Uranyl ion, UO22+, in an aqueous sodium hydrogen carbonate solution of pH 4 - 8 (source phase) was simultaneously and selectively transported into a dilute sulfuric acid solution (receiving phase) through a membrane (chloroform, bulk) containing a lipophilic ion-associate of methyltrioctylammonium ion and hydroxycalix[n]arene-p-sulfonate ion, 2n (n = 6, 8), MTA+-2n, as a metal carrier. The rate of transport increased in proportion to the concentrations of UO22+ in the source phase and carrier in the membrane and along with an increase in the temperature of the system. The rate was also increased along with an increase in the pH of the source phase. None of the other metal ions were transported, or obstructed the transport of UO22+, while the presence of large amounts of sodium hydrogencarbonate and sodium chloride in the source phase interfered with the transport by causing a delay in the start of transport.
Regioselectively hetero-labeled hosts, 6A-pyrenebutylate-6X-tosyl-modified γ-cyclodextrins (X = B or H, C or G, D or F, and E for γ-1, γ-2, γ-3, and γ-4, respectively), were synthesized in order to investigate their chemo-sensor properties for applications to organic compounds, such as bile acids and terpenes. The hosts (γ-1, γ-2, γ-3, and γ-4) exhibit pure monomer fluorescence. The guest-induced fluorescence emissions of these hosts were suppressed in the presence of guests. The extent of fluorescence variations of these hosts with guests was recognized as a manifestation of the sensing ability of the hosts. A sensing parameter (ΔI/I0, where I and I0 are the fluorescence intensities in the presence and absence of a guest and ΔI = I0-I) was used to describe the sensing ability of these hosts. Host γ-analogs were able to detect progesterone, ursodeoxycholic acid, chenodeoxycholic acid, and (-)-borneol with high sensitivity. The behaviors of the appended moieties of these hosts during the formation of host-guest complexes were studied using induced circular dichroism (ICD) spectra, fluorescence spectra and the MM2-energy-minimized structure. The host γ-analogs exhibited different ICD spectra patterns before and after the addition of ursodeoxycholic acid. The guest-induced variations of ICD and the fluorescence spectra and MM2-minimized structures suggest that the pyrene and tosyl moieties move by altering the spatial relationship between them, in which the pyrene moiety works as a hydrophobic cap and the tosyl moiety is speculated to act as a spacer.
A novel spectrophotometric method for the determination of trace molybdenum in the presence of a large amount of tungsten was developed. This proposed method was based on the formation of a green charge-transfer polyoxometalate, molybdo-11-tungstophosphate-3,3′,5,5′-tetramethylbenzidine-N-propanesulfonic, which was solubilized and stabilized in a PVA medium; the wavelength of the maximum absorption was at 660 nm. Beer’s law was obeyed in the Mo concentration range of 0.04 - 1.6 µg ml-1. The molar absorptivity was 1.35 × 104 l mol-1 cm-1. The developed method avoided the interference of WVI, and was conveniently applied to analyses of some tungsten ores containing MoVI with satisfactory results.
Hemoglobin (Hb) was entrapped in a phosphatidylcholine (PC) film and immobilized at a pyrolytic graphite (PG) electrode surface. Its electron-transfer reactivity and enzyme activity were characterized by employing electrochemical methods. It was observed that Hb exhibited direct electrochemistry as well as enzyme-like activity towards the electro-catalytic reduction of NO in PC film. An unmediated, reagentless nitrogen oxide (NO) biosensor was accordingly prepared. Experimental results revealed that the peak current related to NO was linearly proportional to its concentration in the range of 1.0 × 10-7 - 3.0 × 10-4 mol/L. The detection limit was estimated to be 1.0 × 10-7 mol/L. Considering its good stability, nice selectivity and easy construction, this biosensor shows great promise for the rapid determination of traces of NO.
A novel triiodide ion-selective electrode based on a clotrimazole-triiodide ion pair as a membrane carrier was prepared. It has a linear response to triiodide from 8 × 10-6 to 5 × 10-3 M with a slope of -68.9 mV per decade and a detection limit of 5 × 10-6 M. The electrode response is independent of the pH of the solution in the pH range 2 - 9. It has a very short response time and can be used for at least 3 months without any considerable divergence in the potentials. The proposed sensor revealed very good selectivities for I3- over a variety of other anions. It was used as an indicator electrode in the potentiometric titration of triiodide ions and in an indirect potentiometric determination of clotrimazole in pharmaceutical preparations.
A new, simple, sensitive, low cost and rapid potentiometric method for direct determination of ultra trace amounts of sodium dodecyl sulfate (SDS) with a new DS--selective electrode is reported. The electrode was prepared by electropolymerization of aniline in acidified DS- ion on the surface of a Pt electrode. The cyclic voltammetry (CV) was used for electropolymerization of polyaniline (PA) in the potential range of -200 to +1000 mV vs. Ag/AgCl. This sensor showed a Nernstian behavior (59.0 ± 2.3 mV/decade) over a very wide linear range (1.0 × 10-9 - 3.0 × 10-6 M) with a detection limit of 1.0 × 10-9 M. The response time of the electrode was 15 s for 1.0 × 10-7 M of analyte; the electrode can be used for 4 weeks without any major deviation. This electrode can be used in the pH range of 3.5 - 9.8. The selectivity of electrode to DS- over some organic, inorganic and anionic surfactants was investigated with the fixed primary ion method. The results show that the electrode is highly selective to DS- ion over other ions. The proposed electrode was applied to the determination of DS- in real samples.
The composition of the commercial reagent Cyanex 302® was investigated by GC-MS. Mass spectrometric studies allowed us to confirm that bis(2,4,4-trimethylpentyl)monothiophosphinic acid is the major compound and that a considerable amount of tris(2,4,4-trimethylpentyl)phosphine oxide is also present. The study also revealed that the extractant has three minor components. These were identified as bis(2,4,4-trimethylpentyl)phosphinic acid, bis(2,4,4- trimethylpentyl)phosphine oxide and bis(2,4,4-trimethylpentyl)dithiophosphinic acid. The mass spectra of these compounds are discussed and some fragmentation processes are postulated.
Coimmobilization of β-galactosidase and glucose oxidase in a redox polymer, polyvinylferrocenium perchlorate (PVF+ClO4-), led to the development of an enzyme electrode for the determination of lactose. The amperometric response of the electrode was measured at +0.70 V vs. SCE, which was due to the electrooxidation of enzymatically produced H2O2. The effects of the substrate and buffer concentrations as well as the pH on the electrode response were elucidated.
The silica-based Fe(III)-protoporphyrin and Zn-tetraphenylporphyrin stationary phases were examined for the HPLC separation of anions. The retention of nine common inorganic anions as well as benzoate anion (BA) and its hydroxy analogues (HBA) was examined using tartrate, acetate, and succinate eluents. The retention factors of inorganic anions on the FeProP stationary phase were in the order Cl- < NO3- < ClO4- < I- < SCN- and for organic anions benzoate < p-hydroxybenzoate < m-hydoxybenzoate < o-hydroxybenzoate. The retention factors of organic anions examined for a ZnTPP column were in the order p-HBA < m-HBA < BA < o-HBA.
A renewable amperometric immunosensor based on a graphite-paraffin-Schistosoma japonicum antibody (SjAb) biocomposite electrode has been prepared for the detection of Schistosoma japonicum antigen (SjAg). Competitive ELISA was employed involving HRP-SjAg as a tracer and 3,3′,5,5′-tetramethylbenzidine (TMB) as a substrate. The product of an enzyme catalytic reaction was detected at +0.1 V (vs. Ag/AgCl reference electrode) for measuring the amount of HRP-labeled SjAg binding to the electrode surface. The assay conditions were optimized, including the amount of SjAb loading in the electrode and HRP-SjAg in the incubation solution, the pH of the measuring solution and the incubation time. The measuring range was 0.5 - 30 µg/ml under the optimum conditions. Rabbit serum samples of different infection degree were measured, which demonstrated that the immunosensor meets the demands of clinical analysis. It exhibits some advantages, such as simplicity of fabrication, rapidity of measurement, and satisfactory sensitivity and reproducibility.
4-(3,17 β-Dihydroxyestra-1,3,5(10)-trien-6α- and 6β-yl)amino-7-nitro-2,1,3-benzoxadiazoles have been synthesized and characterized as fluorescent probes for use in a receptor assay and/or a homogeneous immunoassay for estradiol. The fluorescence intensities are strongly dependent upon the solvent polarity used. The intensities in water were reduced to less than 1% of those in ethyl acetate, and a blue shift was also observed in polar solvents. The quenched fluorescence in aqueous solution was recovered by adding bovine serum albumin or an anti-estradiol antibody. Adding intact estradiol inhibited the fluorescence recovered by the antibody.
A simple, rapid and sensitive spectrophotometric method has been proposed for the determination of cerium(IV) using a phenothiazine derivative, propionyl promazine phosphate (PPP). This method is based on the formation of a red-colored radical cation upon a reaction of PPP with cerium(IV) in a phosphoric acid medium having maximum absorbance at 513 nm. Beer’s law is valid over the concentration range of 1 - 11 µg/ml with a Sandell’s sensitivity value of 16.14 ng/cm2. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys. Other phenothiazine derivatives viz. butaperazine dimaleate and propericiazine were also used for the determination of cerium(IV).
In this study a headspace spectrophotometric method is proposed for analysis of dichloromethane and isobutyl methyl keton (IBMK) residues in the ampicillin powder. Ampicillin is dissolved in 1 M NaOH in the vessel of an arsenic analyzer unit of an atomic absorption spectrophotometer. After 3-min stirring, the headspace has flowed by air into the flow-through cell and its absorbance is read at 196 nm, as emitted by a selenium hollow cathode lamp. The absorbance of the headspace is read in two cases (in the presence and absence of MnO4- ion). In the former case, the absorbance is only related to dichloromethane; in the latter, it is related to both solvents. By this method both solvents are determined in the ampicillin samples. The obtained results are compared with gas chromatography (GC) data. These results have good agreement. The proposed method is very rapid, selective and repeatable. Other solvents present, such as isopropyl alcohol, ethylacetate and triethylamine, are not interfering.
The interaction of Fast Green FCF (FCF) with proteins (including bovine serum albumin (BSA), human serum albumin (HSA), pepsin (Pep) and α-chymotrypsin (Chy), and lysozyme (Lys)) was characterized by enhanced resonance light-scattering (RLS) measurements using a common spectrofluorometer. The enhanced RLS signals of FCF by proteins at 279.0 nm were obtained, and the mechanism of the RLS enhancement was considered in terms of the effects of the pH and ionic strength on the interaction. It was found that the enhanced RLS intensities were in proportion to the concentrations of proteins in the range of nanogram levels, displaying that the present assay is much more sensitive than the reported RLS methods, with the limits of determination being 4.54, 0.6, 22.8, 4.32 and1.75 ng/ml for BSA, HSA, Pep, Chy, and Lys, respectively.