Rational analysis of data from LC-MS/MS: new insights in acylcarnitines as biomarkers for brain disorders or neurotoxicity.

Objective: LC-MS/MS-based metabolomics is an important tool for studying disease-related biomarkers. Conventionally, different strategies have been used to screen biomarkers. However, many studies for biomarker screening by different strategies have ignored the dose-response relationship between the biomarker level and exposure level, and no relevant studies have described and compared different strategies in detail. Phenobarbital (PHB) which belongs to the barbiturates, was selected as the typical representative of neurotoxins. Acylcarnitines have been promising candidates for diagnostic biomarkers for several neurological disorders and neurotoxicity. In this work, we aimed to use an acute PHB poisoning animal model to clarify PHB poisoning effects on plasma and brain acylcarnitine changes and how to rationally analyze data from LC-MS/MS. Methods: The acylcarnitine profiles in plasma and brain regions in an actuate PHB poisoning animal model were utilized. The dose-response relationship between plasma PHB and carnitine and acylcarnitines (CARs) in plasma and brain were assessed by the variance analysis trend test and Spearman's rank correlation test. In different strategies, principal component analysis (PCA) and partial least squares discriminant analysis (OPLS-DA) screened the differential CARs, variable importance plots (VIPs) were utilized to select putative biomarkers for PHB-induced toxicity, and receiver operating characteristic (ROC) curve analysis then illustrated the reliability of biomarkers. Results: Under the first strategy, 14 potential toxicity biomarkers were obtained including eight downregulated CARs with AUC >0.8. Under the second strategy, 11 potential toxicity biomarkers were obtained containing five downregulated CARs with AUC >0.8. Only when the dose-response relationship was fully considered, different strategies screen for the same biomarkers (plasma acetyl-carnitine (C2) and plasma decanoyl-carnitine (C10)), which indicated plasma acylcarnitines might serve as toxicity biomarkers. In addition, the plasma CAR level changes showed differences from brain CAR level changes, and correlations between plasma CARs and their brain counterparts were weak. Conclusion: We found that plasma C2 and C10 might serve as toxicity biomarkers for PHB poisoning disorders, and PHB poisoning effects on changes in plasma CARs may not be fully representative of changes in brain CARs.

Investigation of biodistribution by liquid-phase microextraction: Using a fatal diphenidol poisoning case.

Liquid-phase microextraction (LPME) possesses a high potential to isolate organic substances from different sample matrices. In this work, LPME was applied for the first time to investigate the biodistribution of diphenidol in different biofluids, organs, and brain regions using a fatal poisoning case. Since the LPME of diphenidol hasn't been reported, the effect of supported liquid membrane (SLM), acceptor and donor phases, and extraction time on LPME performance was investigated first. The solvents of 2-nonanone and 2-nitrophenyl octyl ether (NPOE) were found to be stable and efficient SLMs for LPME of diphenidol from biofluids and tissue samples, respectively. At steady state, the LPME recoveries for different sample matrices were in the range of 87 %-91 %. Due to the clean-up capability of LPME and the relatively high concentration of diphenidol in the fatal poisoning case, the proposed LPME systems were validated with related sample matrices using HPLC-UV for the determination. The methods displayed good linearity (R² ≥ 0.9943), and the limits of detection were 0.30 mg L-1, 0.28 mg L-1, and 2.7 µg g-1 for blood, urine, and liver samples, respectively. Meanwhile, the precision (≤13%), accuracy (90-110%), and matrices effect (±15%) were satisfactory at low, medium, and high concentrations. In addition, the stability, carryover, and dilution integrity met the requirements of ASB Standard 036. Finally, the proposed method was successfully applied to evaluate the biodistribution of diphenidol in five different biofluids, five organs, and six brain regions from a fatal poisoning case. Generally, the distribution of diphenidol in biofluids was lower than that in the organs and brain regions, and the highest concentration of diphenidol was observed in the liver, which is very important for the selection of inspection samples in forensic toxicological analysis. Therefore, LPME was proved to be a powerful tool for the investigation of biodistribution and postmortem redistribution in the fields of forensics.

Determination of aconitum alkaloids in acute poisoning case by electromembrane extraction.

In this work, electromembrane extraction (EME) was used for the first time to separate aconitine (AC), mesaconitine (Mes-AC) and hypaconitine (Hyp-AC) from biological samples and Chinese herbal medicines. Efficient EME of polar and high molecular weight aconitine alkaloids from different sample matrices was achieved with the solvent of 1-ethyl-2-nitrobenzene (ENB). Under the optimal EME conditions, EME provided recoveries for all targets in the range of 72%-74 %, 85%-103 % and 92%-94 % for whole blood, urine and aqueous samples. The proposed EME systems combined with LC-MS/MS and HPLC-UV were evaluated using different sample matrices, and the methods displayed satisfactory analytical characteristic including negligible matrix effect. The LOD and LOQ of AC, Mes-AC, and Hyp-AC by EME-LC-MS/MS were in the range of 0.002-0.068 ng/mL and 0.005-0.228 ng/mL respectively. The LOD and LOQ of AC, Mes-AC, and Hyp-AC by EME-HPLC-UV were in the range of 0.06-0.26 µg/mL and 0.20-0.86 µg/mL, respectively. The coefficient of determination, R2-value was ≥0.9926 for all cases, and the accuracy in the linear ranges was in the range of 91%-111 %. Finally, the method was successfully applied for the qualitative and quantitative analysis of AC and Mes-AC in the whole blood and herbal medicine dreg samples from an actual forensic case, and poisoning by aconitum alkaloids was identified as the cause of death. Therefore, we believe that EME could be a powerful tool to identify poisoning, and EME has great potential for efficient separation of polar and high molecular weight substances. These are of great importance in the fields of but not limited to forensic science, Traditional Chinese Medicine and clinics.

A novel indicator for lead poisoning beyond blood lead level: Facile diagnosis of lead poisoning using random urine with point-of-care testing.

Lead (Pb) poisoning is estimated to account for 1 % of the global disease burden. The gold standard for diagnosing lead poisoning in human body relies on blood lead level (BLL), which is always performed in hospitals using expensive instruments. However, there are still many countries and regions with a lack of medical resources (without enough professional medical staff and analytical instruments). To achieve a facile diagnosis of lead poisoning by ordinary residents (without any expertise), this study conducted a research study on 810 participants to discover and validate a new lead poisoning indicator (creatinine-corrected urinary lead level, cULL) beyond BLL in non-invasive samples. A point-of-care testing (POCT) device to measure cULL was developed, equipped with liquid-phase microextraction and electromembrane extraction on a paper-based analytical device for on-site separation of lead and creatinine in the urine, using a smartphone for the quantification of analytes. The cULL as a novel indicator and the POCT device developed could be effective in reducing the risk of damage from lead contamination.

Confined Gel-Electromembrane Extraction of Oligonucleotides.

Gel-electromembrane extraction (G-EME) is an increasingly popular green variant of electromembrane extraction (EME). However, the electroendosmosis (EEO) flow associated with G-EME greatly limits the development of this technology. To address this challenge, the current study proposed the concept of confined G-EME (CG-EME), and a three-dimensional-printed modular device was elaborately designed to realize this concept. The device blocked the EEO flow by limiting the volume of the sample compartment. Moreover, the mesh structure at the bottom of the extraction module helps to prepare thin and stable gel films, which enhance the electromigration driving force and shorten the migration path. In addition, polar oligonucleotides, a nucleic acid analyte, were extracted for the first time to prove the concept of CG-EME. After optimization, 62% of the oligonucleotides were extracted at 50 V voltage for 15 min using a 3 mm thick agarose (3%) gel film. Finally, the application capability of CG-EME was further demonstrated by recovering DNA primers and isolating disease biomarkers (miRNA-181b) from real samples. In combination with CG-EME and quantitative polymerase chain reaction (qPCR) analysis, the upregulation of miRNA-181b expression in the peripheral blood of patients with schizophrenia was observed. In conclusion, this study proposes CG-EME to diminish EEO and push EME into the clinical field to isolate nucleic acid biomarkers, which will greatly expand the application scenarios of this emerging technology.

Antifouling binary liquid-infused membranes for biological sample pretreatment.

Hydrophobic membranes infused with mixed solvents including a low polar solvent and a specific solvent can efficiently separate analytes from blood upon applying a voltage. In contrast, membranes infused with a specific solvent alone show significantly reduced separation efficiencies for blood samples. Infusion of a low polar solvent is of importance for achieving antifouling ability of membranes for biological sample pretreatment.

Comparison of the applicability of electromembrane extraction and liquid-phase microextraction for extraction of non-polar basic drugs from different biological samples: Using clozapine as the model analyte.

Understanding and comparing the applicability of electromembrane extraction (EME) and liquid-phase microextraction (LPME) is crucial for selecting an appropriate microextraction approach. In this work, EME and LPME based on supported liquid membranes were compared using biological samples, including whole blood, urine, saliva, and liver tissue. After optimization, efficient EME and LPME of clozapine from four biological samples were achieved. EME provided higher recovery and faster mass transfer for blood and liver tissue than LPME. These advantages were attributed to the electric field disrupting clozapine binding to interfering substances. For urine and saliva, EME demonstrated similar recoveries while achieving faster mass transfer rates. Finally, efficient EME and LPME were validated and evaluated combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The coefficient of determination of all methods was greater than 0.999, and all methods showed acceptable reproducibility (≤14%), accuracy (90%-110%), and matrix effect (85%-112%). For liver and blood with high viscosity and complex matrices, EME-LC-MS/MS provided better sensitivity than LPME-LC-MS/MS. The above results indicated that both EME and LPME could be used to isolate non-polar basic drugs from different biological samples, although EME demonstrated higher recovery rates for liver tissue and blood.

Molecularly imprinted polymers by reflux precipitation polymerization for selective solid-phase extraction of quinolone antibiotics from urine.

Molecularly imprinted polymers (MIPs) possess high specific cavities towards the template molecules, thus solid-phase extraction (SPE) based on MIPs using the target as the template has been widely used for selective extraction. However, the performance of SPE depends strongly on the shape and the distribution of the MIP sorbents, and rapid synthesis of MIPs with uniform particles remains a challenge. Our previous studies have shown that reflux precipitation polymerization (RPP) was a simple and rapid method for the synthesis of uniform MIPs. However, synthesis of MIPs by RPP for a group of targets using only one of the targets as the template has rarely been reported. In this work, MIPs with specific recognition capability for a group of quinolone antibiotics were synthesized for the first time via RPP with only ofloxacin as the template. The synthesized MIPs displayed good adsorption performance and selectivity (IF > 3.5) towards five quinolones, and subsequently were used as SPE adsorbents. Based on this MIPs-SPE, after systematic optimization of the SPE operation parameters during loading, washing and elution, an efficient and sensitive enough SPE method for separation and enrichment of the five quinolones in urine was developed and evaluated in combination with LC-MS/MS. The results showed that MIPs-SPE-LC-MS/MS has a good correlation (R2 ≥ 0.9961) in the linear range of 1-500 µg L-1. The limit of detection (LOD) and limit of quantification (LOQ) for the five quinolones were 0.10-0.14 µg L-1 and 0.32-0.48 µg L-1, respectively. In addition, the proposed method demonstrated good reproducibility (≤ 13 %) and high accuracy (92 %-113 %). We are confident that this method holds significant promise for the analysis of quinolones within the contexts of forensic medicine, epidemiology, and environmental chemistry.

Preparation of wax-based molecularly imprinted monolith for pipette-tip solid-phase extraction: a hybrid method.

The development of molecularly imprinted monolith (MIM) for pipette-tip solid-phase extraction (PT-SPE) for sample pretreatment is challenging . In this work, a wax-based molecularly imprinted monolith (WMIM) was successfully prepared with a hybrid method by integration of the traditional packing SPE column and MIM, including preparation of the salt column inside the pipette, polymerization of wax-based imprinted column (WIC) outside the pipette, and immobilization of WIC inside the pipette tip. To ensure the penetration of samples and solvents during the PT-SPE, micrometer-range interconnected macropores were tailor-made via the salt-template sacrifice method. For the production of high affinity imprinted sites within the WIC, octadecanoic acid was used as functional monomer in the paraffin matrix. In terms of the adsorption property, the synthesized WIC exhibited a specific affinity to cardiovascular drugs, with an imprinting factor (IF) of 4.8 for the target analyte. Moreover, the WMIM-based PT-SPE was coupled with fluorescence spectrophotometry for the target propranolol determination  (the excitation and emission wavelengths were 294 nm and 343 nm, respectively). This analytical method showed high recovery of target detection in different real samples (R > 90%), good sensitivity, and accuracy (R2 = 0.99, LOD = 0.03 ng mL-1). We believe this work could provide a significant contribution  for the fabrication of MIM and promote an emerging trend of developing elution-free materials for sample pretreatment.

Specific nanoantibiotics for selective removal of antibiotic-resistant bacteria: New insights in bacterial imprinting based on interfacial biomimetic mineralization.

Antibiotic resistance has been a worsening global concern and selective elimination of antibiotic-resistant bacteria (ARB) while retaining the co-existed beneficial bacteria has been essential in environmental protection, which having attracted considerable interest. In this work, by integrating the whole cell imprinting and epitope imprinting strategy, magnetic bacterial imprinted polymers (BIPs) towards ARB were synthesized with interfacial biomimetic mineralization followed by a screening process. The binding data showed that the BIPs owned highly specific affinity towards the target bacteria. Taking advantage of this specific binding ability of BIPs, a two-step selective antimicrobial approach was developed. Remarkably, the BIP nanoantibiotics (nAbts) could efficiently destroy ARB without harming the beneficial bacteria. In comparison with the non-bacterial imprinted polymers, the biocompatible BIP nAbts showed a 12.5-fold increase in the survival percentage for the beneficial bacteria in wastewater. To the best of our knowledge, this is the first time that bacterial imprinting via interfacial biomimetic mineralization was developed, and also the first report of killing ARB without harming the beneficial bacteria in wastewater. We believe that this strategy provides a new insight into the design of novel affinity materials for the selective elimination of ARB in biological treatment for environmental protection.

Synthesis of molecularly-imprinted polymers towards a group of amphetamine-type stimulants by reflux precipitation polymerization with a pseudo template.

Determination of amphetamine-type drugs (ATSs) in urine and wastewater is a simplified approach for the widespread monitoring of ATSs abuse. To improve the sensitivity of the analytical methods, molecularly imprinted polymers (MIPs) based solid-phase extraction (SPE) pretreatment attracted great attention in this field. Generally, smaller particle sizes and more uniform morphology of the MIPs could provide higher detection sensitivity. Our previous works showed reflux precipitation polymerization (RPP) is a method for synthesizing monodispersed MIPs with small particle size. However, synthesis of uniform spherical MIPs towards a group of targets has never been reported. Therefore, in the present work, MIPs towards a group of ATSs were synthesized via RPP with a pseudo template for the first time. After screening potential pseudo-templates, N-methylphenylethylamine (MPEA) was selected as the optimal pseudo-template. MPEA-MIPs were characterized by scanning electron microscope (SEM), FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS) spectra. Adsorption isotherms, adsorption kinetics and selectivity were evaluated, and the experimental results indicated that the MPEA-MIPs possessed good selectivity and adsorption property towards ATSs. After optimization of the MIP-SPE procedure, the MIP-SPE cartridges were then coupled with liquid chromatography and tandem mass spectrometry (LC-MS/MS) for determination of ATSs. The evaluation results showed that MIP-SPE-LC-MS/MS displayed good linearity (R2 >0.991) in the linear range (1.0-50.0 µg/L for urine and 0.5-50.0 µg/L for wastewater), and low matrix effect (85-112%). The limit of detection (LOD) was 0.05 -0.29 µg/L, and the accuracy (85-115%) and repeatability (RSD ≤ 15%) were satisfactory at low, medium and high concentrations. To the best of our knowledge, this is the first time that dummy MIPs towards a group of ATSs were synthesized by RPP polymerization, which showed great potential for the detection of ATSs in urine and wastewater.

Smartphone-controlled biosensor for viral respiratory infectious diseases: Screening and response.

Outbreaks of emerging viral respiratory infectious diseases (VRIDs) including coronavirus disease 2019 (COVID-19) seriously endanger people's health. However, the traditional nucleic acid detection required professionals and larger instruments and antigen-antibody detection suffered a long window period of target generation. To facilitate the VRIDs detection in time for common populations, a smartphone-controlled biosensor, which integrated sample preparation (electromembrane extraction), biomarker detection (red-green-blue model) and remote response technology (a built-in APP), was developed in this work. With the intelligent biosensor, VRIDs could be recognized in the early stage by using endogenous hydrogen sulfide as the biomarker. Importantly, it only took 15 min to accomplish the whole process of screening and response to VRIDs. Moreover, the experimental data showed that this smartphone-controlled biosensor was suitable for ordinary residents and could successfully differentiate non-communicable respiratory diseases from VRIDs. To the best of our knowledge, this is the first time that a smartphone-controlled biosensor for screening and response to VRIDs was reported. We believe that the present biosensor will help ordinary residents jointly deal with the challenges brought by COVID-19 or other VRIDs in the future.

Determination of total cathinones with a single molecularly imprinted fluorescent sensor assisted by electromembrane microextraction.

An electromembrane microextraction (EME)-assisted fluorescent molecularly imprinted polymer (MIP) sensing method is presented for detecting the total cathinone drugs in urine samples. In this detection system, the clean-up ability of EME eliminated the matrix effects on both target binding with MIPs and the luminescence of the fluorophore in the sensor. Moreover, by optimizing the extraction conditions of EME, different cathinone drugs with a same concentration show a same response on the single aggregation induced emission (AIE) based MIP (AIE-MIP) sensor (λex = 360 nm, λem = 467 nm). The recoveries were 57.9% for cathinone (CAT) and 78.2% for methcathinone (MCAT). The EME-assisted "light-up" AIE-MIP sensing method displayed excellent performance with a linear range of 2.0-12.0 µmol L-1 and a linear determination coefficient (R2) of 0.99. The limit of detection (LOD) value for EME-assisted "light-up" AIE-MIP sensing method was 0.3 µmol L-1. The relative standard deviation (RSD) values for the detection were found to be within the range 2.0-12.0%. To the best of our knowledge, this is the first time that determination of total illicit drugs with a single fluorescent MIP sensor was achieved and also the first utilization of sample preparation to tune the sensing signal of the sensor to be reported. We believe that this versatile combination of fluorescent MIP sensor and sample preparation can be used as a common protocol for sensing the total amount of a group of analytes in various fields.

Water-compatible Janus molecularly imprinted particles with mouth-like opening: Rapid removal of pharmaceuticals from hospital effluents.

Pharmaceuticals in hospital effluents, often discharged into the public sewage network without sufficient treatment, have shown negative impacts to the human health and aquatic environment. However, the conventional adsorbents used to remove these micropollutants had several deficiencies, including slow uptake kinetics and poor selectivity. To overcome these challenges, water-compatible Janus MIP particles (J-MIPs) with mouth-like openings were synthesized using seeded interfacial polymerization in this work. Among the series of J-MIPs, the selected J-MIP3 showed fast binding kinetics (∼40 s) towards the target pollutant. The theoretical and instrumental analysis suggested that the electrostatic interaction, hydrogen bond and hydrophobic reaction constituted the dominant mechanism for J-MIP3's recognition of target pharmaceutical. Selectivity and robustness tests indicated that the synthetic method was promising in practical application. Finally, the feasibility of the J-MIP3 fixed-bed column in the rapid removal of propranolol (PRO) from hospital effluents was successfully demonstrated. Compared to the activated carbon fixed-bed column, the J-MIP3 fixed-bed column showed at least 7-fold enhancement in its treatment efficiency. To the best of our knowledge, this is the first time that the accelerated mass transfer and fast removal of the pharmaceutical from wastewater have been achieved by the synthetic receptor with asymmetric structure. We believe the present study will open new avenues for the development of multi-functional molecularly imprinted polymers as well as Janus materials in environmental science.

Multi-extraction system with identical supported semi-liquid membrane: Enhanced stability for coextraction of acidic and basic drugs.

Coextraction of different groups of analytes is vital for saving sample volumes and simplifying analytical procedures in bioanalysis. Conventionally, coextraction was achieved by using multi-extraction systems with different supported liquid membranes (SLMs). However, the different membrane solvents tended to diffuse into the aqueous solutions and the other SLM to reach distribution equilibrium during extraction process, causing the system instability. In this work, a stable multi-extraction system (integration of liquid-phase microextraction and electromembrane extraction, LPME/EME) based on the identical supported semi-liquid membrane (SsLM) was developed. Principally, the state of distribution equilibrium of the membrane solvent (polypropylene glycol with molecular weight 4000) in SsLM could be reached at the beginning of extraction, which enhanced the coextraction stability. With this multi-extraction system, acidic and basic analytes were simultaneously extracted from practical biological samples. The extraction recoveries of the six model drugs in undiluted urine samples were over 70%. Followed by LC-MS/MS, the limits of quantification (LOQs) were in the range of 5-10 ng mL-1. The multi-extraction system using the identical SsLM in this study shows promising potential in construction of other stable multi-extraction systems (e.g., LPME/LPME and EME/EME) in the future, which will greatly benefit the group separation of analytes in complicated biological samples.

Specific "light-up" sensor made easy: An aggregation induced emission monomer for molecular imprinting.

Development of a specific "light-up" sensor for detection of psychoactive drug has been a great challenge in forensic analysis. To achieve this goal, an aggregation induced emission (AIE) functional monomer containing both phenylboronic group and double bond was synthesized for construction of molecularly imprinted polymers (MIPs) based fluorescent sensor. In this AIE-MIP sensor, the AIE fluorophore could vibrate freely in the absence of the target analyte (cathinone, CAT), while this vibration was restricted after the specific molecular recognition, leading to "light-up" character of the corresponding sensor. FT-IR and LC-MS characterizations proved the AIE monomer was successfully introduced onto AIE-MIPs. SEM analysis indicated the AIE-MIPs was ∼140 nm in diameter. Binding experiments indicated the AIE-MIPs owned high specificity towards CAT. Fluorescent studies confirmed that the "light-up" capability of the AIE-MIPs was highly selective. On this basis, the AIE-MIP sensor was applied in detecting CAT in forensic samples. The sensor reached a detection limit of 0.32 µmol L-1 and exhibited a linear range of 2-12 µmol L-1. Compared to previously reported MIPs based electrochemical sensors and fluorescent sensors for measurement of CAT drug and its analogue, the present AIE-MIP sensor showed much higher sensitivity. To the best of our knowledge, this is the first time that an AIE functional monomer was synthesized for molecular imprinting, and also the first "light-up" AIE-MIP sensor to be reported. We believe that this versatile design of the specific "light-up" sensor can be used as a general protocol for construction of advanced sensor in various fields.

Successive liquid-phase microextraction of acidic and basic analytes.

Practical biological and environmental samples always contain both acidic and basic substances, and the samples are always precious. Thus, separation of analytes with different nature from the same sample was of great significance. Successive liquid phase microextraction (sLPME) of acidic and basic analytes under optimal extraction conditions was therefore proposed for the first time. The concept of sLPME was proved by using three acidic analytes (naproxen, flurbiprofen and diclofenac) and three basic analytes (haloperidol, fluoxetine and sertraline) as model analytes, and using polypropylene glycol with an average molecular weight of 4000 (PPG4000) as SLM. The recoveries of all target analytes by sLPME were similar to that by individual LPME due to good affinity of PPG4000 to both acidic and basic analytes. Under optimal extraction conditions, the recoveries for all analytes by sLPME from urine samples were in the range of 62%-95%. Moreover, combined with LC-MS/MS, such sLPME approach was also evaluated with urine samples. The matrix effect of sLPME-LC-MS/MS at different levels for all analytes ranged from -14.1%-13.2%. The linear ranges with R2 > 0.996 were 5-1000 ng mL-1 for basic analytes, and 20-1000 ng mL-1 for acidic analytes except diclofenac (1-1000 ng mL-1). The repeatability and accuracy at four levels were in the range of 3%-10% and 86%-120%, respectively. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) were found to be 0.07-0.49 ng mL-1 and 0.25-1.63 ng mL-1, respectively. Finally, the strategy for constructing a sLPME system was further confirmed with urine, plasma and saliva using another two versatile SLM solvents possessing high affinity to both acidic and basic analytes. Successive LPME enabled separation of acidic and basic analytes from the same sample under optimum extraction conditions for all target analytes. Thus, we believe that the sLPME system will become a potent platform for forensic toxicology analysis, food science, environmental analysis and epidemiology study.

Sensitive determination of illicit drugs in wastewater using enrichment bag-based liquid-phase microextraction and liquid-chromatography tandem mass spectrometry.

To concentrate trace level of analytes in complex wastewater, sample preparation is necessary prior to instrumental analysis. In this work, an enrichment bag-based liquid-phase microextraction (EB-LPME) system was therefore proposed for the first time to isolate and enrich the illicit drugs (amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), ketamine, codeine and fentanyl) from wastewater. Under the optimum EB-LPME conditions, the recoveries of the model illicit drugs were 40-93% with enrichment factors up to 93. The optimized EB-LPME was compared to hollow fiber-LPME (HF-LPME) in terms of the thickness of the supported liquid membrane (SLM), the effective SLM area, extraction recovery and mass transfer flux. Compared with HF-LPME, EB-LPME possesses larger effective SLM area, and provided higher extraction recovery. In addition, EB-LPME provided larger mass transfer flux than HF-LPME, which was mainly due to the differences in SLM thickness. Therefore, SLM thickness was identified as the main mass transfer flux-determining factor experimentally. The matrix effect of EB-LPME was evaluated using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and excellent sample clean-up was confirmed. Subsequently, EB-LPME-LC-MS/MS was validated with satisfactory results, and the detection of limit of the proposed method was in the range of 0.3-8.7 ng/L. Finally, with standard addition method, EB-LPME-LC-MS/MS was successfully applied for the determination of the model drugs in a local hospital wastewater from Wuhan, China. This study clearly showed that EB-LPME displayed great potential as an efficient sample preparation method for isolation and enrichment of the drugs/pollutants from complex environmental samples for wastewater-based epidemiology in the near future.

Effect of sample matrices on supported liquid membrane: Efficient electromembrane extraction of cathinones from biological samples.

In this work, the effect of sample matrix on electromembrane extraction (EME) was investigated for the first time using cathinones (log P < 1.0) as polar basic model analytes. Ten supported liquid membranes (SLMs) were tested for EME from spiked buffer solutions, urine, and whole blood samples, respectively. For buffer solutions, SLMs containing aromatic solvents provided higher EME recovery than non-aromatic solvents, which confirmed the significance of cation-π interactions for EME of basic substances. Interestingly, when applied to urine and whole blood samples, aromatic SLMs were less efficient, while non-aromatic SLMs containing abundant hydrogen-bond acidity/basicity were efficient. These observations were explained by SLM fouling, and the antifouling property of the SLM was clearly dependent on the nature of the SLM solvent. Accordingly, a binary SLM containing aromatic 1-ethyl-2-nitrobenzene (ENB) and non-aromatic 1-undecanol (1:1 v/v) was developed. This binary SLM was not prone to fouling, and provided high recoveries of cathinones from urine and whole blood. EME based on this SLM was optimized and evaluated in combination with liquid chromatography tandem mass spectrometry (LC-MS/MS), and the linear ranges with R2 ≥ 0.9903 for cathinones in whole blood and urine were 5-200 ng/mL and 1-200 ng/mL, respectively. The LOD and LOQ of cathinones were ranged from 0.12 to 0.54 ng/mL and 0.38-1.78 ng/mL, respectively. The repeatability and accuracy bias at three levels were ≤11% and within 10%, respectively. In addition, the matrix effect ranged from 88% to 118% was also in compliance with guidelines for bioanalytical method validation provided by the European Medicines Agency.

Ultrasound-assisted electromembrane extraction with supported semi-liquid membrane.

Electromembrane extraction (EME), involving the migration of charged analytes across a supported liquid membrane (SLM) with an external power supply, is a promising sample preparation method in analytical chemistry. However, the presence of boundary double layers at the SLM/solution interfaces often restricts extraction efficiency. To avoid this, the current work proposed an ultrasound-assisted EME (UA-EME) method based on a novel type of supported semi-liquid membrane (SsLM). The characterizations showed that the SsLM was stable under ultrasound conditions. Ultrasound was found to reduce the boundary double layers and thus increase the mass transfer. Major operational parameters in UA-EME including ultrasound power density, temperature, applied voltage and extraction time were optimized with haloperidol, fluoxetine, and sertraline as model analytes. Under the optimal conditions, extraction recoveries of model analytes in water samples were in the range of 66.8%-91.6%. When this UA-EME method was coupled with LC-MS/MS for detection of the target analytes in human urine samples, the linear range of the analytical method was 10-1000 ng mL-1, with R2 > 0.997 for all analytes. The limits of detection (LOD) and limits of quantification (LOQ) were in the range of 1.7-2.1 ng mL-1 and 5.7-6.7 ng mL-1, respectively. The UA-EME expands the application field of ultrasound chemistry and will be very important in development of stable and fast sample preparation systems in the future.