Background: Tricyclic Antidepressants (TCAs) can be used for the treatment of depression,
psychiatric disorders and insomnia. They are used extensively in all the countries especially in the developed
countries and therefore, can enter the aquatic environment mainly through the human excretion.
These drugs cannot be completely removed or degraded during the sewage treatment process and their
concentrations in the aquatic environment are relatively low; therefore, the development of sensitive
analytical methods for determination of their concentrations is very important. In biofluids, the measurements
of TCAs are very important to ensure the quality of the preparation and to obtain the optimal
therapeutic concentrations, while minimizing the risk of inappropriate dose or overdose. So, the methods
for determining these drugs concentrations in human samples for forensic purposes are required.
Methods: The aqueous sample solution was transferred into a glass centrifuge tube with flat bottom and
1-octanol as extraction solvent was withdrawn into an HPLC microsyringe and then, rapidly injected
into the tube via syringe needle in order to form a mixture of the aqueous sample solution and the organic
solvent. Then, this mixture was repeatedly aspirated from the tube and infused into it several
times. This caused the solution to become turbid. This operation resulted in the extraction of the target
analyte from the sample solution into the fine droplets of 1-octanol. After then, the mixture was centrifuged
to gather the drops of low density extractant above the sample solution as a thin film. For sampling,
by inserting a PTFE coated stirring bar at the flat bottom of the tube and turning on the stirrer, the
thin film of the organic extraction solvent was converted into a conical vortex with enough volume for
easy collection by the needle syringe.
Results: Several important factors affecting the microextraction efficiency, such as the type and volume
of the extraction solvent (180 µL of 1-octanol), the volume of the aqueous sample solution (7 mL), the
number of air injected (7 times), pH of the sample solution (pH 10) and the ionic strength (no salt addition)
were investigated. Under the optimal extraction conditions, the method exhibited low limit of detection
(0.52 ng mL-1) and good linearity (2-1000 ng mL-1) with coefficient of determination (R2) of
0.9979. The relative standard deviation was 4.5 % and the enrichment factor was 32. Finally, the applicability
of the proposed method was evaluated by extraction of amitriptyline in the biological and environmental
water samples and the calculated relative recoveries were more than 85%.
Conclusion: In this research work, a novel microextraction method based on DLLME has been presented
for the extraction, preconcentration and determination of amitriptyline in various real samples
without using disperser solvents. Also, the developed method was appropriate for the use of low density
extraction solvents without any special device and complicated operation which permitted the use of a
wider range of the organic extraction solvents. On the other hand, by using an innovative simple
method, the internal volume of the quartz UV-Vis microcell decreased and consequently, the volume of
the organic extraction solvent reduced as much as possible which led to the proximity to the aspects of
green chemistry. In addition, under the optimal extraction condition, the method offers good LOD, as
well as good linearity range and repeatability along with acceptable relative recoveries.