Analysis of Caffeine in Dietary Products by Multiple Injection Capillary Electrophoresis - Caffeine: Chemistry, Analysis, Function and Effects - page 161

d n 0 t 2 n g | 4

Figure 9.3 Multiple- injection capillary electrophoresis mode I. Schematic illustra-

tion of the multiple-injection technique mode I (A), applied to the assay
of caffeine in the dietary products (B). Five analyte samples, consisting of
caffeine and acetaminophen were analyzed simultaneously (B). The
hydrodynamically injected sample plugs were subjected to the partial
electrophoresis for 2.2 minutes in order to be isolated from the previously
injected plugs. Operation conditions 15 mg mL -1 sulfated b-cyclodextrin
(S-b-CD). The separations were performed in a 75 cm fused silica
capillary of dimensions: 50 mm 6 65 cm (effective length); Applied
voltage 25 kV; Hydrodynamic injection (0.1 psi) for 10 seconds; BGE 50
mM phosphoric acid (pH 7.0) containing 10% ACN (v/v %), 15 mg m S-
b-CD and 20 mM NaCl; capillary temperature 20 o C; UV detection at
270 nm. Peaks: 0, water; 1, caffeine; 2, acetaminophen.

The developed multiple-injection CE method was considered to be a simple
and fast method for the assay of caffeine. The method was therefore validated
according to the ICH guide line with respect to linearity, precision,
intermediate precision, reproducibility, accuracy, robustness, limit of detection
(LOD) and limit of quantification (LOQ).