Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Analytic Sample Preparation Methods”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources
PubMed2005

Sensitive liquid chromatography-tandem mass spectrometry method for the determination of scutellarin in human plasma: Application to a pharmacokinetic study.

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for the determination of scutellarin in human plasma has been developed. Samples were prepared using solid phase extraction and analyzed on a C(18) column interfaced with a triple quadrupole tandem mass spectrometer. Positive electrospray ionization was employed as the ionization source. The mobile phase consisted of methanol-water (0.1% formic acid), using gradient procedure. The analyte and internal standard baicalin were both detected by use of selected reaction monitoring mode. The method was linear in the concentration range of 0.2-20.0 ng/mL. The lower limit of quantification (LLOQ) was 0.2 ng/mL. The intra- and inter-day relative standard deviation across three validation runs over the entire concentration range was less than 12.4%. The accuracy determined at three concentrations (1.0, 5.0 and 10.0 ng/mL for scutellarin) was within +/-5.0% in terms of relative error. The method herein described was successfully applied for the evaluation of pharmacokinetic profiles of scutellarin guttate pills in 20 healthy volunteers.

Apigenin↗
PubMed1993

Sample cleanup by solid-phase extraction for the ultratrace determination of polychlorinated dibenzo-p-dioxins and dibenzofurans in biological samples.

A sample cleanup method for the isolation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) by solid-phase extraction is described. A C18 bonded silica cartridge is used for the initial extraction and enrichment of the analytes. Subsequent cleanup is achieved with a dual-cartridge arrangement consisting of a bonded benzenesulfonic acid cartridge in series with a silica cartridge. A Florisil cartridge is employed for the final cleanup step. Sample preparation procedures used for blood plasma and animal tissues are described. The precision and accuracy of the method is validated by determining recoveries of 2,3,7,8-substituted PCDD and PCDF congeners spiked at various levels in blood plasma and in animal tissues. The effectiveness of the cleanup method is shown by the analysis of wild bird eggs which are highly contaminated with a variety of pesticides and polychlorinated biphenyls. The application of this cleanup method to human plasma containing PCDDs/PCDFs at parts-per-quadrillion levels and results of analyses by high-resolution mass spectrometry and low-resolution mass spectrometry are presented. The validity of this method is demonstrated by the comparable results obtained from this method and from other established methods.

Animals↗
PubMed2000

Determination of amobarbital and secobarbital in plasma samples using micellar liquid chromatography.

A new liquid chromatographic procedure for the determination of amobarbital and secobarbital in plasma samples is proposed. The method uses a Spherisorb octadecylsilane ODS-2 C(18) analytical column, a guard column of similar characteristics and 0.04 M CTAB solution buffered at pH 7.5 containing 3% 1-propanol as micellar mobile phase. The UV detection was carried out at 250 nm. Butabarbital was used as internal standard. Plasma samples preparation only required adequate dilution with the mobile phase before injection into the chromatographic system. The limits of detection were 0.2 and 0.4 mg/L for amobarbital and secobarbital, respectively. The proposed method allows the determination of amobarbital and secobarbital in plasma at therapeutic levels.

Amobarbital↗
PubMed1992

Determination of Zy 17617B in plasma by solid-phase extraction and liquid chromatography with automated pre-column exchange.

An automated chromatographic system, combining solid-phase extraction and automated pre-column exchange, is described for the routine determination of Zy 17617B at the pmol/ml level in human plasma. The sample extraction and elution onto the analytical column were performed automatically and concomitantly using a conventional liquid chromatographic apparatus equipped with a Merck OSP-2 on-line sample preparator. Validation data demonstrate the reliability of the method.

Antidiarrheals↗
PubMed2006

State of the art in hair analysis for detection of drug and alcohol abuse.

Hair differs from other materials used for toxicological analysis because of its unique ability to serve as a long-term storage of foreign substances with respect to the temporal appearance in blood. Over the last 20 years, hair testing has gained increasing attention and recognition for the retrospective investigation of chronic drug abuse as well as intentional or unintentional poisoning. In this paper, we review the physiological basics of hair growth, mechanisms of substance incorporation, analytical methods, result interpretation and practical applications of hair analysis for drugs and other organic substances. Improved chromatographic-mass spectrometric techniques with increased selectivity and sensitivity and new methods of sample preparation have improved detection limits from the ng/mg range to below pg/mg. These technical advances have substantially enhanced the ability to detect numerous drugs and other poisons in hair. For example, it was possible to detect previous administration of a single very low dose in drug-facilitated crimes. In addition to its potential application in large scale workplace drug testing and driving ability examination, hair analysis is also used for detection of gestational drug exposure, cases of criminal liability of drug addicts, diagnosis of chronic intoxication and in postmortem toxicology. Hair has only limited relevance in therapy compliance control. Fatty acid ethyl esters and ethyl glucuronide in hair have proven to be suitable markers for alcohol abuse. Hair analysis for drugs is, however, not a simple routine procedure and needs substantial guidelines throughout the testing process, i.e., from sample collection to results interpretation.

Alcohols↗
PubMed2006

Microemulsion mediated in situ derivatization-extraction and gas chromatography-mass spectrometric analysis of alkylphosphonic acids.

Detection and identification of environmental signatures of chemical warfare agents is an important aspect of verification program of Chemical Weapons Convention (CWC). Alkylphosphonic acids (APAs) are ultimate and persistent degradation products of nerve agents. Their identification in a sample submitted for off-site analysis infers possible indication of contamination with nerve agents. This paper describes the development of a new sample preparation method which involves 'in situ derivatization and extraction' (INDEX) of acids from water. Derivatization is performed by alkylation of APAs with alkylbromides in surfactant less microemulsion (SLME). The derivatized analytes were analyzed by gas chromatography coupled with mass spectrometry. The developed method involves simultaneous derivatization (alkylation) and extraction of acidic analytes mediated by surfactant less microemulsion. Various derivatization-extraction parameters such as solvent, reaction time and temperature, base and alkyl bromides were optimized. Pentyl bromide in the presence of potassium carbonate and diisopropylamine at 100 degrees C derivatized the selected acids efficiently. Kinetic data for alkylation of methylphosphonic acids and some carboxylic acids were obtained to assess their relative susceptibility for alkylation in microemulsion. Methylphosphonic acid and isopropyl methylphosphonic acid took 140-150 min to reach completion while carboxylic acids took 100 min to complete the reaction. INDEX could be successfully performed even in the presence of interfering Ca(2+) and Mg(2+) ions.

Calibration↗
PubMed1986

High-performance liquid chromatographic method for the determination of etoposide in plasma using electrochemical detection.

A quantitative analytical method has been established for the determination of a semi-synthetic epipodophyllotoxin, etoposide, in plasma. The method employs reversed-phase high-performance liquid chromatography and electrochemical detection. Sample preparation consisted of extraction with 1,2-dichloroethane followed by phase separation, evaporation of the organic phase, and reconstitution of the residue. Observed recoveries were 76.8 and 87.5% for 50 and 500 ng/ml, respectively. The method had a linear range of 10-1000 ng/ml. Correlation coefficients of 0.997 or greater were obtained during validation experiments and study sample analysis.

Chromatography, High Pressure Liquid↗
PubMed1997

Comparative analysis of conjugated bile acids in human serum using high-performance liquid chromatography and capillary electrophoresis.

This paper describes the analysis of conjugated bile acids in human serum using reversed-phase high-performance liquid chromatography (HPLC) and micellar electrokinetic capillary electrophoresis (CE). Samples of healthy subjects and patients with different hepatic diseases were pretreated with a simple preparation procedure using a solid-phase extraction technique. The optimal analytical conditions of both chromatographic methods were investigated for the convenience and reliability for routine analysis. Both HPLC and CE methods were found to be reliable and compatible. The recoveries of nine bile acid conjugates using both methods were generally >85% and reproducibility >90%. The day-to-day variation of retention time was <5% for HPLC, while the variation of migration time for CE was <3%. Although the detection limit of the HPLC method (1 nmol/ml) was five times more sensitive than that of the CE method, the CE method was considered to be more time and cost effective.

Bile Acids and Salts↗
PubMed1998

Headspace solid-phase microextraction and gas chromatographic determination of dinitroaniline herbicides in human blood, urine and environmental water.

Solid-phase microextraction (SPME) is a unique extraction and sampling technique, and it has been used for separation of volatile organics from water or other simple matrices. In this study, we have used SPME to separate dinitroaniline herbicides from complicated matrices of human urine and blood in order to broaden its application to biomedical analysis. The SPME conditions were optimized for water, urine and blood samples, in terms of pH, salt additives, extraction temperature, and fiber exposure time. Urine or water (1.0 ml) spiked with herbicides and 0.28 g of anhydrous sodium sulfate was preheated at 70 degrees C for 10 min, and a polydimethylsiloxane-coated fiber for SPME was exposed to the headspace at 70 degrees C for another 30 min; while spiked blood (0.5 ml) diluted with water (0.5 ml) was treated at 90 degrees C in the same way. The herbicides were extractable under these conditions, and could be determined by gas chromatography-electron capture detector (GC-ECD). The recoveries of the herbicides, measured at the concentrations of 0.50 and 1.0 ng/ml urine or water, or 6.0 and 20 ng/0.5 ml blood, ranged from 35 to 64% for different herbicides from water or urine, and from 3.2 to 7.2% from blood. The headspace SPME yielded clean extracts of dinitroaniline herbicides from urine, blood or water, which could be directly analyzed by GC-ECD without further purification. The peak areas of the extracted herbicides were proportional to their concentrations in the range 0.1-10 ng/ml in water or urine, or 1-60 ng/0.5 ml in blood. The lowest detectable concentration of the herbicides lay in 0.1 ng/ml water or urine, or in 0.5 ng/0.5 ml blood. The intra- and inter-day coefficients of variation were within 14% for most of the analytes. Although the recoveries of the herbicides were rather low, the linearity of calibration curve and the precision were good. The developed method is more sensitive and much simpler in sample preparation than previously reported ones. With the established SPME method, a dosed herbicide was successfully separated and determined in rats' blood.

Aniline Compounds↗
PubMed2005

Desorption electrospray ionization of explosives on surfaces: sensitivity and selectivity enhancement by reactive desorption electrospray ionization.

Desorption electrospray ionization (DESI), an ambient mass spectrometry technique, is used for trace detection of the explosives trinitrohexahydro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 2,4,6-trinitrotoluene (TNT), Pentaerythritol tetranitrate (PETN), and their plastic compositions (Composition C-4, Semtex-H, Detasheet) directly from a wide variety of surfaces (metal, plastic, paper, polymer) without sample preparation or pretreatment. Analysis of the explosives is performed under ambient conditions from virtually any surface in very short times (<5 s) including confirmatory tandem mass spectrometry (MS/MS) experiments, while retaining the sensitivity and specificity that mass spectrometry offers. Increased selectivity is obtained both by MS/MS and by performing additional experiments in which additives are included in the spray solvent. These reactive DESI experiments (reactions accompanying desorption) produce such ions as the chloride and trifluoroacetate adducts of RDX and HMX or the Meisenheimer complex of TNT. Desorption atmospheric pressure chemical ionization, a variant of DESI that uses gas-phase ions generated by atmospheric pressure corona discharges of toluene or other organic compounds, provides evidence for a heterogeneous-phase (gaseous ion/absorbed analyte) charge-transfer mechanism of DESI ionization in the case of explosives. Plastic explosives on surfaces were analyzed directly as fingerprints, without sample preparation, to test DESI as a possible method for in situ detection of explosives-contaminated surfaces. DESI also allowed detection of explosives in complex matrixes, including lubricants, household cleaners, vinegar, and diesel fuel. Absolute limits of detection for the neat explosives were subnanogram in all cases and subpicogram in the case of TNT. The DESI response was linear over 3 orders of magnitude for TNT. Quantification of RDX on paper gave a precision (RSD) of 2.3%. Pure water could be used as the spray solution for DESI, and it showed ionization efficiencies for RDX in the negative ion mode similar to that given by methanol/water. DESI represents a simple and rapid way to detect explosives in situ with high sensitivity and specificity and is especially useful when they are present in complex mixtures or in trace amounts on ordinary environmental surfaces.

Journal Article↗
PubMed1997

Environmental and human monitoring of Americium-241 utilizing extraction chromatography and alpha-spectrometry.

Recent developments in extraction chromatography have simplified the separation of americium from complex matrices in preparation for alpha-spectroscopy relative to traditional methods. Here we present results of procedures developed/adapted for water, air, and bioassay samples with less than 1 g of inorganic residue. Prior analytical methods required the use of a complex, multistage procedure for separation of americium from these matrices. The newer, simplified procedure requires only a single 2 mL extraction chromatographic separation for isolation of Am and lanthanides from other components of the sample. This method has been implemented on an extensive variety of "real" environmental and bioassay samples from the Los Alamos area, and consistently reliable and accurate results with appropriate detection limits have been obtained. The new method increases analytical throughput by a factor of approximately 2 and decreases environmental hazards from acid and mixed-waste generation relative to the prior technique. Analytical accuracy, reproducibility, and reliability are also significantly improved over the more complex and laborious method used previously.

Americium↗
PubMed1980

Preparative and quantitative isolation of plasma lipoproteins: rapid, single discontinuous density gradient ultracentrifugation in a vertical rotor.

A rapid method has been developed for separation of the major plasma lipoproteins from up to 96 ml of plasma by a single ultracentrifugation step. This separation was achieved by a discontinuous density gradient centrifugation between the density range of 1.006 and 1.30 g/ml in Sorvall vertical rotors. Each lipoprotein fraction was sharply banded with VLDL at the top, LDL in the upper middle, and HDL in the lower middle portion of the tube. Use of authentic 125I-labeled lipoproteins showed that complete separation of the three major classes and partial separation of HDL2 and HDL3 was achieved. The lipoprotein fractions prepared by this technique have properties indistinguishable from those isolated by the sequential flotation method in regard to their equilibrium banding density, electrophoretic mobility, and apolipoprotein composition. This method is suitable for the preparative isolation of lipoproteins as well as for quantitative clinical determinations of cholesterol and triglycerides in VLDL, LDL and HDL fractions of plasma. Used as an analytical tool this method allows samples as small as 1 ml of plasma and spin times as short as 45 min. Cholesterol levels in HDL fractions separated by this method have significantly lower values (P less than 0.05) than those estimated by the heparin-manganese chloride precipitation method.

Centrifugation, Density Gradient↗
PubMedDate not supplied

Determination of calcium by inductively coupled plasma-atomic emission spectrometry, and lead by graphite furnace atomic absorption spectrometry, in calcium supplements after microwave dissolution or dry-ash digestion: method trial.

A 3-laboratory method trial was conducted to evaluate 2 sample digestion procedures and instrumental determination parameters for analysis of calcium and lead in Ca supplements. Calcium supplements were treated by dry-ash digestion or microwave dissolution prior to spectrometric analysis. In each case, Pb was determined by graphite furnace atomic absorption spectrometry and Ca by inductively coupled plasma-atomic emission spectrometry. Blind duplicates of 6 Ca supplement samples were analyzed after each sample treatment procedure. Matrix pairs contained dissimilar Pb levels to cover the analyte range encountered during method development. Calcium content of the Ca supplement samples also reflected the range seen during method development. Stock solutions of Ca and Pb were supplied to collaborators for preparation of quantitation standards to remove a variable external to the method. National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1486, bone meal, was included to assess method accuracy and recovery at NIST certificate Ca and Pb levels for this material (26.58 +/- 0.24% Ca and 1.335 +/- 0.014 micrograms Pb/g). Analyses of the NIST SRM yielded 25.9 +/- 1.1 and 27.2 +/- 2.3% Ca and 1.53 +/- 0.19 and 1.26 +/- 0.19 micrograms Pb/g for dry-ash and microwave procedures, respectively. Statistical analyses of data indicated acceptable repeatability and reproducibility for determination of Pb and Ca in various Ca supplements. With either sample preparation technique, the method is appropriate for determining Pb or Ca in Ca supplements.

Biological Products↗
PubMed2003

A comparative study of the correction of systematic errors in the quantitation of pyrethroids in vegetables using calibration curves prepared using standards in pure solvent.

A comparative study of two mathematical approaches was performed in order to correct systematic errors due to the presence of the unexpected interferences which appear when the quantitation of the analyte in real samples is carried out with calibration curves built using standards in pure solvent. These methods consisted in the establishment of different mathematical expressions which transform the concentration (Cs) obtained using calibration graphs built using pure solvent into the corrected concentration (C(M)) that should be obtained if the quantitation is carried out with calibration curves built using standards dissolved in blank matrix extracts. In the two approaches the correction is performed from the results of an intermediate precision study which was carried out using both calibration graphs (prepared using pure solvent and blank matrix extract). By using ANCOVA to compare the slope of both solvent-based and matrix-matched calibration graphs, matrix effect was found in the determination of deltamethrin in tomato and acrinathrin in tomato and pepper. In these cases, both approaches led to good results.

Calibration↗
PubMed2006

[Near infrared spectrometry (NIRS) method for the determination of borneol in sustained-release drugs].

In order to detect the release profile of borneol in sustained-release preparations, a series of NIRS calibration models were established on the basis of chemometrics and internal relationships between NIRS and analytical concentrations of samples, which contained the same substances as the preparations. Partial least square (PLS) algorithm was used to establish the model for predicting the content of borneol. The effect of spectra types, concentration range of samples, and calibration range on the models and predicting results were investigated. It was found that the best calibration models and prediction results can be obtained by using original spectra in the 5,314-7,032 cm(-1) region. The models established according to standards' concentration levels are better than those established without considering concentration levels. Using the model 2 in which calibration standards had medium or high concentration levels, rapid and accurate measurement of borneol released from sustained-release preparation was realized. The results indicated that the method and models provide valuable criteria for developing sustained-release borneol preparations.

Camphanes↗
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↗
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↗
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↗