Chemistry Reference
In-Depth Information
Workentine et al.
(2008) used the test system discussed in Section 5.2.2 and listed
in
Table 5.15
. Linear regression analyses were conducted to determine the relation-
ships between the measured toxicity values and σ
p
: r
2
= 0.23, p = 0.032 (MIC
24
),
r
2
= 0.30, p = 0.043 (MBC
100
) and r
2
= 0.32, p = 0.113 (MBEC
100
).
Khangarot and Das (2009) did not report any QSARs for the Pearson and Mawby
softness parameter (σ
p
). However, they did use linear regression analysis to develop
correlation coefficients to describe the relationship between the toxicity of 19
unspecified cations and 2-day
Cypris subglobosa
Sowerby 1840 EC
50
values based
on immobilization. Their correlation coefficients were converted to coefficients of
determination and the statistics for their linear regression analysis were r
2
= 0.64 and
p < 0.005. Their test system is provided in Table 5.15.
Mendes et al.
(2010) developed 7 QSARs using the Pearson and Mawby softness
parameter (σ
p
) alone or combined with electronegativity, logarithm of the first
hydrolysis constant, covalent index, or atomic radius to predict EC
50
values to the
fungus
Gerronema viridilucens
for 18 cations (
Table 5.12
). Of the 7 QSARs, the
combination of the Pearson and Mawby softness parameter, electronegativity, and
the logarithm of the first hydrolysis constant had a high coefficient of determination
and the lowest AIC (Table 5.12). The test system and cations used to develop the
Mendes et al.
(2010) QSAR are listed in Table 5.15.
Table 5.19
lists the 21 QSARs that only used the Pearson and Mawby softness
parameter (σ
p
) to predict cation toxicity. Two of these QSARs are duplicates. The
Turner et al.
(1983) QSAR with r
2
= 0.360 is a duplicate of the Williams et al.
(1982)
QSAR with the same r
2
value. The Turner et al. (1985) QSAR with r
2
= 0.879 is
a duplicate of the Turner et al.
(1983) QSAR with the same r
2
value. The Jones
and Vaughn (1978) QSAR for Ag
+
, Au
+
, Cd
2+
and Hg
2+
had the highest r
2
, perhaps
because of their proximity in the periodic table. The Turner et al. (1983) QSAR for
Mn
2+
, Co
2+
, Ni
2+
, Cu
2+
, Zn
2+
, Cd
2+
, Hg
2+
and Pb
2+
had the second highest r
2
, perhaps
because Mn
2+
, Co
2+
, Ni
2+
, Cu
2+
and Zn
2+
were in row 4 of the periodic table and
Cd
2+
, Hg
2+
and Pb
2+
were in close proximity. For the Jones and Vaughn (1978) and
Turner et al. (1983) references with 4 and 3 QSARs, respectively, the r
2
decreased as
the number of divalent cations increased (
Table 5.18
)
. The Babich et al. (1986) and
Magwood and George (1996) QSARs both had high r
2
and almost identical cations.
The Babich et al.
(1986) QSAR had almost identical cations to those used for the
Turner et al.
(1983) QSAR with r
2
= 0.879 (Table 5.18). The Enache et al.
(1999)
QSAR also had a high r
2
. However, the Mendes et al.
(2010) QSAR with a high r
2
was the best for the highest number (18) of cations (Table 5.19).
5.3 LESS COMMON PHYSICOCHEMICAL PROPERTIES
USED TO PREDICT CATION TOXICITY
Table 5.20
lists the QSARs with less common physicochemical properties used to
predict cation toxicity. Only a few of the test systems for the references listed in
Table 5.20 have not been previously described. These test systems are described here.
Sauvant et al.
(1997) used the ionization potential (IP) of 16 cations and five bio-
assays (RNA synthesis rate assay, MTT reduction assay, neutral red incorporation
