Determination of lead in water using laser ablation–laser induced fluorescence

The detection sensitivity of laser-induced breakdown spectroscopy (LIBS) is improved by coupling it with a laser-induced fluorescence method. A waterjet sample containing 500 ppm of Pb as an analyte was ablated by a 266 nm, frequency-quadrupled Q-switchedNd:YAG laser at an energy of ~ 260 μJ. After a short delay the resulting plume was re-excited with a 283.306 nm, nanosecond pulse dye laser at energies ranging from 45 to 100 nJ. The limit of detection (LOD) of lead in water was determined both by the single-pulse LIBS technique and Laser Ablation coupled with Laser-Induced Fluorecence (LA–LIF) method. It was found to be 75 ppm in the case of single-pulse LIBS and 4.3 ppm for LA–LIF. When the resonant pulse was detuned from the transition wavelength the LA–LIF signal disappeared demonstrating the resonant selectivity of this technique.     

胶束电动色谱-激光诱导荧光检测法测定肌松弛药巴氯芬

以4-氯-7-硝基苯并-2-氧杂-1,3-二唑(NBD-Cl)为柱前衍生试剂,建立了胶束电动色谱-激光诱导荧光检测法测定肌松弛药巴氯芬(BAL)的新方法。经过实验条件的优化,采用15 mmol/L硼砂、20 mmol/L十二烷基硫酸钠、10%(v/v)乙腈、pH 9.75的缓冲体系,在分离电压为17.5 kV、柱温为25 ℃的条件下,压力进样3.45 kPa(0.5 psi)×3 s,巴氯芬及其内标物的衍生产物在7 min内实现较好的基线分离,线性范围为0.025～25 mg/L,相关系数为0.9999,检出限(S/N=3)和定量限(S/N=10)分别为0.90 μg/L和6.25 μg/L。该方法被应用于巴氯芬制剂及加入巴氯芬对照品的尿液样品分析,回收率范围分别为101.6%～107.9%和107.0%～109.6%。该方法有望应用于巴氯芬药物制剂的质量监控以及为巴氯芬药物代谢的研究提供辅助手段。     

Determination of uranium in rocks by instrumental activation-analysis using epithermal neutrons

A rapid non-destructive neutron-activation method for the determination of uranium in rocks is described. The method is based on activation with epithermal neutrons and subsequent measurement of the 74 keV gamma-ray of (239)U. Results given for some standard rocks are in good agreement with literature data. The precision of the method is about 5 % and the limit of detection is of the order of 0.1 ppm in silicate rocks.     

Determination of uranium in minerals and rocks

A method is described for the determination of uranium in minerals and rocks by spectrophotometry and fluorimetry. After treatment of the sample with hydrochloric acid, uranium is separated from matrix elements by adsorption on a column of the strongly basic anion-exchange resin Dowex 1 x 8 from an organic solvent system consisting of IBMK, tetrahydrofuran and 12M hydrochloric acid (1:8:1 v v ). Following removal of iron, molybdenum and co-adsorbed elements by washing first with the organic solvent system and then with 6M hydrochloric acid, the uranium is eluted with 1M hydrochloric acid. In the eluate, uranium is determined by means of the spectrophotometric arsenazo III method or fluorimetrically. The suitability of the method for the determination of both trace and larger amounts of uranium was tested by analysing numerous geochemical reference samples with uranium contents in the range 10(-1)-10(4) ppm. In practically all cases very good agreement of results was obtained.     

Attogram detection limits using laser induced fluorescence

Laser induced fluorescence has produced outstanding detection limits in liquid phase analysis. This paper presents a general method for optimizing detection limits as a function of sample volume.     

Interference from uranium in neutron activation analysis or rare-earths in silicate rocks

A direct nondestructive method of analysis for²⁴¹Am utilizing photon counting and self-absorption correction factors is presented. The method gives favorable agreement for samples analyzed by radiochemical separation procedures and alpha particle spectrometry. The comparison was made over a range of approximately five orders of magnitude of²⁴¹Am concentrations. The method is reliable and relatively simple. Sensitivity for a ∼5-g sample and a counting intervals of 60 000 s is ∼0.2 pCi/g with an uncertainty of ±22%, which decreases to ±11% for increased counting intervals of 150 000 s and an increased sample size of ∼20 g.     

Determination of uranium by fluorescence method

The paper describes a procedure for the determination of uranium in dilute solutions by fluorescence method. Factors influencing the determination in a phosphoric acid medium were studied. The detection limit of uranium determination is 0.04–0.05 ppm.     

Determination of calcium in uranium by X-ray fluorescence

Summary An X-ray fluorescence method for the analysis of calcium in uranium in the range of 20 to 500 ppm is described. U₃O₈ samples are mixed with boric acid binder and double-layer pellets are prepared. The pellets are analysed using Philips PW 1220 semi-automatic X-ray spectrometer. Calculated lower limits of detection are better than 5 ppm for calcium in uranium.

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Bestimmung von Calcium in Uran durch Röntgenfluorescenz

Zusammenfassung Ein Verfahren für den Bereich von 20–500 ppm wird beschrieben. Die U₃O₈-Proben werden mit BorsÄure als Bindemittel vermischt zu Doppelschicht-Tabletten gepre\t, die mit Hilfe eines halbautomatischen Philips PW 1220 Röntgenspektrometers analysiert werden. Die untere Nachweisgrenze liegt bei 5 ppm Ca.

     

Determination of the composition of gas mixtures and study of chemical reactions using laser induced fluorescence

The possibility of using infrared Q-switched gas lasers to determine the composition of a gas mixture both when it is fixed and when it is varying with time as in a chemical reaction is discussed.     

Determination of chlorine in silicate rocks by neutron activation analysis

A simple radiochemical neutron activation analysis scheme has been developed for the determination of chlorine in silicate rocks. The method involves a 15-min thermal neutron irradiation of rock powder followed by a quick separation of ³⁸Cl as AgCl, and Ge(Li) spectrometry. Chemical yield, normally ranging between 95% and 100%, is monitored gravimetrically through the recovery of AgCl. The procedure has been tested on several geochemical standards to assess its accuracy and precision. The values obtained for standard rocks agree with the literature values. At the 100-ppm level, the analytical precision for chlorine is within ±5% (2σ).     

Determination of phosphorus in steel by the combined technique of laser induced breakdown spectrometry with laser induced fluorescence spectrometry

Laser induced breakdown spectrometry (LIBS) combined with laser induced fluorescence spectrometry (LIFS) has been applied for detection of trace-level phosphorus in steel. The plasma induced by irradiation of Nd:YAG laser pulse for ablation was illuminated by the 3rd harmonic of Ti:Sapphire laser tuned to one of the resonant lines for phosphorus in the wavelength region of 253–256 nm. An excitation line for phosphorus was selected to give the highest signal-to-noise ratio. Fluorescence signals, P213.62 and P214.91 nm, were observed with high selectivity at the contents as low as several tens µg g^− 1. Fluorescence intensities were in a good linear correlation with the contents. Fluorescence intensity ratio of a collisionally assisted line (213.62 nm) to a direct transition line (214.91 nm) was discussed in terms of the analytical conditions and experimental results were compared with a calculation based on rate equations. Since the fluorescence signal light in the wavelength range longer than 200 nm can be transmitted relatively easily, even through fiber optics of moderate length, LIBS/LIFS would be a versatile technique in on-site applications for the monitoring of phosphorus contents in steel.     

Determination of iron in silicate rocks by substoichiometric radioisotope dilution analysis

Iron is determined in rocks by an isotope dilution method involving dissolution with hydro fluoric acid, extraction of iron(III) chloride into isopropyl methyl ketone, stripping with dilute nitric acid, and substoichiometric separation of the Fe-EDTA complex on a cation-exchange column. The precision and accuracy are 1.5% relative or better, as indicated by analyses of some U.S. Geological Survey standard rocks.     

Determination of phosphorus in silicate rocks by flow injection method of analysis

Summary A flow injection spectrophotometric method has been developed for the determination of phosphorus in silicate rocks. A rock solution is prepared by fusion with a mixture of lithium carbonate and boric acid and subsequent dissolution with l M hydrochloric acid. An aliquot of the sample solution is injected directly into the flow system, which consists of formation of heteropolyacids of molybdenum and antimony, reduction with ascorbic acid, and subsequent measurement of the absorbance of blue species. It permits semi-automated analysis of a variety of silicate rocks for phosphorus. Results obtained for standard rocks were in good agreement with the recommended values. The throughput comes out 20 samples per h.

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Bestimmung des Phosphors in Silikatgestein durch Flie-Injektions-Analyse

Zusammenfassung Ein Verfahren zur spektrophotometrischen Phosphorbestimmung in Silikatgestein mittels Fließinjektion wurde entwickelt. Das Gestein wird mit einer Mischung aus Lithiumcarbonat und Borsäure aufgeschlossen und in 1 M Salzsäure gelöst. Ein aliquoter Teil der Lösung wird unmittelbar in das fließende System injiziert, worin Heteropolysäuren aus Molybdän und Antimon gebildet, mit Askorbinsäure reduziert und die Absorbanz der blauen Farbe gemessen wird. Dies ermöglicht die halbautomatische Analyse verschiedener Silikatgesteine zur Phosphorbestimmung. Die Resultate von Standardproben stimmen mit den vorgeschriebenen Werten gut überein. In der Stunde können 20 Proben durchgesetzt werden.

     

Determination of lanthanides in uranium solutions by X-ray fluorescence spectrometry

An XRF-method for the determination of Sm, Gd, Dy, Er and Eu in uranium solution by use of simple polyethylene bottles has been established. Spectral interferences and matrix effects like absorption enhancement have been rectified using standards of similar composition in the absence of internal standard. Analytical application of the method used has been established on the basis of statistical evaluation.     

Immunoassays using capillary electrophoresis laser induced fluorescence detection for DNA adducts

Human DNA is exposed to a variety of endogenous and environmental agents that may induce a wide range of damage. The critical role of DNA damage in cancer development makes it essential to develop highly sensitive and specific assays for DNA lesions. We describe here ultrasensitive assays for DNA damage, which incorporate immuno-affinity with capillary electrophoresis (CE) separation and laser induced fluorescence (LIF) detection. Both competitive and non-competitive assays using CE/LIF were developed for the determination of DNA adducts of benzo[a]pyrene diol epoxide (BPDE). A fluorescently labeled oligonucleotide containing a single BPDE adduct was synthesized and used as a fluorescent probe for competitive assay. Binding between this synthetic oligonucleotide and a monoclonal antibody (MAb) showed both 1:1 and 1:2 complexes between the MAb and the oligonucleotide. The 1:1 and 1:2 complexes were separated by CE and detected with LIF, revealing binding stoichiometry information consistent with the bidentate nature of the immunoglobulin G antibody. For non-competitive assay, a fluorescently labeled secondary antibody fragment F(ab′)₂ was used as an affinity probe to recognize a primary antibody that was specific for the BPDE-DNA adducts. The ternary complex of BPDE-DNA adducts with the bound antibodies was separated from the unbound antibodies using CE and detected with LIF for quantitation of the DNA adducts. The assay was used for the determination of trace levels of BPDE-DNA adducts in human cells. Analysis of cellular DNA from A549 human lung carcinoma cells that were incubated with low doses of BPDE (32 nM–1 μM) showed a clear dose–response relationship. BPDE is a potent environmental carcinogen, and the ultrasensitive assays for BPDE-DNA adducts are potentially useful for monitoring human exposure to this carcinogen and for studying cellular repair of DNA damage.     

Determination of sulphur in silicate and carbonate rocks by wavelength dispersive XRF

Summary A method has been developed for the determination of sulphur in geological materials within the concentration range 0.003–3%. For samples with differing matrices such as geological materials, the fusion method should be employed for X-ray fluorescence flux mixture analysis. The sample is heated with the Li₂B₄O₇ and LiNO₃ (15) in a Pt-Au crucible to 750° C. It has been experimentally verified that the slow heating of the sample in an electric furnace and the presence of an oxidizing agent allows a quantitative binding of all sulphur so that it does not evaporate during subsequent melting of the sample. The glass disc prepared in this way serves not only for the determination of sulphur but also for that of the other major elements. The relative standard deviation of the newly developed method of 4% and the limit of detection 0.003% suffice for the reliable analysis of sulphur in geological materials.

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Schwefelbestimmung in Silicat- und Carbonatgesteinen mit Hilfe der wellenlängendispersiven Röntgenfluorescenzanalyse

Zusammenfassung Das Verfahren zur Schwefelbestimmung in geologischen Materialien wurde für einen Bereich von 0,003 bis 3% ausgearbeitet. Angesichts der verschiedenartigen Matrix wird ein Aufschlußverfahren empfohlen, bei dem die Probe mit einem Gemisch von Li₂B₄O₇ und LiNO₃ (15) in einem Pt/Au-Tiegel bei 750° C erhitzt wird. Durch langsames Aufheizen und durch die Gegenwart eines Oxidationsmittels wird der Schwefel quantitativ gebunden, so daß er während des Schmelzvorganges nicht verdampfen kann. Die so hergestellte Schmelztablette dient neben der Schwefelbestimmung auch zur Bestimmung der übrigen Hauptbestandteile. Die Standardabweichung der Methode beträgt 4%, die Nachweisgrenze liegt bei 0,003%.