3.1.4. Effect of pH
The pH is an important analytical parameter because; it has an
effect on the increase of extraction efficiency. The influence of
pH on the extraction of RB from water was studied in the pH
range of 1–12. As can be seen in Fig. 4, the highest signal intensity
of RB obtained at pH 2. Therefore, pH 2 was selected for
further studies. Moreover, to adjust pH 2, nitric acid was used.
At the higher and lower pH values RB absorbance decreases.
3.1.5. Effect of ionic strength
The addition of salt improves the extraction efficiency in many
conventional extraction processes. Because the organic acceptor/
aqueous donor phase distribution coefficient can be enhanced
by increasing the ionic strength of the aqueous
sample (Pedersen-Bjergaard and Rasmussen, 2008; Psillakis
and Kalograkis, 2003; Rasmussen and Pedersen-Bjergaard,
2004).This phenomenon helps to enhance the affinity of the
acceptor phase for the analyte molecules. Sodium chloride
(NaCl) is commonly added to analytical samples (Rasmussen
and Pedersen-Bjergaard, 2004). To investigate the effect of
ionic strength on DLLME performance, a number of experiments
were performed by adding different amount of NaCl
1–15% (w/v), while other experimental conditions were kept
constant. The results obtained showed that the salt almost
had positive effect on the extraction efficiency of the RB.
The optimal concentration of NaCl was obtained at 10%
(w/v). Thus, the work was done with the addition of NaCl with
a concentration of 10% (w/v) (see Fig. 5).
3.1.6. Study of the extraction time
In DLLME, extraction time is defined as interval time between
injection the mixture of disperser (acetone) and extraction solvent
(octanol) into the aqueous sample and starting to centrifuge.
It is noted that after formation of the cloudy solution, the
contact area between extraction solvent and aqueous phase
(sample) is infinitely large. Thereby, transition of the analytes
from aqueous phase (sample) to the extraction solvent is very
fast. Subsequently, the equilibrium state is achieved quickly so
the extraction time is very short. This is an advantage of the
DLLME technique, i.e., low extraction time. In this method,
the time-consuming step is the centrifuging of sample solution
in extraction procedure. The effect of extraction time was
examined in the range of 1–25 min while the other experimental
conditions remained constant. The obtained results are
3.1.4. Effect of pH
The pH is an important analytical parameter because; it has an
effect on the increase of extraction efficiency. The influence of
pH on the extraction of RB from water was studied in the pH
range of 1–12. As can be seen in Fig. 4, the highest signal intensity
of RB obtained at pH 2. Therefore, pH 2 was selected for
further studies. Moreover, to adjust pH 2, nitric acid was used.
At the higher and lower pH values RB absorbance decreases.
3.1.5. Effect of ionic strength
The addition of salt improves the extraction efficiency in many
conventional extraction processes. Because the organic acceptor/
aqueous donor phase distribution coefficient can be enhanced
by increasing the ionic strength of the aqueous
sample (Pedersen-Bjergaard and Rasmussen, 2008; Psillakis
and Kalograkis, 2003; Rasmussen and Pedersen-Bjergaard,
2004).This phenomenon helps to enhance the affinity of the
acceptor phase for the analyte molecules. Sodium chloride
(NaCl) is commonly added to analytical samples (Rasmussen
and Pedersen-Bjergaard, 2004). To investigate the effect of
ionic strength on DLLME performance, a number of experiments
were performed by adding different amount of NaCl
1–15% (w/v), while other experimental conditions were kept
constant. The results obtained showed that the salt almost
had positive effect on the extraction efficiency of the RB.
The optimal concentration of NaCl was obtained at 10%
(w/v). Thus, the work was done with the addition of NaCl with
a concentration of 10% (w/v) (see Fig. 5).
3.1.6. Study of the extraction time
In DLLME, extraction time is defined as interval time between
injection the mixture of disperser (acetone) and extraction solvent
(octanol) into the aqueous sample and starting to centrifuge.
It is noted that after formation of the cloudy solution, the
contact area between extraction solvent and aqueous phase
(sample) is infinitely large. Thereby, transition of the analytes
from aqueous phase (sample) to the extraction solvent is very
fast. Subsequently, the equilibrium state is achieved quickly so
the extraction time is very short. This is an advantage of the
DLLME technique, i.e., low extraction time. In this method,
the time-consuming step is the centrifuging of sample solution
in extraction procedure. The effect of extraction time was
examined in the range of 1–25 min while the other experimental
conditions remained constant. The obtained results are
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