title: A critical comparison of analytical flow systems exploiting streamlined and pulsed flows.
abstract: 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.
authors.affiliation: Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil.
authors.forename: Ana C B
authors.initials: AC
authors.lastname: Dias
authors.forename: Joâo L M
authors.initials: JL
authors.lastname: Santos
authors.forename: José L F C
authors.initials: JL
authors.lastname: Lima
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Quintella
authors.forename: Angelo M V
authors.initials: AM
authors.lastname: Lima
authors.forename: Elias A G
authors.initials: EA
authors.lastname: Zagatto
mesh_terms: D001961:Bromcresol Green / Q000032:analysis; D002138:Calibration; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D005456:Fluorescent Dyes / Q000737:chemistry; D007834:Lasers; D008956:Models, Chemical; D008962:Models, Theoretical; D008982:Molybdenum / Q000032:analysis; D010710:Phosphates / Q000032:analysis / Q000737:chemistry; D015203:Reproducibility of Results; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013997:Time Factors
chemical_list: D005456:Fluorescent Dyes; D010710:Phosphates; D012996:Solutions; C017541:molybdenum blue; D008982:Molybdenum; D001961:Bromcresol Green