ABSTRACT
In flow analysis, solid particles (sorbents, reagents or catalysts) have been used for e.g. analyte separation/concentration, sample clean-up, speciation analysis, enzymatic assays, analysis relying on slight soluble reagents, and kinetics studies related to adsorption/release of species. The particles are usually accommodated inside packed-bed mini-columns, cartridges or disks, but this geometry may led to limited analyte/particle interaction, poor renewal of the particle surface, swelling effects, establishment of preferential pathways, and increased backpressure. These hindrances are circumvented by fluidizing the solid particles. Fluidization is a worldwide-accepted industrial process, which can be successfully implemented in flow analysis. This review emphasizes historical and conceptual aspects, as well as advantages, limitations, applications, and perspectives for future development of flow analysis relying on fluidized particles.
ABSTRACT
An advanced strategy involving concentric tubes is proposed for fast and controlled heating (or cooling) of the reaction medium in flow analysis. Different temperatures are set by sequentially circulating two thermostated water streams through the outer larged bore (2.0mm i.d.) silicone tube, which acted as a water-jacket of the inner (0.8mm i.d.) PTFE tube, and directing the sample zone to flow through it. Each end of the outer tube is connected to a three-way valve that selects the stream to flow inside it. For 25-85cm tube lengths and a 12.0mLmin-1 flow rate, the time interval required for temperature attainment, and the uniformity of temperature along the tube were evaluated. For the 85-cm tube, low differences in temperatures along the coil (1.1-8.7°C) and between programmed and attained values (2.3-13.4°C) were noted within a wide range of pre-set temperatures (15-75°C). The feasibility of the innovation in flow analysis was demonstrated in a model system relying on the iodide-nitrite reaction. The strategy allows fast (15-120s) thermostating of the reaction medium in a versatile and simple way, and is especially attractive when two controlled temperatures are set during the analytical course. Potentialities and limitations of the innovation are discussed.
