Concentration (µg g-1) of PCBs (·) (S 29 congeners) and biphenyl (o) in electron beam irradiated samples of SRM 1944, New York/New Jersey Waterway Sediment, as a function of irradiation dose (kGy).

The transformation of polychlorinated biphenyls (PCBs) in environmental media into compounds with a lower degree or absence of chlorine content has been achieved. CSTL scientists, in collaboration with researchers from the University of Maryland, College Park, have demonstrated effective radiation-induced degradation of PCBs in water systems, transformer oils, and marine sediments using electron beam technology. This technology, which makes use of an electron beam from a linear accelerator, has the potential to be the preferred treatment for the cleanup of PCBs in environmental media when compared to currently used methods such as incineration or organic solvent washing. Gaseous and particulate waste effluents that result from incineration are minimized and the process does not produce solvent waste streams that must be treated or disposed of properly. In addition, radiation processes are inherently selective to the target chlorinated compounds, leading to either total dechlorination or to products with reduced chlorine content that are more susceptible to bioremediation.

To investigate the application of an electron beam to the dechlorination of PCBs in marine sediment, samples of Standard Reference Material (SRM) 1944, New York/New Jersey Waterway Sediment, were mixed with aqueous alcohol solutions and irradiated. Isopropanol was added to enhance radiolytic yields of reductants and, thus, dechlorination of contaminants. In the electron beam irradiated samples, the concentrations of 29 PCB congeners were found to decrease as a function of dose. At the highest dose (500 kGy) the total concentration of PCBs was decreased by 83 percent. This research has demonstrated the feasibility of this approach and has provided initial design parameters for possible scale-up. Further experiments are underway to examine the use of other additives, particularly those that are more environmentally benign (such as ascorbate) that will also enhance the dechlorination process.

An alternative treatment of PCBs in environmental media may be the use of ultraviolet (UV) radiation. PCBs in transformer oils have been fully degraded using radiation generated by a UV lamp. The application of this method to marine sediment slurries led to little dechlorination in the presence of isopropanol, but with added triethylamine dechlorination was achieved (about 60 percent). It is likely that photolysis under optimal conditions (other additives, additional exposure time) may prove as effective as electron beam treatment for the dechlorination of PCBs in sediment. Moreover, the photochemical efficiency can be increased by an order of magnitude or more by using a quartz window or a windowless configuration, using a better UV source, and improving the irradiation geometry. These parameters and the use of environmentally friendly additives are under study.

June 2003

With the assistance of the American Association of Clinical Chemistry (AACC), the International Federation of Clinical Chemistry (IFCC), and the manufacturers of clinical cTnI assays, NIST is developing a cTnI reference material to address the need for assay standardization. Through two interlaboratory comparison studies, various troponin preparations, including recombinant and native troponin complexes of the troponin T, troponin I, and troponin C subunits, recombinant troponin IC complex, and recombinant and native cTnI, were evaluated using fifteen commercial cTnI assays. Based on the results of these interlaboratory comparison studies, NIST Standard Reference Material (SRM) 2921 will be a purified human cardiac troponin complex of the troponin T, troponin I, and troponin C subunits. The native troponin complex standardized clinical assays better than the other troponin preparations evaluated. Additionally, the native troponin complex was found to be commutable when compared to pooled patient samples for all fifteen assays included in the study. The troponin complex, purified from healthy human hearts under non-denaturing conditions, is produced for NIST by HyTest, Ltd. in Turku, Finland.

NIST SRM 2921 will be supplied as a frozen aqueous solution of the troponin complex. Characterization of the structures of the troponin subunits will be performed by mass spectrometry and a certified value for the concentration of the troponin I subunit will be determined by a variety of analytical techniques, including amino acid analysis. Manufacturers of commercial cTnI assays will be able to use SRM 2921 for quality control purposes and to establish direct SI-traceability of assay measurements, as well as for the value assignment of secondary reference materials.

SRM 2921 is expected to be available in the fall of 2003.

June 2003

Traditional methods of screening job applicants, athletes and others for illicit drug use increasingly are being supplanted or complemented by hair analysis, which offers several testing advantages. The accuracy of such hair tests now can be quality assured through the use of two new Standard Reference Materials (SRMs) from the National Institute of Standards and Technology (NIST).The new NIST standards, which consist of human hair segments that have been soaked in solutions containing target drugs, help validate the accuracy of test methods for detecting those drugs. The first, SRM 2379, is designed for tests of stimulants (“uppers”) such as cocaine and PCP. Its companion SRM, number 2380, checks tests for depressants (“downers”), such as codeine and THC (the active ingredient in marijuana).As new hair tissue forms in the roots, drugs and other chemicals from the bloodstream may be absorbed into and retained by the growing follicles. Hair’s advantages in drug testing—when compared to using fluids such as urine—are that it can be collected more easily, is more difficult to switch or contaminate, and retains traces of drugs for at least 90 days (not just two or three). However, hair analysis generally is not applicable to the detection of drug use initiated within the past 10 days. Therefore, it may be favored as a complement to, rather than a substitute for, traditional methods.NIST began researching the analysis of drugs in hair in 1990 and has conducted seven interlaboratory comparison exercises to see how well different methods work, and in some cases, how well different laboratories conduct such tests.

May 2003

The capability to identify chemical substances easily and accurately at a crime scene or other location outside a laboratory, without handling the material or opening containers, would be a boon for many in science. A new NIST standard that reduces calibration costs as much as 20-fold represents a major step toward making such a tool practical. A small piece of chromium-doped glass, Standard Reference Material (SRM) 2241, will enable users to calibrate the output of Raman spectrometers. Without this SRM, full calibration of these instruments is so expensive that many users skip it and, therefore, may get inaccurate results. Raman spectroscopy reveals the chemical composition of a sample by illuminating it with a laser and then identifying color changes in a very small amount of the scattered light. The technique is simple enough to use in the field and, unlike some competing methods, can be used to measure samples through transparent containers.

May 2003

This SRM has been developed for evaluating analytical methods for determining polychlorinated biphenyl (PCB) congeners, chlorinated pesticides, fatty acids, extractable fat, methylmercury, total mercury, and selected trace elements in fish tissue and similar matrices. Of particular interest are persistent environmental and tissue contaminants such as PCBs and chlorinated pesticides, some of which are suspected carcinogens or have been banned for other reasons; and mercury and methylmercury, which are highly toxic, the latter to nerve tissue. SRM 1946 is the first to provide certified values for three non-ortho-substituted PCBs that are considered the most toxic because of their structural resemblance to 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD).
In addition, this SRM is intended for analysis of food proximates (fat, protein, and carbohydrates) and other constituents of interest in food analysis. For example, fish containing more than a level of methylmercury established by regulation is not to be consumed.Certified values are provided for 30 PCB congeners and 15 chlorinated pesticides, respectively. These values were obtained via two or more independent analytical techniques, based principally on chromatographic and mass spectrometric methods.
Certified values also are given for total extractable fat and 13 individual fatty acids; these are based on measurements made by NIST and collaborating laboratories. Certified values for methylmercury, total mercury, arsenic, and iron are based on results of two or more independent analytical procedures, performed at NIST and collaborating laboratories.
SRM 1946 also provides reference concentration values for 12 PCB congeners, 2 chlorinated pesticides, 12 fatty acids, certain proximates and elements, and caloric content. Certified, reference, and information values are listed in the NIST Certificate of Analysis for Standard Reference Material® 1946, issued 7 October 2002.
One unit of SRM 1946 consists of five bottles, each of which contains approximately 10 g to 12 g (wet basis) of frozen (not freeze-dried) tissue homogenate. This SRM is currently in preparation.

May 2003

The Nutrition Labeling and Education Act of 1990 requires that information for selected nutrients is provided on labels for processed foods. In response, NIST has been working to provide food-matrix SRMs with values assigned for the required nutrients. SRM 2387 Peanut Butter is the most recent SRM in this series. SRM 2387 is intended for use as a primary control material for assigning values to in-house control materials and to validate methods for measuring nutrients such as fat, protein, calcium, iron, calories, and vitamins. This is the first food-matrix reference material available from NIST for which values are also assigned for individual amino acids and for aflatoxins.
To study the robustness of analytical methods, AOAC International developed a nine-sector triangle in which foods are positioned based on their fat, protein, and carbohydrate content. The idea was that one or two foods within each sector should be representative of other foods within that sector when validating an analytical method. Similarly, one or two food-matrix reference materials in each sector can be used as control materials for other foods within that sector. With the release of SRM 2387, one or more reference materials in each of the nine sectors are available from NIST. This SRM is currently in preparation.

May 2003

See a recent article on SRM 2387 and the completed food triangle at The New York Times.

Standard Reference Material (SRM) 3072 is a solution of diquat dibromide monohydrate (Chemical Abstracts Registry Number 85-00-07) in water intended primarily for use in the calibration of chromatographic instrumentation used for the determination of diquat dibromide monohydrate. This SRM can also be used to fortify aqueous samples with known amounts of diquat dibromide monohydrate. A unit of SRM 3072 consists of five 2 mL ampoules, each containing approximately 1.2 mL of solution.
Certified Concentration of Diquat Dibromide: The certified concentration value [1,2], given below, is based on results obtained from the gravimetric preparation of this solution and from the analytical results determined by using liquid chromatography (LC). A NIST certified value is a value for which NIST has the highest confidence in its accuracy in that all known or suspected sources of bias have been investigated or accounted for by NIST.               Diquat Dibromide Monohydrate 39.7 mg/kg ± 0.8 mg/kg
A unit of SRM 3072 consists of five 2 mL ampoules, each containing approximately 1.2 mL of solution.

May 2003

Standard Reference Material (SRM) 2702 is a marine sediment collected at the mouth of the Baltimore Harbor, Baltimore, MD. SRM 2702 is intended for use in evaluating analytical methods for the determination of selected elements in marine or fresh water sediment and similar matrices. All of the constituents in SRM 2702, for which certified, reference, and information values are provided, were naturally present in the sediment material before processing.
Certified values for concentrations, expressed as mass fractions, for 25 elements. The certified values are based on the agreement of results from two or more chemically independent analytical techniques obtained at NIST and collaborating expert laboratories [1]. A NIST certified value is a value for which NIST has the highest confidence in its accuracy in that all known or suspected sources of bias have been investigated or accounted for by NIST.
The sediment used to prepare this SRM was collected from the Chesapeake Bay at the mouth of the Baltimore (MD) Harbor near the Francis Scott Key Bridge (39°12.3'N and 76°31.4'W). This location is very near the site where SRM 1941 and SRM 1941a were collected. The sediment was collected using a Kynar-coated modified Van Veen-type grab sampler. A total of approximately 3300 kg of wet sediment was collected from the site. The sediment was freeze-dried, sieved at 70 µm (100 % passing), homogenized in a cone blender, radiation sterilized at 33 kGy to 45 kGy (60Co) dose, and then packaged in screw-capped amber glass bottles each containing approximately 50.
A unit of SRM 2702 consists of a bottle containing 50 g of radiation-sterilized, freeze-dried sediment material. This SRM is currently in preparation.

May 2003

The prototype sensor system monitors the natural response of bacterial cells bound within the microscopic channels of a plastic microfluidics device—a miniaturized chemical and biochemical analysis system. In the presence of certain chemicals, the cells eject large amounts of potassium, which is detected with an optical sensor that changes color. The prototype was demonstrated as part of an early warning system for industrial pollutants that interfere with sewage treatment, but it also has potential homeland security applications.

Cell-based sensors are of great interest today because they can respond to a wide range of chemical toxins rapidly. NIST’s primary contributions to this project involve expertise in microfluidics technology, particularly aspects such as plastics processing. The new device has a novel configuration in which, through the use of lasers, tiny posts are constructed within the channels to act as a sieve and promote adhesion of the cells.

Although this type of chemical test could be performed in other formats, a microfluidics device is more sensitive because of the high surface to
volume ratio, and also faster because of the close juxtaposition of chemicals and cells. In addition, it consumes less reagent and sample material and could be used in a distributed sensor network for real-time field testing. The device was designed in collaboration with scientists at Virginia Polytechnic Institute and State University (Blacksburg, Va.) and Veridian Pacific-Sierra Research (Charlottesville, Va.).

March 2003

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Date created: May 13, 2002
Last updated: May 6, 2004
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