Perchlorate selective membrane electrodes based on a platinum complex

Three platinum(II) complexes were synthesized and studied to characterize their ability as an anion carrier in a PVC membrane electrode. The polymeric membrane electrodes (PME) and also coated glassy carbon electrodes (CGCE) prepared with one of these complexes showed excellent response characteristics to perchlorate ions. The electrodes exhibited Nernstian responses to ClO₄ ⁻ ions over a wide concentration range from 1.5 × 10⁻⁶ to 2.7 × 10⁻¹ M for PME and 5.0 × 10⁻⁷ to 1.9 × 10⁻¹ M for CGCE with low detection limits (9.0 × 10⁻⁷ M for PME and 4.0 × 10⁻⁷ M for CGCE). The electrodes possess fast response time, satisfactory reproducibility, appropriate lifetime and, most importantly, good selectivity toward ClO₄ ⁻ relative to a variety of other common anions. The potentiometric response of the electrodes is independent of the pH of the test solution in the pH range 2.0–9.0. The proposed sensors were used in potentiometric determination of perchlorate ions in mineral water and urine samples. Correspondence: Ahmad Soleymanpour, Department of Chemistry, Damghan Basic Science University, Damghan, Iran.     

Hydrophilic sensor membrane based on cation-selective protic chromoionophore

The first potassium optode based on a protic chromoionophore immobilized in a hydrogel matrix is presented. The highly selective protic chromoionophore consists of a cryptohemispherand moiety and a trinitroanilino chromophore part. The acidifying power of potassium ions over sodium ions is 0.6 pH units. This correlates with the findings in solution. In contrast to several crown and aza-crown based chromophores the highly pre-organized moiety allows ion detection even in aqueous environment. The detection limit for potassium ions at pH 7.7 is 5 microM.     

Hydrophilic sensor membrane based on cation-selective protic chromoionophore

The first potassium optode based on a protic chromoionophore immobilized in a hydrogel matrix is presented. The highly selective protic chromoionophore consists of a cryptohemispherand moiety and a trinitroanilino chromophore part. The acidifying power of potassium ions over sodium ions is 0.6 pH units. This correlates with the findings in solution. In contrast to several crown and aza-crown based chromophores the highly pre-organized moiety allows ion detection even in aqueous environment. The detection limit for potassium ions at ¶pH 7.7 is 5 μM.     

Optical pH sensor based on Calcon immobilization membrane

An optical pH sensor was developed by immobilizing Calcon on a porous cellulosic polymer film. The color of the membrane in acidic to basic medium changes from pink to blue, which can be used for determination of pH by spectrophotometry. The sensor response to the pH changes at two wavelengths 510 and 670 nm was investigated. The optical sensor can be used for repetitive and reversible pH measurement in the pH range of 4–9 with a response time of 5 min at 510 nm. The relative standard deviation (R.S.D) was less than 0.51% for seven times alternative measurements of pH from 7 to 8. The sensor was successfully applied to the determination of pH in tap and waste water samples.     

Perchlorate-selective membrane electrode based on a new complex of uranil

A potentiometric ion-selective electrode based on new compound, as a carrier, has been successfully developed for detection of perchlorate anion in aqueous solution. Within the perchlorate ion concentration range 1.0×10^–6 to 1.0 mol L^–1 the electrode had a linear response with a Nernstian slope of 60.6±1.0 mV per decade . The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot was 8.0×10^–7 mol L^–1. The proposed electrode has fairly a good discriminating ability towards ClO₄^– ion in comparison to other anions. The sensor has a response time of 10 s and can be used for at least 2 months without substantial divergence in potential. It was successfully applied to direct determination of perchlorate in urine and water.     

Ammonium ion sensor based on immobilized nitrifying bacteria and a cation-exchange membrane

The ammonium ion sensor is based on nitrifying bacteria isolated from activated sludge. The sensor comprises a cation-exchange membrane, an alkaline solution layer (pH 10), a gas-permeable membrane, an immobilized microbial membrane, and an oxygen electrode. This novel combination provides accurate amperometric determinations of ammonium ions in aqueous solutions within 7 min in the range 10^-4– 4.5 × 10^-2 M. Volatile amines or other ions do not interfere. The relative error is within 4% and the sensor can be used continually for more than 10 days.     

Glucose sensor based on a field-effect transistor with a photolithographically patterned glucose oxidase membrane

A photopolymer solution consisting of polyvinylpyrrolidone and 2,5-bis(4′-azido-2′-sulfobenzal)cyclopentanone is used to make a patterned glucose oxidase membrane for a FET-glucose sensor by photolithography. A small patterned glucose oxidase membrane, 0.2 mm wide and 1 mm long, is made on the gate surface of an ISFET by developing a photocross-linked glucose oxidase membrane with aqueous 1–3% glutaraldehyde solution. The optimum composition of the enzyme/photopolymer solution is described. The sensor with the patterned membrane showed linear response to glucose concentration from 0.3 to 2.2 mM and useful response up to 5 mM.     

Amperometric enzyme sensor for glucose based on graphite paste-modified electrodes

Amperometric enzyme electrode for glucose is described based on the incorporation of glucose oxidase (GOD) into graphite paste modified with tetracyanoquinodimethane (TCNQ). The incorporated enzyme exhibits high activity and long-term stability over the earlier TCNQ-based glucose sensor (1). The sensor provides a linear response to glucose over a wide concentration range. The response time of the sensor is 15-50 sec, and the detection limit is 0.5 mM. Stable response to the substrate was obtained during a period of 35 d. Application of the sensor in the plasma analysis is reported.     

Sulfate-selective PVC membrane electrode based on a strontium Schiff's base complex

A strontium Schiff's base complex (SS) can be used as a suitable ionophore to prepare a sulfate-selective PVC-based membrane electrode. The use of oleic acid (OA) and hexadecyltrimethylammonium bromide (HTAB), as additives, and nitrobenzen (NB), dibutyl phthalate (DBP) and benzyl acetate (BA) as solvent mediators, were investigated. The best performance was observed with a membrane composition PVC: NB: SS: HTAB of 30%: 62%: 5%: 3% ratio. The resulting sensor works well over a wide concentration range (1.0 x 10(-2)-1.0 x 10(-6) M) with a Nernstian slope of -29.2 mV per decade of sulfate activity over a pH range 4.0-7.0. The limit of detection of the electrode is 5 x 10(-7) M. The proposed sensor shows excellent discriminating ability toward SO4(2-) ions with regard to many anions. It has a fast response time of about 15 s. The membrane electrode was used to the determination of zinc in zinc sulfate tablets. The sensor was also used as an indicator electrode in the potentiometric titration of SO4(2-) against barium ion.     

基于脱乙酰基魔芋葡甘聚糖固定酶的葡萄糖传感器

制备了脱乙酰基魔芋葡甘聚糖(d-KGM)的溶胶-凝胶,用红外光谱表征了其脱乙酰基前后的结构转化.探讨了d-KGM溶胶-凝胶的制备条件对其成膜性能及酶固定化的影响.在此基础上将d-KGM用于电极表面葡萄糖氧化酶的固定,制备了相应的葡萄糖传感器,并对传感器的工作条件进行了优化.所制备的传感器灵敏度为240 nA/mmol/L,线性范围为0.1～8 mmol/L,表观米氏常数KM为19.6 mmol/L,稳定性好,寿命长.实验结果表明d-KGM是一种可用于生物传感器中酶固定化的优良材料.     

Thallium-selective sensor with a membrane based on Tl4HgI6 ionic conductor

Tl₄HgI₆ solid electrolyte with a high ionic component of conductivity was synthesized for developing a thallium-sensitive sensor. The main sensor characteristics (tilt angle, detection limit, selectivity, pH range, potential drift) of the new thallium sensor were determined. The time stability of its operation and various ways of its application for determining thallium ions in solutions are demonstrated.     

Determination of uranium in water based on enzyme inhibition using a wireless magnetoelastic sensor

The aim of this paper is to develop a wireless magnetoelastic sensing method for the determination of uranium in water based on the inhibitory effect of uranyl cation to α-amylase. In this method, a wireless sensor used for detecting uranium was fabricated by immobilizing a layer of starch gel on the surface of a magnetoelastic foil. When the sensor was in a solution containing α-amylase, the α-amylase catalyzed the hydrolyzation of starch, causing a resonance frequency shift of the sensor. Meanwhile, the catalytic hydrolyzation of starch was inhibited by uranium presented in the above solution, resulting in a decrease in the resonance frequency shift of the sensor. Consequently, the amount of uranium could be determined by measuring the resonance frequency shift. The influence of manifold variables on the determination was investigated in details. A linear range was found to be 9.2 to 103.5?µg?L^?1 under optimal conditions with a detection limit of 3.6?µg?L^?1. The method was applied to the determination of uranium in environmental water samples with satisfactory results.     

Cobalt(II)-selective membrane sensor based on a [Me2(13)dieneN4] macrocyclic cobalt complex

A new poly(vinyl chloride)-based membrane was fabricated with the cobalt(II) complex of 2,4-dimethyl-1,5,8,11-tetraazacyclotrideca-1,4-diene [Me₂(13)dieneN₄] as an ion carrier. The membrane composition was Co²⁺ complex/PVC/NaTPB/DBP 15:50:15:20 (w/w). The sensor exhibited a Nernstian response for Co²⁺ ions over a wide concentration range (7.94×10⁻⁶–1.0×10⁻¹ M) at pH 2.5–7.0, a response time of 10 s, and it could be used for 3 months without any significant divergence in potential. The proposed membrane sensor exhibited good selectivity for Co²⁺ over a wide variety of other metal ions and in mixtures containing up to 25% (v/v) non-aqueous content. The sensor was successfully used as an indicator electrode in the potentiometric titration of Co²⁺ with EDTA and the direct determination of Co²⁺ in real samples.     

Enzyme electrode for glucose based on an iodide membrane sensor

The construction of a new type of enzyme electrode for the potentiometric determination of glucose is reported. The electrode response is based on the enzymecatalyzed reactions: The highly selective iodide sensor monitors the local decrease in the iodide activity at the electrode surface. The properties of the above reactions were examined kinetically, with flow-stream techniques and potentiometric detection. The glucose electrode constructed and the use of flow-stream experiments with two iodide sensors provided accurate and convenient glucose determinations in the absence of some oxidizing and reducing agents.     

A novel ethacrynic acid sensor based on a lanthanide porphyrin complex in a PVC matrix

Lanthanide porphyrin complexes synthesized by a solid state method were used to prepare a novel ethacrynic acid (EA) sensor. The sensor, based on pentane-2,4-dionato(meso-tetraphenylporphinato)terbium [TbTPP(acac)] with an optimized membrane composition, exhibits a Nernstian response to EA- ion in the concentration range 7.4 x 10(-6)-1.0 x 10(-1) mol l-1 with a pH range from 3.2 to 6.8 and a fast response time of 30 s. The electrode shows improved selectivity towards EA- ion with respect to common co-existing ions compared with the previously reported EA sensor. As electroactive materials, lanthanide porphyrin complexes show better potentiometric response characteristics than copper porphyrin complexes. The effect of solvent mediators and lipophilic ion additives was studied and the experimental conditions were optimized. The electrode was applied to the determination of EA in human urine samples with satisfactory results.     

Serine-selective membrane probe based on immobilized anaerobic bacteria and a potentiometric ammonia gas sensor

A new class of bioselective membrane probes using anaerobic bacteria is introduced with the successful construction of a L-serine-selective probe consisting of Clostridium acidiurici cells coupled to a potentiometric ammonia gas sensor. The intact cells containing the enzyme serine dehydratase are physically immobilized at the electrode surface in conjunction with iron(II) stearate, which is shown to enhance response characteristics. The potential vs. log concentration plot is linear from 1.6 × 10^-2 to 1.8 × 10^-4M serine with an average slope of 54 mV/decade and response times of 3–5 min. Optimal behavior of the probe is retained even in non-deaerated media for at least three days, and significant interference is posed only by L-glutamine. Quantitative conversion of serine is demonstrated over the linear concentration range, suggesting possible analytical or clinical applications for these probes utilizing anaerobic bacteria     

Uranium-sensitive electrodes based on the uranium-di(octylphenyl)phosphate complex as sensor and alkyl phosphate as mediator in a PVC matrix membrane

The properties of uranium-sensitive electrodes based on membranes containing uranium di-(4-octylphenyl)phosphate as sensor have been determined, in presence of different phosphates as mediators. The electrode prepared from tritolyl phosphate as mediator was found to give a response of 30 mV/decade over a range of uranium concentration. Interference by Sr(2+), Ba(2+), Ca(2+) and F(-) was also studied, by the mixed solution method. Fluoride interferes severely, by complexation of the UO(2+)(2) ion.     

Preparation of ethambutol-copper(II) complex and fabrication of PVC based membrane potentiometric sensor for copper

Copper(II) complex of ethambutol (I) was prepared and used in the fabrication of Cu(2+) selective ISE membrane. The membrane having Cu(II)-ethambutol complex (I) as electroactive material, along with sodium tetraphenylborate (NaTPB) as anion discriminator, dioctylphthalate (DOP) as plasticizer in poly(vinyl chloride) (PVC) matrix in the percentage ratio 6:2:190:200 (I:NaTPB:DOP:PVC) (w/w) gave a linear response in the concentration range 7.94x10(-6) to 1.0x10(-1) M of Cu(2+) with a slope of 29.9+/-0.2 mV per decade of activity and a fast response time of 11+/-2 s. The sensor works well in the pH range 2.1-6.3 and could be satisfactorily used in presence of 40% (v/v) methanol, ethanol and acetone and is selective for copper over a large number of cations with slight interference from Na(+) and Co(2+) if present at a level 1.5x10(-5) and 6.5x10(-5) M, respectively. It works well over a period of 6 months and can also be used as indicator electrode for the end point determination in the potentiometric titration of Cu(2+) against EDTA as well as in the determination of Cu(2+) in real samples.