Composite Nanofibers as Novel Sorbents for On-Line and Off-Line Solid-Phase Extraction in Chromatographic System: A Comparison for Detection of Free Biogenic Monoamines and Their Metabolites in Plasma.

Two different pretreatment approaches have been used for the enrichment and separation of biogenic monoamines and metabolites in plasma for high performance liquid chromatography (HPLC) determination. The first approach, based on on-line packed-fiber solid-phase extraction (PFSPE) coupled with HPLC, allows for the simultaneous detection of epinephrine (E), norepinephrine (NE), dopamine (DA), 3-methoxyl epinephrine (MN), norepinephrine (NMN), 3-methoxytyramine (3-MT), and 5-hydroxytryptamin (5-HT). Using this developed on-line PFSPE-HPLC method, the limit of detections (LODs) of the seven analytes ranged from 1 ng/mL (NMN and MN) to 2 ng/mL (NE, E, DA, 3-MT and 5-HT). The reportable ranges were 5-300 ng/mL for NE and DA, 5-100 ng/mL for E, and 5-200 ng/mL for NMN, MN, 3-MT and 5-HT. The off-line PFSPE-HPLC was employed in the second approach and could provide simultaneous detection of NE, E, DA, NMN, and MN. The linearity was verified in the range of 0.5-20 ng/mL (NE, E, and DA) and 20-250 ng/mL (NMN and MN). The LODs of the five analytes ranged from 0.2 ng/mL (NE, E, and DA) to 5 ng/mL (NMN and MN). This study verified the possibility of using nanofibers as an adsorbent in an on-line PFSPE-HPLC system for the determination of biogenic monoamines and their metabolites in human plasma. Compared with the off-line PFSPE approach, the on-line PFSPE method deserves attention mainly due to its greener character, derived from the automation of the process and high-throughput with less operators' handling.

Polystyrene nanofibers capped with copper nanoparticles for selective extraction of glutathione prior to its determination by HPLC.

Polystyrene nanofibers were coated with copper nanoparticles (CuNPs) by a combination of electrospinning and in-situ reduction of Cu(II) using sodium borohydride as the reductant. The CuNPs on the nanofibers were characterized by energy dispersive spectrometry, scanning electron microscopy and transmission electron microscopy. A cartridge was packed with the nanofibers which then were activated with methanol and water. Glutathione (GSH) is found to quantitatively adsorbed by the packed cartridge at pH 3.0, and then can be desorbed with aqueous 2-mercaptoethanol and detected, after derivatization with ortho-phthalaldehyde, via high performance liquid chromatography with fluorometric detection. Under optimized conditions, the method has a 1.1 ng·mL-1 detection limit and a response that is linear in the 10-1000 ng·mL-1 GSH concentration range. The recoveries of GSH from artificial urine spiked at three levels (80, 400 and 800 ng·mL-1) are in the range of 94.6-98.6% with relative standard deviations (RSD) of <4.5% (n = 5). The method was applied to assessing the differences in urinary GSH between high-risk infants and healthy infants. The results show that the levels of GSH of normal infants are significantly higher than those of high-risk infants (P < 0.05). Graphical abstract Schematic of the preparation of CuNP-assembled nanofibers and the mechanism of extracting glutathione (GSH). GSH can be extracted by this material based on a strong interaction between the sorbent and GSH. This is attributed to the formation of Cu-S bonds between Cu and -SH.

Selective solid-phase extraction of catecholamines from plasma using nanofibers doped with crown ether and their quantitation by HPLC with electrochemical detection.

A simple and convenient preparation method has been developed for polymeric crown ethers containing the dibenzo-18-crown-6 subunit and electrospun composite nanofibers composed of polymeric crown ethers with polystyrene (PCE-PS). Furthermore, this composite nanofiber was used as a sorbent for selective extraction of plasma catecholamines, viz. dopamine (DA), norepinephrine (NE), and epinephrine (E). After the protein deposition of the plasma sample, the supernatant was adjusted to neutral pH with buffer solution. Then, the mixture was loaded and pushed through a column packed with composite nanofiber sorbent, and the analytes were eluted with 50 µL of acetic acid. The effectiveness of the plasma sample cleanup method was verified by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The PCE-PS packed column may prove clinically useful, as it provides a convenient and selective method for evaluation of human plasma catecholamines. Graphical Abstract Scheme showing the selective packed fiber SPE of catecholamines from spiked plasma using nanofibers doped with ploymeric crown ether.

Electrospun Polycrown Ether Composite Nanofibers as an Adsorbent for On-Line Solid Phase Extraction of Eight Bisphenols from Drinking Water Samples with Column-Switching Prior to High Performance Liquid Chromatography.

Bisphenols (BPs) are a class of endocrine disruptors widely existing in the environment. They have a great impact on human health owing to their environmental endocrine disrupting effects, chronic toxicity, neurotoxicity, cytotoxicity and genetic toxicity. In this paper, an on-line packed fiber solid phase extraction (PFSPE) coupling with column-switching HPLC-FLD determination method was developed for the determination of eight BPs in drinking water. The poly (dibenzo-18-crown-6-ether)/polystyrene composite nanofibers (PDB18C6/PS) were prepared by electrospinning and used as an adsorbent for the on-line PFSPE column. The on-line PFSPE-HPLC equipment contained a dual ternary pump and a switching valve to enable enrichment, purification, and analysis directly in the system. The results showed that the proposed on-line PFSPE-HPLC-FLD method realized the simultaneous separation and detection of eight BPs: BPF, BPE, BPA, BPB, BPAF, BPAP, BPC and BPZ. The curves of the target analytes were prepared with good correlation coefficient values (r2 > 0.998) in the range of 50−1000 pg/mL. The limit of detection (S/N = 3) was 20 pg/mL, the limit of quantitation (S/N = 10) is 50 pg/mL. The recoveries of eight BPs were 94.8−127.3%, and the intra-day precisions (RSD) were less than 10%. The PFSPE column made of the PDB18C6/PS composite nanofibers has stable properties and can be reused at least 200 times. In the detection of drinking water samples, BPZ was detected in nearly 80% of drinking water samples, and BPA, BPAP, BPF and BPAF were also detected in some water samples. This high level of integration and automation was achieved in pretreatment of eight BPs from water samples. The proposed simple, rapid, and practical method has been successfully applied to the detection of eight BPs in drinking water, which can provide powerful technical support for drinking water quality and safety monitoring.

Simultaneous Determination of Nine Quinolones in Pure Milk Using PFSPE-HPLC-MS/MS with PS-PAN Nanofibers as a Sorbent.

In this study, a packed-fiber solid-phase extraction (PFSPE)-based method was developed to simultaneously detect nine quinolones, including enrofloxacin (ENR), ciprofloxacin (CIP), ofloxacin (OFL), pefloxacin (PEF), lomefloxacin (LOM), norfloxacin (NOR), sarafloxacin (SAR), danofloxacin (DAN), and difloxacin (DIF), in pure milk, using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Polystyrene (PS) and polyacrylonitrile (PAN) were combined to form PS-PAN composite nanofibers through electrospinning. The nanofibers were used to prepare the home-made extraction columns, and the process was optimized and validated using blank pure milk. The analytical method showed high accuracy, and the recoveries were 88.68-97.63%. Intra-day and inter-day relative standard deviations were in the ranges of 1.11-6.77% and 2.26-7.17%, respectively. In addition, the developed method showed good linearity (R2 ≥ 0.995) and low method quantification limits for the nine quinolones (between 1.0-100 ng/mL) for all samples studied. The nine quinolones in the complex matrix were directly extracted using 4.0 mg of PS-PAN composite nanofibers as a sorbent and completely eluted in 100 µL elution solvent. Therefore, the developed PFSPE-HPLC-MS/MS is a sensitive and cost-effective technique that can effectively detect and control nine quinolones in dairy products.

Automated on-line packed fiber solid phase extraction for determination of urinary catecholamines.

Despite the development of an off-line packed fiber solid phase extraction procedure (PFSPE) for urinary catecholamines, automation remains a challenge. Here, we propose an on-line PFSPE-HPLC procedure for automated sample processing and analysis of urinary catecholamines, with good recovery and precision, to avoid manual operation errors. The on-line PFSPE-HPLC procedure has been thoroughly optimized concerning the gradient, valve switch timing, the effects of complexing reagent and buffer solution, and the stability of the nanofibers. Validation of the developed on-line PFSPE-HPLC protocol in urine yielded satisfactory accuracies of 99.6-104.2%, precision below 7.0%, as well as a linear range from 1 ng/mL to 100 ng/mL with a correlation coefficient of 0.999. The developed protocol is herein presented as a potential technology for automated sample pretreatment for the determination of urinary catecholamines.

Simultaneous analysis of two urinary biomarkers of oxidative damage to DNA and RNA based on packed-fiber solid phase extraction coupled with high-performance liquid chromatography.

The determination of the concentrations of urinary biomarkers of oxidative damage to DNA and RNA is difficult due to the low content of targets and the complex matrix of urine. A method using polystyrene/polypyrrole (PS/PPY) electronspun nanofibers as the adsorbent was introduced to the routine urinary treatment and determination of 8-OHdG and 8-oxoG for the first time. And 2-aminoethyl diphenylborate (DPBA) solution was creatively used in the loading and rinsing steps in order to promote the retention of the analytes as well as remove impurities. Under optimal conditions, 8-OHdG, 8-oxoG and IS were separated very well and exhibited a good linearity in the range of 0.5-50 ng mL-1, with correlation coefficients of R2 > 0.996. Limits of detection (LOD) were 0.058 ng mL-1 and 0.093 ng mL-1, and limits of quantification (LOQ) were 0.195 ng mL-1 and 0.309 ng mL-1, respectively. The recoveries were 88.8-104.9%. The proposed method was so simple and economical that it had the potential to be applied to batch quantitative analysis of 8-OHdG and 8-oxoG in urine. And it was successfully applied to real urine samples of cancer patients.

Solid phase extraction with Polypyrrole nanofibers for simultaneously determination of three water-soluble vitamins in urine.

This paper put forward a prospective pre-cleanup method of packed-fiber solid phase extraction by using Polypyrrole (Ppy) electrospun nanofibers as the sorbent to simultaneously extract three water-soluble vitamins (i.e., folic acid, cyanocobalamin and riboflavin) in human urine. Primary extraction of target analytes was carried out by loading samples onto the column along with diphenylboronic acid 2-aminoethylester (DPBA) reagent, and then the column should be rinsed with DPBA solution for three times before eluting. The DPBA was innovatively applied as complexing reagent to retain as much of three analytes as possible on the column based on the multi interaction between three vitamins and the boronate affinity reagent, thus improving hydrophobicity of targets and adsorption efficiency through loading and rinsing steps. Under optimized conditions, sample concentration factor was five times with small amount of organic solvent consumed and recoveries between 84.9% to 125.4%, and the lowest detection limit (LOD) between 0.020 to 0.041 µg/mL were achieved. Finally, the urine samples from a group of healthy children were processed with the optimized method. It proved that the proposed method is applicable in the determination of urinary B-vitamins in big samples of people.

Packed-Nanofiber solid phase extraction coupled with gas chromatography-mass spectrometry for the determination of phthalate esters in urines from children.

In this paper, we developed a rapid and safe method based on packed-fiber solid-phase extraction (PFSPE) system coupled with gas chromatography-mass spectrometry for the determination of four phthalate esters (PAEs), diethyl-o-phthalate (DEP), dibutyl-o-phthalate (DBP), di (2-ethylhexyl) phathalate (DEHP), di-n-octyl phthalate (DNOP), in urine samples. The PAEs in urine samples (500µL) were rapidly cleaned up from urines using polystyrene (PS) nanofibers packed micro-columns fitted on a PFSPE pretreatment device, which can process up to 12 samples simultaneously in 5min. Under optimum conditions, satisfied recovery and relative standard deviation values (RSDs) were in the range of 80.4-111.7% and 1.5-10.9%, respectively. The limits of detection (LOD) and the limits of quantification (LOQ) were ranged from 0.1 to 0.5ngmL-1 and 0.5-2ngmL-1, respectively. The well controlled matrix effect was also evaluated by comparing the signal response of the pure PAEs standards dissolved in methanol with the signal response of PAEs in the urine matrix. This new method was successfully applied to determine four PAEs in urine samples of overweight and normal-weight children, and an association between phthalates in urines and obesity was observed. Thus, the method seems to be a useful tool for monitoring of the level of urinary phthalate esters and also to support an evidence for further reasearch of obesity.

Simultaneous quantification of cortisol and cortisone in urines from infants with packed-fiber solid-phase extraction coupled to HPLC-MS/MS.

Cortisol and cortisone are two important glucocorticoids in human body, their interconversion is controlled by two isotypes of 11ß-hydroxy steroid dehydrogenase (11ß-HSD1 and 11ß-HSD2). The ratio of urinary cortisol to cortisone can be used to assess the activity of 11ß-HSDs. An analytical method to quantify urinary cortisol and cortisone using high performance liquid chromatographic tandem mass spectrometry following a packed-fiber solid-phase extraction (PFSPE) was developed. The proposed method was validated and applied to determine the urinary cortisol and cortisone concentrations in infants. Linearity was observed in the range of 0.6-150ng/mL for cortisol and 0.8-200ng/mL for cortisone. The intra-day RSD was 2.4-4.5% for cortisol and 3.3-6.2% for cortisone. Inter-day RSD was 3.7-6.6% for cortisol and 4.3-8.2% for cortisone. The recovery was 97.8±4.6% for cortisol and 98.9±4.4% for cortisone. The established method is simple and efficient for the quantification of urinary cortisol and cortisone and for indirectly assessing the activity of 11ß-hydroxy steroid dehydrogenase.

Packed-fiber solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry for determination of diethylstilbestrol, hexestrol, and dienestrol residues in milk products.

A sensitive analytical method based on packed-fiber solid-phase extraction and high performance liquid chromatography-tandem mass spectrometry (PF SPE-HPLC-MS/MS) has been developed for determination of three synthetic stilbenes in milk. The stilbenes are extracted with acetonitrile, using sodium chloride, and purified with PF SPE using a cartridge containing electrospun polystyrene nanofibers. Parameters affecting the efficiency of PF SPE, such as pH and amount of salt, were optimized. Under optimal conditions, the limits of detection and quantification were 5-13pg/g and 15-37pg/g, respectively. Absolute recoveries varied between 60% and 85% at three different levels. The method was successfully applied for the determination of estrogenic stilbenes in a total of 69 milk samples. The method is sensitive and cost-effective in stilbene detection, and has potential in quality control of dairy products.

Determination of Quinolones in Spicy Soup Using Packed Fiber Solid Phase Extraction and High Performance Liquid Chromatography-Fluorimetric Detection / 分析化学

An analytical method for simultaneous determination of five quinolones in spicy soup was developed. Spicy soup samples were firstly extracted by EDTA-Mcllvaine buffer at pH 4, then purified and concentrated by a novel Packed fiber solid phase extraction ( PFSPE ) coulumn. The extracted liquid supernatant was loaded onto the column, rinsed with water, and then eluted with 2% ammoniated methanol. The mobile phase was methanol-water-phosphoric acid (25:75:0. 1, V/V, adjusting the pH to 2. 8 with triethylamine) . These analytes were quantified by high performance liquid chromatography-fluorimetric detector( HPLC-FLD) at excitation and emission wavelength of 280 nm and 450 nm respectively. Recoveries of spiked quinolone antibiotics in spicy soup were from 72 . 1% to 110 . 3% with intraday relative standard deviation (RSD) between 1. 6% and 4. 3% and inter-day RSD from 2. 0% to 4. 3%. Limit of detection (LOD) and limit of quantitation(LOQ) were from 1. 2 to 5. 4 μg/L and from 3. 9 to 18 μg/L, respectively. The method could be applied to determine the quinolones in spicy soup.