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1.
Issa YM  Zayed SI 《Talanta》2006,69(2):481-487
New clobutinol (Clob) ion-selective polyvinyl chloride (PVC) membrane electrodes, based on the ion-associates of Clob with phosphotungstic acid or phosphomolybdic acid were prepared using dibutyl phthalate as plasticizing solvent. The electrodes were characterized in terms of membrane composition, temperature and pH. The sensors showed a near-Nernstian response over the concentration ranges (6.31 × 10−6)-(1.00 × 10−2) and (5.01 × 10−5)-(1.00 × 10−2) M in the case of clobutinol-phosphotungstate ((Clob)3-PT) applying batch and flow injection (FI) analysis, respectively, and (1.58 × 10−5)-(1.00 × 10−2) and (5.01 × 10−5)-(1.00 × 10−2) M in case of clobutinol-phosphomolybdate ((Clob)3-PM) for batch and FI analysis systems, respectively. The electrodes were successfully applied for the potentiometric determination of ClobCl in pharmaceutical preparation and urine in steady state and flow injection conditions. The electrodes exhibit good selectivity for Clob with respect to a large number of inorganic cations, sugars and amino acids.  相似文献   

2.
The limits of detection (3s) for ascorbic acid were 5×10−8 M with acidic potassium permanganate using both flow injection analysis (FIA) and sequential injection analysis (SIA) whereas the soluble manganese(IV) afforded 1×10−8 M and 5×10−9 M for FIA and SIA, respectively. Determinations of ascorbic acid in Vitamin C tablets were achieved with minimal sample pretreatment using a standard additions calibration and gave good agreement with those of iodimetric titration.  相似文献   

3.
New polymeric membrane (PME) and coated graphite (CGE) samarium(III)-selective electrodes were prepared based on isopropyl 2-[(isopropoxycarbothioyl) disulfanyl]ethanethioate as a suitable neutral ionophore. The electrodes exhibit Nernstian slopes for Sm3+ ions over wide concentration ranges (1.0×10−5 to 1.0×10−1 M for PME and 1.0×10−6 to 1.0×10−1 M for CGE). The PME and CGE have limits of detection of 3.1×10−6 and 5.0×10−7 M, respectively, and response times of about 20 s. The potentiometric responses are independent of the pH of the test solution in the pH range 4.0-7.0. The proposed electrodes revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The electrodes were successfully applied to the recovery of Sm3+ ion from tap water samples and also, as an indicator electrode, in potentiometric titration of samarium(III) ions.  相似文献   

4.
Acetaminophenol or paracetamol is one of the most commonly used analgesics in pharmaceutical formulations. Acetaminophen is electroactive and voltammetric mechanistic studies for the electrode processes of the acetaminophenol/N-acetyl-p-quinoneimine redox system are presented. Carbon nanotubes modified screen-printed electrodes with enhanced electron transfer properties are used for the study of the electrochemical-chemical oxidation mechanism of paracetamol at pH 2.0.Quantitative analysis of paracetamol by using its oxidation process (in a Britton-Robinson buffer solution pH 10.0) at +0.20 V (vs. an Ag pseudoreference electrode) on an untreated screen-printed carbon electrode (SPCE) was carried out. Thus, a cyclic voltammetric based reproducible determination of acetaminophen (R.S.D., 2.2%) in the range 2.5 × 10−6 M to 1 × 10−3 M, was obtained. However, when SPCEs are used as amperometric detectors coupled to a flow injection analysis (FIA) system, the detection limit achieved for paracetamol was 1 × 10−7 M, one order of magnitude lower than that obtained by voltammetric analysis. The repeatability of the amperometric detection with the same SPCE is 2% for 15 successive injections of 10−5 M acetaminophen and do not present any memory effect.Finally, the applicability of using screen-printed carbon electrodes for the electrochemical detection of paracetamol (i.e. for quality control analysis) was demonstrated by using two commercial pharmaceutical products.  相似文献   

5.
The feasibility of a newly synthesized Rh(III) complex, Rh[(trpy)(bpy)Cl](PF6)2, as a novel ionophore for the preparation of anion-selective polymeric membrane electrodes was tested. The ionophore exhibited anti-Hofmeister behavior with enhanced potentiometric selectivity toward thiocyanate ion compared to other anions. The influence of some experimental parameters such as membrane composition, nature and amount of plasticizer and additive and concentration of internal solution on the potential response of the SCN sensor were investigated. The electrode exhibits a Nernstian response for SCN over a wide concentration range (1.0 × 10−5 to 1.0 × 10−1 M) with a slope −58.7 ± 0.5 mV per decade and a detection limit of 4.0 × 10−6 M (0.23 ppm). It could be used in a pH range of 3.0-8.0 and has a fast response time of about 15 s. The proposed sensor was used for the determination of thiocyanate ions in real samples such as urine and saliva of smokers and nonsmokers and, as an indicator electrode, in potentiometric titrations of SCN ion.  相似文献   

6.
Tang B  Zhang L  Xu KH 《Talanta》2006,68(3):876-882
A new kind of near-infrared fluorescence agent, tricarbochlorocyanine dye (Cy.7.Cl), had been synthesized in house and used for near-infrared spectrofluorimetric determination of hydrogen peroxide (H2O2) by flow injection analysis (FIA) for the first time. The oxidation reaction of Cy.7.Cl with H2O2 occurred under the catalysis of horseradish peroxidase (HRP) and it was studied in detail. The possible reaction mechanism was discussed. Under optimal experimental conditions, fluorescence from Cy.7.Cl displayed excitation and emission maxima (ex/em) at 780 and 800 nm, respectively. The two linear working ranges were 1.86 × 10−7 to 4.11 × 10−7 mol L−1 and 4.11 × 10−7 to 7.19 × 10−6 mol L−1, respectively. The detection limit was 5.58 × 10−8 mol L−1 of H2O2. The effect of interferences was studied. The proposed method was successfully applied to the determination of hydrogen peroxide in rainwater, serum and plant samples.  相似文献   

7.
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.  相似文献   

8.
Five plastic membrane electrodes for the determination of dicyclomine hydrochloride (DcCl) were fabricated and fully characterized in terms of composition, life span, usable pH range, working concentration range and temperature. The membranes of these electrodes consist of dicyclominium-silicotungstate (Dc-ST), silicomolybdate (Dc-SM), phosphotungstate (Dc-PT), phosphomolybdate (Dc-PM) or tetraphenylborate (Dc-TPB) ion-associations dispersed in PVC matrix with dibutyl phthalate plasticizer. The electrodes showed near-Nernstian response over the concentration range of 4.0 × 10−6 to 1.0 × 10−2 M DcCl and applied to the potentiometric determination of dicyclominium ion in pharmaceutical preparations, serum, urine and milk in batch and flow injection (FI) conditions with average recoveries of 96.1-102.7% and relative standard deviation of 0.055-1.994%. The electrodes exhibit good selectivity for DcCl with respect to a large number of inorganic cations, organic cations, sugars and amino acids. The sensitivities of these electrodes are high enough to measure as low as 1.73 μg/ml of DcCl which permit the determination of the Ksp values of the ion-associates used. The proposed potentiometric methods offer the advantages of simplicity, accuracy, automation feasibility and applicability to turbid and colored sample solutions.  相似文献   

9.
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)2NO3] 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 NO3 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 NO3 in industrial wastewaters, fertilizers and pharmaceuticals. The results agree fairly well with data obtained by the standard spectrophotometric methods.  相似文献   

10.
Tsukatani T  Matsumoto K 《Talanta》2006,69(3):637-642
A flow-injection system for the quantification of pyruvate based on the coupled reactions of pyruvate decarboxylase (PDC) and aldehyde dehydrogenase (AlDH) was conceived and optimized. A co-immobilized PDC and AlDH reactor was introduced into the flow line. Sample and reagent (NAD+) were injected into the flow line by an open sandwich method and the increase of NADH produced by the immobilized-enzyme reactor was monitored fluorometrically at 455 nm (excitation at 340 nm). Linear relationships between the responses and concentrations of pyruvate were observed in the ranges of 2.0 × 10−5 to 1.5 × 10−3 M at the flow rate of 1.0 ml min−1 and 5.0 × 10−6 to 1.0 × 10−3 M at the flow rate of 0.5 ml min−1. The relative standard deviation for 10 successive injections was 0.95% at the 1.0 mM level. This FIA system for pyruvate was applied to the measurement of acetate, citrate and l-lactate.  相似文献   

11.
Nine monoazathiacrown ethers have been synthesized and explored as ionophores for polymeric membrane Ag+-selective electrodes. Potentiometric responses reveal that the ion-selective electrodes (ISEs) based on 2,2′-thiodiethanethiol derivatives can exhibit excellent selectivities toward Ag+. The plasticized poly(vinyl chloride) membrane electrode using 22-membered N2S5-ligand as ionophore has been characterized and its logarithmic selectivity coefficients for Ag+ over most of the interfering cations have been determined as <−8.0. Under optimal conditions, a lower detection limit of 2.2 × 10−10 M can be obtained for the membrane Ag+-ISE.  相似文献   

12.
High-performance liquid chromatography (HPLC) with tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection methodology is reported for the determination of the atypical antipsychotic drug quetiapine and the observation of its major active and inactive metabolites in human urine and serum. The method uses a monolithic chromatographic column allowing high flow rates of 3 mL min−1 enabling rapid quantification. Flow injection analysis (FIA) with tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection and HPLC time of flight mass spectrometry (TOF-MS) were used for the determination of quetiapine in a pharmaceutical preparation to establish its suitability as a calibration standard. The limit of detection achieved with FIA was 2 × 10−11 mol L−1 in simple aqueous solution. The limits of detection achieved with HPLC were 7 × 10−8 and 2 × 10−10 mol L−1 in urine and serum, respectively. The calibration range for FIA was between 5 × 10−9 and 1 × 10−6 mol L−1. The calibration ranges for HPLC were between 1 × 10−7-1 × 10−4 and 1 × 10−8-1 × 10−4 mol L−1 in urine and serum, respectively. The quetiapine concentrations in patient samples were found to be 3 × 10−6 mol L−1 in urine and 7 × 10−7 mol L−1 in serum. Without the need for preconcentration, the HPLC detection limits compared favourably with those in previously published methodologies. The metabolites were identified using HPLC-TOF-MS.  相似文献   

13.
The potentiometric behavior of coated wire electrodes based on dodecylbenzenesulfonate-doped polypyrrole (PPy-DBS) and hyamine as ion exchanger was investigated. The PPy-DBS was prepared electrochemically by anodic polymerization of pyrrole in the presence of DBS ions in aqueous solution and used as ionophore for construction of the sensor. Two types of coated wire electrodes made of PVC-PPy-DBS and PVC-Hyamine-DBS, plasticized with ortho-nitrophenyloctylether (o-NPOE) showed the Nernstian behavior (with respective calibration slopes of about 58 and 60 mV per decade) over the DBS concentration range of 3.0×10−6 to 1.1×10−3 M and 5.0×10−6 to 1.3×10−3 M, respectively. The influence of membrane composition, type of plasticizer, and pH of test solution on the potentiometric responses of the two electrodes was investigated. The potentiometric response was independent of the pH of test solution in the range 3-10. The response time of electrodes was fast (10 s for both types of electrode), and they can be used for at least 3 months without any significant change in potential. The proposed electrodes revealed very good selectivity for DBS ion over diverse inorganic and organic anions. The potentiometric selectivity coefficients for the PPy-DBS based electrode revealed a significant improvement as compared to the electrode made by conventional Hyamine-DBS (Hya-DBS) anion exchanger. The proposed electrode was used for determination of DBS ion in some commercial detergents. The results of the potentiometric determinations were in satisfactory agreement with those obtained by a standard method (two-phase titration).  相似文献   

14.
J. Ballesta Claver 《Talanta》2009,79(2):499-506
This paper presents an application of chromatographic separation based on an ultra-short monolithic column and chemiluminescent detection in an FIA type instrument manifold for the determination of four paraben mixtures: methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP). The separation is achieved in 150 s using two consecutive carriers: first 12% ACN:water that changes 75 s after injection to 27% ACN:water. The detection is based on the oxidation of the hydrolysis product of parabens, p-hydroxybenzoic acid, with Ce(IV) in the presence of Rhodamine 6G which evokes chemiluminescence of sufficient intensity to enable a sensitive determination of these species. After optimization of the variables involved, the analytical method is characterized, displaying the following values for concentration ranges, detection limits and precision, as relative standard deviation at low concentration (0.15 mg l−1)—MP: from 9.9 × 10−7 to 3.3 × 10−4 M; 1.9 × 10−8; 5.6%; EP: from 9.0 × 10−7 to 3.3 × 10−4 M; 2.8 × 10−8; 3.5%; PP: from 8.3 × 10−7 to 9.9 × 10−5 M; 2.3 × 10−8; 4.2%; and BP: from 7.7 × 10−7 to 9.9 × 10−5 M; 4.2 × 10−8 M; 6.2%. The method was applied and validated satisfactorily for the determination of these parabens in cosmetic samples, comparing the results against a liquid chromatography reference method.  相似文献   

15.
Membrane electrodes for the determination of glutathione   总被引:1,自引:0,他引:1  
Four glutathione (GSH)-selective electrodes were developed with different techniques and in different polymeric matrices. Precipitation-based technique with bathophenanthroline-ferrous as cationic exchanger in polyvinyl chloride (PVC) matrix was used for sensor 1 fabrication. β-Cyclodextrin (β-CD)-based technique with either tetrakis(4-chlorophenyl)borate (TpClPB) or bathophenanthroline-ferrous as fixed anionic and cationic sites in PVC matrix was used for fabrication of sensors 2 and 3, respectively.β-CD-based technique with TpClPB as fixed anionic site in polyurethane (Tecoflex) matrix was used for sensor 4 fabrication. Linear responses of 1 × 10−5 to 1 × 10−4 M and 1 × 10−6 to 1 × 10−3 M with slopes of 37.5 and 32.0 mV/decade within pH 7-8 were obtained by using electrodes 1 and 3, respectively. On the other hand, linear responses of 1 × 10−5 to 1 × 10−2 and 1 × 10−5 to 1 × 10−3 M with slopes of 47.9 and 54.3 mV/decade within pH 5-6 were obtained by using electrodes 2 and 4, respectively. The percentage recoveries for determination of GSH by the four proposed GSH-selective electrodes were 100 ± 1, 100.5 ± 0.7, 100 ± 1 and 99.0 ± 0.8% for sensors 1, 2, 3 and 4, respectively. Determination of GSH in capsules by the proposed electrodes revealed their applicability for determination of GSH in its pharmaceutical formulations. Also, they were used to determine GSH selectively in presence of its oxidized form (GSSG). Sensor 4 was successfully applied for determination of glutathione in plasma with average recovery of 100.4 ± 1.11%. The proposed method was compared with a reported one. No significant difference for both accuracy and precision was observed.  相似文献   

16.
I.M. Isa 《Talanta》2007,71(1):452-455
This paper describes the preparation of and experimentation undertaken by heterogeneous chitosan membrane as ion selective electrode for glutamate ion. The linearity response was obtained in the range of 1.0 × 10−5 to 1.0 × 10−1 M with a detection limit of 1.0 × 10−6 M. The performance of the electrode was found in the pH range of 4.0-8.0 at temperature 25 ± 3 °C. The response time was at 5-35 s and was useful for a period of more than 4 months. The selectivity values towards some anions indicates good selectivity over a number of interfering anions. No significant improvement of membrane performance over additional of plasticizers such as 2-NPOE, BEHA and DOPP. The electrodes gave sufficient Nernstian responses with the exception of membrane with 2-NPOE.  相似文献   

17.
Wang J  Wang L  Han Y  Jia J  Jiang L  Yang W  Sun Q  Lv H 《Analytica chimica acta》2007,589(1):33-38
Novel polyvinyl chloride (PVC) membrane electrodes based on triheptyl dodecyl ammonium iodide have been developed. In the presence of 12.5 mM H2O2, these electrodes are capable of determining molybdate(VI) ion. The electrodes exhibit near-Nernstian responses over a wide concentration range (2.0 × 10−6 to 5.0 × 10−3 M). The proposed electrodes demonstrate satisfying selectivity for molybdate(VI) ion in the presence of a wide variety of anions other than iodide, and can be used in the pH range 5.0-7.0. Moreover, the electrodes show an average response time of 2-3 min and can be used over a period of 2 months without any significant deviation being observed. In the light of our results, the response mechanism of the electrode is discussed and HMoO2(O2)2 is suggested as the response ion. The proposed electrode has been used to measure molybdenum in ore samples, and the results were in agreement with those obtained by means of ICP analysis.  相似文献   

18.
The construction and performance characteristics of different phosphate ion-selective electrodes are described. Three types of electrodes are demonstrated, namely screen-printed, carbon paste and the conventional PVC membrane electrodes. The cited electrodes are based on bisthiourea ionophores and show a considerable selectivity towards hydrogenphosphate with Nernstian slopes depending on the type of the electrode and the ionophore used. Matrix compositions of each electrode are optimised on the basis of effects of type and concentration of the ionophore as well as influence of the selected plasticizers. The screen-printed electrodes work satisfactorily in the concentration range 10−5 to 10−2 mol L−1 with anionic Nernstian compliance (32.8 mV/decade activity) and detection limit 4.0 × 10−6 mol L−1. The screen-printed electrodes show fast response time of about 2.2 s and exhibit adequate shelf-life (4 months). The fabricated electrodes can be also successfully used in the potentiometric titration of HPO42− with Ba2+.  相似文献   

19.
Zhen Hai Li  Koji Oshita 《Talanta》2010,82(4):1225-637
Flow-injection analysis system (FIA system), which was based on Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide, was developed for the determination of hydrogen peroxide. The chromotropic acid has a fluorescence measured at λem = 440 nm (emission wavelength) with λex = 235 nm (excitation wavelength), and the fluorescence intensity at λem = 440 nm quietly decreased in the presence of hydrogen peroxide and Fe(II), which was caused by Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide. By measuring the difference of fluorescence intensity, hydrogen peroxide (1.0 × 10−8-1.0 × 10−3 mol L−1) could be determined by the proposed FIA system, whose analytical throughput was 40 samples h−1. The relative standard deviation (RSD) was 1.03% (n = 10) for 4.0 × 10−8 mol L−1 hydrogen peroxide. The proposed FIA technique could be applied to the determination of hydrogen peroxide in rain water samples.  相似文献   

20.
Novel polymeric membrane (PME) and coated graphite (CGE) silver-selective electrodes based on two recently synthesized mixed azathioether crowns containing a 1,10-phenanthroline sub-unit were prepared. The electrodes reveal a Nernstian behavior over quite wide Ag+ ion concentration ranges with a very low limits of detection (LOD) (i.e. down to 1.0×10−8 M for CGEs and 8.0×10−7 M for PMEs). The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.0. The electrodes possess advantages of low resistance, very fast response time, relatively long lifetimes and, especially, good selectivities relative to a wide variety of other cations. The electrodes were used, as indicator electrodes, in the potentiometric titration of silver ion and in the determination of Ag+ in waste water, photographic emulsion and radiographic and photographic films.  相似文献   

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