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PubMed2004

Simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by slurry-sampling graphite furnace AAS.

A fast and accurate analytical method was established for the simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by graphite furnace atomic absorption spectrometry using a slurry sampling technique and a Hitachi Model Z-9000 atomic absorption spectrometer. The slurry samples were prepared by the ultrasonication of silicon carbide or silicon nitride powders with 0.1 M nitric acid. Calibration curves were prepared by using a mixed standard solution containing aluminum, calcium, iron and 0.1 M nitric acid. The analytical results of the proposed method for aluminum, calcium and iron in silicon carbide and silicon nitride reference materials were in good agreement with the reference values. The detection limits for aluminum, calcium and iron were 0.6 microg/g, 0.15 microg/g and 2.5 microg/g, respectively, in solid samples, when 200 mg of powdered samples were suspended in 20 ml of 0.1 M nitric acid and a 10 microl portion of the slurry sample was then measured. The relative standard deviation of the determination of aluminum, calcium and iron was 5 - 33%.

Journal Article↗

PubMed1993

Determination of salmeterol in rat and dog plasma by high-performance liquid chromatography with fluorescence detection.

Salmeterol (as the hydroxynaphthoate) is the first of a new class of long-acting beta-adrenergic receptor agonists with both bronchodilator and anti-inflammatory actions. A sensitive, accurate, and precise high-performance liquid chromatographic method for the determination of salmeterol in rat and dog plasma is described. Samples are prepared by solid-phase extraction and, after chromatography of the extracts on a reversed-phase styrene/divinylbenzene analytical column, salmeterol is detected by fluorescence monitoring (excitation wavelength, 230 nm; emission wavelength, 305 nm). The method is sensitive to 1 ng/mL, at which concentration the coefficient of variation was 16.3% in a single assay run. Repeated analyses of quality control samples, nominally at 2 ng/mL, were carried out over a number of assay runs with a coefficient of variation of 10.4%. The method is specific for salmeterol with respect to endogenous plasma components and identified metabolites. The assay was applied to the analysis of salmeterol in plasma of rats and dogs from pharmacokinetic studies.

Adrenergic beta-Agonists↗

PubMed1998

Fully-automated systematic toxicological analysis of drugs, poisons, and metabolites in whole blood, urine, and plasma by gas chromatography-full scan mass spectrometry.

The availability of automated, rapid and reliable methods for the systematic toxicological analysis (STA) of drugs and poisons in biosamples is of great importance in clinical and forensic toxicology laboratories. Gas chromatography-continuous scan mass spectrometry (GC-MS) possesses a high potential in STA because of its selectivity and identification power. However, in order to develop a fully automated STA method based on GC-MS two main obstacles have to be overcome: (a) sample preparation is rather sophisticated owing to the need to isolate analytes from the aqueous matrix and to allow a correct GC repartition of polar analytes; (b) the large amount of information collected within a single analysis makes it difficult to isolate relevant analytical information (mass spectra of analytes) from the chemical noise. Using a bench-top GC-MS system equipped with a laboratory robot for sample preparation (the Hewlett-Packard 7686 PrepStation) and an original method for mass spectral purification, a fully automated STA procedure was developed involving isolation of drugs from the sample (whole blood with minimal pretreatment, plasma, urine) by means of solid-phase extraction, derivatization (trimethylsilylation) of the acidic-neutral and of the basic extracts, GC-MS analysis, processing of data, and reporting of results. Each step of the procedure, and the method for data analysis in particular, can be easily integrated with other existing STA methods based on GC-MS.

Autoanalysis↗

PubMed1997

[A new separation and extraction method--solid-phase micro-extraction].

The principle and application of a new sample preparation method--solid-phase micro-extraction (SPME) are introduced in this paper. An SPME unit consists of a certain length of fused silica fiber coated with stationary phase, and a holder which looks like a microliter syringe. Organic analytes are adsorbed by the fiber, and is directly introduced into the GC injector, where the adsorbed analytes are desorbed. SPME can be used to concentrate volatile and nonvolatile compounds in both liquid and gaseous samples without the use of solvents and provides low detection limits. The technique is more favorable in comparing with other sample preparation methods.

Limit of Detection↗

PubMed1984

Improvement of chemical analysis of antibiotics. VII. Comparison of analytical methods for determination of impurities in tetracycline pharmaceutical preparations.

In order to examine the suitability of our four established methods for the analysis of tetracyclines (high-performance liquid chromatography, reversed-phase thin-layer chromatographic densitometry, reversed-phase thin-layer chromatographic spray reagents and silica gel high-performance thin-layer chromatographic densitometry) for the determination of impurities in tetracycline pharmaceutical preparations, sixteen samples available on the Japanese market were analysed. Because these methods did not always give satisfactory results, their analytical conditions were modified. The comparative studies indicated these methods were accurate and reliable. Therefore, we recommend a combination of these methods for the analysis of impurities, in which the spray reagents are used first as a screening method, and then if the results exceed the limits, a precise determination is carried out using either high-performance liquid chromatography or reversed-phase thin-layer chromatographic densitometry.

Anti-Bacterial Agents↗

PubMedDate not supplied

Proteomic analysis of lipid microdomains from lipopolysaccharide-activated human endothelial cells.

The endothelium plays a critical role in orchestrating the inflammatory response seen during sepsis. Many of the inflammatory effects of Gram-negative sepsis are elicited by lipopolysaccharide (LPS), a glycolipid component of bacterial cell walls. Lipid-rich microdomains have been shown to concentrate components of the LPS signaling system. However, much remains to be learned about which proteins are constituents of lipid microdomains, and how these are regulated following cell activation. Progress in this area would be accelerated by employing global proteomic analyses, but the hydrophobicity of membrane proteins presents an analytical barrier to the effective application of such approaches. Herein, we describe a method to isolate detergent-resistant membranes from endothelial cells, and prepare these samples for proteomic analysis in a way that is compatible with subsequent separations and mass spectrometric (MS) analysis. In the application of these sample preparation and MS analyses, 358 proteins from the lipid-rich microdomains of LPS-activated endothelial cell membranes have been identified of which half are classified as membrane proteins by Gene Ontology. We also demonstrate that the sample preparation method used for solubilization and trypsin digestion of lipid-rich microdomains renders the membrane spanning sequences of transmembrane proteins accessible for endoproteolytic hydrolysis. This analysis sets the analytical foundation for an in-depth probing of LPS signaling in endothelial cells.

Cells, Cultured↗

PubMed1992

Improved method for the preparation of TiN-coated WC-Co-based samples for cross-sectional AEM investigation.

An improved method for the preparation of cross-sectional thin foils of coated WC-Co samples for studies by analytical electron microscopy is described. A braze alloy is used to join the sections of the sample together and the resulting sample is stable during subsequent grinding, dimpling, and milling operations. Cross-sectional micrographs provide examples of the efficacy of this method. No microstructural alteration associated with the brazing operation was observed.

Cobalt↗

PubMed1999

Supercritical fluid extraction of microcystins from cyanobacteria.

A new method for the fast extraction of microcystins RR and LR in cyanobacterium was developed using supercritical CO2. The microcystins were successfully extracted with aqueous methanol modified supercritical fluid (90% CO2, 9.0% methanol, 1.0% water). The method developed here has several advantages over solid-phase extraction sample preparation for the analysis of microcystins. Sample handling steps are minimized, thus reducing possible losses of analytes and saving analysis time. No organic solvent extractions are involved in this method, and no cleanup steps are employed.

Chromatography, High Pressure Liquid↗

PubMed2006

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

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-microL 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.

Animals↗

PubMed2004

Matrix-dependent cationization in MALDI mass spectrometry.

The matrix dependence in cationization processes, the competition between cationization and protonation and the question of whether gas-phase cation transfer or attachment of free cations dominates in matrix-assisted laser desorption/ionization mass spectrometry were studied. Two different sample preparation methods were employed, the dried-droplet sample preparation and a mixture of solid matrix, analyte and salt. The latter ensures that the formation of cation adducts takes place in the gas phase. By monitoring the suppression of matrix signals for different matrices, it was found that matrices with high gas-phase metal ion binding energies require high analyte concentrations for matrix suppression to occur. By comparing the mass spectra obtained using sinapinic acid or sinapinic methyl ester as a matrix, a correlation between cationization and deprotonation of matrix molecules was found. It is also demonstrated that attachment of free gas-phase cations, rather than cation transfer from the cationized matrix, is the predominant process in cationization.

Anti-Bacterial Agents↗

PubMed2005

Improved matrix-assisted laser desorption/ionisation sample preparation of a partially depolymerised cellulose derivative by continuous spray deposition and interfacing with size-exclusion chromatography.

Continuous spray deposition (CSD) of aqueous solutions of partially depolymerised methyl cellulose was found to improve matrix-assisted laser desorption/ionisation (MALDI) sample preparation. One feature was that the sensitivity in MALDI time-of-flight mass spectrometry increased up to an order of magnitude compared with the standard sample preparation method. Another feature was that CSD provided targets for MALDI with homogeneously distributed analyte. This resulted in a more even signal intensity and a higher reproducibility than in the standard method. High-mass discrimination was more pronounced in CSD than in the standard method. Size-exclusion chromatography with aqueous eluent was coupled online to CSD onto matrix-precoated foils. The suitability for determination of the molar mass distribution of methyl cellulose was investigated.

Biopolymers↗

PubMed1985

A high-performance liquid chromatographic procedure for the purification of mouse monoclonal antibodies.

High-performance liquid chromatography was applied to the purification of monoclonal antibodies from mouse ascites fluid. The method was based on anion-exchange chromatography using a TSK DEAE-5PW column and a gradient elution with 20 mM Tris, pH 8.5, and 20 mM Tris, pH 8.5, containing 2.0 M sodium acetate. The method can be applied to analytic or preparative scale separations. Purified immunoglobulins were isolated from samples of 20 to 100 microliter containing up to 19 mg total protein. The average recovery of total protein was 89 +/- 12%. Recovery of the immunoglobulins, based on recovery of immunological activity, was quantitative. In addition to separating the immunoglobulins from the other serum proteins, the various classes of IgG were resolved.

Animals↗

PubMed2006

A recombinant Fab fragment-based electrochemical immunosensor for the determination of testosterone in bovine urine.

This work describes the development of an electrochemical, recombinant Fab fragment-based immunosensor for the detection of testosterone in bovine urine. The sensor comprised of a testosterone conjugate on the surface of screen-printed electrodes, and recognition followed by an anti-testosterone Fab fragment. The use of an IgG-horseradish peroxidase conjugate determined the degree of competition. Chronoamperometry at a potential of +100 mV, was chosen to reductively measure the product of the catalysis of 3,3',5,5'-tetramethylbenzidine catalysis. ELISA was primarily used to investigate the assay system, prior to transferring to SPEs. The final Fab-based sensor exhibited the linear range of 300-40,000 pg/ml with limit of detection of 90+/-13 pg/ml. Furthermore, the developed Fab sensor allowed for the determination of testosterone in bovine urine directly after dilution, omitting the necessity of extraction and hydrolysis. Comparison of administrated bovine urine samples between the developed Fab sensor and GC-MS data showed quantitative or semi-quantitative results and enabled identification of suspicious samples for further extensive analysis by established analytical techniques. With simple sample preparation, low limit of detection, and good repeatability, the proposed method can offer alternative advantages as a primary screening tool for meat quality control.

Animals↗

PubMed2002

Profile--Richard A. Mathies. Interview by Suzanne Berry.

Richard A. Mathies (Fig. 1) is a professor of chemistry at the University of California (UC) at Berkeley. His early work at UC was on the use of resonance Raman and time-resolved optical spectroscopy to elucidate the structure and reaction dynamics of energy and information-transducing photoactive proteins called rhodopsins. His work on the Human Genome Project led to the development of high-throughput platform technologies including capillary array electrophoresis and energy transfer fluorescent dye labels for DNA sequencing and analysis. He has also pioneered the development of microfabricated capillary electrophoresis devices, capillary array electrophoresis microplates and microfabriated integrated sample preparation and detection methods. He is the co-founder of the Center for Analytical Biotechnology at UC Berkeley. Mathies was interviewed at the BIOMEMS and Biomedical Nanotechnology conference in Columbus, Ohio, 21-25 September 2001, where he gave a talk about capillary array electrophoresis-based microprocessors. Such devices could be used as point-of-care clinical and genetic analyzers, in integrated microfluidic sequencing chips and in DNA-based computing.

Awards and Prizes↗

PubMed2002

Chemical analysis of used three-way catalysts by total reflection X-ray fluorescence.

The methodology developed for evaluating, by total reflection X-ray fluorescence, the main elements in used three-way catalysts for cars after more than 59 000 km is described. The analytical method does not require chemical manipulation of the samples, is quick (30 min for sample preparation and 10 min for analysis), precise (between 1% and 10% of variation coefficient), and simple. The two catalytic monoliths contained in the cartridge of a car with more than 59,000 km have been analyzed. The mass relationships between the detected elements and Si, a component of the cordierite ceramic substrate, have been used to follow the axial and radial profiles of the elements. Information concerning the loss of active elements and the retention of contaminating elements as a consequence of the working conditions was attained by comparison between the results obtained for the used catalyst (59 000 km) with those of a fresh catalyst (0 km). The interface effect between the first and the second catalytic bricks was also studied.

Air Pollutants↗

PubMed1983

Determination of vanadium in workplace air by DCP emission spectrometry.

This paper provides a method for directly determining vanadium in workplace air by direct current plasma atomic emission spectrometry (DCP-AES). Wavelength selection, instrument operating parameters, and sample preparation methods were studied. It was found that the most suitable wavelength for the analytical line is 437.924 nm (DL 0.006 mg/L) but also the line 309.311 nm (DL 0.003 mg/L) can be used. The results obtained by DCP-AES were compared with those obtained by both flame (FAAS) and electrothermal atomization (ETA-AAS) atomic absorption spectrometry.

Air Pollutants, Occupational↗

PubMed2000

Simultaneous determination of zidovudine and lamivudine in human serum using HPLC with tandem mass spectrometry.

A method employing high performance liquid chromatography (HPLC) with tandem mass spectrometry (MS) has been developed and validated for the simultaneous determination of clinically relevant levels of zidovudine (AZT) and lamivudine (3TC) in human serum. The method incorporates a fully automated ultrafiltration sample preparation step that replaces the solid-phase extraction step typically used for HPLC with UV detection. The calibration range of the dual-analyte LC-MS/MS method is 2.5-2,500 and 2.5-5,000 ng ml-1 for AZT and 3TC, respectively, using 0.25 ml of human serum. The lower limit of quantification was 2.5 ng ml-1 for each analyte, with a chromatographic run time of approximately 6 min. Overall accuracy, expressed as bias, and inter- and intra-assay precision are < +/- 7 and < 10% for AZT, and < +/- 5 and < 12.1% for 3TC over the full concentration ranges. A cross-validation study demonstrated that the LC-MS/MS method afforded equivalent results to established methods consisting of a radioimmuno-assay for AZT and an HPLC-UV method for 3TC. Moreover, the LC-MS/MS was more sensitive, allowed markedly higher-throughput, and required smaller sample volumes (for 3TC only). The validated method has been used to support post-marketing clinical studies for Combivir a combination tablet containing AZT and 3TC.

Anti-HIV Agents↗

PubMed2004

Application of solvent microextraction in a single drop for the determination of new antifouling agents in waters.

A new, rapid microextraction technique termed solvent microextraction (SME) has been developed for the simultaneous determination of new generation antifouling agents, in water samples. Chlorothalonil, dichlofluanid and Sea nine 211 were employed as model compounds to asses the extraction procedure and were determined by gas chromatography with electron capture detection. Experimental parameters which control the performance of SME, such as selection of solvent, exposure time, agitation, organic drop volume, and salt concentration were optimized. The new method provided good average enrichment factors of >10.7 for all analytes, good precision (RSD < 8.5%) and good linearity (r2 > 0.9880). The limits of detection (LODs) were in the range of 0.00025-0.003 microg/L (S/N = 3). The SME was performed in different type of natural water samples and acceptable recoveries were obtained for the tested analytes. The results demonstrated that SME is a rapid, accurate and effective preparation method and could be successfully performed for the determination of antifouling agents in water samples.

Aniline Compounds↗