Hollow Fiber Solvent Bar Microextraction Research Articles

Multi-residue analysis of pesticides in blood plasma using hollow fiber solvent bar microextraction and gas chromatography with a flame ionization detector

The challenges faced on pesticide extraction from biological samples are finding a method that allows a multi-residue extraction, pre-concentration, clean-up, and isolation of analytes in just one step. In this sense, the hollow fiber – liquid phase microextraction method (HF- LPME) in the "solvent bar" mode was used to optimize and validate a method for pesticide multi-residue analysis in blood plasma at trace levels, through gas chromatography coupled with a flame ionization detector (GC-FID). Hollow fiber solvent bar microextraction HF-SBME was carried out with octanol immobilized into the pores of hydrophobic polypropylene fiber and disposed within a matrix of blood plasma, spiked with a mixture of pesticides (monocrotophos, lindane, aldrin, methyl parathion, endosulfan, dieldrin, DDD, DDT, and endrin). The optimization parameters evaluated were: extraction temperature and time, stirring speed, and salt concentration. A principal component analysis was performed to visualize the analytes' behaviour based on their explained variance, and then, a Box-Behnken analysis was generated to identify the optimum parameters. According to the PCA, all pesticides showed similar responses to the extraction method and the response of dieldrin exhibit the lowest variance. Moreover, the stationary points selected from the Box-Behnken analysis were 25.5 °C for the extraction temperature, 870 rpm for stirring speed, 16 min for extraction time, and 8.3 % w/v of salt concentration. Moreover, the validation results proved that HF-SBME is an alternative technique for pesticide multi-residue extraction in blood plasma. The analytes were able to concentrate, reaching 46 fold enrichment. The solvent type, sample and solvent volume were narrowed down without changing the method's precision or accuracy. The relative standard deviation was under 10 %, and the recovery was between 55 % and 105 % for the different analytes excepting lindane, which had lower recovery (27 %). The detection limits were 0.02 until 0.13 μg mL−1 for most of the pesticides used. Finally, HF-SBME is a good alternative for pesticide multi-residue extraction in complex matrices like plasma.

Solvent holder-assisted liquid-phase microextraction using nano-structure biomass-derived carbonaceous aerogel combined with ion mobility spectrometry for simultaneous determination of ethion and chlorpyrifos.

A biomass-derived sponge-like carbonaceous aerogel was prepared through a two-step procedure, including hydrothermal carbonization and freeze-drying process. The aerogel was employed as the solvent holder for liquid-phase microextraction of organophosphorus pesticides, ethion, and chlorpyrifos (as the model compounds), prior to determination by secondary electrospray ionization-ion mobility spectrometry. The carbonaceous aerogel is an appropriate candidate to beused as the solvent holder due to some properties such as three-dimensional structure, porous nature, and very low density. So, the aerogel, including extraction solvent, can tumble on the top of the sample solution, without loss of solvent during its agitation. A comparison of the extraction efficiency was performed at similar conditions between theproposed method and single-drop microextraction, as well as hollow-fiber solvent bar microextraction. Different parameters affecting the extraction efficiency, such as stirring rate, salt concentration, temperature, and extraction time were investigated by using the response surface methodology. The linear dynamic range was in the ranges 1-30 and 1-70μgL-1 with regression coefficients of 0.9973 and 0.9956 for ethion and chlorpyrifos, respectively. The limit of detection was 0.09 and 0.21μgL-1 for ethion and chlorpyrifos, respectively. The method was used for extracting analytes from environmental water and vegetable samples, with the spiking recoveries in the range 80-121%. Graphical abstract Schematic representation of three-dimensional biomass-derived carbonaceous aerogel as the solvent holder in solvent bar microextraction (as a mode of the liquid-phase microextraction method). It was used for the extraction of two kinds of organophosphorus pesticides prior to the determination by ion mobility spectrometry.

Hollow Fiber/Solvent Bar Microextraction Coupled with High Performance Liquid Chromatography for Preconcentration and Determination of Tanshinones and Salvianolic Acids in Radix Salvia miltiorrhiza

Hollow fiber solvent bar microextraction coupled with high-performance liquid chromatography was developed for the preconcentration and determination of active ingredients in Radix Salvia miltiorrhiza. These ingredients include dihydrotanshinone I, cryptotanshinone, tanshinone I, tanshinone IIA, salvianolic acid B, danshensu, and protocatechuic aldehyde. To evaluate the technique, seven compounds of varying polarity were used as model analytes, and a polyvinylidene fluoride hollow fiber (1.0 cm) with octanol (2 µL) was used as microextraction bar. The extraction conditions, including the identity of the hollow fiber, organic solvent, pH, salt addition, agitation speed, extraction time, and volume, were investigated and optimized. The extraction mechanism was analyzed and verified. The two main parameters, extraction recovery and enrichment factor, were obtained. Under the most favorable conditions, the enrichment factors of the analytes were 0.7–612, the limits of detection were below 1.11 ng mL−1, and the recoveries were between 95.4% and 101.3%. Thus, hollow fiber solvent bar microextraction is simple, rapid, and practical with a wide range of potential applications.

Vortex solvent bar microextraction for phthalate esters from aqueous matrices

An improved hollow fiber solvent bar microextraction method termed as vortex solvent bar microextraction (VSBME) was developed. A short hollow fiber immobilized with organic extraction solvent was served as the solvent bar for microextraction of phthalate esters from aqueous matrices. The hydrophobic analytes were pre-focused at the bottom of the vortex under the vigorous magnetic stirring before extraction, which facilitated the mass transfer of analytes from aqueous matrix to organic extraction phase in the subsequent solvent bar microextraction. With the extraction solvent lost gradually from the hollow fiber under the stirring, the efficient extraction was maintained by the absorption of analytes in the porous membrane. After extraction, the analytes were desorbed from the hollow fiber membrane using 50μL organic solvent. The phthalate esters with 1-octanol/water partition coefficients ranging from 1.69 to 8.83 were used as model compounds to investigate the extraction performance. Extraction conditions such as type and volume of extraction solvents, stirring intensity, extraction time, sample concentration and volume were investigated and optimized. Analysis was carried out with gas chromatography–mass spectrometry (GC–MS). Under the optimum conditions, this new method gave super high enrichment factors (over 1500), good reproducibility (<7.1%, n=6) in a rapid extraction within 5min. It allowed the determination of phthalate esters at ngL−1 level. Compared with the other microextraction methods, the proposed VSBME was simpler, more robust and had higher enrichment efficiency. The matrix effects on the extraction performance were also investigated with bottled ice red tea, red wine and human urine.