Toxicity assessment of phosphonium based ionic liquids towards female guppy fish

Article abstract of DOI:10.14233/ajchem.2014.16276

In this study, two phosphonium based ionic liquids (butyl triphenyl phosphonium chloride and hexyl triphenyl phosphonium bromide) have been synthesized using quarternization process. The toxicities of these ionic liquids are unknown and may be harmful to humans and the environment. Therefore, the toxicity assessment of these ionic liquids was carried out according to the Organization for Economic Cooperation and Development (OECD) guideline 203 using female guppy fish (Poecilia reticulata). The median lethal concentrations (LC₅₀) have been estimated for butyl triphenyl phosphonium chloride and for hexyl triphenyl phosphonium bromide to be 73.35 mg/L and 61.36 mg/L respectively. Both LC₅₀ obtained can be identified as slightly toxic ionic liquids based on Acute Toxicity Rating Scale by by the United States Fish and Wildlife Service (USFWS). The findings from this study can be used for better design of phosphonium-based ionic liquids with consideration of their aquatic toxicities.

Full text of DOI:10.14233/ajchem.2014.16276

Asian Journal of Chemistry; Vol. 26, No. 10 (2014), 2997-3000
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16276
Toxicity Assessment of Phosphonium Based Ionic Liquids Towards Female Guppy Fish
1
,*
2
3
MOHANAD EL-HARBAWI , YASMIN SYAZWANI BT. YUSRI and M. ISMAIL HOSSAIN
1
2
3
Department of Chemical Engineering, King Saud University, Riyadh 11421, Saudi Arabia
Faculty of Chemical Engineering, Universiti Teknologi MARA, 40200 Shah Alam, Selangor, Malaysia
Department of Chemistry, Chittagong University, Chittagong-4331, Bangladesh
*
Corresponding author: Tel: +966 556257947; E-mail: melharbawi@ksu.edu.sa
Received: 3 September 2013; Accepted: 28 December 2013;
Published online: 10 May 2014;
AJC-15166
In this study, two phosphonium based ionic liquids (butyl triphenyl phosphonium chloride and hexyl triphenyl phosphonium bromide)
have been synthesized using quarternization process. The toxicities of these ionic liquids are unknown and may be harmful to humans and
the environment. Therefore, the toxicity assessment of these ionic liquids was carried out according to the Organization for Economic
Cooperation and Development (OECD) guideline 203 using female guppy fish (Poecilia reticulata). The median lethal concentrations
(
LC50) have been estimated for butyl triphenyl phosphonium chloride and for hexyl triphenyl phosphonium bromide to be 73.35 mg/L and
1.36 mg/L respectively. Both LC50 obtained can be identified as slightly toxic ionic liquids based on Acute Toxicity Rating Scale by by
6
the United States Fish and Wildlife Service (USFWS). The findings from this study can be used for better design of phosphonium-based
ionic liquids with consideration of their aquatic toxicities.
Keywords: Ionic liquids, Fish, Toxicity, Lethal concentration.
ether etc.) in industrial applications causing a major concern
in the current chemical processing industry.Although intensive
information and data regarding ionic liquids' physical and
thermodynamic properties have been reported and continu-
ously published, only limited data with regard to the toxicity
INTRODUCTION
1
The world of ionic liquids (ILs) started in 1914 byWalden
3 3
who synthesized ethylammonium nitrate [EtNH ][NO ]. Later,
after several years, ionic liquids began to gain more of the
attention of scientists when first room temperature ionic liquid
2
with a 1-alkyl-3-methylimidazolium cation was reported . Ionic
5
-12
and ecotoxicity were reported . The toxic effects of many
solvents combined with serious environmental issues, such as
atmospheric emissions and contamination of aqueous effluents
are making them harmful to use. Thus, many researchers have
emphasized on the improvement of green engineering which
represents research aimed at finding environmentally benign
alternatives to harmful chemicals.Among the neoteric solvents
applicable in green technologies, ionic liquids have garnered
increasing attention over the others due to their numerous appli-
cations in recent years. In general, the toxicity of chemicals
can be measured using (a) mammalian acute toxicity test (b)
bacteria acute toxicity test (c) fish acute toxicity test and (d)
liquids are composed of ions only and they are fluid below
100 °C due to asymmetry of one of the ions. They are thermally
stable with liquid range up to 300 °C compared to 100 °C for
water and show very low vapour pressure, which makes them
of great interest due to these properties. Ionic liquids typically
consist of bulky organic cations, such as imidazolium, pyridi-
nium, ammonium, phosphonium, etc. paired with various anions,
–
–
3,4
4
such as hexaflurophosphate (PF ), bromide (Br ), etc. . They
are currently considered as a remarkable class of solvents due
to their large liquidous range and non-volatile behaviour and
can be used for a broad range of industrial applications. The
research on this area is rapidly increasing due to their exciting
applications and wide usages. The reason for the increasing
interest is clearly due to the realization that these materials
have a great utility as solvents for reactions and material proce-
ssing, media for extraction and working fluids for mechanical
applications.Volatile organic compounds (VOCs) were previously
used as solvents (such as, methanol, ethanol, benzene, toluene,
13
biological dissociation test . The aquatic toxicity assessment
is the study of the effects of the chemicals and other anthropo-
genic and natural materials and activities on aquatic organisms
at various levels of organization and ecosystems. The effects
can cause both positive and negative alteration from previously
existing circumstances, but aquatic toxicology focuses primarily
on the deviations that are considered to be adverse in nature
and on recovery processes in biota that may occur when the

2
998 El-Harbawi et al.
Asian J. Chem.
2
5,26
exposure diminishes. Adverse effects at the organismal level
include both the short-term (acute) and long-term (chronic)
lethality (expressed as mortality or survival) and sub-lethal
effects such as changes in behaviour, growth, development,
reproduction, detoxification activities and tissue structure.
Adverse effects at the sub-organismal level include induction
or inhibition of enzymes and/or phenotypes, as well as changes
in the number, relative abundance and physiological condition
established methods . To an equivalent amountof triphenyl-
phosphine (2 mL, 5.79 mmol) contained in a round-bottomed
flash equipped with a reflux condenser, a magnetic stirrer and
an inlet and outlet of nitogen gas, the appropriate alkylating
reagent (6.00 mmol, in excess) was added drop-wise via
syringe and the mixture was stirred at a temperature rising
from 30 to 200 °C.The reaction time normally varies from 10
to 29 h.After the addition was complete, the mixturewas stirred
for 2 to 3 h at the highest temperature reached (200 °C). The
progress of the reaction was monitored by NMR spectroscopy,
and thus the solid product obtained was dried at high vacuum
overnight. The general structures of these ionic liquids' are
shown in Fig. 1.
14
of species typically found in a given community type . There are
several test species that are recommended by the Organization
for Economic Cooperation and Development (OECD)
guidelines, which are rainbow trout (Oncorhynchus mykiss),
fathead minnow (Pimephales promelas), bluegill (Lepomis
macrochirus), zebrafish (Danio rerio), medaka (Oryzias latipes),
guppy (Poecilia reticulata) and common carp (Cyprinus carpio).
A number of acute toxicity studies have been performed using
+
P
15
+
P
-
-
a variety of fish. For instance, McKim used Chinook salmon
Cl
Br
(Oncorhynchus tshawytscha) for chronic toxicity evaluation.
Baser et al. investigated the acute toxicity of permethrin (a
synthetic pyrethroid pesticide) on guppy fish (Poecilia
1
6
8
reticulata). Pretti et al. assessed the acute toxicity of several
Butyltriphenylphosphonium chloride Hexyltriphenylphosphonium bromide
Fig. 1. Structures of ionic liquids used in this study
17
ionic liquids' towards zebrafish (Danio rerio). Sarikaya et al.
used guppy fish to estimate the toxicity of Fenitrothion (O,O-
dimethyl-O-(3-methyl-4-nitrophenyl) phosphorothioate).
Fish acute toxicity test: The species used for this study is
female guppy fish (Poecilia reticulata). The fish were purchased
from a fish tackling shop in Perak, Malaysia, and brought to
the laboratory within 15 min of purchase in plastic bags
containing sufficient amounts of water for sustainability. Upon
arrival at the test site, the fish were placed in plastic tanks for
acclimation. Prior to the toxicity test, the fish were held in the
laboratory for 12 days. The fish were fed twice daily, once in
the morning and once in the evening. The fish were kept under
normal laboratory illumination with a daily photoperiod of
18
Wang et al. estimated the toxicity of 1-methyl-3-octylimida-
zolium bromide ([C mim][Br]) using goldfish (Carassius
auratus). Dumitrescu et al. evaluated the acute toxicity of
8
19
2
0
tetrabuthylammonium bromide using zebrafish. Li et al.
employed goldfish to evaluate the toxicity of 1-methyl-3-
octylimidazolium bromide ([C mim][Br]). Most researchers
in recent years have carried out acute toxicity tests for at least
8 h and usually 96 h. For more information regarding toxicity
8
4
assessment using guppy fish (Poecilia reticulata), readers can
refer to PAN (Pesticide Action Network) Pesticides Database
1
2-16 h. The temperature of the water was between 23 ± 2 °C.
The dissolved oxygen and pH of the water were 5-7 ppm and
, respectively. The fish were observed carefully every day
(
http://www.pesticideinfo.org) and ECOTOX database (http:/
cfpub.epa.gov/ecotox/). The recent searching (in 2012) with
Guppy (Poecilia reticulata) toxicity studies" gave around
104 individual studies on this species with different chemicals,
which is even greater than with goldfish, Carassius auratus
7
/
for signs of disease, stress, physical damage and mortality. Dead
and abnormal specimens were removed immediately upon
observation. After the adaptation period was completed, a
group of 10 healthy fishes were selected randomly and placed
into 6.5 L plastic tanks provided with electric air pumps.
Healthy fish can be recognized by their normal swimming
style. Fish swimming abnormally should not be selected as
they may have a weak resistance to the chemicals used in
testing. Initially the experiments were conducted using tap
water. Unfortunately, the results were rejected due to an abnormal
death rate of the fish. Therefore, lake water was then used to
avoid the chlorine contamination of tap water. Each tank was
equipped with 5 L of lake water. No food was provided for the
fish during the test. The weight of each fish is approximately
"
4
(
3290). Other studies can be found with zebra fish, Danio rerio
4658), bluegill, Lepomis macrochirus (9677), rainbow trout,
(
Oncorhynchus mykiss (26662) and fathead minnow, pimephales
promelas (15128). For more detailed information on the acute
toxicity tests of different fish species, readers are directed to
the summary tables provided by the U.S. fish and wildlife
21,22
service reports , the handbook of acute toxicity of chemicals
23
16
to fish and aquatic invertebrates and work of Baser et al. .
In this study, the acute fish toxicity study was conducted
24
according to the prescribed guideline OECD 203 elaboration
done one time before using fresh-water Guppy fish (Poecillia
reticulata) to estimate the toxicity of two phosphonium ionic
liquids. To our best of knowledge there is no published literature
regarding the toxicity (LC50) of these ionic liquids.
0
.5 g. The acute fish toxicity test was performed according to
24
the OECD standard methods . Each ionic liquid was tested
for four concentrations. Different concentrations were added
to each testing tank. Behaviors of the fish were monitored
closely and dead fish were removed immediately. The number
of dead fish for each concentration was recorded after 24, 48,
72 and 96 h. The median lethal concentration (LC50) that is
the ionic liquids' concentration in water which kills 50 % of
the test batch of fish within a continuous period of exposure
EXPERIMENTAL
Chemicals used in this study were obtained from commer-
cial sources and had been used without drying and further
purification. All ionic liquids' were synthesized according to

Vol. 26, No. 10 (2014)
Toxicity Assessment of Phosphonium Based Ionic Liquids Towards Female Guppy Fish 2999
of 24, 48, 72 and 96 h were calculated. The results from the
experiment were compared with acute toxicity rating scale
provided by U.S. Fish and Wildlife Service (USFWS) (Table-1).
90
80
70
6
0
TABLE-1
ACUTE TOXICITY RATING SCALE BY FISH
AND WILDLIFE SERVICE (FWS)
50
40
30
Relative toxicity
Super toxic
Aquatic LC (mg/L)
50
0.01-0.1
0.1-1
20
Highly toxic
10
Moderately toxic
Slightly toxic
1-10
0
10-100
100-1000
>1000
1
.3
1.5
1.7
1.9
2.1
Practically non-toxic
Relatively harmless
log concentration (mg/L)
Fig. 2. log10 concentration vs. percent of mortality for butyl triphenyl
phosphonium chloride
RESULTS AND DISCUSSION
The screening tests for the two ionic liquids were con-
ducted with the concentration of 100 mg/L as limit test, which
showed the range of toxicity below 100 mg/L and it lies
between 50 to 100 mg/L. The observations of the fish mortality
for butyl triphenyl phosphonium chloride and hexyl triphenyl
phosphonium bromide are presented in Tables 2 and 3. It can
be clearly seen that at higher concentrations, the number of
dead fish increased. Numbers of dead fish in the time period
prescribed by the test were used to determine the mortality
per cent and median lethal concentration (LC50). The cumu-
lative percentage mortality for 96 h exposure time is plotted
against a logarithm concentration (Figs. 2 and 3).
90
80
70
60
50
40
30
20
10
0
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
Data presented in Tables 4 and 5 were used to determine
log concentration (mg/L)
27
LC50 values employing probit analysis . The best fit dose-
response lines for butyl triphenyl phosphonium chloride and
hexyl triphenyl phosphonium bromide were plotted in Figs. 4
and 5, respectively. Transformation of the toxicity curve to a
Fig. 3. log10 concentration vs. percent of mortality for hexyl triphenyl
phosphonium bromide
straight line indicates that the lethal threshold concentration
28
is estimated correctly. This fact was confirmed by Burdick .
Probit equations were derived from the experimental data
presented in Tables 4 and 5 for both ionic liquids'; which are
Y = 9.95x-13.56 andY = 3.63x-1.49, respectively. The correlation
TABLE-2
MORTALITIES OF ACUTE TOXICITY TEST FOR BUTYL
TRIPHENYL PHOSPHONIUM CHLORIDE
Concentration
2
24 h
48 h 72 h 96 h
Total fish died
coefficients, R were obtained 94 and 99 %, respectively. This
(mg/L)
is confirming the accuracy of the results obtained from the
experiment. Probit equations obtained from this work can be
used to examine the toxicity of any ionic liquids' from the
same family without the need for experimental work. It should
be noted that these two equations are only valid to estimate the
LC50 for the same ionic liquids and aquatic organism (Guppy fish).
Results presented in Figs. 2 and 3 or in Figs. 4 and 5 were
used to obtain the LC50 values. These values were obtained to
be 67.5 mg/L for butyl triphenyl phosphonium chloride and
2
5
7
5.5
2.5
7.5
0
0
0
1
0
1
2
2
0
1
2
2
0
1
2
3
0
3
6
8
1
00
TABLE-3
MORTALITIES OF ACUTE TOXICITY TEST FOR HEXYL
TRIPHENYL PHOSPHONIUM BROMIDE
Concentration
2
4 h
48 h 72 h 96 h
Total fish died
(
7.5
0.0
8.0
00
mg/L)
56.3 mg/L for hexyl triphenyl phosphonium bromide respectively.
2
5
7
1
0
1
2
2
0
1
2
2
0
2
2
2
1
2
2
2
1
4
8
8
According to the acute toxicity rating scale provided by
the U.S. Fish and Wildlife Service (USFWS), these values lie
within the range of slightly toxic.
TABLE-4
log DOSE AND PERCENTAGE OF MORTALITY FOR BUTYL TRIPHENYL PHOSPHONIUM CHLORIDE
Dose (mg/L)
log dose (mg/L)
1.407
Total fish
Total mortality
% of mortality
Probit variable
25.5
52.5
77.5
10
10
10
10
0
3
6
8
0
0
1.720
30
60
80
4.48
5.25
5.84
1.889
100
2.000

3
000 El-Harbawi et al.
Asian J. Chem.
TABLE-5
log DOSE AND PERCENTAGE OF MORTALITY FOR HEXYL TRIPHENYL PHOSPHONIUM BROMIDE
Dose (mg/L)
log dose (mg/L)
1.439
Total Fish
Total mortality
% of mortality
Probits variable
27.5
50.0
78.0
10
10
10
10
1
4
8
8
10
40
80
80
3.72
4.75
5.25
5.84
1.699
1.892
100
2.000
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Conclusion
Fish acute toxicity method was used to evaluate the LC50
of two phosphonium based ionic liquids. The acute fish toxicity
test was performed using Guppy fish (Poecilia reticulata)
according to the OECD 203 standard methods. Results
obtained from this work indicate that the butyl triphenyl phos-
phonium chloride and hexyl triphenyl phosphonium bromide
are slightly toxic. The result from this study can be beneficial
to industrial people who use phosphonium based ionic liquids
in their industrial processes.
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