Antioxidant activity has been assessed in many ways. The limitation of many newer methods is the frequent lack of an actual substrate in the procedure. The combination of all approaches with the many test methods available explains the large variety of ways in which results of antioxidant testing are reported. The measurement of antioxidant activities, especially of antioxidants that are mixtures, multifunctional or are acting in complex multiphase systems, cannot be evaluated satisfactorily by a simple antioxidant test without due regard to the many variables influencing the results. Several test procedures may be required to evaluate such antioxidant activities. A general method of reporting antioxidant activity independent of the test procedure is proposed.

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view; liquid c h ro m a tog rap h y; me ta I ions; (me ta I) specia ti0 n ; co m plexa ti0 n

of Contents Introduction Liquid chromatographic separations Paper chromatography and thin-layer chromatography Column chromatography Displacement chromatography Adsorption and partition Ion-pair chromatography Cation exchange Anion exchange and chelating ion exchange Ion chromatography Extraction chromatography Gradient elution Detection systems Gas chromatographic separations Thermal properties Gas chromatography Other chromatographic and related techniques Thermochromatography Supercritical f I u id ch romatog rap hy Zone electrophoresis and isotachophoresis Ana I yt ica I a pp I icat io ns

Headspace analysis by gas chromatography (GC) and gas chromatography‐mass spectrometry (GC‐MS) has been used to identify and quantify volatiles formed in the oxidative deterioration of corn chips. The effect of light and temperature on the formation of propanal, pentanal and hexanal in stored chips was examined and the data correlated with the results of sensory evaluation. The procedure is suitable for determining concentrations of pentanal and hexanal below, one ppm, which is below the level where rancidity based on sensory evaluation is detected. Problems associated with solute partitioning and sample decomposition in the analysis also were investigated.