Modified micellar electrokinetic chromatography in the analysis of catechins and xanthines in chocolate

Abstract

Modified micellar electrokinetic chromatography (MEKC) analysis of monomeric flavanols (catechin and epicatechin) and methylxanthines (caffeine and theobromine) in chocolate and cocoa was performed by using sodium dodecyl sulfate (SDS) as a principal component of the running buffer. Because of the reported poor stability of catechins in alkaline solutions, acidic conditions (pH 2.5) were chosen and consequently the electroosmotic flow (EOF) was significantly suppressed; this resulted in a fast anodic migration of the analytes partitioned into the SDS micelles. Under these conditions, variations of either pH value in acidic range or SDS concentration, showed to be not suitable to modulate the selectivity. To overcome this limit, use of additives to the SDS-based running buffer was successfully applied and three different systems were optimized for the separation of (+)-catechin, (-)-epicatechin, caffeine, and theobromine in chocolate and cocoa powder samples. In particular, two mixed micelle systems were applied; the first consisted of a mixture of SDS and 3-[(3-cholamidopropyl)dimethylammonio]-1-propansulfonate (CHAPS) with a composition of 90 mM and 10 mM, respectively; the second was SDS and taurodeoxycholic acid sodium salt (TDC) with a composition of 70 mM and 30 mM, respectively. A further MEKC approach was developed by addition of 10 mM hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to the SDS solution (90 mM); it provided a useful cyclodextrin(CD)-modified MEKC. By applying the optimized conditions, different separation profiles of the flavanols and methylxanthines were obtained showing interesting potential of these combined systems; their integrated application showed to be useful for the identification of the low level of (+)-catechin in certain real samples. The CD-MEKC approach was validated and applied to the determination of catechins and methylxanthines in aqueous extracts from four different commercial chocolate types (black and milk) and two cocoa powders.

Recent advances in the application of capillary electromigration methods for food analysis

“…Thus, grapes and wines [56][57][58][59][60][61], plants (including spices and medicinal herbs) [62][63][64][65][66][67][68], different teas [58,69,70], and olive oils [71][72][73][74] are the sources of phenols, polyphenols and pigments mainly investigated. However, some others natural samples such as berries [75], fruits [76,77], soy [78], alga and microalga [79,80] and chocolate [81] have also been analyzed by CE.…”

Cafeína: revisão sobre métodos de análise

“…A detecção foi conduzida no comprimento de onda de 210 nm. A CCEM também foi aplicada na multianálise de flavonóides monoméricos (catequina e epicatequina) e metilxantinas (cafeína e teobromina) em chocolate e cacau 64 . Devido à baixa estabilidade das catequinas em pH alcalino, o procedimento analítico foi conduzido em pH ácido (pH = 2,5).…”

Optimization of the separation of flavonoids using solvent‐modified micellar electrokinetic chromatography

“…A recent example of RF-MEKC separation of flavonoidrelated compounds (catechins and also xanthines) is reported by Gotti and collaborators [13]. The separation mode was chosen as a result of the catechins instability at high pH.…”