Reference materials for monitoring nutrients in sea water environment

VKI, the Danish national reference laboratory for environmental chemistry, has prepared a range of reference materials for quality control of nutrient analyses in environmental samples. The relevant concentration levels and potential matrix interference effects vary with the sample type. In sea water, nutrient concentrations are in the g/L range and salt concentrations can cause matrix interferences. Two certified reference materials for nutrient analyses were prepared representing the salinities in the Kattegat (20–25 parts per thousand) and the Baltic sea (below 10 parts per thousand). The preparation and certification were an integrated part of a larger project conducted by VKI on the optimisation of nutrient analyses in sea water. Part of the project has been participation in a European interlaboratory trial exercise QUASIMEME [1], which has enabled the Danish reference material data to be traced back to other European data. Denmark has now a certified reference material that will help to ensure the quality of marine analyses that are part of the ongoing national water monitoring plan.     

Ultra sensitive trace gas detection for biomedical applications

We present an overview of our recent progress on spectroscopic trace gas detection for biomedical applications. The latest developments of cavity-enhanced spectroscopy as well as magnetic rotation spectroscopy lead to unprecedented sensitivity and specificity. The current detection limits of our laser spectroscopic approaches are in the picomolar to nanomolar range, depending on the molecular compound. The time resolution of the measurements is down to the sub-second range. This very high sensitivity and time resolution open up exciting perspectives for novel analytical tasks in biomedical research and clinical diagnosis.     

Ultra wide-field lens-free monitoring of cells on-chip

We experimentally and theoretically demonstrate the proof-of-principle of a new lens-free cell monitoring platform that involves using an opto-electronic sensor array to record the shadow image of cells onto the sensor plane. This technology can monitor/count cells over a field-of-view that is more than two orders of magnitude larger than that of a conventional light microscope. Furthermore, it does not require any mechanical scanning or optical elements, such as microscope objectives or lenses. We also show that this optical approach can conveniently be combined with microfluidic channels, enabling parallel on-chip monitoring of various different cell types, e.g., blood cells, NIH-3T3 fibroblasts, murine embryonic stem cells, AML-12 hepatocytes. An important application of this approach could be a miniaturized point-of-care technology to obtain CD4 T lymphocyte counts of HIV infected patients in resource limited settings.     

Aerosol radioactivity monitoring in Bratislava following the Chernobyl accident

The radiation situation in Bratislava following the Chernobyl accident is discussed. Measurement results of - and -radioactivity of aerosols are presented. The evolution of the activity ratios in air for some radionuclides is discussed. Their distribution indicates different transport and deposition properties for the volatile and nonvolatile fission products. The results are compared with long-term measurements of anthropogenic radionuclides released to the atmosphere by nuclear bomb tests.     

Determination of plutonium radioactivity in Mururoa lagoon water

This study presents the plutonium radioactivity levels measured in Mururoa lagoon water during the 1985–1991 period.The low radioactivity levels recorded, from 10^–2 to 1.5 Bq/m³ are due to the slow solubilization of plutonium deposited in lagoon sediments following atmospheric experiments which took place from 1966 to 1974. The average concentrations of the lagoon water tend to decrease from one year to the next. However, the influence of the weather conditions is discussed.The Mururoa lagoon being open to the ocean, plutonium radioactivity traces are still detectable in the immediate vicinity of the atoll.     

Gamma spectrometric monitoring of environmental radioactivity using a mobile equipment

Using gamma-spectrometry systems on mobile units with accurate position information is a convenient means for surveying large areas for radioactive fallout or finding hot spots due to misplaced sources or releases from nuclear installations. Traditionally, large (tens of litres) high efficiency NaI(T1) detectors have been used for the purpose. HPGe detectors, however, offer certain advantages which can often compensate for their lower efficiency. This kind of remote sensing, regardless of detector type, requires specialized software. In order to provide accurate position information, the integration times must be kept as short as possible. This is especially true for fast air-borne measurements where counting periods below one second are desirable. We have constructed a special version of SAMPO software which controls data acquisition and runs real-time gamma-spectrum analysis including peak determination, nuclide identification, activity calculations, and reporting. The measurement/analysis cycle can be reduced down to 0.5 seconds on a standard Pentium-based PC. The analysis results are combined with accurate co-ordinates from a differential GPS system on a color coded map. The system is also able to give alarms based on different criteria. We have already measured and analyzed more than 500 000 spectra in field applications using jets, helicopters, cars, and also on-foot.     

The diurnal monitoring of the air radioactivity using portable instrumentation

A method is proposed which, through the monitoring and modeling of the diurnal variation of α-radioactivity in the air near the ground, appears with a potential in enhancing the measurement of low radioactivity unexpected peaks over the natural background. Portable field instrumentation was used for the monitoring which further included the total γ-radiation at ground level, the relative humidity and temperature. The variation of the α-radioactivity follows a periodic form with peaks in the morning and in the afternoon. The applicability of a mathematical model to describe this variation of the α-radioactivity in terms of the meteorological variables and the γ-radiation was tested positive. This could reduce the difference between the measured and modeled periodic variation to an almost flat one, above which sudden unexpected peaks of radioactivity from possible undeclared nuclear activities could be easier identified.     

Natural radioactivity of geothermal water in Beijing,China

In this work, we collected 101 geothermal water samples to investigate comprehensively the radioactivity of geothermal water in Beijing. The concentrations of gross beta, ²²⁶Ra and ²²²Rn were measured and the obtained values were in the range of 0.032–7.060, 0.023–0.363 and 0.470–29.700 Bq/L, respectively. The samples with higher concentration of ²²²Rn were found to be located near large faults. The effective dose of ²²²Rn in the air for three cases were calculated to be greater than radiation dose limit of 1 mSv/a.     

Investigation of radioactivity in selected drinking water samples from Maryland

The comparator instrumental neutron activation analysis (INAA) method was used for certification of arsenic in Korea Research Institute of Standards and Science (KRISS) reference materials 108-04-001 (Oyster Tissue). The certified value was determined by analyzing one sample of approximately 0.15 g from ten bottles selected by random sampling. Potentially significant sources of uncertainty were taken into consideration using the guideline given by ISO. A complete evaluation of all sources of uncertainty yielded an expanded uncertainty for the mean value of this reference material of 4.7% at approximately 95% level of confidence.     

Associative pH sensitive system

New associative pH sensitive systems composed of a modified dextran bearing 2-carboxycyclohexyl carboxyl groups and neutral (p betaCD) or positively charged (p betaCDN(+))beta-cyclodextrin-co-epichlorhydrin copolymers have been synthesized and their properties were investigated as a function of pH by phase diagrams and viscosimetry. The affinity between the CD cavities and the hydrophobic guests (2-carboxycyclohexyl carboxyl groups) has been studied as a function of pH. The system with the neutral p betaCD shows a pH dependent behavior due to the lowest affinity of the guest at pH above 5 for the cavity. Associative phase separation is produced at low pH whereas soluble complexes occur at higher pH. The opposite trend is observed with the system containing the cationic p betaCDN(+). This behavior is due to the combination of electrostatic and inclusion complex interactions in this system. Addition of salt, by screening the electrostatic interactions, also strongly influences the response of the system.     

Determination of natural radioactivity in public drinking water quality assessment

The determination of ₉₀Sr and the gross particleactivity originating from radium isotopes was performed on water samples atvarious stages of treatment taken from water treatment plants before distributionto the consumers.     

Natural radioactivity of spring water used as spas in Spain

Spring waters used as spas may contain significant amounts of natural radionuclides, so, in some circunstances, a radiation protection issue can arise for the population and/or the spas workers. EU has identified some groups of employees to be exposed to natural radiation in the 1996 Euratom Directive. Among these are workers of thermal spas who may be exposed to high radiation doses due to high radon concentrations in indoor air. In order to evaluate the potencial risk of the spring waters used as spas, gross-α and gross-β activity, ²²⁶Ra and ²²²Rn concentration levels were measured in 82 spas all over the country. Gross-alpha and gross-beta concentrations ranged from LLD to 17 Bq·l⁻¹ and from LLD to 60 Bq·l⁻¹, respectively. ²²⁶Ra concentrations ranged from <4 to 3,660 mBq·l⁻¹. ²²²Rn concentrations ranged from <4 to 1868 Bq·l⁻¹. Correlations between ²²⁶Ra concentrations and gross-α activity were obtained.     

Gamma spectrum analysis for in situ automatic monitoring of radioactivity in seawater

The NaI(Tl) detector has been an important research topic and application in the field of in situ marine radioactive automatic monitoring because of its advantages of low power consumption, low cost, and good efficiency. However, its energy resolution is not high enough. This paper investigated an analytical method: spectrum de-noising, background correction based on the SNIP operator, peak search based on the top-hat transform and peak fitting using Gaussian distribution. Simulation and gamma spectra measured from seawater showed that the established energy spectrum analysis method presents satisfactory automatic analytical ability for identification and quantitatively analysis.

     

Highly sensitive multiresponsive chemosensor for selective detection of Hg2+ in natural water and different monitoring environments

A new chemosensor RF1 that combines a ferrocene unit and a rhodamine block via the linkage of a carbohydrazone binding unit was designed and prepared for the highly selective detection of Hg (2+) in natural water. This chemosensor displays great brightness and fluorescence enhancement following Hg (2+) coordination within the limit of detection for Hg (2+) at 1 parts per billion (ppb). The fluorescence intensities are nearly proportional to the amount of Hg (2+) at the ppb level. It is capable of distinguishing between the safe and the toxic levels of inorganic mercury in drinking water. Hg (2+)-binding also arouses the absorption of the rhodamine moiety in RF1 significantly with the chromogenic detection limit for Hg (2+) at 50 ppb. The conventional UV-vis spectroscopic method thus has the potential to provide the critical information about the mercury hazard assessment for industrial wastewater discharging. The obvious and characteristic color change of the titration solution from colorless to pink upon the addition of Hg (2+) demonstrates that RF1 can be used for "naked-eye" detection of Hg (2+) in water. The Hg (2+) complexation also causes a significant shift of the redox potential about the ferrocene/ferrocenium couple. The electrochemical responses provide the possibility to quantitative analysis of Hg (2+) at the parts per million (ppm) level. Preliminary investigations in natural water samples including seawater and freshwater indicate that RF1 offers a direct and immediate Hg (2+) detection in complex media, pointing out its potential utility in environment monitoring and assessment. The responses of RF1 are Hg (2+) specific, and the chemosensor exhibits high selectivity toward Hg (2+) over other Group 12 metals, alkali, alkaline earth metals, and most of the divalent first-row transition metals. The RF1-Hg (2+) complex is successfully isolated and the Hg (2+)-binding is reversible. The crystal structure and spectral properties of its congener RF2 that contains one ferrocene group and two rhodamine 6G moieties were also investigated for a comparison.     

Rapid, sensitive and direct analysis of exopolysaccharides from biofilm on aluminum surfaces exposed to sea water using MALDI-TOF MS

Biofilm studies have extensive significance since their results can provide insights into the behavior of bacteria on material surfaces when exposed to natural water. This is the first attempt of using matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) for detecting the polysaccharides formed in a complex biofilm consisting of a mixed consortium of marine microbes. MALDI-MS has been applied to directly analyze exopolysaccharides (EPS) in the biofilm formed on aluminum surfaces exposed to seawater. The optimal conditions for MALDI-MS applied to EPS analysis of biofilm have been described. In addition, microbiologically influenced corrosion of aluminum exposed to sea water by a marine fungus was also observed and the fungus identity established using MALDI-MS analysis of EPS. Rapid, sensitive and direct MALDI-MS analysis on biofilm would dramatically speed up and provide new insights into biofilm studies due to its excellent advantages such as simplicity, high sensitivity, high selectivity and high speed. This study introduces a novel, fast, sensitive and selective platform for biofilm study from natural water without the need of tedious culturing steps or complicated sample pretreatment procedures.     

Simple determination of 90Sr in water in environmental radioactivity survey

Derivatives of dodecahydro-closo-dodecaborate(2-) anion were proposed as boron-rich compounds for boron-neutron capture therapy (BNCT) of malignant tumours. Labeling of such tumour-targeting compounds with radioisotopes would facilitate the investigation of their pharmacokinetics and help to optimize patient treatment protocols. Earlier, we reported the feasibility of labeling of closo-dodecaborate(2-) by isotopic exchange in molten acetamide. In this study, the feasibility of low-temperature isotopic exchange in the system [¹²⁵I]iodide - bis(triethylammonium) undecahydro-12-iodo-closo-dodecaborate was investigated. Our attempts to perform the exchange in solvents such as methylene chloride, acetone and acetonitrile in the presence of phase-transfer catalysts were unsuccessful. However, copper mediated exchange in aqueous media was possible. Isotopic exchange of triethylammonium undecahydro-12-iodo-closo-dodecaborate provided a 90-95% labeling yield after heating for three and half hours at 100 °C. This revised version was published online in July 2006 with corrections to the Cover Date.     

On-site monitoring of trace levels of free manganese in sea water via sonoelectroanalysis using a boron-doped diamond electrode

Cathodic stripping voltammetry at a boron-doped diamond electrode utilising an insonated accumulation protocol is shown to be possible for the on-site trace detection of free manganese in seawater samples. No sample pre-treatment is required with the application of ultrasound providing a sensitive and selective protocol for the analysis of manganese. The protocol is used in the evaluation of manganese in seawater samples taken near the site of a former ferromanganese factory in the town Šibenik, Croatia.     

A dipping method for radioactivity measurement in water using plastic scintillator

Journal of Radioanalytical and Nuclear Chemistry - A new dipping method was studied for the measurement of radioactive solution using plastic scintillator sheets and pellets (PSs) and a liquid...