Roxani Tzimou-Tsitouridou

Study of interactions between DNA-ethidium bromide (EB) and dna-acridine orange (AO), in solution, using hanging mercury drop electrode (HMDE)

The interaction of ethidium bromide (EB) and acridine orange (AO) with double stranded (ds), thermally denatured (ss) and supercoiled (sc) DNA, in solution, was studied by alternating current voltammetry (AC voltammetry) at the hanging mercury drop electrode (HMDE) in 0.3 M NaCl+50 mM sodium phosphate buffer (pH 8.5). Their interaction with DNA is shown to be time dependent and completely different. The changes at peak 2 (peak at -1.20 V) of dsDNA form and the appearance of peak 3 (peak at -1.42 V) in scDNA form are presented as criteria declaring the different mechanism of interaction of EB and AO with DNA. Additionally, the appearance of a new peak at around -0.44 V as a result of DNA and AO interaction, differentiates the studied behaviors. The comparison of the electrochemical behaviors of these compounds highlights the differences in the mechanism of interaction.

Study of interactions between actinomycin D and DNA on carbon paste electrode (CPE) and on the hanging mercury drop (HMDE) surface

The interaction of actinomycin (ACTD) with double stranded (ds) calf thymus DNA and single stranded (ss) DNA was studied at the carbon paste electrode surface by means of transfer voltammetry in 0.2 M phosphate buffer solution (pH 7.4). Accordingly the interaction of actinomycin (ACTD) with ds calf thymus DNA, ss DNA and supercoiled (sc) DNA was studied using hanging mercury drop electrode in 0.3 M NaCl, and 50 mM sodium phosphate buffer (pH 8.5). The different electrochemical behaviours are presented and compared in the article.

Laboratory and field dissipation of penoxsulam, tricyclazole and profoxydim in rice paddy systems

Rice cultivation relies on pesticide applications to ensure high yields. However, the regular use of pesticides seriously affects the quality of neighboring surface water systems. Thus complete knowledge of the environmental fate and dissipation of pesticides in the paddy rice environment should become available. So far only a few studies have provided comprehensive assessment of the dissipation of pesticides under the submerged cultivation conditions followed in rice. Thus, laboratory and 2-year field studies were performed to assess the dissipation of two new generation rice herbicides (penoxsulam and profoxydim) and one of the most important rice fungicides (tricyclazole). A good agreement between laboratory and field experiments was observed with a faster dissipation of penoxsulam and tricyclazole under field conditions. Profoxydim was the least persistent chemical (DT50 soil<1d; DT50 water 0.5-1.2d), followed by penoxsulam which persisted for longer particularly in the water compartment (DT50water=3.8-5.9d). Tricyclazole was the most persistent pesticide, especially in the soil compartment with DT50 values of 44.5-84.6 (field) and 197d (laboratory). These results could be utilized for the assessment of the environmental risk associated with the use of those pesticides in rice cultivation and the determination of potential mitigation measures for minimizing the risk for contamination of neighboring natural water resources.

Development and validation of an HPLC-DAD method for the simultaneous determination of most common rice pesticides in paddy water systems

Rice crop is mainly cultivated in large river basins which constitute unique ecosystems and their ecological quality is invaluable. However, the high loads of pesticides used in rice cultivation contribute to the contamination of the water resources in such rice-cultivated regions. To regularly monitor the quality of such water resources there is a need for a rapid and sensitive multi-residue analytical method. This study presents the development and validation of a new analytical method for the simultaneous determination of most rice pesticides including penoxsulam, tricyclazole, propanil and its main metabolite 3,4-dichloroaniline, azoxystrobin, molinate, profoxydim and deltamethrin. A solid-phase extraction (SPE) procedure followed by high performance liquid chromatography (HPLC) with diode array detection (DAD) was used. A C18 RP column operated at 30°C was utilised and the analytes were separated with a mobile phase of acetonitrile/water mixture in a linear gradient. Clean-up of water samples and isolation of pesticides was performed on SPE Bakerbond octadecyl cartridges and an ethyl acetate-dichlomethane mixture (9 : 1 v/v, 2 mL) was used for elution. Method validation was performed by means of intra-day (n = 5) and inter-day accuracy and precision (n = 8), sensitivity and linearity. The relative recoveries of the pesticides in paddy water samples were acceptable (80.6–110.2%) and the relative standard deviation (RSD%) ranged from 1.9 to 7.6%. Limits of detection (LOD) and limits of quantification (LOQ) varied from 0.1 to 0.8 ng mL−1 and 0.25 to 2.0 ng mL−1 respectively, depending on the analyte. The method was subsequently applied for the determination of pesticide residues in paddy and canal water samples. Tricyclazole was the most frequently detected pesticide at the highest concentrations, while herbicides were less frequently detected and at lower concentrations. The method described could be a valuable tool for regular monitoring of surface water systems in rice-cultivated basins.

Electrochemical DNA Biosensors Applicable to the Study of Interactions Between DNA and DNA Intercalators

Electrochemical DNA biosensors, based either on carbon paste electrode (CPE) or hanging mercury drop electrode (HMDE) were prepared. These biosensors were used in the study of interaction between double stranded DNA (dsDNA) and single stranded DNA (ssDNA) and acridine orange, a well known DNA intercalator. The different electrochemical behaviors were compared in the article.

Adsorptive transfer stripping voltammetry applied to the study of the interaction between DNA and actinomycin D

Actinomycin D is an antitumor antibiotic which intercalates within DNA. The interaction of actinomycin D with double-stranded and thermally denatured (single-stranded) calf thymus DNA was studied in solution as well as at the electrode surface using differential pulse transfer voltammetry with carbon paste electrode in 0.2 M acetate buffer, pH 5.0.

A new TISAB with aluminon for fluoride determination in water with ion-selective electrode

Abstract The application of a new TISAB solution with Aluminon as a complexing agent for the determination of fluoride with a fluoride ion-selective electrode in various water samples has been studied. The proposed TISAB has been compared to some of the well-known TISABs in the literature, since it concerns the linear response and equilibrium time of the electrode, as well as the effectiveness on complexation of Al3+, Fe3+, Mg2+, and Ca2+. The experimental results showed that the use of TISAB-Aluminon results in high sensitivity of the electrode in low fluoride concentrations, short equilibrium time, and equal or better ability to eliminate the interferences of the cations mentioned.

PM10 emissions and PAHs: the importance of biomass type and combustion conditions.

ABSTRACT The aim of the present work was to investigate the impact of biomass combustion with respect to conditions and fuel types on particle emissions (PM10) and their PAHs content. Special concern was on sampling, quantification and characterization of PM using different appliances, fuels and operating procedures. For this purpose different lab-scale burning conditions, two pellets stoves (8.5 and 10 kW) and one open fireplace were tested by using eight fuel types of biomass. An analytical method is described for the quantitative determination of 16 PAHs using liquid-liquid extraction and subsequent measurement by gas chromatography coupled to a mass spectrometer (GC-MS). Average PM10 emissions ranged from about 65 to 170 mg/m3 at lab-scale combustions with flow oxygen at 13% in the exhaust gas, 85–220 mg/m3 at 20% O2, 47–83 mg/m3 at pellet stove of 10 kW, 34–69 mg/m3 at pellet stove of 8.5 kW and 106–194 mg/m3 at the open fireplace. The maximum permitted particle emission limit is 150 mg/m3. Pellets originated from olive trees and from nonmixture trees were found to emit the lowest particulate matter in relation to the others, so they are considered healthiest and suitable for domestic heating reasons. In general, the results show that biomass open burning is an important PM10 and PAHs emission source.

Differentiations in the Electrochemical Behavior of the Interactions Between DNA and Compounds with Affinity for DNA

Abstract The interest of developing sensors for medical use is growing rapidly. The potential clinical applications of such devices are enormous and they are expected to have a major impact on health care. Especially, electrochemical DNA biosensors are hoped to be applied to the detection of toxic compounds presenting affinity for DNA, to drug design, gene delivery, and to the detection of infectious or inherited diseases. †In memory of Professor Harry Mark, Jr.

Analytical Methodologies for the Assessment of Phthalate Exposure in Humans

ABSTRACT Screening and quantification of phthalate metabolites in biological matrices provide information on the phthalate exposure. The preferred tool for the determination of phthalate metabolites is liquid chromatography–mass spectrometry, typically preceded by a sample extraction step. Method development for the determination of phthalate metabolites by hyphenated techniques faces challenges due to the widespread occurrence of phthalates in the laboratory and sample collection materials that impairs their accurate quantification. Here, the analytical methods that have been developed for the determination of biomarkers of phthalates in various matrices are presented, and limitations and challenges in these applications are discussed.