Dias Ana C B, Santos Joâo L M, Lima José L F C, Quintella Cristina M, Lima Angelo M V, Zagatto Elias A G
Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil.
Anal Bioanal Chem. 2007 Jul;388(5-6):1303-10. doi: 10.1007/s00216-007-1304-1. Epub 2007 May 24.
Multipumping (MPFS) and multicommuted (MCFS) flow systems relying on pulsed and laminar flows were critically compared. The mixing conditions and dispersion associated with both systems were evaluated by simulating the sample with bromocresol green. The molybdenum blue method for phosphate determination in soil extracts was also implemented in both flow systems. Furthermore, laser-induced fluorescence (LIF) was applied to visualize the dispersing sample; rhodamine B was used as the fluorescent species. The pulsed flow enhanced the mixing of the solutions involved, thus reducing reagent consumption (48 and 96 microl for MPFS and MCFS), and improving sampling rate (67 and 144 h(-1) for MCFS and MPFS). For phosphate determination, results obtained with both systems were precise (r.s.d. < 0.5%; n = 10) and accurate. Analyses of the absorbance vs time/space LIF plots revealed that exploitation of pulsed flow led to a pronounced radial dispersion and to a limited axial dispersion, typical aspects of turbulent flows.
