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At least 703 records · Page 39Linked to original sources
PubMed2000

Improved RP-HPLC determination of quinine in plasma and whole blood stored on filter paper.

Analysis of quinine in plasma and whole blood samples dried on filter paper is described. Sample preparation involves liquid extraction of plasma and whole blood from the filter paper and subsequent solid-phase extraction using C8 Bond Elut cartridges. A reverse-phase liquid chromatography system with UV detection and fluorescence detection was used. The analytical characteristics of the method are reported, with a quantification limit of 0.1 microg mL(-1) and within an assay coefficient of variation of 5.6-8.4% in plasma and 6.5-12% in whole blood. Representative chromatograms are shown as a function of time for samples from human subjects after ingestion of a single 400-mg dose of quinine sulphate. Quinidine, dihydroquinine and metabolites are well separated from quinine with a resolution of above 1 (Rs>1).

Adult↗
PubMed1990

Analytical methodologies for the quantitation of platinum anti-cancer drugs and related compounds in biological media.

The methods for analysis of platinum-based anti-cancer drugs in biological media are reviewed in this paper. Although emphasis is placed on cisplatin, attention is also given to several of its analogues (carboplatin, iproplatin) and their degradation and biotransformation products. In an introductory section a short description is given of the historical background and the clinical applications of cisplatin. Reactions occurring in the body and in aqueous solutions are discussed because of their implications for the design of analytical procedures. After a detailed description of sample preparation and storage, attention is focussed on the analytical techniques used for the determination of either total platinum levels or individual platinum-containing compounds. The techniques discussed include atomic absorption and emission spectrometry, derivatization reactions and several chromatographic techniques with different detection methods. The specific advantages and disadvantages of these techniques are discussed.

Antineoplastic Agents↗
PubMed1999

Poisoning by plant material: review of human cases and analytical determination of main toxins by high-performance liquid chromatography-(tandem) mass spectrometry.

The authors have reviewed the main toxic plants responsible for human deaths throughout the world. Forty plants (genera or species) were listed in order to establish an inventory of the active molecules that could be identified, the already published analytical methods and the reported human fatal cases. In a second step, the authors have developed a general method for the detection of various toxins in whole blood by high-performance liquid chromatography coupled to mass spectrometry or tandem mass spectrometry. Sample preparation was realized by liquid-liquid extraction at pH 9.5 for oleandrine, taxol and the alkaloids. These latter compounds were divided into two groups following their chemical properties and could be subsequently purified by acid/base clean up. Cyanogenic compounds and atractyloside were isolated by precipitation of the protein content with acetone and purified for atractyloside by washing with chloroform. Separation of the drugs occurred under reversed-phase conditions on a C18 analytical column 150x2 mm I.D. (5 microm particle size) using two different mobile phases. The first one, formiate buffer 2 mM acidified at pH 3.0, was used for the separation of atractyloside, oleandrine, taxol, the cyanogenic molecules and some alkaloids. The second mobile phase, formiate buffer 10 mM made basic at pH 8.2 was used for the majority of other alkaloids. A gradient elution mode was chosen using acetonitrile or acetonitrile-methanol (50:50, v/v) as the eluting solvent. Detection under positive ionization mode was the mode of choice for all compounds except for atractyloside (negative ions) and for taxol (mixed mode available). Application to real forensic cases has been demonstrated.

Child↗
PubMed1990

Measurement of 2-deoxyglucose and 2-deoxyglucose 6-phosphate in tissues.

The enzymatic methods previously described for 2-deoxyglucose (DG) and 2-deoxyglucose 6-phosphate have been refined and adapted to measurements of brain samples ranging from 50 mg wet weight to less than a microgram dry weight. Procedures for preparing such samples for assay are described. Analytical properties of the enzymes employed are given together with means for overcoming their possible short comings. Emphasis is placed on information useful for employing DG to assess rapid changes in glucose metabolism.

Animals↗
PubMed2002

A HPLC assay for coating integrity of topiramate sprinkle formulation.

A HPLC method has been developed for the determination of coating integrity of topiramate sprinkle formulation. This method determines the completeness of the sprinkle coating and, indirectly, the completeness of taste masking of the product. This method utilizes a sample preparation where the sprinkles are placed in a specially designed stainless steel basket equipped with a screen, 25-mesh size, at the bottom. Water is used to solubilize any incompletely coated drug. The aqueous solution is analyzed for topiramate using a phenyl column in the reversed-phase mode, isocratic elution, and refractive index detection. This analytical method, for recovered topiramate, provides an indirect measure of drug taste-masking in the sprinkle formulation. It was also used in formulation selection by screening sprinkles beads that contained different amounts of coating to see which formula can best mask the taste with an acceptable level of exposed topiramate drug substance. This method has been validated to meet FDA validation guidelines.

Anticonvulsants↗
PubMed2004

Determination of fexofenadine in human plasma using 96-well solid phase extraction and HPLC with tandem mass spectrometric detection.

A fast and sensitive HPLC-MS/MS method, utilizing atmospheric pressure chemical ionization, for the determination of fexofenadine in human plasma is described. A deuterated analog, d6-fexofenadine is used as the internal standard (IS). Plasma samples are prepared using 96-well solid phase extraction with plates containing Waters Oasis HLB sorbent. The analytes are chromatographed on a Restek Ultra IBD column (3.2 mm x 50 mm, 3 microm) using a mobile phase consisting of a mixture of 90% acetonitrile and 10% 10 mM ammonium acetate buffer and 0.1% formic acid. Quantitation of the analyte is based on the response from the multiple reaction monitoring of the precursor to product ion pairs for fexofenadine (m/z 502 --> 466) and d6-fexofenadine (m/z 508 --> 472). The assay has been validated over the concentration range of 1-200 ng/ml based on the analysis of 0.5 ml aliquots of plasma. Within-day assay accuracy was between 97 and 102% of nominal, while within-day precision was better than 3.5% CV at all points on the standard curve. Analyte extraction recovery was better than 70% over the range of the standard curve. The method was found to be suitable for the analysis of human plasma samples obtained 24 h following the administration of a single 60 mg dose of fexofenadine.

Chromatography, High Pressure Liquid↗
PubMed2006

Analysis of trace amount of bank dye and lachrymators from exploding bank devices by solid-phase microextraction and gas chromatography-mass spectrometry.

Solid-phase microextraction (SPME) is a fast, solvent-free alternative to conventional sample preparation techniques. This technique involves exposing a fused silica fiber that has been coated with a stationary phase to an aqueous solution or its headspace to selectively extract compounds from their matrix. The fiber is then removed, and the analytes are thermally desorbed in the injector of a gas chromatograph. By sampling from the headspace above sample matrices, SPME can be used to extract target analytes from very complex matrices. In this study, SPME in the headspace is used in developing a method for the dye 1-methylaminoanthraquinone (MAAQ) and two lachrymators: orthochlorobenzalmalononitrile (CS) (tear gas) and 2-chloroacetophenone (CN) (tear gas). The focus is to develop a robust method to minimize sample preparation and to reduce matrix interferences encountered by other extraction techniques. In developing the method, several fibers are studied for their affinity for the compounds of interest. Although this method is developed for qualitative analysis, the extraction time and temperature profile are thoroughly investigated to provide the optimal conditions. The use of a salt solution is evaluated to increase the partitioning of MAAQ into the headspace. Using this method, qualitative extraction is achieved for the analysis of CN, CS, and MAAQ from its matrices. CN and CS are extracted in less than 5 min, though MAAQ needed more than 15 min to achieve a reasonable response. If more sensitivity is required, the use of a salt solution increases the response of MAAQ by 90-fold.

Journal Article↗
PubMed2004

Determination of di(2-ethylhexyl)phthalate and mono(2-ethylhexyl)phthalate in human serum using liquid chromatography-tandem mass spectrometry.

Concentrations of mono(2-ethylhexyl)phthalate (MEHP), and di(2-ethylhexyl)phthalate (DEHP), in serum of healthy volunteers were determined by high performance liquid chromatography (HPLC) with tandem mass spectrometry (LC/MS/MS). The serum was extracted with acetone, followed by hexane extraction under acidic conditions, and then applied to the LC/MS/MS. Recoveries of 20 ng/ml of MEHP and DEHP were 101+/-5.7 (n=6) and 102+/-6.5% (n=6), respectively. The limits of quantification (LOQ) of MEHP and DEHP in the method were 5.0 and 14.0 ng/ml, respectively. The concentration of MEHP in the serum was at or less than the LOQ. The concentration of DEHP in the serum was less than the LOQ. Contaminations of MEHP and DEHP from experimental reagents, apparatus and air during the procedure were less than the LOQ and were estimated to be <1.0 and 2.2+/-0.6 ng/ml, respectively. After subtraction of the contamination, the net concentrations of MEHP and DEHP in the serum were estimated at or <5 and <2 ng/ml, respectively. To decrease contamination by DEHP, the cleanup steps and the apparatus and solvent usage were minimized in the sample preparation procedures. The high selectivity of LC/MS/MS is the key for obtaining reliable experimental data from in the matrix-rich analytical samples and for maintaining a low level contamination of MEHP and DEHP in this experimental system. This method would be a useful tool for the detection of MEHP and DEHP in serum.

Chromatography, High Pressure Liquid↗
PubMed2006

Determination of antidepressants in surface and waste water samples by capillary electrophoresis with electrospray ionization mass spectrometric detection after preconcentration using off-line solid-phase extraction.

A method for the quantitative determination of seven major antidepressants in surface waters and sewage treatment plant effluents by CE using ESI-MS is presented. Calibration curves for the selected analytes were prepared in Milli-Q purified water and Danube river water extract covering a concentration range of at least one order of magnitude. LODs achieved were between 6 and 13 microg/L for Trazodone and 39 and 53 microg/L for Sertraline in the Milli-Q purified water and Danube river water matrix, respectively. For sample preparation eight different SPE materials were investigated. Best results were obtained for a resin based on hydrophilic divinylbenzene (recoveries from Milli-Q purified water 93-96%; from Danube river water 85-99%). Finally, a series of eight sewage treatment plant effluents were investigated with respect to their content in the selected antidepressants. Six of these samples were tested positive for antidepressants, in particular Venlafaxine, Citalopram and Trazodone in concentrations between 36 and 322 ng/L.

Antidepressive Agents↗
PubMed2003

High-performance liquid chromatographic method for the determination of quinine and 3-hydroxyquinine in blood samples dried on filter paper.

A simple high-performance liquid chromatographic method for the simultaneous analysis of quinine and 3-hydroxyquinine in blood samples dried on filter paper is described. Sample preparation involves liquid-liquid extraction with toluene-butanol 75:25 (v/v) followed by evaporation. A reversed-phase liquid chromatography system with fluorescence detection was used. The limit of determination was 10 nM for both quinine and 3-hydroxyquinine and the recovery varied between 78 and 109%. The within- and between-assay coefficients of variation varied between 2-5% and 4-10%, respectively. No loss of either analyte occurred after storage for 2 months at room temperature or at 37 degrees C. This method for sampling has advantages that make it of great value for clinical and pharmacokinetic studies especially in remote regions where storage and transportation is problematic.

Chromatography, High Pressure Liquid↗
PubMed2006

Liquid chromatographic/mass spectrometry assay of triptolide in dog plasma and its application to pharmacokinetic study.

A rapid and sensitive method for the determination of triptolide in dog plasma was developed and validated, using high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI/MS). Sample preparation consisted of liquid-liquid extraction with ethyl acetate from dog plasma. The analytes and internal standard prednisolone were well separated on a Zorbax Extend-C18 analytical column. Detection was performed on a triple quadrupole mass spectrometer using selected-ion monitoring (SIM) mode on the deprotonated ions [M-H]- at m/z 359. Calibration curves were linear over the concentration range of 0.5-200 ng/mL of triptolide with the intra- and inter-day precision (the relative standard deviation values) were being less than 7%. Triptolide was stable under different conditions. The intra-day and inter-day accuracy were 99.3-105.2% and 101.3-107.0%, respectively. The lower limit of quantification was 0.5 ng/mL. The method was successfully applied to a pharmacokinetic study after an intragastric administration (i.g.) of triptolide to dogs with a dose of 0.05 mg/kg. The results confirm that the assay is suitable for the pharmacokinetic study of triptolide.

Animals↗
PubMedDate not supplied

Automated liquid chromatographic determination of aflatoxin M1 in milk using on-line dialysis for sample preparation.

A procedure has been developed for the automated isolation of aflatoxin M1 from decreamed milk. The method uses on-line stopped flow dialysis and subsequent trace enrichment on a reverse-phase column. After a back-flush to the analytical liquid chromatography column, aflatoxin M1 is determined with fluorescence detection. Fully automated analysis is possible with reproducible dialysis recoveries above 50% (CV = 7.5%, n = 25 at the 50 ng/kg level) and determination levels of 20 ng/kg within 20 min.

Aflatoxin M1↗
PubMedDate not supplied

Determination of tylosin in feeds by liquid chromatography with solid-phase extraction.

A method was developed for the determination of tylosin in feeds. The method involves extraction of tylosin with methanol, concentration under a stream of nitrogen, and cleanup using Phenomenex C18 solid-phase extraction cartridge. Analyte separation and quantitation were achieved by gradient reversed-phase liquid chromatography and UV absorbance at 285 nm with a reference wavelength of 320 nm with column temperature of 45 degrees C. Average spike recoveries for samples prepared at 4 spiking levels (22.7, 181, 907, and 1000 g/ton) were 111.0, 94.9, 96.2, and 98.6%, respectively. The overall method precision at each of the 4 spiking levels was < or = 7.85% relative standard deviation. The limits of detection and quantitation (g/ton) were 2.16 and 7.20 g/ton, respectively.

Animal Feed↗
PubMed2004

Crystallization data mining in structural genomics: using positive and negative results to optimize protein crystallization screens.

Recent efforts to collect and mine crystallization data from structural genomics (SG) consortia have led to the identification of minimal screens and novel screening strategies that can be used to streamline the crystallization process. Two groups, the Joint Center for Structural Genomics and the University of Toronto, carried out large-scale crystallization trials on different sets of bacterial targets (539, JCSG and 755, Toronto), using different sample processing and crystallization methods, and then analyzed their results to identify the smallest subset of conditions that would have crystallized the maximum number of protein targets. The JCSG Core Screen contains 67 conditions (from 480) while the Toronto Minimal Screen contains 6 (from 48). While the exact conditions included in the two screens do not overlap, the major precipitants of the conditions are similar and thus both screens can be used to determine if a protein has a natural propensity to crystallize. In addition, studies from other groups including the University of Queensland, the Mycobacterium tuberculosis SG group, the Southeast Collaboratory for SG, and the York Structural Biology Laboratory indicate that alternative crystallization strategies may be more successful at identifying initial crystallization conditions than typical sparse matrix screens. These minimal screens and alternative screening strategies are already being used to optimize the crystallization processes within large SG efforts. The differences between these results, however, demonstrate that additional studies which examine the influence of protein biophysical properties and sample preparation methods on crystal formation must also be carried out before more robust screens can be identified.

Chemistry Techniques, Analytical↗
PubMed1994

On-line sample preparation for the determination of riboflavin and flavin mononucleotides in foodstuffs.

An on-line sample preparation method is described for the determination of riboflavin and flavin mononucleotide (FMN) in milk and cereal samples by high-performance liquid chromatography (HPLC) with fluorescence detection. The on-line system consists of microwave extraction followed by dialysis and trace enrichment with a C18 mini-column. Sample preparation was minimal, with milk samples being directly introduced into the system and cereal only needing to be ground prior to analysis. Results were obtained for a range of samples and these were found to be in agreement with the Association of Official Analytical Chemists (AOAC) method and a previously reported HPLC method. Recoveries were between 94 and 106% for a range of different samples and the relative standard deviation for ten samples was in the range 1.2-2.0%. During the microwave extraction all the flavin adenine dinucleotide (FAD) was converted into FMN and 15% of FMN was converted into riboflavin. The full analysis time on the ground samples was about 20 min.

Animals↗
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↗