Current status of gross alpha/beta activity analysis in water samples: a short overview of methods

Gross alpha/beta measurement is one of the simplest radioanalytical procedures which are applied widely as a screening technique in the field of radioecology, environmental monitoring and industrial applications as well. Due to the uncertainties of gross alpha/beta measurements this method is often the subject of discussions and debates. The aim of this work is to collect information about recently used standard and routine methods concerning gross alpha/beta activity determination in drinking waters in order to get an overview about the current situation and evaluate their possibilities. Sample preparation methods—e.g. evaporation, co-precipitation—and detection systems—e.g. gas flow proportional counting, liquid scintillation counting and scintillation counting—are compared on the ground of literature data. In the course of our work, the following parameters were analyzed and discussed: background, counting efficiency, interferences, sample capacity, minimal detectable activity, typical counting time, time demand of sample preparation.     

Dispersive liquid‐phase microextraction in combination with HPLC for the enrichment and rapid determination of benzoylurea pesticides in environmental water samples

Benzoylurea (BU) insecticides have contributed greatly to the output of crops. Their residue in the environment put serious threats on human health and environmental safety. In this study, we have established a new, rapid, and reliable method for the monitoring of typical BU insecticides such as diflubenzuron, flufenoxuron, triflumuron, and chlorfluazuron with dispersive liquid–liquid microextraction prior to HPLC. Chlorobenzene and ethanol were employed as the extraction solvent and disperser solvent, respectively. The possible parameters which would influence the extraction efficiency such as the kinds and volumes of extraction and disperser solvents, extraction time, sample pH, centrifuging time, and salting‐out effect were optimized in detail. Under the optimal conditions, the linear range of proposed method was in the range of 1.0–70 μg/L. The detection limits varied from 0.24 to 0.82 μg/L and the precision of the method was <6.5% (RSD, n = 6). The proposed method was validated with real water samples and satisfactory spiked recoveries were achieved. All these results indicate that the proposed method is a low cost, easy to operate, efficient, and sensitive method for the analysis of BU insecticides in water samples.     

A rapid and sensitive analytical method for the determination of 14 pyrethroids in water samples

A simple, efficient and environmentally friendly analytical methodology is proposed for extracting and preconcentrating pyrethroids from water samples prior to gas chromatography-negative ion chemical ionization mass spectrometry (GC-NCI-MS) analysis. Fourteen pyrethroids were selected for this work: bifenthrin, cyfluthrin, λ-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fenvalerate, fenpropathrin, τ-fluvalinate, permethrin, phenothrin, resmethrin, tetramethrin and tralomethrin. The method is based on ultrasound-assisted emulsification-extraction (UAEE) of a water-immiscible solvent in an aqueous medium. Chloroform was used as extraction solvent in the UAEE technique. Target analytes were quantitatively extracted achieving an enrichment factor of 200 when 20 mL aliquot of pure water spiked with pyrethroid standards was extracted. The method was also evaluated with tap water and river water samples. Method detection limits (MDLs) ranged from 0.03 to 35.8 ng L⁻¹ with RSDs values ≤3–25% (n = 5). The coefficients of estimation of the calibration curves obtained following the proposed methodology were ≥0.998. Recovery values were in the range of 45–106%, showing satisfactory robustness of the method for analyzing pyrethroids in water samples. The proposed methodology was applied for the analysis of river water samples. Cypermethrin was detected at concentration levels ranging from 4.94 to 30.5 ng L⁻¹.     

Two rapid and sensitive automated methods for the determination of nitrite and nitrate in soil samples

Spectrophotometric flow injection methods were developed for the individual determination of nitrite or nitrate, and for the simultaneous determination of nitrite and nitrate, in soil samples. Nitrite was determined directly using a modified version of the Griess-Ilosvay diazo-coupling reaction, measuring at 543 nm the absorbance of the azo-dye complex formed. Simultaneous nitrite and nitrate determinations were based on on-line nitrate reduction in a micro column containing copperised cadmium. A single chromogenic reagent containing all the necessary reactants was used in both methods. For determinations, the chemical and instrumental variables were optimised by univariate analysis and simplex chemometric method. The optimised conditions gave a linear calibration range between 0.05 and 1.6 µg m L^− 1 for N-NO₂⁻ and between 0.05 and 7.0 µg m L^− 1 for N-NO₃⁻. The detection limits for nitrite and nitrate were 22 µg L^− 1 and 44 µg L^− 1 respectively. The proposed methods allowed up to 35-40 samples per hour to be analysed with good precision. The simultaneous method was successfully used for the determination of nitrite and nitrate in soil samples (the results obtained were validated against those obtained by reference methods). The proposed methods are simpler and faster than conventional methods and could be routinely used in environmental monitoring laboratories.     

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.     

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.

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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.

     

Uptake of alpha and beta emitters by mushrooms collected and cultured in Spain

Almost all studies on the radioactive content of mushrooms have been centered on ¹³⁷Cs and, to a lesser extent, on ⁴⁰K. Other alpha and beta emitters have not been fully investigated and, therefore, their contribution to the dose due to consumption of mushrooms is not taken into consideration. We have studied the incorporation of several radionuclides: into mushrooms using two approaches — laboratory and natural conditions. Pleurotus eryngii was cultured under controlled laboratory conditions, and was found that ¹³⁴Cs was incorporated to a greater extent in the mushroom than the rest of radionuclides, and ²³⁹Pu at least. These results were confirmed by the uptake under natural conditions: ¹³⁷Cs > ^228,230,232Th ^234,238U ⁹⁰Sr >> ^239+240Pu. The contribution of thorium and uranium to the dose due to mushroom consumption in Spain is of the same order of magnitude as that of ¹³⁷Cs.This revised version was published online in November 2005 with corrections to the Cover Date.     

Two polydimethylsiloxane rod extraction methods for the sensitive determination of phenolic compounds in water samples

Simple, precise, and low‐cost methods for the simultaneous determination of phenolic endocrine disrupting compounds such as bisphenol A, trichlorophenol, pentachlorophenol, 4‐nonylphenol, and 4‐octylphenol in water samples were developed. The Direct, in situ derivatization methods are based on polydimethylsiloxane rod extraction followed by liquid desorption and chromatographic analysis by liquid chromatography and diode array detection. Several parameters affecting the extraction and desorption of the phenolic compounds and their acetylated derivates were studied, as well as the chromatographic and detection conditions. For the direct method, determination coefficients (r²) > 0.990 and LODs in the 0.6–2 μg/L range were obtained for all compounds except bisphenol A (9.5 μg/L). With the derivatization‐based method, based on in situ acetylation, lower limits of detection (0.3–0.9 μg/L) were obtained for all the compounds with r² > 0.988 and RSDs in the 2–9% range. The developed methods were applied to the analysis of spiked water samples obtaining recoveries of between 60.2 and 131.7% for the direct method, and of between 76.6 and 108.2% for the derivatization‐based method. The results demonstrate the feasibility of using these two methods for determining bisphenol A, trichlorophenol, pentachlorophenol, 4‐nonylphenol, and 4‐octylphenol in water.     

Development of a rapid and automatic optosensor for the determination of cromolyn in biological samples

Disodium cromoglycate (SCG) is an anti-allergic drug, which is applied locally or inhaled. After administration, a very small portion of the drug is absorbed, being the most eliminated part unchanged in the urine and bile; therefore, its determination in urine is indicative of the dose absorbed. Here, the first spectroscopic method for the determination of SCG, making use of a sequential injection optosensor with terbium-sensitized luminescence detection, is described. The cationic resin Chelex-100 was used as solid support in the detection area. The measurements were made at 336/545 nm (λ_ex/λ_em) and the system was calibrated for two sample volumes, 150 and 800 μl, depending on the samples analyzed. A detection limit of 15 ng ml⁻¹ and a RSD lower than 2% (n = 10) were observed using the highest sample volume. The proposed method does not use any organic solvent or surfactant, so being environmental friendly. The analyte was satisfactorily determined in pharmaceuticals and human urine, the latter being spiked at the concentrations found after the administration of the drug.     

Gross alpha and gross beta radioactivity of water samples from ININ and Maquixco in the State of Mexico

The conditions to measure the gross alpha and gross beta radioactivity in water samples from the surrounding of the Nuclear Center (Instituto Nacional Investigaciones Nucleares, (ININ), and Collection, Treatment and Storage Center for Low Level Radioactive Waste (Maquixco) in the State of Mexico were established. The samples were collected from 1987 to 1996. The gross alpha and gross beta radioactivity in the samples were determined by a gas-flow proportional counter. The results indicated that the gross alpha and gross beta radioactive contamination in water samples were below the maximum contaminant level (MCL).     

Supported liquid membrane work-up in combination with liquid chromatography and electrochemical detection for the determination of chlorinated phenols in natural water samples

Summary A sample preparation method has been developed for the determination of chlorinated phenols in water. The method is based on a supported liquid membrane extraction system connected on-line to liquid chromatography with electrochemical detection. The supported liquid membrane technique utilizes a porous PTFE membrane. The membrane is impregnated with an organic solvent which forms a barrier between two aqueous phases and enables selective extraction. The technique can easily be coupled in a flow system. In this investigation five chlorinated phenols (1–5 chlorine atoms) were extracted from natural water samples. Extraction for 30 minutes resulted in detection limits of approximately 25 ng L^–1.     

Rapid titrimetric methods for the determination of vanadium and molybdenum in mixtures

Summary A rapid and accurate method has been developed for the volumetric determination of molybdenum(VI) and vanadium(V) in mixtures, using cerium(IV) sulphate. In this procedure the sample solution is reduced in a mercury reductor (to give Mo^V and V^IV) and an aliquot of the reduced solution is titrated with Ce^IV solution using either ferroin, N-phenyl anthranilic acid, or barium diphenylamine sulphate as indicator. This titration gives the amount of molybdenum present, as V^IV does not interfere under the conditions applied. Another aliquot of the reduced solution is titrated with Ce^IV solution and rhodamine 6 G as indicator (observing the quenching of the fluorescence). This titration corresponds to the sum of molybdenum and vanadium. The vanadium content can be calculated by difference.

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Zusammenfassung Zur schnellen und genauen volumetrischen Bestimmung von Molybdän(VI) und Vanadium(V) in Mischungen wird Cer(IV)-sulfat als Reagens verwendet. Die Probelösung wird im Quecksilberreduktor reduziert (wobei Mo^V und V^IV gebildet werden) und ein aliquoter Teil der reduzierten Lösung wird mit Ce^IV-Lösung titriert, wobei Ferroin, N-Phenylanthranilsäure oder Bariumdiphenylaminsulfonat als Indicator dient. Aus dieser Titration erhält man den Molybdängehalt, da V^IV unter den angewendeten Bedingungen nicht stört. Ein weiterer Teil der reduzierten Lösung wird mit Ce^IV-Lösung gegen Rhodamin 6 G titriert (Endpunkt durch Fluorescenzlöschung), woraus man die Summe Mo + V erhält. Der Vanadiumgehalt ergibt sich aus der Differenz.

     

Measuring alpha and beta activity of filter and swab samples with LSC

Analysis of alpha and beta emitters in aerosol filters and swabs of different materials by liquid scintillation counter is discussed. This method appears suitable for fast determination of activity of radionuclides due to direct alpha and beta separation, measurement in 4π geometry and without sample treatment. The selected group of radionuclides was chosen with respect to military significance, radiotoxicity, and possibility of potential misuse. ⁹⁰Sr and ²³⁹Pu were selected as model radionuclides. Three types of filters were examined, and the attention was also focused on optimizing the type and volume of LSC cocktail. The efficiencies for ²³⁹Pu and ⁹⁰Sr were 90% and 79%, respectively. This method was the most effective for the glass fiber filters measured with the MaxiLight cocktail.     

Preparation of magnetic molecularly imprinted polymer for rapid determination of bisphenol A in environmental water and milk samples

A magnetic molecularly imprinted polymer (M-MIP) of bisphenol A (BPA) was prepared by miniemulsion polymerization. The morphological and magnetic characteristics of the M-MIP were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. The adsorption capacities of the M-MIP and the nonimprinted polymer were investigated using static adsorption tests, and were found to be 390 and 270 mg g⁻¹, respectively. Competitive recognition studies of the M-MIP were performed with BPA and the structurally similar compound DES, and the M-MIP displayed high selectivity for BPA. A method based on molecularly imprinted solid-phase extraction assisted by magnetic separation was developed to extract BPA from environmental water and milk samples. Various parameters such as the mass of sorbent, the pH of the sample, the extraction time, and desorption conditions were optimized. Under selected conditions, extraction was completed in 15 min. High-performance liquid chromatography with UV detection was employed to determine BPA after the extraction. For water samples, the developed method exhibited a limit of detection (LOD) of 14 ng L⁻¹, a relative standard deviation of 2.7% (intraday), and spiked recoveries ranging from 89% to 106%. For milk samples, the LOD was 0.16 μg L⁻¹, recoveries ranged from 95% to 101%, and BPA was found in four samples at levels of 0.45–0.94 μg L⁻¹. The proposed method not only provides a rapid and reliable analysis but it also overcomes problems with conventional solid-phase extraction (SPE), such as the packing of the SPE column and the time-consuming nature of the process of loading large-volume samples.     

Method for the rapid atomic-absorption determination of silver in solid carboniferous samples

It is shown that carboniferous samples can be analyzed by injecting them directly into an electrothermal atomizer of an atomic absorption spectrometer as an aqueous suspension stabilized by a surface-active substance. The main factors affecting the stability of the suspension and the metrological characteristics of the procedure are considered; methods for their estimation and approaches to the optimization of the analysis conditions are proposed. A rapid procedure for the determination of silver in carboniferous samples is developed that reduces the time of analysis by several times.     

Multivariate optimisation of a rapid and simple automated method for bismuth determination in well water samples exploiting long path length spectrophotometry

An automated spectrophotometric system is proposed for the determination of bismuth in well water samples, using multi-syringe flow injection analysis (MSFIA) and exploiting a liquid waveguide capillary cell (LWCC). This method is based on the colorimetric reaction of bismuth and methylthymol blue (MTB) in the presence of polyvinylpyrrolidone (PVP) in acid medium (0.1 mol L^?1 HNO₃). The Bi(III)–MTB complex was measured at 600 nm. The method was optimised by multivariate techniques. Some figures of merit of the proposed system are worth being highlighted, such as its wide linear working range (between 4.9 and 600 μg L^?1), its low detection limit (1.5 μg L^?1 of bismuth) and its high intra-day precision and inter-day precision (0.7% (n = 12) and 1.4% (n = 5), respectively, both expressed as RSD). Moreover, a high injection frequency of 30 h^?1 is achieved, as the proposed analyser is a powerful tool for fast Bi(III) determination. The method developed was successfully validated by analysing reference samples (pharmaceutical samples) by comparing the results with those obtained by ICP-OES and it was satisfactorily applied to well water samples. Besides, the present system is miniaturised allowing in situ measurements in control processes and field analysis.     

On the reliability of a rapid method for the determination of90Sr in natural samples

A method for the rapid evaluation of⁹⁰Sr in environmental matrices has been developed. It is a one-day time-consuming procedure compared with 20–25 d of the traditional methods. It is based on a partial measurement of the sample activity and on data extrapolation. This work reports the methodology and its reliability.