Hydrodynamic Mode Of Operation Research Articles

Rapid and Accurate Validated Potentiometric Method for Bispyribac Herbicide Assessment in Rice and Agricultural Wastewater

A new validated method based on potentiometric transduction for bispyribac herbicide assessment in commercial formulations, rice and wastewater samples is fabricated and characterized. Sensors are based in terms of their fabrication on tridodecyl methyl ammonium chloride (TDMAC) as recognition material. TDMAC was plasticized in a poly (vinyl chloride) (PVC) matrix to prepare the membrane. Under static modes of operation, the sensors revealed a Nernstian anionic slope of −63.6 ± 0.7 mV/decade within a linear range of 9.1 × 10−6–1.0 × 10−2 in 50 mM phosphate buffer solution (PBS), pH7. The detection limit was 6.0 × 10−6 M. The sensor was successfully introduced in a flow-stream system revealing a Nernstian response of −53.8 ± 1.3 mV/decade over a linear range of 2 × 10−4–1.0 × 10−2 M and lower detection limit of 5.6 × 10⁻⁵ M. The sampling rate was calculated to be (~42 sample/h). Validation of the assay method is presented in detail including accuracy, trueness, bias, between-day variability and within-day variability, and good performance characteristics of the method are obtained. The presented method was successfully introduced to bispyribac determination in different complex matrices such as commercial bispyribac sodium known as (Nominee-kz, 3% soluble liquid (SL)), rice samples and agricultural wastewater samples. The samples were analyzed successfully under both static and hydrodynamic modes of operation. The results obtained were in a good agreement with those obtained by the liquid chromatographic method.

A New Validated Potentiometric Method for Sulfite Assay in Beverages Using Cobalt(II) Phthalocyanine as a Sensory Recognition Element.

A simple potentiometric sensor is described for accurate, precise, and rapid determination of sulfite additives in beverages. The sensor is based on the use of cobalt phthalocyanine as a recognition material, dispersed in a plasticized poly(vinyl chloride) matrix membrane. o-Nitrophenyl octyl ether (o-NPOE) as a membrane solvent and tri-dodecylmethyl- ammonium chloride (TDMAC) as ion discriminators are used as membrane additives. Under the optimized conditions, sulfite ion is accurately and precisely measured under batch and flow injection modes of analysis. The sensor exhibits fast and linear response for 1.0 × 10−2–1.0 × 10−6 M (800–0.08 µg/mL) and 1.0 × 10−1–5.0 × 10−5 M (8000–4 µg/mL) sulfite with Nernstian slopes of −27.4 ± 0.3 and −23.7 ± 0.6 mV/concentration decade under static and hydrodynamic modes of operation, respectively. Results in good agreement with the standard iodometric method are obtained.Validation of the assay method is examined in details including precision, accuracy, bias, trueness, repeatability, reproducibility, and uncertainty and good performance characteristics of the method are obtained. The sensor response is stable over the pH range of 5 to 7 without any significant interference from most common anions. The advantages offered by the proposed sensor (i.e., wide range of assay, high accuracy and precision, low detection limit, reasonable selectivity, long term response stability, fast response, and long life span and absence of any sample pretreatment steps) suggest its use in the quality control/quality assurance routine tests in beverages industries, toxicological laboratories and by inspection authorities.

TECHNOLOGY OF CYCLIC DISTILLATION IN ALCOHOL PRODUCTION

Alternate changing of the steaming periods and liquid overflow allows to intensify mass transfer between liquid and steam and to reduce the specific consumption of heating steam in the process of separation of multicomponent mixtures. Known methods and models have not found widespread practical use due to the lack of mass transfer in the steam period, fluctuations in steam pressure in the collector, the complexity of constructive solutions to ensure cyclic mode, etc. The authors propose a technology for rectification, which involves the cyclic motion of the liquid without interrupting of the supply of heating steam and the construction of a rectification column for its implementation. The purpose of the work was to research the effectiveness of the proposed technology in the process of rectification of alcohol-containing fractions and to establish the specific flow rate of steam in the impurity concentration column. To ensure a cyclic mode, the column was equipped with movable liquid transfer devices connected to actuating mechanismes, which acted according to the controller program, and perforated (scale-shaped) trays. The primary task was to determine the hydrodynamic mode of operation of the contact devices - the lower and upper the critical vapor velocity of at which the liquid is retained on the plates and there is its entrainment. It is established that the vapor velocity in the free section of the column can reach 1.2 m/s or more, and in the openings of the scales must exceed the first critical velocity of 6.5-7.5 m/s. The weeping of the tray occurs at the vapor velocity in the holes of 1.5-1 m/s. The investigations were carried out in the production conditions of the Chudniv branch of SE “Zhytomyr liquor producer ”. It is experimentally proved that in the process of rectification of alcohol-containing fractions, the main impurities are removed completely, the degree of extraction of higher fusel alcohols is increased by 38%, methanol - by 15.6 %, the multiplicity of concentration of the main impurities is increased by 25 %, the higher alcohols - by 40 %, methanol – by 34 %, acrolein – by 36 %. The costs of heating steam are reduced by 30 % compared to typical installations and do not exceed 13 kg/dal of absolute alcohol introduced with feed. Exempted from the key impurities the bottom liquid of the impurity concentration column should be used for hydroselection in the purifying column.

Optimal Parameters of Grooved Conical Hybrid Journal Bearing With Shear Thinning and Piezo-viscous Lubricant Behavior

To harness higher axial load capacity, a larger cone angle is used in conical bearings, resulting in an increase in the surface area which in turn increases the frictional power loss. The use of microgrooves in journal bearing helps in controlling this loss. Therefore, the present work is aimed to analyze conical hybrid journal bearing (i.e., combination of hydrostatic and hydrodynamic modes of operation) consisting of microgrooves along with shear thinning and piezo-viscous behavior of the lubricant. In this study, the microgroove attributes have been optimized by obtaining the solution of a Reynolds equation using finite element method and generalized minimum residual scheme (GMRES). These optimized groove attributes are used for numerically simulating the performance of the conical bearings. It has been observed that the best features of microgrooves and shear thinning behavior of the lubricant can be extracted to achieve better performance of the bearings. The results presented in this study are believed to be beneficial to the bearing designers and practising lubrication engineers.

The Effectiveness of Venturi Scrubber with Adjustable Throat for Aspiration of Shops for the Production of Mineral Fertilizers

There was presented improved design of Venturi scrubber with adjustable throat, intended for trapping particles from gas phase with more than 0.5 microns. There were determined hydrodynamic modes of operation of a new Venturi scrubber corresponding to the greatest efficiency in trapping particles. There was described flow chart on aspiration of emissions of mineral fertilizers production. There was made a comparison between the results of a mathematical model and test data on trapping of KCl particles during aspiration of shop for production of potash fertilizers. The residual dust content achieved is less than 10 mg/m 3 . There were presented equations for calculation of offered Venturi scrubber.

New potentiometric transducer based on a Mn(II) [2-formylquinoline thiosemicarbazone] complex for static and hydrodynamic assessment of azides

A new potentiometric transducer for selective recognition of azide is characterized and developed. The PVC plasticized based sensor incorporates MnII [2-formylquinoline thiosemicarbazone] complex in the presence of tri dodecyl methyl ammonium chloride (TDMAC) as a lipophilic cationic additive. The sensor displayed a near-Nernstian response for azide over 1.0×10−2–1.0×10−5molL−1, with an anionic slope of −55.8±0.6mVdecade−1 and lower limit of detection 0.34µgmL−1. The sensor was pH independent in the range 5.5–9 and presented good selectivity features towards several inorganic anions, and it is easily used in a flow injection system and compared with a tubular detector. The intrinsic characteristics of the detector in a low dispersion manifold were determined and compared with data obtained under a hydrodynamic mode of operation. This simple and inexpensive automation, with a good potentiometric detector, enabled the analysis of ~33 samples h−1 without requiring pre-treatment procedures. The proposed method is also applied to the analysis of trace levels of azide in primer mixtures. Significantly improved accuracy, precision, response time, stability and selectivity were offered by these simple and cost-effective potentiometric sensor compared with other standard techniques. The method has the requisite accuracy, sensitivity and precision to determine azide ions.

MEMBRANE SENSORS FOR STATIC AND HYDRODYNAMIC POTENTIOMETRIC ASSESSMENT OF CETIRIZINE DRUG IN PHARMACEUTICAL FORMULATIONS

The construction and electrochemical response characteristics of poly (vinyl chloride) (PVC) membrane sensors for the determination of cetirizine drug were described. These sensors were based on the use of the ion-association complexes of the cetirizinium cation (Cet + ) with phosphomolybdic acid (PMA) (sensor I), tetraphenylborate (TPB) (sensor II) and ammonium renickate (sensor III) counter anions as ion-exchange sites in a PVC matrix plasticized with dioctylphthalate (DOP). The sensors revealed fast, stable and Nernstian response between 9.0x10 -7 - 1.0x10 -3 mol L -1 and 5.2x10 -6 - 1.0x10 -3 mol L -1 with slope of 59.3±0.2, 60.6±0.3 and 61.5±0.2 mV and dection limits 5.3x10 -7 , 3.8x10 -6 and 5.2x10 -6 mol L -1 for sensor I, II and III respectively. The intrinsic characteristics of the detectors in a low dispersion manifold under hydrodynamic mode of operation are determined and compared with data obtained under batch mode of operation. Validation of the method reveals good performance characteristics including long life span, good selectivity for Cet + over a wide variety of other organic compounds, long term stability, high reproducibility, fast response, low detection limit, wide measurement range, acceptable accuracy and precision. Applications of the sensors for the determination of Cet + in pharmaceutical samples are also reported. The sensors offer several advantages over many of those previously described and are amenable for quality control/quality assurance assessment of the homogeneity, stability and purity of ephedrine drug tablets.

New potentiometric sensors based on selective recognition sites for determination of ephedrine in some pharmaceuticals and biological fluids

New cost-effective potentiometric membrane sensors with cylindrical configuration responsive to ephedrine are described. The sensors setup is, based on the use of triacetyl-β-cyclodextrin [(triacetyl-β-CD)] as a neutral ionophore embedded in a plasticized poly (vinyl chloride) (PVC) matrix (sensor I) and carboxylated poly(vinyl chloride) [(PVC–COOH)] as a simultaneous plastic matrix and ion exchanger (sensor II). Both sensors showed significant enhancement of response towards ephedrinium cation (EPD+) over a concentration range of 3.0×10−5–8.0×10−3molL−1 at pH 4–9 and 3–8 with low detection limits of 5.7×10−6 and 6.2×10−6molL−1 for sensors (I) and (II), respectively. The sensors displayed near-Nernstian cationic slope of 57.0 and 55.6mV decade−1 for EPD+ and the effects of lipophilic salts and various foreign common ions were examined. The sensors were also satisfactorily used as tubular detectors in a double channel flow injection system. The intrinsic characteristics of the detectors in a low dispersion manifold under hydrodynamic mode of operation were determined and compared with data obtained under batch mode of operation. Validation of the method revealed good performance characteristics including long life span, good selectivity for EPD+ over a wide variety of other organic compounds, long term stability, high reproducibility, fast response, low detection limit, wide measurement range, acceptable accuracy and precision. Applications of the sensors to the determination of EPD+ in pharmaceutical formulations and spiked biological fluid samples were carried out and compared with standard techniques. Notably, the sensors introduced offer several advantages over many of those previously described that are amenable to quality control/quality assurance assessment of the homogeneity, stability and purity of ephedrine drug tablets.

Biomimetic ciprofloxacin sensors made of molecularly imprinted network receptors for potential measurements

A molecularly imprinted polymer (MIP), with special molecule recognition properties of ciprofloxacin CIP), was prepared by thermal polymerization in which ciprofloxacin acted as the template molecule, methacrylic acid (MAA), acrylonitrile (AN) and 2-vinylpyridine (2-VP) acted as the functional monomer and ethylene glycol dimethacrylate (EGDMA) acted as the crosslinker. A biomimetic potentiometric field monitoring device was developed for the assessment of cirofloxacin (CIP) antibiotics based on these newly synthezised imprinted polymers. The sensing elements were fabricated by the inclusion of CIP imprinted polymers in polyvinyl chloride (PVC) matrix. The sensors showed a high selectivity and a sensitive response to the template in an aqueous system. Electrochemical evaluation of these sensors revealed near-Nernstian response with slopes of 29.9 ± 0.7, 27.9 ± 0.5, and 30.3 ± 0.8 mV decade−1 with a detection limit 41.3, 46.3, and 32 μg mL−1CIP with MIP/MAA, MIP/2-VP and MIP/AN membrane based sensors plasticized with DOP, respectively. The effects of lipophilic salts and various foreign common ions were tested. The sensors were easily used in a single channel flow injection system and compared with a tubular detector. The intrinsic characteristics of the detectors in a low dispersion manifold were determined and compared with data obtained under a hydrodynamic mode of operation. Significantly improved accuracy, precision, response time, stability, selectivity and sensitivity were offered by these simple and cost-effective potentiometric sensors compared with other standard techniques. The method had the requisite accuracy, sensitivity and precision to assay CIP in pharmaceutical formulations and biological fluids.

Batch and hydrodynamic monitoring of vitamin C using novel periodate selective sensors based on a newly synthesized Ni(II)-Schiff bases complexes as a neutral receptors

A highly selective membrane electrodes based on a two newly synthesized nickel (II) Schiff bases, [NiL 1] and [NiL 2] where L 1 and L 2 are N,N/bis(salicylaldehyde)4,5-dimethyl-1,2-phenylenediamine (H 2L 1) and N,N/bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (H 2L 2) were used as a neutral carrier ionophores for static and hydrodynamic potentiometric mode of operations for the determination of periodate. Under static mode of operation, the sensors displayed a near-Nernstian slope of −66.1 ± 0.8 and −59.9 ± 1.1 mV decade −1 of activity and detection limits to 5.2 × 10 −6 and 7.3 × 10 −6 mol L −1 for the sensors based on [NiL 1] and [NiL 2], respectively. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range were −71.1 mVdecade −1 of activity, 7.3 × 10 −6 and 1.0 × 10 −5 to 1.0 × 10 −3 mol L −1, respectively. The response time of the sensors in whole concentration ranges was very short (<10 s). The response of the sensors was independent on the pH range of 3–8. A tubular version was further developed and coupled to a flow injection system for ascorbic acid (AA) determination in beverages and pharmaceutical preparations. This approach was achieved by selecting a 50-cm reactor and an overall flow of 3 mL min −1, and injecting volume 100 μL of AA standards in a 1.0 × 10 −4 mol L −1 IO 4 − solution. Under these conditions, a linearity range of 2–13 μg mL −1, with a slope of 4.97 mV (mg/L) −1 ( r 2 = 0.9995), detection limit 0.9 mg L −1 and a reproducibility of ±1.1 mV ( n = 5) was recorded. This simple and inexpensive flow injection analysis manifold, with a good potentiometric detector, enabled the analysis of ∼50 samples h −1 without requiring pretreatment procedures. An average recovery of 98.8% and a mean standard deviation of 1.3% were obtained.

Cobalt phthalocyanine as a novel molecular recognition reagent for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants

Cobalt(II) phthalocyanine [Co(II)Pc] is used as both an ionophore and chromogen for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants (SDS), respectively. The potentiometric technique involves preparation of a polymeric membrane sensor by dispersing [Co(II)Pc] in a plasticized PVC membrane. Under batch mode of operation, the sensor displays a near-Nernstian slope of −56.5 mV decade −1, wide response linear range of 7.8 × 10 −4 to 8.0 × 10 −7 mol L −1, lower detection limit of 2.5 × 10 −7 mol L −1 and exhibits high selectivity for anionic surfactants in the presence of many common ions. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range are −51.1 mV decade −1, 5.6 × 10 −7 and 1.0 × 10 −3 to 1.0 × 10 −6 mol L −1, respectively. The spectrophotometric method is based on the use of [Co(II)Pc] solution in dimethylsulfoxide (DMSO) as a chromogenic reagent. The maximum absorption of the reagent at 658 nm linearly decreases with the increase of anionic surfactant over the concentration range 2–30 μg mL −1. The lower limit of detection is 1 μg mL −1 and high concentrations of many interfering ions are tolerated. Flow injection spectrophotometric measurements are carried out by injection of the surfactant test solution in a stream of the reagent in DMSO. The sample throughput, working range and lower detection limit are 25–30 samples h −1, 4–60 and 2 μg mL −1, respectively. The potentiometric and spectrophotometric techniques are applied to the batch and flow injection measurements of anionic surfactants in some commercial detergent products. The results agree fairly well with data obtained using the standard methylene blue spectrophotometric method.

Conventional and planar chip sensors for potentiometric assay of uric acid in biological fluids using flow injection analysis

The potentiometric response properties of several PVC-based membrane sensors using phthalocyanine complexes of cobalt(II) (CoPC) and Fe(II) (FePC) as anion carriers, towards uric acid were constructed and characterized. The sensors demonstrated fast near-Nernstian response for uric acid over the concentration ranges 9.1 × 10 −6 to 9.1 × 10 −2 and 3.1 × 10 −5 to 3.1 × 10 −2 M with detection limits 0.67 and 2.85 μg mL −1 over pH 6.5–8 for CoPC and FePC based membrane sensors plasticized with o-NPOE and 1% TDMAC, respectively. A novel solid-state planar chip urate sensor was developed, characterized according to IUPAC recommendations, easily used in a single channel wall-jet flow injection system and compared with a tubular detector. The intrinsic characteristics of the detectors in a low dispersion manifold were determined and compared with data obtained under hydrodynamic mode of operation. Validation of the assay methods with the proposed sensors by measuring the lower limit, range, accuracy, precision, repeatability and between-day-variability revealed good performance characteristics confirming applicability for continuous determination of uric acid. The sensors were used for determining urate in biological fluids at an input rate of 50 samples per hour. The results compare favorably with data obtained by the standard spectrophotometry.

A Novel Potentiometric Membrane Sensor Based on Aryl Palladium Complex for Selective Determination of Thiocyanate in the Saliva and Urine of Cigarette Smokers

AbstractA highly selective potentiometric sensor for thiocyanate ion based on the use of a newly synthesized organo‐palladium ion exchanger complex dispersed in a plasticized poly(vinyl chloride) membrane is described. The sensor displays a Nernstian response (−57.8±0.2 mV decade−1) over a wide linear concentration range of thiocyanate (1.0×10−6–1.0×10−1 mol L−1 ), low detection limit (6.3×10−7 mol L−1), fast response (20 s), stable potential readings (±0.4 mV), good reproducibility (±0.9%), long term stability (8 weeks), high precision (±0.7%) and applicability over a wide pH range (4–10). Negligible interferences are caused by F−, Cl−, I−, Br−, NO3−, NO2−, CN−, SO42−, S2O32−, PO43−, citrate, acetate and oxalate ions. Under hydrodynamic mode of operation (FIA), the calibration slope is −51.1±0.1 mV decade−1, the linear response range is 1.0×10−5–1.0×10−1 mol L−1 SCN− and the sample throughput is 40–45 per hour. The sensor is satisfactory used for manual and flow injection potentiometric determination of SCN− in the saliva and urine of cigarette smokers and non smokers. The data agree fairly well with results obtained by the standard spectrophotometric technique. Direct potentiometry and potentiometric titration of SCN− with Ag+ are also monitored with the sensor.

A novel planar miniaturized potentiometric sensor for flow injection analysis of nitrates in wastewaters, fertilizers and pharmaceuticals

A novel all-solid-state miniaturized nitrate sensor is developed, characterized and used for flow injection analysis (FIA) of nitrates in various samples. The sensor incorporates silver bis(bathophenanthroline) nitrate [Ag(bath) 2NO 3] as an electroactive material in a plasticized PVC membrane. The sensing membrane (3 mm × 5 mm) is immobilized on a wafer polyimide microchip (size 13.5 mm × 3.5 mm) to offer a planar miniaturized design easily used in a single channel wall-jet flow injection system. Under hydrodynamic mode of operation (FIA) the sensor displays fast response, high sensitivity, long term stability and good selectivity for NO 3 − in the presence of many common associated anions. The calibration slope is 55.1 ± 0.1 mV decade −1 over the concentration range 1.0 × 10 −1 to 1.0 × 10 −6 mol L −1, the lower detection limit is 0.05 μg mL −1, the working pH is 2–9,and the output is 70–90 samples h −1. Validation of the assay method reveals good performance characteristics and suggests application for routine determination of NO 3 − in industrial wastewaters, fertilizers and pharmaceuticals. The results agree fairly well with data obtained by the standard spectrophotometric methods.

Novel Biomedical Sensors for Flow Injection Potentiometric Determination of Creatinine in Human Serum

Coated-wire (CW) and tubular (Tu) type membrane sensors for creatinine are developed. These consist of creatinine tungstophosphate(CTP), creatinine molybdophosphate (CMP) and creatinine picrolonate (CPC) ion-pair complexes as electroactive materials dispersed in plasticized poly(vinyl chloride) matrix membranes. Electrochemical evaluation of these sensors under static (batch) mode of operation reveals near-Nernstian response with slopes of 62.9, 58.1, and 55.2 mV decade−1 over the concentration range 1×10−2–5.0×10−6, 1×10−2–7.5×10−5, and 1×10−2−3.1×10−5 mol L−1. The lower detection limits are 0.39, 3.49, and 2.20 μg mL−1 creatinine with CTP, CMP and CPC membrane based sensors plasticized with o-NPOE, respectively. Tubular and coated wire CTP membrane sensors are incorporated in flow-through cells and used as detectors for flow injection analysis (FIA) of creatinine. The intrinsic characteristics of the detectors under hydrodynamic mode of operation in a low dispersion manifold are determined and compared with data obtained under static mode of operation. With 10−2 mol L−1 phosphate buffer of pH 4.5 as a carrier solution, the tubular and coated wire CTP detectors exhibit rapid response of 58.9 and 50.7 mV decade−1 over the concentration range 1×10−2–1×10−5 mol L−1 and detection limits of 0.39 μg mL−1 and 0.85 μg mL−1, respectively. Validation of the assay methods with the proposed sensors by measuring the lower detection limit, range, accuracy, precision, repeatability and between-day-variability reveals good performance characteristics confirming applicability for continuous determination of creatinine. The sensors are used for determining creatinine in human blood serum at an input rate of 40 samples per hour. No interferences are caused by creatine, most common anions, cations and organic species normally present in biological fluids. The results favorably compare with data obtained using the standard spectrophotometric method.

SOLID STATE IRIDIUM OXIDE–TITANIUM BASED SENSOR FOR FLOW INJECTION pH MEASUREMENTS

ABSTRACT Iridium oxide-coated titanium wire is prepared by controlled electrodeposition (current density 5 mA/cm2 for 10 min) and used as a solid state pH sensor. The sensor is sensitive for pH variations over the range 2–10 with calibration slopes of ˜ 65.5 and 59.1 mV/pH unit under static and hydrodynamic modes of operation, respectively. The general performance characteristics of the sensor are similar to those of the glass electrode for direct pH monitoring of solutions. The sensor exhibits reasonable stability (±0.005 pH), reproducibility (±2%) and fast response time (20–30 s). The method of preparation is simple, utilizes an inexpensive titanium metal substrate and offers the possibility of fabrication of sensors with various geometry and/or of micro and ultramicro sizes usable for flow injection analysis. No interferences are caused by alkali and alkaline earth metal cations and various anions at level ≥ 104 molar excess over H+.

Flow Injection Potentiometric Determination of Atrazine in Herbicide Formulations

A novel atrazinium selective membrane sensor consisting of an atrazine phosphomolybdate ion-pair complex dispersed in a PVC matrix plasticized with dioctylphthalate is described and electrochemically evaluated under static and hydrodynamic modes of operation. The sensor is incorporated in a flow-through sandwich cell and used as a detector for flow injection determination of atrazine herbicide. The intrinsic characteristics of the detector in a low dispersion manifold is determined and compared with those of a conventional-shaped sensor. In a phosphate buffer of pH 5, the detector exhibits a rapid near-Nernstian response (52.3 mV/decade) for atrazinium cation over the concentration range 10−2 - 10−5 M. Concentrations as low as 0.3μg/ml of atrazine can be detected with an average recovery of 98.3% (mean standard deviation 0.6%), and the sample input rate is 60 sample per hour. The sensor is used for determining atrazine in herbicide formulations, and in extracts of water and soil. No interferences are caused by herbicide diluents and excipients nor by most common anions and cations normally present in water and soil. The results compare favorably with data obtained by gas liquid chromatography.

Membrane sensors for batch and flow injection potentiometric determination of ethamsylate (cyclonamine) in pharmaceutical preparations

The lipophilic nickel(II) and iron(II) bathophenanthroline derivatives of ethamsylate are used as ion-exchangers with high selectivity characteristics for ethamsylate. Poly(vinyl chloride) membrane sensors incorporating these electroactive materials display fast linear response for 1 × 10−1−1 × 10−4M ethamsylate under static and hydrodynamic modes of operation. In an acetate buffer of pH 4, the calibration slope is 51–53 mV/concentration decade and the lower limit of detection is 5.3 μg/ml. Except for salicylate and nitrate, most common anions, organic sulfonates, carboxylates, phenolates and various pharmaceutical excipients and diluents do not interfere. Determination of ethamsylate in various dosage forms shows an average recovery of 98.9% of the nominal and a mean standard deviation of 0.7%.

Miniaturized graphite sensors doped with metal-bathophenanthroline complexes for the selective potentiometric determination of uric acid in biological fluids.

Miniaturized poly(vinyl chloride) matrix membrane sensors in an all-solid-state graphite support, responsive to urate anion, were developed. The membranes incorporate lipophilic ion-pair complexes of urate anion with ruthenium(III), iron(II), nickel(II) and copper(I) bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) counter cations. The sensors demonstrate a near-Nernstian response to urate over the concentration range 1 x 10(-2)-1 x 10(-5) mol l-1 and have micromolar detection limits and good selectivity properties. The response is virtually unaffected by pH changes in the range 7-10 and the response times are 5-10 s in aqueous solutions and in human serum and urine samples. A flow injection detector incorporating an iron(II) bathophenanthroline-urate graphite sensor was used for continuous monitoring of uric acid. The minimum detectable concentration was approximately 8 micrograms ml-1 and the sample throughput was approximately 120 h-1. Direct potentiometric determination of uric acid in the static and hydrodynamic modes of operation over the range 15 micrograms ml-1-1.5 mg ml-1 showed average recoveries of 98.7 and 97.8% with RSDs of 0.6 and 0.7%, respectively. Application of the method to the determination of uric acid in human serum and urine gave results that compared favourably with those obtained by the standard spectrophotometric method.