Papers by George Rhoderick
<title>Methane-in-air standards measured using a 1.65μm frequency-stabilized cavity ring-down spectrometer</title>
Chemical and Biological Sensors for Industrial and Environmental Monitoring II, 2006
Frequency-stabilized cavity ring-down absorption spectrometry (FS-CRDS) with single-mode excitati... more Frequency-stabilized cavity ring-down absorption spectrometry (FS-CRDS) with single-mode excitation using a tunable continuous-wave diode laser is being developed to help support the delivery of reference gas concentration standards. This paper describes initial efforts to compare FS-CRDS measurements with National Institute of Standards and Technology (NIST) methane-in-air standard reference materials to demonstrate the potential of this method to deliver standards-grade measurements
Creation of 0.10-cm-1 resolution quantitative infrared spectral libraries for gas samples
Proceedings of SPIE - The International Society for Optical Engineering
The National Institute of Standards and Technology (NIST) and the Pacific Northwest National Labo... more The National Institute of Standards and Technology (NIST) and the Pacific Northwest National Laboratory (PNNL) are independently creating quantitative, approximately 0.10 cm-1 resolution, infrared spectral libraries of vapor phase compounds. The NIST library will consist of approximately 100 vapor phase spectra of volatile hazardous air pollutants (HAPs) and suspected greenhouse gases. The PNNL library will consist of approximately 400 vapor
Infrared Absorptivity temperature dependence of gas phase methanol and sulfur dioxide
Standard reference database 79, quantitative infrared database
Journal of research of the National Institute of Standards and Technology
Quality assurance of reference spectral data
Journal of the Air & Waste Management Association
The NIST quantitative infrared database
With the recent developments in Fourier transform infrared (FTIR) spectrometers it is becoming mo... more With the recent developments in Fourier transform infrared (FTIR) spectrometers it is becoming more feasible to place these instruments in field environments. As a result, there has been enormous increase in the use of FTIR techniques for a variety of qualitative and quantitative chemical measurements. These methods offer the possibility of fully automated real-time quantitation of many analytes; therefore FTIR
Gas Standards Based on Optical Spectroscopies
Metrologia
CCQM Key Comparison K4 involved primary standards of ethanol in air at a nominal amount fraction ... more CCQM Key Comparison K4 involved primary standards of ethanol in air at a nominal amount fraction 120 µmol/mol. The method used by the pilot laboratory to prepare these standards and the results from the eight participating laboratories are reported.
Fresenius' Journal of Analytical Chemistry, 1998
e.g., alga reference material IAEA-140, in which the contents of interfering elements Na, Cl, Al ... more e.g., alga reference material IAEA-140, in which the contents of interfering elements Na, Cl, Al and Mn are high, the detection limit of NAA for Cu is reduced. In this case, ICP-MS is more suitable than NAA.
REVISION 2-14-96ABSTRACT
A program is described by which the concentration of commercially produced gas mixtures may be
Analysis of One Compressed Gas Mixture for CCQM-K46, Ammonia in Nitrogen
Metrologia
The NIST Atmospheric Methane Gas Standard Scale
The National Institute of Standards and Technology (NIST) has entered into a collaboration with t... more The National Institute of Standards and Technology (NIST) has entered into a collaboration with the National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado on dveloping SI-traceable standards for greenhouse gas monitoring. The Earth System Research Laboratory (ESRL) of NOAA has been designated by the World Meteorological Organization to provide SI-traceable gases to laboratories participating in the WMO climate science community Global Atmosphere Watch program. NOAA has agreed to demonstrate comparability to other National Metrology Institutes under international an existing international agreement (BIPM MRA). NIST and NOAA have begun a series of bilateral comparisons to demonstrate comparability. The Gas Metrology Group at NIST has developed a new suite of atmospheric methane Primary Standard Gas Mixtures (PSMs) that range in amount-of-substance fraction (dry-air mole fraction) from 1700 to 2050 nmol/mol (ppb) with ± 0.03% (0.6 nmol/mol) relative uncertainties (...
Environmental and Industrial Sensing
Composite films containing enzyme and indicator molecules were produced by means of polyelectroly... more Composite films containing enzyme and indicator molecules were produced by means of polyelectrolyte self-assembly. These membranes provide two functions: (i) molecular recognition of the substratum by respective enzyme, and (ii) optrode transducing, when the products o the substratum decomposition affect optical spectra of indicator molecules. Apart from direct registration of enzyme reactions, inhibition reactions can also be monitored with this method. Particularly, heavy metal salts and phosphor organic pesticides acting as inhibitors for Urease and Cholinesterase, respectively, were registered. Composite PESA films were deposited onto glass slides and consisted of several layers of poly(alylamine) hydrochloride (PAA) alternated with indicator molecules, either Cyclo-tetra- chromotropylene or Thymol Blue, both containing SO3- Na+ groups. Then a few layers of PAA/enzyme were deposited on top. A typical structure of the samples was (PAA/Indicator)n/(PAA/Enzyme)m/PAA with n equals 1...
Analytical chemistry, Jan 3, 2015
Between June 2010 and June 2011, the National Institute of Standards and Technology (NIST) gravim... more Between June 2010 and June 2011, the National Institute of Standards and Technology (NIST) gravimetrically prepared a suite of 20 carbon dioxide (CO2) in air primary standard mixtures (PSMs). Ambient mole fraction levels were obtained through six levels of dilution beginning with pure (99.999%) CO2. The sixth level covered the ambient range from 355 to 404 μmol/mol. This level will be used to certify cylinder mixtures of compressed dry whole air from both the northern and southern hemispheres as NIST standard reference materials (SRMs). The first five levels of PSMs were verified against existing PSMs in a balance of air or nitrogen with excellent agreement observed (the average percent difference between the calculated and analyzed values was 0.002%). After the preparation of a new suite of PSMs at ambient level, they were compared to an existing suite of PSMs. It was observed that the analyzed concentration of the new PSMs was less than the calculated gravimetric concentration by ...
The NIST Traceable Reference Material Program for Gas Standards
ABSTRACT A program is described by which the concentration of commercially produced gas mixtures ... more ABSTRACT A program is described by which the concentration of commercially produced gas mixtures may be related to gaseous primary standards maintained by the National Institute of Standards and Technology (NIST). The gaseous mixtures, referred to as gas ...
Analytical chemistry, Jan 25, 2015
There is evidence that the use of whole air versus synthetic air can bias measurement results whe... more There is evidence that the use of whole air versus synthetic air can bias measurement results when analyzing atmospheric samples for methane (CH4) and carbon dioxide (CO2). Gas chromatography with flame ionization detection (GC-FID) and wavelength scanned-cavity ring down spectroscopy (WS-CRDS) were used to compare CH4 standards produced with whole air or synthetic air as the matrix over the mole fraction range of 1600-2100 nmol mol(-1). GC-FID measurements were performed by including ratios to a stable control cylinder, obtaining a typical relative standard measurement uncertainty of 0.025%. CRDS measurements were performed using the same protocol and also with no interruption for a limited time period without use of a control cylinder, obtaining relative standard uncertainties of 0.031% and 0.015%, respectively. This measurement procedure was subsequently used for an international comparison, in which three pairs of whole air standards were compared with five pairs of synthetic ai...
Fresenius' Journal of Analytical Chemistry, 2001
An EPA Voluntary Aluminum Industrial Partnership (VAIP) program has been formed to help US primar... more An EPA Voluntary Aluminum Industrial Partnership (VAIP) program has been formed to help US primary producers focus on reducing the emissions of two perfluorocarbons (PFCs), tetrafluoromethane (CF 4 ) and hexafluoroethane (C 2 F 6 ), during the production of aluminum. To ensure comparability of measurements over space and time, traceability to national sources was desirable. Hence, the EPA approached the NIST to develop a suite of primary standards to cover a mole fraction (concentration) range of 0.1 to 1400 µmol mol -1 for CF 4 and 0.01 to 150 µmol mol -1 of C 2 F 6 . A total of eight gravimetric PFC gas standards were prepared with relative expanded uncertainties of ≤ 0.52% (≈95% confidence level). These primary standards were ultimately used to assign values to a series of secondary gas standards at three mole-fraction levels with relative expanded uncertainties ranging from ± 0.7% to 5.3% (≈95% confidence level). This series of secondary standards was used within the aluminum industry to calibrate instruments used to make emission measurements. Assignment of values to the secondary standards was performed by use of gas chromatography with flame-ionization detection (GC-FID) and Fourier transform infrared spectrometry (FTIR). Real time pot-line and stack samples from a local aluminum plant were also obtained and sub-samples sent to each participating facility for analysis. The data generated from each facility were sent to NIST for analysis. The maximum difference between the NIST and individual facilities' values for the same sub-sample was ± 26%.
<title>Sample and data processing considerations for the NIST quantitative infrared database</title>
Environmental Monitoring and Remediation Technologies, 1999
ABSTRACT
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Papers by George Rhoderick