Trace Analysis of Lead and Copper Ions in Fish Tissue Using Paste Electrodes

Abstract

DNA was immobilized onto a carbon nanotube surface through cyclic voltammetry, in which paste electrode (PE) was subjected to lead and copper trace ion analysis. Optimized conditions for square‐wave stripping voltammetry were then searched. The results indicated three other linear working ranges—3–21 mg l^?1, 2–16 µg l^?1, and 3–17 ng l^?1 Pb(II) Cu(II)—within an accumulation time of 190 s in 0.1‐M ammonium phosphate electrolyte solutions of pH 10.0. At the optimized conditions, the detection limit (S/N) was pegged at 0.4 ng l^?1 (1.93×10^?12 M Pb(II) and 6.29×10^?12 M Cu(II)). And the relative standard deviation at 10 mg l^?1 Pb(II) and Cu(II) was a 0.074 and 0.069% precision, in 15 measurements. The method can be applied to assays of fish tissue.     

Spectrophotometric Determination of Nitrite in Water Samples with 4‐(1‐Methyl‐1‐Mesitylcyclobutane‐3‐yl)‐2‐Aminothiazole

Abstract

A simple, sensitive, and specific spectrophotometric method for the measurement of nitrite in water has been developed and optimum reaction conditions along with other analytical parameters have been evaluated. The azo dye, 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐(p‐N,N‐dimethylazobenzene)‐1,3‐thiazole was synthesized with the reaction of 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐aminothiazole and N,N‐dimethyl aniline in acidic medium. Obtained azo dye has been characterized by infrared (IR), ¹H nuclear magnetic resonance (NMR), and microanalysis methods. The dye shows an absorption maximum at 482 nm. The method is optimized for acid concentration, pH, amount of reagents required, time, and interfering species. All the determinations were carried out at this wavelength throughout the work. At an analytical wavelength of 482 nm, Beer's law is obeyed over the concentration range 0.05 to 2.00 µg nitrite per mL analyte. The molar absorptivity, Sandell's sensitivity, and relative standard deviation are 2.03×10⁴ L mol^?1 cm^?1±251.3 (95%), 2.28×10^?3 µg cm^?2, and 2.74% (n=10), respectively. The detection limit of the method is 0.012 µg ml^?1 of nitrite ion. The method was succesfully applied to the determination of nitrite in tap water and lake water.     

A Novel Hg(II) PVC Membrane Sensor Based on Simple Ionophore Ethylenediamine Bis‐Thiophenecarboxaldehyde

Abstract

A mercury (II) ion‐selective polyvinyl chloride (PVC) membrane sensor based on ethylenediamine bisthiophenecarboxaldehyde (EDBT) as a novel nitrogen‐ and sulfur‐containing sensing material was successfully developed. The ionophore was produced through Schiff's base formation between ethylenediamine and 2‐thiophenecarboxaldehyde. These two reagents have the advantages of low cost and simple chemical compounds. Ortho‐nitro phenyl pentyl ether (o‐NPPE) as solvent and sodium tetraphenyl borate (NaTPB) as a lipophilic salt were chosen. The sensor exhibited a good linear response of 30.0±0.4 mV per decade within the concentration range of 10^?7–10^?2 and a detection limit of 7.0×10^?8 mol L^?1 Hg(II). The sensor showed good selectivity and fast response for the mercury (II) ion with respect to some alkali, alkaline earth, transition, and heavy metal ions. The EDBT–based sensor was suitable for aqueous solutions of pH range from 2.0 to 4.5. It can be used for about 3 months without any considerable divergence in potential. The formation constant of ionophore complex with Hg(II) ion was calculated by using the segmented sandwich membrane method. The structure of both the ionophore and its Hg(II) complex were examined using infrared spectra and elemental analysis. The proposed sensor was applied for the determination of Hg(II) content in some dental amulgum alloys and as an indicator electrode for potentiometric titration of Hg(II) ion with EDTA solution, as well as with I^?, OH^?, and IO₃ ^? ions. In addition, the solubility products of the previous ions were determined by using this sensor.     

Biosensor for Hydrogen Peroxide Based on Chitosan and Nanoparticle Complex Film–Modified Glassy-Carbon Electrodes

Abstract

A biosensor for hydrogen peroxide was fabricated by co-immobilizing cadmium telluride (CdTe) nanoparticles, chitosan, and hemoglobin (Hb) matrix. There was a pair of nearly reversible redox peaks around ?0.360 V, and the electrochemical behavior of Hb was a surface-controlled process, with an electron-transfer rate constant of 1.36 s^?1 and surface coverage of 2.62 × 10^?10 mol cm^?2. Fourier transform infrared (FT-IR) spectra and ultraviolet–visible (UV-vis) spectra indicated that Hb sustained its natural conformation. It was demonstrated that Hb in the matrix kept its bioactivity and exhibited catalytic ability toward H₂O₂, with a response ranging from 7.44 × 10^?6 to 6.95 × 10^?4 M and a detection limit of 2.23 × 10^?6 M.     

A New Flow‐Injection Chemiluminescence Method for the Determination of Acyclovir and Gancyclovir

Abstract

A rapid and sensitive flow‐injection chemiluminescence (FI‐CL) method, which is based on the CL intensity that generated from the redox reaction of Ce(IV)‐rhodamine B in H₂SO₄ medium, for the determination of acyclovir and gancyclovir is described. For acyclovir, the determination range is 3×10^?8 g mL^?1–7×10^?5 g mL^?1, with 1.56×10^?8 g mL^?1 as its determination limit. During 11 repeated measurements for 1×10^?6 g mL^?1 acyclovir, the relative standard deviation was 2.08%. For gancyclovir, the determination range was 5×10^?8 g mL^?1–7×10^?5 g mL^?1, with 2.35×10^?8 g mL^?1 as its determination limit. The relative standard deviation is 2.83% with 11 repeated measurements of 1×10^?6 g mL^?1 gancyclovir. This method can be successfully used to determine the content of acyclovir and gancyclovir in injections, acyclovir in eye drops, and, maybe, also for other ciclovirs.     

Post‐chemiluminescence Method of the Determination of Loperamide Hydrochloride in Human Plasma and Pharmaceutical by Using Dichlorofluorescein as Chemiluminescence Reagent

Abstract

A post‐chemiluminescence (PCL) was observed when loperamide hydrochloride solution was injected into the reaction mixture after the finish of CL reaction of alkaline N‐Chlorosuccinimide (NCS) and dichlorofluorescein. Based on this phenomenon, a simple, sensitive and fast flow injection PCL method was established for the determination of loperamide hydrochloride. The possible mechanism for the PCL reaction was discussed via the investigation of the CL kinetic characteristics, the CL spectra, the fluorescence spectra. The PCL intensity responded linearly to the concentration of loperamide hydrochloride in the range 8.0×10^?10 to 6.0×10^?7 g · ml^?1 with a linear correlation of 0.9995. The detection limit was 4×10^?10 g · ml^?1. The relative standard deviation was 2.4% for 4.0×10^?8 g · ml^?1 loperamide hydrochloride (n=11). This method has been applied to the determination of loperamide hydrochloride in human plasma and pharmaceutical samples with satisfactory results.     

Antibacterial,Antioxidant and Binding Studies of Some Novel Diaryl Sulphide Derivatives

Abstract

A series of novel acyclic and cyclic diaryl sulphides was synthesized from 2,2′-dithiobenzoic acid. The various diaryl sulphides were characterized by use of spectral (IR, ¹H and ¹³C NMR, ESI/MS) and elemental analyses. The antimicrobial activities of the compounds were evaluated in terms of their minimum inhibition concentration (MIC) against a panel of clinical isolates bacteria and were found to possess only moderate antimicrobial activities. N,N′-Bis(2-hydroxyphenyl)-2,2′-thiodibenzamide (13), exhibiting a hydroxy group at the phenyl ring, was the most active antimicrobial agent within the series, with MIC values of 0.05 mg mL^–1 and 10 mg mL^–1 against Staphylococcus aureus and Bacillus cereus, respectively. The antioxidant efficiency of the diaryl sulphides was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity with 13 being the most active compound. The interaction of 2,2′-thiodibenzanilide, N,N′-bis(2-methylphenyl)-2,2′-thiodibenzamide, and N,N′-bis(2-hydroxyphenyl)-2,2′-thiobenzamide with guanine, glutamic acid, and urea were studied quantitatively with binding constants ranging from 1 × 10³ M^?1 to 2.7 × 10⁴ M^?1.     

Determination of L‐Vesamicol in Serum Samples Using Enantioselective,Potentiometric Membrane Electrodes Based on Antibiotics

Abstract

Enantioselective, potentiometric membrane electrodes (EPMEs) based on antibiotics are proposed for the enantioanalysis of L‐vesamicol. A carbon paste was modified with antibiotics (vancomycin, teicoplanin, and teicoplanin modified with acetonitrile), as chiral selectors. The EPMEs based on antibiotics were reliably used for enantiopurity tests of L‐vesamicol using the direct potentiometric technique. The following linear concentration ranges: 1.0×10^?6–1.0×10^?4, 1.0×10^?6–1×10^?3 and 1×10^?7?1×10^?2 mol/L; and detection limits: 1.1×10^?7, 9.6×10^?8, and 3.6×10^?8 mol/L were determine for vancomycin, teicoplanin, and teicoplanin modified with acetonitrile–based EPMEs, respectively. The proposed EPMEs were applied for the enantioanalysis of L‐vesamicol in urine samples.     

Mercaptopyridine-substituted indium,zinc, and metal-free phthalocyanines: nonlinear optical studies in solution and on polymer matrices

In this article, the nonlinear optical characterizations and optical limiting properties of metal-free (2), zinc (3), and indium (4) tetra 4-(2-mercaptopyridine) phthalocyanines are discussed. Nonlinear optical properties of the samples were evaluated using Z-scan at 532 nm and 10 ns pulse in CHCl₃, and doped on poly(bisphenol A carbonate) (PBC) thin films. Thin films for 2, 3, and 4 are represented as 2-PBC, 3-PBC, and 4-PBC, respectively. We observed two-photon absorption (2PA) and strong reverse saturable absorption as the dominant mechanisms at nanosecond laser excitation in solution and thin films. By virtue of the magnitude of absorption coefficients and other nonlinear optical parameters estimated in this work, sample 4 was found to exhibit strongest nonlinear optical properties followed by 3, while 2 is the weakest nonlinear absorber of the studied samples. Large third-order susceptibility (1.46 × 10^?9 esu and 7.74 × 10^?10 esu) and hyperpolarizability (2.13 × 10^?28 and 8.37 × 10^?29 esu) were estimated for 4-PBC and 3-PBC, respectively. Our studies show that these molecules are suitable candidates for practical passive optical limiters.     

Adsorptive Cathodic Stripping Voltammetry Determination of Ultra Trace of Lead in Different Real Samples

Abstract

In the present work, an adsorptive cathodic stripping voltammetric method using a hanging mercury drop electrode (HMDE) was described in order to determine the ultra trace of lead ions with carbidopa in different real samples. The method is based on accumulation of lead metal ion on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. The instrumental and chemical parameters were optimized. The optimized conditions were obtained in pH of 8.4, carbidopa amount of 1.0×10^?6 M, accumulation potential of 0. 0 V, accumulation time of 100 s, scan rate of 100 mV/s and pulse height of 50 mV. The relationship between the peak current versus concentration was linear over the range of 2.4×10^?10–4.8×10^?7 M. The limits of detection were 5.8×10^?11 M and the relative standard deviation at 4.8×10^?10, 2.1×10^?8, and 2.4×10^?7 M of lead ion were obtained 3.2, 2.9, and 2.7%, respectively (n=7).     

Enantioanalysis of S-Ketoprofen Using Enantioselective,Potentiometric Membrane Electrodes

Abstract

Maltodextrins with different dextrose equivalent (DE) values (maltodextrin I: DE 4.0–7.0; maltodextrin II: DE 13.0–17.0; maltodextrin III: DE 16.5–19.5) were used for the design of three enantioselective, potentiometric membrane electrodes (EPMEs) for the assay of S-ketoprofen. The linear concentration ranges for the proposed electrodes were 10^?10 to 10^?8, 10^?9 to 10^?5, and 10^?10 to 10^?7 mol/L, with slopes of 58.0, 58.67, and 58.93 mV/decades of concentration and limits of detection of 1.49 × 10^?8, 2.43 × 10^?8, and 4.19 × 10^?11 mol/L for EPMEs based on maltodextrin I, II, and III, respectively. The EPMEs showed high reliability and effectiveness for the enantioanalysis of S-ketoprofen raw material and its pharmaceutical formulations.     

A Novel Holmium(III) Membrane Sensor Based on N‐(1‐Thien‐2‐Ylmethylene)‐1,3‐Benzothiazol‐2‐Amine

Abstract

A novel plasticized membrane sensor for Ho(III) ions based on N‐(1‐thien‐2‐ylmethylene)‐1,3‐benzothiazol‐2‐amine (TBA) as a neutral carrier was prepared. The best performance was obtained with a membrane composition of 31% PVC, 61% benzyle acetate, 2% sodium tetra phenyl borate and 6% carrier. The electrode exhibits a Nernstian response for Ho(III) ions over a particular concentration range (1.0×10^?5?1.0×10^?2 M) with a slope of 19.7±0.2 mV decade^?1. The limit of the detection is 7.0×10^?6 M. The sensor has a response time of <15 s and a useful working pH range of 4.0–9.5. The proposed sensor discriminates relatively well towards Ho(III) ions with regard to common alkali, alkaline earth, and specially lanthanide ions. It was successfully applied as an indicator electrode in a potentiometric titration of Ho(III) ions with EDTA. It was also applied in determination of fluoride ions in a mouth wash preparation. The proposed sensor was applied for the determination of Ho(III) ion concentration in binary mixtures.     

Study on a Fluorometric Method for the Determination of Protein in Serum Using Quercetin‐Lanthanum (III)‐Sodium Dodecyl Benzene Sulfonate‐Protein System

Abstract

It was found that the fluorescence intensity of lanthanum (III) (La³⁺)‐quercetin (Qu) complex is greatly enhanced by proteins in the presence of sodium dodecyl benzene sulfonate (SDBS). Based on this finding, a new fluorimetric method for the determination of proteins was developed. Under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins in the range of 2.5×10^?8 to 1.0×10^?5 g/mL for bovine serum albumin (BSA), 5.0×10^?8 to 1.5×10^?5 g/mL for human serum albumin (HSA), and 1.0×10^?7 to 1.5×10^?5 g/mL for egg albumin (EA). Their detection limits (S/N=3) are 5.0×10^?9 g/mL, 7.0×10^?9 g/mL, and 2.1×10^?8 g/mL, respectively. The interaction mechanism was also studied.     

Europium(III)-Sensitized Chemiluminescence Determination of Ibuprofen in Pharmaceutical Preparations and Biological Fluids

Abstract

Chemiluminescence reaction of the system containing europium(III) ion, KMnO₄, Na₂SO₃, and ibuprofen was investigated for the determination of ibuprofen. The introduction of Eu(III) ion into the system of KMnO₄-Na₂SO₃-ibuprofen caused a significant increase in the chemiluminescence signal. The increment of the chemiluminescence signal is proportional to ibuprofen concentration in the range of 5.0 × 10^?8–5.0 × 10^?6 g/ml with a detection limit of 1 × 10^?8 g/ml. The relative standard deviation for 1.0 × 10^?7 g/ml ibuprofen solution was 1.7% (n = 11). The proposed method was successfully applied to determine ibuprofen in tablets and human plasma.     

Determination of 1‐Naphthol with Denatured DNA–Modified Pretreated Glassy Carbon Electrode

Abstract

A highly sensitive electrochemical biosensor for the detection of trace amount of 1‐naphthol was designed. Acid‐denatured DNA were immobilized onto the pretreated glassy carbon electrode (GCE(ox)) surface. Two well‐defined oxidation peaks were observed on the denatured DNA‐modified GCE(ox) at about +0.80 V and +1.10 V (vs. Ag/AgCl) in 0.10‐M acetate buffer (pH 5.0). The peak current of the guanine residue decreased with increasing concentration of 1‐naphthol. The optimum experimental conditions for the detection of 1‐naphthol were explored, and the calibration was linear for 1‐naphthol in the range of 1.0×10^?8?1.1×10^?6 M, with a correlation coefficient of 0.998. The limit of detection (LOD) was 5.0×10^?9 M (S/N=3).     

Potentiometric Dipyridamole Sensors Based on Lipophilic Ion Pair Complexes and Native Ionic Polymer Membranes

Abstract

A new spectrofluorimetric method was developed for the determination of trace amounts of lecithin. Using enoxacine (ENX)‐terbium ion (Tb³⁺) as a fluorescent probe, in a buffer solution at pH=5.80, lecithin can remarkably reduce the fluorescence intensity of the ENX‐Tb³⁺ complex at λ=545 nm; the reduced fluorescence intensity of the Tb³⁺ ion is proportional to the concentration of lecithin. Optimum conditions for the determination of lecithin were also investigated. The linear range and detection limit for the determination of lecithin were 1.96×10^?7–9.8×10^?6 mol l^?1 and 9.74×10^?8 mol l^?1. This method is simple, practical and relatively free of interference from coexisting substances, and can be successfully applied to assess lecithin in serum samples.     

Kinetic Spectrophotometric Determination of Thiols and Ascorbic Acid

Abstract

This paper describes a kinetic spectrophotometric method for the determination of L‐ascorbic acid (AA) and thiols (RSH). Absorbance of Fe(II)‐phen complex formed during the reaction of AA or RSH with Fe(III)‐phen was continuously measured at 510 nm by double‐beam spectrophotometer with flow cell. For determination some thiols, the catalytic effect of Cu²⁺ ions was used. AA and RSH can be determined in concentration ranges from 4.0×10^?6 to 4.0×10^?5 M and from 8.0×10^?6 to 8.0×10^?5 M, respectively. The applicability of the proposed method was demonstrated by determination of chosen compounds in pharmaceutical dosage forms.     

Application of Novel Praseodymium (III) PVC‐Membrane Electrode for Determination of Pr(III) Ions in Soil and Sediment Samples

Abstract

A novel Pr(III) ion‐selective polyvinyl chloride (PVC) membrane sensor, based on N,N‐bis(α‐methylsalicylidene)diethylenetriamine (BMT) as a new ionophore, has been prepared and studied. The electrode showed good selectivity for Pr(III) ion with respect to most common cations, including alkali, alkaline earth, transition, and heavy metal ions. This electrode has a wide linear dynamic range from 1.0×10^?6 to 1.0×10^?2 M with a Nernstian slope of 19.8±0.2 mV per decade and a low detection limit of 6.5×10^?7 M, in the pH range of 3.0–8.4, while response time was rapid (<15 s). As far as applications of the recommended sensor are concerned, first it was employed as an indicator electrode in the potentiometric titration of Pr(III) ions with EDTA. Second, it was effectively applied to the determination of concentration of Pr(III) ions in soil and sediment samples, and validation with CRMs.     

Mn(III) and Cu(II) complexes of 1-((3-(dimethylamino)propylimino)methyl) naphthalen-2-ol): Synthesis,characterization, catecholase and phenoxazinone synthase activity and DFT-TDDFT study

Two new complexes, [MnL₂](ClO₄) (1) and [CuL₂] (2) (where LH = (E)-1-((3-(dimethylamino)propylimino)methyl)naphthalen-2-ol), have been synthesized and characterized by spectroscopic techniques and their molecular structures are established by single-crystal X-ray diffraction study. Complex 1 adopts an octahedral geometry around the central manganese atom which is in + 3 oxidation state, whereas in complex 2, the Cu⁺² ion preferred a square pyramidal environment around it through the ligand donor atoms. Both complexes were tested for catecholase and phenoxazinone synthase activity. Complex 1 catalyzes the oxidation of 3,5-ditertiary-butyl catechol with a k_cat value of 6.8424 × 10² h^?1 in acetonitrile whereas the same for complex 2 is 3.7485 × 10² h^?1 in methanol. Phenoxazinone synthase activity was shown only by complex 2 having k_cat = 74.225 h^?1. Structures of both the title complexes have been optimized by means of DFT calculations. Experimental electronic spectra of the complexes have been corroborated by TDDFT analysis. Electrochemical investigations by means of cyclic voltammetry have been carried out to study the electron transfer processes in the complexes.     

Study on Chemiluminescence Assay of Surfactant PEG-400 Using Luminol–Hydrogen Peroxide System

Abstract

Based on the fact that nonionic surfactant polyethylene glycol-400 (PEG-400) catalyzed the chemiluminescence of luminol-H₂O₂ system, a novel and simple chemiluminescence method has been developed for the determination of PEG-400. Under the optimal conditions, the standard curve was Y = 198835X–2091.8, where the correlation coefficient (R) was 0.9999. The detection limit was 4 × 10^?5 g·ml^?1 PEG-400 and the linear range was 1.0 × 10^?4–4.0 × 10^?2g·ml^?1. The relative standard deviation was 3.2% at 2.0 × 10^?3 g·ml^?1 PEG-400 (n = 7). This method has been applied to the determination of PEG-400 in cosmetic samples with satisfactory results. Furthermore, the dynamics characteristic curve of PEG-400 in luminol-H₂O₂ system was compared to typical metallic ion and other surfactants. Moreover, the mechanism of the luminol-H₂O₂-PEG-400 chemiluminescence system was studied, assisted by fluorescence spectra and UV spectra.