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At least 73 records · Page 4Linked to original sources
PubMed1998

Determination of four anabolic steroid metabolites by gas chromatography/mass spectrometry with negative ion chemical ionization and tandem mass spectrometry.

A gas chromatography/mass spectrometry method is described which uses negative ion chemical ionization and tandem mass spectrometry for the determination of anabolic steroid metabolites. Four anabolic steroid metabolites to be derivatized by Pentafluoropropionic anhydride (PFPA) were determined using gas chromatography/mass spectrometry (GC/MS) with negative chemical ionization (NCI) and NCI/MS/MS. The repeatability and reproducibility of this procedure were in the range of 5.3-9.7% and 6.1-10.2%, respectively. This method of derivatization with PFPA for NCI and NCI/MS/MS was useful to determine four metabolites of nandrolone, dromostanolone, methenolone and boldenone. The derivatized metabolites of boldenone could be detected to 2 ppb and the other three steroids could be detected to 25 ppb in urine at a signal-to-noise ratio of S/N = 3.

Anabolic Agents↗
PubMed1999

Analysis of 9-fluorenylmethyloxycarbonyl derivatives of catecholamines by high performance liquid chromatography, liquid chromatography/mass spectrometry and tandem mass spectrometry.

9-Fluorenylmethyloxycarbonyl (FMOC) derivatives of catecholamines, including dopamine (DA; 3,4-dihydroxyphenethylamine), norepinephrine (NE; 2-amino-1-(3,4-dihydroxyphenyl)ethanol) and epinephrine (EPI; 1-phenyl-1-hydroxy-2-methylaminopropane) as well as 3, 4-dihydroxybenzylamine (DHBA) have been analyzed using high performance liquid chromatography coupled to fluorometric detection and atmospheric pressure chemical ionization mass spectrometry at low femtomole levels. Structures of the derivatives have also been characterized by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry and electrospray/tandem mass spectrometry. Protonated molecules of FMOC-DA and FMOC-DHBA as well as [M + H - H(2)O](+) ions of FMOC-NE and FMOC-EPI appear in their conventional mass spectra, and abundant fragments characteristic of catecholamines dominated the spectra. Structurally diagnostic ions using several hundred femtomoles of the FMOC derivatives of catecholamine were observed. Collision-induced dissociation (CID) of electrospray-generated protonated molecules of FMOC-DA and FMOC-DHBA as well as [M + H - H(2)O](+) ions of FMOC-NE and FMOC-EPI produced diagnostic product ion spectra. Liquid chromatography/atmospheric pressure chemical ionization mass spectrometric analysis of the FMOC derivatives of catecholamines and DHBA should prove useful in the separation and characterization of these compounds from biological materials.

Animals↗
PubMed1985

Combined thin layer chromatography/mass spectrometry: an application of 252Cf plasma desorption mass spectrometry for drug monitoring.

The pharmacokinetic analysis is performed in a three-step procedure: sample extraction, sample purification by thin layer chromatography (TLC) and quantitative sample detection by time-of-flight (TOF) mass spectrometry. 252Cf plasma desorption (PD) mass spectrometry utilizing the fission fragment-induced ionization and desorption of non-volatile compounds is suitable as a universal, non-destructive detector in TLC. Here TLC and mass spectrometry are operated in an off-line combination. As an example some pharmacokinetic data for etoposide (VP 16-213) together with calibration data are presented. The new experimental method is discussed in terms of sensitivity and detection limit.

Californium↗
PubMed1988

Characterization of doxylamine and pyrilamine metabolites via thermospray/mass spectrometry and tandem mass spectrometry.

Analysis of doxylamine N-oxide and pyrilamine N-oxide as synthetic standards and biologically derived metabolites by thermospray mass spectrometry (TSP/MS) provided [M + H]+ ions for each metabolite. TSP/tandem mass spectrometry (TSP/MS/MS) of the [M + H]+ ions provided fragment ions characteristic of these metabolites. In addition, TSP mass spectrometry and TSP/MS/MS analysis of ring-hydroxylated N-desmethyldoxylamine, N-desmethylpyrilamine and O-dealkylated pyrilamine is also reported. A fragmentation pathway for analysis by MS/MS of pyrilamine and its metabolites is also proposed. The results demonstrate the utility of TSP/MS for biologically derived metabolites of pyrilamine and doxylamine.

Aminopyridines↗
PubMed1989

Characterization of seven antihistamines, their N-oxides and related metabolites by fast atom bombardment mass spectrometry and fast atom bombardment tandem mass spectrometry.

We have examined the synthetic N-oxides of five ethylenediamine-type antihistamines using fast atom bombardment (FAB) mass spectrometry and FAB tandem mass spectrometry (MS/MS). Fragmentation of the protonated molecule in the normal and collisionally activated spectra appeared to be characteristic for this class of antihistamine N-oxide. Spectra were also acquired from an ethanolamine and a propylamine antihistamine N-oxide for comparison. These results were very similar to those obtained from biologically produced antihistamine N-oxides, as well as isomeric metabolites, which were readily distinguished from the N-oxides by characteristic fragmentation. In addition, a prominent ion 16 daltons lower in mass, which has been attributed to loss of elemental oxygen from the protonated N-oxide in chemical ionization mass spectral studies, was shown to be a matrix-dependent product of the solution-phase reduction of the antihistamine N-oxide to the parent antihistamine during FAB ionization. These results demonstrate that with a non-reducing matrix such as glycerol, FAB mass spectrometry and FAB MS/MS are excellent methods for the characterization of the non-conjugated antihistamine metabolites such as the N-oxides.

Ethanolamines↗
PubMed1989

Thermospray mass spectrometry and tandem mass spectrometry of polar, urinary metabolites and metabolic conjugates.

This paper describes the characterization of glucuronide and sulfuric acid conjugates and alkyl phosphates by thermospray tandem mass spectrometry (MS/MS). Primary thermospray mass spectra were generated using ammonium acetate buffer and filament-on ionization with both positive and negative ion detection. In positive ion mode molecular weight information was obtained for glucuronic, phosphoric and other weak acids. Under these conditions, however, spectra were not obtained for the sulfate adducts or phosphate salts. Negative ion thermospray mass spectrometry was more versatile, providing spectra of all metabolic structures examined. Positive and negative ion mass spectra provided complementary information for glucuronic acids. Collisionally activated dissociation (CAD) mass spectra of the glucuronide [M + NH4]+ or [M - H]- ions exhibited characteristic glucuronide 'fingerprints' as well as prominent aglycone ions. The aryl sulfates were hydrolyzed to the corresponding phenols under buffer/thermospray conditions and for these analytes CAD mass spectra were obtained from [phenate]- or [phenol + acetate]- parent ions. The M- of dimethyl thiophosphate underwent sequential loss of alkyl and alkoxy radicals and formaldehyde with collisional activation. MS/MS greatly enhances the power of the thermospray interface by providing fragmentation information useful both in the identification of unknowns and for improved mass spectrometry specificity.

Chromatography, Gas↗
PubMed1994

Studies of non-covalent interactions of actinomycin D with single-stranded oligodeoxynucleotides by ion spray mass spectrometry and tandem mass spectrometry.

Non-covalent binding of actinomycin D (AMD) to single-stranded DNA (ssDNA) was observed by ion spray mass spectrometry. Interactions between AMD and different sequences of non-self-complementary oligodeoxynucleotides were investigated as a function of pH. Non-covalent AMD/ssDNA complexes disappeared at low pH, and no ssDNA complexes were detected with rifampicin (RP). Moreover, the different binding affinities between AMD and ssDNA with and without 5'G-C3' or 5'C-G3' base sequences were also demonstrated using ion spray mass spectrometry. Additional support for the non-covalent nature of binding in AMD/ssDNA complexes was obtained from tandem mass spectrometry.

Base Sequence↗
PubMed2004

Separation of beta2-microglobulin conformers by high-field asymmetric waveform ion mobility spectrometry (FAIMS) coupled to electrospray ionisation mass spectrometry.

An investigation into the use of high-field asymmetric waveform ion mobility spectrometry (FAIMS) coupled to electrospray ionisation mass spectrometry (ESI-MS) for the differentiation of co-populated protein conformers has been conducted on the amyloidogenic protein beta(2)-microglobulin (beta(2)m). Accumulation of beta(2)m in vivo can result in the deposition of insoluble fibrils whose formation is thought to originate from partially folded protein conformers; hence, the folding properties of beta(2)m are of significant interest. We have analysed beta(2)m using ESI-FAIMS-MS under a range of pH conditions and have studied the effect of the ion mobility spectrometry parameters on the behaviour of the various protein conformers. The data show that different protein conformers can be detected and analysed by ESI-FAIMS-MS, the results being consistent with observations of pH denaturation obtained using complementary biophysical techniques. A variant of beta(2)m with different folding characteristics has been analysed for comparison, and the distinctions observed in the data sets for the two proteins are consistent with their folding behaviour. ESI-FAIMS-MS offers significant opportunities for the study of the conformational properties of proteins and thus may present valuable insights into the roles that different conformers play in diseases related to protein folding.

Amino Acid Sequence↗
PubMed1994

Electrospray mass spectrometry and tandem mass spectrometry of synthetic multicomponent peptide mixtures: determination of composition and purity.

Electrospray (ES) mass spectrometry and tandem mass spectrometry were used to evaluate the composition and purity of synthetic peptide mixtures ("peptide libraries") consisting of 48 peptides in equimolar amounts. For the structurally similar components of the mixtures little mass discrimination effects were found. The ion intensity distribution of the protonated molecular ions was found to be independent of the concentration. The peak heights in the ES mass spectra reflected the number of isobaric peptides in the mixture. By-products formed by incomplete removal of side chain protecting groups were detected fast and conveniently by tandem mass spectrometry. Daughter ion scans were used to identify common structural features of the peptides and the by-products. Parent ion and constant neutral loss scans allowed the detection of all peptides modified with the same protecting group.

Amino Acid Sequence↗
PubMedDate not supplied

Application of real-time mass spectrometric techniques to environmental organic geochemistry. I. Computerized high resolution mass spectrometry and gas chromatography-low resolution mass spectrometry.

LOGOS (Smith et al. 1971), an integrated mass spectrometer/computer system, has been employed in a series of experiments which illustrate the utility of the automated techniques of real-time mass spectrometry in the study of organic compounds in the environment. These techniques are shown to be particularly useful in resolving complex mixtures of organic compounds encountered in environmental studies. Complete high resolution mass spectrometry, particularly when used in conjunction with combined gas chromatography/mass spectrometry, and auxiliary techniques such as stable isotopic labeling are described to illustrate the type and scope of information that may be obtained. Illustrative samples include extracts of air- and waterborne particulates, extracts of water-soluble organic material, and a DDT metabolite from sewage sludge.

Air↗
PubMed2005

Investigation of NOx precursor compounds and other combustion by-products in the primary combustion zone of a waste-incineration plant using on-line, real-time mass spectrometry and Fourier-transform infrared spectrometry (FTIR).

On-line analysis of trace and bulk gas compounds in the burning chamber of a waste-incineration plant has been performed, with high temporal resolution, by use of a variety of distinctly different measurement techniques. Time-of-flight mass spectrometry was performed with simultaneous use of three ionization techniques-resonance-enhanced multiphoton ionization (REMPI), single-photon ionization (SPI), and electron-impact ionization (EI). Chemical-ionization mass spectrometry (CIMS), Fourier-transform infrared spectrometry (FTIR), and electrochemical methods were also used. Sampling was conducted by means of a newly developed air-cooled stainless steel lance, to cope with the high temperatures and elevated particle concentrations at the sampling location. Nitrogen species were mainly nitrogen monoxide, ammonia, and hydrogen cyanide (HCN), with a small amount (approximately 0.3%) of aromatic nitrogen compounds. NO, NH(3), and HCN are the main contributors to the NO(x)-formation process in the postulated fuel-NO reaction scheme dominant at this location. The NO recycling process thereby plays a major role. Changes in plant operating conditions have a noticeable impact only when the air supply is varied. For example, reduction of oxygen leads to an increase in the HCN fraction of the total nitrogen content and a decrease in the NO fraction, and vice versa.

Incineration↗
PubMed1989

Analysis of the major urinary thromboxane metabolites, 2,3-dinorthromboxane B2 and 11-dehydrothromboxane B2, by gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry.

2,3-Dinorthromboxane B2 and 11-dehydrothromboxane B2, the two major metabolites of thromboxane B2, are considered to be indices of thromboxane A2 activity in humans. The determination of these metabolites in urine was comparatively performed by gas chromatography-mass spectrometry and gas chromatography-mass spectrometry-mass spectrometry using the corresponding chemically synthesized tetradeuterated analogues as internal standards. The urine samples of five females and two males, all healthy, were prepurified by solid-phase extraction. The corresponding pentafluorobenzyl ester derivatives were repurified by high-performance liquid chromatography. The concentrations of 2,3-dinorthromboxane B2 and 11-dehydrothromboxane B2 ranged from 21 to 266 pg/ml and 47 to 942 pg/ml, respectively. The ratio of urinary 2,3-dinorthromboxane B2 to 11-dehydrothromboxane B2 varied from 1:3 to 1:5, except for one sample with nearly equal concentrations of 2,3-dinorthromboxane B2 and 11-dehydrothromboxane B2.

Chemical Phenomena↗
PubMed2002

High-performance liquid chromatography--mass spectrometry and electron-capture dissociation tandem mass spectrometry of osteocalcin. Determination of gamma-carboxyglutamic acid residues.

Two mass spectrometry methods, high-performance liquid chromatography combined on-line with electrospray ionization mass spectrometry (HPLC-ESI-MS) and electron-capture (EC) dissociation tandem mass spectrometry (MS-MS), were applied for structural analysis of bovine and human osteocalcins. Osteocalcin contains gamma-carboxyglutamic acid (Gla) residues, which bind metal ions, among its amino acids. Ethylenediaminetetraacetic acid (EDTA) was added to all samples in order to chelate bound metal ions. After elimination of interfering metal ions MS spectra became uncomplicated to interpret. EDTA is incompatible with ESI and it was removed from samples using either on-line HPLC or micropurification method. The number of Gla residues varies in osteocalcin. These subforms, which contain different amounts of Gla residues, were separated using the HPLC-ESI-MS method. In order to determine locations of Gla residues in human osteocalcin, which contained two Gla residues, dissociation MS-MS method was successfully applied.

1-Carboxyglutamic Acid↗
PubMed1997

Complete structure elucidation of a globular protein by particle beam liquid chromatography-Fourier transform infrared spectrometry and electrospray liquid chromatography-mass spectrometry. Sequence and conformation of beta-lactoglobulin.

The advantages to the use of both mass spectrometry (MS) and Fourier transform infrared spectrometry (FT-IR) in combination for the structural characterization of the tryptic digest of a model globular protein is demonstrated. HPLC has been interfaced to both spectroscopic techniques and has provided a high degree of structural detail for the target protein. beta-Lactoglobulins A and B were digested with trypsin and chromatographed with narrow-bore, reversed-phase HPLC. As determined by LC-FT-IR spectrometry, the conformation of each form of intact beta-lactoglobulin was randomized upon elution. The particle beam and the electrospray LC-MS interfaces enabled the acquisition of spectra for nanogram injection quantities. The primary structures were determined from the accurate molecular mass determinations of the digest fragments. Infrared spectra confirmed the presence of some amino acid functionalities.

Amino Acid Sequence↗
PubMed1993

Characterisation of TNF-alpha-related peptides by high-performance liquid chromatography-mass spectrometry and high-performance liquid chromatography-tandem mass spectrometry.

Ion-spray triple quadrupole mass spectrometry and high-performance liquid chromatography were used to investigate the products from the solid phase synthesis of (H)-Leu-Thr-Glu-Asn-(OH), a TNF-alpha active-site probe. The target sequence was assembled using tert.-butoxycarbonyl (Boc) chemistry in stepwise fashion from the C-terminal on an Boc-Asn-OCH2-Pam-copoly(styrene-divinylbenzene) resin [Pam = 4-(carboxamidomethyl)benzyl ester]. The crude product was deprotected and cleaved from the resin by HF-p-cresol treatment for 1 h at 0 degrees C. HPLC analysis at 214 nm indicated two late-eluting major products and an early-eluting product. Preparative HPLC demonstrated that the early-eluting product contained ca. 80% of the expected recovered sample mass. Each component was then directly analysed by mass spectrometry and tandem mass spectrometry. The early eluting peak was confirmed as the desired LTEN sequence. Synthesis of the same sequence using 9-fluorenyl methoxycarbonyl (Fmoc) chemistry gave an identical product and confirmed the above analysis. The most significant by-product was derived from arylation of the glutamyl group by the quencher p-cresol. The likely origins of the by-products are discussed.

Amino Acid Sequence↗
PubMed2001

Comparison between liquid chromatography-time of-flight mass spectrometry and selected reaction monitoring liquid chromatography-mass spectrometry for quantitative determination of idoxifene in human plasma.

This study compares HPLC electrospray time-of-flight mass spectrometry and selected reaction monitoring (SRM) LC-MS for high throughput quantitative determination of a small molecule drug in biological samples. A high throughput LC-MS method was developed for quantitatative determination of idoxifene in human plasma and the evaluation was accomplished with the cross-validation of the developed LC-MS method between the time-of-flight mass spectrometer, and a triple quadrupole mass spectrometer operated in the SRM mode. A simple one-step semi-automated 96-well liquid-liquid extraction procedure was used to prepare 96 samples in approximately 30 min and a rapid gradient was used to shorten the LC run time. Time-of-flight mass spectrometry provides acquisition of full-scan mass spectra and extracted ion current chromatograms, which may be extracted from the total ion current chromatogram for peak area determination. The limit of quantitation for idoxifene in human plasma obtained with the time-of-flight mass spectrometer was 5 ng/ml based on 100-microl aliquots of human plasma, and the linear dynamic range was from 5 ng/ml to 2000 ng/ml. The quantitative LC-MS results from the time-of-flight mass spectrometer demonstrated that precision did not exceed 7.1% and accuracy did not exceed 1.7% with reference to quality control samples at three concentration levels in replicates of six. In contrast, the limit of quantitation for idoxifene in human plasma using a tandem triple quadrupole mass spectrometer was 0.5 ng/ml with a linear dynamic range to 1000 ng/ml. The results from the triple quadrupole instrument show that the precision did not exceed 2.2% and accuracy did not exceed 2.9%. The overall results suggest time-of-flight mass spectrometry may be a viable technique for high throughput bioanalytical work for the quantitative determination of a representative small molecule drug in the low ng/ml range in human plasma.

Calibration↗
PubMed2002

Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques.

The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization.

Atmospheric Pressure↗
PubMed2002

Solid phase microextraction with matrix assisted laser desorption/ionization introduction to mass spectrometry and ion mobility spectrometry.

Solid phase microextraction (SPME) with matrix assisted laser desorption/ionization (MALDI) introduction was coupled to mass spectrometry and ion mobility spectrometry. Nicotine and myoglobin in matrix 2,5-dihydroxybenzonic acid (DHB), enkephalin and substance P in alpha-cyano-4-hydroxy cinnaminic acid were investigated as the target compounds. The tip of an optical fiber was silanized for extraction of the analytes of interest from solution. The optical fiber thus served as the sample extraction surface, the support for the sample plus matrix, and the optical pipe to transfer the laser energy from the laser to the sample. The MALDI worked under atmospheric pressure, and both an ion mobility spectrometer and a quadrupole/time-of-flight mass spectrometer were used for the detection of the SPME/MALDI signal. The spectra obtained demonstrate the feasibility of the SPME with MALDI introduction to mass spectrometry instrumentation.

Enkephalins↗