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K Kalcher

Publications and source records attributed to K Kalcher.

4 recordsLinked to original sources
PubMed2001

Improved method for the fluorimetric detection of beta-D-galactosidase in water.

A very convenient method to quantify coliform bacteria in water can probably be designed via the determination of the activity of the enzyme beta-D-galactosidase, whose natural occurrence is, apart from less frequently occurring aeromonads mainly restricted to this type of microorganisms. 4-methylumbelliferyl-beta-D-galactoside is used as substrate, which is hydrolyzed during the enzymatic reaction; the released 4-methylumbelliferone can be quantified fluorimetrically. In the present study the influence of various physical and chemical parameters on the determination is investigated and the experimental conditions are optimized. Most important entities are the pH value during hydrolysis, the presence of nutrients and co-factors in the sample, and the modification of the substrate. Statistical evaluation of the results obtained by changing single or multiple parameters reflects clearly their positive or negative influence on the enzyme activity. Thus, deliberate addition of surfactants, specific nutrients, salts and co-enzymes results in a significantly increased activity of beta-D-galactosidase towards the substrate, which can be advantageously exploited to increase the sensitivity of the analytical method together with a decrease of the detection limit. The influence of the parameters and the optimized conditions of the improved analytical methods are presented.

Enterobacteriaceae↗
PubMed1998

Trace iron determination in aminoisophthalic acid using differential-pulse cathodic stripping voltammetry at carbon paste electrodes.

Application of differential-pulse cathodic stripping voltammetry using a carbon paste electrode (consisting of carbon powder and liquid paraffin) have been investigated for trace determination of iron in 5-aminoisophthalic acid (AIPA). Samples were dissolved in 1 M HC1, pH was adjusted to 4-5 after addition of EDTA. Voltammetric measurements were performed after filtration. No sample decomposition (mineralization) was necessary. The method showed a good linearity between current and concentration from 3 x 10(-7) to 5 x 10(-5) mol dm-3 of iron, with a detection limit of 3 x 10(-7) mol dm-3 (resp. 1 ppm in solid AIPA). The results agreed well to those obtained by atomic absorption spectrometry (AAS) using electrothermic atomisation. For AAS measurement, however, microwave digestion of samples was necessary.

Carbon↗
PubMed1993

Cadmium and lead in the smoke of a filter cigarette.

Cadmium and lead were determined in the parts of a filter cigarette after fractional smoking. The partitioning of these elements into the main smoke stream, consisting of particulates and gases, also into the side stream, the ash and the butt was determined. Approximately 70% of the lead mobilized by the smoking process was found in the ash; about 50% of the cadmium was transferred into the side stream. The overall trend shows an increase in the amount of the metals in the main stream as the number of puffs is increased. A model for the behavior of the main stream components within the cigarette was developed and showed a high analogy with the Lambert-Beer law describing the absorption of light.

Cadmium↗