Polyoxomolybdate368 /polyaniline nanocomposite as a novel fiber for solid-phase microextraction of antidepressant drugs in biological samples.

A novel solid-phase microextraction fiber was synthesized by coating a stainless steel wire with polyoxomolybdate368 /polyaniline as a sorbent aimed at extraction of amitriptyline, nortriptyline, and doxepin as antidepressant drugs from urine and blood samples. The polyoxomolybdate368 /polyaniline composite coating was applied using electropolymerization process under constant potential. This composition leads to enhanced extraction efficiency of the fiber. Scanning electron microscopy images show that huge three-dimensional structures of polyoxomolybdate368 in composite induced more non-smooth and porous fiber. In order to optimize of the extraction process, a series of variables including concentration of the composite materials, coating thickness, pH, extraction time, salt addition, and stirring rate was investigated and optimum conditions were determined. Analysis of surface morphology and chemical composition was performed. High-performance liquid chromatography was used for separation and evaluation of mentioned antidepressant drugs from the matrixes. The experiments indicated a detection limits of <0.2 ng/L and a linear dynamic range of 0.3-100 ng/L (R2  > 0.994). The relative recovery values were found to be in the range of 92-98%. It was concluded that the purposed fiber is highly efficient in analyzing traces of antidepressant drugs in urine and blood.

High-throughput protein precipitation method with 96-well plate for determination of doxepin and nordoxepin in human plasma using LC-MS/MS.

The aim of this study was to establish a high-throughput and sensitive LC-MS/MS method for the determination of doxepin and its major active metabolite nordoxepin in human plasma. It has been designed for bioequivalence study for formulations containing 25 mg of doxepin. Doxepin and nordoxepin were extracted from human plasma samples by protein precipitation with acetonitrile by using protein precipitation 96-well plates. The analyte was separated using a Phenomenex Kinetex Biphenyl column (100 × 2.1 mm, 2.6 µm) using isocratic elution with a mobile phase of 20 mM ammonium formate (30%) and acetonitrile:methanol 3:7 v:v (70%) at a flow rate of 0.5 mL/min and an injection volume of 10 µL. The detection was performed using a triple quadrupole mass spectrometer by multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 280.4 → 107.0 and 283.4 → 235.0 for doxepin and doxepin-D3, respectively, and 266.3 → 106.9 and 269.3 → 235.0 for nordoxepin and nordoxepin-D3, respectively, in positive electrospray ionization mode. The total run time was 3.5 min. The method was validated over a concentration range of 50-10,000 pg/mL using a Triple Quad 4500 MS System (Sciex) for both analytes. The developed and validated method can be successfully used to study the bioequivalence/pharmacokinetics of doxepin and nordoxepin.

Polythiophene/graphene oxide nanostructured electrodeposited coating for on-line electrochemically controlled in-tube solid-phase microextraction.

In this work, a novel polythiophene/graphene oxide (PTh/GO) nanostructured coating was introduced for on-line electrochemically-controlled in-tube solid phase microextraction of amitriptyline (AMI) and doxepin (DOX) as antidepressant drugs. The PTh/GO coating was prepared on the inner surface of a stainless steel tube by a facile in-situ electro-deposition method and it was used as a working electrode for electrochemically control in-tube solid phase microextraction. In the PTh/GO coating, GO acts as an anion dopant and sorbent. The PTh/GO coating, compared to PTh and GO coatings, exhibited enhanced long lifetime, good mechanical stability and a large specific surface area. Regarding the in-tube SPME, some important factors such as the extraction and desorption voltage, extraction and desorption times and flow rates of the sample solution and eluent, which could affect the extraction and separation efficiency of the analytes, were optimized. Total analysis time of this method including the online extraction and desorption time was about 21min for each sample. AMI and DOX were extracted, separated and determined with limits of detection as small as 0.3µgL-1 and 0.5µgL-1, respectively. This method showed good linearity in the range of 0.7-200µgL-1, 2.3-200µgL-1 and 2.9-200µgL-1 for AMI, and in the range 0.9-200µgL-1, 2.5-200µgL-1 and 3.0-200µgL-1 for DOX in water, urine and plasma samples, respectively; the coefficients of determination were also equal to or higher than 0.9976. The inter- and intra-assay precisions (RSD%, n=3) were in the range of 2.8-3.4% and 2.9-3.9% at the three concentration levels of 5, 25 and 50µgL-1, respectively. Finally, under the optimal conditions, the method was applied for the analysis of the drugs in human urine and plasma pretreated samples and good results were obtained.

Application of tandem dispersive liquid-liquid microextraction for the determination of doxepin, citalopram, and fluvoxamine in complicated samples.

A new type of dispersive liquid-liquid microextraction is used for the determination of doxepin, citalopram, and fluvoxamine in aqueous matrices. This method is based upon the tandem utilization of dispersive liquid-liquid microextraction, and by providing a high sample clean-up, it efficiently improves the applicability of the method in complicated matrices. For this purpose, in the first step, the analytes contained in an aqueous sample solution (8.0 mL) were extracted into an organic solvent, and then these analytes were simply back-extracted into an aqueous acceptor phase (50 µL). The overall extraction time was 7 min, and very simple tools were required for this aim. Optimization of the variables affecting the method such as the type and volume of the organic solvent used and effect of ionic strength was carried out to achieve the best extraction efficiency. Under the optimized experimental conditions, tandem dispersive liquid-liquid microextraction with high-performance liquid chromatography and UV detection showed a good linearity in the range of 10-5000 ng/mL. The limits of detection were in the range of 3-10 ng/mL. The Intra-day precisions (relative standard deviation) were 9.2, 4.5, and 4.8, and the recoveries were 58.5, 52.9, and 39.3% for citalopram, doxepin, and fluvoxamine, respectively.

Adsorption mechanisms of emerging micro-pollutants with a clay mineral: Case of tramadol and doxepine pharmaceutical products.

A sodium exchanged smectite clay mineral (Mt) was used as geo-sorbent for the adsorption of tramadol and doxepin: two pharmaceutical products (PPs) defined as emerging pollutants due to their presence at significant concentration in numerous water compartments. The adsorption isotherms for both the temperatures of 20 and 40°C and the derived data determined through the fitting procedure by using Langmuir, Freundlich and Dubinin-Radushkevich equation models explicitly pointed out that the sorption of both tramadol and doxepin is mainly driven by electrostatic interaction. The studied PPs are intercalated in a monolayer arrangement within the interlayer space through a cation exchange in stoichiometric proportion with the Na(+) cations leading to adsorbed PPs amounts that match the cation exchange capacity (CEC) of Mt. Due to their hydrophobic character, additional doxepin molecules could be adsorbed by weak molecular interaction driving to an increase of the adsorbed amount beyond the CEC at low temperature (20°C). The confinement of PPs within the interlayer space of Mt confirms the use of clay minerals as potential material for the wastewater treatment as well as it drives to an amorphous or glassy state, which can find echo in biopharmaceutical applications for a controlled release of PPs.

Electromembrane surrounded solid phase microextraction: a novel approach for efficient extraction from complicated matrices.

In the present work, electromembrane surrounded solid phase microextraction (EM-SPME) is introduced for the first time. The organic liquid membrane, which consists of 2-nitrophenyl octyl ether (NPOE), was immobilized in the pores of a hollow fiber (HF) and the basic analytes migrated in an electrical field from aqueous sample solution through the liquid membrane and into aqueous acceptor phase and then they were adsorbed on the solid sorbent, which acts as the cathode. Effective parameters such as composition of organic liquid membrane, pH of donor and acceptor phases, applied voltage and extraction time were optimized for extraction of amitriptyline (AMI) and doxepin (DOX) as model analytes and figures of merit of the method were investigated in pure water, human plasma, and urine samples. To extract the model analytes from 24 mL neutral sample solution across organic liquid membrane and into aqueous acceptor phase, 120 V electrical potential was applied for 20 min and finally the drugs were adsorbed on a carbonaceous cathode. Regardless of high sample cleanup, which make the proposed method suitable for the analysis of drugs from complicated matrices, extraction efficiencies in the range of 3.1-11.5% and good detection limits (less than 5 ngmL(-1)) with admissible repeatability and reproducibility (intra- and inter-assay precisions ranged between 4.0-8.5% and 7.5-12.2%, respectively) were obtained from different extraction media. Linearity of the method was studied in the range of 2.0-500.0 ngmL(-1) and 5.0-500.0 ngmL(-1) for AMI and DOX, respectively and coefficient of determination higher than 0.9947 were achieved. Finally, the proposed method was applied for the analysis of AMI and DOX in real samples.

Microcoil NMR study of the interactions between doxepin, ß-cyclodextrin, and acetate during capillary isotachophoresis.

The capillary isotachophoresis (cITP) separation of the isomers of the tricyclic antidepressant doxepin using ß-cyclodextrin (ß-CD) as a buffer additive is investigated by online microcoil NMR detection. Capillary electrophoresis (CE) is also used to determine the binding constant between the doxepin E and Z geometric isomers and ß-CD. Although the doxepin isomers could be easily baseline resolved by CE, their separation by cITP was more challenging due in part to the high concentration of doxepin after cITP-focusing. The use of online (1)H NMR detection allows observation of changes in doxepin dynamics due to formation of the ß-CD inclusion complex, changes in the fraction complexed and the intracapillary pH. It also provides novel experimental evidence that a weak complex between ß-CD and acetate contributes to its active transport from the leading electrolyte through the sample band to the trailing electrolyte in this cationic cITP separation. The results of these cITP-NMR experiments provide new mechanistic details about the interactions of the buffer counterion acetate with various components of the separation system and have important implications for other analyses based on formation of cyclodextrin inclusion complexes.

[Analysis of 37 drugs in whole blood by HPLC after solid phase extraction].

OBJECTIVE: To develop a specific, sensitive, reproducible SPE-HPLC method for the determination of 37 drugs in whole blood. METHODS: With the doxapram as internal standard, Oasis column was used to extract drugs from whole blood. Two kinds of mobile phases were used in this study. Separations were achieved by a LiChrospher 100 RP-C18 (250 mm x 4.0 mm x 5 microm) column kept at 50 degrees C, the DAD detector was set at 230 nm and 250 nm. RESULTS: The limit of detection were 1-30 ng/mL. The method showed excellent linearity and the linear correlation coefficient was > or =0.997 98. The relative standard deviation for between-day and within-day assay were <10%. CONCLUSION: The method is effective, simple, reliable and has been used in real cases.

Analysis of 37 drugs in whole blood by HPLC after solid phase extraction / 法医学杂志

OBJECTIVE@#To develop a specific, sensitive, reproducible SPE-HPLC method for the determination of 37 drugs in whole blood.@*METHODS@#With the doxapram as internal standard, Oasis column was used to extract drugs from whole blood. Two kinds of mobile phases were used in this study. Separations were achieved by a LiChrospher 100 RP-C18 (250 mm x 4.0 mm x 5 microm) column kept at 50 degrees C, the DAD detector was set at 230 nm and 250 nm.@*RESULTS@#The limit of detection were 1-30 ng/mL. The method showed excellent linearity and the linear correlation coefficient was > or =0.997 98. The relative standard deviation for between-day and within-day assay were <10%.@*CONCLUSION@#The method is effective, simple, reliable and has been used in real cases.

High-performance liquid chromatography of some basic drugs on a n-octadecylphosphonic acid modified magnesia-zirconia stationary phase.

The high-performance liquid chromatographic behavior of some basic drugs was studied on a n-octadecylphosphonic acid modified magnesia-zirconia (C18PZM) stationary phase. The effect of mobile phase variables such as methanol content, ionic strength, and pH on their chromatographic behavior was investigated. The retention mechanism of basic drugs on the stationary phase was elucidated. The results indicate that both hydrophobic and cation-exchange interactions contribute to solute retention under most chromatographic conditions. The inherent Brönsted-acid sites and also the adsorbed Lewis base anionic buffer constituents on accessible ZM surface Lewis acid sites play a role in the retention of ionized solutes by cation-exchange interaction. However, especially at high mobile phase pH, the retention of basic drugs depends mainly on hydrophobic interactions between solutes and support. Separations of the basic drugs on the C18PZM phase by a predominantly reversed-phase retention mode were very promising. The mixed-mode retention feature on this phase, as a result of the adsorbed Lewis base anionic buffer constituents acting as sites for cation-exchange, could also be very useful, e.g. for enhancing the chromatographic selectivity of such analytes. The C18PZM seems to be an excellent alternative to silica-based reversed-phase stationary phase for the separation of strongly basic solutes.

[Testing of some dibenzoazepines and dibenzocycloheptadiene derivatives with high pressure thin layer chromatography]. / Badania niektórych pochodnych dibenzoazepiny i dibenzocykloheptadienu metoda chromatografii cienkowarstwoweji wysokosprawnej cieczowej.

An influence of several adsorbents and the composition of the eluent mixtures on the separation of dibenzoazepine and dibenzocycloheptadiene derivatives was examined by thin-layer chromatography. The best system (RP-18 and methanol-buffer solution pH 8.5 19:1) was employed for the separation of amitryptiline and doxepine by HPLC. Both compounds were determined in ng amounts in pharmaceutical preparations and in blood by addition and in patients blood. Doxepine was used as internal standard for the determination of amitryptiline.