Showing papers in "Journal of research of the National Bureau of Standards in 1988"

Octacalcium Phosphate Solubility Product from 4 to 37-Degree-C

Abstract: Etude de la solubilite de l'OCP, important intermediaire dans la formation des dents et des os. Influence d'une atmosphere riche en CO 2

The Application of Flame Spread Theory to Predict Material Performance

Abstract: A review is presented of recent work which attempts to apply flame spread theories to a wide range of materials. The approach is based on using the theories to develop correlations from material data. The data are derived from small scale tests and are expressed in terms of "properties." Various radiant heating apparatus are discussed, and a wide range of results are presented. The focus of the application is fire spread on

High resolution nonlinear laser spectroscopy

Abstract: High resolution laser techniques were developed that address the problems listed above. The techniques are collectively called site selective laser spectroscopy. They relied upon the idea that a narrow band laser could be tuned to excite selectively an absorption line of a specific component or site within a sample so the resulting fluorescence spectrum came only from the site or component excited. One could simplify spectral congestion with this approach. One could also eliminate broadening that was caused by inhomogeneities in the samples because excitation within a broadened line would only excite components that had energy states resonant with the laser so the resulting fluorescence spectrum would not reflect the inhomogeneities. These methods were applied to matrix isolation, low temperature organic glasses, Shpol'skii systems, inorganic analysis using precipitates, and supersonic jet spectroscopy to measure a variety of inorganic and organic materials at ultra-trace levels. The methods all relied upon sample fluorescence and they failed if the samples were non-fluorescent. We have recently shown that there is a new family of high resolution laser spectroscopies that have the same capabilities but do not require a fluorescent sample. These spectroscopies are based upon nonlinear mixing where several tunable lasers are focused into a material and new frequencies are formed at all of the sums and differences of the original laser frequencies. This nonlinear mixing is resonantly enhanced when some of the laser combinations match resonances of components in the sample. The nonlinear mixing can be used to perform atomic spectroscopy and molecular spectroscopy. We will concentrate on molecular spectroscopy in this discussion. One can perform component selection by tuning the lasers to match resonances on one specific component in the sample. One would then expect to have that component contribute dominantly to the nonlinear mixing. One can also eliminate inhomogeneous broadening by tuming the lasers to match the resonances of specific sites within the inhomogeneously broadened line. Again, one would expect that those sites would contribute dominantly to the mixing and the nonresonant sites would be discriminated against. We have tested these ideas in several model systems using four wave mixing spectroscopy. The two model systems are pentacene doped into p-terphenyl crystals and pentacene doped into benzoic acid crystals where p-terphenyl was added in small amounts to introduce controlled amounts of inhomogeneous broadening. The experiments were done at 2 K to eliminate thermal effects. There are four schemes that one can use to establish resonances with the pentacene molecules. In all of them, one establishes resonances with the vibrational levels, the excited electronic states, and the vibrational levels of the excited electronic state (which we will call vibronic states). The four schemes differ in which states are involved in the resonance associated with the emitted light. If the emitted light involves transitions between two levels that are not initially populated, the technique is classified as a nonparametric process. If one of the levels were initially populated, the technique is a parametric process. Theories for the ideas predict that each possibility will have a different ability to provide selectivity in the measurement. The pentacene in p-terphenyl system was studied first. Pentacene has four different crystallographic sites in this crystal, some of which differ only slightly from each other. Conventional spectroscopy shows that the transitions from each

Microwave Acid Sample Decomposition for Elemental Analysis

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

Solid-phase extraction on a small-scale

Abstract: [I] Paterson, K. Y., Veillon, C., and H. M. Kingston, \"Microwave Digestion of Biological Samples for Selenium Analysis by Electrothermal Atomic Absorption Spectrometry\" in Introduction to Microwave Sample Preparation: Theory and Practice, H. M. Kingston and L. B. Jassie, eds., ACS Reference Book Series, in press. [2] Kingston, H. M., and Jassie, L. B., Anal. Chem. 58, 2534 (1986). (31 Pratt, K. W., Kingston, H. M., MacCrehen, W. A., and Koch, W. F., \"Voltammetric and Liquid Chromatographic Identification of Organic Products of Microwave-Assisted Wet Ashing of Biological Samples\" in press.

High-performance capillary electrophoresis

Abstract: High performance capillary electrophoresis is expected to be the fastest-growing analytical technique since HPLC. The method has already shown its utility in a variety of applications.

The NBS scale of spectral irradiance

Abstract: This paper describes the measurement methods and the instrumentation used in the realization and transfer of the NBS scale of spectral irradiance. The basic measurement equation for the irradiance realization is derived. The spectral responsivity function, linearity of response, and “size of source” effect of the spectroradiometer are described. The analysis of sources of error and the estimates of uncertainty are described. The assigned uncertainties (3σ level) in spectral irradiance range from 2.2% at 250 nm to 1.0% at 654.6 nm to 6.5% at 2400 nm.

Expert Systems and Robotics

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

Precipitation of NH4UO2PO4•3H2O ― Solubility and structural comparison with alkali uranyl (2+) phosphates

Abstract: Precipitates formed in the system UO2(NO3)2-NH4OH-H3PO4-H2O, aged for 30 days at 298 K, were studied. The precipitates were characterized by chemical and thermogravimetric analyses, x-ray powder diffraction, infrared spectroscopy, polarized light microscopy, and by their fluorescent properties. The precipitation boundary was established tindallometrically and microscopically. On the basis of these measurements, the stability conditions, structural parameters, and solubility of the tetragonal polymorph of NH4[UO2PO4]·3H2O were determined. This compound shows a close structural relationship with H3O[UO2PO4]·3H2O (space group P4/ncc) and alkali uranyl(2+)phosphates polyhydrates M[UO2PO4]·nH2O (n =4 for M=Li; n =3 for M=Na, K, Rb and n =2.5 for M=Cs). The unit-cell dimensions determined for NH4UO2PO4·3H2O are: a=b=7.02 Å, c=18.08 Å (P4/ncc). The thermodynamic solubility product constant, Ks=a(NH4+)×a(UO22+)×a(PO43−), for NH4UO2PO4·3H2O was determined: log Ks= −26.50±0.09. The Ks values of M[UO2PO4]·n H2O (at ionic strength, I=0.23 mol dm−3) calculated from previously published experimental data by using correct stability constants of uranyl(2+)phosphate complexes are: log Ks=−22.61±0.08 for M=Na; log Ks= −23.92±0.12 for M=K; log Ks= −24.13±0.19 for M=Rb; log Ks= −23.80±0.20 for M=Cs; and log Ks= −24.74±0.10 for M=NH4,showing that NH4UO2PO4·3H2O is less soluble than corresponding alkali uranyl(2+)phosphates.

Diffraction imaging (topography) with monochromatic synchrotron radiation

Abstract: Structural information of special interest to crystal growers and device physicists is now available from high resolution monochromatic synchrotron diffraction imaging (topography). In the review, the importance of superior resolution in momentum transfer and in space is described, and illustrations are taken from a variety of crystals: gallium arsenide, cadmium telluride, mercuric iodide, bismuth silicon oxide, and lithium niobate. The identification and understanding of local variations in crystal growth processes are shown. Finally, new experimental opportunities now available for exploitation are indicated.

Partitioning of alkylbenzenes and aliphatic alcohols between hexadecane and methanol-water mixtures

Abstract: Partition coefficients between n-hexadecane and methanol-water mixtures are reported and analyzed for a series of alkylbenzenes and aliphatic alcohols. A custom-designed flask which has a side arm attached near the bottom was used for the measurements. The hexadecane layer was sampled from the top of the flask, and the aqueous layer was sampled through the side arm of the flask. Both phases were analyzed by an appropriate analytical technique, either gas or liquid chromatography, to determine concentrations. A lattice-model theory suggests a correlation between the hexadecane/methanol-water partition coefficients and the solute molar volume for each solute group type and between the hexadecane/methanol-water partition coefficients and the volume fraction of water in the aqueous phase. The mole-fraction-based activity coefficients calculated from the partition coefficients compare favorably to those determined by a headspace gas chromatographic method. Finally, based upon the data contained herein, the retention mechanism in reversed phase liquid chromatography appears to involve the stationary phase as more than just a passive receptor.

Quantitation of Arsenic Species in Urine for Exposure Assessment Studies

Abstract: Accuracy in trace level clinical or biomedical analyses is of increasing importance as populationbased surveillance is more widely used to address issues of nutritional requirements, environmental exposures, and epidemiological outcomes. Among the uses of such surveillance, evaluation of community exposures from a local arsenic pollution source is one example. Urinary biological monitoring is a desirable tool used in conjunction with measurement of environmental levels of arsenic in order to permit assessment of total exposures and to provide a basis for consideration of the relative importance of different routes of exposure and of age-related behaviors in influencing exposure. Urinary arsenic concentrations are indicative of recent (previous 1-2 days) exposures to arsenic. When total urinary arsenic is measured, total arsenic intake is assessed. When exposures to inorganic arsenic (in the forms of oxides or salts of trivalent or pentavalent arsenic) are of interest, determination of urinary arsenic species comprising the major metabolites of inorganic arsenic exposures is most appropriate [1]. A recent two-year study of community exposures to environmental inorganic arsenic pollution utilized urinary arsenic speciation analysis to assess exposures. In these analyses, part-per-billion sensitivity was achieved with a mean precision of less than 12% coefficient of variation, and with excellent interlaboratory comparability.

Graphite Furnace AAS: Application of Reduced Palladium as a Chemical Modifier

Abstract: Chemical modification techniques are widely used in graphite furnace atomic absorption spectrometry (GFAAS). Palladium is a very effective chemical modifier and can be used to stabilize many elements to several hundred degrees higher than the temperatures possible with current methods [1-9]. Of the elements tested, the greatest temperature shifts are achieved for the semi-metallic elements such as As, Se, Te, Bi, Sb, Pb, TI, Ga, Ge and P. Ash temperatures can be raised 400-800 'C higher than current methods allow. Temperature shifts are somewhat less for the transition elements and ash temperatures can be raised 200-500'C. Palladium has no similar effect on elements in Groups I and 11 of the Periodic Table. The change in stability is believed to be due to the formation of an intermetallic species. This improvement in stability permits more efficient removal of matrix constituents during the ash step and vaporization into a hotter environment during the atomize step. Background and interference problems are thus reduced or eliminated. Steps taken to guarantee that palladium is present as the reduced metal as early as possible greatly improve performance of the modifier. The palladium modifier solution can be pre-injected and the graphite tube heated to 1000 'C. Such a method has been used to stabilize mercury [10]. It is assumed that at this temperature palladium metal is present on the graphite surface. The sample can then be introduced. The addition of a reducing agent such as 5% hydrogen in 95% argon, ascorbic acid, or hydroxylamine hydrochloride also appears to guarantee that the palladium is present as the metal early in the temperature program. The use of hydrogen as a reducing agent appears to be the method of choice for a number of reasons. It is cleaner, leaves no residue, and is less subject to contamination. It is also easy to use. A pre-mixed gas of 5% hydrogen in 95% argon can simply be introduced into the furnace. More importantly, the problem encountered with high concentrations of nitric acid is eliminated with the use of hydrogen. Reduced palladium metal allows the retention of the analyte element on the graphite surface until a higher gas phase temperature is achieved. This appears to give many of the analytical advantages normally associated with platform atomization while using the simpler wall atomization technique. Investigations to elucidate the mechanism of palladium chemical modification have been conducted. Also, comparison of palladium modifier methods with current modifier methods in spike recovery studies from difficult matrices was accomplished. Scanning electron micrographs of graphite surfaces with palladium deposits obtained by different reduction methods were obtained to investigate whether the physical form of palladium influenced the modifier behavior. It was found that reduced palladium metal was indeed present on the graphite surface after reduction and that the most effective reduction method was the use of 5% hydrogen in 95% argon with a palladium solution containing 1% glycerol. The scanning electron micrograph of the surface produced under these conditions is shown in figure 1. The palladium particles are considerably smaller and more highly dispersed than those produced by other methods. The average particle diameter is 0.05-0.15 pAm. The smaller particles result in a great increase in palladium surface area. Spike recovery studies from difficult matrices showed that smaller, highly dispersed particles produced improved interference performance. The interference performance of a palladium/ hydrogen/glycerol method for tin was compared with the performance of a commonly used method. The commonly used method requires the use of the platform and chemical modifiers of ammonium dihydrogen phosphate and magnesium nitrate. Wall atomization was used for the palladium method. The results of this study are listed in table 1. While both methods performed well in concentrated HCl, in most instances the palladium gave slightly better interference performance. It was significantly better in overcoming interferences from NaCI and seawater matrices. Other elements have been tested in the same matrices and, in virtually every instance, palladium gave as good as or better interference performance (wall) as did the currently used methods (platform).

Electrochemical enzyme-immunoassay

Abstract: "Immunoassay" defines the body of techniques which use the antibody (Ab) macromolecule, usually of the IgG class, for the detection and quantitation of an enormous range of simple and complex antigen (Ag) molecules. The success of the methods relies on both the specificity and formation constant of the Ab used, and the ability to detect the interaction between Ab and Ag. Sensitive assays in complex matrices require some kind of label to be present to provide this ability. The development of immunoassay methods has in large part been driven by the available technology. Thus, although one of the first immunoassays using a label was electrochemically based [1], the state of that art in 1951 was relatively primitive, and could not meet the analytical demands of the Ag. Some years later, Yalow and Berson [2] developed immunoassays based on the radioisotopic label (RIA). For the first time, Ab selectivity was married to very low detection limit technology, and the result was an enormous growth rate in the use of RIA in both the clinical and research laboratory. RIA has the significant advantage that the label used is not a normal constituent of physiological samples, and interferences of this type are therefore absent. RIA, however, has the disadvantages that accompany radioisotope handling, together with an inability to distinguish label which is bound from that which is not. There has therefore been an enormous effort to find suitable replacements for the radiolabel. Where the low detection limit of RIA was not required for a successful assay, labels detectable by spectroscopic methods have become important. Where very low detection limits are demanded, then the concept of amplification of, or by, the label has been developed. The most successful of these have been enzyme linked using an immunosorbent phase for Ag extraction (ELISA), although assays based on the lysis of label-containing liposomes are also exhibiting very low detection limits. In our hands, electrochemically based immunoassays at very low detection limits have also used enzyme amplification and ELISA, with either NAD/NADH and glucose-6-phosphate dehydrogenase [3], or phenyl phosphate/phenol and alkaline phosphatase [4]. The greatest sensitivity thus far has been obtained with ELISA coupled with liquid chromatography with electrochemical detection (LCED) [5]. The power of this approach can be readily illustrated by examining the evolution of its use in an assay for IgG, itself an important analyte. This evolution covers three principal stages of development and a reduction in detection limit of five orders of magnitude. The basic methodology is shown in figure 1. The assay is essentially a "sandwich" ELISA, using an alkaline phosphatase labelled second Ab for amplification. Oxidative flow amperometry at +875 mV

Convective velocity effects on a thermistor in water

Abstract: Electrical powers from 5 to 150 μW were dissipated in a thermistor, causing it to rise to equilibrium temperatures above the stagnant surrounding water. Natural convection was then simulated by forced convection of water flowing up or down at known rates from 1.3 to 17 mm/min. The disturbances of the equilibrium temperatures were measured, and are presented as effects of equivalent absorbed dose and absorbed dose rates, positive and “negative.”

Reliable Measurement of Major, Minor, and Trace Elemental Nutrients

Abstract: [1] Harnly, J. M., O'Haver, T. C., Golden, B., and Wolf, W. R., Anal. Chem. 51, 2007 (1979). [2] Miller-Ihli, N. J., Anal. Chem. 57, 2892 (1985). [31 Harnly, J. M., Miller-Ihli, N. J., and O'Haver, T. C., Spectrocim. Acta 39fl, 305 (1984). (41 Harnly, J. M., and O'Haver, T. C., Anal. Chem. 53, 1291 (1981). [5] Kingston, H. M., and Jassie, L. B., Anal. Chem. 58, 2534 (1986). [61 Miller-lhli, N. J., J. Anal. At. Spectrom., in press.

Open tubular liquid chromatography and the analysis of single neurons

Abstract: Liquid chromatography in open tubular columns (OTLC) offers a means of achieving separations of high resolving power within analysis times of minutes to hours. A theory which predicts the optimal dimensions for an open tubular column for a given set of analytical conditions has been developed [1]. This theory predicts that for a wide range of possible inlet pressures and analysis times the most efficient columns will result when the column inner diameter is between 1.5 and 3 prm. A column of 2 Mrm diameter and 2 meter length should be capable of producing a million theoretical plates for an analyte with a capacity factor of 10 (strongly retained) and a retention time of 100 minutes.

Analysis of trace elements in methamphetamine hydrochloride by inductively coupled plasma mass spectrometry

Abstract: [11 Chakrabarti, C. L., Chang, S. B., Thong, P. W., Huston, T. J., and Shaole Wu, Talanta 34, 259 (1987). [2] McNally, J., and Holcombe, J. A., Anal. Chem. 89, 1105 (1987). [3] Box, G. E. P., Hunter, W. G., and Hunter, J. S., Statistics for Experimenters, Wiley, New York (1978). [41 Wegscheider, W., Knapp, G., and Spitzy, H., Fresenius' Z. Anal. Chem. 283, 9 (1977). [5] Schintlmeister, W., Pacher, O., Kailer, K., and Waligram, W., Ion Plating Beschichtungen aus hochschmeizenden Metallen, Proc. 10th Plansee Sem. 2, 635 (1981). [61 Michaelis, M., Thesis, Technical University Graz (1986). [7] Wegscheider, W., Michaelis, M., and Ortner, H. M., Peak Shape Parameters as Indicators for the Occurrence of Interferences in Graphite Furnace Atomic Absorption Spectrometry, in Atomspektrometrische Spurenanalytik (Welz, B., ed.), vol. 3, in press. [8] Wold, S., Wold, H., Dunn 111, W. J., and Ruhe, A., The collinearity problem in linear regression. The partial least squares approach to generalized inverses. Umea University, Report UMINF-83.80 (1982). [9] Wegscheider, W., Michaelis, M., Thai My Phe, and Ortner, H. M., in preparation. Analysis of Trace Elements in Methamphetamine Hydrochloride by Inductively Coupled Plasma-Mass Spectrometry

Some applications of isotope analysis of lead in food by ICP-MS

Abstract: Figure 3. Effect of sampling time on emission responses for Mn (10 ~Lg/L): A, 2 min; B, 5 Sampling rate, 8 mL/min. Elution, nitric acid Steady state response, conventional nebulisatio Introduction injection, multinitric acid (250 The lead concentration in food items is usually low, but accurate measurements of these concentrations are necessary if useful estimates of dietary intake are to be made. Measurements of lead at around 10 ng/g are usually beset by the two problems of sensitivity and, more importantly, matrix effects when atomic absorption techniques are employed. The advent of instruments in which samples are aspirated into an ICP torch (as an ion-source) interfaced with a mass spectrometer (as an ion-counter) open up new possibilities for the accurate measurement of lead in food at normal levels. The present work explores the relative merits of two approaches, viz., standard additions and iso-

History of trace analysis

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.

Increased accuracy in the automated interpretation of large EPMA data sets by the use of an expert system

Abstract: I INPUT, NEXT EXPERIMENTAL k"-WALUES [13] Lohninger, H., and Varmuza, K., Anal. Chem. 59, 236 (1987). [14] Wold, S., Wold, H., Dunn, W. J., 111, and Rube, A., Umea University, Report UMINF-83.80, 1982. [15] Martens, H., Multivariate Calibration: Combining Harmonies from an Orchestra of Instruments into Reliable Predictions of Chemical Composition, 46th Session of the Intern. Statistical Institute, Tokyo (1987). [16] Hellberg, S., A Multivariate Approach to QSAR, Research Group for Chemometrics, Umea University (1986). [171 Wold, S., Sjoestroem, M., Carlson, R., Lundstedt, T., Hellberg, S., Skagerberg, B., Wikstroem, C., and Oehman. J., Anal. Chim. Acta 191, 17 (1986). [181 Bandemer, H., and Otto, M., Mikrochim. Acta 1986 11, 93. [191 Blaffert, T., Anal. Chim. Acta 161, 135 (1984). [20] Otto, M., and Bandemer, H., Anal. Chim. Acta 184, 21 (1986). [21] Otto, M., and Bandemer, H., Chemom. Intell. Lab. Syst. 1, 71 (1986). [22] Kateman, G., J. Res. Natl. Bur. Stand. (U.S.) 93, 217 (1988). [23] Schostack, K., Parekh, P., Patel, S., and Malinowski, E. R., J. Res. Nati. Bur. Stand. (U.S.) 93, 256 (1988). [24] Janssens, K., Van Borm, W., and Van Espen, P., J. Res. Natl. Bur. Stand. (U.S.) 93, 260 (1988). [25] Derde, M. P., and Massart, D. L., Anal. Chim Acta 191, 1 (1986).

Studies of limit of detection on 2,4,6-trinitrotoluene (TNT) by mass-spectrometry

Abstract: Various ionization methods including positive chemical ionization (PCI), negative chemical ionization (NCI) and electron impact (El) were used to study the mass spectra of TNT. Methane, isobutane and ammonia were used as the CI reagent gases. The mass spectrometric quantitation in this study was performed by selected ion monitoring (SIM), with sample introduction via a short capillary column and a solids probe. The best TNT detection limit (ca. 0.020 ng) was obtained with the NCI-SIM technique with isobutane as a reagent gas.

Chemi-luminescence detection in flowing streams - Immobilized and solid-state reagents

Abstract: [1] Fiola, J. W., DiDonato, G. C., and Busch, K. L., Rev. Sci. Instrum. 57, 2294 (1986). [2] Busch, K. L., Fiola, J. W., DiDonato, G. C., Flurer, R. A., and Kroha, K. J., Adv. Mass Spectrom. 10, 855 (1986). [3] DiDonato, G. C., and Busch, K. L., Anal. Chem. 58, 3231 (1986). [4] Stanley, M. S., and Busch, K. L., Anal. Chim. Acta 194, 199 (1987). [5] Busch, K. L., TrAC 6, 95 (1987). [6] Stanley, M. S., Duffin, K. L., Doherty, S. J., and Busch, K. L., Anal. Chim. Acta, in press. [7] Duffin, K. L., and Busch, K. L., manuscript in preparation.

The determination of trace-elements in uranium oxide (U3O8) by inductively coupled plasma emission-spectrometry and graphite-furnace atomic-absorption spectrometry

Abstract: [1] Shan Xiao-quan, Ni Zhe-ming, and Zhang Li, At. Spectrosc. 5, 1 (1984). [2] Shan Xiao-quan, Ni Zhe-ming, and Zhang Li, Talanta 31, 150 (1984). [3] Shan Xiao-quan, and Hu Kaijin, Talanta 32, 23 (1985). [4] Shan Xiao-quan, and Wang Dian-Xun, Anal. Chim. Acta 173, 315 (1985). [5] Liu Ping, Keiichiro Fuwa, and Kazuko Matsumoto, Anal. Chim. Acta 171, 279 (1985). [6] Schlemmer, G., and Welz, B., Poster 077, presented at Colloquium Spectroscopicum Internationale XXIV, Garmisch-Partenkirchen, FRG, September (1985). [7] Niskavaara, H., Virtasalo, J., and Lajunen, L., Spectrochim. Acta, Part B 40, 1219 (1985). [8] Voth-Beach, L., and Shrader, D., Spectroscopy 1(10), 49 (1986). [9] Voth-Beach, L., and Shrader, D., Jour. of Anal..At. Spect. 2, 45 (1987). [10] Grobenski, Z., Erler, W., and Voellkopf, U., At. Spectrosc. 6, 91 (1985). The Determination of Trace Elements in Uranium Oxide (U30d by Inductively Coupled Plasma Emission Spectrometry and Graphite Furnace Atomic Absorption Spectrometry

Assessment of the analytical capabilities of inductively coupled plasma-mass spectrometry

Abstract: [1] Yost, R. A., and Fetterolf, D. D., Mass Spectrom. Revs. 2, 1 (1983). [2] Dawson, P. H., Quadrupole Mass Spectrometry and its Applications, Elsevier, Amsterdam (1976). [31 Dawson, P. H., Adv. Electronics Electron Phys. 53, 153 (1980). (4] Dawson, P. H., Int. J. Mass Spectrom. Ion Phys. 20, 237 (1976). [5] Dawson, P. H., and Fulford, J. E., Int. J. Mass Spectromn. Ion Phys. 42, 195 (1982). [61 Dawson, P. H., French, J. B., Buckley, J. A., Douglas, D. J., and Simmons, D., Org. Mass Spectroni. 17, 205 (1982). [71 Dawson, P. H., French, J, D., Buckley, J. A., Douglas, D. J., and Simmons, D., Org. Mass Spectroma. 17, 212 (1982). [8] Shushan, B., Douglas, D. J., Davidson, W, R., and Naeson, S., Int. J. Mass Spectrom. Ion Phys. 46, 71 (1983). [9] Dawson, P. H., and Sun, W.-F., Int. J. Mass Spectrom. Ion Processes 55, 155 (1983/1984). [10] Martinez, R. I., and Dheandhanoo, S., J. Res. Natl. Bur. Stand. (U.S.) 92, 229 (1987). [III Martinez, R. I., Rapid Commun, Mass Spectrom. (1987), to be submitted. [121 Martinez, R. I., and Dheandhanoo, S., Int. J. Mass Spectrom. Ion Processes 74, 241 (1986). [131 Martinez, R. I., and Dheandhanoo, S., lnt. J. Mass Spectronm. Ion Processes, in press. [14] Martinez, R. I., and Ganguli, B., Int. J. Mass Spectrorn. Ion Processes, to be submitted. [151 Martinez, R. I., Rev. Sci. Instrum., in press.

Evolutionary Factor Analysis

Abstract: Because of chemical interconversion, many chemical systems cannot be physically separated, making chemical identification and quantification difficult. The spectra (IR, UV, Visible, Raman, CD, etc.) of such systems exhibit overlapping contributions of uncataloged components, confounding the identification as well as the quantification. Strategies based on factor analysis [1], a chemometric technique for handling complex multi-dimensional problems, are ideally suited to such problems. Abstract factor analysis (AFA) reveals the number of spectroscopically visible components. Evolutionary factor analysis (EFA) [2-4] takes advantage of experimental variables that control the evolution of components, revealing not only the concentration profiles of the components but also their spectra even when there are no unique concentrations or spectral regions. Evolutionary factor analysis makes use of the fact that each species has a single, unique maximum in its evolutionary concentration distribution curve. We have recently applied this self-modeling method to the infrared spectra of stearyl alcohol in carbon tetrachloride solution. The evolutionary process of this system was achieved by increasing the concentration of stearyl alcohol from 0.0090 to 0.0800 g/L in 15 stages, each time recording the IR spectra from 3206 to 3826 cm '. The spectra were corrected for baseline shift, solvent absorption and reflectance losses. The 15 spectra were then digitized every 3 cm ' and assembled into a 35 x 15 absorbance matrix [A] appropriate for factor analysis. The factor indicator function [1], the reduced eigenvalue [5] and cross validation [6] indicated that three species contribute to the observed spectra. Thus AFA expresses the data matrix as a product of a 35 x 3 absorptivity matrix [E],,,, and 3 X 15 abstract concentration matrix [C],h,,.

Solvent-Free Injection in Supercritical Fluid Chromatography Using Sintered Glass Deposition

Abstract: Sample injection in supercritical fluid chromatography (SFC) is usually performed using a combination of apparatus from liquid chromatography and capillary gas chromatography. The device most often consists of an injection valve (of the type used in liquid chromatography) followed by a flow splitter controlled by a restrictor. It is sometimes desirable to inject samples in the absence of a solvent, as in physicochemical applications of SFC. In this article, two simple modifications to a conventional sampling valve system are presented which allow solvent-free injection. Using these devices, sample (in a solvent) is deposited on a sintered glass bed. After removal of the solvent by mild heating and evacuation, the sample loop is filled with the supercritical carrier and the valve is switched to the inject position.