Direct coupling of microcolumn liquid chromatography with in-tube solid-phase microextraction for the analysis of antidepressant drugs

Innovative extraction materials for fiber-in-tube solid phase microextraction: A review

Fiber-in-tube solid-phase microextraction (fiber-in-tube SPME) with short capillary longitudinally packed with fine fibers as extraction device allows direct coupling to high performance liquid chromatography (HPLC) systems to determine weakly volatile or thermally labile compounds. This technique associates the advantages of miniaturized and analytical on-line systems. Major achievements include the use of different capillaries (fused-silica, copper, stainless steel, polyetheretherketone (PEEK), or poly(tetrafluoroethylene) (PTFE)) that are packed with neat fibers (Zylon®, silk, or Kevlar 29®) or fibers (stainless steel, basalt, or carbon) functionalized with selective coatings (aerogels, ionic liquids (ILs), polymeric ionic liquids (PILs), molecularly imprinted polymers (MIPs), layered double hydroxides (LDHs), or conducting polymer). This review outlines the fundamental theory and the innovative extraction materials for fiber-in-tube SPME-HPLC systems and highlights their main applications in environmental and bioanalyses.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

Synthesis of an organic-inorganic hybrid absorbent for in-tube solid-phase microextraction of bisphenol A

This research is an application of fiber-in-tube solid-phase microextraction followed by high-performance liquid chromatography with UV detection for the extraction and determination of trace amounts of bisphenol A. Nanomagnetic Fe₃ O₄ was formed on the surface of polypropylene porous hollow fibers to increase the surface area and then it was coated with polystyrene. The introduction of polystyrene improves the surface hydrophobicity and is an appropriate extractive phase because it is highly stable in aquatic media. The extraction was carried out in a short capillary packed longitudinally with the fine fibers as the extraction medium. Extraction conditions, including extraction and desorption flow rates, extraction time, pH, and ionic strength of the sample solution, were investigated and optimized. Under optimal conditions, the limit of detection was 0.01 µg/L. This method showed good linearity for bisphenol A in the range of 0.033-1000 µg/L, with the coefficient of determination of 0.9984. The inter- and intraday precisions (RSD%, n = 3) were 7.9 and 6.3%, respectively. Finally, the method was applied to analysis of the analyte in thermal papers, disposable plastic cups, and soft drink bottles.

Bioanalytical HPLC Applications of In-Tube Solid Phase Microextraction: A Two-Decade Overview

In-tube solid phase microextraction is a cutting-edge sample treatment technique offering significant advantages in terms of miniaturization, green character, automation, and preconcentration prior to analysis. During the past years, there has been a considerable increase in the reported publications, as well as in the research groups focusing their activities on this technique. In the present review article, HPLC bioanalytical applications of in-tube SPME are discussed, covering a wide time frame of twenty years of research reports. Instrumental aspects towards the coupling of in-tube SPME and HPLC are also discussed, and detailed information on materials/coatings and applications in biological samples are provided.

An organically modified silica aerogel for online in-tube solid-phase microextraction

Aerogels have received considerable attentions because of its porous, high specific surface, unique properties and environmental friendliness. In this work, an organically modified silica aerogel was functionalized on the basalt fibers (BFs) and filled into a poly(ether ether ketone) (PEEK) tube, which was coupled with high performance liquid chromatography (HPLC) for in-tube solid-phase microextraction (IT-SPME). The aerogel was characterized by scanning electron microscopy (SEM) and fourier transform infrared spectrometry (FT-IR). The extraction efficiency of the tube was systematically investigated and shown enrichment factors from 2346 to 3132. An automated, sensitive and selective method was developed for the determination of five estrogens. The linear range was from 0.03 to 100μgL^-1 with correlation coefficients (r) higher than 0.9989, and low detection limits (LODs) were 0.01-0.05μgL^-1. The relative standard deviations (RSDs) for intra-day and inter-day were less than 4.5% and 6.7% (n=6), respectively. Finally, the analysis method was successfully applied to detect estrogens in sewage and emollient water samples.

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.

The current role of on-line extraction approaches in clinical and forensic toxicology

In today's clinical and forensic toxicological laboratories, automation is of interest because of its ability to optimize processes, to reduce manual workload and handling errors and to minimize exposition to potentially infectious samples. Extraction is usually the most time-consuming step; therefore, automation of this step is reasonable. Currently, from the field of clinical and forensic toxicology, methods using the following on-line extraction techniques have been published: on-line solid-phase extraction, turbulent flow chromatography, solid-phase microextraction, microextraction by packed sorbent, single-drop microextraction and on-line desorption of dried blood spots. Most of these published methods are either single-analyte or multicomponent procedures; methods intended for systematic toxicological analysis are relatively scarce. However, the use of on-line extraction will certainly increase in the near future.

Bio-sample preparation and analytical methods for the determination of tricyclic antidepressants

An extended and comprehensive review is presented herein, focusing on sample preparation (pretreatment and extraction) and different analytical methods applied for the quantification of tricyclic antidepressants. These procedures are relevant tools in clinical and forensic toxicology. It is revealed that SPE, for sample preparation, and HPLC, using reversed-phase alkyl (C18) or cyanopropyl-bonded silica columns for the analytes separation, are effective and versatile methods for assay of tricyclic antidepressants. These methods enable achievable detection limits using UV/diode array detection, readily available in most laboratories, down to 1–8 ng ml-1, and using electron capture detection better than 1 ng ml-1, which is lower than that for nitrogen–phosphorus detector. MS interfaced with electrospray ionization offered similar sensitivity, whilst sonic spray ionization provided detection down to 0.03 ng ml-1. A brief discussion on chemical structures, metabolism and mechanism of action of this group of drugs is also presented.