4.Optimization of extraction temperature and time
Reported cloud point temperatures for TritonX-114 are within
the range of 15e20 C [19]. It refers to the temperature at which the
surfactant coacervation results notorious in the extraction system,
because of its turbid aspect. As it is well known, extraction temperatures
above the cloud point, and/or the extended extraction
time (>2 min), diminishes the water content of the resulting surfactant
reach phase, and thus, its final volume [25]. This argument
is based on the fact that as the extraction temperature increases,
the hydrogen bonds are disrupted leading, thus, to dehydration of
micelles [25]. On the other hand, it is important to take into account
that the use of excessive high extraction temperature can reduce
the CPE efficiency, because of the thermal stability of surfactant
aggregates [30] as well as the analytes lability. Therefore, it was of
interest to study the effect of the extraction temperature on the
extraction system performance, as well as on the analytes analytical
response along with the extraction time within the range 45e75 C
and 10e30 min, respectively. The extraction temperature assays
were carried out considering a 20 min extraction time; while the
time assays, were carried out at the optimum temperature resulting
from the former. As the temperature increased from 45 to 65 C a
better surfactant-rich phase separation as well as an increased
response of the analytes was observed. The results showed no
significant change neither on the CPE performance nor on the
analytical response of the studied ARV at extraction temperatures
above 65 C. Therefore, 65 Cwere chosen for further assays. For the
extraction time, it was observed that by increasing it, the relative
response is subsequently increased, reaching the maximum
analytical responses of the studied ARV at 20 min; after which, and
remained invariant. Thus, in the following experiments, an
extraction time of 20 min was selected for the extraction.