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

{"title":"Applications of Mass Spectrometry in Polymer Analysis: Use of GC-GC-High Resolution MS to Identify Photo- and Oxidative Degradation Products of BPA-Polycarbonate","authors":"W. V. Ligon, A. Factor, R. J. May","doi":"10.6028/jres.093.090","DOIUrl":"https://doi.org/10.6028/jres.093.090","url":null,"abstract":"A full understanding of any chemical process usually requires the complete elucidation of all of the reactants involved and all of the products produced. Even products produced in very minor quantities can be important because they may provide mechanistic clues. The photooxidative degradation of polymers is an economically important process. If we are designing windows of a clear plastic then stability to light is all important in order to extend useful life. If we are designing certain kinds of single-use containers then we may wish them to degrade rapidly in order to minimize the potential for environmental contamination. Identifying the products of the photooxidation process is, however, an unusual challenge for the analytical chemist. Especially in the early stages of the process, the products are likely to remain bound to the polymer backbone whose molecular weight may typically lie in the tens of thousands.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"394 - 396"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362461","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":"ICP-AES: A Realistic Assessment of Its Capabilities for Food Analysis","authors":"J. Jones","doi":"10.6028/jres.093.075","DOIUrl":"https://doi.org/10.6028/jres.093.075","url":null,"abstract":"Figure 2. Total concentrations, with associated standard errors from the flame atomic absorption spectrometric step, of several major and minor elements in NBS SRM 1570 Spinach, as a function of subsample. Open and closed data points depict unftiltered and liltered solutions, respectively, used to measure acidsoluble concentrations; the data at extreme right are overall means ± standard error. References","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"358 - 360"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362631","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":"Inaccuracies in Clinical Chemical Analysis","authors":"M. Evenson","doi":"10.6028/jres.093.067","DOIUrl":"https://doi.org/10.6028/jres.093.067","url":null,"abstract":"Lithium and copper are distributed equally between cells and serum. However, red cells contain more magnesium, zinc, and iron than does serum. To assure analytical accuracy, hemolysis should be avoided. Also, cells and sera must be separated shortly after sample collection. Since aqueous solutions leach magnesium from glass containers, materials and reagents meant for magnesium analysis should be stored in plastic containers wasted to reduce trace nmeta] content. Specimens for zinc analysis are best collected and stored in washed plastic containers to avoid contamination by the zinc present in rubber stoppers of the usual evacuated tubes. Both flame and electrothermal atomization techniques can be applied to the analyses of these metals. Flame atomization is more practical for routine clinical determinations of lithium, magnesium, and zinc. Electrothermal atomization is preferred for copper and iron analyses. Background correction is essential for electrothermal atomization AAS.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"336 - 338"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362689","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":"Homogeneous Electrochemical Immunoassay Using a Chemically Modified Electrode","authors":"R. M. Kannuck, J. Bellama, R. Durst","doi":"10.6028/jres.093.138","DOIUrl":"https://doi.org/10.6028/jres.093.138","url":null,"abstract":"1 [3] Moleman, P., and Borstrok, J. J. M., Biogenic Amines 3, 33 (1985). [4] Westerink, B. H. C., and Mulder, T. B. A., J. Neurochem. 6, 1449 (1981). [5] Causon, R. C., Carruthers, M. E., and Rodnight, R., Anal. Biochem. 116, 223 (1981). [6] Kobayashi, S., Sekino, J., Kazumasa, H., and Imai, K., Anal. Biochem. 112, 99 (1981). [7] Mellbin, G., J. Chromatogr. 6, 1603 (1983). [8] Imai, K., in Methods in Biogenic Amine Research, Eds., Parvez, S., Nagatsu, T., Nagatsu, 1., and Parvez, H., Elsevier, New York (1983) Chapter 2. [9] Imai, K., Toyo'oka, T., and Miyano, H., Analyst 109, 1365 (1984). [10] Mori, K., and Imai, K., Anal. Biochem. 146, 283 (1985). [11] Todoriki, H., Hayashi, T., Naruse, H., and Hirakawa, A., J. Chromatogr. 276, 45 (1983). [12] Imai, K., J. Chromatogr. 150, 135 (1975). [13] Yui, Y., and Kawai, C., J. Chromatogr. 206, 586 (1981). [14] Yui, Y., Kimura, M., Itokawa, Y., and Kawai, C., J. Chromatogr. 177, 376 (1979). [15] Roth, M., Anal. Chem. 43, 880 (1971). [16] Udenfriend, S., Stein, S., Bohlen, P., Dairman, W., Leihgruben, W., and Weigle, M., Science 178, 871 (1972). [17] Benson, J. R., and Hare, P. E., Proc. NatI. Acad. Sci. USA 72, 619 (1975). [18] Matuszewski, B., Givens, R. S., Srinivasachar, K., Carlson, R. G., and Higuchi, T., J. Org. Chem. 51, 3978 (1986).","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"506 - 508"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362820","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":"A Uniform Concept for Error Estimation in Gamma-Ray Spectrometry","authors":"P. Zagyvai, L. Nagy, J. Solymosi","doi":"10.6028/jres.093.125","DOIUrl":"https://doi.org/10.6028/jres.093.125","url":null,"abstract":"The estimated errors of peak areas are primarily important results for the complete analytical process (e.g., activation analysis or environmental radiocontamination assay). Many excellent program routines were offered in the literature for determining peak areas; however, no unambiguous solution has been given so far for assigning accurate error estimation methods. As an introduction to our \"uniform concept\" some basic principles are to be stated:","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"481 - 482"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363074","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":"Voltammetric Sensors Using Chemically Active Electrode Materials","authors":"C. O. Huber","doi":"10.6028/jres.093.129","DOIUrl":"https://doi.org/10.6028/jres.093.129","url":null,"abstract":"Voltammetric analytical techniques have ordinarily used relatively inert conducting materials in order to maximize the range of available applied potential and to enhance selectivity of the electrode reactions by control of applied potentials. A number of investigators have recently been examining modification of electrode surfaces in order to improve selectivity and sensitivity which are essential components to enhanced accuracy at trace levels. These modifications include bonded chemical functionalities, adsorption, polymers, use of electrode paste vehicle solubility, enzyme attachment and others. In the work reported here the use of several chemically active electrode materials is reported. In flow-through voltammetric devices, such as for HPLC and FIA detectors, the chemical history of the electrode surface is relatively easily managed so that sometimes chemically active electrode materials can offer advantages. Further, these onstream voltammetric configurations offer the advantages of controlled convection, electrode surface history, and ease of detector design. In this laboratory some recent studies exemplifying such an approach have involved nickel/nickel oxide [1-3], copper/copper oxide and silver iodide [4] as working electrode materials. Nickel electrodes have allowed the smooth oxidation of hydroxyl and amine as well as more easily oxidized organic functional groups. The typical electrode conditions include 0.1 M sodium hydroxide as electrolyte. Often 0.1 mM nickel sulfate is added to the electrolyte to enhance long-term activity to slower reacting analytes. Typically a flow rate of 1 mL/min and a sample injection volume of 25 FL is used. The anodic current is controlled by redox reaction rate of the electrodes higher oxide lattice sites with the analyte molecule. This allows for low concentration level determinations of sugars, alcohols, glycols, amino acids, proteins, nucleic acids and nucleic acid constituents. Although the carrier stream is alkaline, acidic samples can be readily accommodated using the flow injection technique. The low-pH sample plug first produces a cathodic component to the signal as part of the electrode oxide layer is reduced, but as the pH increases with the passing of the low-pH segment a fresh, high-activity oxide layer is produced which oxidizes the end of the sample plug. Samples with pH as low as two can be accommodated. Layers of nickel oxide adsorbed on metals other than nickel yielded similar reactions to those using a nickel substrate. Several proteins have been determined at concentrations as low as I mg/L [3]. Sensitivity is enhanced by increased temperature. Sideand end-hydroxyl and amino groups as well as sulfhydryl groups are oxidized, thus the technique is general for proteins, not limited to sulfide or bisulfide as for most electroanalytical methods, or to aromaticity as in UV-absorbance methods. Denaturation of human serum albumin in 0.1 M NaOH was followed by the technique. The results obtai","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"488 - 489"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363139","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":"Adsorptive Stripping Voltammetry—A New Electroanalytical Avenue for Trace Analysis","authors":"Joseph Wang","doi":"10.6028/jres.093.130","DOIUrl":"https://doi.org/10.6028/jres.093.130","url":null,"abstract":"nickel can also be determined using a copper anode. Conditions are similar to those for nickel except that the applied potentials must be 200 mV more positive than for nickel. The anodic reaction rate constants with copper are typically somewhat greater than with nickel, however the applied potential results in increased background noise so that copper offers no signal-to-noise advantage over nickel. When the background electrolyte contains nickel as suspended nickel hydroxide as described above, copper, nickel, cobalt, silver, platinum, and gold electrodes yield similar analytical currents. These results indicate that suspended nickel hydroxide adsorbs to the metal electrode surfaces and essentially converts them to nickel oxide electrodes. Silver iodide in its room-temperature crystal form is sufficiently conducting so that it can carry the currents necessary for analytical amperometry. The electrode material is contacted using silver epoxy. The cathodic electrode mechanism involved generation of iodide at the silver:silver iodide interface yielding a current proportional to the rate of oxidation of iodide ions at the silver iodide:solution interface. Hypochlorous acid at sub-parts-per-million level thus yields cathodic currents for pH 6 solutions whereas pH 3 must be used for cathodic amperometry of monochloramine [4]. Accordingly a direct, linear response analytical technique for concentrations from more than 5 mg chlorine per liter down to about 10 gg chlorine per liter was developed for either monochloramine or the sum of hypochlorous acid plus monochloramine. The concentrations determined were sufficiently low to allow determination of the rate constant for monochloramine formation under realistic water treatment concentration, pH, and ionic strength conditions. The rate constant obtained was 3.2X 106 L/mol/s, in agreement with earlier reported values extrapolated from higher concentrations and less moderate pH solutions.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"489 - 491"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363145","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":"Expert Systems and Robotics","authors":"T. Isenhour, J. C. Marshall","doi":"10.6028/jres.093.019","DOIUrl":"https://doi.org/10.6028/jres.093.019","url":null,"abstract":"In the early sixties, AI researchers attempted to simulate the complicated process of thinking by finding general methods for solving broad classes of problems. This proved too difficult and such attempts failed. In the early seventies the problem was reformulated to include careful attention to data structures but the emphasis was still on general knowledge. Progress was still limited. In the late seventies the problem was further refined to focus almost completely on the knowledge representation. The goal was to make intelligent programs by providing them with high quality, domain-specific knowledge about some limited problem area. This strategy is much like that used by a human expert and gives rise to the term \"expert system.\" What domains are appropriate for expert system work? First and foremost, for the present state of expert systems technology the problem domain must be of limited scope. A majority of the people within the application field must agree that real experts do exist. The problem must be knowledge, not data, intensive. A problem is knowledge intensive if there is substantial variability in people's ability to solve it. The problem must not require information from visual input. Multiple answers from the same input data can be handled but with limited success. Perhaps the best test of all for a potential candidate for expert system work is the so-called \"telephone test.\" If you have a problem and you are confident that if you called some known expert in the field, he or she could solve the problem for you in 30 minutes or less over the phone, then the problem is likely to be amenable to an expert system solution. How do expert systems compare with human experts? The popular press has tended to be wildly optimistic about the present state of expert systems development. While many useful expert systems are available, they apply to very limited problem domains. In such domains expert systems can quickly provide answers that are consistent and objective. Expert systems can capture human expertise and make it permanent, widely available and easily portable. However, current expert systems lack the creativity and adaptability expected of a human expert. How do expert systems work? Regardless of the details of the implementation, an expert system is a program driven by an inference engine towards a specific goal. It is, in the limit, a remarkably simple","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"209 - 212"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71361732","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 Trace Analysis","authors":"G. Kateman","doi":"10.6028/jres.093.021","DOIUrl":"https://doi.org/10.6028/jres.093.021","url":null,"abstract":"Most analytical measurements are not absolute but depend on the correlation between physical phenomena and some intrinsic property, e.g., concentration. Therefore, calibration is an indispensable part of analytical chemistry. Unfortunately, calibrations are not free from interference by the environment. This disturbing environment can be the micro-environment, components in the sample that influence the calibration line. As a rule this interference is usually constant, though not always (e.g., separation processes). The macro-environment, however, changes continuously. Temperature, pressure, chemicals, and man are stationary only during a short time. These influences will be seen as random fluctuations or, when autocorrelated, as drift. One approach is to monitor the properties of the calibration system internally by incorporating a calibration system and a measuring system. By monitoring the calibration system, the results of the unknown can be corrected. Kalivas and Kowalski [1] described the solution for the multicomponent situation, using the generalized standard addition method (GSAM). By treating drift as a time dependent component they obtain the equation","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"217 - 218"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71361745","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":"Pharmaceutical Trace Analysis","authors":"D. Aldrich, S. J. Borchert, A. Abe, J. E. Freeman","doi":"10.6028/jres.093.031","DOIUrl":"https://doi.org/10.6028/jres.093.031","url":null,"abstract":"of an analyte specific clean-up is useful in minimizing this problem. Identification of the species producing the effect and application of specific clean-up steps can eliminate problems. Low results can result from incomplete analyte extraction, loss or degradation of the analyte during sample clean-up, or matrix effects. These problems can be eliminated by a careful evaluation of each of the steps employed in the sample preparation. 1) Extraction efficiencies can be improved by dissolving the sample matrix whenever possible and determining the optimum solvent for analyte extraction. When dissolution of the matrix is not practical, an exhaustive extraction procedure with an optimum solvent should be used. 2) Loss or degradation of the analyte can be controlled by determining the recoveries of all analytes through each clean-up step. An understanding of the chemical and physical properties of the analyte will not only improve recoveries, but also can allow optimization of each clean-up step. 3) Matrix effects leading to low results generally are caused by exceeding the capacity of the clean-up procedure for either analytes, related compounds, or coextractive species. This \"overloading\" can change the chromatographic retention of the analyte. In general, these effects can be minimized by decreasing the sample size or using a highcapacity pretreatment step to remove the coextractives. Application of these precautions can result in a method which does not generate false positive or false negative results. A recent collaborative study to determine fortified levels of CDDs and CDFs in human adipose tissue at 5-50 pg/g has been completed by eight laboratories highly experienced in the determination of CDDs and CDFs [Albro et al., Anal. Chem. 57, 2717 (1985)]. By implementing the practices described above, laboratory 2 avoided generating either unaccountably high or low results (table 1). The apparent drawback of the laboratory 2 method is the relatively long analysis time per sample. However, when the standard deviation of the recoveries for each laboratory is calculated and used in the equation to determine the relative time to analyze N samples (measurements necessary to yield data of defined statistical reliability), method 2 can actually generate data with a specified precision in the shortest time. Table 1. Interpretation of recovery data from CDD/CDF collaborative study","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"242 - 245"},"PeriodicalIF":0.0,"publicationDate":"1988-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71361866","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}