An enzyme electrode for determination of aromatic diamines and aminophenols based on cross-linked ceruloplasmin

1984 ◽  
Vol 49 (3) ◽  
pp. 752-756 ◽  
Author(s):  
Lumír Macholán ◽  
Milan Jílek
Keyword(s):  
Response Time ◽  
Reaction Layer ◽  
Aromatic Amines ◽  
Enzyme Electrode ◽  
Aromatic Diamines ◽  
Oh Groups ◽  
Electrode Response ◽  
Marked Selectivity ◽  
Better Than

The determination of aromatic amines and phenols by an enzyme pO2 electrode containing cross-linked ceruloplasmin in the reaction layer was examined. The electrode shows at pH 5.5 a marked selectivity for derivatives with-NH2 or NR2, resp., and -OH-groups in para and ortho position while its sensitivity for aromatic diamines is better than its sensitivity for aminophenols and polyphenols. p-Phenylenediamine and its N,N-dialkyl derivatives are the best analytes which can be detected starting from concentrations of 10-5 mol l-1 and higher; the reproducibility is 5-7% at an electrode response time of 2-5 min.

A Glucose Oxidase Immobilized Electrode Based on Modified Graphite

2002 ◽  
Vol 57 (7-8) ◽  
pp. 705-711 ◽  
Author(s):  
Nina Dimcheva ◽  
Elena Horozova ◽  
Zinaida Jordanova
Keyword(s):  
Uric Acid ◽  
Response Time ◽  
Glucose Oxidase ◽  
Substrate Concentration ◽  
Enzyme Electrode ◽  
Initial Activity ◽  
Electrode Response ◽  
Working Surface ◽  
Enzyme Layer

Glucose oxidase (E. C. 1.1.3.4) was immobilized on electrochemically modified graphite to obtain an enzyme electrode. The working surface of the electrode was coated with gelatine to prevent desorption of the enzyme. In substrate (glucose) solutions the amperometric signal of the enzyme electrode was due to the electroreduction of H2O2 generated in the enzyme layer. The linearity of the electrode response was found up to a substrate concentration of 300 μᴍ at a working potential of 0 mV (vs. Ag/AgCl). It was shown that the electrode did not respond to l-ascorbic and uric acid at that working potential. The response time was about 2 min. The enzyme electrode keeps about 50% of its initial activity after a one-week storage at 4 °C.

A biospecific membrane sensor for the determination of sucrose

1983 ◽  
Vol 48 (3) ◽  
pp. 798-804 ◽  
Author(s):  
Lumír Macholán ◽  
Hana Konečná
Keyword(s):  
Thin Film ◽  
Hydrogen Peroxide ◽  
Steady State ◽  
Reaction Layer ◽  
Enzyme Reaction ◽  
Oxygen Electrode ◽  
Reaction Vessel ◽  
Membrane Sensor ◽  
Electrode Response

The paper describes a rapid method for the biospecific determination of sucrose using an oxygen electrode of the Clark type or a platinum disc anode, the measuring part of which is coated by a thin film of invertase, mutarotase and glucose oxidase co-crosslinked by glutardialdehyde together with serum albumin. After injecting the sample into the reaction vessel the current corresponding to the decrease of the oxygen content or to the formation of hydrogen peroxide in the enzyme reaction layer is registered. The steady state electrode response is proportional to the concentration of sucrose within the range of 0.03 to 1.5 mmol . l-1 and is attained during 1-2 minutes with a reproducibility of 3-4%.

Time and Latitude in South Africa

1972 ◽  
Vol 1 ◽  
pp. 27-38
Author(s):  
J. Hers
Keyword(s):  
South Africa ◽  
Cape Town ◽  
Astronomical Observations ◽  
Royal Observatory ◽  
The Republic ◽  
Astronomical Determination ◽  
Limited Accuracy ◽  
Better Than

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.

Determination of trace concentrations of copper by FIA-FAAS after preconcentration on chelating sorbents

1989 ◽  
Vol 54 (7) ◽  
pp. 1785-1794 ◽  
Author(s):  
Vlastimil Kubáň ◽  
Josef Komárek ◽  
Zbyněk Zdráhal
Keyword(s):  
Sampling Frequency ◽  
Copper Determination ◽  
Flow Rates ◽  
Sample Injection ◽  
Injection Flow ◽  
Chelating Sorbents ◽  
Set Up ◽  
Trace Concentrations ◽  
Better Than

A FIA-FAAS apparatus containing a six-channel sorption equipment with five 3 x 26 mm microcolumns packed with Spheron Oxin 1 000, Ostsorb Oxin and Ostsorb DTTA was set up. Combined with sorption from 0.002M acetate buffer at pH 4.2 and desorption with 2M-HCl, copper can be determined at concentrations up to 100, 150 and 200 μg l-1, respectively. For sample and eluent flow rates of 5.0 and 4.0 ml min-1, respectively, and a sample injection time of 5 min, the limit of copper determination is LQ = 0.3 μg l-1, repeatability sr is better than 2% and recovery is R = 100 ± 2%. The enrichment factor is on the order of 102 and is a linear function of time (volume) of sample injection up to 5 min and of the sample injection flow rate up to 11 ml min-1 for Spheron Oxin 1 000 and Ostsorb DTTA. For times of sorption of 60 and 300 s, the sampling frequency is 70 and 35 samples/h, respectively. The parameters of the FIA-FAAS determination (acetylene-air flame) are comparable to or better than those achieved by ETA AAS. The method was applied to the determination of traces of copper in high-purity water.

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