Journal of research of the National Bureau of Standards最新文献

{"title":"Stable Isotope Dilution GC/MS for the Quantification of Food Contaminants","authors":"J. Gilbert, J. Startin","doi":"10.6028/jres.093.079","DOIUrl":"https://doi.org/10.6028/jres.093.079","url":null,"abstract":"6 Each replicate contained seven pork chops; one-half of the replicates were fried after irradiation. The data obtained from the analyses of the sam- ples described above were used to develop re- sponse surface equations which would predict the effect of the irradiation dose and temperature on each vitamin over the entire area covered by the design. From the equation for the response surface for thiamin loss the predicted losses in pork chops irradiated at 0 'C and then cooked were as follows: 0 kGy, -1.5% (-0.04%); 0.50 kGy, -10.1% (14.3%); 3.5 kGy, -48.7% (54.3%); and 7.0 kGy, -65.9% (69.7%). The values given in parentheses represent the average of the actual observed val- ues. There was no loss of thiamin in the control on a sample weight basis upon cooking, but there was an overall weight loss of about 30%. The effect of temperature on the degradation of thiamin can be illustrated by comparison of the predicted results obtained at a dose of 3.5 kGy, losses of 32.7 (34.9%) and 63.3% (60.2%) at -20' and +20'C respectively. The fit of the predicted values to the measured values is indicated by a R' value of 0.90 for the equation for the response surface. The effect of radiation on thiamin was different in poultry from that observed in pork. The re- sponse surface equation for thiamin loss in chicken breasts cooked after irradiation predicted the fol- lowing losses of thiamin at 0 'C: 0 kGy, + 3.2%; 1.0 kGy, -0.38%; 2.0 kGy, -2.2%; 3.0 kGy, -5.9%; 3.5 kGy, -7.4%; and 7.0 kGy, -34.9%. Thus, in the range of greatest interest for the con- trol of salmonella contamination (3.0 kGy) the loss of thiamin was very low especially when compared to losses in pork chops irradiated and cooked in the same manner.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"365 - 367"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inorganic Trace Analysis by Isotope Dilution Mass Spectrometry—New Frontiers","authors":"J. D. Fassett","doi":"10.6028/jres.093.100","DOIUrl":"https://doi.org/10.6028/jres.093.100","url":null,"abstract":"Isotope dilution mass spectrometry (IDMS) is used extensively at NBS in the certification of elemental concentrations in Standard Reference Materials. It is regarded at NBS as a \"definitive method,\" that is, a method of proven high accuracy. Since the theme of this symposium is accuracy in trace element analysis, it is appropriate to review the role IDMS plays in accurate inorganic analysis. The thesis of this paper is that mass spectrometry is a dynamic technique, marked by continuous productive activity and change, and that new mass spectrometric methods and new ionization techniques promise to make IDMS more general, more available, and more cost effective. Furthermore, I argue that the adoption of this technique by analytical laboratories outside of reference laboratories would do much to broaden the accuracy base of the world's measurements. In IDMS the quantity of an element present in a material is determined from the change produced in the isotopic composition of the element when a known amount of stable isotope (called a spike) is added. Thus, the technique is applicable to all elements with more than one stable isotope, or greater than 60 elements in the periodic table. In practice this number is reduced to those elements readily handled and ionized in the source of a mass spectrometer. In addition, some mononuclidic elements can be determined using radioactive isotopic spikes. For instance, procedures have been developed in our laboratory for iodine and thorium us-","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"417 - 418"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trace Level Quantitation of Phenyltin Compounds Using HPTLC","authors":"K. K. Brown, P. Tomboulian, S. M. Walters","doi":"10.6028/jres.093.054","DOIUrl":"https://doi.org/10.6028/jres.093.054","url":null,"abstract":"The monitoring of LO, for 6-15 days has been carried out several times in the metropolitan area of Tokyo since November 1985, and data on more than 1800 samples have been obtained. Acetaldehyde, C,-C 3 alcohols, and acetone were constantly observed in chromatograms. Acrolein, C 2 -C 3 esters, propionaldehyde, C 4 C5 ethers, and methylethylketone were occasionally detected. This system has worked satisfactorily for more than 2500 hours without any exchange of parts in the devices, and has proved to be practical and durable.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"301 - 305"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of Chromium(III) and Chromium(VI) by Ammonium Pyrrolidine Dithiocarbamate-Methyl Isobutyl Ketone-Furnace Atomic Absorption Spectrometry","authors":"K. S. Subramanian","doi":"10.6028/jres.093.055","DOIUrl":"https://doi.org/10.6028/jres.093.055","url":null,"abstract":"(1] Poole, C. F., and Schuette, S. A., Contemporary Practice of Chromatography, Elsevier, Amsterdam (1984). [2] Poole, C. F., Coddens, M. E., Butler, H. T., Schuette, S. A., Ho, S. S. J., Khatib, S., Piet, L., and Brown, K. K., J. Liq. Chrom. 8, 2875 (1985). 131 Laughlin, R. B., Guard, H. E., and Coleman, W. M., Env. Sci. Tech. 20, 201 (1986). (4] Woggon, H., and Jehle, D., Die Nahr. 17, 739 (1973). [5] Kimmel, E. C., Fish, R. H., and Casida, J. E., J. Agr. Food Chem. 25, 1 (1977). (6] Vasundhara, T. S., and Danhar, D. B., Fres. Z. Anal. Chem. 294, 408 (1979). [71 Ohlsson, S. V., and Hintze, W. W., J. High Resol. Chrom. & Chrom. Comm. 6, 69 (1983). [8] Arakawa, Y., Wada, O., and Manabe, M., Anal. Chem. 55, 1901 (1983). [9] Sherman, J., TLC Technical Series Vol. 2, Whatman Chemical Separation Inc., New Jersey, 1981. [101 Brown, K. K., and Poole, C. F., J. High Resol. Chrom. & Chrom. Comm. 7, 520 (1984). [II] Brown, K. K., and Poole, C. F., L. C. Mag. 2, 526 (1984). Determination of Chromium(III) and Chromium(VI) by Ammonium Pyrrolidine DithiocarbamateMethyl Isobutyl Ketone-Furnace Atomic Absorption Spectrometry","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"305 - 307"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transferring Accuracy to the Trace Level and Then to the Field","authors":"Paul De Biévre","doi":"10.6028/jres.093.142","DOIUrl":"https://doi.org/10.6028/jres.093.142","url":null,"abstract":"[5] Piccone, T. J., Butrymowicz, D. B., Newbury, D. E., Mannig, J. R., and Cahn, J. W., Scripta Met., 839 (1982). [6] Myklebust, R. L., Newbury, D. E., Marinenko, R. B., and Bright, D. S., Background Correction in Electron Microprobe Compositional Mapping with Wavelength-Dispersive X-ray Spectrometry, Microbeam Analysis, San Francisco Press (1987) 25. [7] Garruto, R. M., Swyt, C., Fiori, C. E., Yanagihara, R., and Gajdusek, D. D., Lancet, 1353 (1985).","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"40 1","pages":"520 - 525"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhanced Multidimensional Luminescence Measurements Through Cyclodextrin Complexation","authors":"I. Warner, G. Nelson, G. Patonay, L. Blyshak, S. Neal","doi":"10.6028/jres.093.109","DOIUrl":"https://doi.org/10.6028/jres.093.109","url":null,"abstract":"Cyclodextrins (CDxs) are cyclic oligosaccharides made up of 6, 7, or 8 glucopyranose units for a, /3, and y-CDx, respectively. These molecules are torus-shaped, with an interior cavity size ranging from 5 A for the smaller a-CDx to 10 A for the larger y-CDx. While the CDx is water soluble, the cavity is characterized as hydrophobic. Consequently, an appropriately sized hydrophobic molecule can form an inclusion complex with the CDx. Often, the molecules involved in these complexes exhibit different properties than their uncomplexed forms, such as precipitation of the CDx complex, or a change in spectroscopic parameters of the included molecule. Cyclodextrin chemistry therefore offers a means for gaining selectivity and sensitivity in a variety of analytical measurements. Many studies have demonstrated that the selectivity and accuracy of quantitative measurement of individual luminophors in a complex sample can be enhanced by simultaneous exploitation of multiple parameters. The combination of many multiple parameters could potentially provide specificity for the measurement. The most commonly used form of multidimensional luminescence measurement is the excitation-emission matrix (EEM), i.e., the measurement of the luminescence as a function of multiple excitation wavelengths (X,) and multiple emission wavelengths (XI,,). in this talk, we discuss the use of CDxs to enhance selective detection via EEM measurements. Particular emphasis will be placed on the enhanced measurement of luminophors complexed with CDxs in the presence of select alcohols and quenchers. In addition, the use of solvent extraction and data analysis to reduce the dimensionality of the acquired EEM will be discussed. Cyclodextrin complexation has been demonstrated to enhance the fluorescence of many types of included molecules. The lengthening of fluorescence lifetime [l], change in the fluorescence quantum yield [2], and shifts in the peak shape and position [3] have been observed as a consequence of complexation of fluorophors with CDxs. The addition of aliphatic alcohols to CDx systems has been shown to further enhance changes in these parameters [4]. These changes are often used to quantify the formation constants of a particular complex. Yet, in many instances, such changes are not of sufficient magnitude to quantify an analyte in a complex matrix. One method of further enhancing the selectivity of CDx complexation is through the use of added quenchers. The accessability of some quenchers to a fluorophor is reduced by complexation of the fluorophor with CDxs. The presence of aliphatic alcohols further reduces the quenching of a CDx included fluorophor. A model system employing naphthalene and B3-CDx will be discussed to demon-strate these principles. Appropriate SternVolmer type equations will be presented to explain the quenching phenomena observed in these studied. Quenching may be successfully exploited for the analysis of a mixture of fluorescent molecules in the pres","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"438 - 439"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Automation and Application of a Direct-Current Plasma Emission Spectrometer","authors":"M. S. Epstein, R. E. Jenkins, K. S. Epler, T. O'Haver","doi":"10.6028/jres.093.118","DOIUrl":"https://doi.org/10.6028/jres.093.118","url":null,"abstract":"The direct-current plasma (DCP) coupled to an echelle spectrometer has been used for over 6 years in our laboratory as one of several independent methods for the certification of Standard Reference Materials (SRMs). The demanding certification process requires maximum performance from an analytical method as well as a good understanding of the method capabilities and limitations. We have made a number of modifications to the conventional DCP spectrometer to improve accuracy, precision, and analysis speed. Figure I is a schematic diagram of the entire DCP spectrometric system with all modifications and enhancements. This paper discusses these modifications and their application to a number of analytical problems.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"458 - 462"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Accuracy in CPAA for C, N and O and in ERDA and NRA for H","authors":"T. Nozaki","doi":"10.6028/jres.093.126","DOIUrl":"https://doi.org/10.6028/jres.093.126","url":null,"abstract":"Trace amounts of H, C, N and 0 can be determined by only a few methods, often with rather poor accuracies. Charged particle activation analysis (CPAA) is highly reliable for C, N and 0, and is used for calibration of other methods. Elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA) have recently been utilized for H and D near the surface. Accuracies in these analyses are discussed on the basis of our experimental data.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"482 - 484"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microwave Acid Sample Decomposition for Elemental Analysis","authors":"H. Kingston, L. Jassie","doi":"10.6028/jres.093.041","DOIUrl":"https://doi.org/10.6028/jres.093.041","url":null,"abstract":"resistant version of the standard Zymark arm was chosen for this project. A special problem was posed, however, in the handling of these solutions in the volumes required (10-300 mL) without contaminating the delivery devices. A solution was found through the use of peristaltic pumps and three-way pinch valves. These components were assembled into a pump station controlled by digital signals from Zymark's Power and Event Controller [4]. Between test firings, the tygon tubing is replaced to avoid cross-contamination. In addition, the master solutions are shielded in a lead brick lined enclosure-the robot workcell is itself not enclosed. The system that required the most extensive modification is currently enclosed in a stainless steel glovebox [5]. This application called for the transfer of samples of Pu-238 oxides into and out of calorimeters for measurement of their heat output. Pu-238 is an intense alpha emitter and, as an oxide, the particulate acquires a charge. These charged particles are very mobile, quickly contaminate any space, and even migrate into conductors shorting them eventually. All drive electronics were removed from the Zymark robot base and wrist, coatings were removed, and all plastic components were replaced with metal. The only components remaining with the robot arm are the servo motors and feedback potentiometers. Remoted electronics were placed in a separate housing and cabled to through the wall of the glovebox using special hermetically sealed feedthrough connectors. Our experience with radiation environments, gloveboxes, and existing laboratories have led us to begin design of our own robotic arm. The system will be of a gantry geometry and be modular in the x and y dimensions in increments of 6 inches. This will allow us to size the robot to the existing work space and the intended application. The z-axis will be telescoping in on itself to limit the overall height of the robot. The gantry design permits maximum use of the bench space or glovebox floor for modules, while the robot itself uses previously unused space overhead. Laboratory remodelling costs will thus be circumvented. Additional specifications have been reviewed by many researchers and address such areas as material compatibility, precision, controller architecture, tool changing, etc. The arm will be compatible with other commercially available laboratory robotic modules (i.e., syringe stations, balances, centrifuges, etc.). We anticipate having prototypes available within 2 years. References","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"269 - 274"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"History of Trace Analysis","authors":"H. Laitinen","doi":"10.6028/jres.093.013","DOIUrl":"https://doi.org/10.6028/jres.093.013","url":null,"abstract":"In the era of classical analysis when major and minor constituents of materials such as rocks and ores were determined by gravimetric and titrimetric methods, a measure of the quality of an analysis was the closeness to which the summation of constituents approached 100%. Trace constituents were considered to be those known to be present but in amounts so small that they made no appreciable contribution to the summation. An early authority was Hillebrand [1], who in 1919 wrote his classic book \"Analysis of Silicate and Carbonate Rocks\" and used the word \"trace\" to designate constituents present below the limit of quantitative determination, which meant below 0.01 or 0.02 percent. Sandell [2], in his 1944 book \"Colorimetric Determination of Traces of Metals,\" considered major constituents to be those present in amounts greater than 1%, minor constituents to be those present in amounts between 0.01 and 1%, and trace constituents those below 0.01%. The modern definition of \"trace\" is more flexible, as illustrated by a quotation from a 1965 book, \"Trace Analysis\" edited by George Morrision [3]: \"The connotation of the term \"trace\" varies with the background or interests of the reader.\" In that book, the upper limit was considered to be about 100 ppm by weight, and the term \"ultratrace\" was used for constituents below 1 ppm. To quote further, \"any sharp division is, of course, superfluous, and will depend on the nature of the sample to be analyzed, the analytical technique employed, and the analyst.\" For trace analysis to emerge as a specialty in its own right, two conditions had to be met: specific needs and applicable methods. Qualitative methods in general emerged much earlier than quantitative ones. Quite a few qualitative tests and even a few quantitative methods of great sensitivity existed before the turn of the century, but they remained largely unused as interesting curiosities until a need arose. The decade of the 1940s represented a watershed in creating a variety of new demands for analytical methods of exceptional sensitivity and difficulty. World War II had quite a stimulating effect with respect to new needs, but it also stifled free publication for several years, with the result that shortly after the end of the war in 1945, there was a release of enormous amounts of previously classified material for publication. Methods and instrumentation developed to solve specific problems now became available for wider application. It is now convenient to consider five periods in history-(I) antiquity to the beginning of modern chemistry late in the 18th century, (2) late 18th century through the 19th century, (3) the period from 1900 to 1939, (4) the decade of the 1940s, and (5) the period from 1950 to the present.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"175 - 185"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}