Analysis of Caffeine and Related Compounds by Automated Flow Methods - Caffeine: Chemistry, Analysis, Function and Effects - page 198

d n 0 t 2 n g | 3

Figure 11.3 Representative multicommutation flow manifold. In multicommutated

flow systems all actions are carried out by the precisely time-based
controlled operation of solenoid valves that are strategically positioned
in the flow network: (a) flushing with carrier (C) through valve V1; (b)
injection of first sample zone (S) through valve V2; (c) injection of
reagent (R) through valve V3; (d) injection of second sample zone (S)
through valve V2. (With permission from Elsevier, Rocha et al 2002).

tion flow setups. A typical multicommutation flow configuration including
injection of sample (b) and (d) and reagent (c) in a ''sandwich'' format is
depicted in Figure 11.3 (a)-(d). Multicommutation enables increased repeat-
ability, easier sample handling, and reduced reagent consumption, providing
an invaluable tool to develop environmentally friendly methods, which
provides benefits in terms of reagent waste generation or sample-reagent
consumption (Garci´a-Reyes et al 2006).

11.3 Determination of Caffeine and Related Compounds
by Coupling of SI/FI to Separation Techniques
Historically, one of the major challenges of flow injection based techniques is
the ability to simultaneously analyze mixtures of more than one analyte in
complex matrices. Despite the numerous ingenious approaches towards this
direction based on e.g. kinetic discrimination, sample splitting and so on
(Hlabangana et al 2006), the most straightforward and viable solution appears
to be the direct coupling of flow injection techniques to separation ones
(HPLC, GC, CE). The hyphenated analytical schemes combine the separation