Fiber-optic microsensor for high resolution pCO2 sensing in marine environment

A fast responding fiber-optic microsensor for sensing pCO₂ in marine sediments with high spatial resolution is presented. The tip diameter varies typically between 20 and 50 μm. In order to make the pH-indicator ¶8-hydroxypyrene-1,3,6-trisulfonate soluble in the ethyl cellulose matrix, it was lipophilized with tetraoctylammonium as the counterion [HPTS-(TOA)₄]. The microsensor was tuned to sense very low levels of dissolved carbon dioxide which are typically present in marine systems. The detection limit is 0.04 hPa pCO₂ which corresponds to 60 ppb CO₂ of dissolved carbon dioxide. A soluble Teflon derivative with an extraordinarily high gas permeability was chosen as a protective coating to eliminate interferences by ionic species like chloride or pH. Response times of less than 1 min were observed. The performance of the new microsensor is described with respect to reproducibility of the calibration curves, dynamic range, temperature behavior, long term stability and storage stability. The effect of hydrogen sulfide as an interferent, which is frequently present in anaerobic sediment layers, was studied in detail.     

Characterization of a reservoir-type capillary optical microsensor for pCO(2) measurements

A reservoir type of capillary microsensor for pCO₂ measurements is presented. The sensor is based on the measurement of the fluorescence intensity of the anionic form of the pH indicator 1-hydroxy-3,6,8-pyrenetrisulfonate in the form of its ion pair with a quaternary ammonium base in an ethyl cellulose matrix. The glass capillary containing the reservoir sensor was prepared by immersing the tip of the optical fiber into the sensing agent very close to the sensor tip thus providing a very small volume for the sensing reaction. The purpose of the sensing approach is to regenerate the dye/buffer system by diffusion, which may be poisoned by interfering acids, or bleach by photolysis. The fresh cocktail from the reservoir takes the place of protonated form of the dye. The internal buffer system also makes the protonation-deprotonation equilibria reversible. The distal tip of the internal buffer containing reservoir is coated with a gas-permeable but ion-impermeable teflon membrane. The dynamic range for the detection of pCO₂ is between 1 and 20 hPa, which corresponds to the range of dissolved CO₂ in water. The response time is 15 s and the detection limit is 1 hPa of pCO_2. The recovery performance of this sensor can be improved by means of mechanical adjustment of the sensor tip in a micrometric scale.     

Living cell-based allergen sensing using a high resolution two-dimensional surface plasmon resonance imager

Recently, several papers indicated that the surface plasmon resonance (SPR) technique was available to monitor stimulation responses of mammalian cells adhered on sensor chips. On the other hand, the newly developed two-dimensional SPR (2D-SPR) imager system can obtain 2D-images of local refractive index change on the surface of a gold thin film. From these backgrounds, we expected that the 2D-SPR imager can visualize the individual response of many mammalian cells, simultaneously. Here, we report the observation of an allergenic response of a model mast cell, rat basophilic leukaemia cell (RBL-2H3), by using the high magnification 2D-SPR imaging system after pre-sensitization with 0.1 μg mL(-1) anti-dinitrophenyl immunoglobulin E (anti-DNP IgE). The response of the cells was successfully observed as the increment of the SPR signal (reflection intensity) upon stimulation with 0.1-1000 ng mL(-1) DNP-modified bovine serum albumin (DNP-BSA).     

Luminescent dual sensor for time-resolved imaging of pCO2 and pO2 in aquatic systems

An optical dual sensor for the two-dimensional detection of pCO₂ and pO₂ is described. Tris(tetraoctylammonium)-8-hydroxypyrene-1,3,6-trisulfonate ((TOA)₃HPTS) acting together with the lipophilic buffer tetraoctylammonium hydrogen carbonate ((TOA)HCO₃) as pCO₂-sensing system along with the oxygen indicator tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) bis(3-(trimethylsilyl)-1-propanesulfonate) (Ru(dpp)₃TMS₂) are incorporated into a single layer ethyl cellulose matrix. A second layer of black silicone rubber served as an optical isolation. The two indicators were simultaneously excited with a 460-nm LED, and a fast-gateable CCD camera was used as the detector. The time-gated imaging scheme enables the mapping of pCO₂ and pO₂ within one measurement, where images in three different time windows during and after a series of square-shaped excitation pulses are recorded. A numerical evaluation method for the resolution of the single parameter maps from these three overall images is described. The response of the sensor has been optimized for use in aquatic systems.     

A high precision, fast response, and low power consumption in situ optical fiber chemical pCO2 sensor

A sensor system suitable for monitoring changes in partial pressure of carbon dioxide (pCO(2)) in surface seawater or in the atmosphere has been developed. Surface seawater samples are pumped into a PVC tube enclosing an inner Teflon AF tube, which served as a long pathlength gas-permeable liquid-core waveguide for spectrophotometry. The Teflon cell contains a pH-sensitive indicator-buffer solution consisting of bromothymol blue (BTB) and sodium carbonate. Carbon dioxide in the sample diffuses into the indicator-buffer solution to reach equilibrium, resulting in pH changes, which are detected by changes in the absorbance of BTB at wavelengths of 620 and 434 nm. The pCO(2) in the sample is then derived from the pH change. The sensor has a response time of 2 min at the 95% equilibrium value and a measurement precision of 0.26-0.37% in the range 200-800 microatm pCO(2). This chemical sensor takes advantage of a combination of long pathlength, multiple wavelength detection, indicator solution renewal, and in situ automatic control technology, and has the feature of low power consumption (the average being approximately 4 W with a peak of approximately 8 W).     

Multipurpose cold injector for high resolution gas chromatography

The multipurpose cold injector described in this paper represents a solution for an universal sampling system for high resolution gas chromatography. The system is modular and is built around the Carlo Erba cold on-column injector provided with secondary cooling. An auxiliary module, easily fixable on the bottom of the on-column injector, creates a temperature programmable vaporizing chamber making the system also suitable for cold split-splitless injections or solvent venting prior to the sample transfer into the capillary. The system can be operated manually or in a fully automatic mode using the auto-sampler for cold on-column injections. The experimental data illustrate its benefits and limitations.     

RhIr@MoS2 nanohybrids based disposable microsensor for the point-of-care testing of NADH in real human serum

Dihydronicotinamide adenine dinucleotide (NADH) is an important enzyme in all living cells, which is found to be abnormally expressed in cancer cells. Since it is redox-active, an electrochemical detection method would be suitable for monitoring its concentration in biological fluids. Here we present a strategy for specific determination of NADH in real human serum by using RhIr@MoS₂ nanohybrids based microsensor. To implement the protocol, RhIr nanocrysrals are in-situ grown onto MoS₂ interlayers forming a nanohybrid structure (RhIr@MoS₂). After being locally deposited on an electrochemical microsensor, it could be used for the analysis of NADH. The developed RhIr@MoS₂ nanohybrids based microsensor possesses the ability for analyzing NADH at the applied potential of 0.07 V (much lower than most reported values). The detection limit is evaluated as low as 1 nmol/L even in bovine serum albumin (BSA) media. In addition, the sampling analysis of human serum from cancer patients and health controls shows that the microsensor displays good diagnostic sensitivity and specificity, illustrating that this developed detection technique is a relatively accurate method for measuring NADH in biological fluids. The proposed electrochemical microsensor assay also owns the benefits of convenience, disposable and easy processing, which make it a great possibility for future point-of-care cancer diagnosis.     

A high resolution GC-analysis method for determination of C2-C10 hydrocarbons in air samples

An analytical method for the determination of non-methane hydrocarbons (NMHC) in air was developed using simultaneously pressure and temperature programmed gas chromatography (GC) on a capillary column. The separation of C2-C10 hydrocarbons was performed in a single GC-run using a fused silica capillary column (FSCC) with a chemically bonded non-polar stationary phase (CP-Sil-5-CB). A combination of on-column cryofocusing and GC reinjection provided baseline separation of C2 hydrocarbons at subambient initial temperature (?40°C). The cryofocusing was performed on the column head immersed in liquid nitrogen. Quantitative retention of all C2-C10 hydrocarbons was achieved only when a temperature gradient is created along the cooled column section. The focused components are eluted from the column head without supplementary heating by removing the coolant. To eliminate matrix effects, the enrichment procedure was designed to remove CO₂ and H₂O. The detection limit was found to be 2.0 × 10^?12 g propane.     

Chromogenic betaine lariates for highly selective calcium ion sensing in aqueous environment

This paper describes the design, synthesis, and the characterization of the two new chromogenic crown ethers 2,2′-[1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diylbis(methylene)]bis[4-[(1-methyl-4-(1H)-pyridinylidene)ethylidene]-2,5-cyclohexadien-1-one (KBC-001) and the lipophilic derivative 2,2′-[1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diylbis(methylene)]bis[4-[(1-dodecyl-4-(1H)-pyridinylidene)ethylidene]-2,5-cyclohexadien-1-one (KBC-002). A merocyanine dye that forms a betainic structure upon intramolecular charge transfer and shows solvent polarity dependent spectral sensitivity was selected as the chromophore system to develop the new chromoionophores. This approach allows the design of overall electrically neutral ligands bearing charged groups without the need of external counter ions. A proton ionizable group in the dye moiety acts as a charged ion-binding site and is an integral part of a lariat crown ether ionophore. A chromoionophore for calcium ion sensing has been developed, which combines the size-selective binding character of a crown ether with strong electrostatic attraction between the positively charged calcium ion and two negatively charged lariat side arms in the overall neutral compound. This water-soluble dye selectively responds to the presence of calcium ions in water at pH 8.5 with a dynamic response range between 10 μM and 10 mM. The binding event can be monitored both by absorption spectrometry and by fluorescence spectrometry. No cross-sensitivity was found for the physiologically important cations Mg²⁺, Li⁺, Na⁺, and K⁺ up to concentrations of 0.1 M under the same experimental conditions. In contrast to the water-soluble reagent KBC-001, the lipophilized derivative KBC-002 having two long alkyl chains was successfully applied to ion-exchange type optode membranes made from plasticized poly(vinyl chloride) (PVC). The dynamic response range of the optode at pH 9.0 was between 10 μM and 10 mM while retaining the high calcium selectivity.     

Benefits of high resolution IC-ICP-MS for the routine analysis of inorganic and organic arsenic species in food products of marine and terrestrial origin

A recently developed and validated method for simultaneous determination of 17 inorganic and organic arsenic compounds in marine biota has been successfully applied to routine analysis of different food products, including fish, shellfish, edible algae, rice, and other types of grain. During one year, approximately 250 food samples were analyzed, mostly fish and rice. Long-term stability and robustness of the system was observed and reproducible results for certified reference materials were ensured by means of control charts. The separation was performed by ion-pair chromatography on an anion-exchange column to separate anionic, neutral, and cationic arsenic species in one chromatographic run. Hyphenation to ICP–MS allowed element-specific and sensitive detection of the different arsenic species with a detection limit as low as 8 ng As L^–1 in the sample extract, which is equivalent to 2 ng As g^–1 in the original sample. Special emphasis was laid on the analysis of marine algae and rice samples. These food types can contain elevated levels of the very toxic inorganic arsenic species (up to 90% in rice) and therefore are the focus of interest in the food industry. In marine algae, inorganic arsenic was mainly present as arsenate whereas in rice arsenite predominated.     

Studies of transuranics in an arctic marine environment

Since the accidental loss of four nuclear weapons by a B-52 at Thule Airbase, Greenland in 1968, the marine environment at Thule has showed enhanced levels of Pu and Am. Most of the activity is confined to the benthic environment within a distance of 50 km from the crash site of the B-52. Samplings of sediments, benthos, seaplants, fish, and water have been carried out in 1968, 1970, 1974, 1979, and in 1984. The study presented herein intends to answer the following questions: What is the mean residence time of these transuranics in the benthic communities? Do Pu and Am behave differently in the environment?     

An improved model for predicting hydrate phase equilibrium in marine sediment environment

Based on the models of hydrate phase equilibrium in bulk water and porous media, an improved model was proposed to predict the methane hydrate equilibrium in marine sediment environment. In the suggested model, mechanical equilibrium of force between the interfaces in hydrate-liquid-vapor system was considered. When electrolyte was present in pore water, interfacial energy between hydrate and liquid was corrected by an equation that is expressed as the function of temperature and electrolyte concentration. The activity of water is calculated based on the Pitzer model and the interfacial energy between liquid and gas is solved using the Li method. The prediction results show good agreement with the experimental data. By comparison with other models, it is proved that this model can improve the accuracy for predicting hydrate phase equilibrium in marine sediment environment.     

Organometallics in the nearshore marine environment of Australia

This review draws together published information on the occurrence and biogeochemical cycling of selenium, arsenic and tin in the nearshore marine environment of Australia. The selenium content of marine organisms is well documented but little information is available on the selenium content of waters and sediments. The speciation of selenium in organisms, water and sediments is unknown although it appears that selenium is associated with proteins. The occurrence and speciation of arsenic in marine organisms has been extensively studied, with arsonobetaine being isolated as the probable end-product of arsenic metabolism in marine food chains. However, organisms can produce other organoarsenic compounds, e.g. trimethylarsine oxide, which may be metabolized to toxic end-products. Little is known about the occurrence and speciation of arsenic in waters and sediments. Arsenic(V) is dominant in oxygenated waters, with appreciable quantities of arsenic(III) in some deoxygenated waters. There are few data for tin in water, sediments or organisms and no data on naturally occurring tin species. Tributyltin has been measured in water, sediment and organisms from areas affected by boating activity.     

Semi-automated methods for the determination of particulate phosphorus in the marine environment

Summary After filtration of sea water through glass fiber filters, the filters with the residue are digested by heating with sulphuric acid and hydrogen peroxide. The following determination of phosphate is based on the formation of a phosphomolybdenum complex. It has been modified in such a way that the phosphorus content of the samples can be determined with a continuous-flow system with the TechniconAutoAnalyzer direct after digestion. Two methods are described for different sensitivities of 0.1–10mol P · l^–1.

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Halbautomatische Methoden zur Bestimmung von partikulärem Phosphor in Meerwasser

Zusammenfassung Der Rückstand bei Filtration von Meerwasser durch Glasfaserfilter wird mit Schwefelsäure und Wasserstoffperoxid aufgeschlossen. Die anschließende Phosphatbestimmung basiert auf der Bildung eines Phosphormolybdän-Komplexes. Sie wurde modifiziert, so daß der Phosphor-Gehalt der Proben sofort nach Aufschluß mit dem Durchflußsystem des Technicon-AutoAnalyzers bestimmt werden kann. Zwei Methoden mit unterschiedlicher Empfindlichkeit (von 0,1–10mol P · l^–1) werden beschrieben.

     

Traveling wave magnetophoresis for high resolution chip based separations

A new mode of magnetophoresis is described that is capable of separating micron-sized superparamagnetic beads from complex mixtures with high sensitivity to their size and magnetic moment. This separation technique employs a translating periodic potential energy landscape to transport magnetic beads horizontally across a substrate. The potential energy landscape is created by superimposing an external, rotating magnetic field on top of the local fixed magnetic field distribution near a periodic arrangement of micro-magnets. At low driving frequencies of the external field rotation, the beads become locked into the potential energy landscape and move at the same velocity as the traveling magnetic field wave. At frequencies above a critical threshold, defined by the bead's hydrodynamic drag and magnetic moment, the motion of a specific population of magnetic beads becomes uncoupled from the potential energy landscape and its magnetophoretic mobility is dramatically reduced. By exploiting this frequency dependence, highly efficient separation of magnetic beads has been achieved, based on fractional differences in bead diameter and/or their specific attachment to two microorganisms, i.e., B. globigii and S. cerevisiae.     

Algorithms for automatic interpretation of high resolution mass spectra

Automated interpretation of high-resolution mass spectra in a reliable and efficient manner represents a highly challenging computational problem. This work aims at developing methods for reducing a high-resolution mass spectrum into its monoisotopic peak list, and automatically assigning observed masses to known fragment ion masses if the protein sequence is available. The methods are compiled into a suite of data reduction algorithms which is called MasSPIKE (Mass Spectrum Interpretation and Kernel Extraction). MasSPIKE includes modules for modeling noise across the spectrum, isotopic cluster identification, charge state determination, separation of overlapping isotopic distributions, picking isotopic peaks, aligning experimental and theoretical isotopic distributions for estimating a monoisotopic peak's location, generating the monoisotopic mass list, and assigning the observed monoisotopic masses to possible protein fragments. The method is tested against a complex top-down spectrum of bovine carbonic anhydrase. Results of each of the individual modules are compared with previously published work.     

A simple computer program for high resolution gamma-ray spectra

A computer program is presented, which locates peaks in high-resolution γ-ray spectra and determines their content. The program has been written in Basic; ‘translations’ have been made into Fortran and Algol. For detailed information the reader is referred to the original TNO Report CL 69/137.