Flow Injection Potentiometry Research Articles

Optimasi dan Karakterisasi Kinerja Sistem Pengukuran Potensiometrik Fosfat dengan Elektroda Kobalt Secara Flow Injection Analysis

Phosphorus is known as an essential nutrient required by plant in large numbers and absorbed in the form of phosphate ions, either as a primary orthophosphate ion H2PO4- or secondary orthophosphate ion HPO42-. Concentration of the phosphorus in the soil is usually determined by the spectrophotometric method, while the potentiometric method has not been widely used because of the availability of the phosphate-selective electrodes are not yet available in the market. This research has been conducted in the development and assessment of performance of the potentiometric method that utilizes cobalt metal in the quantitative determination of the phosphate ions in the flow system. Firstly it was performed optimization of pH and concentration of the used buffer solution and the flow rate of the solution to obtain the optimum response of the cobalt electrode in the presence of phosphate ions. It was then followed by an evaluation of the working performance of the flow injection potentiometry method and an interference test of some solutions that are commonly used as a solvent extractors of soil samples. The result showed that the optimum system was achieved when the buffer solution was set to pH 4 at concentration of 1 x 10-3 M and at the flow rate of 2 mL/minute. According to the characterisation results of the method in the process of phosphate determination, the method has a linearity of 0.99, detection limit of 4.86 x 10-5 M, sensitivity of 22.569 mV / decade and precision of ≤ 5%.

Aqueous phase sensing of bismuth ion using fluorescent metal-organic framework

In this work, the fluorescent CAU-1-(OH)2 was successfully exploited as a fluorescent probe for bismuth ion (Bi3+) in aqueous solutions, which is the first MOF-based fluorescent sensor for Bi3+ up to date. The MOF can exhibit bright green fluorescence in H2O for the intramolecular proton transfer process between the ligand and H2O molecule. In addition, the carboxylate and hydroxyl groups in the MOF can strongly coordinate with Bi3+. Accordingly, CAU-1-(OH)2 can selectively detect Bi3+ in water in 24 s. In addition, the limit of detection of this MOF was calculated to be 2.16 μM, superior to those of some traditional methods such as spectrophotometry and flow injection potentiometry.

Simultaneous and automated monitoring of the multimetal biosorption processes by potentiometric sensor array and artificial neural network

In this communication, a new methodology for the simultaneous and automated monitoring of biosorption processes of multimetal mixtures of polluting heavy metals on vegetable wastes based on flow-injection potentiometry (FIP) and electronic tongue detection (ET) is presented. A fixed-bed column filled with grape stalks from wine industry wastes is used as the biosorption setup to remove the metal mixtures from the influent solution. The monitoring system consists in a computer controlled-FIP prototype with the ET based on an array of 9 flow-through ion-selective electrodes and electrodes with generic response to divalent ions placed in series, plus an artificial neural network response model. The cross-response to Cu2+, Cd2+, Zn2+, Pb2+ and Ca2+ (as target ions) is used, and only when dynamic treatment of the kinetic components of the transient signal is incorporated, a correct operation of the system is achieved. For this purpose, the FIA peaks are transformed via use of Fourier treatment, and selected coefficients are used to feed an artificial neural network response model. Real-time monitoring of different binary (Cu2+/ Pb2+), (Cu2+/ Zn2+) and ternary mixtures (Cu2+/ Pb2+/ Zn2+), (Cu2+/ Zn2+/ Cd2+), simultaneous to the release of Ca2+ in the effluent solution, are achieved satisfactorily using the reported system, obtaining the corresponding breakthrough curves, and showing the ion-exchange mechanism among the different metals. Analytical performance is verified against conventional spectroscopic techniques, with good concordance of the obtained breakthrough curves and modeled adsorption parameters.

Flow-Injection Potentiometry by Poly(vinyl chloride)-Membrane Electrodes with Diphosphoryl-dicarboxylicacid-p-tert-butylcalix[4] arene Ionophore for the Determination of Th(IV) Ions

A new coated ion-selective electrode for the determination of trace thorium ions by flow-injection potentiometry (FIP) has been developed. A poly(vinyl chloride) (PVC)-based membrane was coated on a graphite electrode. The optimum membrane contained 5 wt% diphosphoryl-dicarboxylicacid-p-tert-butylcalix[4]arene (L) as the ionophore, 59 wt% dioctyl phthalate (DOP), 33 wt% PVC and 3 wt% additive sodium tetraphenylborate. The response was linear from 2.0 × 10(-7) to 1.0 × 10(-2) M with a slope of 13.9 mV decade(-1) and a limit of detection of 9.0 × 10(-8) M. The pH-independent region ranged from 3.15 to 6.5, and the lifetime was longer than 8 weeks when used in the flow injection analysis (FIA) system. Selectivity coefficients for several ions were obtained by the separate solutions method. Results showed that, for all cations used, the selectivity coefficients were in the order of 10(-3), or smaller. The flow cell is simple to construct and free from memory effect problems over long periods of use. The proposed sensor was successfully applied to the direct determination of thorium in both real and synthetic samples.

SELECTIVE RECOGNITION IN POTENTIOMETRIC SENSING BASED ON TWO COMPETITIVE RECOGNITION SITES FOR STATIC AND HYDRODYNAMIC DETERMINATION OF CAMYLOFIN AS A SMOOTH MUSCLE RELAXANT

A poly (vinyl chloride) matrix membrane sensors for selective determination of camylofin (CY) in pharmaceutical formulations were developed based on the use of dibenzo-18crown-6 (DB18C6) as a neutral carrier and ion-association complex ([CY]2[PM])of (CY) cation with phosphomolybdate anion (PM). Subsequently, these electroactive materials were dispersed in dioctyl sebacate (DOS) as solvent mediator designed and can be easily used in flow injection system. Under static mode of operation, the sensors revealed a near Nernstain response over a wide CY + concentration range 8.5x 10 -6 and 5 x 10 -6 to 1.0 x 10 -2 mol L -1 with a detection limit of 6.0x10 -6 and 2.5x10 -6 mol L -1 , respectively. In flow injection potentiometry, excellent reproducibility (RSD %±0.7%), fast response, high sensitivity with a near-Nernstian 53.9±1.1 and 40.2±0.8 mV decade -1 , linear range 1.0x10 -4 -1.0x10 -2 mol L -1 , detection limit 16.4±0.3 and 5.9±0.3 μg mL -1 , high sampling rate (20-22 and 40-45 sample h -1 ) and stable baseline was observed in the presence of 0.05 mol L -1 citrate buffer, pH 4.5 as a carrier for ([CY]2[PM] and (DB18C6) membrane based sensors, respectively. The utility of the sensors was tested for field monitoring of CY + in different pharmaceutical formulations collected from the local market.

Synthesis, characterisation and application of two new lariat crown ethers in construction of PVC membrane, coated wire and coated graphite electrodes: application to flow injection potentiometry

Two lariat crown ethers, 7-(2-Hydroxy-5-methylbenzyl)-5,6,7,8,9,10-hexahydro-2H-benzo[b][1,4,7,10,13]pentadecine-3,11(4H,12H)dione, L1 and, (7-(5-tert-buthyl-2-hydroxybenzyl)-5,6,7,8,9,10-hexahydro-2H-benzo[b][1,4,7,10,13]dioatriazacyclopentadecine-3,11 (4h, 12, H) dione, L2 was synthesised, characterised and used as active components for fabrication of PVC membrane electrode (PME), coated graphite electrode (CGE) and coated wire electrodes (CWE) for sensing Co2+ ion. Potassium tetrakis(p-cholorophenyl) borate(KTpClPB) and o-nitrophenyloctyl ether (o-NPOE) were used as anion excluder and plasticiser, respectively, in a PVC matrix. The two lariat ethers were tested, L1 has shown better electrode characteristics than the other. The electrodes exhibited linear Nernstian responses to Co2+ ion in the linear concentration range of 3.3 × 10−6–1.9 × 10−2 M (for PME), 2.3 × 10−7–7.9 × 10−2 M (for CWE), and 5.0 × 10−8–1.2 × 10−2 M (for CGE). The CGE was used as a proper detection system in flow-injection potentiometry (FIP) with a linear Nernstian range of 2.3 × 10−7–1.2 × 10−2 M. Over a pH range of 3.2 to 8.0, the limit of detection for PME, CWE, CGE, and CGE-FIP systems were found to be 1.2 × 10−6, 2.5 × 10−7, 3.5 × 10−8 and 1.0 × 10−7 M, respectively. The electrodes revealed fairly good discriminating ability towards Co2+ in comparison with a large number of alkali, alkaline earth, transition and heavy metal ions. The electrodes were found to be chemically inert, showing fast response time of <5 s, and could be used practically over a period of 1 month. CGE has also been used for measurement of Co2+ in binary mixtures.

ChemInform Abstract: Determination of Penicillamine by Batch and Flow-Injection Potentiometry with AgI-Based Sensor.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Flow-injection potentiometric applications of solid state Li+ selective electrode in biological and pharmaceutical samples

A solid state polyvinyl chloride (PVC) membrane Li+-selective electrode was prepared and used as a detector in a low-dead volume flow through cell for the determination of Li+ in pharmaceutical formulations and human serum samples. The potentiometric performance characteristics of the electrode were calculated under the optimized flow conditions. The electrode had near-Nernstian behavior in the concentration range of 0.1–100 mM (R 2 = 0.9981) with a slope of 61.34 mV decade−1 and detection limit of 0.080 mM. The relative standard deviation of the electrode response for eight replicate measurements of 100, 10, and 1 mM Li+ was 0.43%, 0.45%, and 0.99%, respectively. The designed flow-through cell detector system revealed sampling rates of approximately 70 injections per hour. Flow injection potentiometry (FIP) results obtained for the pharmaceutical formulations were in good harmony with the atomic emission spectrophotometry results. However, the electrode could not be used successfully for the direct analysis of real serum samples in FIP.

Screen-printed sensor for batch and flow injection potentiometric chromium(VI) monitoring

A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis. The carbon screen-printed electrode was modified with a graphite-epoxy composite. The optimal graphite-epoxy matrix contains 37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed sensor exhibits a response time of 20 +/- 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour using 0.1 M NaNO(3) solution at pH 3 as the carrier, a flow rate of 2.5 mL.min(-1), and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI) ions and optimal detection limits in both static mode (2.1 x 10(-7) M) and online analysis (9.4 x 10(-7) M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful results in leachates from municipal solid waste landfills.

Comparison of Detectors and Cell Configurations in Flow-Injection Potentiometeric Technique of Pharmaceutical Analysis

Carbon paste and PVC electrodes were constructed and incorporated in the flow injection system for potentiometric determination of amantadine (AM), metformin (MF), ranitidine (RN) and trimetazidine (TRMZ). Wall-jet and continuous flow cells were designed where the wall-jet cell showed better performance regarding the sample dispersion and sensitivity to the change in flow rate. CPEs were more suitable for incorporation in the flow-injection systems due to its fast response, mechanical strength and lifetime. The proposed electrodes showed linear calibration graphs in the concentration range from 10 -5 to 10 -1 mol L -1 with Nernstian slopes values of 61.4±1.7, 60.1±0.99, 65.5±2.0 and 30.9±1.1 mV decade -1 for AM, MF, RN and TRMZ, respectively. The developed electrodes have been successfully applied for flow injection potentiometric determination of the investigated drugs in their pharmaceutical formulation with sample output of 120 samples h −1 and the advantage of simplicity, accuracy and automation feasibility. Key word: Flow-injection potentiometry; CPEs; PVC electrode; Cell configurations; Pharmaceuticals analysis.

Novel PVC-membrane potentiometric sensors based on a recently synthesized sulfur-containing macrocyclic diamide for Cd 2+ ion. Application to flow-injection potentiometry

A new sulfur-containing macrocyclic diamide, 1,15-diaza-3,4,12,13-dibenzo-5,11-dithia-8-oxa-1,15-(2,6-pyrido)cyclooctadecan-2,14-dione, L, was synthesized, characterized and used as an active component for fabrication of PVC-based polymeric membrane (PME), coated graphite (CGE) and coated silver wire electrodes (CWE) for sensing Cd 2+ ion. The electrodes exhibited linear Nernstian responses to Cd 2+ ion in the concentration range of 3.3 × 10 −6 to 3.3 × 10 −1 M (for PME, LOD = 1.2 × 10 −6 M), 2.0 × 10 −7 to 3.3 × 10 −1 M (for CWE, LOD = 1.3 × 10 −7 M) and 1.6 × 10 −8 to 1.3 × 10 −1 M (for CGE, LOD = 1.0 × 10 −8 M). The CGE was used as a proper detection system in flow-injection potentiometry (FIP) with a linear Nernstian range of 3.2 × 10 −8 to 1.4 × 10 −1 M (LOD = 1.3 × 10 −8 M). The optimum pH range was 3.5–7.6. The electrodes revealed fairly good discriminating ability towards Cd 2+ in comparison with a large number of alkali, alkaline earth, transition and heavy metal ions. The electrodes found to be chemically inert, showing a fast response time of <5 s, and could be used practically over a period of about 2–3 months. The practical utility of the proposed system has also been reported.

Chromium(III) determination without sample treatment by batch and flow injection potentiometry

A new and easy device for direct detection of chromium(III) in batch and flow analysis without previous oxidation/reduction or preconcentration steps of samples is designed and evaluated. For this purpose a potentiometric sensor with solid state membrane based on carbon paste matrix is developed. The sensor is modified with di(2-hydroxyphenylimino)ethane and the principal analytical parameters of the potentiometric response in batch and flow analysis are optimized and calculated. Optimal detection limits (1.4 × 10 −7 M in static mode and 5.4 × 10 −7 M in on-line analysis) and selectivity to trivalent chromium are obtained in both analysis modes. The use of this device to direct detection of chromium(III) in real samples is tested using a sediment Certified Reference Material. Chromium(III) determination is also carried out with successful results in environmental samples such as extracts from soils used as barriers in landfills and industrial samples such as waste waters from electroplating industries.

Macrocyclic compound as ionophores in lead(II) ion-selective electrodes with excellent response characteristics

Macrocyclic compounds, such as crown ethers, azacrown ethers, thiacrown ethers, calixarenes and porphyrins, which act as ionophores in lead(II) ion-selective electrodes, are systematically summarized based on the latest literatures. The molecular structure characteristics of the ionophores are generalized. The modification regulations for the substituted ionophores are elaborated with the purpose of improving the response features of the lead(II) ion-selective electrodes assembled by them. It is pointed out that the introduction of pendant moieties which contain soft base coordination centers like N, S and P atoms is in favor of adjusting the cavity size and conformation of the macrocyclic compounds. Furthermore, there is synergic effect between the cavity and the donor sites of the ligand and thus the selective complexation of lead ions is easily realized, resulting in significant avoidance of the interference from other metal ions. The macrocyclic ionophore having the best response characteristics thus far was found to be N,N′-dimethylcyanodiaza-18-crown-6 with the detection limit of 7.0×10−8 (14.5 μg/L), which is one of the uncommon ionophores that can really eliminate the interference from silver and mercury ions. The selectivity coefficients of the ionophore for lead ions over other metal ions, such as alkali, alkaline earth and transition metal ions are in the order of 10−4 or smaller, where the selectivity coefficient of lead(II) over mercury(II) ions is much lower, down to 8.9×10−4. The structure design idea for high-performance ionophore is proposed according to present results. The incorporation of nitrogen atom, especially cyano group or thiocyano group or amino/imino groups, rather than thio atom alone could result in new excellent lead ionophores. The aborative design for metacyclophanes containing aromatic nitrogen atoms with the aim of creating excellent ionophores would also become a potential research trend. The lead(II) ion-selective electrodes have shown widely potential applications in the potentiometric titration, and flow injection potentiometry, and in the direct determination of lead in stack emissions of lead smelters, and assay of lead in rocks, particularly in the direct measurements of trace amount of lead(II) in human hair, blood, edible oil, food, water, and air.

Highly Selective Cyanide Coated-Wire Electrode Based on a Recently Synthesized Co(II) Complex With the &lt;formula formulatype="inline"&gt; &lt;tex&gt;$N,N^{\prime}$&lt;/tex&gt; &lt;/formula&gt;-Bis(2-Quinolinecarboxamido)- 1,2-Benzene Applying Batch and Flow Injection Analysis Techniques

A poly(vinyl chloride) (PVC)-based coated wire electrode based on [Co(II)bqb] (bqb = N,N'-bis(2-quinolinecarboxamido)-1,2-benzene) as a novel sensing material for determination of trace amounts of cyanide ions is successfully developed. The effect of electrode substrate, membrane composition and pH of the working solution on the behavior of the sensor was investigated. The electrode was also used in flow injection potentiometry by a home-made flow cell. The electrode revealed Nernstian response towards cyanide anion over the concentration ranges 3.2times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> to 2.0times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> molldrL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 5.0times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> to 1.0times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> molldrL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> applying batch and flow injection analysis (FIA), respectively. The lower detection limits are 3.2times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> molldrL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 5.0times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> molldrL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> for batch and FIA, respectively. The electrode shows a short response time (<5 s) in the whole concentration range. The selectivity of the electrode in comparison with most of cyanide selective electrodes is high. The flow cell is simple to construct and free from memory effect problems over long periods of use. The proposed electrode was successfully applied for the determination of cyanide in commercially available spring water under both batch and flow injection conditions. A comparative study revealed no significant difference between ASTM method and the proposed technique.

A Novel Flow‐Through Planar Solid Contact Sensor for the Determination of Lead with Potentiometric Anionic Response

AbstractThe construction and general performance characteristics of two poly(vinyl chloride) matrix chemical sensors for lead were described. These sensors were based on the use of ion association complexes of trihydroxoplumbate, [Pb(OH)3]− and tetraiodoplumbate, [PbI4]2−with cetylpyridinium chloride (CP) and iron(II)‐4,7‐bathophenanthroline [Fe(bphen)3]2+ as novel electroactive materials dispersed in o‐nitrophenyloctyl ether (o‐NPOE) plasticizer for ionometric sensor controls, respectively. The sensing membrane (3×5 mm) is immobilized on a wafer polyimide chip (size 13.5×3.5 mm) to offer a planar miniaturized design that could be easily used flow injection system. Under static modes of operation, the sensors revealed a near Nernstian response over a wide Pb2+ ion concentration range 7.9×10−7 to 10−4 and 3.2×10−7 to 10−4 mol L−1 with detection limit of 100 and 45.5 ng mL−1, respectively . In flow injection potentiometry, excellent reproducibility (RSD%=0.5%), fast response, high sensitivity, high sampling rate (50 sample h−1) and stable baseline was observed in the presence of 5×10−2 mol L−1 NaOH and 10−1 mol L−1 KI as a carrier for [CP][Pb(OH)3] and [Fe(bphen)3][PbI4] membrane based sensors, respectively. Validation of the assay method according to the quality assurance standards (range, within‐day repeatability, between‐day variability, standard deviation, accuracy, lower detection limit) reveals good performance characteristics and suggests application for routine determination of lead in industrial wastewaters and stack emissions of lead smelters. The results agree fairly well with data obtained by the standard atomic absorption methods.

Novel lipoate-selective membrane sensor for the flow injection determination of α-lipoic acid in pharmaceutical preparations and urine

A potentiometric lipoate-selective sensor based on mercuric lipoate ion-pair as a membrane carrier is reported. The electrode was prepared by coating the membrane solution containing PVC, plasticizer, and carrier on the surface of graphite electrode. Influences of the membrane composition, pH, and possible interfering anions were investigated on the response properties of the electrode. The sensor exhibits significantly enhanced response toward lipoate ions over the concentration range 1 × 10 −7 mol L −1 to 1 × 10 −2 mol L −1 with a lower detection limit of (LDL) of 9 × 10 −8 mol L −1 and a slope of −29.4 mV decade −1, with S.D. of the slope is 0.214 mV. Fast and stable response, good reproducibility, long-term stability, applicability over a pH range of 8.0–9.5 is demonstrated. The sensor has a response time of ≤12 s and can be used for at least 6 weeks without any considerable divergence in its potential response. The proposed electrode shows good discrimination of lipoate from several inorganic and organic anions. The CGE was used in flow injection potentiometry (FIP) and resulted in well defined peaks for lipoate ions with stable baseline, excellent reproducibility and reasonable sampling rate of 30 injections per hour. The proposed sensor has been applied for the direct and FI potentiometric determination of LA in pharmaceutical preparations and urine; and has been also utilized as an indicator electrode for the potentiometric titration of LA.

Flow injection potentiometry by a novel coated graphite electrode based on 5-(9-anthracenylmethyl)-5-aza-2,8-dithia[9],(2,9)-1,10-phenanthrolinophane for the selective determination of uranyl ions

Abstract Spectrofluorimetric studies on the binding properties of 5-(9-anthracenylmethyl)-5-aza-2,8-dithia[9],(2,9)-1,10-phenanthrolinophane (L) toward different heavy metal ions in methanol solution revealed its selective 2:1 (ligand/metal) complexation with uranyl ion. Consequently, L was used as a suitable ionophore for the preparation of new plasticized PVC membrane-selective electrodes for the determination of uranyl ion by flow injection potentiometry. The electrodes resulted in Nernstian responses for UO22+ ion over wide concentration ranges (1.0 × 10−6 to 1.0 × 10−1 M with a detection limit of 8.3 × 10−7 M for polymeric membrane electrode, PME, and 1.0 × 10−7 to 1.0 × 10−1 M with a detection limit of 7.5 × 10−8 M for coated graphite electrode, CGE). The potentiometric response is independent of the pH of test solution in the pH range 2.5–4.0. The proposed electrodes possess very good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The CGE was used in flow injection potentiometry and resulted in well defined peaks for uranyl ions with stable baseline, excellent reproducibility and very high sampling rate of 160 injections h−1. The proposed FIP system was used for the determination of trace uranyl ions in real and synthetic samples.

A novel flow injection potentiometric graphite coated ion-selective electrode for the low level determination of uranyl ion

Solution studies on the binding properties of uranyl ion toward four different recently synthesized benzo-substituted macrocyclic diamides L1-L4 revealed the occurrence of a 1:1 complexation of the ligands with UO 2 2+ ion, with a stability order of L2 > L1 > L4 > L3. Consequently, L2 was used as a suitable neutral ionophore for the preparation of novel polymeric membrane (PME) and coated graphite (CGE) UO 2 2+-selective electrodes. The electrodes exhibit a Nernstian behavior for UO 2 2+ ions over wide concentration ranges (1.0 × 10 −6–1.0 × 10 −1 M for PME and 1.0 × 10 −7–1.0 × 10 −1 M for CGE) and very low limits of detection (8.0 × 10 −7 M for PME and 7.3 × 10 −8 M for CGE). The proposed potentiometric sensors manifest advantages of fast response and, most importantly, good selectivity with respect to many alkali, alkaline earth, transition, and heavy metal ions. The potentiometric responses of the electrodes are independent of the pH of the test solution in the pH range 2.9–3.7. The CGE was used in flow injection potentiometry and resulted in well defined peaks for uranyl ions with stable baseline, excellent reproducibility and very high sampling rate of 170 injections per hour. The proposed FIP system was used for the determination of trace uranyl ions in real and synthetic samples.

Use of a solid-phase extraction disk module in a FI system for the automated preconcentration and determination of surfactants using potentiometric detection

The global determination of anionic surfactants is proposed by using flow injection potentiometry, and by employing specifically developed tubular flow-through ion selective electrodes (ISEs). The low concentration requirements needed for the environmental application are obtained with an on-line preconcentration stage embedded in the flow system, which has as its goal the unattended monitoring of anionic surfactants in surface waters. The on-line preconcentration is achieved by employing an octadecylsilica extraction disk in the FIA system. This stage performs the solid phase extraction (SPE) for the enrichment and purification of the target analytes from common interfering anions. The outlined procedure improves the detection limit of a direct injection system, which is decreased from 10 to 0.25 μM by using a preconcentration volume of 3.0 mL and 50 μL of 75% acetonitrile in water as the eluent. Precision was estimated as 2.9% relative standard deviation ( n = 20) for a 0.25 μM (0.070 mg·L − 1 ) sodium docecylsulfate standard.

Long-term and High Temporal Resolution In-situ Monitoring of Potassium, Sodium, and Chloride in a Small Forested Catchment Using Flow Injection Potentiometry

Long-term water quality data with high temporal resolution, together with hydrological data, are essential in developing hydrogeochemical and diffuse pollution modeling. An in situ flow injection potentiometry (FIP) system to monitor the stream water quality (chloride, sodium and potassium) every 15 minutes for two weeks was developed and tested in the laboratory and in a small forested catchment in Gozyo City, Nara Prefecture, Japan. The system resolves main hurdles that prevent long-term monitoring, except the problem of samples freezing in winter. Frequent calibration with three standards was adopted to compensate for the temperature dependency of ion-selective electrodes. The results of monitoring stream water quality in this catchment in 2004 showed clear differences in the concentration of the ions of chloride, potassium, and sodium depending on discharge: chloride showed the simple washout of accumulated atmospheric input, potassium implied the washout from the stock in the shallow soil layer, and sodium indicated the effect of ion exchange and chemical weathering.