摘要:

The use of fluorescence difference decay curves was explored as a way to isolate the decays of components in a complex system. Time-correlated single photon methodology allows one to subtract a “reference” curve from a “sample” curve from a “sample” curve to yield a difference decay curve. To test the feasibility of this method, a model 3-component system (6-carboxyfluorescein, pyranine, and 1-dimethyl-aminoaphtalene-5-sulfonate) was examined. From its complex fluorescence decay curve, the individual decays were obtained by subtracting the appropriate binary solution decay curves. These difference curves coincided with those of the single component systems. Stringent requirements included: use of the same instrumental settings for all solutions, low counting efficiency, avoidance of inner filter effects, absence of energy transfer, and lack of chemical interaction between components. The difference decay method was applied to: 1. Sequential dansylation of serum albumin. Lifetimes of the first two dyes bound are longer than those of the third. 2. Dynamic quenching of quinine fluorescence by chloride ion. When the reference differs from the sample only by having a shorter lifetime, the difference decay curve has a characteristic shape. 3. Quenching of intrinsic protein fluorescence by acrylamide. Bovine serum albumin and liver alchol dehydrogenase were examined. Of the two tryptophans in each protein, one was preferentially quenched and its decay curve was obtained by difference.

ISSN:0003-2719    

DOI:10.1080/00032718408065301

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Knowledge of possible variability in the dissociation constant (pKa) among preparations of phenol red-polyacrylamide was needed during development of a fiber optic probe to monitor fetal blood pH. Determination of the pKa through absorbance-wavelength spectra on opaque 50% glycerol suspensions of phenol red-resin required second derivative spectrophotometry. The apparent pKa was 8.0 for both the dye and several batches of its resin derivative. Spectrophotometry of comparable aqueous solutions of phenol red yielded a pKa of 7.78 ± 0.02, at μ=0.25M.

ISSN:0003-2719    

DOI:10.1080/00032718408065302

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The nuclear magnetic resonance chemical shifts of the lower polyphosphate compounds are strongly dependent on the hydrogen ion concentration of the solution, both absolutely and relative to each other. At an optimum pH, the chemical shifts of pyrophosphate and tripolyphosphate will be most widely separated, and these two compounds can be determined in the presence of each other and in the presence of higher polyphosphates. The univariate simplex procedure found the optimum pH in ten trials, but required two more measurements to define the minimum width of the maximum response region, pH 8.4 to 8.7

ISSN:0003-2719    

DOI:10.1080/00032718408065303

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Determination of traces of impurities in chloro-silanes and high purity silica are important in the preparation of semiconductor grade silicon. The author have developed an indirect method for the determination of phosphorus in these materials. Phosphorus is extracted as phosphoantimonyl molybdate complex in methyl isobutyl ketone. The concentration of phorphorus is calculated by determining the concentration of antimony by atomic absorption spectrophotometer as antimony and phosphorus are present in 1:1 molar ratio in the complex. The method is selective and enables the determination of 0.1 ppm of phosphorus.

ISSN:0003-2719    

DOI:10.1080/00032718408065304

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A simple, sensitive and rapid spectrophotometric method has been developed for the determination of osmium using cyclohexane 1,3-dione bisthiosemicarbazone mono-hydrochloride (1,3-CHDT.HCl). The method is based on the instantaneous colour reaction between 1,3-CHDT. HCl and osmium(VIII) in sodium acetate—acetic acid buffer medium (pH range 3–6). The osmium complex shows maximum absorbance at 375 nm and considerable absorbance at 510 nm. Although the complex formed between platinum(IV) and reagent (1,3-CHDT.HCl) shows maximum absorbance at 375 nm, it does not show any absorbance at 510 nm. Simultaneous determination of osmium and platinum is carried out when present alone and in presence of other foreign (associated) ions. Some physico-chemical and analytical characteristics of osmium and platinum complex are described. Interference of various foreign ions have studied and osmium is estimated selectively in the presence of constituents of platinum ores.

ISSN:0003-2719    

DOI:10.1080/00032718408065305

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The amounts of five polynuclear aromatic hydrocarbons-fluoranthene, pyrene, benzo(a)anthracene, benzo(k)fluoranthene, and benzo(a)pyrene-extracted by six solvents with four extraction techniques have been determined for diesel exhaust particulate collected on Teflon-coated glass fiber filters. Samples were analyzed by high pressure liquid chromatography with fluorescence detection. Toluene and methylene chloride gave higher recoveries than methanol, isopropanol, acetonitrile, and acetone for benzo(a)anthracene, benzo(k)fluoranthene, and benzo(a)pyrene. Soxhlet extraction for two hours (approximately 48 cycles) with toluene or acetonitrile was more effective than simple mechanical agitation, ultrasonic agitation for 15 minutes or immersion in refluxing ‘solvent’ for two hours.

ISSN:0003-2719    

DOI:10.1080/00032718408065306

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Phase solubility analysis (PSA) was applied to the determination of azinphos-ethyl and - methyl standards. The presence of 0.5% purity was detected by the method. A linear cumulative effect was obtained when known amounts of two impurities were added to standards of both organophosphate materials which were then analyzed by the phase solubility method.

ISSN:0003-2719    

DOI:10.1080/00032718408065307

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

We propose a rapid and convenient method for the determination of sodium nitroprusside in aqueous solution. In alkaline medium and in the presence of dimethylsulfoxide, the concentration of the nitrite ions coming from the nitroprusside corresponds with the initial quantity of this compound.

ISSN:0003-2719    

DOI:10.1080/00032718408065308

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A new concept for the analytical application of persulfate oxidation in alkaline media is presented: The persulfate oxidation of organic compounds has been utilized to determine their nitrogen content. The ammonia formed in the oxidation coupled distillation was measured acidimetrically with an accuracy of ± 0.5 % (rel.). The applicability of the method proposed is shown in the determination of the organically bound nitrogen content of numerous model substances as well as industrial and natural matrices: vinasse, aluminate liquor, white- and soy-bean samples, eggprotein.

ISSN:0003-2719    

DOI:10.1080/00032718408065309

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A flow system version of a barium electrode based on a sparingly soluble mixture of lauric acid and barium laurate as the responsive element and a glass electrode as the primary sensor is reported. The basic theory of the barium response of this system is arrived at by extension of that proposed for the static system case.

ISSN:0003-2719    

DOI:10.1080/00032718408065310

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor