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meso-Bromosubstituted indodicarbocyanine dyes produce dimeric molecules, together with the debrominated species, under acid catalysis. The relationship between the dimerization and hydrodebromination routes depends on the aryl substitution of the dyes. A possible reaction mechanism is also proposed.

The analysis of soluble reactive phosphate (SRP) in water is key to control water quality. In order to continuous monitor orthophosphate content in water during treatment processes and in the effluents of wastewater treatment plants, conventional procedures, usually performed in a laboratory, must be adapted. This means pursuing efforts on miniaturizing systems to operate in situ and automating analytical methods to work on-line. The design, construction and evaluation of an automatic and low cost cyclic olefin copolymer (COC)-based spectrophotometric microanalyzer, capable of operating in unattended conditions, is presented to monitor soluble reactive phosphorous, as orthophosphate ion, in wastewater samples coming from sewage treatment plants. The microsystem, constructed by CNC micromilling and using a multilayer approach, integrates microfluidics to carry out the phosphomolybdenum blue (PMB) reaction and an optical flow-cell for the spectrophotometric orthophosphate determination in a single polymeric substrate smaller than a credit card. It is connected to a compact optical detection system composed by a LED emitting at 660 nm and a PIN-photodiode, both integrated in a PCB. Flow management is automatically performed by programmed microvalves and micropumps, which control autocalibration processes and allow unattended operation. Analytical features after the optimization of the microfluidic platform and the chemical and the hydrodynamic variables, were a linear range from 0.09 to 32 mg L−1 P and a detection limit of 0.03 mg L−1 P with a sampling rate of 24 samples h−1, demonstrating the microanalyzer suitability for SRP monitoring in water. Moreover, real samples were analyzed obtaining promising results.

The design, construction and evaluation of a low cost, cyclic olefin copolymer (COC)-based continuous flow microanalyzer, with optical detection, to monitor carbon dioxide in bottled wines and beers as well as in fermentation processes, is presented. The microsystem, constructed by computer numerically controlled (CNC) micromilling and using a multilayer approach, integrates microfluidics, gas-diffusion module and an optical flow-cell in a single polymeric substrate. Its size is slightly bigger than a credit card, exactly 45 × 60 × 4 mm in the microfluidic and diffusion module zone and 22.5 × 40 × 3 mm in the flow-cell zone. The gas-diffusion module is based on a hydrophobic polyvinylidene fluoride (PVDF) membrane, which allows the transfer of the carbon dioxide present in the sample to a bromothymol blue (BTB) pH-sensitive acceptor solution, where the color change is measured optically. The detection system consisted of a LED with an emission peak at 607 nm and a photodiode integrated in a printed circuit board (PCB). The obtained analytical features after the optimization of the microfluidic platform and hydrodynamic variables are a linear range from 255 to 10000 mg L−1 of CO2 and a detection limit of 83 mg L−1 with a sampling rate of 30 samples h−1.

The progress made in recent years in the area of micro total analysis system (μ-TAS) has allowed the development of analytical tools for determination and measurement of elements and compounds that previously required bench laboratory equipment for such purposes. μ-TAS provides a high degree of sensitivity and they are simple and affordable. This work details a process by which classical colorimetric methodologies used in analysis have been adapted from discontinuous to continuous flow systems, for determination of cobalt in aqueous solutions in real time. The purpose of this adaptation is the subsequent system miniaturization using low temperature co-fired ceramics (LTCC). The adapted methodology for the colorimetric determination of cobalt uses 3-Hydroxy-4-nitroso-2,7-naphtalene disulfonic acid disodium salt or nitroso-R salt (NRS) as the main reagent, in an environment of acetate and sodium citrate which favors the reaction. The carrier solution is prepared with sulfuric acid. The system encompasses a microfluidic structure in LTCC, a peristaltic pump to maintain the continuous flow, a six-way valve for sample injection, and an issuer of light of 540 nm based on a multiled. Using the integrated circuit TCS3414, the signal is sent to the computer wirelessly through zigbee protocol, and at the end a LabVIEW-based application shows the absorbance for a range of concentrations between 0.5 and 10 mg/L.

A boron trifluoride–methanol complex demonstrated remarkable deprotection selectivity against commonly used amino-protecting groups in the deacetylation of acetanilides and high sensitivity to the steric hindrance of substrates. The scope and limitations of the reaction were explored.

The synthesis of a set of open-chain bis-aminosubstituted cyanine dyes as well as others with cyclic fragments in the polymethine chain is presented. These dyes are suitable for the development of polymeric compositions with variable optical characteristics as they can be covalently incorporated into the polymer.

An optical microfluidic system based on the use of modified gold nanoparticles for monitoring Hg(II) is presented. The system is based on the specific recognition of the heavy metal by a new synthesized ionophore based on a modified thiourea, which is attached to the gold nanoparticles. This interaction generates a change on the gold Surface Plasmon Resonance (SPR) band. The sensitivity and selectivity of the procedure is firstly studied in batch. The obtained results demonstrate the mercury selective response over the different tested ions that can be found in environmental water samples. Due to the remarkable unusual rapid signal change observed during the interaction of the metal and the modified gold nanoparticles, the reaction can be easily performed in a microfluidic system. Results obtained by using the microfluidic system revealed improved analytical features compared to batch experiments such as a lower detection limit (11 ppb), higher sensitivity and faster analysis time, all this with an easy and automated procedure. Therefore, the approach has shown great potential for designing low cost instrumentation for automatic in-field discrete or continuous measurements of Hg(II).

This work describes the development of a fully integrated Low Temperature Co-fired Ceramic (LTCC) microreactor for the synthesis of carbon dots (CDots). The microreactor integrates fluidics, a heating resistor and an optical window for fluorescence imaging of the reaction progress in a monolithic, all ceramic device, ensuring homogeneous surface chemistry and physical properties. A pool of different CDots was synthesized at high temperature and pressure using a hydrothermal method, demonstrating the robustness of the microreactor. The synthesis was monitored by following the photoluminescence of the produced CDots, and the reaction conditions were optimized according to their Quantum Yield (QY) and the flow pattern inside the microchannel. The obtained CDots exhibited blue photoluminescence upon irradiation with UV light with QYs of up to 0.77. The CDots were screened as metal nanoprobes and bioimaging contrast agents.

The construction and evaluation of a Low Temperature Co-fired Ceramics (LTCC)-based continuous flow potentiometric microanalyzer prototype to simultaneously monitor the presence of two ions (potassium and nitrate) in samples from the water recycling process for future manned space missions is presented. The microsystem integrates microfluidics and the detection system in a single substrate and it is smaller than a credit card. The detection system is based on two ion-selective electrodes (ISEs), which are built using all-solid state nitrate and potassium polymeric membranes, and a screen-printed Ag/AgCl reference electrode. The obtained analytical features after the optimization of the microfluidic design and hydrodynamics are a linear range from 10 to 1000 mg L−1 and from 1.9 to 155 mg L−1 and a detection limit of 9.56 mg L−1 and 0.81 mg L−1 for nitrate and potassium ions respectively.

Monitoring organic environmental contaminants is of crucial importance to ensure public health. This requires simple, portable and robust devices to carry out on-site analysis. For this purpose, a low-temperature co-fired ceramics (LTCC) microfluidic potentiometric device (LTCC/ POT) was developed for the first time for an organic compound: sulfamethoxazole (SMX). Sensory materials relied on newly designed plastic antibodies. Sol–gel, self-assembling monolayer and molecular-imprinting techniques were merged for this purpose. Silica beads were amine-modified and linked to SMX via glutaraldehyde modification. Condensation polymerization was conducted around SMX to fill the vacant spaces. SMX was removed after, leaving behind imprinted sites of complementary shape. The obtained particles were used as ionophores in plasticized PVC membranes. The most suitable membrane composition was selected in steady-state assays. Its suitability to flow analysis was verified in flow-injection studies with regular tubular electrodes. The LTCC/ POT device integrated a bidimensional mixer, an embedded reference electrode based on Ag/AgCl and an Ag-based contact screen-printed under a micromachined cavity of 600 m depth. The sensing membranes were deposited over this contact and acted as indicating electrodes. Under optimum conditions, the SMX sensor displayed slopes of about −58.7 mV/decade in a range from 12.7 to 250 g/mL, providing a detection limit of 3.85 g/mL and a sampling throughput of 36 samples/h with a reagent consumption of 3.3 mL per sample. The system was adjusted later to multiple analyte detection by including a second potentiomet-ric cell on the LTCC/ POT device. No additional reference electrode was required. This concept was applied to Trimethoprim (TMP), always administered concomitantly with sulphonamide drugs, and tested in fish-farming waters. The biparametric microanalyzer displayed Nernstian behaviour, with aver-age slopes −54.7 (SMX) and +57.8 (TMP) mV/ decade. To demonstrate the microanalyzer capabilities for real applications, it was successfully applied to single and simultaneous determination of SMX and TMP in aquaculture waters. The authors acknowledge the financial support from FCT, Fundacão para a Ciência e Tecnologia/FEDER (project PTDC/AGR-AAM/68359/2006). Oneofus (Almeida SAA) is grateful to FCT for the PhD Grant (SFRH/BD/42509/2007). Publicado

Resumen Objetivos Estudiar los efectos del tratamiento de los pacientes con fractura de cadera en una unidad ortogeriatrica conjunta entre los servicios de traumatologia y geriatria comparados con el tratamiento hospitalario habitual y analizar las diferencias de costes entre ambos sistemas de asistencia. Material y metodos Estudio prospectivo cuasi-experimental de intervencion, aleatorizado, en 506 pacientes ingresados en un hospital terciario con el diagnostico de fractura de cadera osteoporotica. El sistema habitual de tratamiento fue el ingreso a cargo de traumatologia con interconsulta a geriatria (tipo IC) y el sistema a estudio consistio en el ingreso en una unidad ortogeriatrica (UOG) para el tratamiento conjunto integrado entre los especialistas en traumatologia y geriatria. Este incluyo la designacion de un interlocutor unico por cada servicio, seguimiento por la enfermera de ortogeriatria, valoracion geriatrica precoz, atencion clinica diaria coordinada, pase de visita conjunto semanal y planificacion coordinada de la programacion quirurgica, del inicio de la deambulacion y del destino y momento del alta. Resultados Se incluyo a 255 pacientes consecutivos ingresados en la UOG y 251 tratados simultaneamente mediante IC. No existieron diferencias, salvo por una edad ligeramente inferior en el grupo de UOG, en las caracteristicas previas ni en la tasa de intervencion quirurgica de ambos grupos. En los pacientes de la UOG fue mas frecuente recibir rehabilitacion en la fase aguda, ser capaz de caminar al alta y ser derivado a unidades de recuperacion funcional (todas con p Conclusiones La UOG es un nivel asistencial que aporta mejoras en la evolucion funcional de los pacientes y una reduccion total de estancias hospitalarias. En base a ello reduce los costes de asistencia. Estos resultados hacen recomendable este sistema de atencion a los pacientes con fractura de cadera en fase aguda.

A novel fluorescence dip-probe POF (Polymer Optical Fiber) sensor that allows performing in situ chemical determinations has been fabricated. The dip-probe sensor design has been optimized by simulations in order to improve the fluorescence collection. To demonstrate its possibilities, it has been chemically activated with a lead-selective plasticized PVC (polyvinylchloride) membrane containing a new synthesized suitable fluoroionophore and a commercial lead ionophore. The analytical response of the dip-probe sensor has been characterized and it shows a fully reversible response with a sensitivity of −35.10 mV/dec C and a Pb2+ detection limit of 7 × 10−6 M, which can be appropriate for monitoring contamination episodes. No significant interferences with other metal ions have been found. The device has been finally tested to determine the lead content in contaminated natural samples with promising results.

A miniaturized and robust optical fluorosensor, designed as a portable instrumentation for the in situ analysis of ions in water samples by using optodes has been constructed with low cost discrete optical components. The chemical recognition element of the device consists of a plasticized PVC-based fluorescent optode, which includes a new hexamethine–hemicyanine dye as a fluorophore. The signal can be attributed to a certain analyte depending on the ionophore employed. In this work, a commercial potassium ionophore (valinomycin) has been used to formulate a model membrane selective to potassium. The sensor has been fully characterized using a simple flow injection analysis (FIA) system and analytical parameters such as sensitivity (0.71 mV dec −1 ), limit of detection (2.2 × 10 −5 M K + ), repeatability (R.S.D. = 4.2%), reproducibility, lifetime and ionic interferences have been determined. The developed miniaturized system has been applied to the potassium concentration determination in spiked tap water samples. The obtained results have been compared to those acquired by the ICP-OES reference method and the suitability of the experimental setup for the determination of ions in water samples by the miniaturized fluorescence proposal has been demonstrated.

New norcyanine dyes were characterised for their use as long wavelength chromoionophores in optodes. Different membrane compositions were formulated for pH determination in water and their response in terms of sensitivity, linear range, response time and reversibility was examined with the aim to apply them in planar optochemical sensors. Their absorbance maxima are located in the NIR region (785–830 nm), which is very appropriate for applications using common low cost telecommunication components. The characterised optodes showed good analytical features. Hence, fully reversible, reproducible, fast, and sensitive bulk optodes were obtained. The photostability of dyes in the plasticised matrices and their tendency to leach from the membrane phase were also evaluated at different conditions.

New nor-based cyanine dyes have been characterised for their use as long wavelength chromoionophores in optochemical sensors. Since common quaternary cyanine dyes present optimum spectroscopic characteristics but with high basicities, three kinds of molecules (nortricarbocyanine dyes, norindosquarocyanine dyes and norindocrococyanine dyes), based on an acid–base equilibrium, where the proton attached to the indolic nitrogen is involved, have been designed, expecting to obtain lower p K a values. For comparison purposes, every type of dye has been synthesised with a different central group and molecules with the same heterocyclic substituents have been proposed. The acid forms of the norcyanine dyes present sharp and intense absorption bands from the far visible to the NIR region, with absorption maxima between 648 and 821 nm, allowing the use of non-expensive semiconductor based optical sources and detectors. Relationships between the optical properties, the basicity and the molecular structure are discussed.

Some new symmetrical and unsymmetrical near-infrared absorbing acidochromic dyes are synthesised by a simple one-step reaction. Such indicators belong to the ketocyanine dyes type and as well as their full characterisation as the relationship between their structure and optical properties are discussed. They are mainly tested for their future application as pH or solvent polarity sensors. The absorption maxima of the long-wavelength absorbing acidic form span the region from 715 to 750 nm, nearly matching the emission wavelength of the 780 nm laser diode. p K a values in ethanol cover the range between 1.7 and 4.3, and reversible absorption spectra are observed while pH is changed forth and back. As merocyanine dyes, the synthesised ketocyanine dyes show a positive solvatochromism. Since one of the requirements for a solvatochromic molecule to be useful to establish a solvent polarity scale is its stability, the photostability of the dyes is tested in ethanolic solution as well.

Twenty ketocyanine dyes are evaluated as potential pH fluoroionophores to be used in the development of new integrated waveguide fluorescence optodes (IWFOs). Its fluorescence characterization, as well as the pH response is first undertaken in ethanolic solution and then in plasticized PVC membranes with a conventional spectrofluorimeter. Analytical parameters such as basicity, reversibility, leaching and calibration curves are determined in both media and finally, photostability is also measured. Besides, some photophysical fluorescent parameters, such as the emission wavelength, are evaluated for both species, the acidic and the basic form, and quantum yields are calculated in ethanolic solution. Ketocyanine dyes have demonstrated their suitability for being used as acidochromic fluoroionophores in bulk optodes for the development of new IWFOs. They exhibit high fluorescence intensities in the far-visible region, an adequate photostability and an optimum pH response.

A set of near-infrared absorbing tricarbocyanine dyes has been synthesised and characterised for their future application as chromoionophores in optochemical sensors. Their absorption maxima are localised in the NIR region, where matrix interferences are minimal and the use of suitable and inexpensive optical communication components gives great advantages. The acid form of the synthesised dyes in pure ethanol spans the region from 675 to 815 nm and the molar absorptivities are up to 3.3 × 10 5 l/mol cm. The calculated p K a values in ethanol lie between 11.4 and more than 13. The effect of the introduction of substituents on the p K a values and on the spectroscopic characteristics of the dyes is also discussed. Moreover, pH-sensitive aggregation processes have been observed in aqueous solution.

Acyclic Pd–diaminocarbene complex showed high catalytic activity in Suzuki arylation of meso-chlorine-substituted tricarboindocyanine dyes. Arylated dyes were obtained in 57–83% yields in the presence of 5 × 10−4 equiv of catalyst.

The continuous monitoring of processes in the food industry, and in particular in wine production, holds great interest as it can help to increase the quality of the goods produced and also the efficiency of the production process. One process that is feasible to control is the stabilisation of wine by means of ion-exchange resins. The use of this technique is of great promise since it allows continuous wine treatment and also on-line monitoring systems can be applied to determine the saturation of the resin in addition to the fraction of wine requiring stabilisation. The development of a pH, calcium and potassium analyser for on-line monitoring of wine in a continuous flow system is reported here. The potentiometric sensors used are ion-selective field-effect transistors (ISFETs). The stability of these sensors in hydro-alcoholic media was studied obtaining a sensitivity of 56 mV per decade for the pH ISFET and sensitivities of −26 mV per decade and −50 mV per decade for calcium and potassium sensors, respectively. The long-term stability of pH-ISFETs was 7 and 4 months for cation sensors. Results obtained in the continuous flow system with wine samples demonstrated that the proposed system is capable to detect the saturation point of the ion-exchange resin in wine stabilisation process and also to determine the ratio of wine required to stabilise it.

The present report describes the development of a thick-film sensor with intended applications for soil analysis. A probe incorporates three sensors, each at a different depth and featuring a copper plate as the reference electrode. In addition, the probe also contains all necessary instrumentation required for processing the sensor signal and to transmit it via radio. The developed sensors were calibrated in situ using two different soil compositions by adding standard solutions. Results show a quasi-Nernstian response in soil, in response to the addition of fertilisers. Extracts of soil samples analysed by the Kjeldahl method were compared with results from the probe. This comparison confirms that the sensors are capable or measuring chemical parameters in situ in an automated fashion.

In this paper, the universal determination of non-ionic surfactants (NIS) of the polyethoxylate type is attempted using flow-injection potentiometry. Two systems are proposed which use specifically developed tubular flow-through ion selective electrodes (ISEs). These are sensitive to NIS with an hydrophilic chain between 6 and 18 ethoxylate units, which are predominant species in the environment. An on-line pre-concentration system is designed with the aim of a possible application for the unattended monitoring of NIS in surface waters. This on-line pre-concentration is achieved by employing a column packed with a commercial solid phase extraction (SPE) sorbent for the enrichment and purification of the target analytes. The procedure outlined improves the detection limit of a direct system, decreasing it from 1×10 −4 to 3×10 −6 M by use of a pre-concentration volume of 40.0 ml and 200 μl of 75% acetonitrile in water as the eluent. Precision was estimated as 4% relative standard deviation (R.S.D.) ( n =25) for a 1×10 −6 M (0.7 ppm) nonylphenol polyethoxylate with 12 ethoxylate units when 10.0 ml of sample are pre-concentrated. Finally, the on-line pre-concentration system is applied for the total NIS determination in environmental samples from Llobregat river basin of Barcelona area (NE Spain).

A method is described for the conductimetric determination of CO 2 . The proposed system was constructed with a pervaporator chamber coupled to a flow system comprised of a six-way solenoid valve, a conductivity cell, a conductivimeter and a PC microcomputer for data acquisition and external controls. An amount of 2 g of dry soil samples were directly weighted in the donor compartment of the pervaporation chamber. The CO 2 was determined from an analytical curve within 5.0 x 10 -3 -5.0 x 10 -2 mol kg -1 CaCO 3 . This curve was constructed with the matrix matching approach and presented a linear regression of y = 13.58 + 584.77r (r = 0.9962). Soils with different lime amounts were analyzed by the proposed methodology and with the official method, that uses the calcium difference between the total, extracted with HCl 1 mol l -1 and exchangeable, extracted with the KCl 1 mol l -1 After paired t-test application, no significant difference between the methods was found at the 95% probability level. The proposed method presented sampling rate of 17 h -1 , detection limit of 8.0 x 10 -4 mol kg -1 CaCO 3 , and R.S.D. < 3%. The use of the pervaporator allowed the in situ soil pretreatment for the residual lime determination.

A flow injection system for the determination of polyethoxylated nonionic surfactants is described. Potentiometric detection based on tubular flow-through ion-selective electrodes (ISEs) sensitive to this type of surfactants was used. As ion-exchanger, the plasticised PVC membrane incorporates the ion pair between the adduct of a nonionic surfactant with barium and tetraphenylborate. Two different membrane compositions were studied. They differed in the nonionic surfactant used in the ion-exchanger preparation: either nonylphenoxypolyethoxylate with 5 (Ig5) or 12 (Ig12) ethylene oxide units were used. Experimental results showed that the use of Ig5 membrane with a barium salt adjusting solution allowed lower detection limits, while Ig12 ISE with potassium salt solution presented enhanced sensitivity. Both FI systems were evaluated employing three different polyethoxylate standards, which could be determined down to ca. 10 −5 M. Precision was 3% R.S.D. for n = 50 using repetitive injections of a 3 × 10 −4 M Ig12 standard. Preliminary tests of an on-line preconcentration flow system employing the developed sensing devices are also shown. © 2001 Elsevier Science B.V. All rights reserved.

Standard methods to measure nutrient levels in soil are complex and time consuming due to the extraction and pre-treatment processes involved. Besides, the instrumentation used for these measurements is also expensive. Therefore, the use of chemical sensors warrants investigation since they can be placed directly in the soil and results can be provided in real or quasi-real time at a moderate cost. The control of nutrients with sensors will permit an optimisation of irrigation and fertilisation management systems and thus will be useful for reducing the environmental impact caused by the runoff of nutrients into surface and ground waters. In this work, the use of chemical sensors based on ion sensitive field effect transistors (ISFETs) for soil analysis is proposed. These devices are fabricated with microelectronic technology – providing some important advantages such as robustness, small size, low output impedance and mass production. Fabrication of pH, Ca2+, K+ and NO3− ISFETs with photocurable polymeric membranes and their evaluation in aqueous solutions is reported. Studies of their response in horticulture soils and comparison with standard methods have been performed. The results confirm the feasibility of ISFET based sensors for in-soil monitoring and the promising future applications they have.

The fabrication of ion-sensitive electrochemical sensors for calcium is described in the present work. The membrane uses a photocurable polymer based on aliphatic diacrylated polyurethane. The use of photocurable polymers as the support matrix instead of PVC simplifies the preparation and the casting of the developed ion-sensitive membranes. Additionally, these polymers are compatible with the photolithographic fabrication techniques used in the microelectronics industry. This aspect permits the patterning of membranes on wafer level for semiconductor based sensors thus the automatization of the whole sensor fabrication. These polymer matrices show also better adhesion to silanised semiconductor surfaces, such as the gate surfaces of ion selective field effect transistors (ISFETs). Membranes sensitive to calcium ions were optimised according the type of plasticizer and the polymer/plasticizer ratio. Ion selective electrodes (ISEs) with a solid internal reference and ISFETs were used to evaluate the membrane. The resulting sensors were functional for periods of more than 8 months and the resulting sensitivities were quasi-Nernstian (26–27 mV/dec) in a range of 5×10 −6 –8×10 −2 M. These sensors were used to measure calcium activity in water samples extracted from agricultural soils. The results were compared with those yielded by standard methods, finding a good correlation between the two analytical procedures.

A new approach for developing absorbance optochemical sensors is presented in this paper. It is based on a planar microoptic circuit where an optochemically active membrane, which responds selectively to a compound, is deposited in the device, yielding a part of the guiding planar structure. Light is propagated through the membrane, which changes its spectral absorption properties and controls the selectivity of the measurements by means of several immobilised compounds. This way, high sensitivity of the device can be easily obtained due to relatively long light paths through the membrane, and low response times can be achieved as the analyte diffusion occurs perpendicularly to the light path and through a thin membrane. Experimental results on measurements of the concentration of a specific ion in solution using the fabricated sensors are also presented.

A colorimetric flow injection-system for the determination of Cu(II) in waters based on complexation reaction with 4-(2-pyridylazo)-resorcinol, usually termed PAR, is described. Performing measurements in 0.25 mol l −1 HNO 3 medium allowed improved selectivity of the analytical method. The lack of sensitivity deriving from the low complex absorption under acidic conditions was balanced by the insertion of an immobilised poly(ethylenimine) (PEI) column where Cu(II) pre-concentration in neutral media occurs. Using sample volumes ranging from 2 to 4 ml, sampling rates of 24 and 12 samples h −1 within a detection limit of 25 and 13 μg l −1 , respectively, were accomplished. Accuracy of the developed methodology was assessed by comparison with atomic absorption spectrometry being the relationship [FIA] mg l −1 =1.00 (±0.03)×[AAS] mg l −1 +0.00 (±0.02) obtained after analysing 15 samples. Precision was also evaluated using two samples of 0.05 and 0.5 mg l −1 copper, and a relative standard deviation (R.S.D.) better than 3% was attained for both.

The development of a new electrochemical microsensor based on silicon technology with a photocurable enzyme membrane based on polyurethane acrylate is described. The use of photocurable polymers as the entrapping matrix for enzymes fulfils all the requirements expected for these materials without damaging the biological material. Additionally, the preparation of biosensor devices following this methodology is fast and simple, and this entails the main improvement shown by the new immobilisation method proposed here. The polymer used for enzyme immobilisation enhances the adhesion of the membrane to the previously silanised ion-sensitive field effect transistor (ISFET) gate and assures a long-term stability of more than one month. Additionally, this material provides a membrane deposition methodology compatible with photolithographic techniques allowing mass-production of low cost biosensors. The membrane has been optimised taking into account a good entrapment of the biological material and the effective transport of the substrate and the products through the membrane. After mixing the components of the prepolymer solution, a short exposure (30 s) to 365 nm UV-radiation produced a polymeric membrane without damaging the enzyme. The calibration parameters for the sensors prepared compared well with other methods yielding a slope of 58 mV/dec and a linear range of 0.04–36.0 mM urea in a NH4Cl pH 5.6 solution. The response time (t 95%) was approximately 2 min.

The application of optimised poly(vinyl chloride) matrix, anionic surfactant-sensitive membranes to ion-selective field-effect transistors (ISFETs) is described. The developed devices showed a lifetime longer than four months, improving reported values of PVC membrane-ISFETs. Other characteristics are Nernstian slopes from 59 to 62 mV/dec, detection limits of about 10 ˇ6 M and good linearity. They also showed response to several anionic surfactant species and to the reagent used for the potentiometric titration. This allowed the measurement of the overall anionic surfactant content in different samples. Apart from the basic characteristics of the membranes, this report also shows the results of potentiometric titrations using the developed ISFETs with known samples. The devices were useful in a range from 0.02 to 10 mM for dodecylbenzenesulphonate solutions. End-point potential jumps up to 250 mV were obtained in the titrations. The reproducibility, expressed as relative standard deviation, was estimated, using a standard 4 mM sodium dodecylsulphate solution, as 1.45% (na14). Finally, in a comparative study, there were no significant differences between the results produced with the standard, two-phase titration method and the proposed potentiometric titration method using surfactant ISFETs as end-point indicators. # 1999 Elsevier Science B.V. All rights reserved.

A flow-injection system based on potentiometric detection and designed for the monitoring of anionic surfactant content of printing plates washing solutions is described. Two new PVC membrane ion-selective electrodes, constructed with an all-solid-state tubular flow-through design, are used. The sample, with high ionic strength and extremely alkaline pH, is conditioned in a two-channel flow-injection system, allowing for surfactant determination in the 1 × 10 −4 to 1 × 10 −3 M range, with NaOH contents up to 0.3 M.

A set of amino-group possessing cyanine dyes is obtained from their N-acetyl derivatives via deprotection with boron trifluoride–methanol complex in good yields.

The synthesis and characterization of new nor-indocrococyanine dyes are described. The acid form of the obtained dyes has an absorbance maxima in the 759–800 nm range. They present spectral changes at pH 6.5–9.7.

Ion-selective electrodes with poly(vinyl chloride) membranes cast directly on conductive composite substrates are easy to build and have shown their usefulness both in quiescent and flow analysis applications. Matching PVC-composite technology to that of ion-sensitive field-effect transistors (ISFETs) has produced a new type of hybrid chemical sensor. In this novel configuration, a graphite-loaded araldite layer is used to cover the gate opening of encapsulated ISFETs. A poly(vinyl chloride) membrane featuring a plasticiser and an ionophore is cast on top of the conductive composite, rendering the device sensitive to the ion of choice. The resulting hybrid devices show similar electrochemical features when compared to traditional sensors (ISFET + PVC membrane). They also display increased longevity and reduced optical sensitivity when compared with ISFETs featuring transparent PVC membranes.

New one-step synthesis of ketocyanine dyes is presented. The dyes obtained expose spectral changes in pH range from 1.7 to 4.3 and their protonated forms absorb at 715–750 nm.

Results obtained in the evaluation of a mathematical model for flow-injection sandwich systems, in which the sample is inserted between two different carrier solutions with the aid of an eight-way injection valve, are presented. The model considers the system as a tubular reactor with axially dispersed plug flow, where chemical kinetics have been included. Only a minimum of parameters are needed for the model: the dispersion coefficients, which are obtained from experimental correlations for the different hydrodynamic conditions, and the rate constants, which are determined by univariate optimization. The behaviour of the model, when applied to the case of one analyte and one reagent, was evaluated for the enzymatic determinations of glucose or glycerol. The case of two analytes determined with two reagents was also studied in the combined determination of glucose and glycerol. Experimental profiles were compared with the simulated peaks and showed good agreement.

A simple flow-injection metod for the determination of ammonium ions in water, based on a flow-through pH-ISFET, is described. Ammonium is converted to ammonia, which diffuses through a microporous hydrophic membrane into an ammonium chloride recipient stream, forming a pH buffer which is monitored by the semiconductor detector. The linear working range extends from 0.1 to 10 mmol l−1 with a relative standard deviation of ca. 1% at the 0.7 mmol l−1 level.

Synthesis of new acidochromic-based dyes is presented. The dyes obtained have acid absorbance maxima at 640–700 nm and expose spectral changes in the pH-range from 8 to 12.

Flow injection methodology based on sample insertion between two different standard solutions used as carrier streams is described. This approach provides a simple system for continuous recalibration in process control; spectrophotometric and ion-selective electrode procedures are outlined.

A simply constructed flow-through pH-ISFET detector suitable for flow-injection analysis is described. Its response characteristics are presented and discussed. The calibration plot is linear in the pH range 2–12; the slope is 53 mV per decade.

Samples (1500 μl) are inserted between zones of water and ascorbic acid solution with subsequent addition of 1,10-phenanthroline at pH 5.0. The signal provides a plateau region corresponding to Fe(Il) followed by a peak corresponding to total iron. The proposed system allows up to 90 injections per hour. Linear working ranges are 0.1–9 and 0.3–12 mg l−1 Fe(II) and total iron, with relative standard deviations of < 0.6 and 1.2%, respectively. Results obtained for various ground waters agree well with those obtained by a standard method.

A general construction procedure for conventional shape ion-selective electrodes based on a conductive support prepared with a mixture of a non-conductive epoxy and graphite was used in the preparation of a flow-through benzoate electrode to be used as potentiometric detector in flow injection analysis manifolds. The membranes were prepared from tetraoctylammonium benzoate in o -nitrophenyloctylether immobilized on PVC. The results of the assessment of the tubular electrodes behaviour in low dispersion manifolds against that of conventional electrodes with the same membrane are reported. Data obtained with a double-channel flow injection manifold incorporating these tubular detectors for benzoate determinations in several commercially available pharmaceutical preparations are also presented.

A tubular PVC membrane electrode for calcium without inner reference solution and a device for location of the reference electrode are described. In the flow-injection system, calcium is determined potentiometrically and then magnesium is determined by atomic absorption spectrometry. The electrode provides linear response to calcium in the range 5 × 10 −5 /2-10 −1 M. On-line dilution of the sample allows magnesium determination in the range 0/2-10 mg l − . Flow rates between 3 and 6 ml min −1 are possible. The sampling frequency is 60/2-90 h −1 .