In this paper the overall antioxidant power, expressed as Briggs-Rauscher antioxidant index, of decoction or cold infusions of dried Hibiscus sabdariffa flowers was determined at 25 and 37°C, to compare the scavenger ability of the beverages at either room or physiological temperature. Total polyphenol contents and the absorbance of anthocyanin pigments were also determined, and the trend with the overall antioxidant capability is considered. Combined photometric and pH-metric titrations were acquired to obtain information on the colour-total acidity relationship of the product. The results show that the decoction preparation protocol provides karkadè with the highest nutritional value and that the polyphenol content can account for the antioxidant capability of H. sabdariffa-based beverages. Moreover, a quantitative relationship between acid-base and redox chemistry was found. The H. sabdariffa-based drinks can be considered as protective beverages and a regular consumption of karkadè might be proposed to ensure protection against free radicals.

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In this paper we report the results of an investigation performed by potentiometric (H+-glass electrode) and visible spectrophotometric measurements on the interaction of UO2(2+) ion towards some carboxylic ligands (acetate, malonate, succinate, azelate). The measurements were carried out at T= 25 degrees C in different ionic media (KNO3 and NaCl) at different ionic strengths (0.1 < or = I/mol L(-1) < or = 1.0, NaCl; I/mol L(-1) = 0.1, KNO3). The dependence on ionic strength of formation constants was taken into account by using both a simple Debye-Hückel type equation and the SIT (Specific ion Interaction Theory) approach. Different speciation models (depending on concentration of reagents, ionic strength, pH-range) both for different carboxylates and different ionic media have been obtained. Linear combinations between formation constants, stoichiometric coefficients and length of alkyl chain of dicarboxylates have been observed and predicted formation constants at I= 0 mol L(-1) are reported for the interaction of UO2(2+) with HOOC-(CH2)n-COOH with 1 < or = n < or = 7. Finally, a visible absorption spectrum for each complex reaching a significant percentage of formation in solution (KNO3 medium) has been calculated to characterise the compounds found by pH-metric refinement.

When irradiated in paddy-field water, propanil (PRP) undergoes photodegradation by direct photolysis, by reactions with OH and CO, and possibly also with the triplet states of chromophoric dissolved organic matter. Irradiation also inhibits the nonphotochemical (probably biological) degradation of PRP. The dark- and light-induced pathways can be easily distinguished because 3,4-dichloroaniline (34DCA, a transformation intermediate of considerable environmental concern) is produced with almost 100% yield in the dark but not at all through photochemical pathways. This issue allows an easy assessment of the dark process(es) under irradiation. In the natural environment, we expect PRP photodegradation to be important only in the presence of elevated nitrate and/or nitrite levels, e.g., [NO] approaching 1 mmol L (corresponding to approximately 60 mg L). Under these circumstances, OH and CO would play a major role in PRP phototransformation. Because flooded paddy fields are efficient denitrification bioreactors that can achieve decontamination of nitrate-rich water used for irrigation, irrigation with such water would both enhance PRP photodegradation and divert PRP dissipation processes away from the production of 34DCA, at least in the daylight hours.

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The redox and acid-base reactivity of red wines was studied from both the analytical and kinetic standpoint. Four homemade wines, made from Italian red grape varieties of two different vintages, were tested to study the effect of temperature (25 and 37 degrees C) on the overall antioxidant power, through the Briggs-Rauscher oscillating reaction. The reaction was monitored by potentiometry (platinum electrode) and by direct chronometric detection. A reference scale based on the response of gallic acid was also employed, so as to achieve a quantitative evaluation: the novel Briggs-Rauscher antioxidant index (BRAI) was developed to express the overall antioxidant power quantitatively versus the chosen standard molecule. Overall antioxidant power was found to be related to total polyphenol content measured using the Folin-Ciocalteu method: the older wines had a lower antioxidant ability. Total acidity was also estimated indirectly by means of coupled pH-metric/photometric titrations and visible spectrophotometric measurements; it revealed an overlap between acid-base and redox chemistry of red wine.

The valorization of olive oil mill solid wastes (OMW) has been addressed by considering it as a possible source of humic-like substances (HLSs), to be used as auxiliary substances for photo-Fenton, employing caffeine as a target pollutant to test the efficiency of this approach. The OMW-HLS isolation encompassed the OMW basic hydrolysis, followed by ultrafiltration and drying. OMW-HLS structural features have been investigated by means of laser light scattering, fluorescence, size exclusion chromatography, and thermogravimetric analysis; moreover, the capability of OMW-HLS to generate reactive species under irradiation has been investigated using spin-trap electronic paramagnetic resonance. The caffeine degradation by means of photo-Fenton process driven at pH = 5 was significantly increased by the addition of 10 mg/L of OMW-HLS. Under the mechanistic point of view, it could be hypothesized that singlet oxygen is not playing a relevant role, whereas other oxidants (mainly OH • radicals) can be considered as the key species in promoting caffeine degradation.