Comparative methods for determination of rare earths in geological and mineral samples

Particle induced X-ray emission (PIXE) has been used for the quantitative analysis of rare earth elements (REE) in thick targets prepared from geological and mineral samples. Measurements were made with 1 and 3 MeV proton beams. For comparison, determination of the same elements was made by X-ray fluorescence (XRF) using a²⁴¹Am annular source. Minimal detectable limits (MDL) have been estimated for the two situations. Neutron activation analysis (NAA) has also been used for the determination of REE at the ppm level.     

A new method for the determination of low-level actinium-227 in geological samples

We developed a new method for the determination of ²²⁷Ac in geological samples. The method uses extraction chromatographic techniques and alpha-spectrometry and is applicable for a range of natural matrices. Here we report on the procedure and results of the analysis of water (fresh and seawater) and rock samples. Water samples were acidified and rock samples underwent total dissolution via acid leaching. A DGA (N,N,N′,N′-tetra-n-octyldiglycolamide) extraction chromatographic column was used for the separation of actinium. The actinium fraction was prepared for alpha spectrometric measurement via cerium fluoride micro-precipitation. Recoveries of actinium in water samples were 80 ± 8 % (number of analyses n = 14) and in rock samples 70 ± 12 % (n = 30). The minimum detectable activities (MDA) were 0.017–0.5 Bq kg^?1 for both matrices. Rock sample ²²⁷Ac activities ranged from 0.17 to 8.3 Bq kg^?1 and water sample activities ranged from below MDA values to 14 Bq kg^?1of ²²⁷Ac. From the analysis of several standard rock and water samples with the method we found very good agreement between our results and certified values.     

Spectrographic determination of barium and strontium in geological samples

Ohne Zusammenfassung

---

Polarographic determination of Tergitol 08

     

A review on molybdenum determination in solid geological samples

This review highlights the necessity for the development of proper sampling and storage, fast pretreatment methodology followed by highly sensitive detection for the determination of molybdenum in geological samples. Distribution of concentration and chemical speciation of molybdenum analysis in solid geological matrices have also been discussed.     

Anion-exchange separation and spectrophotometric determination of thorium in geological samples

To determine thorium in geological samples it is first separated from all matrix elements by means of anion-exchange. After elution thorium is determined spectrophotometrically by using thoronol or arsenazo III. The suitability of the method for the determination of both trace and larger amounts of thorium was tested by analysing numerous geochemical standard samples with thorium contents in the range of 1-1000 ppm. In all cases very good agreement was obtained.     

Analytical methods for the determination of common booster biocides in marine samples

Booster biocides are organic compounds that are added to antifouling copper-based paints to improve their efficacy. Due to their widespread use, they are common pollutants of marine ecosystems. Some of these compounds show acute and chronic toxic effects in non-targeted organisms at concentrations as low as ng L⁻¹. The determination of these compounds is therefore important, and for some, which are prioritized in the EU water framework directive, a necessity.     

Review of chemical methods for the determination of penicillin

The published methods for the analysis of penicillin are classified according to whether they are intended a) to differentiate between types of penicillin, or b) to determine the total penicillins present in a given sample.The limitations of many of these methods are indicated, and those which are attractive for possible routine application are discussed in detail.     

The determination of molybdenum in geological samples by Neutron Activation Analysis

A metal-silicate extraction technique combined with neutron activation analysis has been developed to determine molybdenum in geological samples. The samples are equilibrated with Femetal powder at high temperatures. Molybdenum is completely extracted into the metal phase because of very reducing conditions in the furnace. The metal spherule is separated from the silicates, irradiated and dissolved in an acid solution. The molybdenum is precipitated as a sulfide and the precipitate is dissolved in aqua regia and counted on a Ge/Li/detector. The radiochemical yield is obtained by irradiation of the solution. The method avoids production of⁹⁹Mo from induced fission of²³⁵U by performing the metal-silicate separation before irradiation. The precipitation step may be necessary to remove the high background from the decay of⁵⁹Fe. Mo concentrations down to 15 ng/g have been obtained using this method.     

Modifications of spectrophotometric methods for total phosphorus determination in meat samples

Spectrophotometric determination of total phosphorus in meat samples was modified using the molybdenum blue reaction with the following reducing agents: ascorbic acid (AA), hydrazine sulphate (HS), and mixture of hydroquinone and hydrazine sulphate (HHS). Proposed methods were validated by evaluation of statistical parameters such as: linearity, sensitivity, limits of detection (DL) and quantification (QL), precision, and accuracy, against the standard and malachite green (MG) modified procedures and by applying food certified materials. The values of within-day and between-days precision in meat samples for all tested reducing agents were better than 3.4 % and 4.2 %, respectively. The recoveries for CRMs analyses were between 92 % and 102.3 %. Obtained results suggest usefulness of the hydroquinone and hydrazine sulphate mixture in the determination of phosphorus ions.     

Development of digital gamma-activation autoradiography for the determination of platinum group element inclusions in geological samples

It has been shown that gamma-activation significantly extends possibilities of activation autoradiography with respect to determination of platinum group elements (PGE) in silicate samples. All PGE may be activated by bremsstrahlung with forming radionuclides having convenient half-lives for autoradiography (hours-days). Digital methods for quantitative 2D-densitometry of autoradiograph images by means of documents scanners have been developed and discussed. Approaches for increasing selectivity of analysis by means of autoradiography have been proposed and tested on the real sample containing PGE inclusions (analysis of decay kinetics while cooling, combination with gamma-ray spectrometry).     

Gas chromatographic methods for the determination of trace organic pollutants in environmental samples

Some problems, special features, and tendencies of the determination of trace organic compounds in various environmental samples with the use of chromatographic methods are considered.     

Review of analytical methods for the determination of chlorine dioxide

The present study reviews more than twenty years (1985-present) of published research on the development and application of analytical procedures for the determination of chlorine dioxide, a widely used disinfectant and bleaching agent. The review covers a variety of techniques including batch and automated spectrophotometry and fluorimetry, electroanalysis and chromatography. The analytical figures of merit to the methods are presented, while critical discussion regarding their advantages and disadvantages is addressed.      

NAA methods for determination of nanogram amounts of arsenic in biological samples

Summary The determination of arsenic at natural levels in biological materials remains difficult. Many analytical techniques cannot detect the low levels present in typical biological tissues and other techniques suffer from interferences. This paper reviews uses of neutron activation analysis (NAA) at NIST to determine nanogram amounts of arsenic in biological reference materials with radiochemical (RNAA) or instrumental (INAA) procedures. INAA is compromised by high activities from ²⁴Na, ⁸²Br, and ³²P that may be formed during irradiation of biological tissues, and result in detection limits as high as 0.1 mg. Lower detection limits have been achieved using state-of-the-art gamma-ray spectrometry systems in INAA and a variety of procedures in RNAA. These techniques and procedures were applied recently at NIST to the determination of arsenic in urine, nutritional supplements, and total diet samples.     

环境样品中多溴联苯醚分析方法的研究进展

多溴联苯醚(PBDEs)作为一类应用广泛的溴代阻燃剂,具有持久污染性、易于从被应用产品中脱离出来进入环境介质等特性,目前已对全球环境造成了严重危害.近年来针对PBDEs分析检测技术的报道愈来愈多,然而PBDEs不仅含量极低,而且所处基体复杂,因此样品前处理技术成为分析PBDEs类化合物的一个重要步骤,受到科学工作者的广泛重视.本文作者综述了近年来分析环境样品中PBDEs的样品前处理技术和分析检测方法的研究进展,为更好的发展准确、灵敏、快速的分析方法提供重要的参考.     

Comparison of different methods for the determination of volatile organic compounds in water samples

The aim of this work was to compare the characteristics of three methods, membrane inlet mass spectrometry (MIMS), purge-and-trap gas chromatography-mass spectrometry (P&T) and static headspace gas chromatography (HSGC), for the determination of volatile organic compounds in water samples as used in routine analysis. The characteristics examined included linear dynamic ranges, detection limits of selected environmentally hazardous volatile organic compounds (e.g. toluene, benzene and trichloroethene) in water, required analysis time and reproducibility of the analytical methods. The MIMS and P&T methods had the lowest detection limits for all the tested compounds, ranging from 0.1 to 5 mug 1(-1). Linear dynamic ranges using the MIMS method were about four orders of magnitude and using the P&T method about two orders of magnitude. Detection limits of the HSGC method were 10-100 times higher than those of the other two methods, but the linear dynamic ranges were larger, even up to six orders of magnitude. The analysis time per sample was shortest for the MIMS method, from 5 to 10 min, and ranged around from 35 to 45 min for the HSGC and P&T methods. The reproducibilities of the methods were of the same order of magnitude, in the range of 1-13%. Agreement between the analytical results obtained for spiked samples and for environmental water samples by the three different methods was very good.     

Potentiometric determination of fluoride in geological and biological samples following pyrohydrolytic decomposition

A method for the determination of fluoride in coal, coal fly ash, phosphate rock, limestone, mineral clay, fossilised materials, oyster tissue and vegetation using pyrohydrolysis for sample decomposition is proposed. A specific apparatus was constructed and the influence of vanadium pentoxide (V₂O₅) as a catalyst for the pyrohydrolysis reaction was investigated. It was verified that V₂O₅ does not influence the release of fluoride from the vegetation, oyster tissue, coal and coal fly ash matrices analysed. However, the catalyst was necessary for the phosphate rock, fossil bone, mineral clay and limestone samples. Certified and noncertified samples were analysed using an ion selective electrode (ISE) for the analyte detection. Precise (relative standard deviation—R.S.D.<7%) and accurate (recovery in accordance to certified values) results were obtained. The limit of quantification (LOQ) of the method was 5.0 μg g⁻¹ of fluoride using 20 mg of sample and a final dilution to 10 ml. The sample frequency was five samples per hour.     

Comparative study of activation analyses for the determination of trace halogens in geological and cosmochemical samples.

Halogens (fluorine, chlorine, bromine and iodine) were determined by activation analyses (neutron activation analysis (NAA), photon activation analysis (PAA) and prompt gamma-ray analysis (PGA)) for geological and cosmochemical solid samples. We studied how each analytical method was for the determination of trace amounts of halogens in rock samples. Radiochemical NAA (RNAA) showed the highest analytical reliability for three halogens (chlorine, bromine and iodine), whereas a set of four halogens (fluorine, chlorine, bromine and iodine) could be determined in principle by radiochemical PAA (RPAA) from a single specimen. Although it is a non-destructive method, PGA showed an analytical sensitivity for chlorine comparable to those of RNAA and RPAA.     

Sensitive methods for the determination of microbial activities in water samples using fluorigenic substrates

Summary Sensitive methods for the determination of several catabolic enzyme activities in the natural water cycle as well as in water treatment plants have been developed. The tests are based on the fluorimetric measurement of dyes which are released by enzymatic cleavage from fluorigenic substrates added to the water sample. On the basis of a linear reaction the turnover rate can be calculated. Compared to photometric tests the detection limits are lower by a factor of 20 to 500, which now allows a precise study of the catabolic activity in samples with low biomass density. In addition, the use of fluorigenic substrates for the determination of microbial enzyme activities provides a higher precision in shorter reaction times compared to photometric tests. In detail, instructions for the determination of esterase, phosphatase, aminopeptidase and glucosidase activities are presented.

---

Empfindliche Methoden zur Bestimmung der mikrobiellen Aktivitäten in Wasser mit Hilfe fluorigener Substrate

Zusammenfassung Es werden empfindliche Methoden zur Bestimmung verschiedener mikrobieller Enzymaktivitäten im natürlichen Wasserkreislauf und in Wasseraufbereitungsanlagen vorgestellt. Die Tests basieren auf der Verwendung von fluorigenen Substraten, die der Probe direkt zugesetzt werden. Die durch enzymatische Aktivität abgespaltenen Farbstoffe werden fluoreszenzspektroskopisch gemessen. Aus der Konzentration der freigesetzten Farbstoffe läßt sich bei linearem Reaktionsverlauf der Substratumsatz in der Probe berechnen. Im Vergleich zu photometrischen Tests sind die Nachweisgrenzen der fluorimetrischen Tests um den Faktor 20 bis 500 niedriger, so daß nunmehr auch eine differenzierte Untersuchung von mikrobiell gering besiedelten Proben möglich ist. Zudem wird eine höhere Genauigkeit bei kürzerer Reaktionszeit erreicht. Im Einzelnen werden Testvorschriften zur Bestimmung der Esterasen-, Phosphatasen-, Aminopeptidasen- und Glucosidasen-Aktivität beschrieben.