Brazilian Journal of Analytical Chemistry - BRJAC - Brazilian Journal ...

In the study of accuracy, recovery tests were performed
by adding pesticides to mashed potato samples
at concentrations nearly 2, 5 and 20 times (15.0,
30.0 and 150.0 µg L -1 ) the encountered quantification
limit (QL). The method was efficient with recoveries
of 93.8% for chlorpyrifos, 94.4% for λ-cyhalothrin,
82.1% for cypermethrin and 97.9% for deltamethrin.
The method presented good accuracy since all obtained
recovery percentages at the three levels did not differ
significantly among themselves at the level of 95%
probability in accordance with the t-test, and the coefficients
of variation (CV) were less than 5%, independent
of the concentration.
Considering the MRL of the pesticides of interest in
potatoes established by ANVISA (1, 0.05, 0.05 and 0.01
µg g -1 for chlorpyrifos, λ -cyhalothrin, cypermethrin and
deltamethrin, respectively) and recovery percentages
obtained at the level of fortification of 0.05 µg g -1 (15.0
µg L -1 in the extract), it was concluded that all pesticides
were efficiently extracted from the matrix.Despite the
good efficiency of the extraction of deltamethrin, the
LQ of this compound was two times greater than the
MRL established by ANVISA.
The results obtained by employing the SLE-LTP method
in fortified potato samples were compared to the
results obtained by the method utilized by IMA (Instituto
Mineiro de Agropecuária) for extraction of the
pesticides chlorpyrifos, λ-cyhalothrin, cypermethrin and
deltamethrin in food products (Table III).
taBlE iii. rECovEry PErCEntagEs (%r), standard dEviation
EstimatE a n d C o E f f iC iE n t o f variation, Cv(%), o f thE PEstiCidEs
ChlorPyrifos, λ-Cyhalothrin, CyPErmEthrin a n d dEltamEthrin in
fortifiEd Potato samPlEs, E m P l o y i n g thE slE-ltP m E t h o d a n d thE
m E t h o d utilizEd By ima.
ChlorPyrifos λ- Cy h a l o t h r i n CyPErmEthrin dE l t a m E t h r i n
%R CV(%) %R CV(%) %R CV(%) %R CV(%)
SLE-LTP 93.8 2.4 94.4 2.4 82.1 a 2.6 97.9 2.8
IMA
Method 98.5 4.4 87.0 5.3 81.9a 4.5 80.0 3.2
(a) results statistically similar at a 95% probability level according to
the t-test.
Analyzing the degree of proximity between the results
obtained by the two methods (Table III), it was observed
that λ-cyhalothrin and deltamethrin were best
extracted by the SLE-LTP technique, while the recovery
percentages obtained for cypermethrin were statistically
the same. However, the two methods did not show
significant dispersion between the two sets of results.
The multi-residue method employed by the laboratories
of IMA basically consist of a solid-liquid extraction
using acetone, dichloromethane and hexane as
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Dardengo et al.
solvent extractors. This method requires a large volume
of organic solvent (100.0 mL) and various sample
preparation steps, characteristics that increase the cost
of analysis and decrease laboratory productivity. The
use of dichloromethane, a solvent incompatible with
the electron capture detector, requires an evaporation
stage and changing of solvent. Dichloromethane also
presents high toxicity, inflammability and environmental
risks. Acetonitrile employed in the SLE-LTP is toxic as
well, but according to Maštovská and Lehotay [26], the
negative impacts caused by this solvent to human health
and to the environment are lower than those caused by
chlorinated solvents such as dichloromethane. According
to the US Environmental Protection Agency (EPA),
acetonitrile is not classified as carcinogenic to human
beings and is less persistent in the environment. Its low
volatility also reduces exposure of analysts to vapor during
sample preparation.
Advantages of the IMA method include its use of an
extract concentration factor of 10, which may contribute
to better detectability and the fact that it can be
used with different matrices (carrots, strawberries, potatoes,
etc.) for analysis of a wide range of pesticides of
different chemical classes.
In contrast, the SLE-LTP technique presents a lower
consumption of solvent (10.0 mL), and does not require
an evaporation step and solvent change, reducing
the risks of contamination and loss of analytes of
interest. This provides more precise results which can
be observed (Table III) from the coefficients of variation
which are slightly lower when the SLE-LTP methodology
is employed.
3.4 applIcatIon o f t h e optImIzed sle-ltp m e t h o d o l o g y
to potato samples harvested In t h e souther n r e g Io n
o f mIn a s ge r a Is state, br a z Il.
Pyrethroid residues were not detected in any of the
analyzed samples.
In three samples from a crop that received the recommended
doses of commercial insecticides containing
chlorpyrifos and cypermethrin, chlorpyrifos residues (50
µg kg -1 , 230 µg kg -1 and 6.5 µg kg -1 ) were detected at
levels below the MRL established for potato by Brazilian
Legislation (1000 µg kg -1 ).These results were confirmed
by GC-MS for two samples. In addition to retention
time, the ion m/z values of 97, 197, 314 and 349 were
also used for identification of chlorpyrifos.
In samples of potatoes purchased from local retail
stores in Viçosa, MG, Brazil clorpyrifos residues were
detected at levels below the QL.
Samples of potatoes in which quantifiable pesticide
residues were detected were peeled and the pulp and
peel analyzed separately. Residues of chlorpyrifos were
not detected in the pulp. However, in the peel, chlorpyrifos
concentrations higher than 970 µg kg -1 were
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