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At least 685 records · Page 38Linked to original sources
PubMed2004

Validation of a confirmatory method for the determination of sulphonamides in muscle according to the European Union regulation 2002/657/EC.

A simple multiresidue method is described for assaying 10 sulphonamides (SAs) (sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethazine, sulfamonomethoxine, sulfachlorpyridazine, sulfamethoxazole, sulfaquinoxaline and sulfadimethoxine) in muscle samples. Samples were prepared by homogenizing the tissue, extracting with ethyl acetate and cleaning up with a cation-exchange solid-phase extraction (SPE) column. The detection of analytes was achieved by HPLC-diode array detection (DAD) at 270 nm. The procedure was validated according to the European Union regulation 2002/657/EC determining specificity, decision limit, detection capability, trueness and precision. The results of validation process demonstrate that the method is suitable for application in European Union statutory veterinary drug residue surveillance programmes.

Animals↗
PubMed2000

High accuracy isotope dilution analysis for the determination of ethanol using gas chromatography-combustion-isotope ratio mass spectrometry.

A procedure was established for the determination of ethanol in water samples by isotope dilution analysis. After spiking the sample with labelled [13C2]ethanol, it was analysed by gas chromatography-combustion-isotope ratio mass spectrometry. Results are reported for two certified reference materials and also ethanol solutions prepared for a CITAC (Co-operation on International Traceability in Analytical Chemistry) interlaboratory comparison. The certified reference materials were certified using the dichromate titration method at nominal levels of 80 and 200 mg per 100 mL. The CITAC solutions were prepared gravimetrically at nominal levels of 50, 80 and 200 mg per 100 mL. The results of the analysis agree well to within 0.5% of the gravimetric values of the different samples. The relative expanded standard uncertainties (with a coverage factor equal to 2) associated with the results varied between 0.18 and 0.37%, a range that encompassed the gravimetric values for the different samples. A complete uncertainty budget was also drawn up so that the different contributions could be identified and quantified. The main contributions were due to variations in the measured isotope amount ratios and a 'between' blend component introduced to quantify the contribution of factors such as the degree of matching of the isotope amount ratios between standards and samples used in the isotope dilution analysis.

Journal Article↗
PubMed1984

Nondestructive optical methods of food quality evaluation.

Quality control is an important aspect of food production and processing from the point of view of providing foods of acceptable nutritional value, and for providing safety of products. Several characteristics such as size, shape, density, maturity, moisture content, oil content, flavor, firmness, tenderness, color, defects, blemishes, etc., are routinely used in the quality control of agricultural and biological food products. Until recently, most analytical techniques used in quality control required isolation of the food component of interest. The original properties of the product are, therefore, destroyed during sample preparation and analysis. Oftentimes, such analyses are expensive, time consuming, and require sophisticated instrumentation, and hence are not suited for "on-line" quality control of food products. Recent progress in the development of instrumentation utilizing the optical properties of food products has provided several nondestructive techniques for quality evaluation. Most optical methods of nondestructive nature make use of the characteristic absorption spectra of components of interest. Such methods are highly sensitive, rapid, and reproducible, and have been successively used in routine "on-line" quality control of a large number of samples. In this article, theoretical considerations in the development of nondestructive analytical techniques based on the optical properties of several agricultural and biological products are briefly reviewed. A major emphasis is placed on quality control methods that are particularly useful in maturity and/or ripeness evaluation of food products, the detection of external and internal defects, and the subsequent development of automatic sorting machines for on-line measurement of quality.

Food↗
PubMed2005

An infrared spectroscopic method for quantitative analysis of fatty alcohols and fatty acid esters in machinery oils.

A new infrared spectroscopic method suitable for determining total fatty alcohol and fatty acid ester concentrations in industrial oils has been developed. Oil samples were diluted with toluene (1:3 w/w), the toxicity and volatility of which are relatively low compared with more commonly used IR solvents, like carbon tetrachloride or carbon disulfide. Mixture standards were prepared from dodecanol, tetradecanol, octadecanol, methyl stearate and methyl palmitate. Some analytical and statistical tests were performed on the developed method. The recoveries and the repeatability of the method proved to be sufficient for the quantitative determination of fatty alcohol and fatty acid ester additives in industrial oils. Reproducibility testing in another laboratory also produced satisfactory results. The developed method also proved to be relatively quick and simple. This method was developed to satisfy industry's need to determine the concentrations of these oil additives, and it has already been applied successfully in machinery oil analysis.

Carbon Disulfide↗
PubMed1993

Stereoselective determination of the active metabolites of a new anti-inflammatory agent (CS-670) in human and rat plasma using antibody-mediated extraction and high-performance liquid chromatography.

The main metabolites of (+-)-2-[4-(2-oxocyclohexylidenemethyl)phenyl]propionic acid (CS-670), a new pro-drug anti-inflammatory agent of the 2-arylpropionic acid type, have one or two chiral centres arising from reduction of the oxocyclohexylidene moiety in addition to an original chiral centre in the propionic acid moiety. To determine these metabolites stereoselectively, antibody-mediated extraction was investigated as a stereoselective clean-up method prior to chiral HPLC. Immunoglobulin G, which recognizes each stereoisomeric cyclohexanol moiety, was coupled to cyanogen bromide-activated Sepharose 4B to prepare re-usable immobilized antibody, and its specificity was improved by examination of a washing process after charging of samples. Plasma extracted with the immobilized antibody column was derivatized with a chiral reagent to separate the enantiomers of the propionic acid moiety by HPLC. This newly developed analytical method clarified the stereoselective biotransformation of the pro-drug to pharmacologically active forms in humans and rats related to reduction of the oxocyclohexylidene moiety and chiral inversion in the propionic acid moiety.

Animals↗
PubMedDate not supplied

Determination of verapamil and norverapamil in human plasma by liquid chromatography: comparison between a liquid-liquid extraction procedure and an automated liquid-solid extraction method for sample preparation.

A conventional liquid-liquid extraction (LLE) procedure with high-performance liquid chromatography (HPLC) has been developed for the determination of verapamil and its main metabolite, norverapamil, in plasma. After addition of the internal standard, plasma samples were basified with phosphate buffer (pH 9.0) and extracted with a mixture of cyclohexane-dichloromethane. After centrifugation, the organic layer was separated and the analytes were extracted back into a 0.1 N sulphuric acid solution containing 2-aminoheptane. An aliquot of this aqueous phase was then injected directly onto the HPLC column. This LLE procedure has been compared with an automated liquid-solid extraction (LSE) method that has been developed in parallel. Good linearity was obtained using both extraction methods. The absolute recoveries for the two analytes were ca 95% with the automated LSE procedure and slightly lower (ca 84%) for the LLE method. The automated method gives better results with respect to detectability and precision, but the LLE procedure is simpler to develop, requires much less expensive equipment, and remains a useful alternative when the number of samples to be analysed is limited.

Buffers↗
PubMed2006

Optimization of paper bridge loading for 2-DE analysis in the basic pH region: application to the mitochondrial subproteome.

Separation of basic proteins with 2-DE presents technical challenges involving protein precipitation, load limitations, and streaking. Cardiac mitochondria are enriched in basic proteins and difficult to resolve by 2-DE. We investigated two methods, cup and paper bridge, for sample loading of this subproteome into the basic range (pH 6-11) gels. Paper bridge loading consistently produced improved resolution of both analytical and preparative protein loads. A unique benefit of this technique is that proteins retained in the paper bridge after loading basic gels can be reloaded onto lower pH gradients (pH 4-7), allowing valued samples to be analyzed on multiple pH ranges.

Animals↗
PubMed2002

Identification of 1-hydroxypyrene glucuronide in tissue of marine polychaete Nereis diversicolor by liquid chromatography/ion trap multiple mass spectrometry.

1-Hydroxypyrene glucuronide is identified as the single major aqueous metabolite of the tetracyclic aromatic hydrocarbon pyrene, in tissue from a deposit-feeding marine polychaete, Nereis diversicolor. Identification was performed using an ion trap mass spectrometer fitted with an atmospheric pressure chemical ionization (APCI) probe and connected to a high-performance liquid chromatography/diode array detector (HPLC/DAD) system. Besides 1-hydroxypyrene, the 339-nm UV trace of tissue samples from pyrene-exposed worms showed only one dominant peak that could be related to pyrene metabolism. Negative APCI-MS of this supposed 1- hydroxypyrene conjugate gave a characteristic signal at m/z 429 corresponding to the molecular ion of 1-hydroxypyrene glucuronide plus eluent adducts ([M - H + 2H(2)O](-)). Fragmentation pathways were studied by isolating the abundant ion at m/z 429 in the ion trap and performing multiple mass spectrometric experiments (MS(n)). The fragmentations observed were consistent with the proposed identification. Two low intensity LC peaks that could be related to pyrene metabolism by their DAD absorption spectra were also present in the 339-nm UV chromatogram of tissue samples. However, these peaks could not be identified by their mass spectra in negative ion mode due to ion suppression by very abundant co-eluting impurities. The present method shows that LC/MS(n) is a fast and useful analytical tool for identification of aqueous polycyclic aromatic hydrocarbon biotransformation products in samples from relatively small marine invertebrates with limited sample preparation.

Animals↗
PubMed2006

Matrix solid phase dispersion (MSPD).

A review of the many uses of matrix solid phase dispersion (MSPD) in the extraction and analysis of a variety of compounds from a range of samples is provided. Matrix solid phase dispersion (MSPD) has found particular application as a somewhat generic analytical process for the preparation, extraction and fractionation of solid, semi-solid and/or highly viscous biological samples. Its simplicity and flexibility contribute to it being chosen over more classical methods for these purposes. MSPD is based on several simple principles of chemistry and physics, involving forces applied to the sample by mechanical blending to produce complete sample disruption and the interactions of the sample matrix with a solid support bonded-phase (SPE) or the surface chemistry of other solid support materials. These principles are discussed as are the factors to be considered in conducting a MSPD extraction.

Solid Phase Extraction↗
PubMed2002

Detection of explosives and their degradation products in soil environments.

Polynitro organic explosives [hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6-trinitrotoluene (TNT)] are typical labile environmental pollutants that can biotransform with soil indigenous microorganisms, photodegrade by sunlight and migrate through subsurface soil to cause groundwater contamination. To be able to determine the type and concentration of explosives and their (bio)transformation products in different soil environments, a comprehensive analytical methodology of sample preparation, separation and detection is thus required. The present paper describes the use of supercritical carbon dioxide (SC-CO2), acetonitrile (MeCN) (US Environmental Protection Agency Method 8330) and solid-phase microextraction (SPME) for the extraction of explosives and their degradation products from various water, soil and plant tissue samples for subsequent analysis by either HPLC-UV, capillary electrophoresis (CE-UV) or GC-MS. Contaminated surface and subsurface soil and groundwater were collected from either a TNT manufacturing facility or an anti-tank firing range. Plant tissue samples were taken fromplants grown in anti-tank firing range soil in a greenhouse experiment. All tested soil and groundwater samples from the former TNT manufacturing plant were found to contain TNT and some of its amino reduced and partially denitrated products. Their concentrations as determined by SPME-GC-MS and LC-UV depended on the location of sampling at the site. In the case of plant tissues, SC-CO2 extraction followed by CE-UV analysis showed only the presence of HMX. The concentrations of HMX (<200 mg/kg) as determined by supercritical fluid extraction (SC-CO2)-CE-UV were comparable to those obtained by MeCN extraction, although the latter technique was found to be more efficient at higher concentrations (>300 mg/kg). Modifiers such as MeCN and water enhanced the SC-CO2 extractability of HMX from plant tissues.

Azocines↗
PubMed2001

Analysis of sweet diterpene glycosides from Stevia rebaudiana: improved HPLC method.

An improved analytical method was developed which may be applied to quality control of stevioside and rebaudioside A contents in dried leaves of Stevia rebaudiana before processing; in a selective sampling program searching for plants of higher yield in diterpene glycosides content; or when a large number of samples are sent to the laboratory for analysis. The procedure developed involves two steps: solvent extraction followed by an isocratic HPLC analysis. The sample, 1 g of dried leaves of S. rebaudiana, is ground and solvent-extracted with EtOH 70% (w/w) in Erlenmeyer flasks by shaking for 30 min in a 70 degrees C water bath. After the extract was cooled, it was filtered and analyzed by HPLC using an NH(2) column (250 x 4.6 mm) and a mixture of acetonitrile/water (80:20, v/v) as mobile phase, pH 5 adjusted with acetic acid. The detection was in the UV range at 210 nm (0.04 AUFS). Quantitation was performed by means of an external standard calibration curve for each analyte which had been obtained from standard solutions of pure stevioside and rebaudioside A. Working under these conditions there were no observed interference effects. The method saves time in sample preparation, and reduces sample handling and chromatographic analysis time, while having little loss of precision [coefficient of variation (CV%) between 1.8% and 3.0%] and recovery [between 98.5% and 100.5%]. The method was applied to 30 samples of S. rebaudiana from Misiones (Northeastern Argentina), and the stevioside content found ranged between 3.78 and 9.75% (weight) whereas Rebaudioside A content ranged between 1.62 and 7.27% (weight).

Chromatography, High Pressure Liquid↗
PubMed2000

Measurement of food flavonoids by high-performance liquid chromatography: A review.

The flavonoids are plant polyphenols found frequently in fruits, vegetables, and grains. Divided into several subclasses, they include the anthocyanidins, pigments chiefly responsible for the red and blue colors in fruits, fruit juices, wines, and flowers; the catechins, concentrated in tea; the flavanones and flavanone glycosides, found in citrus and honey; and the flavones, flavonols, and flavonol glycosides, found in tea, fruits, vegetables, and honey. Known for their hydrogen-donating antioxidant activity as well as their ability to complex divalent transition metal cations, flavonoids are propitious to human health. Computer-controlled high-performance liquid chromatography (HPLC) has become the analytical method of choice. Many systems have been developed for the detection and quantification of flavonoids across one, two, or three subclasses. A summary of the various HPLC and sample preparation methods that have been employed to quantify individual flavonoids within a subclass or across several subclasses are tabulated in this review.

Anthocyanins↗
PubMed1997

[Discussion of the validation of thin-layer chromatographic procedure in pharmaceutical analysis].

TLC has become a convenient, fast, robust, and cost efficient technique in pharmaceutical analysis because of its coherent features. The important analytical performance parameters are summarized, such as accuracy, precision, reproducibility, specificity, detection limit, quantitation limit, linearity and range, etc. The validation methods and the acceptance criteria are discussed for sample preparation, sample stability in solution and on plate, sample exposure time, robustness and quality of stationary and mobile phases, application of sample to plate, spot dimension and shape, temperature, humidity and chamber saturation, detection, and quantitation, etc. It is recommended that the definition of the validation parameters and the validation procedures for quantitative TLC should be described whenever the results are reported.

Chromatography, Thin Layer↗
PubMed1983

[Methodological aspects of urinary enzymology].

Collection and storage of the sample exert significant influences on the results of urinary enzyme determinations. Enzymes with sufficient stability during urine collection and consecutive in vitro storage are probably best suited for diagnostic purposes. Sample preparation, e.g. by gel filtration of the urine should be performed to remove quantitatively interferences. Optimized methods for some urinary enzymes are now available offering a basis for standardization. Analytical results should be verified by the use of self-prepared or commercially available quality control materials. The modern clinical chemical technology permits the determination of enzyme activities in urine with a quality standard comparable to that in other body fluids. New approaches are the development of a dipstick test for beta-N-acetylglucosaminidase and the use of immunological techniques for the measurement of enzyme concentrations in urine.

Acetylglucosaminidase↗
PubMed1977

[Comparison of amino acids in human serum and plasma (author's transl)].

Using standardized analytical methods amino acids in human serum and plasma were compared. Identical concentrations of the studied amino acids are found in serum and plasma, which are prepared immediately after blood sampling. If protein precipitation is performed after storage of the serum sample at 4 degrees C or 22 degrees C for 10 or 24 hours, concentrations of some amino acids are significantly changed.

Adult↗
PubMed2006

Potentials of ion trap collisional spectrometry for liquid chromatography/electrospray ionization tandem mass spectrometry determination of buprenorphine and nor-buprenorphine in urine, blood and hair samples.

A liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method has been developed for the analysis of buprenorphine (BUP) and nor-buprenorphine (NBUP) in biological fluids. Analytes are isolated from urine and blood, after addition of d4-buprenorphine (d4-BUP) as internal standard, by solid-phase extraction. Preparation of hair involves external decontamination, mechanical pulverization, overnight incubation in acidic medium, and neutralization prior to extraction. Enzymatic hydrolysis with beta-glucuronidase may be performed to distinguish between free and total BUP. Chromatographic separation is accomplished by gradient elution on a cyanopropyl 2.1 x 150 mm column. Positive ion ESI and MS analyses are carried out in an ion trap mass spectrometer. The use of this mass analyzer allows effective collisional experiments to be performed on ESI-generated MH+ species. Abundant product ions are produced, which can be monitored together with precursor ions without losing sensitivity. Thus, assay selectivity is definitely increased with respect to LC/ESI-MS/MS methods in which only precursor ions are monitored. The method has good linearity (calibration curves were linear in the range 0.1-10 ng/mL in urine and blood, in the range 10-160 pg/mg in hair) and limits of detection of 0.05 ng/mL for both BUP and NBUP in blood and urine samples, of 4 pg/mg for both analytes in hair. Both intra- and inter-assay precision and accuracy were satisfactory at three concentrations studied: relative standard deviations were <13.7% in urine, <17.3% in blood, <17.8% in hair; percent deviation of the mean from the true value was always <10.5% in urine and blood, <16.1% in hair. The method can be used to determine both analytes in the urine and hair of drug addicts on replacement therapy, and in post-mortem blood specimens when there is suspicion of drug-related death.

Analgesics, Opioid↗
PubMed2006

Quantification of urinary zwitterionic organic acids using weak-anion exchange chromatography with tandem MS detection.

A rapid and accurate quantitative method was developed and validated for the analysis of four urinary organic acids with nitrogen containing functional groups, formiminoglutamic acid (FIGLU), pyroglutamic acid (PYRGLU), 5-hydroxyindoleacetic acid (5-HIAA), and 2-methylhippuric acid (2-METHIP) by liquid chromatography tandem mass spectrometry (LC/MS/MS). The chromatography was developed using a weak anion-exchange amino column that provided mixed-mode retention of the analytes. The elution gradient relied on changes in mobile phase pH over a concave gradient, without the use of counter-ions or concentrated salt buffers. A simple sample preparation was used, only requiring the dilution of urine prior to instrumental analysis. The method was validated based on linearity (r2>or=0.995), accuracy (85-115%), precision (C.V.<12%), sample preparation stability (<or=5%, 72 h), and established patient ranges. The method was found to be both efficient and accurate for the analysis of urinary zwitterionic organic acids.

Acids↗
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↗