Stable Isotope Dilution Mass Spectrometry Research Articles

Determination of choline and acetylcholine in distinct rat brain regions by stable isotope dilution and field desorption mass spectrometry

The determination of choline and acetylcholine by field desorption mass spectrometry from rat brain tissue samples has been demonstrated. Essential points of the assay are the use of stable isotope labelled internal standards, a simple ion pair extraction procedure, direct analysis of the quaternary ammonium ions without derivatization, and accumulation of the electrically recorded field desorption ion signals with a multi-channel analyser. The analysis of sample amounts in the picogram range gave quantitative data of good precision (0.6--10% standard deviation).

Determination of lithium in microlitre amounts of human body fluids at therapeutic and normal levels by stable isotope dilution and field desorption mass spectrometry.

The use of field desorption mass spectrometry for the determination of lithium in body fluids at therapeutic levels--ppm region--as well as at the normal level--ppb region--has been developed. The use of a stable isotope enriched internal standard, together with the outstanding sensitivity of field desorption for alkali cations and the high specificity of mass spectrometry, allows a quantitative determination of lithium in microlitre amounts of body fluids, such as plasma, saliva and urine. The assay allows a determination of lithium even at ultratrace concentrations where routine spectroscopic procedures cannot be applied. Analysis of plasma required a simple protein precipitation, whereas saliva and urine could be analysed without treatment. The precision of the data obtained ranged from 2--10%. The time consumption for one analysis in routine work is about 20--30 min.

Determination of Thallium in Brain Tissue by Stable Isotope Dilution and Field Desorption Mass Spectrometry

The utility of field desorption mass spectrometry for quantitative metal cation analysis in forensic sciences is demonstrated by the determination of a lethal thallium level in the brain tissue of an experimental animal. Stable isotope dilution and accumulation of the electrically recorded field desorption ion currents with a multi-channel analyzer allowed a direct estimation of thallium in homogenized tissue samples without further pretreatment. Experiments with standard solutions revealed the limit of detection for thallium to be about 10 pg of the metal cation.

Specific method for determining uric acid in serum using high-performance liquid chromatography and gas chromatography-mass spectrometry

A method using a combination of high-performance liquid chromatography and stable-isotope dilution-mass spectrometry is described for the specific quantitation of uric acid in serum. The procedure involves addition of a known amount of [1,3,9-15n]uric acid, as intenral standard, to the serum sample followed by equilibration with the endogenous analyte. After separation from serum proteins, cationic and neutral compounds by anion-exchange chromatography, the purified uric acid is converted into its tetraethyl derivatives. High-performance liquid chromatography is used to isolate the three major isomeric derivatives for measurement of the isotope ratio m/e 280 to m/e 283. This ratio gives the relative abundances of the molecular ions of natural and of labelled tetraethyluric acid, and from it the amount of uric acid in the original serum specimen is determined. Effective separation of tetraethyluric acid isomers can be achieved by adsorption or reversed-phase high-performance liquid chromatography using n-heptane-isopropanol (80:1, v/v) and methanol-water (3:2, v/v), respectively, as solvent systems.

Theoretical considerations in stable isotope dilution mass spectrometry for organic analysis

Theoretical considerations in stable isotope dilution mass spectrometry for organic analysis

Synthesis of deuterium-labeled analogs of cyclophosphamide and its metabolites.

Convenient syntheses are described of d4 analogs of cyclophosphamide and some of its metabolites, potential standards for the quantitative analysis of the drug and its metabolites in human body fluids by stable isotope dilution-mass spectrometry. Base-catalyzed H-D exchange on N-nitrosobis(2-hydroxyethyl)amine gave N-nitrosobis(1,1-dideuterio-2-hydroxyethyl)amine from which bis(2-chloro-1,1-dideuterioethyl)amine (nor-HN2-d4) was readily obtained. Established synthetic routes were then used to convert nor-HN2-d4 into d4 analogs of cyclophosphamide [2-[bis(2-chlorethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide], 4-ketocyclophosphamide [2[BIS(2-chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorin-4-one 2-oxide], and carboxyphosphamide [2-carboxyethyl N-N-bis(2-chloroethyl)phosphorodiamidate], and these analogs were used in a preliminary investigation into the quantitation of the appropriate components in human plasma and urine. Also prepared were d4 analogs of phosphoramide mustard [N,N-bis(2-chloroethyl)phosphorodiamidic acid (cyclohexylammonium salt)] and 3-(2-chloroethyl)oxazolidone and the methyl and trideuteriomethyl esters of phosphoramide mustard.

Major, minor and trace element abundances in samples from the Apollo 17 station 7 boulder: Implications for the origin of early lunar crustal rocks

Apollo 17 station 7 boulder consortia samples were analyzed for major and minor elements by a combined semimicro atomic absorption spectrophotometric and colorimetric procedure. Lithophile trace element abundances were determined by stable isotope dilution mass spectrometry. Three matrix types samples (77135, 77115, and 77075) were found to be KREEP-rich fragment-laden melts with analogues throughout the Apollo 17 landing site. Of the five clasts analyzed, at least one (77115,19, troctolite) is thought to be a cumulate; 77135, 77115, and 77075 are thought to have originated by impact fusion of material with similar composition. This original material may represent a partial melt of a parent material of the composition of an included, shocked norite breccia (77215).

The determination of trace amounts of chromium by stable isotope dilution-mass spectrometry

A simple chemical-mass-spectrometric method for the determination of chromium is described. The method has been applied to steels, copper-base and aluminium-base alloys. The conditions for the thermal ionisation of chromium are given, and the stable isotope-dilution technique is used for quantitative analysis over the range 0·003 to 0·2 per cent. The advantage of the isotope-dilution technique in not requiring quantitative extraction is clearly illustrated by the application of a single method to more than one type of alloy.

Adsorption studies in a fluorinating atmosphere: J J Abassin et al, Com Energie Atomique, CEA-R-2952, 1966, 76 pages (in French)

This chapter presents the fundamental theory and scope of the stable isotope dilution mass-spectrometry (MSID) method. It describes the chemical preparation and the mass spectrometry of the samples, and explains data calculation and quality. MSID is the most accurate technique for determining lanthanide abundances in geochemical materials. The superior quality of the method may be attributed principally to the inherent sensitivity of mass-spectrometers, and to the use of the ideal internal standard—namely, an artificially enriched isotope of each element to be determined. The utilization of isotopic internal standards virtually eliminates potential analytical problems, such as quantitative recovery and instrument calibration. The sensitivity of the mass spectrometer is such that the lower limit of measurable abundance is usually controlled by the purity of the reagents used in preparing the sample for analysis.

Vacuum technology in the production of thin films: W Espe, Feinwerktechnik, 70 (1 and 2), 1966, 2–8, 57–64 (in German)

This chapter presents the fundamental theory and scope of the stable isotope dilution mass-spectrometry (MSID) method. It describes the chemical preparation and the mass spectrometry of the samples, and explains data calculation and quality. MSID is the most accurate technique for determining lanthanide abundances in geochemical materials. The superior quality of the method may be attributed principally to the inherent sensitivity of mass-spectrometers, and to the use of the ideal internal standard—namely, an artificially enriched isotope of each element to be determined. The utilization of isotopic internal standards virtually eliminates potential analytical problems, such as quantitative recovery and instrument calibration. The sensitivity of the mass spectrometer is such that the lower limit of measurable abundance is usually controlled by the purity of the reagents used in preparing the sample for analysis.