Reactions of gaseous ions. I. Methane and ethylene.

At elevated pressures in a mass spectrometer ion source reactions occur between certain ions and the neutral species present. We have studied the various secondary ions formed in methane and ethylene at elevated pressures and have determined the reactions by which they are formed and the rates of these reactions. The rates are all extremely fast. The reaction rates have been treated by classical collision theory and it has been shown that to a fair approximation the cross-sections and reaction rate constants can be predicted from a simple balance of rotational and polarization forces. [Reprinted from J. Am. Chem. Soc. 1957; 79: 2419.]

The early days of chemical ionization: A reminiscence.

A narrative account is given of the events leading to the discovery of chemical ionization in the laboratories of the Humble Oil and Refining Company in 1965. The discovery was unplanned in the sense that it resulted from the observation of unanticipated phenomena made In the course of experiments undertaken for a different purpose. However, the sequence of events which occurred IS an Illustration of the discovery of a practical, useful result from a program of research which was primarily of a basic nature but with ancillary awareness of possible practical implications.

Limits for the use of (18O)cholesterol and (18O)sitosterol in studies of cholesterol metabolism in humans.

The present study was undertaken in order to determine whether 18O-labeled sterols could be used in place of 14C-sterols in clinical studies of cholesterol metabolism. (3 beta-18OH)Cholesterol and (3 beta-18OH)sitosterol were simply and inexpensively synthesized and precisely and accurately quantified by gas chromatography/mass spectrometry. 18O-Sterols added to fecal homogenate and saponified were completely recovered. However, in a series of validation studies in humans, the fecal recoveries of orally administered (18O)cholesterol and (18O)sitosterol were significantly lower than the recoveries of 14C-sterols given simultaneously. We found that the losses were largely limited to the coprostanol and ethylcoprostanol fecal metabolites. In vitro fecal incubations of 18O-sterols and unlabeled water or of unlabeled sterols with H2(18)O indicated that the losses occurred during fecal bacterial metabolism and were likely due to 3 beta-oxygen exchange with the oxygen of water, possibly via a 3-ketosteroid intermediate. These data indicate that (18O)cholesterol and (18O)sitosterol are invalid tracers for the measurement of human cholesterol metabolism by methods based on fecal sterol recovery.

Quantification of the sulfates of 16 alpha-hydroxy androgens that are possible precursors of estriol-3-sulfate in human breast cyst fluid.

The concentration of 16 alpha-hydroxydehydroepiandrosterone-3-sulfate (16 alpha-OHDHAS) was determined in 29 samples of human breast cyst fluid (BCF) and in 15 of these, androst-5-ene-3 beta,16 alpha,17 beta-triol-3-sulfate (A-TriolS) was also assayed. The median value of both was about 100 ng/mL and the ranges were from 1.4 to about 1800 ng/mL. There was a significant association in the values for the two sulfates (p less than 0.05). These concentrations are consistent with a role for 16 alpha-hydroxy androgens as possible precursors for estriol-3-sulfate. The latter is highly elevated relative to other body fluids in BCF. The androgens also correlated directly with the concentrations of K+, an indicator of apocrine proliferation of breast cysts.

A rapid, sensitive mass spectrometric method for investigating microscale chemical reactions of surface adsorbed peptides and proteins.

A new mass spectrometric method for measuring the products of reactions of surface adsorbed peptides and proteins is described. The technique is rapid, convenient, and sensitive and provides detailed information concerning the molecular weights of the reaction products and the rate and extent of reaction. The properties of the technique are illustrated by an investigation of cleavage reactions of the disulfide bonds in bovine insulin, cyclic somatostatin, and conotoxin G1 utilizing the reducing agent dithiothreitol.

Androsterone long chain fatty acid esters in human breast cyst fluid.

We reported previously that incubation of [3H] androsterone in homogenates of human breast tumor resulted in production of long chain fatty acid esters of androsterone (A-LCFE). To identify the individual A-LCFE, breast tumor homogenates were incubated with androsterone, then submitted to solvent extraction, Celite chromatography, high pressure liquid chromatography and OH- negative chemical ionization mass spectrometry. The (M-1)-ions of the oleate, linoleate, palmitoleate, palmitate, arachidonate, and stearate esters of androsterone were produced. The first 3 cited unsaturated esters accounted for over 90% of the total. Since fibrocystic disease of the breast is a reported risk factor for the development of breast cancer, breast cyst fluids were analyzed for A-LCFE as part of an overall program to relate endocrine profiles in cyst fluid to the incidence of cancer. Breast cyst fluids were analyzed for total A-LCFE by a method involving solvent extraction, saponification, purification of the liberated androsterone, and then quantification of the steroid by RIA. The 10 fluids analyzed contained 0.52-3.79 ng/ml fatty acid esters, measured as androsterone. In 4 of these samples, the individual A-LCFE were analyzed by mass spectrometry. As in the incubation study, the unsaturated fatty acid esters predominated. In 3 samples, palmitoleate and in 1 sample, oleate predominated. The palmitate varied from undetectable to 25% of the total. The divergent total concentrations and profiles of A-LCFE indicate potential parameters for correlations with the subsequent course of fibrocystic disease of the breast.

Identification of 19-nor-corticosterone in rat urine.

19-Nor-corticosterone (19-nor-B) was isolated from a pool of urine collected from Wistar-Kyoto (WKY) rats. Identity was established by comparison of chromatographic mobilities with standard 19-nor-B both as the free compound and diacetate derivative. Comparison of the gas chromatographic-mass spectra of the urinary product and standard 19-nor-B as the diacetate following isolation by high pressure liquid chromatography (HPLC) confirmed the identity of the urinary product to be 19-nor-B. This demonstration that 19-nor-B is a naturally occurring product in addition to 19-nor-deoxycorticosterone supports the concept of the existence of a biosynthetic pathway for the formation of the 19-nor-corticosteroids.

Determination of total body water by deuterium isotope dilution measurements using chemical ionization mass spectrometry.

Two chemical ionization mass spectrometric methods were developed for direct determination of deuterium in water in the range of 0.0-0.6% 2H2O. One of them utilizes the batch inlet system, methane as the reagent gas, and the peak matching device of a magnetic sector mass spectrometer. The second one utilizes the directly-coupled gas chromatograph of a quadrupole mass spectrometer and computer control for ion selection and data processing. In this method the water itself serves as the reagent gas. The deuterium concentration is calculated from the ratio of ion intensities at m/z 20 (2HH2O+) and m/z 19 (H3O+). We have used these methods to determine total body water in 350 human subjects, which entailed making 900 measurements over a period of four years. Comparisons were made in 200 subjects of our results with those obtained by the creatinine method. No significant differences were found.

Effects of liver disease on fecal excretion of methadone and its unconjugated metabolites in maintenance patients. Quantitation by direct probe chemical ionization mass spectrometry.

This study was performed to determine the amounts of methadone and unconjugated metabolites excreted in feces of otherwise healthy methadone maintained patients and to determine whether the metabolism and elimination of methadone, as assessed by analysis of feces, is altered in patients with liver disease. The method for analysis of fecal homogenates was modified from the methods previously developed by our laboratories for the quantitative measurements of methadone and its metabolites in urine, using chemical ionization mass spectrometry with direct probe insertion of specimens to improve sensitivity of analysis. Analysis of fecal homogenates from unmedicated volunteer patients showed that interferences at the mass range of interest (m/z 264 to 326) were usually very small, even smaller than those found in analyses of unmedicated urine specimens, and therefore would not introduce significant error into analysis. Nineteen patients stabilized in chronic methadone treatment for over two years were studied, including five otherwise healthy males and 14 patients with chronic liver disease (nine males and five females). Fecal collections were made over 24 h periods. Three consecutive fecal samples were collected over the required number of sequential 24 h intervals. Each of these fecal conditions was analysed separately. Each analysis was made in triplicate, following extraction procedures. The concentrations of methadone and unconjugated metabolites varied due to biological, pharmacological, and analytical factors and ranged from 3.8 ng ml-1 to 42 micrograms ml-1 of fecal homogenate. The relative concentrations of each, in descending order, were pyrrolidine, pyrrolidone (plus hydroxymethadone), methadone, pyrroline, and methadol.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholest-5-ene-3 beta, 26-diol: synthesis and biomedical use of a deuterated compound.

To further studies of the metabolism of 26-hydroxycholesterol in fetal and neonatal life, a deuterated compound was prepared from kryptogenin by Clemmensen reduction. The spectra of the deuterated 26-hydroxycholesterol showed that five to nine deuterium atoms were incorporated per 26-hydroxycholesterol molecule, with the maximum incorporation of eight deuterium atoms. The deuterated compound was recovered unchanged from the feces of a child following oral administration. Comparison of the ratio of deuterated to protium compound indicated the presence of an endogenous pool of 26-hydroxycholesterol. Parenteral administration of the compound to a hamster indicated metabolism to deuterated chenodeoxycholic acid. The compound is useful as an isotope tracer for studies of the endogenous metabolism of 26-hydroxycholesterol.

Gas chromatographic--mass spectrometric detection of circulating plasticizers in surgical patients.

Gas chromatographic and gas chromatographic--mass spectrometric analytical techniques were employed to quantitate and confirm levels of circulating organic plasticizers in critically ill surgical patients. Two plasticizers, dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP), have been identified. DEHP can be found in many plastic medical devices. The DEHP levels were significant soon after transfusion or in the presence of renal dysfunction. The source of DBP is not clear at present and requires further study. The prevention of this contamination and the toxicity of these plasticizers should be investigated to ensure the safe use of plastic medical devices.

Effects of liver disease on urinary excretion of methadone and metabolites in maintenance patients: quantitation by direct probe chemical ionization mass spectrometry.

This study was performed to define the amounts of methadone and metabolites excreted in urine in otherwise healthy maintenance patients, and to determine whether the metabolism and elimination of methadone, as assessed by analyses of urines, is altered in patients with liver disease. A method was developed for the simultaneous quantitation of methadone and six of its major and minor metabolites using chemical ionization mass spectrometry with direct probe introduction to increase sensitivity for analyses of the minor metabolites. Analyses of urine from unmedicated volunteers showed that the interferences at the mass range of interest (264-326) were usually small and therefore would not introduce significant error into analysis. Nineteen patients well-stabilized in chronic long-term methadone treatment were studied, five otherwise healthy males and fourteen patients with chronic liver disease (nine males and four females). Twenty-four hour urine collections were made and analyzed following extraction procedures. The concentrations of methadone and the major pyrrolidine metabolite exceeded 1 microgram ml-1 in all cases; the concentration (listed in descending order) of pyrrolidone, pyrroline, hydroxymethadone, hydroxypyrroline, methadol and hydroxypyrrolidine were all less than 1 microgram ml-1. The total 24 hour urinary excretion of methadone and its metabolites was 48.3% (+/- 1.71 SEM) in otherwise healthy patients but was significantly lower, 32.6% (+/- 3.19 SEM) in patients with liver disease (p less than 0.05). The total 24 hour excretion of the pyrrolidone metabolite, the end product of two pathways of methadone metabolism, was also significantly reduced in patients with liver disease (p less than 0.05). Females with liver disease had significantly higher ratios of pyrrolidine to methadone than did males with liver disease (p less than 0.05).

[OH]- negative chemical ionization mass spectrometry. Reactions of [OH]- with methadone, l-alpha-acetylmethadol and their metabolites.

The [OH]- chemical ionization spectra of methadone and three metabolites and of l-alpha-methadol and six metabolites are presented. The spectra are simple, but the methadol compounds exhibit much fragmentation. The ionization sensitivity is somewhat greater than that in CH4 positive chemical ionization.