Papers by Lorna Sniegoski
TRITIUM-LABELED COMPOUNDS. VIII. CONFIRMATION OF THE POSITION OF THE TRITIUM IN D-GLUCOSE-6-t AND D-GLUCITOL-5-t
... Lorna T. Sniegoski and Horace S. Isbell ... Consequently, all of the tritium in D-glucose-£-£... more ... Lorna T. Sniegoski and Horace S. Isbell ... Consequently, all of the tritium in D-glucose-£-£ is at Cl or C-6. Next, a sample of the D-glucose-6>-£ was oxidized with iodine by the Kline-Acree method [8] to potas-sium D-gluconate-£-£, which contains no hydrogen or tritium attached ...
TRITIUM-LABELED COMPOUNDS VII. ISOTOPE EFFECTS IN THE OXIDATION OF d- MANNITOLS-C¹ⴠAND d-MANNITOLS-t TO d-FRUCTOSES
D-Mannitols, labeled either with carbon-14 at C1, C2, or C3, or with ; tritium attached to C1, C2... more D-Mannitols, labeled either with carbon-14 at C1, C2, or C3, or with ; tritium attached to C1, C2, or C3, were prepared. After oxidation by Acetobacter ; suboxydans, the distribution of radioactivity in each of the resulting labeled D-; fructoses was determined. Labeled D-mannitol is unique among the hexitols in ; that it may be oxidized by A. suboxydans in either the labeled or the unlabeled ; part of the molecule. Except in the oxidation of D-mannitol-2-t, the competing ; reactions result in the formation of a mixture of D-fructoses, each having ; radioactivity in one of two different positions. Hence, the isotope effect, k*/; k, (where k* and k are, respectively, the rate constants for oxidation in the ; labeled and in the unlabeled part of the labeled emannitol molecule) is the ratio ; of the activities at the two positions of the product, D-fructose. The following ; isotope effects were found for the bacterial oxidation of labeled D-mannitols: ; for D-mannitol-2-C¹â´, k*/k = 0.93; for Dmannitol-2-t, k*/k = 0.23; and for ; D-mannitol-3-t, k*/k = 0.70. For D-mannitols labeled at other positions, no ; isotope effect was detected, since k*/k was unity. The large isotope effect for ; D-mannitol-2-t is indicative of rupture of the C2-H bond in the rate determining ; process. It is suggested that the secondary isotope effect for tritium at C3 ; indicates hyperconjugation of the C3 hydrogen atom in the activated enzyme--; substrate complex; the lack of such effect for tritium at C1 may be due to ; unfavorable steric conditions for hyperconjugation of the C1 hydrogen atoms in ; the complex. The following substances were prepared and their isotopic ; distributions determined: D-fructose1,6-C¹ⴠand D-fructose-1,6-t (from 1-; labeled D-mannitols); D-fructose-2,5-C¹ⴠand D-fructose-5-t (from 2-labeled ; e-mannitols); and D-fructose-3,4-C¹ⴠand D-fructose-3,4-t (from 3-labeled D-; mannitols). A procedure, employing D-fructose-1,6-C¹ⴠas an internal ; standard, was devised for the analysis of D-fructose-3,4-t. (auth);
International Journal of Radiation Applications and Instrumentation Part A Applied Radiation and Isotopes
Journal of Analytical Toxicology, 1996
Fourteen laboratories interested in the analysis of human hair for drugs of abuse participated in... more Fourteen laboratories interested in the analysis of human hair for drugs of abuse participated in a fourth interlaboratory study to determine how well drugs could be detected and quantitated in hair. The drugs of abuse included cocaine, benzoylecgonine, cocaethylene, codeine, morphine, and 6-monoacetylrnorphine. The hair samples analyzed were in the form of short segments and included hair from drug users, soaked hair (drug-free hair into which drugs had been soaked), and drug-free hair. Results from the study show that the laboratories performed well qualitatively, but that there was a large amount of scatter in quantitative results. Various methods were used to extract the drugs from the hair, and the most commonly used approaches, HCI extractions, methanol extractions, and enzyme digestions, all gave comparable results. Gas chromatography-mass spectrometry (GC-MS) was the most commonly used analytical technique. Of the laboratories using GC-MS, some produced consistently good results, whereas others produced results of poorer quality. Two laboratories using liquid chromatography-mass spectrometry produced good results, but the one laboratory using liquid chromatography without mass spectrometric detection produced less accurate results. Laboratories that reported good results on control material sent with the unknowns generally performed better on the unknowns than did laboratories whose results on the control were less accurate.
Journal of Analytical Toxicology, 1993
Methods for extraction of cocaine, some of Its metabolites, morphine, and codeine from hair and m... more Methods for extraction of cocaine, some of Its metabolites, morphine, and codeine from hair and methods for analyzing the extracts have been investigated. Results of these studies have shown that extractions with O.1N HCl are efficient at removing the target compounds from hair and appear to be as effective as enzymatic digestions that dissolve the hair. GC/MS with either electron ionization or chemical ionization was found to provide accurate and unambiguous determinations of the target compounds. Tandem mass spectrometry (MS/MS) also provided accurate results when performed on extracts from hair, but results were ambiguous when MS/MS was performed on hair segments directly. Environmental issues, including the removal of powdered and vapor-deposited cocaine from the hair surface and the effect of various hair treatments on the levels of cocaine entrapped in hair, have also been investigated. Removal of cocaine deposited on hair was incomplete by all approaches tested, making differentiation of hair of cocaine users from hair with environmental exposure of cocaine difficult. Cocaethylene, a cocaine metabolite believed to be formed in the liver, was found in the hair of some cocaine users and may be a good marker for proving drug use. Common hair treatments, such as shampoos, conditioners, and peroxide bleaches, reduced cocaine levels in a fortified hair material by 60 to 80% after 30 treatments. Finally, to assist laboratories in evaluating the accuracy of their methods, two human hair reference materials with recommended concentrations of cocaine, benzoylecgonine, morphine, and codeine determined by GC/MS have been developed.
Forensic Science International, 1993
Eleven laboratories interested in the analysis of human hair for drugs of abuse participated in a... more Eleven laboratories interested in the analysis of human hair for drugs of abuse participated in a study to determine how well drugs could be detected and quantified in hair. For the two exercises completed to date, substances to be determined were limited to cocaine, benzoylecgonine, and morphine. Samples sent to the participating laboratories included hair from drug users, drug-free hair, and hair into which drugs had been soaked. For the first exercise, the hair samples were sent as powders; for the second, they were in the form of short segments. Results from these studies have shown that the laboratories, with a few exceptions, have performed very well qualitatively. However, scatter in quantitative results was high. Various approaches were used to liberate drugs from the hair, with the most commonly used, acid extractions and enzyme digestions, producing similar results. Laboratories using GUMS generally performed well and reported no false positives. In contrast, one laboratory analyzing hair directly using MS/MS without extractions produced three of the four false positives and the worst quantitative results.
Simultaneous Quantification of Homocysteine and Folate in Human Serum or Plasma Using Liquid Chromatography/Tandem Mass Spectrometry
Analytical Chemistry, Jun 1, 2005
A unified extraction and quantification procedure based on stable isotope-dilution liquid chromat... more A unified extraction and quantification procedure based on stable isotope-dilution liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been developed for the simultaneous determination of total homocysteine and folate (5-methyltetrahydrofolic acid and folic acid) levels in human serum and plasma. This is the first report documenting the simultaneous extraction and quantification of these structurally dissimilar analytes. Analytes are quantitatively isolated from samples (500 microL) prior to LC/MS/MS analysis using a two-step stabilization process combined with C18 solid-phase extraction. The method exhibits excellent linearity over 4 orders of magnitude for each analyte. Measurement repeatability (RSD, N = 2) ranged from 0.3% to 3% for all analytes over 1 day of analysis. Total method variability (RSD, N = 6) ranged from 0.7% to 10% for all analytes over three independent days of analysis. The accuracy and practical applicability of the method were demonstrated by applying the method to the quantitative determination of each analyte in a new NIST serum Standard Reference Material (NIST SRM 1955 Homocysteine and Folate in Frozen Human Serum) and in a small subset of normal donor plasma samples.
Modifications to the NIST reference measurement procedure (RMP) for the determination of serum glucose by isotope dilution gas chromatography/mass spectrometry
Analytical and Bioanalytical Chemistry, Apr 27, 2010
The definitive method (DM), now known as the reference measurement procedure (RMP), for the analy... more The definitive method (DM), now known as the reference measurement procedure (RMP), for the analysis of glucose in serum was originally published in 1982 by the National Institute of Standards and Technology (NIST). Over the years the method has been subject to a number of modifications to adapt to newer technologies and simplify sample preparation. We discuss here an adaptation of the method associated with serum glucose measurements using a modified isotope dilution gas chromatography/mass spectrometry (ID-GC/MS) method. NIST has used this modified method to certify the concentrations of glucose in SRM 965b, Glucose in Frozen Human Serum, and SRM 1950, Metabolites in Human Plasma. Comparison of results from the revised method with certified values for existing Standard Reference Materials (SRMs) demonstrated that these modifications have not affected the quality of the measurements, giving both good precision and accuracy, while reducing the sample preparation time by a day and a half.
Direct calibration of GC/MS systems using SRM (Standard Reference Material) gas cylinders. Project report, January 1984-August 1985
A cryogenic trapping system has been developed for use in calibrating GC/MS systems for the analy... more A cryogenic trapping system has been developed for use in calibrating GC/MS systems for the analysis of volatile organic compounds. This system provides for direct Standard Reference Material (SRM) traceability on data generated on gaseous samples. The cryogenic trap is a coil of stainless steel tubing immersed in a cryogen to trap and preconcentrate organic species present in a gaseous
Clinical Chemistry
Background: There is a need for a critically evaluated reference method for thyroxine to provide ... more Background: There is a need for a critically evaluated reference method for thyroxine to provide an accuracy base to which routine methods can be traceable. We describe a candidate reference method involving isotope-dilution coupled with liquid chromatography/ mass spectrometry. Methods: An isotopically labeled internal standard, thyroxine-d 5 , was added to serum, followed by equilibration, protein precipitation, and ethyl acetate and solid-phase extractions to prepare samples for liquid chromatography-mass spectrometry electrospray ionization (LC/MS-ESI) analysis. For separation, a Zorbax Eclipse XDB-C 18 column was used with a mobile phase consisting of 1 mL/L acetic acid in acetonitrile-water (32:68 by volume) for positive ions and a Zorbax Extend-C 18 column with a mobile phase consisting of 2 mL/L ammonium hydroxide in methanol-water (32:68 by volume) for negative ions. [M ؉ H] ؉ ions at m/z 778 and 783 for thyroxine and its labeled internal standard were monitored for positive ions and [M ؊ H] ؊ ions at m/z 776 and 781 for negative ions. Samples of frozen serum pools were prepared and measured in three separate sets. Results: Within-set CVs were 0.2-1.0%. The correlation coefficients of all linear regression lines (measured intensity ratios vs mass ratios) were 0.999 -1.000. Positive-and negative-ion measurements agreed with a mean difference of 0.45% at three concentrations (50, 110, and 168 g/L). The detection limits (at a signal-tonoise ratio of ϳ3 to 5) were 30 and 20 pg for positive and negative ions, respectively. The results from the LC/MS-ESI method were within 1 SD of the composite means from many routine clinical methods, although it appears that the clinical method means may be biased high by 4 -5 g/L across the concentrations. Some routine clinical methods may be biased by up to 20% at low concentrations.
Journal of Research of the National Bureau of Standards, 1988
The compound 3-quinuclidinyl benzilate (BZ) is a potent muscarinic cholinergic antagonist that ca... more The compound 3-quinuclidinyl benzilate (BZ) is a potent muscarinic cholinergic antagonist that can produce incapacitation at very small doses . As such it can be used as a powerful psychochemical warfare agent. In response to the scheduled destruction of U.S. military stockpiles of BZ and the increased potential for worker exposure, our laboratory has developed a specific confirmatory test for human exposure to BZ. The test determines the amount of the parent compound in the urine as well as the two major metabolites, quinuclidinol (Q) and benzilic acid (BA) which are formed by hydrolysis as shown in figure 1. Previous work in our laboratory demonstrated that BA and Q could be determined in urine at their target concentration of 5 ng/mL as based on a proposed acceptable exposure level. The work described here demonstrates the recovery of the parent compound from urine at its target level and the incorporation of this method into an overall test for exposure to BZ.
Clinical chemistry, 2002
There is a need for a critically evaluated reference method for thyroxine to provide an accuracy ... more There is a need for a critically evaluated reference method for thyroxine to provide an accuracy base to which routine methods can be traceable. We describe a candidate reference method involving isotope-dilution coupled with liquid chromatography/mass spectrometry. An isotopically labeled internal standard, thyroxine-d(5), was added to serum, followed by equilibration, protein precipitation, and ethyl acetate and solid-phase extractions to prepare samples for liquid chromatography-mass spectrometry electrospray ionization (LC/MS-ESI) analysis. For separation, a Zorbax Eclipse XDB-C(18) column was used with a mobile phase consisting of 1 mL/L acetic acid in acetonitrile-water (32:68 by volume) for positive ions and a Zorbax Extend-C(18) column with a mobile phase consisting of 2 mL/L ammonium hydroxide in methanol-water (32:68 by volume) for negative ions. [M + H](+) ions at m/z 778 and 783 for thyroxine and its labeled internal standard were monitored for positive ions and [M - H](...
An isotope-dilution mass-spectrometric (IDMS) method for the determination of vitamin-C in milk
Journal of Research of the National Bureau of Standards, 1988
ABSTRACT
CCQM-K11: The determination of glucose in serum
Metrologia, 2003
A Key Comparison on the determination of glucose in human serum organized by the Consultative Com... more A Key Comparison on the determination of glucose in human serum organized by the Consultative Committee on Amount of Substance (CCQM) was carried out in 2001. To address the measurement traceability needs of the clinical chemistry community, the CCQM is undertaking Key Comparisons to document the capabilities of national metrology institutes (NMIs) that provide measurement services in this area. This
Syntheses of 1-dodecyl-d25 phosphate
Journal of Labelled Compounds and Radiopharmaceuticals, 1983
ABSTRACT
Synthesis of 3-quinuclidinol-18O, benzilic-d5 acid, and 3-quinuclidinyl-18O benzilate-d5
Journal of Labelled Compounds and Radiopharmaceuticals, 1989
Page 1. Journal of Labelled Compoundr and Radiopharmaceuticals-Vol. XXVII, No. 9 SYNTHESIS OF 3-Q... more Page 1. Journal of Labelled Compoundr and Radiopharmaceuticals-Vol. XXVII, No. 9 SYNTHESIS OF 3-QUINUCLIDINOL-180, BENZILIC-d5 ACID, AND 3 -QUINUCLIDINYL-'~ 0 BENZIIATE-d5 Lorna T. Sniegoski, Gary D. Byrd ...
Journal of Agricultural and Food Chemistry, 1989
Clinical Chemistry, 2007
Background: To meet recommendations given by the Laboratory Working Group of the National Kidney ... more Background: To meet recommendations given by the Laboratory Working Group of the National Kidney Disease Education Program for improving serum creatinine measurements, NIST developed standard reference material (SRM) 967 Creatinine in Frozen Human Serum. SRM 967 is intended for use by laboratories and in vitro diagnostic equipment manufacturers for the calibration and evaluation of routine clinical methods. Methods: The SRM was produced from 2 serum pools with different creatinine concentrations. The concentrations were certified using a higher-order isotope-dilution GC-MS method and an isotope-dilution LC-MS method. The LC-MS method is a potential higher-order reference measurement procedure. Results: The GC-MS mean (CV) concentrations were 67.0 (0.9%) mol/L for serum pool 1 and 346.1 (0.45%) mol/L for serum pool 2. The LC-MS results were 66.1 (0.2%) mol/L and 346.3 (0.2%) mol/L, respectively. For serum pool 1, there was a 1.4% difference between the mean GC-MS and LC-MS measurements, and a 0.10% difference for serum pool 2. The results from the 2 methods were combined to give the certified concentrations and expanded uncertainties. Conclusions: The certified concentration (expanded uncertainty) of SRM 967 was 66.5 (1.8) mol/L for serum pool 1 (a value close to the diagnostically important concentration of 88.4 mol/L) and 346.2 (7.4) mol/L for serum pool 2 (a concentration corresponding to that expected in a patient with chronic kidney disease).
Simultaneous Quantification of Homocysteine and Folate in Human Serum or Plasma Using Liquid Chromatography/Tandem Mass Spectrometry
Analytical Chemistry, 2005
A unified extraction and quantification procedure based on stable isotope-dilution liquid chromat... more A unified extraction and quantification procedure based on stable isotope-dilution liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been developed for the simultaneous determination of total homocysteine and folate (5-methyltetrahydrofolic acid and folic acid) levels in human serum and plasma. This is the first report documenting the simultaneous extraction and quantification of these structurally dissimilar analytes. Analytes are quantitatively isolated from samples (500 microL) prior to LC/MS/MS analysis using a two-step stabilization process combined with C18 solid-phase extraction. The method exhibits excellent linearity over 4 orders of magnitude for each analyte. Measurement repeatability (RSD, N = 2) ranged from 0.3% to 3% for all analytes over 1 day of analysis. Total method variability (RSD, N = 6) ranged from 0.7% to 10% for all analytes over three independent days of analysis. The accuracy and practical applicability of the method were demonstrated by applying the method to the quantitative determination of each analyte in a new NIST serum Standard Reference Material (NIST SRM 1955 Homocysteine and Folate in Frozen Human Serum) and in a small subset of normal donor plasma samples.
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Papers by Lorna Sniegoski