摘要:

This paper describes a flow potentiometric method for determination of ammonium at low levels. A new diffusion cell coupled to an ammonium ion electrode was used as the potentiometric detector. This method eliminates interference to the ammonium ion electrode. When the stopped-flow method is employed for the acceptor stream, ammonium ions can be accumulated in the acceptor solution in the diffusion cell, giving high selectivity and sensitivity. The lower linear value of the proposed method can reach 1 × 10−6mol L−1with an accumulation time of 5 min. The method is simple, sensitive and suitable for online determination of ammonium in water samples. It has been applied to the determination of ammonium in rain water and river water, and recoveries of 95 – 104% were obtained. The relative standard deviation of seven replicate analyses for all samples was 1.1 – 2.7%.

ISSN:0003-2719    

DOI:10.1080/00032719708007214

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Oxalacetic acid (OAA), an α-keto acid, absorbs strongly in the 250-265 nm region where most keto- and amino-acids do not absorb. This absorption peak was used for the direct quantitative determination of oxalacetic acid in the presence of L-aspartic, L-glutamic, and α-Ketoglutaric acids. Studies were done on solutions prepared in 0.1 M phosphate buffers at pH 7.4 and 8.4 and in 0.1 M Tris, (Tris(hydroxymethyl)aminomethane), buffer at pH 8.4. Spectra of the individual acids and of those in a mixture revealed that only oxalacetic acid absorbs in the 250-265 nm region. For quantitative measurements of OAA, calibration curves were constructed. Absorbance of OAA at 260 nm was found to be linear over the wide concentration range 1×10−5-5×10−3M in phosphate and Tris buffers, pH 7.4 and 8.4, respectively. Due to its chemical structure, OAA decarboxylates spontaneously in solution. From preliminary kinetic studies of the decarboxylation, it was found that within the time-frame of measurements, this side reaction has no significant effect on the accuracy of measurements. For a 1×10−3M solution, the absorbance decreased by approximately 1% after 5 minutes and by 1.6% after 10 minutes.

ISSN:0003-2719    

DOI:10.1080/00032719708007215

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Human serum aspartate amino- transferase(AST) activity was measured voltammetrically at a gold micro electrode. 2,6- dichloroindophenol(DClP) was used as the redox mediator and electroactive species. Sensitive measurements free from spectrophotometric interferences can be made by a differential pulse voltammetric detection technique. The instrumentation is simple and inexpensive. The method yields reproducible results that were in excellent agreement with those obtained using the standard spectrophotometric method for determining serum AST activity in the clinical laboratory.

ISSN:0003-2719    

DOI:10.1080/00032719708007216

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The separation and determination of chlorogenic acid inEucommia ulmoideswas studied using reversed electroosmotic flow capillary electrophoresis. The addition of 0.2 mmol/L of cetyltrimethylammonium bromide (CTAB) could change the direction of electroosmotic flow. When 10–20%(v/v) methanol was added to KH2PO4-Na2B4O7buffer at pH 8.6, the separation of chlorogenic acid from other components inEucommia ulmoidesleaf and its cortex cell culture was achieved using -20KV voltage. The effect of pH and concentration of the buffers, applied voltage and loading time on the separation and determination were also investigated. Using this method, the analysis of chlorogenic acid could be completed within 4 minutes.

ISSN:0003-2719    

DOI:10.1080/00032719708007217

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

On the basis of the fluorescence enhancement effect of nucleic acids on the aluminum (III) / 8-hydroxyquinoline (8-HQ) complex, a spectrofluorimetric method for nucleic acids is proposed in the present paper. In the pH range 5.8–7.0, the fluorescence of the Al(III)/8-HQ complex, excited at 265 nm or at 365 nm, is enhanced by nucleic acids. The calibration curve was linear in the range 0.25 – 3.0 μg ml−1for calf thymus DNA, 0.25 – 3.5 μg ml−1for fish sperm DNA and 0.5 – 3.5 μg ml−1for yeast RNA, respectively. The limit of determination (3[sgrave]) was 0.024 μg ml−1for calf thymus DNA, 0.013 μg ml−1for fish sperm DNA and 0.130 μg ml−1for yeast RNA, respectively. Six synthetic samples were determined with satisfaction.

ISSN:0003-2719    

DOI:10.1080/00032719708007218

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two simple and sensitive spectrophotometric methods are described for the determination of benzalkonium chloride which is added as a preservative in certain dosage forms. The methods are based on the formation of highly coloured stable radical anions between benzalkonium chloride as n-electron donor and 7,7,8,8-tetracyanoquinodimethane (TCNQ) or 2,3-dichloro-5,6dicyano-p-benzoquinone (DDQ) as n-electron acceptors. Beer's Law is obeyed over the concentration range 0.5 - 8 and 1 - 8 μg ml−1for TCNQ and DDQ respectively. The optimum experimental parameters for colour production with both reagents were studied and incorporated into procedures. The percentage recoveries obtained were in accordance with those given by the official method. The proposed methods are characterized by high sensitivity, satisfactory accuracy and precision.

ISSN:0003-2719    

DOI:10.1080/00032719708007219

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A colorimetric method for the determination of ampicillin (Amp.) and 6-aminopenicillanic acid (6-APA) are described, based on the reaction of these drugs with acenaphthenequinone in basic media to give a highly intense red coloured product. The latter exhibits an absorption maximum at 610 nm with apparent molar absorptivities of 2.83 and 1.45 × 104l. mol−1cm−1and Sandell sensitivities of 0.013 and 0.015 μg cm−2for Amp. and 6-APA, respectively. The optimum concentration ranges are 0.4-10 and 0.4-14 μg ml−1for Amp. and 6-APA, respectively. For more accurate results, Ringbom optimum concentration ranges are 1–8.5 and 1–12 μg ml−1for Amp. and 6-APA, respectively. Statistical analysis indicated that there was no significant difference between the results obtained by the described method and those of the official methods. The mean recoveries percentage were found to be 99.5 × 1.1% for pharmaceutical formulations and 99.1 × 1.6% for serum and urine samples. The method is selective for the determination of Amp. or 6-APA in the presence of their degradation products, additives and excipiences that are normally encountered in dosage forms. The proposed method was applied successfully to the determination of Amp. in pharmaceutical formulations. Also, applicability of the proposed method to human serum and urine is presented and the validity assessed by applying the standard addition technique.

ISSN:0003-2719    

DOI:10.1080/00032719708007220

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Phencyclidine forms ionic associates with Bromoxylenol Blue, Cresol Red, Eriochrome Cyanine R, Orange I, Amido Black 10B and Xylenol Blue. The associates are extractable with chloroform and the extracts exhibit absorption maxima in the region 407 - 625 nm. Maximum extraction of the associates was achieved after two to five minutes at pH 2 - 5. The method allows detection of PCP in aqueous solutions at concentrations of 0.32 mg.ml−1to 1.94 mg.ml−1and determination at 0.74 mg.ml−1to 5.15 mg.ml−1.

ISSN:0003-2719    

DOI:10.1080/00032719708007221

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An HPLC method has been developed for the determination of the beta adrenergic blocking drug metoprolol tartrate. The method is based on the formation of a Cu (II) - dithiocarbamate complex by precolumn derivatization of secondary amino group of metoprolol with CS2and CuCl2in the presence of ammonia. The complex is extracted into chloroform and injected into the chromatograph. Chromatographic separation was performed by a RP (μ Bondapak C18) column with methanol - pH 5.8 phosphate buffer (80 : 20) as the isocratic mobile phase. A variable wavelength absorbance detector (λ = 275 nm) was used. A linear relationship was obtained between peak areas and metoprolol tartrate concentrations over the range of 35 - 180 nmol ml−1. The method was applied to the analysis of metoprolol tartrate tablets and the results were statistically compared with those obtained by official method using t - and F - tests.

ISSN:0003-2719    

DOI:10.1080/00032719708007222

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Propofol is an intravenous anaesthetic widely used for induction and maintenance of anaesthesia and for sedation. A sensitive and simple gas chromatography-mass spectrometry (GC-MS) method for the determination of 2,6-diisopropyl-1,4-quinol, the major hydroxylated propofol metabolite, is presented. Thymol was used as internal standard. Thymol and 2,6-diisopropyl-1,4-quinol are extracted under basic conditions. The extraction efficiencies for quinol metabolite was > 90 %. Standard curves were linear over the ranges of 50 to 2500 ng ml−1. This assay represents an alternative to existing methods of 2,6-diisopropyl-1,4-quinol analysis, which use HPLC. The assay was applied to the analysis of propofol metabolism in vitro by rat liver microsomes.

ISSN:0003-2719    

DOI:10.1080/00032719708007223

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor