摘要:

A method for the catalytic voltammetric determination of perchlorate using a carbon paste electrode modified with a liquid anion exchanger is presented. The fundamental catalytic effect is based on the chemical reoxidation of electrochemically generated Tl(O) by perchlorate which can be monitored by an increase of the corresponding current flow. Perchlorate can be preconcentrated, together with tetrachlorothallate(III) as a catalyst, from hydrochloric acid solutions onto the modified carbon paste electrode under open circuit conditions. For analytical purposes, the increase of the current response for the reoxidation of Tl(O) to Tl(I) is exploited for quantifications. Methodical parameters such as pH, ionic strength of the media, preconcentration time and thallium concentration are investigated; the influence of interferents is studied. The dependence of the current increase on the concentration of perchlorate with different accumulation times is presented. The detection limit (3σ) is 50 μg˙l−1ClO4−(12 min accumulation). To show the applicability of the method to the analysis of real samples spiked drinking water was investigated.

ISSN:0003-2719    

DOI:10.1080/00032719608001516

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/ lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 8.0–8.4 (controlled by NH3-NH4Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for yeast RNA (when excited at 267.0 nm) and emits at 483.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4–3.6 μg˙ml−1for calf thymus DNA, 0.4–4.0 μg-ml−1for fish sperm DNA and 0.4–4.0 μg˙ml−1for yeast RNA, respectively. The limits of determination (3σ) were 0.076 μg˙ml−1for calf thymus DNA, 0.068 μg˙ml−1for fish sperm DNA and 0.329 μg˙ml−1for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.

ISSN:0003-2719    

DOI:10.1080/00032719608001517

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A method was developed for the automatic quantitative determination of potassium in serum, by flow injection analysis. The serum sample is directly introduced in the flow. The dilution with deionized water stream is done automatically and sequentially in the system to reach the adequate concentration to be introduced in the flame photometer. The results achieved with this method, for serum samples obtained in the Hospital of the University, had been compared with those values of the Hospital laboratory that uses manual dilution and flame photometry. The results obtained by the two methods agree within at least ±5%. About 60 samples/hour can be easily analyzed by the method proposed in this work.

ISSN:0003-2719    

DOI:10.1080/00032719608001518

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A rapid and sensitive fluorimetric method has been developed for the determination of trace hydrogen peroxide (0–5.0 × 10−6mol/l) and, indirectly, glucose (3.0 × 10−7– 3.5 × 10−5mol/l), based on the catalytic effect of hemin on the thiamine, a new fluorogenic substrate, and hydrogen peroxide system at pH=8.0. Using the fixed time method, the detection limits of hydrogen peroxide and glucose are 3.0 × 10−8mol/l and 3.0 × 10−7mol/l, respectively. This method is simple, inexpensive and has been applied successfully to the determination of glucose in human sera with relative standard deviation of 2.4–3.1%.

ISSN:0003-2719    

DOI:10.1080/00032719608001519

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The effect of base-pair mismatches on DNA hybridization was investigated by fluorescence polarization to evaluate the specificity of the DNA hybridization technique. A fluorescein-labeled 24-mer DNA probe was used to monitor the course of hybridization, from which the rate of DNA hybridization was obtained. The specificity of the method was considered by comparing the hybridization rate of the fluorescein-labeled probe with complementary oligomers comprising a number of base pair mismatches. In either 0.8 M NaCl or 0.2 M MgCl2, rapidin vitrodetermination of target DNA was possible within 10 minutes if the sample DNA had 3 or less base-pair mismatches. It was shown that this method would be applicable for rapid and specific DNA determination, even in the presence of mismatches.

ISSN:0003-2719    

DOI:10.1080/00032719608001520

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A capillary gas chromatographic method is described for the determination of perindopril, an anti-hypertensive agent. The method is based on the derivatization of perindopril with pentafluorobenzyl bromide in acetone, using potassium carbonate as a base catalyst. Under a mild condition, the highly polar and nonvolatile perindopril was derivatized into a derivative with suitable chromatographic properties. The resulting derivative was separated on an SE-54 capillary column and detected by a flame-ionization detector.

ISSN:0003-2719    

DOI:10.1080/00032719608001521

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Three visible spectrophotometric methods (A-C) for the determination of Methotrexate (MTX) in pharmaceutical formulations are described. Method A is based on the reduction of Fe(III) to Fe(II) by the drug which forms a coloured complex (λmax: 510 nm) with 1,10-phenanthroline (PHEN). Method B involves the reduction of Folin-Ciocalteu (F-C) reagent by the drug and the reduced species produced possesses a characteristic intense blue colour (λmax: 770 nm). Method C is based on the coupling reaction through the involvement of an aromatic secondary amino group in p-N-methylaminobenzoylglutamic acid (released through reduction of the drug with zinc and HCl) with 1,2-naphthaquinone-4-sulfonic acid sodium salt (NQS) to form a coloured product (λmax: 500 nm). Regression analysis of a Beer's plot showed good correlation in the concentration ranges of 1.0–8.0, 2.0–14.0 and 25.0–300.0 μg.ml−1for methods A,B and C, respectively. No interference was observed from the additives and the applicability of the methods was tested by analysing the pharmaceutical formulations containing methotrexate. Recoveries were 98.9–101.1%.

ISSN:0003-2719    

DOI:10.1080/00032719608001522

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A sensitive adsorptive stripping voltammetric method for measurement of hesperidin in 0.1 M NaAc-HAc solution was described. The method was based on the adsorptive accumulation of the drug at a hanging mercury drop electrode, followed by linear sweep voltammetry. The response was evaluated with respect to preconcentration time, pH effect and concentration of HAc-NaAc buffer solution. The peak potential was -1.01V (vs.Ag/AgCl). The peak current was directly proportional to the concentration of hesperidin with a detection limit of 3.0×10−7M at an accumulation time of 2 min. The reduction process is irreversible and the wave shows adsorptive characteristics.

ISSN:0003-2719    

DOI:10.1080/00032719608001523

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Silica gel bound to some amine derivatives such as semicarbazide, thiosemicarbazide, ethylenediamine and phenylenediamine as well as ion exchangers containing carboxylic groups derived from phthalic anhydride and succinic anhydride were synthesized, and their metal-uptake properties in aqueous solution were studied. The factors controlling and influencing the metal uptake capacity, such as shaking time and pH of the metal ion solution, were also determined to evaluate and compare the performance toward metal ion extraction. The data in this study show that the values of metal capacity of the silica gel-bound complexing agents are higher than those of the ion exchanger analogs, and those of the immobilized aliphatic diamines or acid derivatives are higher than the corresponding values of aromatic analogs. A method of recycling the synthesized phases after metal extraction processes, for the sake of further and successive use of the recycled phases, is also presented.

ISSN:0003-2719    

DOI:10.1080/00032719608001524

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A comparison was made between the efficiency of micellar electrokinetic capillary chromatography (MECC) and reversed phase high performance liquid chromatography (RP-HPLC) to separate a mixture of plant phenolics. Of a range of buffers 6 mM borate/10 mM phosphate/100 mM SDS at pH 8.5 was the most effective in separating a complex mixture of phenolics using MECC. Using this buffer the elution order and resolution was different from that obtained by HPLC using a reversed phase C18 column. These results illustrate how MECC and RP-HPLC are complimentary when examining complex mixtures such as those obtained from plant extracts. MECC using these conditions was applied to the examination of phenolics from leaf tissue ofEucalyptus margmata(jarrah).

ISSN:0003-2719    

DOI:10.1080/00032719608001525

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor