The aim of this work was to determine the selenium content in nut samples by cathodic stripping potentiometry. Dry-powdered nuts were digested by HNO(3) and dissolved with concentrated hydrochloric acid. To avoid the interference of natural oxygen, the potentiometric determination of selenium was carried out in an electrolyte solution consisting of 2 M CaCl(2) and 4 M HCl. The analysis was executed applying an electrolysis potential of -150 mV for 60 s and a constant current of -30 microA. Under these conditions, detection limits lower than 1.0 ng g(-)(1) were obtained for selenium analysis in nuts. The relative standard deviation of these measurements (expressed as rsd %) ranged from 0.44 to 0.88% while recoveries ranged from 90.2 to 95.3%. The results obtained with the proposed method were compared with those obtained via hydride vapor generation atomic absorption spectroscopy, a common method for determining selenium. The results of the two methods agreed within 5% for almond, hazelnut, and pistachio samples. The mean concentrations of selenium determined in Sicilian samples of almond, hazelnut, and pistachio were 531 +/- 1, 865 +/- 1, and 893 +/- 4 microg/kg, respectively.

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The purpose of this paper was to use adsorptive stripping chronopotentiometry for the determination of Ni (II) in worldwide consumed beverages without any sample pretreatment, using dimethilglyoxime (DMG) as complexing agent and a glassy carbon mercury film electrode as the working electrode. Ni (DMG)2 complex is adsorbed onto the mercury film at an electrolysis potential of -500 mV for 60 s and then reduced by a -5 microA constant cathodic current. The sensitivity of the method was studied for certified reference water and black tea in the pH range 6.5-11. At pH 9.5 in ammonia buffer, a detection limit of 0.2 microg L(-1) was achieved; the instrumental precision (expressed as rsd %) was 1.5%, and the accuracy, expressed as obtained recoveries both from certified and not certified matrixes, ranged from 93.0 to 95.5 %. The chronopotentiometric analysis executed on commercial beverages provided evidence that black tea samples were the richest source of Ni (II) (1500-3700 microg L(-1)), followed by coffee (100.0-300.5 microg L(-1)); bottled mineral water showed a Ni (II) concentration lower than 4.6 microg L(-1). Among alcoholic beverages, red wines presented the highest content of Ni (II) (55.5-105.0 microg L(-1)). Significant differences were noticed between Ni (II) levels of fermented and distillated alcoholic beverages; moreover, canned cola and beer did not show higher Ni (II) levels with respect to the glass-bottled products.

Contaminants belonging to various classes, including polychlorobiphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), organophosphorus pesticides (OPPs), pyrethroid insecticides (PYRs), fungicides (Fs), herbicides (Hs), synergists (SYNs) and insect growth regulators (IGRs) were analysed simultaneously in honey samples using a new simultaneous, easy and rapid method based on a liquid-liquid extraction with a mixture of n-hexane and ethyl acetate. It allowed recoveries in the range 80-137%, with limits of detection (LODs) between 0.10 and 5.21 ng g, showing a good sensitivity and accuracy. All the analysed Italian honeys showed the presence of residues of OPPs; PAHs were in 46.8% of the samples and PCBs were always below the LODs; 53.2% of the samples were contaminated by OCPs, PYRs, SYNs and IGRs. In addition, 46.8% of the samples exceeded the maximum residue limits (MRLs) established by the European Community in honey for chlorfenvinphos (cis + trans), TPP, γ-HCH, tebuconazole, coumaphos and τ-fluvalinate (cis + trans).

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