A capillary electrophoresis method with UV detection is proposed for the identification and quantitation of bacterial contamination in food samples. The electrophoretic separation relies on the differential mobility of bacteria in the capillary. Electrophoretic resolution is improved by using calcium and myoinositol hexakisphosphate as specific ions that interact with the bacterial surface changing its electrical properties and electrophoretic mobility. The proposed method allows the effective separation of eight different types of bacteria in only 25 min. It was successfully used to detect the presence of bacteria in contaminated food. The precision of the analysis of real spiked samples ranges from 3.3 to 7.0%, and the overall analysis time is 7 h, which is much shorter than the 24-48 h typically required for plate counts. The validity of the method was established by comparison with the standard plate counting method.

A TTF-TCNQ/PVC composite electrode is proposed as a voltammetric cation and anion sensor. The electrode relies on the principle that, during redox processes involving the TCNQ 0/À couple for cations and the TTF þ/0 couple for anions, electrolyte ions are included into lattice sites in the charge neutralization process. This voltammetric ionsensor provides results that are similar to those of sensors based on two electrodes (viz. one modified with TCNQ for cations and another modified with TTF for anions) but with some practical advantages over them.

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The biological activity of polyphenols extracted from grape marc was studied with a view to finding a new use for this winery waste. Polyphenols were extracted by using an alternative supercritical-fluid extraction method based on the use of a liquid trap that allows extracted polyphenols to be retained in a saline buffer, thus avoiding the need for the organic solvent required to elute polyphenols from a solid trap. The major extraction variables influencing the performance of the liquid trap (viz. CO(2) modifier content, flow-rate, extraction time and trap volume) were optimized. The proposed method was applied to the supercritical-fluid extraction extraction of 0.3 g grape marc with CO(2) modified with 3% methanol at 350 bar at 50 degrees C (CO(2) density 0.9 g mL(-1)) for 20 min, using a liquid flow-rate of 0.9 mL min(-1). The polyphenol extracts thus obtained exhibited cytotoxic effects that induced apoptosis in tumour cells.

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