Showing papers in "Analytical Sciences in 1987"

Recognition of Largest Common Structural Fragment among a Variety of Chemical Structures

Abstract: A computer program, called MAXFIT, has been developed for the automated recognition of the largest common substructure among a diverse set of chemical structures This approach is based on a substructure search technique Five different search levels which were defined with weighted graph representation of the chemical structures are available in the search The search level can be specified interactively Applications to structure-activity problems, including sweetners and opiates are presented to illustrate the abilities of the program

Matrix Effects in Inductively Coupled Plasma Mass Spectrometry

Abstract: Suppression of analyte signals by various concomitant elements was investigated. In addition to the ionization interference by easily ionizable elements reported previously, signal suppression by heavy matrix elements was found to be significant. The interference trend followed the order of atomic weight of the matrix elements, i.e., the larger the atomic weight, the severer the suppression effect. Ion scattering by collision with matrix atoms or ions in the course of ion traveling from the sampling orifice is proposed as the mechanism of the matrix effect.

Ion-association reagents. A review.

Abstract: Ion-association reagents are widely used for analytical chemistry. The ion-associable cation or anion should be univalent, bulky and charge-dispersed. The reagents are classified by their shape: plane, sphere, chain and polymer types. The ion-associable cation and anion can combine with each other to form the ion-associate in water. This phenomenon has been used for gravimetric and volumetric analyses and for extraction-spectrophotometry of a trace component. Several examples of specific and sensitive extraction-spectrophotometries are illustrated. The polymer type reagent can react with the counter-charged poly-electrolyte to form a precipitate quantitatively, and it can be used for colloid titration. Metachromasy phenomenon is based on the formation of the ion-associate of colored ion-associable cation or anion with counter-charged colorless ion-association reagents to show distinguished color changes.

Acylation of Aminopropyl-Bonded Silica Gel for Liquid Chromatography

Abstract: Acylation of aminopropyl-bonded silica gel for liquid chromatography with acid chlorides was investigated in terms of the pore structure of silica gel and the molecular size of acylating agents. Three types of aminopropyl bonded silica gel with different pore sizes, 40, 60 and 100A, were acylated with various acid chlorides. Silica gel with larger pore size generally reacted with a larger amount of acid chloride than that with smaller pore size. This trend was more remarkable when acylating agents with larger molecular size were used. Thus, the density of ligand on the silica surface can be controlled by the combination of pore structure of silica gel and molecular size of acylating agents. Unreacted amino groups on silica surface after the acylation with stearoyl chloride could be made to react when benzoyl chloride, with a smaller molecular size, was used as a second acylating agent.

A novel amperometric ammonia sensor.

Abstract: A novel amperometric ammonia sensor was designed in which an amperometric ammonium-ion selective polyvinyl chloride)-nitrobenzene gel electrode containing dibenzo- 18-crown-6 was covered with a gas-permeable membrane. This sensor gave a current response proportional to the ammonia concentration in the range from 2 to 200μmol dm-3. We examined the dependence of the current response on electrode potential, thickness of the internal- solution layer, and pH of the sample solution. The results were well explained by theoretical equations.

Liquid-Liquid Extraction of Metal Ions by Cyclic and Acyclic Tetrathio Ethers

Abstract: Liquid-liquid extraction of metal ions with several cyclic and acyclic tetrathio ethers was examined using picrate as the anion of the ion pair. Three new acyclic compounds were synthesized. Class b metal such as Ag(I), Cu(I), Pd(II) and Hg(II) were extracted well, whereas class a and class ab metals were not extracted at all except for Cu(II) with each ligand, regardless of its being cyclic and acyclic tetrathio ethers. The extraction behavior of copper(I) was stoichiometrically examined. Copper(I) was extracted with five ligands(L) into 1, 2-dichloroethane as ion pair compounds, [Cu(I)L]+Pic-. The extraction constant Kex for copper(I) with each ligand was determined. Copper(I) is most effectively extracted with the tetrathio ether of the o-xylene derivative. It becomes clear that the configuration of ligands is reflected in the Kex value.

Preconcentration of silver(I) with 2-mercaptobenzothiazole loaded silica gel

Abstract: A complexing material, 2-mercaptobenzothiazole loaded silica gel (MBT/SG), was prepared for rapid preconcentration of trace amounts of silver(I) from water samples. Silver(I) was quantitatively retained on the MBT/SG from solution of pH 0-6.3 in batch experiments, while the untreated silica gel captured only 5% of the element in the solution. The retention capacity of the loaded gel was about 8.8mg Ag g-1 (81.5μmol g-1) at pH 4.0. The mole ratio of MBT to silver was about 8.3. Silver was quantitatively retained on the MBT/SG column at a high flow velocity (18.8cm min-1). The silver retained on the column was completely eluted with 10-15cm3 of 0.1mol dm-3 nitric acid containing 2% thiourea, and directly determined by one-drop atomic absorption spectrometry. Silver contents of near-shore seawater were determined by the present method.

Determination of 1β-Hydroxylated Bile Acids and Related Compounds in Human Biological Fluids by Gas Chromatography-Mass Spectrometry

Abstract: A highly sensitive and specific quantitative assay of the 1β-hydroxylated bile acids and related compounds has been developed by gas chromatography-selected ion monitoring of their methyl ester-trimethylsilyl ether derivatives using the deuterium labeled internal standards: [2H7] DCA, [2H7] CA, [2H5] 3β-hydroxy- and [2H6] 3β, 12α-dihydroxy-5-cholen-24-oic acids. Calibration curves for these bile acids are useful over the range of 0.01-100μg in serum (0.2 ml), urine (5ml), or lyophilized meconium (1mg). Recoveries of the bile acids and their conjugates ranged from 92 to 101% of the added amounts of their standard samples. In the analysis of bile acids in human meconium by the developed method, novel 1β, 3α, 7α-trihydroxy- (II) and 1β, 3α, 7α, 12α-tetrahydroxy- (IV) 5β-cholan-24-oic acids were determined in significant amounts of 0.24μg/mg (5.3% of the total bile acids) and 0.27μg/mg (6.3%), respectively.

Distribution of Nickel(II), Cadmium(II) and Copper(II) Chelates of 2-(2-Pyridylazo)-5-methylphenol in Two Phases Separated from Micellar Solution of Nonionic Surfactant

Abstract: Several metal chelates of 2-(2-pyridylazo)-5-methylphenol (PAP-5-Me) were extracted from an aqueous phase into a surfactant phase which was separated from a micellar solution of poly(oxyethylene)=4-nonylphenyl=ether with oxyethylene units of 7.5 (PONPE-7.5). On the basis of the distribution curves for the respective chelates, the partition constants of the neutral chelates were determined at 293K at an ionic strength of 0.1 (NaCl). The partition constants were considerably smaller than those expected from the regular solution theory. The partition constants were also dependent upon the kind of metal ions. This fact is probably due to such an ordered structure as liquid crystal in the surfactant phase which can differentiate the size of the metal chelates.

Supporting Electrolytes for Voltammetric Study of Ion Transfer at Nitrobenzene/Water Interface

Abstract: The polarizable potential range was determined by cyclic voltammetry for the interface between an aqueous solution of lithium chloride or magnesium sulfate and a nitrobenzene solution of various electrolytes: tetrabutylammonium salts of tetraphenylborate, tetrakis(4-fluorophenyl)borate, tetrakis(4-chlorophenyl)borate, and tetrakis[3, 5- bis(trifluoromethyl)phenyl]borate, and tetrapentyl- and tetrahexylammonium salts of tetraphenylborate. The anodic and cathodic limits of polarizable potential range were discussed with reference to the standard ion-transfer potentials of the supporting-electrolyte ions.

Fiber-Optic pH Sensor with Monolayer Indicator

Abstract: A fiber-optic pH sensor has been constructed by immobilizing fluorescein isothiocyanate (FITC) on the end surface of the optical fiber. The pH response is reversible in the range 4.0-6.9, precision being±0.1. Due to implantation of FITC as a monolayer, the intrinsic response time is less than 10ms.

Determination of Oral Hypoglycemic Biguanides by High Performance Liquid Chromatography with Fluorescence Detection

Abstract: A sensitive and specific method for the analysis of oral hypoglycemic biguanides, metformin, buformin, and phenformin, was developed by use of high performance liquid chromatography (HPLC) with fluorometric detection. These biguanide drugs are converted to 2-alkylguanidino-1H-phenanthro[9, 10-d]imidazole derivatives by pre-column fluorescence labeling with 9, 10-phenanthraquinone (PQ) in an alkaline medium. The derivatives are separated on a reversed′phase column with 0.1M phosphate buffer (pH 2.5) containing 75 (v/v)% acetonitrile. Monosubstituted guanidines which exist in biological fluids also react with PQ in the same reaction conditions as the biguanides to form a fluorescent product, 2-amino-1H-phenanthro[9, 10-d]imidazole (API). However, they do not interfere with the analysis of the Biguanides in the elution system. The lower detection limits of biguanides added to serum are 0.2ng for metformin and 0.4ng for both buformin and phenformin, per 10μl of injection volume. The recoveries of 0.1μg biguanides added to 0.5ml of serum are in the range 96-102%.

Spectrophotometric Determination of Anionic Surfactants in River Water with Cationic AZO Dye by Solvent Extraction- Flow Injection Analysis

Abstract: Anionic surfactants in water were determined by a spectrophotometric flow injection technique coupled with solvent extraction. The ion associate which formed between an anionic surfactant and an cationic azo dye was extracted into an organic solvent and the absorbance was measured. The carrier was distilled water, and the reagent solution contained an cationic azo dye and sodium sulfate, the pH of which being adjusted to 5 with acetate buffer. A phase separator with a poly(tetrafluoroethylene) porous membrane (0.8μm pore size) was used to separate the organic phase. Six derivatives of cationic azo dyes and several extracting solvents were examined; a pair of 1-methyl-4-(4-diethylaminophenylazo)- pyridinium cation and chloroform turned out best. The sampling rate was 30 samples per hour. Calibration graphs were linear up to 2×10(-6)M or 3×10(-5)M of anionic surfactant when injection volume was 300 or 100μl, respectively. The relative standard deviation(n=10) was 1.5% for 300μl of 1×10(-6)M sodium dodecylsulfate. The detection limit was as little as 1×10(-8)M of anionic surfactant. Anionic surfactants in river water were determined satisfactorily.

Power of Detection and Accuracy in Elemental Trace Analysis

Abstract: Today, there exists a demand for analytical methods and procedures with absolute power of detection down to the pg-range for numerous elements in complex matrices. They should enable either to detect very low element concentrations in bulk samples or to acquire exact data on elemental distributions on the micro scale. With decreasing absolute amounts to be determined in real samples, detectability and reliability are in increasing discrepancy with the onsequence that analytical results become unreliable or wrong and thus very often particularly uneconomic. The fast evaluation of analysis results for lower and lower concentrations or amounts to be determined is limited by a rapid increase of systematic errors of a physical, but predominantly of a chemical nature. In the attempt, for instance, to properly derive concentrations from intensities, great difficulties are often encountered. This basic problem occurs at the ng-level and still far more for analyses at the pg-level. The solution of this analytical problem is not a general one but is obtained by special strategies in each individual case. In problem-orientated work involving extreme trace analyses, the reliability and economy of a procedure will therefore remain incalculable until it will be possible to recognize and eliminate the sources of systematic errors and to confirm the analytical results by independent procedures. The strategies leading to the best results for elemental determinations at ng-and pg-levels will be generally discussed and demonstrated by examples of the determination of Hg, Se, Tl and precious metals.

Surfactant-selective electrode based on plasticized poly(vinyl chloride) membrane and its application.

Abstract: The surfactant-selective electrode based on the poly(vinyl chloride) membrane plasticized with o-nitrophenyl octyl ether shows the Nernstian response to anionic surfactants as well as to cationic ones, e.g., the dodecylsulfate ion and the dodecyltrimethyl ammonium ion. The response time of the electrode is in the order of a few seconds. The electrode is highly selective to the dodecylsulfate ion over inorganic anions. The dodecylsulfate ion selective electrode was applied to the successive potentiometric detection of surfactants by high performance liquid chromatography. Four alkylsulfates were successfully detected with the electrode, after being separately eluted with water-methanol mixture through the reversed phase packing column. The electrode was shown to be useful for the determination of critical micelle concentrations of surfactants in the presence of electrolytes.

Conditions for a unique solution in factor analysis of overlapped Raman spectra of two components

Abstract: Conditions for uniquely separating the true spectra of individual components from the overlapped Raman spectra were examined by factor analysis. Whether the unique separation is possible or not depends upon the information contained in the data-set of the sample spectra. Unique solutions were obtained for two component Raman spectra under the following conditions. Case 1), two components each have a pure wavenumber and their pure samples exist; case 2), two components each have pure wavenumber; case 3), two pure samples exist; and case 4), one component has a pure wavenumber and its pure sample exists. Here, the pure wavenumber means the wavenumber at which only one component has a definite Raman intensity and the other components have zero intensities.

Determination of hydrogen peroxide with phenol and 4-aminoantipyrine by the use of a resin modified with manganese−tetrakis(sulfophenyl)porphine

Abstract: An anion-exchange resin, Amberlite IRA 900 modified with manganese-tetrakis(sulfophenyl)porphine (MnTPPSr), was used in place of peroxidase for the determination of hydrogen peroxide by the following enzyme-re-action: 2H2O2+phenol+4-aminoantipyrine → quinoid dye(λmpx=505nm)+4H2O. The calibration curve was linear in the range from 5μg to 50μg of hydrogen peroxide with a relative standard deviation of 1.05% (n=10).The absorbance of the quinoid dye formed by the use of Mn-TPPSr reached approximately 80% of that obtained by the control peroxidase method. The activity of MnTPPSr did not deteriorate over repeated uses.Only slight interferences of foreign substances were found except for the case of ascorbic acid.

Application of "Clean-up" Cartridge for Gas Chromatographic Determination of Di- and Tri-n-butyltin in Fish

Abstract: A gas chromatographic method is presented to determine traces of di- and tri-n-butyltin compounds in fish by use of an innovative clean-up cartridge. The cartridge used was packed with a moderately sulfonated low capacity cation exchange resin. The organotin compounds in fish tissue were extracted with hydrochloric acid-ethanol solution as their chlorides, transferred to an ethylacetate/hexane phase by liquid-liquid extraction, and the organic layer was concentrated with a rotary evaporator. The organotin chlorides were trapped on the resin by passing through the cartridge. The sampled cartridge was washed successively with ethanol, water and sodium chloride solution. The trapped organotin compounds were converted to their hydrides by passing a sodium borohydride ethanol solution through the cartridge, and these hydrides were eluted with 1/1 hexane/ethanol. The eluted organotin hydrides were extracted with hexane by shaking the eluate with water and hexane. The hexane layer was subjected to gas chromatographic separation, and identified by mass spectroscopy. The di- and tri-n-butyltin compounds in a fish sample could be determined as their chlorides with 2.7-4.8% relative standard deviations in the range 0.1-2.0μg/g. The detection limits of di- and tri-n-butyltin compounds as their chlorides were 3ng/g and 8ng/g for 10g of the sample.

Molecular structure and extraction behavior of silver (I)-13,14-benzo-1,4,8,11-tetrathiacyclopentadec-13-ene picrate complex.

Abstract: The X-ray crystallographic analysis of silver(I)-13, 14-benzo-1, 4, 8, 11-tetrathiacyclopentadec-l3-ene picrate (Ag-Bz- TTCP-Pic) was carried out. The molecular structure of its complex cation is discussed in connection with its solvent extraction behavior. The Ag-Bz-TTCP cation complex is not the simple 1:1 monomer complex cation, [Ag(bz-ttcp)]+, but the 2:2 dimeric complex cation, [Ag2(bz-ttcp)2]2+. Each silver(I) ion has the coordination number 5 and binds with five sulfur atoms: four sulfur atoms in one Bz-TTCP molecule and one sulfur atom in another Bz-TTCP, to form a distorted square pyramidal configuration. Thus two silver(I) ions are sandwiched between two Bz-TTCP molecules so that they look as if they were surrounded with two cyclic polythioether rings and two benzene rings. The charge on two silver(I) ions is delocalized on the dimeric complex. Thus the formation of the ion pair complex with two picrate anions is so stabilized that silver(I) will be almost completely extracted.

Instrumental neutron activation analysis of vehicle exhaust particulates as environmental reference material.

Abstract: Trace elements in a vehicle exhaust particulates environmental reference material (NIES No. 8) prepared by the National Institute for Environmental Studies were determined by an instrumental neutron activation analysis method (INAA). The vehicle exhaust particulates samples (ca. 150-550mg) were irradiated by neutrons for a short time (30s) and a long time (5h) at Musashi Institute of Technology Research Reactor (MITRR). Samples were irradiated by two methods: namely, thermal neutron irradiation without cadmium filter and epithermal neutron irradiation with cadmium filter. Activated samples were measured by four methods: γ-ray spectrometry, anticoincidence counting, coincidence counting and low energy photon spectrometry using a planar Ge detector LEPS). Concentrations of 52 elements were determined by these irradiation and counting methods.

Determination of bismuth in environmental samples by hydride generation-atomic absorption spectrometry

Abstract: The determination of trace amounts of bismuth in environmental samples was investigated by hydride generation-atomic absorption spectrometry. For a simpler procedure, an argon-hydrogen flame was used instead of the graphite furnace originally proposed by lee. Under the analytical conditions proposed here, the detection limit was 1ng as bismuth (S/N=2) and the precision was 1.5% (n=7). Analytical results are presented for sediments, seawater, and some standard reference materials.

Fluorometric determination of guanidino compounds by high performance liquid chromatography using water-soluble 9,10-phenanthrenequinone-3-sulfonate

Abstract: A water-soluble 9, 10-phenanthrenequinone-3-sulfonate was synthesized as a fluorogenic reagent which reacted with guanidino group in an alkaline solution. The reagent was used for the determination of guanidino compounds by high performance liquid chromatography where the mobile phase contained the fluorogenic reagent. Several guanidino compounds were separated within 20min on a Nucleosil C8 column (3μm, 75mm×4.6mm i.d.) by an isocratic, reversed phase and ion-pair chromatography and detected as fluorophores derived from condensation with the reagent in an alkaline solution. The chromatographic system, in which the mobile phase contained the reagent, was simple because only two pumps were required to deliver the mobile phase and the alkaline solution. The relative standard deviation (within-run, n=10) and the limit of detection for the assay of the compounds were 3.00% and 0.1nmol, respectively. This method was applied to the determination of guanidino compounds in serum obtained from patients on haemodialysis therapy.

Separation of radionuclides from water by magnesium oxide adsorption

Abstract: L'oxyde de magnesium, comme celui de zirconium, ou de fer, ou de calcium, peut etre utilise pour enlever par adsorption les elements radioactifs presents dans l'eau, ceci a des fins de decontamination. Les avantages de la separation avec l'oxyde de magnesium sont exposes ici (il peut etre utilise avec plus de quarante radioisotopes)