Analysis of Non-Aromatic Organic Acids in Beer by CE and Direct Detection Mode with Diode Array Detection

A method for the analysis of the main non-aromatic organic acids in beer using capillary electrophoresis is presented. In this work, malic, citric, succinic, pyruvic, acetic and lactic acids are separated using a sodium hydrogen phosphate background electrolyte with direct detection mode with a diode array detector. The separation exhibits lower sensitivity than equivalent methods with indirect detection mode, however, the risk of co-migration with unknown compounds in beer matrixes is significantly reduced. This is due to (i) a higher efficiency (250,000–400,000 theoretical plates), (ii) a higher selectivity than any equivalent method using an indirect detection mode, and (iii) the possibility to monitor other wavelengths in parallel (260 nm for example) to check for possible co-migration with phenolic or benzoic acids. This was critical when working with beer samples as an unknown compound absorbing at 200 and 260 nm was detected in the neighbourhood of malic, citric and succinic acids. Such co-migration will not have been detected using single wavelength detection below 200 nm or indirect detection mode.FCT - POCTI/CTA/48059/2002FCT - SFRH/BPD/30548/2006FCT - SFRH/BD/31056/ 200

Determination of biogenic amines by capillary electrophoresis using a chameleon type of fluorescent stain

A method was developed for the determination of biogenic amines (BAs) via micellar electrokinetic chromatography along with laser induced fluorescence detection using the amino-reactive chameleon stain Py-1. A labeling protocol was established for seven primary BAs by optimizing the reaction conditions in terms of the amount of reagents, reaction temperature, reaction time and solvent. Derivatization was accomplished within 30 min and is visible by the naked eye because it is accompanied by a color change from blue to red. Separation of the labeled BAs was achieved within 15 min with a background buffer of pH 2.5 containing phosphate, Tween®80, and methanol. The LODs range from 0.1 to 0.9 µmol·L−1, with RSDs ranging from 1.1 to 4.2% at 10 µmol·L−1. The method was applied to the determination of histamine in various fish samples