摘要:

The paper briefly reviews the status of titanium as an environmental pollutant and presents a new method suitable for the microdetermination of the metals in plants, animal tissues and waters. The method is based on extractive separation of titanium as its chelate with N-p-methoxyphenyl -2-furylacrylohydroxamic acid (MFHA) in chloroform or isoamyl alcohol and subsequent spectrophotometric or atomic absorption spectrometric determination. MFHA was chosen from nine new hydroxamic acids as detailed in the paper. The overall sensitivity of the spectrophotometric method with chloroform as extracting solvent i s better than 1 ppb (0.001 ppm). For atomic absorption spectrometric determination isoamyl alcohol is used as extracting solvent and a sensitivity of 0.2 ppm, which is ten times better than attained earlier, is achieved. There was excellent agreement between the results obtained by the two different instrumental methods.

ISSN:0003-2719    

DOI:10.1080/00032718708082589

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

High resolution capillary gas chromatographic analysis of the polychlorobiphenyls (PCBs) present in snapping turtle eggs, provided quantitative data on selected toxic congeners. The concentrations of these congeners have been converted into equivalent toxic concentrations of 2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD). The toxic equivalent factors (TEFs), necessary to effect this transformation were derived from EC50values (half the concentration of the toxic congener required to produce the maximum effect) for aryl hydrocarbon hydroxylase (AHH) induction associated with the corresponding toxic PCB congener or isomer. Summation of the resulting toxic equivalents provided a composite assessment of the toxlcity of the PCB mixture in terms of an equivalent concentration of TCDD.

ISSN:0003-2719    

DOI:10.1080/00032718708082590

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Higher order derivative techniques are mainly used in deconvoluting the overlapping absorption spectra of various analytes in their determination. The procedure utilizing higher order derivatives in molecular absorption spectrophotometry essentially are based on the formation of binary complex viz. metal reacting with a chromogenic reagent. This paper reports a fourth order derivative spectrophotometric procedure for the determination of traces of cobalt based on the liquid-liquid extraction of ternary ion - asociation complex -cobalt, 1, 10-phenanthroline, rose bengal into chloroform. The developed procedure is simple, rapid, reliable and allows the determination of as low as 6 ppb of cobalt in high purity rare earth oxides and salts.

ISSN:0003-2719    

DOI:10.1080/00032718708082591

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A new simple and accurate method for molecular weight estimation of oligomers by reversed-phase liquid chromatography was developed and has been proposed to use in the investigation of bio-oligomers. Capacity factors (k′) of 24 peptides and proteins ranging in molecular weight from 200 to 70000 were measured independently under isocratic eluting conditions with slightly different acetonitrile contents in the mobile phase. Profiles of plots of the log k' values of the peptides and proteins against the acetonitrile contents were on straight lines with different slopes. These slopes were characteristic for each oligomer and found to be proportional to the two/thirds power of the molecular weight. This elution behavior of oligomers in reversed-phase liquid chromatography can be explained in terms of the solvophobic theory. The estimated molecular weights of several bio-oligomers were more accurate than those obtained by size-exclusion chromatography. when the range of molecular weights was limited from 103to 2×104.

ISSN:0003-2719    

DOI:10.1080/00032718708082592

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A new type of membrane for ion sensitive field effect transistors (ISFET's) made by plasma polymerization has been proposed for electrode material. Tetrafluoroethylene, chlorobenzene, acetonitrile pure and doped with iodine served as monomers. Some structural features of the plasma polymer membranes are analyzed by ESCA- and IR- methods. Ion sensitivity and long term stability of the membrane are examined.

ISSN:0003-2719    

DOI:10.1080/00032718708082593

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The response of an ion-selective electrode can be amplified by connecting the cell, which is composed of an ion-selective electrode and a reference electrode, in series. For a cell using 1, 2 or 3 valinomycin electrodes connected in series, the response slopes to 1 × 10−5−1 × 10−1M K+were 58, 116 and 174 mV/activity decade (a.d.) at 25°C, respectively. This amplification method would especially be useful for accurate determinations with electrodes in the range of low concentrations outside the Nernstian response or for determinations of polyvalent ions, in which both cases exhibit small emf response changes in changing the ion concentration.

ISSN:0003-2719    

DOI:10.1080/00032718708082594

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A new class of fully reversible biosensors, utilizing a layer of monoclonal antibodies trapped at the sensing surface of an immobilized-antigen membrane, is shown to be suited for continuous monitoring of antigen levels. The model sensor described gives a potentiometric response to the hapten 2,4-dinitrophenol (DNP) at micromolar concentration levels through competitive interaction with monoclonal anti-DNP antibodies held within the sensor tip. The proposed design yields a reusable, reagentless antigen sensor with good analytical precision and an operating lifetime of at least 17 days.

ISSN:0003-2719    

DOI:10.1080/00032718708082595

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Electrochemical incorporation of enzyme molecules into the growing matrix of platinum black particles is employed for the microfabrication of the enzyme electrode. Two electrochemical processes, i.e., electrochemical adsorption of enzyme molecules and electrolytic (reductive) deposition of metallic microparticles from its complex compound, are simultaneously carried out by using a microelectrode whose diameter is below 50 μm. A glucose sensor, a glucose oxidase-incorporated microelectrode, demonstrates high performance with high sensitivity and fast responsiveness.

ISSN:0003-2719    

DOI:10.1080/00032718708082596

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A hydrogen peroxide electrochemical sensor, coupled with two enzymes (ß -galactosidase and glucose oxidase) immobilized on the surface of the sensor covered with a cellulose acetate dialysis membrane (cut off 100), is proposed for the analysis of lactose in raw milk. The resulting hydrogen peroxide formation is measured with a platinum electrode polarized at +650 mV versus Ag/AgCl. The procedure developed is very simple and the short response time permits its use in assaying milk samples on dairy farms.

ISSN:0003-2719    

DOI:10.1080/00032718708082597

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A high performance liquid chromatography analysis method has been developed for the quantitation of 2′,3′-dideoxyinosine (DDI) in plasma. Proteins were precipitated from plasma samples with acetonitrile containing the internal standard, 6-methylaminopurine riboside. The treated samples were evaporated to dryness and reconstituted in mobile phase for the analysis. Separation of the components was achieved on a 5 μm octadecylsilane column with ultraviolet detection at 254 nm. The method was validated at nine concentrations between 0.015 and 150 μg/mL. Using 500 μL of human plasma, the limit of quantitation was 120 ng/mL and the limit of detection was 60 ng/mL. The mean intra-day precision of the method was 1.6%. The mean accuracy of the method was within 2% of the actual values. This method is currently being used for pharmacokinetic studies in the rat.

ISSN:0003-2719    

DOI:10.1080/00032718708082598

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor