elements and standard additions for the minor constituents. No other standardization procedure was necessary and results were calculated by using the least squares regression method. Results obtained with the proposed procedure compared well with the reported values for plant reference materials.