摘要:

A mini review of enzyme-based electrochemical biosensors for inhibition analysis of organophosphorous and carbamate pesticides is presented. Discussion includes the most recent literature to present advances in detection limits, selectivity and real sample analysis. Recent reviews on the monitoring of pesticides and their residues suggest that the classical analytical techniques of gas and liquid chromatography are the most widely used methods of detection1.2. These techniques, although very accurate in their determinations, can be quite time consuming and expensive and usually require extensive sample clean up and pre-concentration. For these and many other reasons, the classical techniques are very difficult to adapt for field use.

ISSN:0003-2719    

DOI:10.1080/00032719908542594

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Pseudomonascells able to degrade biphenyl and chlorinated benzoates were used as a basis of the recognition element in amperometric biosensors. The possibility of detecting biphenyl and chlorinated benzoates in a range of concentrations from 0.002 to 0.3 mM and 0.01 to 1.0 mM, respectively, was shown. The sensors were characterized by wide substrate specificity. Their parameters and the dependence of signals on the measurement conditions (pH of the medium, temperature, salt concentration) were studied. It was suggested that these analyzers can be used in practice for evaluation of the total pool of aromatic xenobiotics available at high concentrations in chemical industry wastes.

ISSN:0003-2719    

DOI:10.1080/00032719908542595

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A flow injection method for the determination of nitrate and nitrate in human saliva is described. It is based on the reaction of nitrite with iodide in acidic medium, the triiodide formed being amperometrically monitored at +0.2 V with a platinum microelectrode (r = 5μm) in a wall-jet cell. The method is very sensitive owing to the association of hydrodynamic transport in a flowing solution and the high mass transport rate at a microelectrode, the limit of detection for nitrite and nitrate being 0.07 and 0.25 μM respectively. The sample throughput was 60 h−1and the standard deviation for 5 injections of 1 μM nitrite was 1.9% (1.3% for nitrate). The method was used in the study of the conversion of nitrate to nitrite in the oral cavity by bacteria, experimental data concerning the salivary concentration of both ions being obtained before and after treatment with an antiseptic solution. The results showed the decline of nitrite concentration after the oral treatment followed by a proportional increase in the nitrate concentration, proving that the majority on salivary nitrite comes from bacterial reduction of nitrate.

ISSN:0003-2719    

DOI:10.1080/00032719908542596

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A biosensor based on carbon paste modified with crude extract of cara root (Dioscorea bulbifera) is proposed for the determination of epinephrine and dopamine in pharmaceutical formulations. After selection of the extraction medium, a crude extract of cara root was used as enzymatic source ofpolyphenol oxidase(PPO;tyrosinase; catechol oxidase; E.C:1.14.18.1). This enzyme catalyses the oxidation of epinephrine and dopamine to corresponding epinephrinequinone and dopaminequinone. A voltammetric study was performed by scanning the potential between +0.4 and −0.4 V. This biosensor provides a linear response for epinephrine in the concentration range from 2.0 × 10−4to 1.2 × 10−3mol L−1at Epc= −0.14 V (electrochemical reduction of epinechrome to epinephrine) and for dopamine in the concentration range from 2.0 × 10−3to 8.0 × 10−3mol L−1at Epc= +0.15 V (electrochemical reduction of dopaminequinone to dopamine). The detection limit (three times the signal blank/slope) was 8.2 × 10−5mol L−1and 7.5 × 10−4mol L−1for epinephrine and dopamine, respectively. The accuracy was checked by comparing with a Pharmacopoeia procedure and a paired-t test showing that all results obtained for these catecholamines in pharmaceutical products are in agreement at the 95% confidence level. The new biosensors have a longer lifetime than those prepared from purified enzyme.

ISSN:0003-2719    

DOI:10.1080/00032719908542597

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The water-soluble B6vitamins pyridoxine, pyridoxal and pyridoxamine were determined by coupling with the diazonium ion ofp-sulfanilic acid, in a micellar medium ofN-cetylpyridinium chloride (NCPC), with spectrophotometric measurement in the visible region (450 nm). A stable azo dye, with increased sensitivity with respect to the derivative obtained in non-micellar medium, was rapidly formed. The addition of toxic mercury(II) acetate, recommended in a previous procedure to develop the colour for pyridoxine and pyridoxamine, was not required in the presence of NCPC. The procedure was applied to the determination of pyridoxine hydrochloride in commercial pharmaceutical preparations, with recoveries between 94 and 107%, and repeatabilities below 1%. The differences in the coupling reaction rates of the B6vitamins, in the presence of boric acid and NCPC micellar medium, permitted the differential-kinetic analysis of binary mixtures of the three B6vitamins.

ISSN:0003-2719    

DOI:10.1080/00032719908542598

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Three simple and accurate spectrophotometric methods are described for the determination of enrofloxacin, a new fluoroquinolone synthetic orally active broad spectrum antibacterial. The first method is based on the reaction with iron III forming a water soluble yellow complex with maximum absorbance at 434 nm. The method allows the determination of 25–140 μgml−1. The second method involves ion-pair formation with bromocresol purple (BCP) in presence of phthalate buffer (pH 4.8±0.4). The yellow ion-pair is extracted with chloroform and the absorbance is measured at 410 nm. The method allows the determination of 4–18 μgml−1. The third method is based on the reaction of the drug with 8-dichloro-5,6 dicyano-p-benzoquinone (DDQ) in methanol as π-acceptor to give a molecular charge-transfer complex, with maximum absorbance at 460 nm. The method permits the determination of 50–240 μgml−1. Optimization of different experimental conditions were described. Beer's law was obeyed for the three methods and the relative standard deviation was found to be less than 2%. The methods have been applied successfully to the analysis of commercially available enrofloxacin preparations without interference from the ingredient commonly found.

ISSN:0003-2719    

DOI:10.1080/00032719908542599

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The acid dyes eosin B and tropeolin oo were used for the determination of terfinadine, astemizole and acrivastine in the presence of Mcllvain buffer of a suitable pH. The formed ion-pairs were extracted with chloroform and the absorbances were measured at 530–535 nm and 410 nm in the case of eosin B and tropeolin oo, respectively.

ISSN:0003-2719    

DOI:10.1080/00032719908542600

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A sensitive method is described for the determination of cefaclor by cathodic stripping voltammetry at the hanging mercury drop electrode. cefaclor is accumulated at the electrode surface as a mercury salt, which is reduced at −0.67 V. The optimum accumulation potential and accumulation time were +0.15 V and up to 180 s, respectively. Linear calibration graphs were obtained between 3.9 μg.L−1to 39 μg.L−1and the limit of determination was evaluated to be 1.9 μg.L−1. The method was applied successfully to the determination of cefaclor in pharmaceutical formulations.

ISSN:0003-2719    

DOI:10.1080/00032719908542601

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple flow injection method is proposed for the determination of nickel by its complexation with ammonium 2-amino-cyclohexene dithiocarbamate (AACD). The dark red complex can be detected by spectrophotometric determination at 535 nm. The FIA factors that influence on sensitivity were optimized by factorial design analysis. The model of absorbance vs. these factors was constructed and the correlation of these factors with each other was studied. Nickel can be determined as low as 0.007 μg/ml and Beer's law was obeyed in the range of 0–2.5 μg/ml of Ni(II). The effect of more than thirty potential interfering cations and anions were studied. The evaluation of the method was examined by the determination of Ni(II) in hydrogenated vegetable oil and synthetic samples.

ISSN:0003-2719    

DOI:10.1080/00032719908542602

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The paper describes a simple and sensitive spectrofluorimetric procedure for the analysis of microquantities of aluminum in drinking water for toxicological purposes. The method is based on the formation of the Al(III) – Mordant Red 19 complex, after a comparative study of the complexes formed with several compounds of the Mordant family. The emission of the fluorescent complex was measured at λ = 555 nm with excitation at λ = 475 nm. A good linearity was found in the 1 – 80 ng ml−1of aluminum range. The precision of the method was good, the intraday Relative Standard Deviation being 1.9% for a 30 ng ml−1aluminum standard solution. The procedure proved to be suitable in terms of accuracy and selectivity for the microdosage of aluminum in mineral waters.

ISSN:0003-2719    

DOI:10.1080/00032719908542603

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor