Showing papers on "Fluorescence spectrometry published in 1979"

Inductively coupled plasma-atomic emission spectroscopy: Its present and future position in analytical chemistry

Abstract: This review (with 179 references) is mainly intended to facilitate judgements about the present and future position of inductively coupled plasma-atomic emission spectrometry (ICP-AES) among both various “established” spectroscopic methods and AES methods based on novel plasma sources for liquid analysis. It is considered that a thorough and critical comparison of the capabilities and cost of ICP-AES with those of the existing outfit of a laboratory must be made in each individual situation separately to judge whether ICP-AES as a supplement to or a replacement of one or more established techniques is an economic proposition. From this point of view ICP-AES is reviewed as a relatively new method for the analysis of liquids and dissolved solids. The principle of the method and the basic instrumentation are briefly outlined. The distinction between low-power argon ICPs and high-power nitrogen-argon ICPs is pointed out and the viability of both approaches in the analysis of real samples is noted. Analytical performance is discussed in terms of detection limits, precision, accuracy and dynamic range. Applications of real-sample analysis are given as illustrative examples. A list is included of the best detection limits of 67 elements in aqueous solutions as reported for argon ICPs operated with pneumatic and ultrasonic nebulizers. Detection limits of 15 elements in oil are given to illustrate the potentials of low-power argon ICPs in the field of organic liquid analysis. The detection limits of As, Sb, Bi, Se and Te as achieved by combining hydride generation with an argon ICP, are presented to demonstrate recent progress in the determination of elements for which the detection power was hitherto less satisfactory than desired. With regard to precision, the behaviour of ICPs is pointed out as fluctuation-nose limited systems that are dominated by a relative standard deviation (RSD) of ≤ 1 % in both background and net signals as generated in the source. The dependence of the RSD in the eventually measured net signals (gross signal minus background signal) on the ratio of concentration to detection limit is discussed. An extensive discussion of accuracy incorporates detailed reference to factors such as spectral interferences and reagent impurities, nebulization and transport interferences, “solute vaporization” interferences, and ionization interferences, which may affect the accuracy attained in ICP-AES. It is shown that ICP-AES is relatively free from interferences so that a fair degree of accuracy can be reached, if proper precautions are taken, which, in comparison with AES methods using other excitation sources, or AAS, are not excessive. It is added, however, that the measures needed to ensure fair accuracy will become increasingly severe as the analyte concentration approaches the detection limit more closely or the composition of the sample becomes more complex. It is noted that under these conditions the problems that arc spectroscopists had to face in trace analysis using dc arc spectrography are again encountered, in particular as regards the correct isolation of a net line signal from a background spectrum whose structure depends on the sample composition. The advantages of the large linear dynamic range of three to five orders of magnitude are mentioned. The numerous applications of ICP-AES reported in literature are illustrated with a list of classes of materials for which analyses were described recently. Spectrometers enter into the discussion as indispensable parts of ICP equipment that are necessary for complete analytical instruments and the price of which may be a multiple of that of the ICP source itself. Alternative spectrometers for ICP-AES are grouped into three categories depending on the type of analysis problem: 1) general survey analysis, 2) routine multielement analysis and non-routine multielement analysis with limited flexibility, and 3) flexible single-element analysis. This classification, which fits in with general cost and performance considerations, is used as a convenient basis in the subsequent assessment of the position of ICP-AES among “established” spectroscopic methods. This assessment encompasses comparisons of the capabilities of ICP-AES, flame AES, flame and furnace atomic absorption spectrometry (AAS), de arc AES, spark AES, and X-ray fluorescence spectrometry (XRFS). The position of ICPs with respect to alternative novel plasma sources for liquid analysis by AES is discussed in the light of the historic development. This eventually led to the present situation in which there are at least twelve manufacturers of spectroscopic equipment that are marketing ICP apparatus and one marketing a dc plasma source for liquid analysis, while a renewed commercialization of a capacitively coupled microwave plasma (CMP) is stimulating new interests in CMPs. As to microwave-induced plasmas (MIP), attention is drawn in particular to the TM010 cavity that permits the generation of atmospheric pressure plasmas in helium. These have excellent characteristics as element-selective detectors in gas chromatography and also have many potential applications in multielement and single-element analysis in general, especially for the analysis of microsamples, if these are separately evaporated and atomized, e.g. by electrothermal means, prior to their introduction into the MIP.

Metabolism of benzo[a]anthracene to its tumorigenic 3,4-dihydrodiol.

Abstract: The weak carcinogenicity of benzo[a]anthracene may be due to either low amounts of the tumorigenic 3,4-dihydrodiol formed or poor conversion of this diol to the bay-region diol epoxides, i.e., benzo[a]anthracene 3,4-diol-1,2-epoxides. We have investigated the metabolism of benzo[a]anthracene with rat liver microsomes and a highly purified monooxygenase system reconstituted with cytochrome P-448 to determine the relative amounts of the 3,4-dihydrodiol formed. With liver microsomes from induced and uninduced rats, as well as with the purified and reconstituted system in the presence of epoxide hydrase, benzo[a]anthracene was metabolized predominantly to its 5,6- and 8,9-dihydrodiols. Small but significant amounts of the 3,4- and 10,11-dihydrodiols were also detected by chromatographic methods and fluorescence spectrometry. Since only trace amounts of phenols were detected, the arene oxides of benzo[a]amthracene must be good substrates of epoxide hydrase. With the purified and reconstituted system in the absence of epoxide hydrase, only phenols and the K-region 5,6-oxide were found to be metabolites of benzo[a]-anthracene. Moreover, the extent of metabolism of benzo[a]anthracene was substantially reduced in the absence of epoxide hydrase, suggesting that phenolic metabolites are potent inhibitors. Strong inhibition of the metabolism of benzo[a]anthracene by synthetic 5- and 6-hydroxybenzo[a]anthracenes and by a mixture of phenolic metabolites was observed. ACKNOWLEDGMENTS The authors wish to thank Mrs. Janet Deyhle for her excellent help in the preparation of this manuscript.

Metabolism of Benzo[a]anthracene to its tumorigenic 3,4-dihydrodiol.

Abstract: The weak carcinogenicity of benzo[a]anthracene may be due to either low amounts of the tumorigenic 3,4-dihydrodiol formed or poor conversion of this diol to the bay-region diol epoxides, i.e., benzo[a]anthracene 3,4-diol-1,2-epoxides. We have investigated the metabolism of benzo[a]anthracene with rat liver microsomes and a highly purified monooxygenase system reconstituted with cytochrome P-448 to determine the relative amounts of the 3,4-dihydrodiol formed. With liver microsomes from induced and uninduced rats, as well as with the purified and reconstituted system in the presence of epoxide hydrase, benzo[a]anthracene was metabolized predominantly to its 5,6- and 8,9-dihydrodiols. Small but significant amounts of the 3,4- and 10,11-dihydrodiols were also detected by chromatographic methods and fluorescence spectrometry. Since only trace amounts of phenols were detected, the arene oxides of benzo[a]amthracene must be good substrates of epoxide hydrase. With the purified and reconstituted system in the absence of epoxide hydrase, only phenols and the K-region 5,6-oxide were found to be metabolites of benzo[a]-anthracene. Moreover, the extent of metabolism of benzo[a]anthracene was substantially reduced in the absence of epoxide hydrase, suggesting that phenolic metabolites are potent inhibitors. Strong inhibition of the metabolism of benzo[a]anthracene by synthetic 5- and 6-hydroxybenzo[a]anthracenes and by a mixture of phenolic metabolites was observed. ACKNOWLEDGMENTS The authors wish to thank Mrs. Janet Deyhle for her excellent help in the preparation of this manuscript.

Conformational changes in proteins by low temperature--rapid flow analysis.

Abstract: Publisher Summary This chapter discusses conformational changes in proteins by low temperature through rapid flow analysis. The relationship between protein conformation and function in biochemical reactions has provided an impetus for the development of rapid and sensitive methods for the observation of reaction intermediates. The achievement of the objective requires the integration of several different areas of current research. These include (1) the design of rapid mixing devices, (2) their adaptation to spectral methods that allow identification of the chemical nature of intermediates, (3) the design of rapid scanning detectors (1-10 msec time range), which have excellent spectral resolving powers, (4) the placement of chromophoric groups within the enzyme and/or substrate, which do not interfere with the enzyme reaction but rather act as monitors of its progress, and (5) the use of subzero temperatures to decrease the rate of reaction. The chapter also deals with continuous and stopped-flow methodology and their adaptation to absorption and fluorescence spectrometry. Stopped-flow absorbance and fluorescence instrumentation has been used frequently in the study of both models for enzyme reactions and enzyme-catalyzed reactions themselves. Such instrumentation has been essential to mechanistic studies of ester hydrolysis, imine formation, of ligand interactions with peroxidases and hemeprotein, intermediates in flavoproteins, and alcohol dehydrogenase reactions.

Halothane Biotransformation in Anesthetists

Abstract: Serum bromide levels were measured in 115 anesthetists by use of x-ray fluorescence spectrometry. Bromide levels peaked at 184 +/- 21 micron in anesthetists regularly exposed to halothane (n = 20), at 58 +/- 4 micron in anesthetists sporadically exposed to halothane (n = 71), and at 46 +/- 3 micron in nonexposed anesthetists (n = 24). Kinetic studies were carried out in five other anesthetists after ten days of exposure to halothane. Average daily halothane concentration was 19.2 +/- 3.2 ppm; duration of exposure was 3.8 +/- 0.2 hours/day. Mean serum bromide level increased from 40 +/- 4 micron before exposure to 220 +/- 36 micron on the last day of exposure. Serum bromide half-life was 14 +/- 1.7 days. The study demonstrates that anesthetists debrominate halothane in a dose-related fashion. Serum bromide levels achieved, however, were far below those reported to result in clinical bromism.

A non‐linear least squares fitting routine for optimizing empirical XRF matrix correction models

Abstract: An off-line non-linear least squares fitting procedure is described as part of a program package ‘RUNFIT’. This program supports most of the intensity/correction algorithms currently employed in X-ray fluorescence spectrometry. The program runs under the Data General DOS operating system and requires a minimum hardware configuration of 32K 16 bit words and two floppy disks. The minimization technique is based on the Marquardt scheme which has the main advantage that the step direction taken in the minimization process always lies in the direction of steepest descent. The RUNFIT program includes various statistical tests on the fitted data which enable the user to make accurate judgements as to the quality of the fitted data. Several examples are given of the use of this approach to typical analytical situations.

The application of X‐ray spectrometry to analysis of elemental composition (chemoprinting) in the study of migration of Noctua pronuba L.

Abstract: . 1. Wavelength dispersive X-ray fluorescence spectrometry was used to make quantitative determinations of the elemental composition (chemoprints) of individuals and of bulked males and females of Noctua pronuba. 2. Females caught in light traps at Rothamsted on two successive nights in August 1978 could be separated by significant differences in content of five elements, S, K, Ca, Cu and Zn. Two females, thought on biological grounds to be immigrants, could be distinguished from other, probably resident, females trapped at the same time. 3. Males and females were different in respect of four elements, S, Cl, K and Ca, three of which, S, K, and Ca, were also discriminants between nightly populations of females.

Influence of cation content on adenosine triphosphate determinations in soil.

Abstract: Adenosine triphosphate in soil is measured by the luciferin-luciferase bioluminescence method. Cation exchange in the ATP extraction procedure is used to reduce the content of, e.g., Fe, Al, and Cations in extracts. The efficiency of the cation exchange is determined by measuring the concentration of Fe by X-ray fluorescence spectrometry. The time dependence of the light emission from the bioluminescence process is investigated, and a method for correlating the ATP content and the light emission is proposed.

Response functions for the quantitative evaluation of compromise conditions for multi-element analyses with energy-dispersive X-ray fluorescence spectrometry

Abstract: Figures-of-merit are developed for simultaneous multi-element analysis with energy-dispersive X-ray fluorescence spectrometry. Those derived from information theory frequently give optima in regions of poor excitation of one or more elements and have to be restricted to the region above the absorption edge of the highest Z element; the shapes of the surface described by these and other functions are studied and their optima are compared. A product sum function of inverse Poisson standard deviation gives results that best meet the expectations of X-ray spectroscopists. The location of optima in the space of excitation conditions is dependent upon concentration, but the optimum of the one sample of a batch with the highest overall count rate is still a good compromise between the best experimental conditions and maximum input. These results are substantiated with plots giving the dependence of the figures-of-merit from experimental conditions and with spectra at the optima as defined by the different functions. These equations are potentially useful as objective functions in optimization alogorithms as well as for the comparison between the performance of different X-ray systems.

Ion-implaned reference standards for the analysis of surface impurities by X-ray fluorescence spectrometry

Abstract: X-ray fluorescence spectrometry is capable of the quantitative determination of impurities in and on solid surfaces in concentrations of fractional atomic monolayers. This capability could not be exploited to any large extent in the past due to the lack of suitable standard reference materials. By means of quantitative ion implantation, however, such standards can now be manufactured. They are described and formulae are derived for correcting the fluorescent signal for attenuation due to depth distribution of the impurities as well as for interelement excitation in matrices of higher atomic number than the impurity.

Localization and chemical characterization of a partially purified bovine pineal antigonadotropin

Abstract: An antigonadotropic substance was partially purified from aqueous extracts of bovine pineal glands by methods of gel filtration, ultrafiltration and ion exchange chromatography. Two biological tests,viz. inhibition of compensatory ovarian hypertrophy and reduction of ventral prostate weight, were used to guide the purification. The partially purified antigonadotropin was characterized chemically using techniques of UV and fluorescence spectrometry, thin layer and paper chromatography, paper electrophoresis and amino acid analysis. The results reveal a diversity of ninhydrin-positive components present in the preparations, including free and peptide-bound amino acids, as well as other unidentified components, but not including any of the commonly occurring indoles, indoleamines or catecholeamines. One peptide, oxidized glutathione, was identified in the most purified material containing the biologically active principle yet pure, synthetric glutathione has no antigonadotropic activity in the biological tests utilized. Although the chemical nature of the bovine pineal antigonadotropin remains in question it may be purified by the methods described. The activity is thought to reside in the extremely small, perhaps trace quantities of residues derived. It is believed that large scale, preparative studies will be required for structural determination.

Beam-splitter and cell-window errors in fluorescence spectrometry.

Abstract: Fluorescence excitation spectra should be corrected for distortions caused by spectral variations in the transmittance/reflectance ratio of the beam splitter and by variations in the transmittance of cell windows. The polarization of the excitation beam may cause a large uncertainty in the beam-splitter correction, but this source of error can be eliminated by using angles of incidence of 15°, or less, at the beam splitter. The small distortions due to the transmittances of the sample-cell and quantum-counter entrance windows can be made to cancel one another it the angle of incidence at the quantum counter is also 15° or smaller.

Determination without standards of small amounts of metal compounds on microfilters by X-ray fluorescence spectrometry

Abstract: The extracted minor phases in superalloys are analyzed by X-ray fluorescence spectrometry without the use of standards. The calculation in the analysis is simplified by using a monochromatic X-ray source and the fundamental parameter method. The extracts on the microfilter are approximated by thin film on the filter substrate, though the extracts were not homogeneous. This source permits a simple calculation using the thin film model to transform the measured X-ray intensity to mass thickness and mass fraction, since the mass absorption coefficient for the primary beam is easily found in a commercially available table. A great advantage of this method is that the calculations are possible by using a small programmable calculator.