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.

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.

[Determination of three urinary catecholamines and serotonin by on-line packed-fiber solid-phase extraction].

Biogenic monoamines, including catecholamines (CAs) and serotonin (5-HT), play critical roles in the central nervous system. They have recently been proven to be primarily useful as biomarkers for the diagnosis of CA-producing tumors. The highly polar properties of biogenic monoamines result in poor retention on conventional materials, making it challenging to simultaneously measure more biogenic monoamines from complex matrices. Moreover, the classical method of off-line pretreatment is relatively complex, labor-intensive, and incurs errors in repeatability among different operators. Therefore, the development of an on-line sample pretreatment method combined with the use of specific nanofiber adsorbents has been explored. An on-line procedure could avoid unnecessary and time-consuming steps, and enable full automation of the experimental process. In this study, an on-line packed-fiber solid-phase extraction (PFSPE) and determination method for urinary CAs (dopamine (DA), norepinephrine (NE), epinephrine (E)) and 5-HT was developed, using composite nanofibers of polycrown ether-polystyrene (PCE-PS). PCE-PS composite nanofibers prepared by electrospinning were used as adsorbents in the PFSPE column, which was connected to the on-line HPLC system. The PFSPE-HPLC equipment contained a dual ternary pump and a switching valve to enable enrichment, purification, and analysis directly in the system. The left pump was connected with the PFSPE column for sample enrichment and purification, while the right pump was attached to the analysis column for sample separation and testing. The switching valve was controlled such that after enrichment, the samples could be eluted to the analysis column for separation and detection. The current work expands on our previous research by analyzing more target substances, and developing an on-line sample pretreatment method to simultaneously analyze four biogenic monoamines. Gradient separation aided in the satisfactory separation of the biogenic monoamines within a short retention time. The running time was set at 16 min to enable thorough enrichment, elution, and analysis. The influence of the complexing reagent (diphenylborinic acid 2-aminoethyl ester, 2 mg/mL) was also investigated with this on-line PFSPE-HPLC system. The results showed that the intensity of most analytes was significantly higher when 50 µL of the complexing reagent was added. The influence of a buffer on the extraction of the biogenic monoamines was also tested. The optimum extraction condition for the target analytes was achieved when artificial urine (AU) samples were diluted in a volume ratio of 1∶1 by phosphate- buffered saline solution (PBS, pH 7.8). Under the optimum experimental conditions, the on-line PFSPE-HPLC procedure showed good linearity (in the range of 1 ng/mL to 200 ng/mL) with correlation coefficients above 0.996 for the quantitative detection of urinary CAs (DA, NE, E) and 5-HT. For the CAs, the limit of detection (LOD) was 1 ng/mL (S/N=3), while the limit of quantitation (LOQ) was 2.5 ng/mL (S/N=10). For 5-HT, the LOD was 2.5 ng/mL (S/N=3) and the LOQ was 5 ng/mL (S/N=10). Moreover, high recovery rates and good reproducibility were obtained. The recoveries of AU and real urine spiked with CAs and 5-HT were in the range of 83.5%-117.7%, and the intra-day precision was lower than 10%. Additionally, no significant changes in the nanofibers were observed after repeated extraction, which reflected the good stability and reusability of the nanofibers. The nanofibers could be reused for more than 95 times. The on-line PFSPE-HPLC system was successfully applied for the determination of urinary CAs and 5-HT with good precision and high sensitivity. This high level of integration and automation was significantly advantageous in terms of its repeatability, as well as reduction in the time and effort required. The proposed on-line pretreatment and determination method can provide strong technical support for the detection and diagnosis of, as well as research on related diseases in clinical practice.