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Internal Standards (internal + standards)
Selected AbstractsRadical Reduction of Epoxides Using a Titanocene(III)/Water System: Synthesis of ,-Deuterated Alcohols and Their Use as Internal Standards in Food AnalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2010Tania Jiménez Abstract We describe a comprehensive study into the Cp2TiCl-mediated reductive epoxide ring opening using either water as a hydrogen source or deuterium oxide as a deuterium source. The remarkable chemical profile of this reaction allows access to alcohols with anti-Markovnikov regiochemistry from different epoxides. The use of D2O as a deuterium source leads to an efficient synthesis of ,-deuterated alcohols, including a deuterated sample of tyrosol, a bioactive compound contained in the leaves of the olive, which was successfully applied as an internal standard in food analysis. [source] Improvements for comparative analysis of changes in diversity of microbial communities using internal standards in PCR-DGGEFEMS MICROBIOLOGY ECOLOGY, Issue 3 2005Dorthe Groth Petersen Abstract The use of internal standards both during DNA extraction and PCR-DGGE procedure gives the opportunity to analyse the relative abundance of individual species back to the original sample, thereby facilitating relative comparative analysis of diversity. Internal standards were used throughout the DNA extraction and PCR-DGGE to compensate for experimental variability. Such variability causes decreased reproducibility among replicate samples as well as compromise comparisons between samples, since experimental errors cannot be differentiated from actual changes in the community abundance and structure. The use of internal standards during DNA extraction and PCR-DGGE is suitable for ecological and ecotoxicological experiments with microbial communities, where relative changes in the community abundance and structure are studied. We have developed a protocol Internal Standards in Molecular Analysis of Diversity (ISMAD) that is simple to use, inexpensive, rapid to perform and it does not require additional samples to be processed. The internal standard for DNA extraction (ExtrIS) is a fluorescent 510-basepair PCR product which is added to the samples prior to DNA extraction, recovered together with the extracted DNA from the samples and analysed with fluorescence spectrophotometry. The use of ExtrIS during isolation of sample DNA significantly reduced variation among replicate samples. The PCR internal standard (PCRIS) originates from the Drosophila melanogaster genome and is a 140-basepair long PCR product, which is amplified by non-competitive primers in the same PCR reaction tubes as the target DNA and analysed together with the target PCR product on the same DGGE gel. The use of PCRIS during PCR significantly reduced variation among replicate samples both when assessing total PCR product and when comparing bands representing species on a DGGE gel. The entire ISMAD protocol was shown to accurately describe changes in relative abundance in an environmental sample using PCR-DGGE. It should, however, be mentioned that despite the use of ISMAD some inherent biases still exist in DNA extraction and PCR-DGGE and these should be taken into consideration when interpreting the diversity in a sample based on a DGGE gel. [source] Synthesis of Deuterium-Labeled Perfume Ingredients as Internal Standards for Their GC/MS QuantificationHELVETICA CHIMICA ACTA, Issue 9 2009Christian Chapuis Abstract The synthesis of various D-labeled perfume ingredients (orris-like, sandalwood-like, musky, and amber-like) is presented. These substances, possessing practically identical H2O/solid and solid/gas partition coefficients as their unlabeled analogues, are used as internal standards for the validation of a new analytical GC/MS method for the determination of low residual concentrations in H2O after biodegradability tests. [source] ChemInform Abstract: Synthesis of Dioxin-Like Monofluorinated PCBs: For the Use as Internal Standards for PCB Analysis.CHEMINFORM, Issue 38 2008Richard Sott Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Improvements for comparative analysis of changes in diversity of microbial communities using internal standards in PCR-DGGEFEMS MICROBIOLOGY ECOLOGY, Issue 3 2005Dorthe Groth Petersen Abstract The use of internal standards both during DNA extraction and PCR-DGGE procedure gives the opportunity to analyse the relative abundance of individual species back to the original sample, thereby facilitating relative comparative analysis of diversity. Internal standards were used throughout the DNA extraction and PCR-DGGE to compensate for experimental variability. Such variability causes decreased reproducibility among replicate samples as well as compromise comparisons between samples, since experimental errors cannot be differentiated from actual changes in the community abundance and structure. The use of internal standards during DNA extraction and PCR-DGGE is suitable for ecological and ecotoxicological experiments with microbial communities, where relative changes in the community abundance and structure are studied. We have developed a protocol Internal Standards in Molecular Analysis of Diversity (ISMAD) that is simple to use, inexpensive, rapid to perform and it does not require additional samples to be processed. The internal standard for DNA extraction (ExtrIS) is a fluorescent 510-basepair PCR product which is added to the samples prior to DNA extraction, recovered together with the extracted DNA from the samples and analysed with fluorescence spectrophotometry. The use of ExtrIS during isolation of sample DNA significantly reduced variation among replicate samples. The PCR internal standard (PCRIS) originates from the Drosophila melanogaster genome and is a 140-basepair long PCR product, which is amplified by non-competitive primers in the same PCR reaction tubes as the target DNA and analysed together with the target PCR product on the same DGGE gel. The use of PCRIS during PCR significantly reduced variation among replicate samples both when assessing total PCR product and when comparing bands representing species on a DGGE gel. The entire ISMAD protocol was shown to accurately describe changes in relative abundance in an environmental sample using PCR-DGGE. It should, however, be mentioned that despite the use of ISMAD some inherent biases still exist in DNA extraction and PCR-DGGE and these should be taken into consideration when interpreting the diversity in a sample based on a DGGE gel. [source] Some fundamental and technical aspects of the quantitative analysis of pharmaceutical drugs by matrix-assisted laser desorption/ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2005Lekha Sleno The purpose of the present paper was to study some of the underlying physical and technical aspects of high-throughput quantitative matrix-assisted laser desorption/ionization (MALDI) of small drug molecules. A prototype MALDI-triple quadrupole instrument equipped with a high repetition rate laser was employed. Initially, the detection limits and dynamic ranges for the quantitation of four drugs (quinidine, danofloxacin, ramipril and nadolol) were determined. Internal standards were carefully chosen for each of these analytes in terms of structure similarity and fragmentation pathways. Three organic matrices were tested for these assays, resulting in different crystallization behaviors and measurement reproducibilities. , -Cyano-4-hydroxycinnamic acid yielded the best results and was subsequently employed for the quantitative determination of all four analytes. Further experiments considered the role of laser energy and pulse rate on the ablated areas as well as ion signals. Light microscope and scanning electron microscope images allowed the examination of the ablated area of the MALDI spots. The images showed convincing evidence that the ablated area was virtually void of crystals after analysis, with no preferential removal of material in the center of the laser's path. Average values for the amount of material ablated were determined to be 3.9,±,0.5% of the total spot size, and as low as 19.5 attomoles of analyte were detectable for our most sensitive analyte, ramipril. It was calculated that, under these assay conditions, it was possible to accurately quantify less than 1 femtomole of all analytes with the use of appropriately pure internal standards. These studies showed very promising results for the quantitative nature of MALDI for small molecules with molecular weights less than 500,Da. Copyright © 2005 John Wiley & Sons, Ltd. [source] Electromigration diffusivity spectrometry: A way for simultaneous determination of diffusion coefficients from mixed samplesELECTROPHORESIS, Issue 17 2010Suhua Yang Abstract A novel method was proposed for simultaneous measurement of diffusion coefficients, (D), from mixed samples by electrophoresis and termed electromigration-based diffusivity spectrometry. After theoretical treatment, D- equation for practical use has been deduced. With a modified CE system built in laboratory, electromigration-based diffusivity spectrometry has been realized and validated to suit for fast and accurate determination of diffusivities of mixed aromatic amino acids, phenols and aromatic organic acid, giving diffusivity spectra by peak area versus D, much similar to mass spectra. The precision of the measurement was found to critically depend on pH value of running buffer, which should be so selected that the analytes and internal standards could be charged at above 0.5e. The standards have to be selected at an electric flux far from each other and from analytes. In these cases, sample and running buffer concentrations, voltage and system temperature were found to have only negligible impact on the determination. In our test, the obtained measuring precision was generally kept within 1% for five runs, and the measured values of D agreed well with those from literature, with a deviation of less than 2.2% after the right use of calibration standards. [source] Universal multiplex PCR and CE for quantification of SMN1/SMN2 genes in spinal muscular atrophyELECTROPHORESIS, Issue 7 2009Chun-Chi Wang Abstract We established a universal multiplex PCR and CE to calculate the copy number of survival motor neuron (SMN1 and SMN2) genes for clinical screening of spinal muscular atrophy (SMA). In this study, one universal fluorescent primer was designed and applied for multiplex PCR of SMN1, SMN2 and two internal standards (CYBB and KRIT1). These amplicons were separated by conformation sensitive CE. Mixture of hydroxyethyl cellulose and hydroxypropyl cellulose were used in this CE system. Our method provided the potential to separate two 390-bp PCR products that differ in a single nucleotide. Differentiation and quantification of SMN1 and SMN2 are essential for clinical screening of SMA patients and carriers. The DNA samples included 22 SMA patients, 45 parents of SMA patients (obligatory carriers) and 217 controls. For evaluating accuracy, those 284 samples were blind-analyzed by this method and denaturing high pressure liquid chromatography (DHPLC). Eight of the total samples showed different results. Among them, two samples were diagnosed as having only SMN2 gene by DHPLC, however, they contained both SMN1 and SMN2 by our method. They were further confirmed by DNA sequencing. Our method showed good agreement with the DNA sequencing. The multiplex ligation-dependent probe amplification (MLPA) was used for confirming the other five samples, and showed the same results with our CE method. For only one sample, our CE showed different results with MLPA and DNA sequencing. One out of 284 samples (0.35%) belonged to mismatching. Our method provided a better accurate method and convenient method for clinical genotyping of SMA disease. [source] Use of poly(vinyl alcohol)-coated capillaries for separation of amino-terminated polyamidoamine dendrimersELECTROPHORESIS, Issue 3 2007Britton Carter Abstract Characterization of amino-terminated polyamidoamine dendrimers by CE suffers from a lack of resolution for higher generations and poor between-day reproducibility of retention times. Under optimal conditions of temperature, voltage, and sample amount, 0,5,generations of dendrimers could be resolved with a bare fused-silica capillary. However, reproducibility was poor due to potential interactions of the polycationic dendrimers with the uncoated quartz capillary wall. Use of a poly(vinyl alcohol)-coated capillary significantly decreased the migration times of the nanomolecules without compromising resolution. Dendrimer mixtures containing generations,0,5 are separated as discrete, nonoverlapping peaks in about 15,min. In addition, the between-day precision of retention times was dramatically improved without the need for internal standards or data normalization. Dendrimers of various generations and cores run on different days showed an RSD of retention times of less than 4%. The poly(vinyl alcohol) coating was very stable as shown by the excellent precision of migration times obtained on a capillary used for a month with more than 100,injections. Similar to PAGE, separation of polyamidoamine dendrimers on a bare fused-silica and poly(vinyl alcohol)-coated capillary showed an exponential relationship between migration times and calculated charge density of the nanomolecules. [source] Capillary electrophoresis of polycationic poly(amidoamine) dendrimersELECTROPHORESIS, Issue 15 2005Xiangyang Shi Abstract Generation,2 to generation,5 poly(amidoamine) (PAMAM) dendrimers having different terminal functionalities were analyzed by capillary electrophoresis (CE). Polyacrylamide gel electrophoresis was also used to assess the composition of the individual generations for comparison with the CE results. Separation of PAMAMs can be accomplished by either using uncoated silica or silanized silica capillaries, although reproducibility is poor using the uncoated silica capillary. To improve run-to-run reproducibility, silanized capillary was used and various internal standards were also tested. Relative and normalized migration times of primary amine terminated PAMAM dendrimers were then determined using 2,3-diaminopyridine (2,3-DAP) as an internal standard. Using silanized capillaries and internal standards, the relative and normalized migration times are fully reproducible and comparable between runs. Apparent dimensionless electrophoretic mobilities were determined and the results were compared to theoretical calculations. It is concluded that for PAMAMs a complex separation mechanism has to be considered in CE, where the movement of the ions is due to the electric field, but the separation is rather the consequence of the adsorption/desorption equilibria on the capillary wall ("electrokinetic capillary chromatography"). The described method may be used for quality control and may serve as an effective technique to analyze polycationic PAMAM dendrimers and their derivatives with different surface modifications. [source] Capillary electrophoresis-laser induced fluorescence analysis of endogenous damage in mitochondrial and genomic DNAELECTROPHORESIS, Issue 13 2005Michaela Wirtz Abstract Reactive oxygen molecules are formed in vivo as by-products of normal aerobic metabolism. All organisms dependent on oxygen are inevitably exposed to these species so that DNA damage can occur in both genomic and mitochondrial DNA (mtDNA). In order to determine endogenous DNA damage we have developed an analytical method that involves the isolation and hydrolysis of genomic DNA or mtDNA, the labeling of modified and unmodified nucleotides and micellar electrokinetic chromatography with laser-induced fluorescence detection. With this method we have found etheno-adenine, thymine glycol, uracil, hypoxanthine, and 5-methylcytosine. These were identified by the addition of internal standards to the genomic or mtDNA. There are a large number of other signals in the electropherograms of mtDNA that we have never found in genomic DNA analysis because they are at lower concentration in the genome. In the DNA of untreated patients with chronic lymphocytic leukemia (CLL), uracil and high levels of etheno-adenine were found, which can be explained by antioxidant enzyme alterations and oxidative stress in the CLL lymphocytes. [source] Substances with estrogenic activity in effluents of sewage treatment plants in southwestern Germany.ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2001Abstract A gas chromatography/mass spectrometry method for the simultaneous quantitative determination of natural and synthetic estrogens (17,-estradiol, estrone, 17,-ethinylestradiol, and mestranol), phytoestrogens (genistein and ,-sitosterol), and xenoestrogens (benzyl butyl phthalate, dibutyl phthalate, bisphenol A, 4-nonylphenol [NP], 4-nonylphenoxyacetic acid [NP1EC], 4-nonyl-phenol diethoxylate [NP2EO], and ,-endosulfan) in effluents of sewage treatment plants (STPs) was developed. Identification and quantification were carried out with the standard addition method using analyte-specific and, in some cases, deuterium-labeled internal standards. The effluents of 18 STPs were investigated. Apart from ,-endosulfan and mestranol, all selected substances were detected in the majority of samples. The median concentrations of steroidal estrogens were between 0.4 ng/L (17,-ethiny-lestradiol) and 1.6 ng/L (17,-estradiol). The metabolites of the nonylphenol polyethoxylates, NP, NP1EC, and NP2EO were found in concentrations ranging from the upper-ng/L-range (NP) to the lower-,g/L range (NP1EC). For all substances except mestranol and ,-endosulfan, median values were calculated and compared to the results of other investigations in Europe and the United States. Possible dependencies of measured concentrations on the geographical location, the capacity, the influent composition, and the technical fitting of the STPs are discussed. [source] Improvements for comparative analysis of changes in diversity of microbial communities using internal standards in PCR-DGGEFEMS MICROBIOLOGY ECOLOGY, Issue 3 2005Dorthe Groth Petersen Abstract The use of internal standards both during DNA extraction and PCR-DGGE procedure gives the opportunity to analyse the relative abundance of individual species back to the original sample, thereby facilitating relative comparative analysis of diversity. Internal standards were used throughout the DNA extraction and PCR-DGGE to compensate for experimental variability. Such variability causes decreased reproducibility among replicate samples as well as compromise comparisons between samples, since experimental errors cannot be differentiated from actual changes in the community abundance and structure. The use of internal standards during DNA extraction and PCR-DGGE is suitable for ecological and ecotoxicological experiments with microbial communities, where relative changes in the community abundance and structure are studied. We have developed a protocol Internal Standards in Molecular Analysis of Diversity (ISMAD) that is simple to use, inexpensive, rapid to perform and it does not require additional samples to be processed. The internal standard for DNA extraction (ExtrIS) is a fluorescent 510-basepair PCR product which is added to the samples prior to DNA extraction, recovered together with the extracted DNA from the samples and analysed with fluorescence spectrophotometry. The use of ExtrIS during isolation of sample DNA significantly reduced variation among replicate samples. The PCR internal standard (PCRIS) originates from the Drosophila melanogaster genome and is a 140-basepair long PCR product, which is amplified by non-competitive primers in the same PCR reaction tubes as the target DNA and analysed together with the target PCR product on the same DGGE gel. The use of PCRIS during PCR significantly reduced variation among replicate samples both when assessing total PCR product and when comparing bands representing species on a DGGE gel. The entire ISMAD protocol was shown to accurately describe changes in relative abundance in an environmental sample using PCR-DGGE. It should, however, be mentioned that despite the use of ISMAD some inherent biases still exist in DNA extraction and PCR-DGGE and these should be taken into consideration when interpreting the diversity in a sample based on a DGGE gel. [source] Linearization of second-order calibration curves in stable isotope dilution,mass spectrometryFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2001Laurent B. Fay Abstract The quantification of compounds using isotope dilution mass spectrometry requires the establishment of calibration curves prior to determination of any unknown sample. When calibration over a wide concentration range is required and/or when an overlap exists between internal standard and analyte ions (if mono- or di-isotopically-labelled internal standards are used), second-order calibration curves are obtained. In this paper we have compared several calculation methods to linearize such calibration curves. We found that the method published by Bush and Trager6 gives a satisfactory linear relationship between the corrected amount ratio y = Ql(Qu+tQl) (the value Qu being the amount of unlabelled analyte, Ql the amount of labelled internal standard and t, the fixed fraction of the internal standard, which is identical to the unlabelled analyte) and the ratio of unlabelled to labelled ion intensities. All the other calculation methods that have been published so far have failed to linearize the second-order calibration curve build-up over a wide concentration range. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of Deuterium-Labeled Perfume Ingredients as Internal Standards for Their GC/MS QuantificationHELVETICA CHIMICA ACTA, Issue 9 2009Christian Chapuis Abstract The synthesis of various D-labeled perfume ingredients (orris-like, sandalwood-like, musky, and amber-like) is presented. These substances, possessing practically identical H2O/solid and solid/gas partition coefficients as their unlabeled analogues, are used as internal standards for the validation of a new analytical GC/MS method for the determination of low residual concentrations in H2O after biodegradability tests. [source] Towards a quantitative SERS approach , online monitoring of analytes in a microfluidic system with isotope-edited internal standardsJOURNAL OF BIOPHOTONICS, Issue 4 2009Anne März Abstract In this contribution a new approach for quantitative measurements using surface-enhanced Raman spectroscopy (SERS) is presented. Combining the application of isotope-edited internal standard with the advantages of the liquid,liquid segmented-flow-based approach for flow-through SERS detection seems to be a promising means for quantitative SERS analysis. For the investigations discussed here a newly designed flow cell, tested for ideal mixing efficiency on the basis of grayscale-value measurements, is implemented. Measurements with the heteroaromatics nicotine and pyridine using their respective deuterated isotopomers as internal standards show that the integration of an isotopically labeled internal standard in the used liquid,liquid two-phase segmented flow leads to reproducible and comparable SERS spectra independent from the used colloid. With the implementation of an internal standard into the microfluidic device the influence of the properties of the colloid on the SERS activity can be compensated. Thus, the problem of a poor batch-to-batch reproducibility of the needed nanoparticle solutions is solved. To the best of our knowledge these are the first measurements combining the above mentioned concepts in order to correct for differences in the enhancement behaviour of the respective colloid. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] COMPARISON OF HEADSPACE SOLID PHASE MICROEXTRACTION AND XAD-2 METHODS TO EXTRACT VOLATILE COMPOUNDS PRODUCED BY SACCHAROMYCES DURING WINE FERMENTATIONSJOURNAL OF FOOD QUALITY, Issue 1 2006JEFFRI C. BOHLSCHEID ABSTRACT A modified headspace solid phase microextraction (HS-SPME) method was compared with Amberlite® XAD-2 resin for the extraction of volatile compounds. In the HS-SPME method, volatiles were extracted using an 85 ,m polyacrylate fiber from wines that contained a standardized amount of ethanol (10% v/v), NaCl (0.325 g/mL) and internal standards (dodecanol and nonanoic acid). Both extraction procedures yielded high relative recoveries (>92%) and reproducibilities (coefficient of variations , 11%) for the different higher alcohols, esters and medium-chain fatty acids. Overall, limits of detection for the HS-SPME and XAD-2 methods were below sensory threshold concentrations. HS-SPME and XAD-2 performed similarly in the analysis of a Riesling wine; however, the HS-SPME method did not require organic solvents and was generally quicker to perform. In applying the HS-SPME method, differences in concentrations of volatile compounds produced in Riesling and Chenin blanc wines by 11 different yeast strains were noted. [source] Synthesis of deuterated herbicidal ZJ0273, ZJ0702, ZJ0777, and SIOC0163JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2010Zheng-Min Yang Abstract ZJ0273 (propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate), ZJ0702 (isopropyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate), ZJ0777 (2-bromo- N -(2-(4,6-dimethoxypyrimidin-2-yloxy)benzyl)aniline), and SIOC0163 (5-bromo- N -(2-(4,6-dimethoxypyrimidin-2-yloxy)benzyl)pyridin-2-amine) are active ingredients in oilseed rape herbicides. The middle aromatic ring-deuterated form of ZJ0273 was synthesized from (2H6)phenol and have been successfully used as tracer in its metabolism and degradation study. The methoxyl-deuterated forms of four ingredients were synthesized from (2H4)methanol, respectively, and they could be used as internal standards in quantitation of herbicide residue in rapeseed and its downstream foodstuff by using HPLC-MS/MS. Copyright © 2010 John Wiley & Sons, Ltd. [source] Microwave-accelerated synthesis of psychoactive deuterated N,N -dialkylated-[,,,,,,, -d4]-tryptaminesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2008Simon D. Brandt Abstract A large number of N,N -dialkylated tryptamines are known to induce psychoactive effects in humans. This has resulted in their increased attention within clinical and forensic communities. Deuterated tryptamines are ideal for use as internal standards during MS bioanalysis or of use in biochemical NMR studies. The present study reports on a microwave-enhanced synthesis of 22 N,N -dialkylated-[,,,,,,, -d4]-tryptamines via the reduction with lithium aluminium deuteride of glyoxalylamide precursors obtained by the procedure of Speeter and Anthony. Syntheses were carried out using a single-mode system under elevated pressure conditions where anhydrous tetrahydrofuran was used as the solvent at 150°C. Good yields were obtained within 5,min. Copyright © 2008 John Wiley & Sons, Ltd. [source] An efficient synthesis of [13C6]-3,5-dichloroanilineJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 7 2008Bachir Latli Abstract 3,5-Dichloroaniline is commonly found in many compounds with pharmacological and other biological activities. [13C6]-Aniline or its hydrochloride salt was converted in three steps to [13C6]-3,5-dichloroaniline, which can be incorporated in compounds of interest and used as internal standards in drug metabolism and pharmacokinetics (DMPK) studies. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis of the lipid peroxidation product 4-hydroxy-2(E)-nonenal with 13C stable isotope incorporationJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2008I. Jouanin Abstract The aim of this work was to synthesize 13C internal standards for the quantification of 4-hydroxy-2(E)-nonenal (HNE), a lipid peroxidation product, and of the etheno-adducts possibly formed by HNE damage to DNA nucleobases. We designed an eight-step synthesis starting from ethyl 2-bromoacetate and giving access to 4-[(tetrahydro- 2H -pyran-2-yl)oxy]-2(E)-nonenal. This compound is a precursor of HNE. The scheme was then used to produce the 13C precursor [1,2- 13C2]-4-[(tetrahydro- 2H -pyran-2-yl)oxy]-2(E)-nonenal. [1,2- 13C2]-HNE was obtained by acid deprotection. All the intermediary and final compounds were fully characterized by IR, HRMS, 1H and 13C NMR. It is the first synthesis of HNE which enables the incorporation of two 13C labels at determined positions. Copyright © 2008 John Wiley & Sons, Ltd. [source] Use of simple stable labelled intermediates to produce complex isotopically labelled internal standards,JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 5-6 2007Paul Allen [source] The synthesis of multiply 13C-labelled plant and mammalian lignans as internal standards for LC-MS and GC-MS analysisJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2005Tara Fryatt Abstract The syntheses of multiply 13C-labelled derivatives of the two mammalian lignans, enterolactone and enterodiol, and two of their plant lignan precursors, secoisolariciresinol and matairesinol, are described. Three 13C atoms were incorporated into each lignan using potassium [13C]cyanide as the source for all of the 13C atoms. The compounds were prepared for use as internal standards in the LC-MS and GC-MS analysis of lignans. Copyright © 2005 John Wiley & Sons, Ltd. [source] The evolution of volatile compounds profile of "Toscano" dry-cured ham during ripening as revealed by SPME-GC-MS approach,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2010C. Pugliese Abstract The volatile compounds profile is an important feature for the characterization of dry-cured hams. Some minor typical Italian products, such as ,Toscano' ham, have been poorly studied in regards to their composition of volatile compounds. In this article, we studied the evolution of the aromatic profile of ,Toscano' dry-cured ham by solid-phase microextraction-gas chromatographic-mass spectrometry (SPME-GC-MS) with ripening. Ten right thighs were cured according to the ,Toscano' PDO protocol, sampled at 0, 1, 3, 6 and 12 months and submitted to volatile compounds analysis by SPME with a Divinylbenzene (DVB)/Carboxen/Polydimethylsiloxane (PDMS) 75-µ Stable Flex fibre. An Agilent 5975C mass selective detector (MSD) spectrometer with electron ionization (EI) source operating in scan mode within the m/z 29,350 range was used for data collection. Seven internal standards, either deuterium labeled or absent in the specimens and chosen to represent low or high boiling esters, alcohols, acids or phenols, were added to the homogenized samples and used to normalize the SPME fibre response to account for response changes upon wearing. Linear calibrations were obtained in this way for selected representative compounds. Over 60 compounds belonging to esters, aldehydes, organic acids, ketones and alcohols were identified by comparison with spectral libraries and Kovats indices. Aldehydes were the most represented chemical family, followed by organic acids, alcohols, ketones and esters. The aldehydes and ketones increased during the first 3 months, when the larger formation of volatiles occurred. For other families, the evolution over time was less evident. The principal component and discriminant analyses of the aromatic profile were effective in classifying the hams at 0, 6 or 12 months of ripening while for 1 and 3 months' samples a partial overlapping was shown. These results represent the first characterization of ,Toscano' ham and may constitute the basis to identify the best ripening time and define an analytical quality standard for this typical ham. Copyright © 2010 John Wiley & Sons, Ltd. [source] Detection and validated quantification of nine herbal phenalkylamines and methcathinone in human blood plasma by LC-MS/MS with electrospray ionizationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2007Jochen Beyer Abstract The herbal stimulants Ephedra species, Catha edulis (khat), and Lophophora williamsii (peyote) have been abused for a long time. In recent years, the herbal drug market has grown owing to publicity on the Internet. Some ingredients of these plants are also ingredients of cold remedies. The aim of the presented study is to develop a multianalyte procedure for detection and validated quantification of the phenalkylamines ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine, methylpseudoephedrine, cathinone, mescaline, synephrine (oxedrine), and methcathinone in plasma. After mixed-mode solid-phase extraction of 1 ml of plasma, the analytes were separated using a strong cation exchange separation column and gradient elution. They were detected using a Q-Trap LC-ESI-MS/MS system (MRM mode). Calibration curves were used for quantification using norephedrine- d3, ephedrine- d3, and mescaline- d9 as internal standards. The method was validated according to international guidelines. The assay was selective for the tested compounds. It was linear from 10 to 1000 ng/ml for all analytes. The recoveries were generally higher than 70%. Accuracy ranged from , 0.8 to 20.0%, repeatability from 2.5 to 12.3%, and intermediate precision from 4.6 to 20.0%. The lower limit of quantification was 10 ng/ml for all analytes. No instability was observed after repeated freezing and thawing or in processed samples. The applicability of the assay was tested by analysis of authentic plasma samples after ingestion of different cold medications containing ephedrine or pseudoephedrine, and after ingestion of an aqueous extract of Herba Ephedra. After ingestion of the cold medications, only the corresponding single alkaloids were detected in human plasma, whereas after ingestion of the herb extract, all six ephedrines contained in the plant were detected. The presented LC-MS/MS assay was found applicable for sensitive detection and accurate and precise quantification of all studied analytes in plasma. Copyright © 2006 John Wiley & Sons, Ltd. [source] A validated method for the determination of nicotine, cotinine, trans -3,-hydroxycotinine, and norcotinine in human plasma using solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization-mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2006Insook Kim Abstract A liquid chromatographic-mass spectrometric method for the simultaneous determination of nicotine, cotinine, trans -3,-hydroxycotinine, and norcotinine in human plasma was developed and validated. Analytes and deuterated internal standards were extracted from human plasma using solid-phase extraction and analyzed by liquid chromatography/atmospheric pressure chemical ionization-mass spectrometric detection with selected ion monitoring (SIM). Limits of detection and quantification were 1.0 and 2.5 ng/ml, respectively, for all analytes. Linearity ranged from 2.5 to 500 ng/ml of human plasma using a weighting factor of 1/x; correlation coefficients for the calibration curves were > 0.99. Intra- and inter-assay precision and accuracy were < 15.0%. Recoveries were 108.2,110.8% nicotine, 95.8,108.7% cotinine, 90.5,99.5% trans -3,-hydroxycotinine, and 99.5,109.5% norcotinine. The method was also partially validated in bovine serum, owing to the difficulty of obtaining nicotine-free human plasma for the preparation of calibrators and quality control (QC) samples. This method proved to be robust and accurate for the quantification of nicotine, cotinine, trans -3,-hydroxycotinine, and norcotinine in human plasma collected in clinical studies of acute nicotine effects on brain activity and on the development of neonates of maternal smokers. Copyright © 2006 John Wiley & Sons, Ltd. [source] LC,ESI-MS/MS analysis for the quantification of morphine, codeine, morphine-3-,- D -glucuronide, morphine-6-,- D -glucuronide, and codeine-6-,- D -glucuronide in human urineJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2005Constance M. Murphy Abstract A liquid chromatographic-electrospray ionization-tandem mass spectrometric method for the quantification of the opiates morphine, codeine, and their metabolites morphine-3-,- D -glucuronide (M-3-G), morphine-6-,- D -glucuronide (M-6-G) and codeine-6-,- D -glucuronide (C-6-G) in human urine has been developed and validated. Identification and quantification were based on the following transitions: 286 to 201 and 229 for morphine, 300 to 215 and 243 for codeine, 644 to 468 for M-3-G, 462 to 286 for M-6-G, and 476 to 300 for C-6-G. Calibration by linear regression analysis utilized deuterated internal standards and a weighting factor of 1/X. The method was accurate and precise across a linear dynamic range of 25.0 to 4000.0 ng/ml. Pretreatment of urine specimens using solid phase extraction was sufficient to limit matrix suppression to less than 40% for all five analytes. The method proved to be suitable for the quantification of morphine, codeine, and their metabolites in urine specimens collected from opioid-dependent participants enrolled in a methadone maintenance program. Copyright © 2005 John Wiley & Sons, Ltd. [source] Simultaneous determination of melamine and related compounds by hydrophilic interaction liquid chromatography,electrospray mass spectrometryJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2010Jingen Xia Abstract A hydrophilic interaction liquid chromatography coupled to ESI-MS (HILIC/ESI-MS) method for the simultaneous determination of melamine and related compounds, i.e. ammeline, ammelide and cyanuric acid in foods was developed and validated. The separation was accomplished on a Venusil HILIC column with a mobile phase of acetonitrile + 10,mM ammonium formate buffer solution at pH 3.5 (88:12, v/v) under isocratic elution mode. For the detection of the targets, the ESI probe worked in the positive and negative switching mode. For each compound, three ions were selected as qualitative ions to obtain high specificity, and the most abundant ion of each compound was selected for quantification to obtain high sensitivity. The target compounds were quantified using SIM with 15N3-melamine and 13C3-cyanuric acid being used as an internal standards in the positive and negative modes, respectively. Compared with RP separation mode, HILIC has merits such as high separation and anti-interference efficiency. The method validation including linearity, LOD, LOQ, precision and recovery proved that the method has merits such high sensitivity, specificity and simplicity versus the other methods reported in the literature. [source] Determination of eight fatty acid ethyl esters in meconium samples by headspace solid-phase microextraction and gas chromatography,mass spectrometryJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2010Marli Roehsig Abstract A number of fatty acid ethyl esters (FAEEs) have recently been detected in meconium samples. Several of these FAEEs have been evaluated as possible biomarkers for in utero ethanol exposure. In the present study, a method was optimized and validated for the simultaneous determination of eight FAEEs (ethyl laurate, ethyl myristate, ethyl palmitate, ethyl palmitoleate, ethyl stearate, ethyl oleate, ethyl linoleate and ethyl arachidonate) in meconium samples. FAEEs were extracted by headspace solid-phase microextraction. Analyte detection and quantification were carried out using GC-MS operated in chemical ionization mode. The corresponding D5-ethyl esters were synthesized and used as internal standards. The LOQ and LOD for each analyte were <150 and <100,ng/g, respectively. The method showed good linearity (r2>0.98) in the concentration range studied (LOQ , 2000,ng/g). The intra- and interday imprecision, given by the RSD of the method, was lower than 15% for all FAEEs studied. The validated method was applied to 63 authentic specimens. FAEEs could be detected in alcohol-exposed newborns (>600,ng/g cumulative concentration). Interestingly, FAEEs could also be detected in some non-exposed newborns, although the concentrations were much lower than those measured in exposed cases. [source] Determination of aminoglycoside and macrolide antibiotics in meat by pressurized liquid extraction and LC-ESI-MSJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4-5 2010Houda Berrada Abstract A simple method for the simultaneous determination of dihydrostreptomycin, spectinomycin, spiramycin, streptomycin, tilmicosin, and tylosin in meat has been developed using pressurized liquid extraction and LC-triple quadrupole MS (LC-ESI-MS/MS). The pressurized liquid extraction operational parameters were optimized and no protein precipitating and fat removing steps were required. A gradient HPLC separation was developed with ion-pair mobile phases consisting of aqueous 1,mM heptafluorobutyric acid water and methanol. Protonated molecules were used as precursor ions for CID. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of three fragment ion transitions to provide a high degree of sensitivity and specificity. Dirithromycin and sisomycin were selected as internal standards. A validation study was conducted for these antibiotics in poultry meat samples. All selected compounds could be detected (monitoring ions by multiple reaction monitoring) in meat samples at amounts below the regulatory level of concern. Using the internal standards, pressurized liquid extraction recovery rates were from 70 to 96% (RSD 12,25%). LC-ESI-MS/MS method detection limits of the selected antibiotics were 1,6,,g/kg. Good method reproducibility was found by intra- and inter-day precisions at maximum residue level, yielding the RSDs less than 15 and 16%, respectively. [source] | |||||||||||||||||||||||||||||||