In This Issue...
Prototype NIST Method Detects and Measures Elusive Hazards
A chemist at the National Institute of Standards and Technology (NIST) has demonstrated a relatively simple, inexpensive method for detecting and measuring elusive hazards such as concealed explosives and toxins, invisible spoilage in food or pesticides distributed in soil by wind and rain. The prototype method is more sensitive than conventional techniques for detecting traces of these materials, which are polar—like water molecules, having distinct electrically positive and negative ends—and do not readily evaporate.
As described in a new paper,* NIST researcher Tom Bruno enhanced a technique called “headspace analysis,” which is the detection and analysis of trace levels of chemical compounds from a solid or liquid that are released into the surrounding atmosphere. Bruno’s enhancements greatly improve the efficiency of sample collection, for the first time making the technique suitable for detecting low concentrations of polar, low-volatility, compounds such as explosives. Preliminary results indicate the method is sensitive enough to measure amounts of target materials that constitute as little as 0.0000002 percent of a sample.
The sample collection device consists of several coils of fine tubing just 0.32 millimeters in inner diameter. Bruno modified the inner coating, which efficiently attracts and retains chemicals across its large surface area. The device can be used with a sample-heating oven as part of a laboratory analysis system or taken into the field for sample collection. To extract target molecules from a sample, the coil is placed inside an insulated cylinder and chilled with a cold air stream to minus 40 degrees Celsius. A gas, such as helium, is swept across the sample held in the oven or the coil device, gathering up target molecules along the way, and through the fine tubing. Chilling the coils—part of Bruno’s innovation—makes collection of target molecules more efficient. The tubing is washed with a solvent, or heated, to release the captured molecules for analysis.
Bruno found that the mass of the collected molecules increases with rising oven and sweep gas temperatures, offering a way to detect specific target molecules under particular field conditions. NIST researchers demonstrated the new method using several explosives, including the pure explosive TNT and the plastic explosive mixture C-4. Among other applications, NIST researchers have used the method to improve sampling and analysis of fire retardants in a car interior, a topic of interest because of concerns expressed by some that the “new car smell” may be a health hazard. They also are using the method to detect volatile protein decomposition products in spoiled meats. Environmental applications could include detection of pesticides deposited on soils subject to weathering effects.
The work is supported by the Department of Homeland Security.
* T.J. Bruno. Simple, quantitative headspace analysis by cryoadsorption on a short alumina PLOT column. 2009. Journal of Chromatographic Science, Vol. 47, pp. 569-574, August.
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High in Sodium: Highly Charged Tungsten Ions May Diagnose Fusion Energy Reactors
Just as health-food manufacturers work on developing the best possible sodium substitutes for low-salt diets, physicists at the National Institute of Standards and Technology (NIST) have acquired new knowledge on a promising sodium alternative of their own. Sodium-like tungsten ions could pepper—and conveniently monitor—the hot plasma soup inside fusion energy devices, potential sources of abundant, clean power.
Tungsten—having the highest melting point of any metal—will be used in some high-strength structural components in the experimental ITER fusion reactor under construction in France (see “NIST Light Source Illuminates Fusion Power Diagnostics,” NIST Tech Beat, Oct. 11, 2007.). When ITER cooks up its hot, dense fusion plasma, it could erode trace amounts of tungsten from its structures and strip away many of its electrons in the process. When 63 of tungsten’s 74 electrons are removed, it becomes chemically analogous to sodium atoms, which have 11 electrons as well.
Ordinary sodium gas radiates bright yellow-orange light, which has proven useful for everything from mundane streetlamps to exotic atom lasers. Sodium radiates approximately 99 percent of its visible light in two shades of orange, which scientists have termed the “D” spectral lines.
Sodium-like tungsten ions emit intense light in analogous “D” spectral lines, but they are at far higher energy levels than sodium, and so are shifted out of the visible spectrum to the extreme ultraviolet. Measuring the wavelengths and relative intensities of lines in the spectrum of light released by a population of tungsten ions in the plasma can provide information about the fusion plasma conditions, such as its temperature, density and magnetic fields. Yet it has been challenging to measure light in this portion of the electromagnetic spectrum.
NIST’s John Gillaspy and his colleagues have now provided the first measurement* of both “D” lines in sodium-like tungsten, confirming theoretical predictions of their energies and intensities. The NIST scientists further checked their knowledge by measuring the spectrum of light from other sodium-like ions of hafnium, tantalum and gold. The researchers used NIST’s electron beam ion trap (EBIT), which employs an electron beam to make, catch and study highly charged ions. To measure the spectra, they used an extreme ultraviolet (EUV) spectrometer, originally developed to study 13.5 nanometer wavelength light emitted from plasma sources for next-generation microelectronics applications, but they discovered they could push it to detect radiation as low as about 2 nanometers, where tungsten’s lower-wavelength “D” line resides. With this experimental knowledge of tungsten’s lines, researchers may now have a robust new ingredient for measuring fusion reactor conditions.
* J.D. Gillaspy, I.N. Draganic, Y. Ralchenko, J. Reader, J.N. Tan, J.M. Pomeroy and S.M. Brewer Measurement of the D-line doublet in high-Z highly charged sodiumlike ions. Physical Review A, Published online 8 July 2009. doi/10.1103/PhysRevA.80.010501.
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NIST Calculations May Improve Temperature Measures for Microfluidics
If you wanted to know if your child had a fever or be certain that the roast in the oven was thoroughly cooked, you would, of course, use a thermometer that you trusted to give accurate readings at any temperature within its range. However, it isn’t that simple for researchers who need to measure temperatures in microfluidic systems—tiny, channel-lined devices used in medical diagnostics, DNA forensics and “lab-on-a-chip” chemical analyzers—as their current “thermometer” can only be precisely calibrated for one reference temperature. Now, researchers at the National Institute of Standards and Technology (NIST) have proposed a mathematical solution that enables researchers to calibrate the “thermometer” for microfluidic systems so that all temperatures are covered.
Reactions taking place in microfluidic systems often require heating, meaning that users must accurately monitor temperature changes in fluid volumes ranging from a few microliters (a droplet approximately 1 millimeter in diameter) to sub-nanoliters (a droplet approximately 1/10 of millimeter in diameter). A common DNA analysis technique, for example, depends heavily on precise temperature cycling. Ordinary thermometers or other temperature probes are useless at such tiny dimensions, so some groups have turned to temperature-sensitive fluorescent dyes, particularly rhodamine B. The intensity of the dye’s fluorescence decreases with increasing temperature. The idea is that the dye can be used as a noninvasive way to map the range of temperatures occurring within a microfluidic system during heating and, in turn, provide a means of calibrating that system for experiments.
However, the technique currently requires the user to base all readings on the fluorescence at a single reference temperature. Previous groups have developed “calibration curves” that relate temperature to rhodmaine B fluorescent intensity based on a reference temperature of about 23 degrees Celsius (a technique first proposed by NIST researchers David Ross, Michael Gaitan and Laurie Locascio in 2001*). But it turns out that the curves are only good for that one temperature. In an upcoming paper in Analytical Chemistry**, the NIST team—Jayna J. Shah, Michael Gaitan and Jon Geist—reports that changing the reference point, such as the higher temperature when a microfluidic system is first heated, introduces errors when a dye intensity-to-temperature calculation is done using current methods.
“Our analysis shows that a simple linear correction for a 40 degrees Celsius reference temperature identified errors between minus 3 to 8 degrees Celsius for three previously published sets of calibration equations derived at approximately 23 degrees Celsius,” says lead researcher Shah.
To address the problem, the NIST team developed mathematical methods to correct for the shift experienced when the reference temperature changes. This allowed the researchers to create generalized calibration equations that can be applied to any reference temperature.
Microfluidic DNA amplification (production of numerous copies of DNA from a tiny sample) by the polymerase chain reaction (PCR) is one procedure that could benefit from the new NIST calculations, Shah says. “PCR requires a microfluidic device to be cycled through temperatures at three different zones starting around 65 degrees Celsius, so a useful dye intensity-to-temperature ratio would have to be based on that temperature and not a reference point of 23 degrees Celsius,” she explains.
* D. Ross, M. Gaitan and L.E. Locascio. Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye. Analytical Chemistry, Vol. 73, No. 17, pages 4117-4123, Sept. 1, 2001.
** J.J. Shah, M. Gaitan and J. Geist. Generalized temperature measurement equations for rhodamine B dye solution and its application to microfluidics. Analytical Chemistry, Vol. 81, No. 19, Oct. 1, 2009 (published online Sept. 1, 2009).
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New NIST Trace Explosives Standard Slated for Homeland Security Duty
Security personnel need to be able to find explosive materials and persons who have been in contact with them. To aid such searches, the National Institute of Standards and Technology (NIST), with support from the Department of Homeland Security, has developed a new certified reference material, Standard Reference Material (SRM) 2905, Trace Particulate Explosives. Compatible with field and laboratory assay methods, the SRM will be helpful in calibrating, testing and developing standard best operating procedures for trace-explosives detectors.
Most air travelers have probably had some experience with prototype walkthrough portal or tabletop-type trace explosive detectors. Customs inspectors use the machines to check international cargo shipments, and firefighters and police officers use them to evaluate suspicious packages.
The goal of these detectors is to effectively collect residue particles that result from handling materials that might be used to fabricate a bomb and then evaluate the explosives content. For example, when operating the tabletop device, security personnel use a piece of material to swab packages and bags for explosive residues. The security officer then places the swab in a tabletop device that heats the material, separating any chemical residues that may have been absorbed.
Like other sensitive instruments, these machines need well-defined calibration standards to ensure that they are working properly. According to NIST chemist William MacCrehan, the calibration materials that the vendors of these machines provide are typically of unknown quality.
“These detectors need to be reliable and precise enough to detect particles that weigh as little as a few billionths of a gram,” says MacCrehan. “We created this SRM to provide manufacturers and operators with high quality, independently generated and validated reference test materials to enable better designs and reduce the number of false positives and negatives.”
SRM 2905 consists of four different test substances designed to simulate trace residues of C-4 plastic explosives and TNT. The substances themselves consist of inert solid particles about 20 to 30 microns in diameter. The particles have been coated with explosive materials and a florescent tag, which enables the material to be seen using specially filtered optics or glasses. Although the particles are coated with explosive material, MacCrehan says they are incapable of exploding on their own and are completely safe to handle.
This release is part of a larger, ongoing project to develop other wet and dry materials that simulate SEMTEX, gunpowder and peroxide-type explosives. According to MacCrehan, efforts also are underway to develop reference materials to help train bomb-sniffing dogs.
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NIST Issues New Call for White Papers on Critical National Needs
The National Institute of Standards and Technology (NIST) has published a new request for "white papers" that outline or help define potential new funding competitions under the agency’s Technology Innovation Program (TIP). A notice* in the Sept. 4, 2009 issue of the Federal Register solicits detailed analyses of critical national and societal needs that could be addressed by new technology developed with TIP support.
TIP promotes innovation in the United States through cost-shared funding for high-risk, high-reward research projects by single small-sized or medium-sized businesses or by joint ventures that also may include institutions of higher education, nonprofit research organizations and national laboratories. Competitions for TIP funding target large national and societal needs that arguably could be addressed or reduced through a program of high-risk, transformational research. Suggestions in the form of white papers from interested parties, including industry; academia; federal, state, and local governments; and professional organizations and societies are among the several sources consulted by TIP in deciding the scope of future competitions.
While TIP is interested in white papers addressing any area of critical national need, the program is particularly soliciting information related to several potential topic areas currently under consideration. These include:
The full text of the Federal Register notice is available at www.nist.gov/tip/2009_tip_frn_cnn_white_paper_8_13_09.pdf
* Federal Register, Vol. 74, No. 171, Friday, Sept. 4, 2009, p. 45823.
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New NIST Publications Describe Standards for Identity Credentials and Authentication Systems
Two publications from the National Institute of Standards and Technology (NIST) describe new capabilities for authentication systems using smart cards or other personal security devices within and outside federal government applications. A report describes a NIST-led international standard, ISO/IEC 24727, which defines a general-purpose identity application programming interface (API). The other is a draft publication on refinements to the Personal Identity Verification (PIV) specification.
NIST is responsible for developing specifications for PIV cards required for the government under Homeland Security Presidential Directive 12. These smart cards have embedded chips that hold information and biometric data such as specific types of patterns in fingerprints called “minutiae” along with a unique identifying number. The goal is to develop methods that allow each worker to have a PIV card that works with PIV equipment at all government agencies and with all card-reader equipment regardless of the manufacturer.
Because there is growing interest in using secure identity credentials like PIV cards for multiple applications beyond the federal workplace, NIST provided its smart card research expertise in the development of an international standard—ISO/IEC 24727 – Identification cards – Integrated circuit card programming interfaces—that provides a set of authentication protocols and services common to identity management frameworks.
The new NIST report, Use of ISO/IEC 24727 is an introduction to that standard. It describes the standard’s general-purpose identity application programming interface, the “Service Access Layer Interface for Identity (SALII)”, which allows cards and readers to communicate and operate with applications seamlessly. The report also describes a proof-of-concept experiment demonstrating that existing PIV cards and readers can work interoperably with ISO/IEC 24727. The applications tested included logging on to Windows or Linux systems, signing and encrypting email, and performing Web authentications.
NIST researchers also are involved in improving PIV components and providing guidelines that the private sector and municipalities can use with a similar smart ID card. They have drafted an update to an earlier publication that contains the technical specifications for interfacing with the PIV card to retrieve and use identity credentials.
Special Publication 800-73-3, Interfaces for Personal Identity Verification, provides specifications for PIV-Interoperable and PIV-Compatible cards issued by non-federal issuers, which may be used with the federal PIV system. It also provides specifications designed to ease implementation, facilitate interoperability and ensure performance of PIV applications in the federal workplace. The new publication specifies a PIV data model, card edge interface and application programming interface. The report also provides editorial changes to clarify information in the earlier version. (For background, see “Updated Specification Issued for PIV Card Implementations,” NIST Tech Beat, Oct. 14, 2008.)
The draft version of NIST SP 800-73-3 is open for public comment through Sept. 13, 2009. The document is available online at http://csrc.nist.gov/publications/PubsDrafts.html#800-73-3. Comments should be addressed to PIV_comments@nist.gov with “Comments on Public Draft SP 800-73-3” in the subject line.
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Seventeen Years of Baldrige Scoring Data Now Available
The Baldrige National Quality Program recently published “blinded” (anonymous) scoring data on 1,033 applicants for the Baldrige National Quality Award during the years 1990-2006. The data, posted at www.baldrige.nist.gov/Data_Analysis/index.htm, are being publicly released in response to many requests and to facilitate further analysis by interested researchers.
Presented in both tabular and graphic forms, the scoring data come from both independent reviews (the initial scores given by individual examiners prior to consensus by the full examiner team) and consensus reviews (the later scores determined by the full team) for: (1) all 17 years and all six award categories (manufacturing, small business, service, health care, education and nonprofit) together; (2) all 17 years by individual category; (3) the comparison of categories within individual years; and (4) the comparison of years within individual categories. Applicants and examiners are not identified.
Future updates to the scoring data Web site will add features such as individual applicant scores for individual Baldrige criteria and the ability to track the scoring progress for repeat applicants.
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