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K Pfeilsticker

Publications and source records attributed to K Pfeilsticker.

16 recordsLinked to original sources
PubMed2003

Atmospheric detection of water dimers via near-infrared absorption.

Weakly bonded pairs of water molecules (H2O)2, or water dimers (WDs), may play an important role in photochemistry and climate, but the overlap of most of its spectral features with the water monomer (WM) has made detection difficult. We report on WD absorption measurements by means of atmospheric long-path (18.34 kilometers) differential optical absorption spectroscopy of the near-infrared OH stretching mode 0>f 4>b overtone transition predicted to be located near 746 nanometers. Our observation is in reasonable agreement with the known thermochemistry, calculated and measured structure, and spectroscopy (band strength, shape, and width) of the WD. The observation implies that the WD 0>f 4>b band is located at 749.5 nanometers, with a full width at half maximum of approximately 19.4 wave numbers, and that its band strength ranges between 1.23 x 10(-22) and 5.25 x 10(-22) centimeters per molecule.

Journal Article↗
PubMed1996

[Detection of treatment of chicken breast with ionized rays and gradation of radiation dosage with the help of headspace gas chromatography and discriminant analysis evaluation].

Chicken breast was irradiated with doses of 3, 5, and 7 kGy. Headspace gas chromatographical analysis demonstrated the tendency that the amounts of volatile compounds (mainly pentanal, hexanal and heptanal) are higher in irradiated samples in comparison with non irradiated. Statistical evaluation of the gas chromatograms by discriminant analysis enabled the detection of irradiation. Unknown samples could be classified in the groups "un-irradiated" or "irradiated" in most cases.

Aldehydes↗
PubMed1995

[Selenium content of tea from different provinces of the People's Republic of China].

In the People's Republic of China there are wide regions where many people suffer from strong selenium deficiency. In order to elucidate the possibilities to compensate this state of need by the national drink, the selenium contents of 31 tea samples from nine provinces of the PR China were determined by hydride generation atomic absorption spectrometry (HG-AAS). The Se contents of the ten analyzed tea samples from one region with soils containing high selenium amounts range from 83 ng/g to 7530 ng/g. These results are in contrast to the Se contents of the remaining tea samples from other regions, which range from 28 to 573 ng/g. The extractable part of selenium in the tea drink ranges between 7% and 27% without significant difference among different tea samples. The accuracy of Se determination was tested by using one tea standard reference material. The daily consumption of one "Se tea" examined in this study assures that people who suffer from a Se deficiency resume enough of it. Drinking normal quantities of this tea an intoxication by Se is not to be expected.

China↗
PubMed1993

[Determination of minerals and trace elements in selenium tea from the Enschi district, People's Republic of China, and in its infusions using inductively coupled plasma-atomic emission spectrometry, graphite furnace atomic absorption spectrometry and instrumental neutron activation analysis].

The Enschi district in Hubei province, Peoples Republic of China is geochemically one of the two seleniferous regions, producing both selenium (Se) black tea and the Se green tea. Three samples of green tea with different Se contents and one non-Se tea were analysed. The following mineral and trace elements were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES): K, Ca, Mg, Na, P, S, Al, Mn, Fe, Ba, Sr, Co, Ni, Cu, Zn, Mo, and Cr. Except for Mo, Co, and Cr, all other elements in infusions of the samples analysed were also measured, since their concentrations are lying over their detection limits. The Se content in the tea samples and in the infusions were measured with graphite furnace atomic absorption spectrometry (GFAAS). The accuracy of Se determination was tested by measuring untreated tea samples with instrumental neutron activation analysis (INAA). The Se content in the measured samples was 1 to 8.5 micrograms/g. In addition to Se, 17 other elements were measured in the tea samples and 14 others in the infusions. With this data the extractable part of this elements in the infusion were calculated. Up to 10% of the Se was found in a first infusion.

China↗
PubMed1982

[Charakterisation of L-ascorbic acid oxidase (EC 1.10.3.3) from wheat flour (author's transl)].

The Isoenzymes of L-Ascorbic Acid Oxidase, isolated and separated according to [1] exhibit a maximum activity with L-Ascorbic Acid in the pH range 5,4-6,0 with temperature optima of 30, 39 and 40 degrees C. Cu2+ inactivates the reaction. In this property the enzyme corresponds to other enzymes of different origin. The activating effect o NAC1 with optimum activity near 0,6 mol concentration has not been described previously.

Ascorbate Oxidase↗
PubMed1980

[Isolation and characterisation of L-ascorbic acid oxidase (EC 1.10.3.3) from wheat flour (author's transl)].

Wheat flour (Caribo, 0.55% ash) is extracted with 0.4 M-NaCl-solution, the L-ascorbic acid oxidase precipitated with (NH4)2SO4 and this concentrate separated by thinlayer isoelectric focussing on polyacrylamid- and dextrangel. 8-12 active fractions (isoenzymes) are detected with a high specifity for L-ascorbic acid in respect in L-isoascorbic acid activity). The molecular weights are 165,000-175,000 (determined by dextran gel-thin layer chromatography). In fresh flour the activity is near 28 mg L-ascorbic acid per kg flour in 30 min, after 30 days the activity has diminished to 5% after 60 days no activity is detectable.

Ascorbate Oxidase↗
PubMed1978

[Residues of ethylene chlorohydrin (ECH) in infusions of cocoa and in chocolate (author's transl)].

With a sensitive method residues of 0.2--0.6 ppm ECH are found in commercial and bendtop infusions of cocoa and 1.8--5.6 ppm ECH in chocolate. The balance is established with time between ECH and ethylene oxide (EO) in the boiling infusion and the distillate depending on time. It is found that the ECH concentration in the infusion is reduced in 15 min to 1/7 by evaporation alone. No reaction to EO or ethylene glycol or other metabolites is detectable. For the determination alkali is added to the sample, followed by distillation of any formed EO into dilute sulfuric acid, where ethylene glycol is oxidized to formaldehyd according to Malaprade. This is distilled off for further enrichment and determined according to Bremanis by photometry at 570 nm. The determination for limit was to 0.01 ppm, the standard deviation is s = 0.0034 ppm (N = 30), the yield 99.8%. The sensitivity may be increased tenfold by increasing sample size.

Cacao↗
PubMed1977

[Residues of 1-14C-acrylonitrile in fumigated dry food (author's transl)].

Ten different kinds of dry food were fumigated with 10 g/m3 of 1-14C-Acrylonitrile (AN, 24 h, 20 degrees C). Residues of 0--19 mg/kg AN were found by Liquid-Scintillation-Spectrometry. The values become smaller as the density of the material increases. 30--70% of this agent are metabolised within two months.

Acrylonitrile↗
PubMed1976

[Isolation of the Derivatives from Coca-Powder Fumigated by Ethylene Oxide 1,2-14 C and their Structure Suggested on the Basis of I. R. and Mass-Spectrometry].

In Coca-powder fumigated with Ethylene Oxide-1,2(14)C, several derivatives were isolated by extraction and preparative Thin Layer Chromatography. Of the two compounds isolated from the water-extract, the structures have been suggested as N,N-Bis-(Di-Ethoxy-O-Hydroxy-ethyl)-Isoleucyl-Alanyl-Cysteine (MW = 569)and N-Ethoxy-O-Hydroxyethyl)-Tyrosine (MW = 269), based on I.R. and Mass Spectrometry. Their approximate concentrations were found to be 20 and 50 mg/kg respectively.

Amino Acids↗
PubMed1975

[Group separation of ethylene oxide 1,2-14c fumigated coca-powder derivatives and their distribution of radioactivity (author's transl)].

A procedure based on extraction, column chromatography and precipitation is described for the separation of ethylene oxide-1,2-14C fumigated coca-powder derivatives in 9 different groups. As it was found in wheat [1], the major portion of radioactivity lies in water extract; in coca-powder the major portion of radioactivity is also found in low molecular components.

Cacao↗
PubMed1975

[Simultaneous, gas-chromatographic determination of ethyleneoxide, ethylenechlorohydrine and ethyleneglycol in grain (author's transl)].

The not comminuted grain (10 g) is extracted for 24 hrs (25 degrees C) with 5 ml methanol (shaking machine), then the fluid phase is separated by centrifugal filtration and directly injected into the GC (10 mu). The GC starting temperature (60 degrees C) is adjusted by cooling the oven with Co2. Yield: EO 73% (concentr. range 25 ppm); ECH 93% (concentr. r. 50 ppm); EG 99% (conc. r. 50 ppm). Standard deviation: EO s = +/- 1,70 ppm (N = 24, conc. r. 10 ppm), ECH s = +/- 1,15 ppm (N = 24, conc. r. 20--30 ppm), EG s = +/- 0,62 ppm, (conc. r. 15--30 ppm, N = 24).

Chlorohydrins↗