Adsorptive behavior and solid-phase microextraction of bare stainless steel sample loop in high performance liquid chromatography

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.

Self-acidity induced effervescence and manual shaking-assisted microextraction of neonicotinoid insecticides in orange juice

A novel dispersive liquid-liquid microextraction that combines self-induced acid-base effervescent reaction and manual shaking, coupled with ultra high performance liquid chromatography with tandem mass spectrometry was developed for simultaneous determination of ten neonicotinoid insecticides and metabolites in orange juice. An innovative aspect of this method was the utilization of the acidity of the juice for a self-reaction between acidic components contained in the juice sample and added sodium carbonate which generated carbon dioxide bubbles in situ, accelerating the analytes transfer to the extractant of 1-undecanol. The total acid content of juice sample was measured to produce the maximum amount of bubbles with minimum usage of carbonate. Manual shaking was subsequently adopted and was proven to enhance the extraction efficiency. The factors affecting the performance, including the type and the amount of the carbon dioxide source and extractant, and ionic strength were optimized. Compared with conventional methods, this approach exhibited low limits of detection (0.001-0.1 µg/L), good recoveries (86.2-103.6%), high enrichment factors (25-50), and negligible matrix effects (-12.3-13.7%). The proposed method was demonstrated to provide a rapid, practical, and environmentally friendly procedure due to no acid reagent, toxic solvent, or external energy requirement, giving rise to potential application on other high acid-content matrices.

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.

Selective and sensitive determination of protoberberines by capillary electrophoresis coupled with molecularly imprinted microextraction

In this work, we developed a novel molecularly imprinted solid-phase microextraction with capillary electrophoresis method for the selective extraction and determination of protoberberines in complicated samples. The imprinted monolith was prepared in a micropipette tip-based device by using acrylamide as the functional monomer, ethyleneglyoldimethacrylate as the cross-linker and dimethylsulfoxide as the porogen, and exhibited an imprinting factor of 2.41 to berberine, 2.36 to palmatine and 2.38 to jatrorrhizine. Good capillary electrophoresis separation was achieved by using 20 mM phosphate buffer at pH 7 as running buffer with the addition of organic modifier of 10% methanol. Parameters such as sample pH value, sample flow rate and sample volume were investigated for imprinted monolith-based solid-phase microextraction. An imprinted solid-phase microextraction with capillary electrophoresis method was developed, the method showed a wide linear range (0.3-50 μg/mL), good linearity (R² ≥ 0.9947) and good reproducibility (relative standard deviations ≤ 0.73%), the limit of detection was as low as 0.1 μg/mL, which was lower than some reported methods based on capillary electrophoresis for protoberberines. The method has been applied for determination of three common protoberberines in Cortex Phellodendri Chinensis, by using a molecularly imprinted monolith as the selective sorbent, most of the matrices in the Cortex Phellodendri Chinensis sample were removed and three protoberberines were selectively enriched and well determined.