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A liquid chromatographic method with online photometric and luminescent detection for the determination of 18 phenolic compounds in wines is reported. Photometric detection is performed at four wavelengths, namely, 256, 280, 320, and 365 nm, using a diode array detection system. The luminescent detection is achieved by means of a postcolumn derivatization reaction of 10 of these compounds with terbium(III) in the presence of synergistic agents, such as ethylenediaminetetraacetic acid (EDTA) and n-octyltriphosphine oxide (TOPO). A micellar medium provided by the surfactants sodium dodecyl sulfate and Triton X-100 was used for the determination of the luminescent chelates at lambdaex 317 and lambdaem 545 nm. The long wavelength emission of lanthanide chelates can minimize interferences from background sample matrix, which usually emit at shorter wavelengths. The analytical features of the photometric and fluorometric methods, such as dynamic ranges of the calibration graphs, detection limits, and precision data, have been obtained. The practical usefulness of the developed methods is demonstrated by the analysis of Spanish and Italian wine samples (red, rosé, oloroso, and white), which were diluted and directly injected into the chromatographic system. The accuracy of both methods was checked by assaying a recovery study, which was performed at three different analyte levels for each type of sample.

The capability of antioxidant compounds to reduce gold(III) to gold nanoparticles (AuNPs) has been kinetically studied in the presence of cetyltrimethylammonium bromide using stopped-flow mixing technique and resonance light scattering as detection system. This study has given rise to a simple and rapid method for the determination of several synthetic and natural antioxidant used as additives in foodstuff samples. The formation of AuNPs was monitored by measuring the initial reaction-rate of the system in about 5 s, using an integration time of 0.1 s. Dynamic ranges of the calibration graphs and detection limits, obtained with standard solutions of the analytes, were (µmol L -

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A new post-column derivatization system is described and applied to the determination of flavonoids in citric beverages after their separation by LC using a monolithic column. The derivatization involves the formation of the chelates of the analytes with aluminum (III) and terbium (III) in the presence of the surfactant SDS and the measurement of the terbium sensitized luminescence at lambda(ex) 360 and lambda(em) 545 nm. Naringin, hesperidin, quercetin, naringenin, and kaempferol have been chosen as analyte models. The large Stokes shift and the relatively long wavelength emission of terbium(III) can minimize interferences from background sample matrix, which usually emit at shorter wavelengths. Calibration graphs were constructed in the intervals 6.0-1700 ng/mL naringin, 9.8-1700 ng/mL hesperidin, 2.1-2000 ng/mL quercetin, 5.2-1500 ng/mL naringenin and 2.5-2000 ng/mL kaempferol, with regression coefficients higher than 0.9935 in all instances. The precision of the method, expressed as RSD%, was established at two concentration levels, with values of 1.3 and 4.7%, which corresponded to the minimal and maximal error zones of the calibration graphs. The practical usefulness of the method is demonstrated by the analysis of orange juices, which were diluted and directly injected into the chromatographic system, obtaining recoveries between 86.9 and 108.2%.