13,140 research outputs found
Separating the wheat from the chaff: a prioritisation pipeline for the analysis of metabolomics datasets
No full textLiquid Chromatography Mass Spectrometry (LC-MS) is a powerful and widely applied method for the study of biological systems, biomarker discovery and pharmacological interventions. LC-MS measurements are, however, significantly complicated by several technical challenges, including: (1) ionisation suppression/enhancement, disturbing the correct quantification of analytes, and (2) the detection of large amounts of separate derivative ions, increasing the complexity of the spectra, but not their information content. Here we introduce an experimental and analytical strategy that leads to robust metabolome profiles in the face of these challenges. Our method is based on rigorous filtering of the measured signals based on a series of sample dilutions. Such data sets have the additional characteristic that they allow a more robust assessment of detection signal quality for each metabolite. Using our method, almost 80% of the recorded signals can be discarded as uninformative, while important information is retained. As a consequence, we obtain a broader understanding of the information content of our analyses and a better assessment of the metabolites detected in the analyzed data sets. We illustrate the applicability of this method using standard mixtures, as well as cell extracts from bacterial samples. It is evident that this method can be applied in many types of LC-MS analyses and more specifically in untargeted metabolomics
Ms. Courtney Chartier, RWWL AUC, August 2011
No full textThis video is a conversation with Ms. Courtney Chartier. Ms. Chartier talks about her work on the "New Georgia Encyclopedia" and "Online Voter Education Project." Andrea Jackson, AUC Woodruff Library, is the interviewer
Ms. Neely Terrell, RWWL AUC, March 2012
No full textThis video is a conversation with Ms. Neely Terrell. Ms. Terrell talks about her book, "Super Singles Activate". Anthony Kinsey and Jahnesta Horney, AUC Woodruff Library, are the interviewers
Simultaneous pre-concentration and HPLC-MS/MS quantification of phycotoxins and cyanotoxins in inland and coastal waters
No full textThe purpose of this study was to set up a sensitive method for the simultaneous determination of phycotoxins and cyanotoxins—Emerging pollutants with different structures and harmful properties (hepatotoxicity, neurotoxicity and cytotoxicity)—In environmental waters. Due to the low concentrations detected in these samples, a pre-concentration step is required and here it was performed in a single step with a commercial cartridge (StrataTM-X), achieving enrichment factors up to 200 and satisfactory recovery (R = 70–118%) in different aqueous matrices. After solid-phase extraction (SPE), toxins were separated and quantified by High Performance Liquid Chromatography-Heated ElectroSpray Ionisation Tandem Mass Spectrometry (HPLC-HESI-MS/MS) in Multiple Reaction Monitoring (MRM) mode. An analytical evaluation of the proposed method was done based on the analytical figures of merit, such as precision and trueness, linearity, selectivity, and sensitivity, and it turned out to be a robust tool for the quantification of ng L−1 levels, phycotoxins and cyanotoxins in both freshwater and saltwater samples
Ms. Felesha Love, Spelman College, January 2016
No full textThis video is a conversation with Felesha Love. Ms. Love talks about her book, "Brave Leap to Freedom: Integrating Mind, Body, and Spirit to Cultivate Healthy Relationships". Jordan Moore, AUC Woodruff Library, is the interviewer
HPLC-MS/MS multiclass determination of steroid hormones in environmental waters after preconcentration on the carbonaceous sorbent HA-C@silica
No full textIn this study, a sensitive and multiclass method has been developed for analysis of three families of steroid hormones, i.e. progestins, oestrogens, androgens, by SPE-HPLC-ESI-MS/MS. The extraction efficiency of thermally condensed humic acids onto silica sorbent (HA-C@silica), here for the first time studied for multiclass enrichment of these sex hormones, was tested in different environmental waters (tap and river water, urban wastewater treatment plant effluent) spiked at the nanograms per litre levels (5–1000 ng L−1). Quantitative adsorption was achieved using 200 mg sorbent for preconcentration of 250–1000 mL sample, at the native pH (pH = 6.5–7.7). Elution was performed by two sequential fractions (methanol followed by acetonitrile), obtaining in all the matrices investigated satisfactory recoveries (71% to 124% for river waters and 71–113% for urban wastewater treatment plant effluent) and RSDs below 15% (n = 3). The high enrichment factors (up to 4000) coupled with high-performance liquid chromatography tandem mass spectrometry quantification (MRM mode) provided low limits of detection and quantification (a few ng L−1), that are suitable for environmental monitoring. Most of the analytes were detected in river water and in wastewater effluent samples (in the ng L−1 concentration range), attesting their environmental diffusion. The proposed method was extended to a fourth class, Glucocorticoids, achieving good results in river samples, by the same SPE cartridge and chromatographic run
Green and Efficient Determination of Fluoroquinolone Residues in Edible Green Fruits and Leafy Vegetables by Ultrasound-Assisted Extraction Followed by HPLC-MS/MS
No full textIn this work, a simple, quick and efficient analytical method for determination of human and veterinary fluoroquinolone antimicrobial residues in lettuce, cucumber and spinach is developed. The procedure entails a 6 min ultrasound-assisted extraction (UAE, 3 x 2 min) in an alkaline (2% v/v NH3) aqueous solution containing Mg2+ ions (3 x 6 mL), with no need for organic solvents. The extract is submitted to cleanup on the HLB (TM) cartridge and the fluoroquinolones are separated and quantified by HPLC-MS/MS in a 10 min chromatographic run, using a small amount of acetonitrile in the mobile phase. The method, entirely developed in real matrices, is validated according to the updated analytical guidelines and provided suitable recoveries in the range of 67-116% and precision (RSD <= 20%, n = 3) at different concentrations (15, 70 and 150 ng g(-1)), with method quantification limits of 2-10 ng g(-1). Fluoroquinolones were detected and quantified at concentrations from few to hundreds of nanograms per gram in vegetables from supermarkets, demonstrating the applicability of the method for monitoring residues of these pharmaceuticals
Corticosterone administration to rat pups, but not maternal separation, affects sexual maturation and glucocorticoid receptor immunoreactivity in the testis
No full textPrenatal stress strongly affects sexual dimorphism of male rats. Much less information is instead available on the effects of postnatal stress on sexual maturation during the so-called stress hyporesponsive period (SHRP). For this reason, we compared corticosterone-treated (CS; 10 mg/kg sc, suspended in sesame oil) or maternally separated pups (MS; 5 h/day in the first week of life) with control rats. Control and MS PUPS also received sesame oil injections. The effects of these procedures on physical development (body weight and eye opening), sexual maturation [anogenital distance, testis weight, 3beta-hydroxysteroid dehydrogenase/(Delta5-4) (3betaHSD) isomerase activity and time to testis descent] and glucocorticoid receptor (GR) immunoreactivity in the testis were examined. Corticosterone treatment significantly (P<.05) advanced testis descent and increased testis weight and 3betaHSD activity at puberty. In addition, adult CS rats presented higher levels of GR inummoreactivity in testicular tubules when compared to control and MS rats. No differences were found between control and MS rats. On this basis, we propose that the silencing of adrenocortical function during the SHRP could be finalized to preserve sexual maturation from the influence of glucocorticoid effects. As SHRP is unique to rodents, this phenomenon could be related to their successful reproductive strategy. (C) 2002 Elsevier Science Inc. All rights reserved
HA-C@silica sorbent for simultaneous extraction and clean-up of steroids in human plasma followed by HPLC-MS/MS multiclass determination
No full textAim and novelty of this work are the development of a simple and straightforward analytical procedure for multiclass determination of steroid hormones in human plasma. The method entails a single pre-treatment step based on solid-phase extraction using a recently proposed sorbent phase (HA-C@silica). This is easily prepared with good reproducibility via pyrolysis of humic acids onto silica, and not yet tested in biological fluids. It proved to be advantageous as it showed poor affinity for the protein matrix constituents while quantitatively extracting and pre-concentrating the target analytes. Indeed, as demonstrated in bovine serum albumin solution, up to ca. 90% protein is not retained by the sorbent, similarly to the behaviour of restricted access carbon nanotubes, tested for comparison. The high albumin exclusion allowed a satisfactory clean-up avoiding protein precipitation and centrifugation before extraction. The extraction procedure, optimized by a chemometric approach (23 experimental design) in BSA solution, provided quantitative recovery (76–119%, n = 3) for all steroids working with 1:8-diluted plasma (2 mL) and 100 mg HA-C@silica. Before analytes elution by 1 mL methanol-acetonitrile (1:1, v/v), selective washings (2% v/v formic acid and 30% v/v methanol) were applied to remove the small fraction of retained proteins, thus obtaining very clean SPE extracts to be analyzed by HPLC-ESI-MS/MS. This allowed identification/quantification (MRM mode) at few ng mL−1 by a single chromatographic run. The procedure was verified in blank-certified foetal bovine serum (spikes 10–100 ng mL−1), obtaining good recovery and suitable inter-day precision (RSDs < 15%, n = 3). The analytical method, applied to real plasma samples analysis, is appealing in terms of sample throughput, extraction efficiency and clean-up
In-vial polycaprolactone thin film for sampling and microextraction of sexual hormones in environmental waters and wastewaters followed by HPLC-MS/MS
No full textBackground: The sustainability of sample treatments is a hot topic that can be addressed focusing on miniaturization of techniques and design of more efficient and sustainable sorbents. In such scenario, in-vial microextraction is increasingly reported as a reliable alternative to other solid-phase extraction setups, as integrates sampling, adsorption and desorption in a single device before instrumental analysis. Polymeric thin films have proven to be a versatile and efficient material for microextraction processes, but more attention has to be paid to the preparation steps both in terms of nature of polymer and possible co-extractant, and of solvents applied during the solubilization process.
Results: An in vial-microextraction device for sex hormones was fabricated using as the extractant a thin film
made of a biodegradable polymer (polycaprolactone, PCL) directly formed on the bottom wall of a glass vial. The
greenness assessment of the film preparation results in the selection of an environmentally friendly solvent
(methyl-tetrahydrofuran) for PCL solubilization. After evaluation of key parameters (contact time, desorption
solvent and conditions), efficient adsorption-desorption cycle is completed in 30 min. High simplicity, low
sample manipulation (two steps), quantitative adsorption and recovery (EE% > 70; R% > 60 for most analytes,
respectively) determined by HPLC- MS/MS greatly improve sample throughput and the greenness of the method
(0.66 by AGREEprep and 7.58 by SPMS). The method was successfully validated in actual water samples, showing low limits of detection (2–35 ng/L), satisfactory linearity (0.5–50 μg/L), and limited matrix effects (<10 % for river and <25 % for wastewater).
Significance:
This polycaprolactone film proved to be a biodegradable and sustainable sorbent towards sex hormones. Its applicability in the in-vial thin film microextraction ensures the whole sample treatment in the same vial with high throughput, low energy and solvent consumption, keeping unchanged performance for multiple cycles. The method combines a green sample treatment with accurate detection and high sensitivity by HPLC-MS/MS, representing significant progress in miniaturized devices for environmental scope
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