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Matrix Interferences (matrix + interference)

Distribution by Scientific Domains

Chemistry	62%

Selected Abstracts

Reducing glycerophosphocholine lipid matrix interference effects in biological fluid assays by using high-turbulence liquid chromatography

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2008
Lihong Du
Matrix interferences can severely affect quantitative assays of biological samples when electrospray ionization (ESI) is employed with liquid chromatography/tandem mass spectrometry (LC/MS/MS). A major source of matrix interferences for plasma sample analyses is the presence of glycerophosphocholine (GPCho) lipids. The efficiency of online high-turbulence liquid chromatography (HTLC) extraction for eliminating these lipids is evaluated and the interfering effects of endogenous lipids on human plasma assays are measured for pharmaceutical compounds having a wide variety of chemical properties. It is found that GPCho lipids, represented by 16:0, 18:1 and 18:0 LPC (lysophosphatidylcholine) and 16:0-18:2 PC, cause variations for hydrophobic compound analyses even when optimal online HTLC extraction conditions are employed. The efficiency for lipid removal depends on the organic content of the transfer solvent, but turbulent flow loading has no significant effect. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Detection of nodularin in flounders and cod from the Baltic Sea

ENVIRONMENTAL TOXICOLOGY, Issue 2 2001
Vesa Sipiä
Abstract The brackish water cyanobacterium Nodularia spumigena regularly forms waterblooms in the Baltic Sea. Many N. spumigena strains can produce nodularin, a hepatotoxic penta-peptide, which has caused several animal poisonings in the Baltic Sea area. To improve our understanding of nodularin bioaccumulation in aquatic organisms this study measured nodularin in flounder and cod caught from the Baltic Sea. Flounders were collected from the western Gulf of Finland in July 1996, September 1997, and September 1998, and from the Gulf of Bothnia in August 1997 and September 1998. Flounders were also collected from the coastal areas of Sweden in the Baltic Proper during September 1998. Cod were caught from the southern Baltic Sea in August 1998. Livers and muscles of the 1997 fish were isolated, extracted, and analysed for nodularin using high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA) and protein phosphatase 1 (PP1) inhibition assay. Approximately 30,70 ng of nodularin/g dry weight (maximum value 140 ng/g) were found in the liver tissue samples by ELISA and PP1 inhibition. These concentrations were below the detection limit of HPLC. PP1 assay showed inhibition also in muscle samples, but this may due to other compounds present in the muscle extracts rather than NODLN or due to matrix interference. The recovery of nodularin from liver tissue with ELISA and PP1 assays was about 30%. Nodularin concentrations in samples are not corrected for recovery. Although the concentrations of nodularin found in this study are low further studies of nodularin are needed to assess possible bioaccumulation in brackish water food webs. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 121,126, 2001 [source]

Porous silicon surfaces for metabonomics: Detection and identification of nucleotides without matrix interference

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007
D. Gómez
Abstract In present work, porous silicon surfaces (PSS) have been developed for time of flight mass spectrometric experiments (TOF-MS) in the monitoring of nucleotides, commonly found as metabolites in the cell. The mass range of the studied molecules (, 400 amu) is common to several important messengers and other metabolites. Different porosified surfaces have been developed by means of electrochemical etching and different degree of porosity and pore size achieved as function of silicon dopant concentration, silicon resistivity, current density and the presence or absence of illumination along the process. As main conclusion, it can be said that an interesting commercial nucleotide (Cyclic adenosine monophosphate, c-AMP) has been detected on low concentrations (,hundreds of femtomols) for some of the fabricated porous surfaces. Taking into account that these concentrations are similar to the ones found in real samples, this result opens the possibility to the fabrication of DIOS (Desorption Ionization On Silicon) chips for the detection of nucleotides in biological fluids. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A New Indirect Electroanalytical Method to Monitor the Contamination of Natural Waters with 4-Nitrophenol Using Multiwall Carbon Nanotubes

ELECTROANALYSIS, Issue 9 2009
Cruz Moraes, Fernando
Abstract The electrochemical detection of the hazardous pollutant 4-nitrophenol (4-NP) at low potentials, in order to avoid matrix interferences, is an important research challenge. This study describes the development, electrochemical characterization and utilization of a multiwall carbon nanotube (MWCNT) film electrode for the quantitative determination of 4-NP in natural water. Electrochemical impedance spectroscopy measurements showed that the modified surface exhibits a decrease of ca. 13 times in the charge transfer resistance when compared with a bare glassy carbon (GC) surface. Voltammetric experiments showed the possibility to oxidize a hydroxylamine layer (produced by the electrochemical reduction of 4-NP on the GC/MWNCT surface) in a potential region which is approximately 700,mV less positive than that needed to oxidize 4-NP, thus minimizing the interference of matrix components. The limit of detection for 4-NP obtained using square-wave voltammetry (0.12,,mol L,1) was lower than the value advised by EPA. A natural water sample from a dam located in São Carlos (Brazil) was spiked with 4-NP and analyzed by the standard addition method using the GC/MWCNT electrode, without any further purification step. The recovery procedure yielded a value of 96.5% for such sample, thus confirming the suitability of the developed method to determine 4-NP in natural water samples. The electrochemical determination was compared with that obtained by HPLC with UV-vis detection. [source]

Ultra-trace analysis of multiple endocrine-disrupting chemicals in municipal and bleached kraft mill effluents using gas chromatography,high-resolution mass spectrometry

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2008
Michael G. Ikonomou
Abstract A comprehensive gas chromatographic,high-resolution mass spectrometric (GC-HRMS),based method was developed that permitted the simultaneous determination of 30 estrogenic endocrine-disrupting chemicals (EDCs) and related compounds, including surfactants, biogenic and synthetic steroids, fecal sterols, phytoestrogens, and plasticizers, in wastewater. Features of the method include low sample volume (,40 ml), optimized Florisil® cleanup to minimize matrix interferences and optimized analyte derivatization to improve sensitivity via GC-HRMS. Detection limits were in the low- to mid-ng/L range, and recoveries were greater than 60% for most target analytes. This new method allows for high throughput analysis of many organic wastewater contaminants in a complex matrix with relative standard deviation of less than 15% for most measurable compounds. The applicability of the method was demonstrated by examining wastewater samples from different origins. Compounds such as di(2-ethylhex-yl)phthalate, cholesterol, cholestanol, and other cholesterol derivatives were measured in much higher concentrations in untreated sewage and were reduced substantially in concentration by the treatment process. However, steroidal compounds, particularly estrone (E1), 17,-estradiol (E2), and estriol (E3), as well as plant sterols (except stigmastanol), were greater in the treated municipal wastewater versus the untreated effluent. Plant and fungi sterols, stigmastanol and ergosterol, were found largely associated with bleached kraft mill effluent (BKME) as compared to the municipal effluents. [source]

Continuous mode of operation for large volume dosing in analytical carrier ampholyte-free isoelectric focusing of proteins applied to off-line detection of fractions

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2006
Jana Budilová
Abstract Mass spectrometry is being increasingly used for analysis of proteome complex samples. Sample preparation is often necessary to remove matrix interferences and to concentrate analytes prior to MS measurement. A useful method for this purpose is Carrier Ampholyte Free-Isoelectric Focusing (CAF-IEF). In this paper CAF-IEF of ampholytes was performed on a commercial apparatus EA101 (Villa Labeco, Slovakia) equipped with a specially made column for samples of large volume (up to 0.5 mL). A new continuous mode without voltage interruption or electrolyte replacement was developed. In this mode, a low molecular mass pI marker (PIM 7.4) and low concentrations of myoglobin and insulin (16 mg/L), respectively, were concentrated, and then 5-,L fractions collected for off-line analyses. The total time of focusing was 66 minutes. The concentration of PIM 7.4 in the fractions was increased up to 75 times (determined by UV-VIS spectrometry). The concentration in the fractions was increased up to 30 times for myoglobin and 10 times for insulin. [source]

Reducing glycerophosphocholine lipid matrix interference effects in biological fluid assays by using high-turbulence liquid chromatography

Determination of abamectin in soil samples using high-performance liquid chromatography with tandem mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2004
Bobby N. Brewer
Abamectin, which is comprised of a mixture of avermectins B1a and B1b, is a natural pesticide used as an anti-parasitic agent in livestock, ornamental, and agricultural crops, which can potentially be transported to aquatic systems. These compounds are highly toxic to both aquatic vertebrates and invertebrates at low concentrations in water. This investigation developed high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) techniques to support automated extraction by an accelerated solvent extraction (ASE®) system and chromatographic techniques to measure residues of avermectins in complex soil samples. HPLC along with atmospheric pressure chemical ionization (APCI) MS/MS was used for separation and determination of avermectin isomers in soil samples. Average method recovery for abamectin by UV was 91%, while detection by MS/MS resulted in a 68% recovery for abamectin. Individual method recoveries by MS/MS were 53.6% for avermectin B1a and 36.8% for avermectin B1b. The use of tandem technology eliminated matrix interferences and resulted in an approximately eight-fold increase in sensitivity. Copyright © 2004 John Wiley & Sons, Ltd. [source]