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The current work describes the implementation of electro membrane extraction (EME) into an autosampler for high-throughput analysis of samples by EME-LC-MS. The extraction probe was built into a luer lock adapter connected to a HTC PAL autosampler syringe. As the autosampler drew sample solution, analytes were extracted into the lumen of the extraction probe and transferred to a LC-MS system for further analysis. Various parameters affecting extraction efficacy were investigated including syringe fill strokes, syringe pull up volume, pull up delay and volume in the sample vial. The system was optimized for soft extraction of analytes and high sample throughput. Further, it was demonstrated that by flushing the EME-syringe with acidic wash buffer and reverting the applied electric potential, carry-over between samples can be reduced to below 1%. Performance of the system was characterized (RSD, <10%; R2, 0.994) and finally, the EME-autosampler was used to analyze in vitro conversion of methadone into its main metabolite by rat liver microsomes and for demonstrating the potential of known CYP3A4 inhibitors to prevent metabolism of methadone. By making use of the high extraction speed of EME, a complete analytical workflow of purification, separation, and analysis of sample could be achieved within only 5.5 min. With the developed system large sequences of samples could be analyzed in a completely automated manner. This high degree of automation makes the developed EME-autosampler a powerful tool for a wide range of applications where high-throughput extractions are required before sample analysis. [ABSTRACT FROM AUTHOR]

Monitoring brassinosteroids (BRs) has been of major interest of researchers as these substances play a crucial role in a variety of phytological processes in plants. However, the determination of endogenous BRs in plant tissue is still a challenging task due to their low abundance and the complex matrix of plant tissues. In this study, a single step strategy by combining tip extraction and in situ derivatization was proposed for BR analysis. In the proposed strategy, a mixed mode sorbent (C8-SO3H) in tip was modified with 4-phenylaminomethylbenzeneboric acid (4-PAMBA) through cation exchange and hydrophobic interactions, and then used as a boronate affinity media to selectively capture and purify BRs from plant extract through the reaction of boric acid groups of 4-PAMBA and cis-diol on BRs. The BRs-4-PAMBA derivatives formed were easily eluted from the C8-SO3H tip by nullifying the ion exchange and hydrophobic interactions using ammonia acetonitrile, followed by LC-MS/MS analysis. BR standards, isotopically labeled with dS-4-phenylaminomethyl-benzeneboric acid (4-PAMBA-dS) were introduced to improve the assay precision of LC-MS/MS. Under the optimized conditions, the overall process could be completed within 1 h, which is greatly improved in speed compared with previously reported protocols. In addition, the detection sensitivities of labeled BRs were improved by over 2000-fold compared with unlabeled BRs, thus the consumption of plant materials was reduced to 50 mg. Finally, the proposed method was applied for the investigation of BRs response in rice toward Cd stress. [ABSTRACT FROM AUTHOR]

A simple to construct and operate, "dip-in" electromembrane extraction (EME) probe directly coupled to electrospray ionization-mass spectrometry (ESI-MS) for rapid extraction and real time analysis of various analytes was developed. The setup demonstrated that EME-MS can be used as a viable alternative to conventional protein precipitation followed by liquid chromatography–mass spectrometry (LC–MS) for studying drug metabolism. Comparison of EME-MS with LC–MS for drug metabolism analysis demonstrated for the first time that real time extraction of analytes by EME is possible. Metabolism kinetics were investigated for three different drugs: amitriptyline, promethazine, and methadone. By comparing the EME-MS extraction profiles of the drug substances and formed drug metabolites with the metabolism profiles obtained by conventional protein precipitation followed by LC–MS good correlation was obtained with only very limited time delay in the extraction. The results indicate that, by tuning the electromembrane properties, for example, by optimizing the extraction voltage, extremely fast extraction kinetics can be obtained. A metabolic profile could be generated while the drug was metabolized offering a significant time saving as compared to conventional LC–MS where laborious protein precipitation or other sample pretreatments are required before analysis. This makes the developed EME-MS setup a highly promising sample preparation method for various kinds of applications where fast and real-time analysis of analytes is of interest. [ABSTRACT FROM AUTHOR]

An automated analyte electroextraction and preconcentration system, which was used as the front end for a liquid chromatography-electrospray mass spectrometry instrument, is described. The extraction was based on driving the anionic analytes across a polymer inclusion membrane by application of a potential of 200 V to the cell. Five milliliters (5 mL) of sample were passed through a flow-through cell at a flow rate of 0.2 mL/min containing a membrane 20 μm thick. This consisted of 75% cellulose triacetate as base polymer, 12.5% of tris(2-ethylhexyl)phosphate as plasticizer, and 12.5% of Aliquat 336 as cationic carrier. The target analytes were enriched in 20 μL of a stagnant acceptor solution prior to online LC/MS analysis. The performance of the system was demonstrated for the determination of chlorinated phenoxyacetic acid herbicides in spiked river water. Enrichment factors of ~200 were achieved with recoveries of typically 99% and precision values of typically 5%. The limit of detection (LOD) values were found to be between 0.03 ng/mL to 0.08 ng/mL. [ABSTRACT FROM AUTHOR]

Exploratory or untargeted ultra performance liquid chromatography--mass spectrometry (UPLC-MS) profiling offers an overview of the complex lipid species diversity present in blood plasma. Here, we evaluate and compare eight sample preparation protocols for optimized blood plasma lipid extraction and measurement by UPLC-MS lipid profiling, including four protein precipitation methods (i.e., methanol, acetonitrile, isopropanol, and isopropanol- acetonitrile) and four liquid-liquid extractions (be., methanol combined with chloroform, dichloromethane, and methyl-ferf butyl ether and isopropanol with hexane). The eight methods were then benchmarked using a set of qualitative and quantitative criteria selected to warrant compliance with high-throughput analytical workflows: protein removal efficiency, selectivity, repeatability, and recovery efficiency of the sample preparation. We found that protein removal was more efficient by precipitation (99%) than extraction (95%). Additionally, isopropanol appeared to be the most straightforward and robust solvent (61.1% of features with coefficient of variation (CV) < 20%) while enabling a broad coverage and recovery of plasma lipid species. These results demonstrate that isopropanol precipitation is an excellent sample preparation procedure for high-throughput untargeted lipid profiling using UPLC-MS. Isopropanol precipitation is not limited to untargeted profiling and could also be of interest for targeted UPLC-MS/MS lipid analysis. Collectively, these data show that lipid profiling greatly benefits from an isopropanol precipitation in terms of simplicity, protein removal efficiency, repeatability, lipid recovery, and coverage. [ABSTRACT FROM AUTHOR]

MALDI imaging mass spectrometry (MALDI-IMS) has become a powerful tool for localizing both small molecules and intact proteins in a wide variety of tissue samples in both normal and diseased states. Identification of imaged signals in MALDI-IMS remains a bottleneck in the analysis and limits the interpretation of underlying biology of tissue specimens. In this work, spatially directed tissue microextraction of intact proteins followed by LC-MS/MS with electron transfer dissociation (ETD) was used to identify proteins from specific locations in three tissue types; ocular lens, brain, and kidney. Detection limits were such that a 1 μL extraction volume was sufficient to deliver proteins to the LC-MS/MS instrumentation with sufficient sensitivity to detect 50-100 proteins in a single experiment. Additionally, multiple modified proteins were identified; including truncated lens proteins that would be difficult to assign to an imaged mass using a bottom-up approach. Protein separation and identification are expected to improve with advances in intact protein fractionation/chromatography and advances in interpretation algorithms leading to increased depth of proteome coverage from distinct tissue locations. [ABSTRACT FROM AUTHOR]

Heterocyclic amines (HCAs) are mutagenic/carcinogeniccompoundsformed at ng/g levels during frying meat or fish. The effect of thenormal intake of dietary HCAs in humans and their involvement in theetiology of cancer are currently unknown. In this work, a new extractionmethod, liquid phase microextraction (LPME) with hollow fibers, andLC-MS/MS have been used for the first time to determine HCAs and metabolitesin nonspiked human urine following a single meal of chicken cookedat 180 °C for 6 min. The total intake of HCAs was estimated tobe 6 μg, of which 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) accounted for about 1 μg. The concentrationsof PhIP in nonhydrolyzed urine samples ranged from 11.7 to 59.4 pg/g.The total amount of PhIP in urine ranged between 9.3 and 21.1 ng,which corresponds to 0.91–2.1% of the ingested PhIP. In addition,the urine levels of 4′-OH-PhIP (2-amino-1-methyl-6-(4′-hydroxy)phenylimidazo[4,5-b]pyridine) and 5-OH-PhIP (2-amino-1-methyl-6-(5-hydroxy)phenylimidazo[4,5-b]pyridine) also showed a narrow variation between the samples.The analysis of urine samples after acid hydrolysis did not give additionalinformation but showed a notable increase in norharman in some cases.The obtained results suggest PhIP in urine as a possible biomarkerof exposure to HCAs and the LPME and LC-MS/MS method as an appropriatestrategy to biomonitor HCAs in urine. [ABSTRACT FROM AUTHOR]