© Benaki Phytopathological Institute
Bempelou
et al.
62
at nine levels of concentration, i.e. 0.05, 0.1,
0.2, 0.5, 1, 2, 5, 10 and 20μg/mL, and linear-
ity parameters were found acceptable, with
correlation coefficients (r) being higher than
0.998. The contribution of the uncertainty of
the calibration line on the total uncertainty
of the method was calculated at the middle
concentration (0.5μg/mL) of the calibration
curve and was estimated to be 31.4%, based
on the equation
In the case of inorganic bromide, as al-
ready mentioned, the calibration solutions
followed the complete method procedure
using five final solutions in ethyl acetate
equivalent to 5, 25, 50, 100 and 150μg Br.
Linearity parameters were found also ac-
ceptable, with correlation coefficients (r) to
be higher than 0.99. The contribution of the
uncertainty of the calibration line on the to-
tal uncertainty of the method was calculat-
ed at the middle concentration (10μg/mL)
and was estimated to be 26.3%, based on
the equation mentioned above.
The suitability of the present analytical
methods for the determination of dithiocar-
bamate fungicides and inorganic bromide
in plant products was further proved by the
successful participation of our laboratory in
two proficiency tests EUPT-SRM 5 and EUPT-
SRM 6 (European Proficiency Tests for Single
Residue Methods 5 and 6) organized by the
European Reference Laboratories. The test
materials of these proficiency tests were ap-
ple and rice, respectively. The method of di-
thiocarbamates was evaluated with the ac-
ceptable z scores of 1.42 for apples and 0.69
for rice, while the one of inorganic bromide
participated only in the proficiency test of
rice and was evaluated with the very good
z score of -0.2.
The described methods were applied for
the analysis of domestic and imported sam-
ples, 150 for dithiocarbamates and 45 for in-
organic bromide, 12%of which gave positive
results for CS
2
but not above the MRLs set by
legislation. In the case of inorganic bromide,
92% of the tested samples gave positive re-
sults, since bromide is a natural component
of plant tissues. There were, however, only
two samples of rice in which very high con-
S
u
= S
y/x
b
Table 1.
Mean recoveries (R, %), number of replicates (n), relative standard deviations (RSD,
%) for the determination of CS
2
in plant products at 2 fortification levels.
Matrix
1
st
level (n=5)
2
nd
level (n=5)
C (mg/kg)
R (%)
RSD (%)
MRL (mg/kg)
R (%)
RSD (%)
Apples
0.1
101
11.6
5
90
9.6
Leek
0.1
83
6.9
3
84
4.0
Potato
0.1
110
9.1
1
104
5.8
Strawberry
1.0
112
5.3
10
104
6.4
Wheat
0.2
89
15.5
1
71
6.7
Tomato
0.3
93
10.1
3
84
5.6
Table 2.
Mean recoveries (R, %), number of replicates (n), relative standard deviations (RSD,
%) for the determination of inorganic bromide in plant products in 3 fortification levels.
Matrix
1
st
level (n=5)
2
nd
level (n=5)
3
rd
level (n=5)
C (mg/kg) R (%) RSD (%) MRL (mg/kg)
R(%) RSD (%) C (mg/kg) R (%) RSD (%)
Tomato
10
89
9.3
50
94
6.2
Lettuce
10
95
9.0
50
89
4.7
0.5
82
6.7
Rice
10
90
18.5
50
80
4.6
1...,23,24,25,26,27,28,29,30,31,32 34,35,36,37,38,39,40,41,42