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At least 865 records · Page 48Linked to original sources
PubMed2004

A new method for the quantitation of propofol in human plasma: efficient solid-phase extraction and liquid chromatography/APCI-triple quadrupole mass spectrometry detection.

Propofol (2,6-diisopropyl phenol) is widely used for the induction and maintenance of anesthesia. Analyses of its pharmacokinetics require simple and sensitive methods for quantitation of propofol in human plasma. Previously reported HPLC and GC methods are limited by cumbersome extraction steps. We describe a novel method that combines sample preparation by solid-phase extraction (SPE) with hydrophilic-lipophilic balance cartridges and analysis with a sensitive LC-APCI-triple quadrupole mass spectrometry (MS/MS) method for better quantitation. The absolute recovery of the analyte was greater than 96%. The limit of quantification for propofol in plasma at a signal-to-noise ratio of 10 was 5 ng/ml. The precision of the assay yielded coefficients of variation ranging from 2.9 to 5.3% and an accuracies of 99-105%. Our method advances the quantitative analysis of propofol in human plasma by combining simple, rapid and efficient SPE with specific and sensitive quantitation by HPLC with APCI-MS/MS detection.

Anesthetics, Intravenous↗
PubMed2001

Separation and identification methods for metalloproteinase inhibitors.

Metalloproteinase inhibitors are being explored for the treatment of a wide variety of human diseases including cancers, arthritis, cardiovascular disorders, human immunodeficiency virus infection, and central nervous system illnesses. This review provides an overview of various analytical sample preparation, separation, detection, and identification techniques employed for the quantitative and qualitative determination of these inhibitor compounds. Special emphasis is placed on biological sample preparation by automated solid-phase extraction, liquid-liquid extraction, and protein precipitation by centrifugation or filtration. Other sample preparation methodologies are also evaluated. Applications of high-performance liquid chromatography. gas chromatography, and capillary electrophoresis to the quantitative determination of metalloproteinase inhibitors are described. Examples of qualitative analysis of metalloproteinase inhibitors by hyphenated liquid chromatography with mass spectrometry and nuclear magnetic resonance are also presented. The advantages and limitations of these separation and identification methodologies as well as other less frequently employed techniques are assessed and discussed.

Chromatography, Gas↗
PubMed2006

A non-perturbing scheme for the mineralogical characterization and quantification of inorganic colloids in natural waters.

Although the role played by inorganic colloids in natural waters depends on their composition as well as on their size, the characterization of submicron particles has rarely gone beyond describing the morphology and identifying some of the most abundant particles. The process of quantification has been hampered by a lack of suitable analytical methods. This study demonstrates that it is possible to identify and quantify inorganic particles in the colloidal size range by applying a straightforward methodology based on a well-proved, quantitative, and nonperturbing method of sample preparation (direct centrifugation of the samples on transmission electron microscopy grids) in conjunction with particle analysis using widely available techniques: transmission electron microscopy, energy dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED). The method has successfully been applied to six water samples from basins of contrasting geological characteristics. The method has the advantage of minimizing sample modifications by allowing on site sample preparation, using standard equipment, and it is not particularly time-consuming. Notably, the combination of EDS and SAED information makes it possible to characterize and quantify the most abundant components of the colloidal pool in the majority of the aquatic systems: the different types of aluminosilicates.

Colloids↗
PubMed2005

Determination of aromatic hydrotropic drugs in pharmaceutical preparations by the surfactant-binding degree method.

An aggregation parameter-based analytical approach, the surfactant-dye binding degree (SDBD) method, was used, for the first time, to determine aromatic hydrotropic compounds. The anionic dye Coomassie Brilliant Blue G (CBBG) was used as inductor of didodecyldimethylammonium bromide (DDABr) aggregates, whose formation was monitored from changes in the spectral features of the dye. Interactions between hydrotrope and DDABr molecules resulted in a decrease of the degree of binding of the cationic surfactant to CBBG, which was proportional to the concentration of hydrotrope in the aqueous solution. The CBBG-DDABr-hydrotrope chemical system was found to fit to the mathematical expression previously derived for the determination of amphiphilic compounds. The hydrotrope-surfactant bond strength determined the sensitivity achieved for the determination of hydrotropic compounds, which was highly dependent on the molecular structure of the analyte. The high precision (the relative standard deviation for 7 mg l(-1) of salicylic acid was 0.8%), rapidity (measurements were performed in a few minutes) and low cost (in both instrumentation and reactants) of the proposed method, made it especially suitable for quality control. The practical analytical applicability of the SDBD method for the control of hydrotropic drugs in pharmaceutical preparations was demonstrated by quantifying salicylic acid and acetyl salicylic acid in liquid (solutions) and solid (tablets, granulates, unguents, gels and creams) samples, which were directly analyzed after dissolution of the samples.

Chemistry, Pharmaceutical↗
PubMed2006

Unravelling in vitro variables of major importance for the outcome of mass spectrometry-based serum proteomics.

The use of mass spectrometry (MS) for analysing low-molecular weight proteins and peptides from biological fluids has a great, yet not fully realized, potential for biomarker discovery. To prune MS-data as much as possible for non-relevant non-biological variation the development of standardized protocols for handling and processing the samples before MS and adjusting data after MS to compensate for method-induced variability are warranted. This calls for knowledge about how different variables contribute to MS-based proteome analyses. In addition, identification of the peptides involved in pre-analytical variation will be helpful in evaluating the clinical significance of predictive models derived from MS data. Using human sera, extraction by weak cation-exchange magnetic beads, and analysis by MALDI-TOF MS we here evaluated pre-analytical variation and identify peptides involved in this. The influences of humidity, temperature, and time for preparation of sera on spectral changes were evaluated. Also, the reproducibility of the methods and the effect of a baseline correction procedure were examined. Low temperatures, short handling times, and a baseline correction procedure minimize the contribution of artifacts to sample variability as observed by MS. The complement split product C3f and fragments thereof appear to be sensitive indicators of sample handling induced modifications. Other peptides that are indicative of such variability are fibrin and kininogen fragments. Using strict experimental guidelines as well as standardized sample collection procedures it is possible to obtain reproducible peak intensities and positions in serum mass profiling using magnetic bead-based fractionation and MALDI-TOF MS.

Biomarkers↗
PubMed2006

A hollow fiber solvent microextraction approach to measure drug-protein binding.

A new direct method has been developed to determine protein-drug binding based on hollow fiber membrane solvent microextraction. Hollow-fiber membrane solvent microextraction coupled with high-performance chromatography with UV detection was employed to evaluate the binding characteristics of drugs to bovine serum albumin (BSA) and blood serum. It was found that the BSA and matrix in the blood serum did not interfere with the measurement. The method is simple and fast. It lacks the drawbacks of some conventional analytical techniques, such as taking much long time and requiring large volume sample consumption.

Animals↗
PubMed2006

Activity-based matrix metallo-protease enrichment using automated, inhibitor affinity extractions.

An automated inhibitor affinity extraction method for the activity-based enrichment of matrix metallo-proteases (MMPs) is presented. Samples containing purified MMP-12 were first extracted at different flow rates in a syringe pump setup, using cartridges packed with an MMP inhibitor affinity sorbent based on an immobilized hydroxamic acid containing peptide (PLG-NHOH) with mumol/L MMP affinity. Faster extractions, a reduced number of manual manipulations, and higher extraction yields (98.9%-99.3%) were obtained over the whole flow rate range compared to batch extractions. Application of the method to synovial fluid from a rheumatoid arthritis patient followed by gelatin-zymography revealed a strong enrichment of distinct MMPs from this biological sample that were not clearly visible in the original sample. The use of an auto-sampler and a solid-phase extraction (SPE) workstation allowed full automation of the extraction procedure with the potential for on-line coupling to further sample preparation and analytical steps. MMP-12 extractions were optimized showing that ligand density is an important factor with a clear extraction yield optimum around 5 to 7.5 mmol/L. Conditioning of the stationary phase for 1 week prior to use resulted in a further slight increase in extraction yield. Under optimal conditions, an extraction yield of 99.5% was reached with a cartridge contact time of only 13 s for MMP-12. The efficacy of the extraction method for activity-based MMP profiling was further improved by the use of a broad-spectrum MMP inhibitor with nmol/L affinity (TAPI-2). This resulted in an increased extraction yield for all tested MMPs. For MMP-1, -7, -8, -10, -12, and -13 extraction yields of at least 98.8% were obtained, while for MMP-9 (full length and catalytic domain) an extraction yield of at least 96.1% was reached.

Adsorption↗
PubMed2006

Quantitative determination of perfluorinated surfactants in water by LC-ESI-MS/MS.

The surfactants perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and derivatives of the latter have emerged as globally distributed persistent environmental contaminants. Methods for their reliable quantitative determination at ppt-levels (ng/L) are needed in order to detect their main sources, to elucidate their environmental fate, and to identify potential sinks. The common method for water analysis involves preconcentration by SPE followed by LC coupled to ESI MS/MS (LC-ESI-MS/ MS). All sample preparation steps must be carefully optimized in order to arrive at reliable quantitative data. Two major aspects are important: (i) during SPE, contaminations may arise from materials containing traces of PFOA/S; (ii) during LC-ESI-MS/ MS, ionization yields are suppressed by matrix components and depend upon the analyte concentrations in the extracts. The levels of PFOA/S in the river Roter Main near Bayreuth have been determined using the optimized method.

Alkanesulfonic Acids↗
PubMed2003

Confirmatory analysis of 17beta-boldenone, 17alpha-boldenone and androsta-1,4-diene-3,17-dione in bovine urine by liquid chromatography-tandem mass spectrometry.

A sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for confirmatory analysis of 17beta-boldenone (17beta-BOL), 17alpha-boldenone (17alpha-BOL) and androsta-1,4-diene-3,17-dione (ADD) in bovine urine was developed. [2H(2)]17beta-Testosterone (17beta-T-d(2)) was used as the internal standard. Sample preparation involved enzymatic hydrolysis and purification on a C(18) solid-phase extraction column. Chromatographic separation of the analytes was obtained using an RP-C(18) HPLC column. LC-MS-MS detection was carried out with an atmospheric pressure chemical ionisation (APCI) source equipped with a heated nebulizer (HN) interface operating in the positive ion mode. For unambiguous hormone confirmation, three analyte precursor-product ion combinations were monitored during multiple-reaction monitoring (MRM) LC-MS-MS analysis. Overall recovery (%), repeatability (relative standard deviations, RSD, %) and within-laboratory reproducibility (RSD, %) ranged from 92.2 to 97.7%, from 6.50 to 2.94% and from 13.50 to 5.04%, respectively, for all analytes. The limit of quantification in bovine urine was 0.20 ng ml(-1) for 17beta-BOL and ADD and 0.50 ng ml(-1) for 17alpha-BOL. The validated method was successfully applied for determination of 17beta-BOL, 17alpha-BOL and ADD in a large number of bovine urine samples collected within the national Official Residue Control Program.

Androstadienes↗
PubMed2005

Simultaneous determination of OSI-774 and its major metabolite OSI-420 in human plasma by using HPLC with UV detection.

A new method was developed and validated for quantitating OSI-774 and its metabolite OSI-420 in human plasma. Sample preparation involved initial extraction with methyl t-butyl ether followed by back extraction with HCl and re-extraction with methyl t-butyl ether. This extraction process resulted in significant improvement in the specificity, reproducibility and sensitivity. The analytes were separated on a Water Symmetry C18 analytical column and the mobile phase consisted of acetonitrile-0.05 M potassium phosphate buffer (42:58, v/v) (pH 4.8), and monitored at a wavelength 345 nm. Values of between- and within-day precision and accuracy for both OSI-774 and OSI-420 were <20%. This method was successfully applied to study steady-state pharmacokinetics of OSI-774 and OSI-420 in a phase II clinical trial.

Chromatography, High Pressure Liquid↗
PubMed2001

Analysis of nucleotide sugars from cell lysates by ion-pair solid-phase extraction and reversed-phase high-performance liquid chromatography.

Analysis of nucleotide sugar metabolism is essential in studying glycosylation in cells. Here we describe practical methods for both extraction of nucleotide sugars from cell lysates and for their analytical separation. Solid-phase extraction cartridges containing graphitized carbon can be used for the purification of nucleotide sugars by using triethylammonium acetate buffer as a ion-pairing reagent for decreasing retention. After that they are separated by high-performance liquid chromatography using a C18 reversed-phase column and the same ion-pairing reagent for increasing retention. These new sample preparation and analysis methods enable good separation of structurally similar sugar nucleotides, compatibility with rapid evaporative concentration, and possibility to automation. Monitoring the production of GDP-deoxyhexoses in genetically engineered yeast and native bacterial cells are described here as specific applications.

Adsorption↗
PubMed1998

Development of a method for the determination of low contents of asbestos fibres in bulk material.

Asbestos is a category 1 carcinogen under the EU classification, but in the absence of a method to quantify asbestos in a matrix at the 0.1% level, there has been a delay in implementing relevant directives to asbestos. An analytical scheme for identification and quantification of asbestos using polarised light microscopy (PLM) and phase contrast optical microscopy (PCM) has now been developed. When used on artificial mixtures by an experienced laboratory, it achieved the required target performance, at 0.1% asbestos concentration by mass in a bulk sample, to obtain a result, which with 90% probability, is correct within a factor of two. The method of identification by PLM and quantification by PCM has been assessed by interlaboratory comparisons. The method begins with an initial identification using PLM, and depending on asbestos type and matrix a combination of preparation procedures are used to produce the analytical filter. A gentle comminution method was used which reduces the risk of overmilling. The asbestos mass percentage on the filter is quantified using PCM in combination with a PLM attachment for identification of possible non-asbestos fibres. The final method is supported by efficient methods for fibre identification for size determination and calculation of total fibre volume. A statistical analysis of mass concentration estimates was made and the effect of preferred orientation of fibres on the analytical filter was quantified.

Asbestos↗
PubMedDate not supplied

Spectrofluorimetric determination of acetaminophen with N-bromosuccinimide.

A simple, sensitive, and selective method for determination of acetaminophen based on its oxidation using N-bromosuccinimide (NBS) to produce a highly fluorescent product. Optimization of reaction variables was carried out concerning NBS concentration, pH, temperature, reaction time, and stability time. Under optimal analytical conditions, the fluorescent intensity was measured at lambda emission. 442 nm (excitation at lambda 330 nm). The linearity range is 120-800 ng/mL with lower detection limit of 33.6 ng/mL acetaminophen. The method was applied successfully to the determination of the compound in pharmaceutical preparations, with average recovery of 100.3 +/- 2%. The method was also applied successfully to the determination of the drug in spiked plasma samples, with an average recovery of 101.2 +/- 1%. Interference effects of some compounds, present in combination with acetaminophen, were studied and the tolerance limits of these compounds were determined.

Acetaminophen↗
PubMed1988

[Methods of quick-freezing and cryosubstitution of biological tissues in analytical ion microscopy].

The localization and relative concentration of diffusible ions (Li+, K+) or bound but easily displaceable ions (Ca2+) have been studied in myocardium prepared by rapid-freeze fixation and compared with results from chemically prepared samples. Contrary to chemical fixation which gives diffused potassium imaging, cryofixation enables elemental precise mapping in cellular compartment. Bound displazable external calcium, extracted by chemical fixation, is visualized after rapid-freeze fixation. Its localization is distinguished by a bright cellular outline, which corresponds to the glycocalix. Intracellular calcium is less emissive and has the same distribution and concentration whatever the sample preparation. Very movable and present at low concentration in tissues, lithium is localized after rapid-freeze fixation. Those qualitative and quantitative results show the adequation of rapid freeze fixation and freeze substitution to the study of diffusible ions by means of analytical ion microscopy.

Animals↗
PubMed2004

Analysis of the Fusarium mycotoxins fusaproliferin and trichothecenes in grains using gas chromatography-mass spectrometry.

A method is described using gas chromatography-mass spectrometry (GC-MS) for the simultaneous detection of the Fusarium mycotoxins fusaproliferin and seven trichothecenes from grains. Sample purification of the raw extract was carried out with commercial solid phase extraction columns, and the recovery of the more polar analytes was increased by rinsing the column with acetonitrile. A significant matrix effect was found for the analysis of fusaproliferin and trichothecenes; thus, the calibrants should be prepared in a blank matrix. The response was linear in the range used. The mean recovery for fusaproliferin was 60.4 or 62.9%, depending on the spiking level. With respect to the trichothecenes, the recovery was generally higher (70.2-125.3%). The method proved to be repeatable for the analysis of fusaproliferin and trichothecenes. The limit of detection for fusaproliferin in the blank matrix mixture was 50 microg/kg, and that for trichothecenes was 5-15 microg/kg. Thirty-eight Finnish grain samples were analyzed for fusaproliferin and trichothecenes with the method developed. Fusaproliferin was not detected in any of the samples. The mean levels of deoxynivalenol, 3-acetyldeoxynivalenol, nivalenol, HT-2 toxin, and T-2 toxin in Finnish grain samples were 272, 17, 150, 40, and <20 microg/kg, respectively.

Edible Grain↗
PubMed1979

Isotachophoresis of CSF proteins in gel tubes especially gammaglobulins. An analytical and preparative technique for high-separation of CSF proteins.

An isotachophoretic method using polyacrylamide gel (PAG-ITP) in a simple disc electrophoretic equipment with plastic tubes containing the gels, was elaborated and especially designed for studying the gammaglobulins in CSF and serum from control subjects and patients with neurological disorders, especially known or probable MS. The device and the ITP system used, including leading and terminating electrolytes and spacer substances, dividing the gammaglobulins in a reproducible way, are described. No cooling of the gel tubes was needed. The sample volumes varied between 5--500 microliters, and the separation time was 1.5--3.0 h. CSF from patients with verified or probable MS revealed characteristic, increased low-mobility gammaglobulin fractions. Using other ITP systems, such as other spacer compositions, the anodic proteins can also be studied in more detail. PAG-ITP in gel tubes is a simple and inexpensive technique which can be used for both analytical and preparative procedures for biological material such as CSF, serum and extractions from nervous tissues.

Cerebrospinal Fluid Proteins↗
PubMed1996

Simultaneous determination of coumarin, 7-hydroxycoumarin and 7-hydroxycoumarin glucuronide in human serum and plasma by high-performance liquid chromatography.

A HPLC method was developed for the determination of the metabolites of coumarin and 7-hydroxycoumarin in plasma and serum. Separation was based on gradient elution of 7-hydroxycoumarin glucuronide, 7-hydroxycoumarin, coumarin and finally 4-hydroxycoumarin (which is used as an internal standard). Standards, prepared in plasma or serum, and samples were treated with trichloroacetic acid, mixed and centrifuged. The supernatant was removed and analyzed by reversed-phase high-performance liquid chromatography on a C18 column. The limit of detection was 50 ng/ml for 7-hydroxycoumarin and 200 ng/ml for coumarin and 7-hydroxycoumarin glucuronide. The linear range was 0.5-100 micrograms/ml for each of the analytes. The percentage relative standard deviation about the mean measured concentrations were all below 10%. There was no statistical difference between the standard curves prepared in plasma or serum. The method developed was applied to the determination of each of the three compounds in serum, after the administration of 7-hydroxycoumarin, and in plasma after the administration of coumarin. The concentrations of total 7-hydroxycoumarin in the serum samples were also determined by another HPLC method and the results were compared. There was no statistical difference between the results determined.

Chromatography, High Pressure Liquid↗
PubMed1997

An isotope-dilution gas chromatography-mass spectrometry method for trace analysis of xylene metabolites in tissues.

A gas chromatography-mass spectrometry (GC-MS) method using isotope dilution was developed to measure trace levels of xylene metabolites in brain tissues. The primary metabolites of xylene are dimethylphenol (DMP), methylbenzyl alcohol (MBA), toluic acid (TA), and methylhippuric acid (MHA). The internal standard was a mixture of deuterated DMP-d3, TA-d7, and MHA-d7. DMP-d3 was commercially available and was used as the internal standard for both DMP and MBA. TA-d7 and MHA-d7 were biosynthesized by administering xylene-d10 to rats and collecting their urine. Based on the noise peaks in 10 blank samples, the on-column limits of quantitation (mean +10 SD of noise peaks) were approximately 305, 1220, 545, and 386 pg for DMP, MBA, TA, and MHA, respectively. Analyte detection and recovery tests from brain tissues of control rats were conducted by spiking the tissues with 32 nmol/g of each analyte, together with the deuterated metabolites. The tissues were homogenized, extracted with ethyl acetate, and derivatized by trimethylsilylation. One microliter of the sample was injected into the GC-MS. The recoveries of the analytes were 104 +/- 8%, 80 +/- 9%, 93 +/- 10%, and 92 +/- 11% (mean +/- SD, n = 7) for DMP, MBA, TA, and MHA, respectively. The tissue preparation efficiency, which was indicated by absolute recoveries of internal standards, was approximately 33% for DMP, MBA, and TA and approximately 80% for MHA. No metabolites were detected in untreated control tissues. This simple and sensitive method to simultaneously detect major xylene metabolites in brain tissues could also be used for the analysis of blood and urine samples from workers to monitor p-xylene exposure.

Animals↗