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At least 1,171 records · Page 65Linked to original sources
PubMed2006

Determination of tamsulosin in human aqueous humor and serum by liquid chromatography-electrospray ionization tandem mass spectrometry.

A simple, sensitive and selective LC-MS/MS method was developed for the determination of tamsulosin in human aqueous humor and serum to study the recently reported eye-related adverse effects of this alpha(1)-blocker drug. Aqueous humor samples were analyzed by direct injection, after addition of the internal standard, labetalol. Liquid-liquid extraction with ethyl acetate was used for serum sample preparation. The chromatographic separation was performed on a reversed phase column by gradient elution with acetonitrile -0.1% formic acid at a flow-rate of 0.2 ml/min. Detection and quantification of the analytes were carried out with a linear ion trap mass spectrometer, using positive electrospray ionization (ESI) and multiple reaction monitoring (MRM). The limit of quantification was 0.1 ng/ml for both aqueous humor and serum samples and linearity was obtained over the concentration ranges of 0.1-4.7 ng/ml and 0.1-19.3 ng/ml for aqueous humor and serum samples, respectively. Acceptable accuracy and precision were obtained for concentrations within the standard curve ranges. The method has been used for the determination of tamsulosin in aqueous humor and serum samples from patients that were on tamsulosin medication and underwent cataract surgery.

Adrenergic alpha-Antagonists↗
PubMed2003

A simple, rapid, and sensitive method for analysis of SYPRO Red labeled sodium dodecyl sulfate-protein complexes by capillary electrophoresis with laser-induced fluorescence.

We describe a segmental filling method for the analysis of SYPRO Red labeled sodium dodecyl sulfate (SDS)-proteins (SRSPs) by capillary electrophoresis-laser induced fluorescence (CE-LIF) with electroosmotic counterflow of poly(ethylene oxide) (PEO). It is shown that SDS and salt play a crucial role in determining the fluorescence intensity of the SRSP. Although the fluorimetric measurements reveal that the SRSPs fluoresce strongly in Tris-borate (TB) buffer containing 0.1% SDS and high concentrations of NaCl (100 mM), these conditions are not appropriate to CE in view of Joule heating. To overcome that impediment, we applied a plug of 0.1% SDS (1/5 to 1/3 of the injection volume) prior to injection of samples (0.64 microL) prepared in TB buffer containing 50 mM NaCl and SYPRO Red. When using a background electrolyte of 0.6% PEO in TB buffer containing NaCl, electroosmotic counterflow of the analytes allows one to concentrate large sample volumes (up to 1/3 of effective capillary length) in 21 min, with detection of 0.35 and 0.10 nM for bovine serum albumin and casein, respectively. With a linear dynamic range from 10 nM to 5 microM, this method provides the capability of determining the concentration of casein in cow's milk as 0.45 +/- 0.03 mM (n = 5).

Animals↗
PubMed1998

[A method for the assay of histidine decarboxylase activity].

The histamine-forming enzyme histidine decarboxylase (HDC) is induced in various tissues of mice in response to various physiological or inflammatory stimuli including stress, physical exercise, proinflammatory cytokines and hematopoietic cytokines. The induction of HDC also occurs in mast cell-deficient mice. The newly formed histamine produced through the induction of HDC diffuses away from its site of formation without being stored. Therefore, in addition to the release of histamine from mast cells or basophils, the induction of HDC is an important alternative mechanism for supplying histamine. Studies on the newly formed histamine may clarify new physiological or pathological roles of histamine. Here, we introduce a method that we devised for the simultaneous assay of HDC activity of many samples taken from mice. This method is based on (i) a simple method for the preparation of histamine-free enzyme solutions and (ii) a simple manual method for the separation of histamine formed in reaction mixtures containing HDC.

Animals↗
PubMed1992

Design and performance of a mass spectrometric facility for measuring helium isotopes in natural waters and for low-level tritium determination by the 3He ingrowth method.

The design and performance of a mass spectrometric system for the measurement of helium isotopes and very low tritium concentrations in natural waters are described and discussed in the light of analytical precision and accuracy. The system consists of a VG 3000 mass spectrometer with a fully automated inlet system for preparation and purification of the samples. Along with this mass spectrometric system, different custom-fabricated units are described, especially designed for taking samples, extracting helium or degassing tritium samples prior to the mass spectrometric analysis. The 3He detection limit of the system is close to 10(-16) cm3 STP corresponding to a tritium level of 0.003 TU for a 500 g water sample stored six months for 3He regrowth. A vertical oceanic tritium profile from the south hemisphere is presented as an illustration of the system's capability to detect very low tritium concentrations in the environment.

Equipment Design↗
PubMed1999

A method for isolating adult and neonatal airway smooth muscle cells and measuring shortening velocity.

Methods are described for isolating smooth muscle cells from the tracheae of adult and neonatal sheep and measuring the single-cell shortening velocity. Isolated cells were elongated, Ca2+ tolerant, and contracted rapidly and substantially when exposed to cholinergic agonists, KCl, serotonin, or caffeine. Adult cells were longer and wider than preterm cells. Mean cell length in 1.6 mM CaCl2 was 194 +/- 57 (SD) microm (n = 66) for adult cells and 93 +/- 32 microm (n = 20) for preterm cells (P < 0.05). Mean cell width at the widest point of the adult cells was 8.2 +/- 1.8 microm (n = 66) and 5.2 +/- 1.5 microm (n = 20) for preterm cells (P < 0.05). Cells were loaded into a perfusion dish maintained at 35 degreesC and exposed to agonists, and contractions were videotaped. Cell lengths were measured from 30 video frames and plotted as a function of time. Nonlinear fitting of cell length to an exponential model gave shortening velocities faster than most of those reported for airway smooth muscle tissues. For a sample of 10 adult and 10 preterm cells stimulated with 100 microM carbachol, mean (+/- SD) shortening velocity of the preterm cells was not different from that of the adult cells (0.64 +/- 0.30 vs. 0.54 +/- 0.27 s-1, respectively), but preterm cells shortened more than adult cells (68 +/- 12 vs. 55 +/- 11% of starting length, respectively; P < 0.05). The preparative and analytic methods described here are widely applicable to other smooth muscles and will allow contraction to be studied quantitatively at the single-cell level.

Animals↗
PubMed1980

Problems associated with clinical chemistry quality control materials.

Quality control methods and materials are widely used to monitor each and every facet of clinical chemistry laboratory performance. Quality control materials are also used in evaluation of methods and as secondary standards. A wide range of liquid and lyophilized materials are available from commercial sources and are prepared in individual laboratories. Many problems arise in the use of quality control materials. Problems discussed in this review include the use of nonhuman based materials and additives of animal origin, the physical and chemical characteristics of quality control materials that differentiate such samples from those from patients, attempts to generate quality control materials with elevated levels of particular analytes, the difficulties in handling and storage of quality control materials, the dangers of hepatitis, and the stability of quality control materials both during storage in the laboratory and after their reconstitution. The advantages and disadvantages of liquid and lyophilized quality control materials are discussed. The assignation of analyte values is of particular importance as the current trend is to consider inaccuracy of laboratory methods in addition to imprecision. This review assesses relevant publications in an area of fundamental importance to quality control in clinical chemistry.

Animals↗
PubMed2000

Protein identification methods in proteomics.

A combination of high-resolution two-dimensional (2-D) polyacrylamide gel electrophoresis, highly sensitive biological mass spectrometry, and the rapidly growing protein and DNA databases has paved the way for high-throughput proteomics. This review concentrates on protein identification. We first discuss the use of protein electroblotting and Edman sequencing as tools for de novo sequencing and protein identification. In the second part, we highlight matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) as one of the main contemporary analytical methods for linking gel-separated proteins to entries in sequence databases. In this context we describe the two main MALDI-MS-based identification methods: (i) peptide mass fingerprinting, and (ii) post-source decay (PSD) analysis. In the last part, we briefly emphasize the importance of sample preparation for obtaining highly sensitive and high-quality MALDI-MS spectra.

Animals↗
PubMed2004

The application of ultrasound as a rapid method to provide DNA fragments suitable for detection by DNA biosensors.

Contamination of food and water supplies by microorganisms such as Escherichia coli, the need for point-of-care bedside analysis of biological samples, and concerns about terrorist attacks using biological organisms, have made the development of fast, reliable, and sensitive analytical methodologies for use in monitoring of pathogens very important. With a variety of biosensors being developed for extremely sensitive and rapid nucleic acid diagnostics, it has become even more important to shift focus towards creation of methods to decrease the amount of time and effort necessary for sample preparation. The application of ultrasound has the potential to create DNA fragments from genomic material with lengths that are suitable for determination using biosensors and microarrays. For example, application of 85 W power at a frequency of 20 kHz can produce a preponderance of fragments of 100-400 base pairs (bp) within several seconds, and sample processing can lead to over 75% conversion from genomic material to fragments in times of 20-30 s. A proportion of these fragments are in a single-stranded state and are suitable for hydridization with immobilized single-stranded DNA probe oligonucleotides using a fiber optic biosensor. Control of factors such as salt concentration, exposure time, ultrasound power, and the initial temperature of the solution, can affect the length and form (single- or double-stranded) of DNA fragments that are generated by ultrasound, and average fragment length can be adjusted by selection of these operating parameters.

Biosensing Techniques↗
PubMed2004

Determination of hexanal as indicator of the lipidic oxidation state in potato crisps using gas chromatography and high-performance liquid chromatography.

Hexanal (an oxidative state indicator) formed in the headspace of potato crisps during storage was evaluated using two different procedures. First, solid-phase microextraction, an innovative sampling preparation methodology was used. It consisted on the absorption of analytes directly from samples and subsequent thermal desorption on the gas chromatograph (GC) injector. Then, a reversed-phase high-performance liquid chromatographic technique (HPLC) was employed to quantify hexanal in the form of 2,4-dinitrophenylhydrazone derivative. Methods were evaluated in what concerns to validation parameters such as linearity, repeatibility and detection limit. GC (LOD = 1 ng/ml) method resulted in more sensitive method than HPLC (LOD = 9 ng/ml). The most suitable technique for hexanal measurement was selected.

Aldehydes↗
PubMed2004

Narrow-bore high performance liquid chromatographic method for the determination of cetirizine in human plasma using column switching.

An improved column switching high performance liquid chromatographic (HPLC) method was developed for determination of cetirizine in human plasma. Plasma samples were prepared by liquid-liquid extraction using methylene chloride. The samples extracted were initially injected into a clean-up Capcell Pak MF C8 column and the peaks of cetirizine and internal standard were separated to an analytical C18 micro-column via column switching device. This analysis showed highly sensitive and selective results. Also, it was successfully applied to evaluate the pharmacokinetics of cetirizine in human volunteers after single oral administration.

Cetirizine↗
PubMed1998

Residual solvents determination in pharmaceutical products by GC-HS and GC-MS-SPME.

Solid-phase microextraction (SPME) has been applied to the residual solvents determination in pharmaceutical products and was compared with the static headspace. Three fibers with different polymer films were compared and the polydimethylsiloxane/divinylbenzene coated fiber was found to be the most sensitive for the analyzed analytes. Between the investigated sample preparation techniques, gastight-SPME proved to be the most sensitive, with DL values ranging from 5 pg ml(-1) to 2 ng ml(-1). Headspace SPME is more precise, with RSD of peak areas values ranging from 2 to 3%. The headspace SPME method was successfully validated. The validation data are reported in the text. The most important difference between the two techniques is that the gastight SPME showed better behavior towards very volatile solvents. Compared with the static headspace technique, both SPME methods showed superior results, being compatible with the pharmaceutical samples.

Drug Contamination↗
PubMed2006

Quantitative determination of jatrophone in "cachaça" prepared with Jatropha elliptica.

A method for sample preparation and analysis by high performance liquid chromatography with UV detection (HPLC-UV) was developed for analysis of jatrophone in "cachaça" prepared with Jatropha elliptica, administered orally, employed in Brazil for the treatment of venomous snake bites. The linearity, accuracy, precision of the procedure was evaluated. Analytical curve for jatrophone was linear in the range of 16.24-81.20 microg ml(-1). The recovery of the jatrophone in the samples analyzed was 98.99-99.89%. The percent coefficient of variation for the quantitative analysis of the "cachaça" in the analyses was under 2%.

Antineoplastic Agents, Phytogenic↗
PubMed2006

[Application of wavelength selection algorithm to measure the effective component of Chinese medicine based on near-infrared spectroscopy].

Near infrared (NIR) spectroscopy has raised a lot of interest in the pharmaceutical industry because it is a rapid and cost-effective analytical type of spectroscopy with no need for extensive sample preparation, and with the easy-realizable ability of on-line application. The NIR technology can increase the quality control standard of the Chinese medicine and accelerate the entry into the international market. In the present paper, two methods for wavelength selection are applied to the measurement of borneol, one of which is the multiple-chain stepwise, which tends to select many variables in the same area containing valuable information, and the other is the mixture genetic algorithm, which incorporates simulated annealing so as to improve the local searching ability while maintaining the global searching ability. The results present that the number of wavelength is reduced to 16% compared with the original number of wavelength, and the prediction accuracy has increased 47.6%. Therefore, the method of wavelength selection is a good way to enhance the prediction accuracy and simplify the model in NIR region.

Algorithms↗
PubMed1995

A pilot programme of external quality assessment for general haematology in Italy.

In the years 1984-1989 the Istituto Superiore di Sanità organized an EQAS for haematology (SVEQE) in Italy. A series of trials for haemocytometry, abnormal haemoglobins, HbA2, HbF, red cell G6PD and peripheral blood films, were carried out with the participation of 126 hospital laboratories, in different regions. SVEQE was an educative programme, aiming at promotion of quality assurance (QA) in laboratory haematology. At the same time an attempt was made to survey the analytical methods and instruments and to estimate the "state of the art" by the dispersion of all results. Participant laboratories were not scored for their performances. The operative protocol was harmonized to the guidelines established by WHO and ICSH; the trial specimens were prepared from normal or pathologic blood samples provided by blood banks or hospital departments. The trials for haemocytometry demonstrated a wide use of completely automated analyzers and in a steady state of performance during about five years. CVs, mainly for WBV and PLT, were somewhat higher than in other countries, where national QA systems have been established for a long time. Such discrepancies were not surprising in a pilot programme and were likely to be caused by inadequate internal quality control. The exercises for abnormal haemoglobins, HbA2, HbF and G6PD pointed out the need of using standardized methods according to the recommendations of ICSH. A large number of participating laboratories took part in the trial for blood cell morphology, being convinced of the educative function of this exercise; it is important to continue with systematic surveys, even including rare haematological disorders amongst the selected cases.

Hematologic Tests↗
PubMed1996

FIOH external quality assurance scheme for organic solvent metabolites.

The scheme consists of analyses for phenol,2,5-hexanedione, and mandelic, trichloroacetic and methylhippuric acids in urine. The present participants are 31 laboratories from 14 countries. Samples are prepared by pooling urine obtained from occupationally exposed workers or by spiking with appropriate pure metabolites. Four sets of samples at two concentration levels for each analyte are distributed annually. The report includes information on the arithmetic means, standard deviations and CVs for overall results and separately for different methods. During the last three years, the CVs have varied rather non systematically, being 21-31% for mandelic acid, 24-26% for trichloroacetic acid, 24-35% for phenol, 55-110% for 2,5-hexanedione and 44-50% for methylhippuric acid.

Environmental Monitoring↗
PubMed2005

Separation of proteins with a molecular mass difference of 2 kDa utilizing preparative double-inverted gradient polyacrylamide gel electrophoresis under nonreducing conditions: application to the isolation of 24 kDa human growth hormone.

A method for separating proteins with a molecular mass difference of 2 kDa using SDS-PAGE under nonreducing conditions is presented. A sample mixture containing several human growth hormone (hGH) isoforms was initially separated on a weak anion-exchange column. Fractions rich in 24 kDa hGH as determined by analytical SDS-PAGE were pooled and further separated by cation-exchange chromatography. The fractions pooled from the cation-exchange chromatography contained two hGH isoforms with a 2 kDa molecular mass difference according to SDS-PAGE analysis, 22 and 24 kDa hGH. The 22 and 24 kDa hGH were separated using continuous-elution preparative double-inverted gradient PAGE (PDG-PAGE) under nonreducing conditions. The preparative electrophoresis gel was composed of three stacked tubular polyacrylamide matrices, a 4% stacking gel, a 13-18% linear gradient gel, and a 15-10% linear inverted gradient gel. Fractions containing purified 24 kDa hGH were pooled and Western blot analysis displayed immunoreactivity to antihGH antibodies. PDG-PAGE provides researchers with an electrophoretic technique to preparatively purify proteins under nonreducing conditions with molecular mass differences of 2 kDa.

Chromatography↗
PubMed2000

The use of nuclear magnetic resonance spectroscopy in the detection of drug intoxication.

The use of nuclear magnetic resonance (NMR) spectroscopy as a method for drug analysis has the advantages of reduced pre-analytical preparation time and the potential to detect and quantitate drug conjugates and metabolites simultaneously. NMR was investigated as a method to screen for organic substances (and metabolites) in 25 patients who presented to the Emergency Department with clinical indications of a drug overdose. Urine specimens were examined by 1H NMR spectroscopy at 300 MHz and the results compared with gas chromatography-mass spectrometry (GC-MS) results. There was a 56% concordance (14 of 25 samples) between NMR and GC-MS. NMR identified acetaminophen, ibuprofen, aspirin, valproate, carbamazepine, and pseudoephedrine as parent compounds or metabolites. For a patient for whom GC-MS results were negative, NMR strongly suggested the presence of erythromycin. NMR was most successful in identifying analgesics and antiepileptic drugs (sensitivity 83-100%). In 10 patients, signals from 1,2-propanediol, a common vehicle for some pediatric medications, were observed by NMR spectroscopy. NMR had 0% sensitivity in identifying tricyclic antidepressants and antipsychotic drugs. In these samples, GC-MS detected a variety of compounds, including tricyclic antidepressants and their metabolites and chlorpromazine. In addition, other substances that had not been disclosed as having been ingested, such as caffeine, diphenhydramine, and nicotine, were detected by GC-MS. NMR spectroscopy represents an emerging supplementary analytical technique that is applicable to a wide range of possible intoxicants and to the evaluation of the intoxicated patient, particularly when larger amounts of the intoxicant (> 200 mg) are ingested.

Adolescent↗
PubMed1999

Chromatographic separation of carotenoids.

The carotenoids are extremely reactive and consequently unstable due to their long system of conjugated double bonds. Several precautions, such as protection against light and oxygen, use of low temperature and antioxidants, analysis in the shortest possible time, should be taken during isolation and chromatography. The food samples, preferably fresh, are homogenized and immediately extracted with a suitable organic solvent. Saponification has been employed in order to hydrolyze the carotenoid esters, remove fatty material and destroy chlorophyll. This optional step facilitates subsequent carotenoid separation, identification and quantification. The separation of carotenoids is usually carried out by column chromatography, thin layer chromatography and high performance liquid chromatography, in analytical or preparative scale, on many stationary phases such as silica-gel, alumina, MgO, Ca(OH)2 and reversed-phase material (C18 and C30). The choice of the most suitable chromatographic method depends on the amount of sample, carotenoid composition, resolution, speed and purity required. Examples of carotenoid separation in different stationary phases will be shown and discussed.

Carotenoids↗