Michele M Schantz

National Institute of Standards and Technology, Gaithersburg, MD, United States

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Publications (133)287.13 Total impact

  • Metrologia 07/2014; 51(1A):8010. · 1.90 Impact Factor
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    ABSTRACT: The National Institute of Standards and Technology (NIST), in collaboration with the National Institutes of Health (NIH), has developed a Standard Reference Material (SRM) to support technology development in metabolomics research. SRM 1950 Metabolites in Human Plasma is intended to have metabolite concentrations that are representative of those found in adult human plasma. The plasma used in the preparation of SRM 1950 was collected from both male and female donors, and donor ethnicity targets were selected based upon the ethnic makeup of the U.S. population. Metabolomics research is diverse in terms of both instrumentation and scientific goals. This SRM was designed to apply broadly to the field, not towards specific applications. Therefore, concentrations of approximately 100 analytes, including amino acids, fatty acids, trace elements, vitamins, hormones, selenoproteins, clinical markers, and perfluorinated compounds (PFCs), were determined. Value assignment measurements were performed by NIST and the Centers for Disease Control and Prevention (CDC). SRM 1950 is the first reference material developed specifically for metabolomics research.
    Analytical Chemistry 11/2013; · 5.70 Impact Factor
  • Margarete S Nocun, Michele M Schantz
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    ABSTRACT: Oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) have recently received much attention in discussions regarding the negative impacts of particulate matter (PM) on human health and the environment. The National Institute of Standards and Technology provides several environmental matrix standard reference materials (SRMs) with certified and reference values for polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs. In this study, the concentrations of oxygenated PAHs are determined in three air PM SRMs (1649b, 1648a, and 2786) and three diesel PM SRMs (1650b, 2975, and 1975) using two independent gas chromatography-mass spectrometry methods. Concentrations of oxy-PAHs were at the milligrams per kilogram level with higher overall concentrations in diesel PM (up to 50 mg/kg for 9,10-anthraquinone). One of the highest oxy-PAH concentrations (up to 5 mg/kg) measured in the air particulate SRMs was for 7,12-benz[a]anthracenquinone. These results suggest that oxygenated PAHs should not be neglected in the analysis of PM as their concentrations can be as high as those of some PAHs and are one to two orders of magnitude higher than those for nitro-PAHs.
    Analytical and Bioanalytical Chemistry 04/2013; · 3.66 Impact Factor
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    ABSTRACT: The National Institute of Standards and Technology administers quality assurance programs devoted to improving measurements of nutrients and related metabolites in foods, dietary supplements, and serum and plasma samples. These programs have been developed in collaboration with the National Institutes of Health to assist measurement communities in their efforts to achieve accurate results that are comparable among different laboratories and over time. Targeted analytes include micronutrients, botanical markers, nutritional elements, contaminants, fatty acids, and vitamin D metabolites.
    Analytical and Bioanalytical Chemistry 04/2013; · 3.66 Impact Factor
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    ABSTRACT: As part of a collaboration with the National Institutes of Health's Office of Dietary Supplements and the Food and Drug Administration's Center for Drug Evaluation and Research, the National Institute of Standards and Technology has developed Standard Reference Material (SRM) 3274 Botanical Oils Containing Omega-3 and Omega-6 Fatty Acids and SRM 3275 Omega-3 and Omega-6 Fatty Acids in Fish Oil. SRM 3274 consists of one ampoule of each of four seed oils (3274-1 Borage (Borago officinalis), 3274-2 Evening Primrose (Oenothera biennis), 3274-3 Flax (Linium usitatissimum), and 3274-4 Perilla (Perilla frutescens)), and SRM 3275 consists of two ampoules of each of three fish oils (3275-1 a concentrate high in docosahexaenoic acid, 3275-2 an anchovy oil high in docosahexaenoic acid and eicosapentaenoic acid, and 3275-3 a concentrate containing 60 % long-chain omega-3 fatty acids). Each oil has certified and reference mass fraction values for up to 20 fatty acids. The fatty acid mass fraction values are based on results from analyses using gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS). These SRMs will complement other reference materials currently available with mass fractions for similar analytes and are part of a series of SRMs being developed for dietary supplements.
    Analytical and Bioanalytical Chemistry 02/2013; · 3.66 Impact Factor
  • Metrologia 01/2013; 50. · 1.90 Impact Factor
  • Metrologia 01/2013; 50. · 1.90 Impact Factor
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    ABSTRACT: Four new Standard Reference Materials (SRMs) have been developed to assist in the quality assurance of chemical contaminant measurements required for human biomonitoring studies, SRM 1953 Organic Contaminants in Non-Fortified Human Milk, SRM 1954 Organic Contaminants in Fortified Human Milk, SRM 1957 Organic Contaminants in Non-Fortified Human Serum, and SRM 1958 Organic Contaminants in Fortified Human Serum. These materials were developed as part of a collaboration between the National Institute of Standards and Technology (NIST) and the Centers for Disease Control and Prevention (CDC) with both agencies contributing data used in the certification of mass fraction values for a wide range of organic contaminants including polychlorinated biphenyl (PCB) congeners, chlorinated pesticides, polybrominated diphenyl ether (PBDE) congeners, and polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners. The certified mass fractions of the organic contaminants in unfortified samples, SRM 1953 and SRM 1957, ranged from 12 ng/kg to 2200 ng/kg with the exception of 4,4'-DDE in SRM 1953 at 7400 ng/kg with expanded uncertainties generally <14 %. This agreement suggests that there were no significant biases existing among the multiple methods used for analysis.
    Analytical and Bioanalytical Chemistry 11/2012; · 3.66 Impact Factor
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    ABSTRACT: Drinking yerba maté, common in southern South America, may increase the risk of esophageal squamous cell carcinoma (ESCC). In 2006, we found high but variable polycyclic aromatic hydrocarbon (PAH) content in commercial yerba maté samples from eight Brazilian brands. The PAH content of new samples from the same brands, purchased in 2008, and four brands from a single manufacturer processed in different ways, obtained in 2010, were quantified to determine whether PAH concentration was still high, PAH content variation was brand specific, and whether processing method affects PAH content of commercial yerba maté. Concentrations of individual PAHs were quantified using gas chromatography/mass spectrometry with deuterated PAHs as internal standards. Median total PAH concentration was 1500 ng/g (range: 625 to 3710 ng/g) and 1090 ng/g (621 to 1990 ng/g) in 2008 and 2010 samples, respectively. Comparing 2006 and 2008 samples, some brands had high PAH concentrations in both years, while PAH concentration changed considerably in others. Benzo[a]pyrene concentrations ranged from 11.9 to 99.3 ng/g and 5.11 to 21.0 ng/g in 2008 and 2010 samples, respectively. The 2010 sample processed without touching smoke had the lowest benzo[a]pyrene content. These results support previous findings of very high total and carcinogenic PAH concentrations in yerba maté, perhaps contributing to the high incidence of ESCC in southern South America. The large PAH content variation by brand, batch and processing method suggests it may be possible to reduce the content of carcinogenic PAHs in commercial yerba maté, making it a healthier beverage.
    Environmental Science & Technology 10/2012; · 5.26 Impact Factor
  • Michele M Schantz, Elizabeth McGaw, Stephen A Wise
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    ABSTRACT: Four particulate matter Standard Reference Materials (SRMs) available from the National Institute of Standards and Technology (NIST) were used to evaluate the effect of solvent, number of static cycles and static times, pressure, and temperature when using pressurized liquid extraction (PLE) for the extraction of polycyclic aromatic hydrocarbons (PAHs) and nitrated-PAHs. The four materials used in the study were SRM 1648a Urban Particulate Matter, SRM 1649b Urban Dust, SRM 1650b Diesel Particulate Matter, and SRM 2975 Diesel Particulate Matter (Industrial Forklift). The results from the study indicate that the choice of solvent, dichloromethane compared to toluene and toluene/methanol mixtures, had little effect on the extraction efficiency. With three to five extraction cycles, increasing the extraction time for each cycle from 5 to 30 min had no significant effect on the extraction efficiency. The differences in extraction efficiency were not significant (with over 95% of the differences being <10%) when the pressure was increased from 13.8 to 20.7 MPa. The largest increase in extraction efficiency occurred for selected PAHs when the temperature of extraction was increased from 100 to 200 °C. At 200 °C naphthalene, biphenyl, fluorene, dibenzothiophene, and anthracene show substantially higher mass fractions (>30%) than when extracted at 100 °C in all the SRMs studied. For SRM 2975, large increases (>100%) are also observed for some other PAHs including benz[a]anthracene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, benzo[ghi]perylene, and benzo[b]chrysene when extracted at the higher temperatures; however, similar trends were not observed for the other diesel particulate sample, SRM 1650b. The results are discussed in relation to the use of the SRMs for evaluating analytical methods.
    Analytical Chemistry 09/2012; 84(19):8222-31. · 5.70 Impact Factor
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    ABSTRACT: Linzhou, China has one of the highest rates of esophageal squamous cell carcinoma in the world. Exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP), may have a role in this increased risk. To better understand PAH sources, we measured PAHs in the air and food of 20 non-smokers over multiple days and compared the concentrations with a urinary PAH biomarker, 1-hydroxypyrene glucuronide (1-OHPG). Sampling occurred over 4 consecutive days. Kitchen air samples (days 2-3) and duplicate diet samples (days 1-4) were analyzed for 14 or more unique PAHs, including BaP. Daily urine samples (days 1-3) were analyzed for 1-OHPG. Mixed-effects models were used to evaluate the associations between air or food PAH concentrations and urine 1-OHPG concentrations. The median kitchen air BaP concentration was 10.2 ng/m(3) (interquartile range (IQR): 5.1-20.2 ng/m(3)). The median daily food BaP concentration and intake were 0.08 ng/g (IQR=0.04-0.16 ng/g) and 86 ng/day (IQR=41-142 ng/day), respectively. The median 1-OHPG concentration was 3.36 pmol/ml (IQR=2.09-6.98 pmol/ml). In mixed-effects models, 1-OHPG concentration increased with same-day concentration of food BaP (P=0.07). Although PAH concentrations in air were not associated with 1-OHPG concentrations, the high concentrations of PAHs in both air and food suggest that they are both important routes of exposure to PAHs in this population. Further evaluation of the role of PAH exposure from air and food in the elevated rates of esophageal cancer in this region is warranted.Journal of Exposure Science and Environmental Epidemiology advance online publication, 18 July 2012; doi:10.1038/jes.2012.73.
    Journal of Exposure Science and Environmental Epidemiology 07/2012; · 3.19 Impact Factor
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    ABSTRACT: The certification of chemical constituents in natural-matrix Standard Reference Materials (SRMs) at the National Institute of Standards and Technology (NIST) can require the use of two or more independent analytical methods. The independence among the methods is generally achieved by taking advantage of differences in extraction, separation, and detection selectivity. This review describes the development of the independent analytical methods approach at NIST, and its implementation in the measurement of organic constituents such as contaminants in environmental materials, nutrients and marker compounds in food and dietary supplement matrices, and health diagnostic and nutritional assessment markers in human serum. The focus of this review is the important and critical role that separation science techniques play in achieving the necessary independence of the analytical steps in the measurement of trace-level organic constituents in natural matrix SRMs.
    Journal of Chromatography A 06/2012; 1261:3-22. · 4.61 Impact Factor
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    ABSTRACT: Determination of the dynamic nature of vapor/odor release has application in a wide variety of systems. This study applies automated solid-phase microextraction (SPME) utilizing an externally sampled internal standard (ESIS) to determine the vapor-time profile of odor delivery devices for three classes of explosive compounds. The profiles of delivery systems for target odorants 2,4-dinitrotoluene (2,4-DNT), 2-ethyl-1-hexanol (2-EH), and triacetone triperoxide (TATP) as canine training aids were compared over a period of 70 h. Strategies for evaluating the vapor-time profile of components with widely differing volatility are considered. An approach to quantifying the vapor concentration is described. The differences in the vapor-time profiles are examined and suggestions for selecting the best representative odor delivery technique are outlined.
    Journal of Chromatography A 05/2012; 1244:28-36. · 4.61 Impact Factor
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    ABSTRACT: Standard reference materials (SRMs) are homogeneous, well-characterized materials used to validate measurements and improve the quality of analytical data. The National Institute of Standards and Technology (NIST) has a wide range of SRMs that have mass fraction values assigned for legacy pollutants. These SRMs can also serve as test materials for method development, method validation, and measurement for contaminants of emerging concern. Because inter-laboratory comparison studies have revealed substantial variability of measurements of perfluoroalkyl acids (PFAAs), future analytical measurements will benefit from determination of consensus values for PFAAs in SRMs to provide a means to demonstrate method-specific performance. To that end, NIST, in collaboration with other groups, has been measuring concentrations of PFAAs in a variety of SRMs. Here we report levels of PFAAs and perfluorooctane sulfonamide (PFOSA) determined in four biological SRMs: fish tissue (SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue), bovine liver (SRM 1577c), and mussel tissue (SRM 2974a). We also report concentrations for three in-house quality-control materials: beluga whale liver, pygmy sperm whale liver, and white-sided dolphin liver. Measurements in SRMs show an array of PFAAs, with perfluorooctane sulfonate (PFOS) being the most frequently detected. Reference and information values are reported for PFAAs measured in these biological SRMs.
    Analytical and Bioanalytical Chemistry 04/2012; · 3.66 Impact Factor
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    ABSTRACT: Polycyclic aromatic sulfur heterocycles (PASH) are ubiquitous in fossil fuels and pose risk to the environment due to their toxicity. Some PASH, resistant to degradation in the environment, are used to differentiate pollutant source and weathering. Although retention data exist for some PASH, few mass spectra are available, so misidentification often occurs between isomers in the same family. In this study, the retention behavior of 119 PASH on 14%-cyanopropyl/86%-polydimethylsiloxane (DB-1701ms), trifluoropropylmethylpolysiloxane (Rtx-200ms), 5%-phenyl/95%-dimethyl (Rxi-5ms), and 50%-diphenyl/50%-dimethyl (Rxi-17Sil-ms) are reported along with their mass spectra. This data is guiding on-going research aimed at identifying PASH in coal tar by multidimensional GC-GC/MS for compounds where standards are not available.
    Polycyclic Aromatic Compounds 01/2012; 32(2):154-176. · 1.04 Impact Factor
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    ABSTRACT: Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM K55.a, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2009/2010. Eleven national measurement institutes and the BIPM participated. Participants were required to assign the mass fraction of estradiol present as the main component in the comparison sample (CCQM-K55.a) which consisted of a bulk estradiol hemihydrate material obtained from a commercial supplier that had been extensively but not exhaustively dried prior to sub-division into the units supplied for the comparison. Estradiol was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of organic compounds of medium structural complexity [molar mass range 300â€モ500 Da] and low polarity ( pK OW < âˆメ2) for which related structure impurities can be quantified by capillary gas phase chromatography (GC) or by high performance liquid chromatography (LC). The majority of participants used a mass balance approach to determine the estradiol content. The key comparison reference value (KCRV) for estradiol in CCQM-K55.a was assigned by combination of KCRVs assigned by consensus from participant results for each orthogonal impurity class. This allowed participants to demonstrate the efficacy (or otherwise) of their implementation of the mass balance approach and to demonstrate that their assigned value for the main component agreed with the KCRV through use of internally consistent contributing methods. The KCRV for the estradiol content of the material was 984.3 mg/g with a combined standard uncertainty of 0.42 mg/g. The individual participant results showed that a relative expanded uncertainty for the purity assignment of 0.2% is a reasonable estimate of the best achievable result by an individual laboratory for a material of this complexity available in this amount at this level of purity. The relative expanded uncertainties reported by laboratories having results consistent with the KCRV ranged from 0.2% to 0.8%. The review of results that were biased from the KCRV showed that two major analytical challenges are posed by the material: the measurement of its water content and controlling for related substance artefact formation during the analysis process. The results displaying a positive bias relative to the KCRV (overestimation of estradiol content) were due to underestimation of the water content of the material, while those with a negative bias (underestimation of estradiol) overestimated the total related substance impurities through a failure to detect and control for artefact formation arising from in situ oxidative dimerization of estradiol in neutral solution prior to analysis. There was however good agreement between all participants in the identification and the quantification of the individual related structure impurities actually present in the sample. The comparison also demonstrated the utility of high-field 1 H NMR for both quantitative and qualitative analysis of high purity compounds. It is noted that all the participants who used qNMR as a major or contributing technique and included it as part of, combined it or confirmed it with a conventional 'mass balance' data estimate, obtained results consistent with the KCRV. Main text. To reach the main text of this paper, click on Final Report [http://www.bipm.org/utils/common/pdf/final_reports/QM/K55/CCQM-K55.a.pdf] . Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/ [http://kcdb.bipm.org/] . The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
    Metrologia 01/2012; 49(1A):08009. · 1.90 Impact Factor
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    ABSTRACT: Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM K55.b, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2010/2011. Nineteen national measurement institutes and the BIPM participated. Participants were required to assign the mass fraction of aldrin present as the main component in the comparison sample for CCQM-K55.b which consisted of technical grade aldrin obtained from the National Measurement Institute Australia that had been subject to serial recrystallization and drying prior to sub-division into the units supplied for the comparison. Aldrin was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of organic compounds of medium structural complexity [molar mass range 300 Da to 500 Da] and low polarity (pKOW < −2) for which related structure impurities can be quantified by capillary gas phase chromatography (GC). The key comparison reference value (KCRV) for the aldrin content of the material was 950.8 mg/g with a combined standard uncertainty of 0.85 mg/g. The KCRV was assigned by combination of KCRVs assigned by consensus from participant results for each orthogonal impurity class. The relative expanded uncertainties reported by laboratories having results consistent with the KCRV ranged from 0.3% to 0.6% using a mass balance approach and 0.5% to 1% using a qNMR method. The major analytical challenge posed by the material proved to be the detection and quantification of a significant amount of oligomeric organic material within the sample and most participants relying on a mass balance approach displayed a positive bias relative to the KCRV (overestimation of aldrin content) in excess of 10 mg/g due to not having adequate procedures in place to detect and quantify the non-volatile content—specifically the non-volatile organics content—of the comparison sample. There was in general excellent agreement between participants in the identification and the quantification of the total and individual related structure impurities, water content and the residual solvent content of the sample. The comparison demonstrated the utility of 1H NMR as an independent method for quantitative analysis of high purity compounds. In discussion of the participant results it was noted that while several had access to qNMR estimates for the aldrin content that were inconsistent with their mass balance determination they decided to accept the mass balance result and assumed a hidden bias in their NMR data. By contrast, laboratories that placed greater confidence in their qNMR result were able to resolve the discrepancy through additional studies that provided evidence of the presence of non-volatile organic impurity at the requisite level to bring their mass balance and qNMR estimates into agreement. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
    Metrologia 01/2012; 49(1A):08014. · 1.90 Impact Factor
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    ABSTRACT: The vapor-time profiles of explosive materials are of valuable interest to Homeland Security, providing critical information that can aid in the detection of explosive-containing devices. An approach is described that achieves reproducible characterization of volatile components as a function of time based on comparison of the sample response to an externally sampled internal standard (ESIS). Utilizing nonequilibrium solid-phase microextraction (SPME) measurements, this SPME-ESIS technique improves reproducibility (reported as percent relative standard deviation) of vapor-time profiles by approximately an order of magnitude and allows for an equitable comparison of the target compound between diverse materials. Two odorants associated with canine detection of explosives, 2-ethyl-1-hexanol and 2,4-dinitrotoluene, are used to optimize parameters for the SPME-ESIS technique.
    Analytical Chemistry 10/2011; 83(22):8560-5. · 5.70 Impact Factor
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    ABSTRACT: Despite numerous instrumental achievements, canines are still considered the most effective field method for explosive detection. However, due to strict explosive regulations and safety requirements, it can be a challenge for agencies with "bomb dogs" to train using neat explosive materials. This establishes a need for non-explosive canine training aids with the same volatile component profiles as the explosives that they represent. In order to compare mimic materials to their explosive counterparts, a technique must be established that not only allows for identification of volatile compounds but also can monitor changes in the headspace profile over time with respect to time and temperature. The Automated Training Aid Simulation using SPME (or ATASS) was developed for that purpose. As described, ATASS was used to observe changes in the volatile profile of three explosives (Composition C-4, 2,4-dinitrotoluene (DNT), and triacetone triperoxide (TATP)) and respective prototype training materials (0.1% by mass C-4, 1% by mass 2,4-DNT, and 1% by mass TATP). Samples were prepared in vials and metal tins within a gallon (≈ 3785 mL) paint can to simulate common field techniques for canine training. Monitoring these materials in real time provides a better understanding of the major volatile components present and how the relative abundances of these components can change over time. The results presented indicate that ATASS successfully allows for a sufficient comparison between explosive and non-explosive training materials.
    Forensic science international 06/2011; 212(1-3):90-5. · 2.10 Impact Factor
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    ABSTRACT: PILOT STUDY Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a laboratory comparison, CCQM-P20.f, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2007/2008. Nine national measurement institutes, four expert laboratories and the BIPM participated in the comparison. Participants were required to assign the mass fraction of digoxin present as the main component in the comparison sample (CCQM-P20.f) which consisted of digoxin material obtained from a commercial supplier stated to comply with USP requirements. In addition to assigning the mass fraction content of digoxin for the material, participants were requested, but not obliged, to provide mass fraction estimates for the minor components they identified in each sample. In contrast with the previous round of the CCQM-P20 series, in which the mass fraction content of theophylline in two comparison samples (CCQM-P20.e.1 and CCQM-P20.e.2) was determined, a wider range of results were reported for the mass fraction content of digoxin in the CCQM-P20.f comparison. A minority of participants did not appear to use conditions capable of fully resolving and/or quantifying the major related structure impurities present in the comparison sample. Among those that did achieve suitable separations, there was further variation in their reported quantifications of the individual and total related substance content which reflected in part the limited availability of reference standards for these materials and the resulting assumptions that had to be made regarding the structure and response factors relative to digoxin for each individual impurity. This was particularly relevant because of the span of molecular masses of the impurities present in the sample, which ranged from aglycones to glycones with tetrameric carbohydrate chains, relative to that of digoxin. A significant additional factor also contributed to the observed variation of results. Unlike the CCQM-P20.e samples, in which the major impurities were solely related structure organic compounds, the CCQM-P20.f study material contained significant levels of residual organic solvents (ethanol, dichloromethane and to a lesser extent toluene). The majority of participants failed to detect and allow for the presence of this class of impurity, introducing a bias towards overestimation of digoxin content in most of the individual results. However, the uncertainty budgets produced by several participants were sufficiently conservative such that their reported results were nevertheless consistent with the reference value for digoxin content assigned using a consensus mass balance approach. The results of the comparison reinforce the conclusion from previous rounds of the CCQM-P20 study that care in developing and validating the suitability of the chromatographic separation method used to resolve the main component from the related structure impurities present is essential to obtaining reliable, comparable results when using the mass balance approach to estimate purity. This specific comparison has demonstrated that, in addition to developing an appropriate chromatographic separation, it is also important to use complementary techniques capable of detecting all potential orthogonal classes of impurities if it is desired to demonstrate a general capability to assign purity with a small (<0.2% relative) standard uncertainty.
    Metrologia 01/2011; 48. · 1.90 Impact Factor

Publication Stats

2k Citations
287.13 Total Impact Points

Institutions

  • 1989–2013
    • National Institute of Standards and Technology
      • Analytical Chemistry Division
      Gaithersburg, MD, United States
  • 2001
    • Summit Environmental Technologies
      Cuyahoga Falls, Ohio, United States
  • 1994
    • National Oceanic and Atmospheric Administration
      United States
  • 1993
    • Universität Ulm
      Ulm, Baden-Württemberg, Germany