A flow system with zone merging and zone trapping in the main reactor applied to spectrophotometric catalytic determination of cobalt in grasses

A flow system with zone merging and zone trapping in the main reactor was proposed. The sample and reagent inserted aliquots merge together and the resulting zone is directed towards a displaceable reactor inside which its most concentrated portion is trapped. After the pre-set TRAP period, the handled sample is released towards detection. A comparison with an analogous flow system exploiting zone stopping revealed the superior characteristics of sampling rate and system operation; moreover, the sample inserted volume plays little influence on sampling rate. The system was applied to the spectrophotometric determination of cobalt in pastures, and enhanced figures of merit (sampling rate=18 h−1; peak height r.s.d.=0.7%, detection limit=0.046 μg L−1 Co; reagent consumption=330 μg of Tiron per measurement; 98%<recovery<114%) were estimated.