Enzymatic reaction coupled with flow-injection analysis with charged aerosol, coulometric, or amperometric detection for estimation of contamination of the environment by pesticides

Because excessive using of pesticides poses a threat to the environment and to human health, development of low-cost and sensitive methods for analysis of pesticides in the environment is needed. Several bacteria can release halide ions from the molecules of halogenated hydrocarbons. This can be used in a device for analysis of halogenated hydrocarbons in the environment by quantification of the halide anions. Here we directed our attention to selecting an instrument for detection of chloride anions. We tested three different detectors, amperometric, and coulometric, both coupled with flow-injection analysis and charged aerosol, coupled with high performance liquid chromatography. Detection limits (3 x S/N) for measurement of chloride anions by use of these detectors was 30 mu M (charged aerosol), 100 nM (coulometric), and 1 nM (amperometric). Because of its lowest detection limit for chloride anions and the many technical possibilities of miniaturization, the amperometric detector was used to test of effect of different cations on the chloride signal under the optimized experimental conditions (working electrode potential -365 mV; "Current R" 5 mu A; mobile phase 0.2 M phosphate buffer, pH 6; flow rate 0.5 mL min(-1)). NaCl, SrCl2, NH4Cl, and CsCl were tested as sources of chloride anions. We then used the detector to detect chloride anions catalytically cleaved from 1-chlorohexane by the enzyme haloalkane dehalogenase LinB from the bacterium Sphingobium japonicum UT26. The activity of the enzyme increased with increasing reaction temperature until the maximum was observed at 39 degrees C. The results obtained were in good agreement with data obtained by calorimetric detection

Electrochemical determination of Ag-ions in environment waters and their action on plant embryos

We utilized liquid chromatography coupled with electrochemical detector (HPLC-ED) for analyzing of silver ions. The optimization of basic chromatographic parameters has been done. The detection limit (3 S/N) obtained were 20 nmol/dm(3). Influence of different interferences (anions and cations) on current response of silver ions has been described. Moreover, we used HPLC-ED to analyze waters of different purity including 3 photographic emulsion, which naturally contained silver ions. We found out that content of silver ions in the emulsion was 1.57 x 0.03 mmol/dm(3). Moreover, we investigated influence of silver ions on early somatic embryos of Blue Spruce. We were interested in the issue how much silver ions can embryos uptake during four days long treatment. For this purpose, we used optimized HPLC-ED technique. The content increased with increasing treatment time and applied concentration. We also studied how silver ions can influence thiols content in the treated embryos. For these purposes we used adsorptive transfer stripping voltammetry in connection with differential pulse voltammetry - Brdicka reaction. It clearly follows from the obtained results that content of thiols increased with increasing treatment time and applied concentration. (c) 2007 Elsevier B.V. All rights reserved

Toxicological aspects of flavonoid interaction with biomacromolecules

OBJECTIVES: Flavonoids are widely accepted as health promoting phytochemicals, however, some flavonoids show ability of direct interaction with DNA and/or enhance carcinogen activation into DNA modifying agents. Thus, their potential harmful effect on the human body should be examined in detail. METHODS: Direct interaction of flavonoids (quercetin, rutin) with DNA was examined using square wave voltammetry on carbon paste electrode. Induction effect of selected flavonoids on content of cytochrome P450 1A1, carcinogens activating enzyme, in colon and liver microsomal samples of animals exposed to flavonoids was determined by Western blotting, using anti-cytochrome P450 lAl specific antibody. RESULTS: Of the natural flavonoids tested, induction of CYPIA1 was elicited by the typical citrus flavonoid naringenin in the colon, as well as by flavone in the liver. Moreover, synthetic (beta-naphthoflavone and naturally occurring chrysin, quercetin and diosmin induced CYP1A1 in both tissues. The oxidation signals of guanine and adenine in the DNA molecule were decreased in the presence of flavonoids. CONCLUSIONS: Although flavonoids are often considered to be safe because of their "plant origin"; ingestion of flavonoids should be taken with caution. Enhanced expression of CYPIA1 in colon tissue might be responsible for increasing incidence of colorectal carcinoma in humans. Electrochemistry can be used to study the interactions of flavonoids and DNA

Determination of isoflavones using liquid chromatography with electrochemical detection

Among the biologically important roles of isoflavones is also their effect on carcinogenesis. We used flow injection analysis and high performance liquid W with electrochemical detection to simultaneously determine certain isoflavones (biochanin A, formononetin, sissotrin, daidzin, daidzein, glycitin, glycitein and genistein). The most suitable chromatographic conditions were: mobile phase: 0.2 mol L-1 acetate buffer (pH 5.0); flow rate 2.0 mL min(-1); column and detector temperature: 26 degrees C; detection potential: 800 mV. Under the optimal conditions, the detection limits were in the range of several ng mL(-1). Their simultaneous determination takes 15 min

Utilizing of square wave voltammetry to detect flavonoids in the presence of human urine

About biological affecting of flavonoids on animal organisms is known less, thus we selected flavonoids, flavanones and flavones, and their glycosides, which were examined as potential inducers of cytochrome(s) P450 when administrated by gavages into experimental male rats. The study was focused on induction of CYP1A1, the major cytochrome P450 involved in carcinogen activation. The data obtained demonstrate the necessity of taking into account not only ability of flavonoids to bind to Ah receptor (induction factor) but also to concentrate on their distribution and metabolism (including colon microflora) in the body. After that we examined certain flavonoids as potential inducers of cytochrome P450, we wanted to suggest and optimize suitable electrochemical technique for determination of selected flavonoids (quercetin, quercitrin, rutin, chrysin and diosmin) in body liquids. For these purposes, we selected square wave voltannetry using carbon paste electrode. Primarily we aimed on investigation of their basic electrochemical behaviour. After that we have optimized frequency, step potential and supporting electrolyte. Based on the results obtained, we selected the most suitable conditions for determination of the flavonoids as follows: frequency 180 Hz, step potential 1.95 mV/s and phosphate buffer of pH 7 as supporting electrolyte. Detection limits (3 S/N) of the flavonoids were from units to tens of nM except diosmin, where the limit were higher than M. In addition, we attempted to suggest a sensor for analysis of flavonoids in urine. It clearly follows from the results obtained that flavonoids can be analysed in the presence of animal urine, because urine did not influence much the signals of flavonoids (recoveries of the signals were about 90 %)