摘要:

The performance and dynamic response characteristics of the potentiometric carbon dioxide gas sensor with an alternative to the commercially available silicon rubber membrane are studied in this paper. This study was performed in the course to choose a low cost membrane and possibly to further optimize the time response of this sensor. The membrane used was a microporous Teflon membrane which is used in ammonia gas sensor. The results have shown that the CO2gas-sensing probe with the Teflon membrane shows similar performance characteristics as the silicon rubber membrane, but improved stability with time. Convolution mathematics were also used to study the dynamic response characteristics of the gas sensor with the Teflon membrane and the results have shown that practically similar time constants are obtained as when a silicon rubber membrane is used. Therefore, the less costly membrane can replace the silicon rubber membrane when CO2is being monitored and a gas-sensing probe can be constructed through this means, by using a Teflon membrane and a 1 mM NaHCO3- 100 mM NaCl internal filling solution.

ISSN:0003-2719    

DOI:10.1080/00032719308016807

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new metformin (Mf) ion selective PVC membrane electrode based on the ion-pair complex of Mf with sodium tetraphenylborate was prepared and its performance characteristics were studied. The electrode exhibited a linear response with a good Nernstian slope over a relatively wide range of concentration. The calibration graph slope was constant for up to 14 days with continuous soaking at 54 mv/ concentration decade at 30°C. Then the slope decreased as the time of soaking increased, reaching 42 mv/decade after 21 days. The changes in pH did not affect the electrode performance within the range 4.0–11.0. The standard electrode potentials were determined at different temperatures and were used to calculate the isothermal coefficient of the electrode (0.0004 V/°C). The electrode showed a very good selectivity for Mf with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were used to determine Mf in pure solutions and in pharmaceutical preparations.

ISSN:0003-2719    

DOI:10.1080/00032719308016808

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Thromboxane B2(TxB2) was determined by high performance liquid chromatography (HPLC) after pre-column derivatization with fluorescent probes. We report the results of two derivatization procedures. The carboxylic group of thromboxane B2was esterified either by 4-bromomethyl-7-methoxycoumarin or by panacyl bromide whereas its alcoholic functions were derivatized using 7-[(chlorocarbonyl) methoxy]-4 methylcoumarin. Characteristics of the method and first results with TxB2released by platelets under pharmacological stimulation are reported.

ISSN:0003-2719    

DOI:10.1080/00032719308016809

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The adsorption process of four metals in solution (Pb, Cu, Zn, Cd) toChlorella Vulgariswill be described and compared to a previous study using three metals (Pb,Cu,Zn) in solution. The binding capacity ofChlorella Vulgaristo four elements simultaneously increases with time, mass of algae, and up to a temperature of about 20.0°C. The equilibrium points for binding three metals simultaneously are at pH=4.55, with 7 mg of algae, and after 2.0 hrs. in a 5 ml aliquot of the solution. In the four metal system, the optimum values are significantly higher while the binding capacity is reduced. The competition between metals for binding sites in the algal cells is governed by kinetic properties as related to the pH, mass of algae, time, and concentration of solution. The binding process is also dependent upon thermodynamics with respect to the temperature of the solution.

ISSN:0003-2719    

DOI:10.1080/00032719308016810

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We have found that high-performance liquid chromatographic analysis of enantiomeric N-protected amino acid esters on a cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase column (Daicel Chiralcel OD) can be utilized as one of the procedures for determining the optical purities of non-protein amino acids. The methyl esters of the N-benzyloxycarbonyl (Z) derivatives of a number of non-protein amino acids showed excellent to good enantiomeric separations using hexane - 2-propanol as a mobile phase. There was a regularity in the elution order of enantiomers: the L-isomer had a shorter retention time than the D-isomer. We have also investigated the effect of the N-protecting groups and the ester groups on the enantiomeric separation. The Z, 4-methoxybenzyloxycarbonyl (Z(OMe)), and 9-fluorenylmethoxycarbonyl (Fmoc) derivatives gave exceptionally good resolutions. By contrast, the formyl and t-butoxycarbonyl (Boc) groups impaired the enantiomeric separation. Almost all the alkyl esters examined and the benzyl ester gave resolutions better than or of the same order as the methyl ester. The resolution of β-amino acids was worse than that of the corresponding α-amino acids.

ISSN:0003-2719    

DOI:10.1080/00032719308016811

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new enzymatic assay method for ornithine carbamoyltransferase, OCT, activity was developed using ornithine:2-oxo-acid aminotransferase, OKAT, and 1-pyrroline-5-carboxylate dehydrogenase, P5CDH. The method is based on the reaction of L-ornithine formation from L-citrulline by OCT. The OCT activity was measured spectrophotometrically at 340 nm and the minimum detectable activity was about 4 units/L of serum. Results obtained by this method and by the chemical method correlated well. This method is superior to the chemical method, as it does not require boiling of the reaction mixture nor removal of interfering substances in the serum.

ISSN:0003-2719    

DOI:10.1080/00032719308016812

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Two spectrophotometric methods for the determination of cefadroxil using Cu(II) and V(V) in sulphuric acid medium are described. Beer's law is obeyed up to 100 μg ml−1and the molar absorptivities are 2.10 × 103and 3.81 × 103L mol−1cm−1with copper and vanadium respectively. The two methods have been applied successfully to the analysis of the pharmaceutical preparations (Duricef oral suspension and capsules).

ISSN:0003-2719    

DOI:10.1080/00032719308016813

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A simple colorimetric method for the determination of six nitro derivatives, namely: furazolidone, nifuroxime, niridazole, nitrazepam, nitrofurantoin and nitrofurazone was described. The suggested method depends upon the formation of orange to purple colour when these nitro compounds react with tetrabutylammonium hydroxide in dimethylformamide. The different experimental parameters were studied and incorporated into the procedure. The mean percentage recoveries ranged from 98.9 ± 0.3 to 100.4 ± 0.7. The proposed method was applied to the determination of certain pharmaceutical dosage forms containing the studied nitro-compounds, as well as furazolidone and nifuroxime in mixture. The results obtained were in agreement with those obtained by official and compendium methods.

ISSN:0003-2719    

DOI:10.1080/00032719308016814

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper the absorption spectra of the copper complex with cyanide ion have been studied by conventional and derivative spectrophotometry. The use of third-derivative spectra both eliminates the interference from other metals and improves the sensitivity. Beer's law is obeyed for 0.64–3.2 μg/ml of copper. The relative standard deviation for 7 determinations 1.5 μg/ml of copper was 0.78%. The detection limit, corresponding to a signal-to-noise ratio of 2, was found to be 0.15 μg/ml. The suggested method has been applied successfully to the analysis of some iron alloys and aluminium alloys without any separation.

ISSN:0003-2719    

DOI:10.1080/00032719308016815

出版商:Taylor & Francis Group    

年代:1993

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 either binary or ternary complex formation. This paper deals with fourth order derivative spectrophotometric procedure for the determination of traces of lead based on the liquid-liquid extraction of ternary ion association complex lead with 1,10-phenanthroline and rose bengal into chloroform. The ternary ion associate is stable for over 24 hours. The developed procedure is simple, rapid, reliable and allows the determination of as low as 20 ppb of lead in sea water samples.

ISSN:0003-2719    

DOI:10.1080/00032719308016816

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor