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PubMed2002

Quantification of ephedrines in urine by column-switching high-performance liquid chromatography.

A method for the quantification of five congener ephedrines in urine samples without sample preparation was developed. The analytes were trapped on a C18 precolumn and separated on a C18 BDS analytical column. Baseline separation was achieved for all analytes. The method meets the requirements of the International Olympic Committee (IOC) medical commission regarding cut-off limits for positive doping cases with ephedrines.

Chromatography, High Pressure Liquid↗
PubMed1994

An alternative method for the analysis of phenol and o-, m-, and p-cresol by capillary GC/FID.

An alternative method for the sampling and simultaneous analysis of phenol, o-, m-, and p-cresol, employing XAD-7 as a sorbent for the collection of each analyte, is described. Desorption was achieved with methanol followed by analysis of all samples using gas chromatography with flame ionization detection. The separation of all analytes was achieved on a Stabilwax-DA capillary column. Sample collection and preparation was improved over current methods used at the National Institute for Occupational Safety and Health. The results obtained when a Stabilwax-DA capillary column was used in the analysis, as compared to those obtained using a Stabilwax capillary column, indicated achievement of baseline separation of the analytes. Peak resolution and overall peak shape were enhanced by the use of the Stabilwax-DA column. Lower limits of detection were achieved for each analyte. Desorption efficiency and storage stability results (30 days) were acceptable. Sample stability in solution and on solid sorbent tubes was examined. The relative standard deviation of the analytical portion of the method was found to be 0.045. This method provides a simplified, concise, simultaneous analysis of phenol, o-, m-, and p-cresol.

Acrylic Resins↗
PubMed1997

Determination of standard zinc values in the intact tissues of mice by ICP spectrometry.

The most commonly encountered difficulties for the quantitative measurement of zinc in biological samples are the limited sample amount, total and effective digestion of connective and fatty residues, and low zinc concentrations. These problems often lead to the determination of lower zinc values than actually present, so that the sample preparation, digestion, and analytical procedure deserve careful attention. In this short communication, a new method for microwave tissue disintegration is described. The authors have obtained consistent and reproducible results with tissue samples of 0.5 g or less.

Animals↗
PubMed1997

Direct determination of polyglucose metabolites in plasma using anion-exchange chromatography with pulsed amperometric detection.

High-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) was evaluated for the quantitation of polyglucose metabolites (DP2-DP7) in human plasma. The method was investigated for accuracy, precision, specificity, linearity, range and analyte stability. Samples were prepared by dilution into the standard range (0.1-10 microg/ml) followed by deproteinization using a 30,000 molecular mass cut-off filtration device. The limit of detection was 0.05 microg/ml for all metabolites. Method precision for DP2-DP7 varied from approximately 2% R.S.D. in the upper range to approximately 15% R.S.D. at the limit of quantitation. Samples were stable following one or two freeze-thaw cycles and, after preparation, they could be refrigerated for up to 72 h. Application of this method to clinical plasma samples from continuous ambulatory peritoneal dialysis (CAPD) patients administered one daily night-time intraperitoneal exchange of 2 l of 7.5% polyglucose solution for four weeks indicated that plasma levels of DP2, DP3 and DP4 increased from baseline levels of <0.01 g/l to steady-state levels of 1.2+/-0.3, 1.2+/-0.3 and 0.4+/-0.1 g/l (mean+/-S.D.), respectively. These steady state plasma levels for DP2 and DP3 are comparable to previously reported levels in patients administered daily overnight 7.5% polyglucose dialysis solution.

Chromatography, Ion Exchange↗
PubMedDate not supplied

Detection of thiazide-based diuretics in equine urine by liquid chromatography/mass spectrometry.

Thiazide-based diuretics are included in the list of banned drugs in the horse-racing industry. One effect of their misuse is increased urine flow, contributing to dilution of other doping agents. Their determination is essential in ensuring compliance to horse-racing regulation. This study evaluates the feasibility of using liquid chromatography/mass spectrometry (LC/MS) with electrospray and atmospheric pressure chemical ionization interfaces to analyze thiazidic diuretics in equine urine samples. Existing LC and gas chromatography/MS methods are limited in their applicability to thiazide analysis. Sample preparation, analyte extraction, chromatographic separation, ion-source collision induced dissociation, solvent composition, ionization mode, and ion polarity are discussed. The practicality of LC/MS for this analysis is demonstrated with actual equine administration samples collected at specified time intervals. Detection limits were 270 ng/mL for chlorothiazide, 131 ng/mL for hydrochlorothiazide, and 384 ng/mL for trichlormethiazide.

Animals↗
PubMed2001

Quantitative evaluation of the CEEM soil sampling intercomparison.

The aim of the CEEM soil project was to compare and to test the soil sampling and sample preparation guidelines used in the member states of the European Union and Switzerland for investigations of background and large-scale contamination of soils, soil monitoring and environmental risk assessments. The results of the comparative evaluation of the sampling guidelines demonstrated that, in soil contamination studies carried out with different sampling strategies and methods, comparable results can hardly be expected. Therefore, a reference database (RDB) was established by the organisers, which acted as a basis for the quantitative comparison of the participants' results. The detected deviations were related to the methodological details of the individual strategies. The comparative evaluation concept consisted of three steps: The first step was a comparison of the participants' samples (which were both centrally and individually analysed) between each other, as well as with the reference data base (RDB) and some given soil quality standards on the level of concentrations present. The comparison was made using the example of the metals cadmium, copper, lead and zinc. As a second step, the absolute and relative deviations between the reference database and the participants' results (both centrally analysed under repeatability conditions) were calculated. The comparability of the samples with the RDB was categorised on four levels. Methods of exploratory statistical analysis were applied to estimate the differential method bias among the participants. The levels of error caused by sampling and sample preparation were compared with those caused by the analytical procedures. As a third step, the methodological profiles of the participants were compiled to concisely describe the different procedures used. They were related to the results to find out the main factors leading to their incomparability. The outcome of this evaluation process was a list of strategies and methods, which are problematic with respect to comparability, and should be standardised and/or specified in order to arrive at representative and comparable results in soil contamination studies throughout Europe. Pre-normative recommendations for harmonising European soil sampling guidelines and standard operating procedures have been outlined in Wagner G, Desules A, Muntau H, Theocharopoulos S. Comparative Evaluation of European Methods for Sampling and Sample Preparation of Soils for Inorganic Analysis (CEEM Soil). Final Report of the Contract SMT4-CT96-2085, Sci Total Environ 2001;264:181-186. Wagner G, Desaules A, Munatu H. Theocharopolous S, Quevauvaller Ph. Suggestions for harmonising sampling and sample pre-treatment procedures and improving quality assurance in pre-analytical steps of soil contamination studies. Paper 1.7 Sci Total Environ 2001b;264:103-118.

Environmental Monitoring↗
PubMed2005

Sample preparation of organic liquid for off-site analysis of chemical weapons convention related compounds.

Off-site analysis of chemical warfare agents (CWAs) and related compounds plays a key role in the verification program of the Chemical Weapons Convention (CWC). The analysis results, aiming toward unambiguous identication of compounds, depend on the type of sample preparation method. Development of milder sample preparation methods, which offer good recoveries and do not alter the structure of analytes, is highly desirable. Organic liquid with high hydrocarbon background is a frequently encountered challenge in off-site analysis and in official proficiency tests conducted by OPCW. Sample cleanup procedures, namely, solvent exchange followed by cooling and liquid-liquid extraction were studied to eliminate the hydrocarbons from organic liquid. Acetonitrile, a polar aprotic solvent, was effectively used to remove the background in both methods, and recoveries of spiked CWAs by the two techniques were between 69 and 99%.

Chemical Warfare Agents↗
PubMedDate not supplied

Contributions of mass spectrometry in the study of nucleic acid-binding proteins and of nucleic acid-protein interactions.

Nucleic-acid-protein (NA-P) interactions play essential roles in a variety of biological processes-gene expression regulation, DNA repair, chromatin structure regulation, transcription regulation, RNA processing, and translation-to cite only a few. Such biological processes involve a broad spectrum of NA-P interactions as well as protein-protein (P-P) interactions. These interactions are dynamic, in terms of the chemical composition of the complexes involved and in terms of their mere existence, which may be restricted to a given cell-cycle phase. In this review, the contributions of mass spectrometry (MS) to the deciphering of these intricate networked interactions are described along with the numerous applications in which it has proven useful. Such applications include, for example, the identification of the partners involved in NA-P or P-P complexes, the identification of post-translational modifications that (may) regulate such complexes' activities, or even the precise molecular mapping of the interaction sites in the NA-P complex. From a biological standpoint, we felt that it was worth the reader's time to be as informative as possible about the functional significance of the analytical methods reviewed herein. From a technical standpoint, because mass spectrometry without proper sample preparation would serve no purpose, each application described in this review is detailed by duly emphasizing the sample preparation-whenever this step is considered innovative-that led to significant analytical achievements.

Animals↗
PubMed1997

Determination of the halothane metabolites trifluoroacetic acid and bromide in plasma and urine by ion chromatography.

Halothane (CF3CHClBr), a widely used volatile anesthetic, undergoes extensive biotransformation in humans. Oxidative halothane metabolism yields the stable metabolites trifluoroacetic acid and bromide which can be detected in plasma and urine. To date, analytical methodologies have either required extensive sample preparation, or two separate analytical procedures to determine plasma and urine concentrations of these analytes. A rapid and sensitive method utilizing high-performance liquid chromatography-ion chromatography (HPLC-IC) with suppressed conductivity detection was developed for the simultaneous detection of both trifluoroacetic acid and bromide in plasma and urine. Sample preparation required only ultrafiltration. Standard curves were linear (r2> or =0.99) from 10 to 250 microM trifluoroacetic acid and 2 to 5000 microM bromide in plasma and 10 to 250 microM trifluoroacetic acid and 2 to 50 microM bromide in urine. The assay was applied to quantification of trifluoroacetic acid and bromide in plasma and urine of a patient undergoing halothane anesthesia.

Bromides↗
PubMed2002

Quantitative NMR spectroscopy using coaxial inserts containing a reference standard: purity determinations for military nerve agents.

A novel 31P NMR method for the determination of purity for the military nerve agents sarin, soman, and VX has been developed. In contrast to more conventional quantitative NMR methods, stem coaxial inserts are placed into the sample tube to introduce reference material into the analysis without mixing or reaction with the analyte. All sample preparation is eliminated, and the analysis is completed expeditiously in less than 25 min. The method is highly specific and rugged with respect to operator-induced variability, experimental parameters, and all influences from nuclear magnetic relaxation. Nerve agent purity can be determined with a precision and accuracy typically better than 1%, and impurities can be detected at concentrations as low as 25 microg/mL. The limit of quantitation has been estimated at 85 microg/mL. In terms of precision, accuracy and execution time, the method rivals typical chromatographic methods.

Chemical Warfare Agents↗
PubMed1995

High-performance liquid chromatographic method for the determination of a novel thymidylate synthase inhibitor, AG 331, in human serum.

AG 331 is a novel thymidylate synthase inhibitor currently in Phase I clinical trial. To determine the pharmacokinetic parameters of AG 3331 in human subjects, a suitable analytical method was developed using high-performance liquid chromatography. Serum and urine samples were prepared using both solid-phase extraction and solvent extraction. Either 4,4'-diaminodiphenyl sulfone or benz[cd]indole-2(1H)-one were used as internal standards for the method. A reversed-phase C18 analytical column completely resolved the drug and internal standard peaks from non-specific substances present in biological matrix. The method was validated for precision, accuracy, and reproducibility in serum and was linear over a concentration range of 50-2000 ng/ml, with a limit of detection of 20.0 ng/ml and a quantifiable limit of 50 ng/ml.

Chromatography, High Pressure Liquid↗
PubMed1995

General strategies in chromatographic analysis of lipids.

Lipid extracts of natural sources contain a large number of lipid classes and molecular species. Completely reproducible samples are obtained only with great care and skill. Analytical methods other than chromatography and/or mass spectrometry are of little use for resolution and identification of lipid molecules even in simple mixtures. The analytical information desired governs the selection of the chromatographic and mass spectrometric method, which determine the sample preparation and derivative needed. Usually a combination of chromatographic methods is necessary to identify specific species of lipids. The recent development of soft ionization techniques, that are readily interfaced with mass spectrometers, have greatly simplified the sample preparation and have largely eliminated the need for derivatization. Because these techniques require expensive equipment and dedicated operators, the methods selected must be consistent with the true analytical needs and the available resources. Although personal preference cannot be eliminated entirely, the general strategies outlined below should help to reduce the number of possibilities facing a lipid analyst to a few practical choices.

Chromatography, Gas↗
PubMed2005

Determination of metal and organometal trophic bioaccumulation in the benthic macrofauna of the Adour estuary coastal zone (SW France, Bay of Biscay).

A multidisciplinary approach has been adopted in order to investigate the bioaccumulation of metals and organometals in macrobenthic populations. A complete method coupling a sampling strategy and classification of benthic organisms with a performant analytical procedure for the analysis of both metals and organometals has been developed. A single sample preparation method using a TMAH extraction and species specific isotope dilution makes it possible to analyse metals and organometals in the same extract, which is especially interesting for situations where only a limited amount of sample is available. Low detection limits have been obtained in the range of 12-250 pg g(-1) for mercury and butyltin compounds and 0.4-50 ng g(-1) for metals with good precision (1-10% RSD) even for a very low mass of sample (0.02 g). This method has been applied for monitoring contamination and bioaccumulation of metals and organometals as well as the biodiversity and trophic structure of the macrobenthic population of the Adour Estuary (South-West, France). The benthic macrofauna diversity indicates that inner estuarine stations are moderately polluted whereas outer estuarine stations are less impacted. However, metals concentrations in both sediment and benthic biomass do not change drastically between stations. Moreover, the bioaccumulation has been determined in relation to the feeding guild of benthic organisms. The results demonstrate that higher bioaccumulation is generally observed for deposit feeders directly impacted by sediment contamination compared to suspensive feeders and predators. Biomagnification along the trophic levels was highlighted for MMHg but no significant trend was observed for the other metallic compounds.

Animals↗
PubMed2004

Fast liquid chromatographic-tandem mass spectrometric (LC-MS-MS) determination of metformin in plasma samples.

Liquid chromatographic-tandem mass spectrometric (LC-MS-MS) methods for the determination of metformin in plasma from different species are presented. The first method employed a YMC cyano 2mm x 50 mm, 3 microm analytical column. For minimum sample preparation direct injection of samples after protein precipitation was performed. The polar column used with highly organic mobile phases provided a normal phase retention mechanism. The elution conditions were optimized to obtain reproducible peak areas and good peak shape. A step gradient from 100% acetonitrile to acetonitrile-water 80:20 (v/v) containing 10mM ammonium acetate and 1% acetic acid was applied, leading to a sample-to-sample cycle time of 2 min. In a second method, a column-switching LC-MS-MS assay for on-line trapping was developed. The analyte and internal standard were trapped on a YMC cyano 2 mm x 10 mm, 5 microm column using acetonitrile-methanol 95:5 (v/v). Elution was performed isocratically in back-flush mode on to the analytical column (YMC cyano 2 mm x 50 mm, 3 microm) using 10 mM ammonium acetate in acetonitrile-water 80:20 (v/v) with 1% formic acid. With this approach, the signal-to-noise ratio was improved and the run time could be shortened to 1 min. Calibration samples were prepared in the matrix to be assayed in the range of 10-10,000 ng/ml. Quality control (QC) samples were prepared at 40, 400 and 4000 ng/ml and interspersed with the unknown study samples in the assays. Deviations for precision and accuracy were less than 20% for the lower limit of quantification (LLOQ) and low QC sample and less than 15% for other calibrators and QCs.

Animals↗
PubMed2006

Acoustic-resonance spectrometry as a process analytical technology for the quantification of active pharmaceutical ingredient in semi-solids.

The purpose of this study was to demonstrate acoustic resonance spectrometry (ARS) as an alternative process analytical technology to near infrared (NIR) spectroscopy for the quantification of active pharmaceutical ingredient (API) in semi-solids such as creams, gels, ointments, and lotions. The ARS used for this research was an inexpensive instrument constructed from readily available parts. Acoustic-resonance spectra were collected with a frequency spectrum from 0 to 22.05 KHz. NIR data were collected from 1100 to 2500 nm. Using 1-point net analyte signal (NAS) calibration, NIR for the API (colloidal oatmeal [CO]) gave an r2 prediction accuracy of 0.971, and a standard error of performance (SEP) of 0.517%CO. ARS for the API resulted in an r2 of 0.983 and SEP of 0.317%CO. NAS calibration is compared with principal component regression. This research demonstrates that ARS can sometimes outperform NIR spectrometry and can be an effective analytical method for the quantification of API in semi-solids. ARS requires no sample preparation, provides larger penetration depths into lotions than optical techniques, and measures API concentrations faster and more accurately. These results suggest that ARS is a useful process analytical technology (PAT).

Acoustics↗
PubMed2000

Determination of total sulfur compounds and benzothiazole in asphalt fume samples by gas chromatography with sulfur chemiluminescence detection.

As part of a collaborative project between the National Institute for Occupational Safety and Health and the Federal Highway Administration to evaluate asphalt pavers' exposures to asphalt fume and their potential health effects, a method was developed for the determination of total sulfur compounds and benzothiazole in asphalt fume samples. Asphalt fume samples were collected from asphalt mixtures with and without the addition of ground-up rubber tires. The asphalt fume samples were collected with sampling trains that consisted of a Teflon membrane filter and an XAD-2 adsorbent tube. Filter and sampling tube media were extracted with hexane and subsequently analyzed by gas chromatography with a sulfur chemiluminescence detector. Separation was achieved with a 100 percent dimethyl polysiloxane fused silica column. Typical calibration curves had linear correlation coefficients of 0.99 or better with a relative standard deviation (RSD) of 5 percent. Benzothiazole desorption efficiency (DE) determined using spiked sampling tubes ranged from 96.5 percent at 5.0 micrograms to 89.4 percent at 40 micrograms with RSD values from 0.9 to 4.0 percent. Benzothiazole storage recovery determined using sampling tubes spiked at 20 micrograms and refrigerated for 30 days at 4 degrees C was 89.8 percent when corrected for the DE with an RSD of 1.1 percent. The limit of detection for the method determined using spiked sampling tubes was 0.30 microgram. Quantitation for total sulfur compounds and benzothiazole was against benzothiazole standards in hexane. Because of detector selectivity, sample preparation consisted of a simple hexane extraction even when samples had a high background due to hydrocarbon overload. Detector sensitivity provided quantitation in the sub-microgram region. Because of the sample preparation step and because benzothiazole was determined during the same analysis run, this method is straightforward and analytically efficient. The method has been used to analyze asphalt fume samples collected at several asphalt paving and roof operations.

Air Pollutants, Occupational↗
PubMed1991

[Evaluation of methods for the analysis of low insulin concentrations in serum].

Three methods of the determination of insulin in serum were optimized in order to determine low concentrations of this analyte reliably (Method I: enzymatic after acidic hydrolysis of inulin; Method II: by anthrone/sulfuric acid reagent; Method III: by cysteine/tryptophan reagent). The interfering reaction of glucose in the methods I and II was avoided by the preincubation of samples with glucose oxidase/catalase reagent. The detection limit of all three methods was below 5 mg/l and the within-run precision amounted to values below 5%. Method I and II gave identical results. In comparison with these two methods, method III resulted in inulin values by about 8% lower, because inulin, depending on the lot used, contained alkali-labile fractions which were destroyed during the sample preparation. Method II is recommended for routine measurements because of its an analytical reliability and its cost-effectiveness.

Catalase↗
PubMed2002

An analytical protocol for the determination of total mercury concentrations in solid peat samples.

Traditional peat sample preparation methods such as drying at high temperatures and milling may be unsuitable for Hg concentration determination in peats due to the possible presence of volatile Hg species, which could be lost during drying. Here, the effects of sample preparation and natural variation on measured Hg concentrations are investigated. Slight increases in mercury concentrations were observed in samples dried at room temperature and at 30 degrees C (6.7 and 2.48 ng kg(-1) h(-1), respectively), and slight decreases were observed in samples dried at 60, 90 and 105 degrees C (2.36, 3.12 and 8.52 ng kg(-1) h(-1), respectively). Fertilising the peat slightly increased Hg loss (3.08 ng kg(-1) h(-1) in NPK-fertilised peat compared to 0.28 ng kg(-1) h(-1) in unfertilised peat, when averaged over all temperatures used). Homogenising samples by grinding in a machine also caused a loss of Hg. A comparison of two Hg profiles from an Arctic peat core, measured in frozen samples and in air-dried samples, revealed that no Hg losses occurred upon air-drying. A comparison of Hg concentrations in several plant species that make up peat, showed that some species (Pinus mugo, Sphagnum recurvum and Pseudevernia furfuracea) are particularly efficient Hg retainers. The disproportionally high Hg concentrations in these species can cause considerable variation in Hg concentrations within a peat slice. The variation of water content (1.6% throughout 17-cm core, 0.97% in a 10 x 10 cm slice), bulk density (40% throughout 17-cm core, 15.6% in a 10 x 10 cm slice) and Hg concentration (20% in a 10 x 10 cm slice) in ombrotrophic peat were quantified in order to determine their relative importance as sources of analytical error. Experiments were carried out to determine a suitable peat analysis program using the Leco AMA 254, capable of determining mercury concentrations in solid samples. Finally, an analytical protocol for the determination of Hg concentrations in solid peat samples is proposed. This method allows correction for variation in factors such as vegetation type, bulk density, water content and Hg concentration in individual peat slices. Several subsamples from each peat slice are air dried, combined and measured for Hg using the AMA254, using a program of 30 s (drying), 125 s (decomposition) and 45 s (waiting). Bulk density and water content measurements are performed on every slice using separate subsamples.

Environmental Monitoring↗