Electronic Supplementary Material (ESM) for
Supramolecular–based dispersive liquid–liquid microextraction: A novel
sample preparation technique for determination of inorganic species
Sanaz Jafarvand, Farzaneh Shemirani
Effect of the volume of disperser solvent
Influence of the volume of THF (disperser solvent) on cobalt absorbance was also examined. It is
noted that by using different volumes of THF and a constant amount of microextraction solvent
the obtained volume of standing phase was not the same. In order to acquire the same volume of
standing phase (60+2 µL), the volume of disperser solvent and the amount microextraction
solvent were changed simultaneously. To obtain the optimized volume of THF, various
experiments were performed by using different volumes of THF (0.50, 1.00, 1.50, and 2.00 mL)
containing 41, 29.5, 21.15, and 16.7 mg of decanoic acid, respectively, while the volume of the
standing phase was constant (60+2 µL). Below this volume (0.50 mL) only a fraction of the
decanoic acid is incorporated in coacervation process and as a result the extraction efficiency and
absorbance signals are low. The decrease of signal at higher concentrations of THF is probably
due to the dissolution of a portion of the coacervate in THF–water bulk solution. Fig. S1 shows
the effect of disperser solvent volume on the absorbance of cobalt.
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Fig. S1 Effect of the volume of THF (disperser solvent) on the absorbance of cobalt obtained from SM–
DLLME. Extraction conditions, volume of water sample, 5.00 mL; pH 1; concentration cobalt, 100 µgL–1,
amount of decanoic acid (microextraction solvent), 41 mg
Chelating agent concentration
The influence of the quantity of reagent PAN in preconcentration of cobalt was evaluated,
varying the concentration of the solution of this reagent. PAN solutions at different
concentrations in ethanol were prepared. Each of these solutions was mixed with aqueous
solution containing cobalt and after complex formation; the solution of decanoic acid in THF
was injected rapidly into the sample solution. The result obtained for each solution is shown in
Fig. S2. We investigated PAN concentration in the range of 0.3×10−5 to 4.0×10−5 mol L−1.
Maximum absorbance was obtained at a concentration of 3.0×10−5 mol L−1 of the ligand and
after that, absorbance approximately stays constant. Two solutions of PAN (3.0×10−5 mol L−1)
were prepared with different solvents, ethanol and THF. These solutions were submitted to
preconcentration procedure. The results were similar for both solvents. Then, ethanol was used to
prepare a 3.0×10−5 mol L−1 PAN solution, due to its more environment friendlier property.
2
Fig. S2 Effect of PAN amount on cobalt absorbance obtained by SM–DLLME. Extraction conditions are
the same as Fig. S1
Effect of ionic strength
For investigating the influence of ionic strength on the microextraction efficiency of SM–
DLLME, various experiments were performed by adding different amount of KNO3 (0–20%
w/v) into a standard solution (100 µg L–1 of cobalt) with other experimental conditions were kept
constant. Results show that the absorbance decreased by adding KNO3 concentration in the
studied range. It is noted that by increasing KNO3 concentration, the volume of standing phase
increases due to decreasing microextraction solvent solubility in the aqueous phase in the
presence of salt (Fig. S3).
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Fig. S3 Effect of ionic strength on the absorbance of cobalt obtained from SM–DLLME. Extraction
conditions, as with Fig. S1
Determination of cobalt in real water samples
The presented method was applied to the determination of cobalt in tap water, well water,
mineral water and waste water. Reliability was checked by spiking the sample and the results
obtained were in good agreement with those obtained using reference method (ASTM D 3558–
90). For this purpose samples were passed through the filter. After centrifuging the samples, they
were diluted and acidified with HCl to pH 1 and 5.00 mL of samples were pre–concentrated
using the previously described SM–DLLME technique. The results along with the recovery for
the spiked sample with 100 µg L–1 and 30 µg L–1 of cobalt are given in Table S1. As could be
seen, the recoveries of the spiked samples are satisfactory and the results obtained (Table S1)
indicate that the relative recoveries are in the range of 94.6–107%. Statistical comparison of the
results by the Student’s t–test and the variance–ratio F–test at the 95% confidence level revealed
there was no significant difference between the accuracy and precision of the two methods. Thus,
this method is reliable for determination of cobalt in natural water samples.
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Table S1 Determination of cobalt in real water samples and relative recovery of spiked cobalt
Sample
Concentration of Co
a
Mean ± SD /
Added Co /
-1
µg L
-1
Found Co
Mean ± SD /
-1
µg L
Relative
a
recovery /
µg L
%
Added Co /
-1
µg L
Found Co
Relative
a
Mean ± SD /
-1
recovery /
µg L
%
Tap water b
n.d f
30
29.7 ± 2
99
100
100 ± 3
100
Well water c
n.d f
30
32.1 ± 2
107
100
101 ± 3
101
Mineral water d
n.d f
30
28.4 ± 2
94.6
100
98.6 ± 3
98.6
Waste water e
32 ± 3
30
60 ± 3
96.7
100
130 ± 4
98.5
a
standard deviation (n = 3).
b
From drinking water system of Tehran, Iran.
c
From Tehran.
d
Damavand mineral water.
e
From Zanjan Industrial Group.
f
Not detected.
5