Determination of aryloxyphenoxypropanoic acid derivatives in crops treated with herbicidal sprays

Summary A reproducible and sensitive gas Chromatographic method has been developed for the trace analysis of fluazifop-butyl, haloxyfop-ethoxyethyl and quizalofop-ethyl as well as their main metabolites (corresponding acids analysed after conversion to methyl esters) in some fruits and vegetables treated with herbicidal sprays. Comparable detection limits (0.01 mg/kg) were achieved when mass fragmentography and/or the electron capture detector were employed. However, in the latter case, bromination of fluazifop esters had to be carried out prior to GC analysis. By means of the nitrogen-phosphorus detector, determination of residues at a level of 0.05 mg/kg was possible. The residue values found in strawberries, cabbages, cauliflowers and carrots were used to discuss the degree of metabolic hydrolysis of parent esters, i.e. active ingredients of herbicides.

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Bestimmung von Aryloxyphenoxypropionsäure-Derivaten in mit Herbicidsprays behandelten Produkten

Zusammenfassung Es wurde eine gaschromatographische Methode zur quantitativen und selektiven Bestimmung von Fluazifop-butyl, Haloxyfop-ethoxyethyl und Quizalofop-ethyl sowie von ihren Hauptmetaboliten (den entsprechenden Säuren, die zu Methylestern umgesetzt werden müssen) in mit Herbiciden behandelten Obst- und Gemüseproben entwickelt. Eine Nachweisgrenze von 0,01 mg/kg wurde durch Elektroneneinfanggaschromatographie oder durch Massenfragmentographie erzielt. Um die gleiche Empfindlichkeit des EC-Detektors bei Fluazifop zu erreichen, wurden die beiden Ester mit Brom umgesetzt. Mit Hilfe des NP-Detektors konnte eine Nachweisgrenze von 0,05 mg/kg erreicht werden. Die festgestellten Rückstandsgehalte in Erdbeeren, Kohl, Blumenkohl und Möhren wurden gleichzeitig zur Beurteilung der metabolischen Hydrolyse der diskutierten Ester (der Wirkstoffe der Herbicide) herangezogen.

     

Flavour significant compounds in yeast autolysate Gistex X-II Powder. Part 2. Neutral and basic fractions

Flavour properties of the individual fractions of aroma concentrate isolated from yeast autolysate Gistex X-II Powder were organoleptically evaluated. Using coupled gas chromatography-mass spectrometry there were identified some volatile substances in the basic and neutral fractions. Alkylpyrazines were found as the major constituents of the basic fraction. Nitrogen and oxygen-containing heterocyclic compounds, phenols and carbonyls were identified in the neutral fraction. The influence of heat treatment on yeast autolysate was also investigated.     

Analysis of Amadori compounds by high-performance cation exchange chromatography coupled to tandem mass spectrometry

High-performance cation exchange chromatography coupled to tandem mass spectrometry or electrochemical detection was found to be an efficient tool for analyzing Amadori compounds derived from hexose and pentose sugars. The method allows rapid separation and identification of Amadori compounds, while benefiting from the well-known advantages of mass spectrometry, such as specificity and sensitivity. Glucose- and xylose-derived Amadori compounds of several amino acids, such as glycine, alanine, valine, leucine/isoleucine, methionine, proline, phenylalanine, and glutamic acid, were separated or discriminated using this new method. The method is suitable for the analysis of both model reaction mixtures and food products. Fructosylglutamate was found to be the major Amadori compound in dried tomatoes (approximately 1.5 g/100 g) and fructosylproline in dried apricots (approximately 0.2 g/100 g). Reaction of xylose and glycine at 90 degrees C (pH 6) for 2 h showed rapid formation of xylulosylglycine (approximately 12 mol %, 15 min) followed by slow decrease over time. Analysis of pentose-derived Amadori compounds is shown for the first time, which represents a major breakthrough in studying occurrence, formation, and decomposition of these labile Maillard intermediates.     

The influence of some pesticides on the quality of apples. I. Enzymatic browning reactions

Zusammenfassung In Äpfeln, welche mit den Pesticiden Melprex 65 W und/oder Anthio 25 behandelt wurden, und weiterhin in nicht behandelten Früchten (Kontrolle) wurden bedeutende Mengen von Substraten der Polyphenoloxidasen festgestellt. In den Proben wurden unterschiedliche Mengen von o-Diphenolen und phenolischen Säuren gefunden. Eine signifikant niedrigere Menge dieser Stoffe wurde in den mit Melprex 65 W behandelten Früchten nachgewiesen. Die Aktivität der Polyphenoloxidasen in dieser Probe ist fast identisch mit der Kontrolle. In den mit Anthio 25 behandelten Früchten beobachtete man ein etwas geringeres Braunwerden. Interessant ist die Feststellung, daß Dodine, der aktive Bestandteil von Melprex 65 W, die Bildung von Farbprodukten bei den Reaktionen der enzymatischen Bräunung beeinflußt.

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The influence of some pesticides on the quality of apples. I. Enzymatic browning reactions

Summary The contents of some significant substrates of apple polyphenol oxidase were determined either in fruit treated with Melprex 65 W and/or Anthio 25 and in untreated fruit. Some differences were found in the concentrations of o-Dihydroxyphenols and phenolic acids. The significantly lower content of these substances was checked in apples treated with Melprex 65 W. The activity of polyphenol oxidase in this sample was nearly the same as that in a control. A slightly lower rate of browning was observed in apples treated with Anthio 25. It was proved that dodine (active ingredient of Melprex 65 W) participates in the formation of coloured products originating during enzymatic browning reactions.

     

The studies of interaction between ascorbate oxidase and some organophosphorous insecticides in vitro

Summary The possible interactions between organophosphorous insecticides (OPI) and plant homogenates of ascorbate oxidase (AO) were studied. There was not found any inhibition of AO activity. The decrease in the activity of AO can be caused in vitro by the presence of some acid degradation products of OPI, which can influence the highly sensitive AO to pH. According to the buffer capacity of the plant tissues it may be supposed that this mechanism of inhibition does not occur in vivo.

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Zusammenfassung Es wurden die Interaktionen der Organophosphor-Insecticide mit Ascorbinsäure-Oxidase verfolgt. Es kommt zu keiner Hemmung der Ascorbinsäure-oxidase (AO) unter experimentellen Bedingungen. Die der AO kann in vitro durch Abbau-Produkte der Organophosphor-Insecticide hervorgerufen werden, die die gegen pH-Änderungen hochempfindliche AO beeinflussen können. In Rücksicht auf die Puffer-Kapazität der Pflanzengewebe kann man annehmen, daß dieser Mechanismus in vivo nicht verlaufen kann.

     

Design of state digital filters

In this correspondence, we develop a very simple algorithm for the design of a second-order state-space digital filter. The design equations presented here were derived on the rendition that the sensitivity of the coefficients in the state-space digital filter (SDF) are spread uniformly to all coefficients of the SDF. The design algorithm has been shown to provide SDF realizations having a minimum output round-off noise while preserving low coefficient sensitivity and freedom from limit cycles