International Congress BIOLOGICAL PRODUCTS - Gruppo di ...

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INFLUENCE OF DIFFERENT TREATMENTS ON Cd (II), Cu (II), Pb (II) AND Zn (II) CONTENT IN
SICILIAN OLIVE OILS
La Pera Lara, Lo Turco Vincenzo, Lo Curto Simona, Mavrogeni Ekaterini, Dugo Giacomo
Dipartimento di Chmica Organica e Biologica Università di Messina Salita Sperone, 31, 90166 S. Agata-
Messina
Metals can be found in fatty food as edible oils that are often subjected to refining, bleaching, and
deodorization, during which they inevitably come in contact to metallic surfaces (1). Trace levels of some metal
ions like Cu (II) could catalyse the oxidation reaction of fatty acid chains, with conseguent a deleterious effect on
oil flavor and shelf-life of oils (2).
Metals contamination of olive oil could be due to their presence in the soil, water and, particularly for
lead, in the air (3). Many studies have been carried out in which the presence of trace metals in olive oils was
correlated to agronomical techniques, harvesting methods, oil extraction and packaging procedures (4, 5). The
purpose of this paper was to explore the correlation between the pesticide treatments occurred in olive growing
and the content of metals found in oils.
The analytical techniques frequently used for the subsequent determinations are emission and absorption
spectrophotometric techniques as well as electroanalytical techniques (2,6).
In this paper derivative potentiometric stripping analysis (dPSA) was used to determine copper (II), lead
(II), cadmium (II) and zinc (II), in samples of virgin olive oils from Sicily (7-9).
MATERIALS AND METHODS
Samples
Seven olive oils samples belonging to Nocellara del Belice variety, produced in the crop year 2000 -2001
from plants grown up on sandy soils in the zone of Valle del Belice (Trapani), were studied. Each of these
samples was originated from olive grove subjected to different pesticides treatments as dimethoate/fenthion,
dimethoate, copper oxy-chlorine/dimethoate, copper oxy-chlorine/fenthion; biological treatments as copper oxychlorine
and biological fight and no treatment.
Oil samples were stored in dark glassy bottles at 4°C for the time of analysis.
Chemicals
Ultra pure hydrochloric acid (34-37%), Hg (II) (1000 µgmL -1 , 1M in hydrochloric acid) and Cd (II), Cu
(II), Pb (II), Zn (II), Ga (III) and Pd (II) (1000 µg mL -1 , 0.5 N in nitric acid) standard solutions were purchased
by Panreac Quimica (Barcelona, Spain). The extracts are filtrated on a carbon column Supelclean ENVI-Carb
SPE (0.5 g, 6 mL), purchased by Supelco (Bellefonte, PA, USA).
Apparatus
Determinations were carried out using a PSA ION 3 potentiometric stripping analyzer (Steroglass, S.
Martino in Campo, Perugia, Italy), connected to an IBM-compatible personal computer. The analyzer operated
under the control of the NEOTES software package (Steroglass).
Electrode Preparation (plating) and potentiometric determination
Working electrode was a glassy carbon electrode coated with a Hg film, the reference one was an
Ag/AgCl electrode; the counter was a Pt electrode. The plating of the working electrode was effected putting in
the electrochemical cell a 20 mL volume of a 1000 µgmL -1 Hg standard solution and carrying out the
electrolysis, at –950 mV against the reference electrode, for 1 min.
The determination of Cd, Cu and Pb in oily extract was executed at pH 0.5, putting in the electrochemical
cell a 3 mL volume of elute, a 17 mL volume of ultra pure H2O and a 1 mL volume of Hg (II) standard solution
as oxidant agent. The determination of Zn was executed at pH 1.8, putting in the electrochemical cell a 1 mL
volume of elute, 18.5 mL of ultra pure H2O and 0.5 mL of Hg (II) standard solution as oxidant agent. The
quantitatve analysis was carried out by the multiple standard addition method. Metals determination was
managed under analytical conditions described in table 1.
RESULTS AND DISUSSION
Method
The repeatability of the method was attested at 86.4 % for cadmium, at 94.9% for copper, at 99.0% for
lead and at 98.9% for zinc. Recoveries were carried out by spiking a sample of olive oil at different levels.
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