Konstantinos Fytianos

This study aimed on the development of a SPE-UHPLC-MS/MS method for the simultaneous determination of pesticide residues in drinking water samples. A chemometric approach was applied to optimize the efficiency of the SPE pretreatment procedure. This study involved (i) the application of a Full Factorial Design for the screening of the significant factors, (ii) the application of a Central Composite Design for the determination of the optimal conditions and (iii) the evaluation and validation of the significance of the statistically proposed models. Oasis HLB cartridges were used for the extraction. The optimum sample volume was 300 mL and the elution solvent 3 mL of the mixture of methanol:ethylacetate 70:30 v/v. The method was validated according to the international guidelines. Recoveries were ranged from 63 to 116% and the detection limits were between 0.1 and 1.5 pg mL^− 1. The validated method could be used in routine analysis for pesticides screening.

In the present report, the oxidative degradation of an endocrine-disrupting compound triadimenol has been investigated using the photo-Fenton reaction. Different reaction conditions that affected the degradation kinetics were examined including the iron (Fe²⁺) ions and hydrogen peroxide (H₂O₂) concentrations, the initial concentration of triadimefon, and the type of iron salt. The degradation rates proved to be strongly influenced by the above parameters. The reaction conditions in terms of Fe²⁺ and H₂O₂ concentrations were systematically studied and optimized using an experimental design through central composite design. The kinetics of the process can be characterized as pseudo-first-order. As iron and hydrogen peroxide concentrations increase, the degradation rate of triadimenol accelerates and complete degradation can be achieved after a short time of illumination. The effectiveness of the five different iron salts on the degradation performance were also investigated. Experiments with longer time illumination can lead to complete mineralization and detoxification of triadimenol solutions. The properties of the proposed oxidative degradation scheme make it a promising candidate for wastewater treatment.

The pulp and paper industry have historically been one of the world’s largest consumers of freshwater resources and producers of wastewater discharges. More than 250 chemicals have been identified in effluents including chlorine-based organic and other toxic compounds. Some of these are resistant to biological degradation such as color-related compounds. The goal of this study was to analyze the real wastewater from the paper mill and to suggest a photocatalytic treatment method in order to reduce the organic pollutants load. The efficiency of the commonly used treatment photocatalytic processes (photo-TiO₂ and photo-Fenton reagent) on the treatment of real paper mill effluent was investigated. Additionally, the performance of TiO₂ photocatalytic reactions with and without the addition of hydrogen peroxide was also examined. For the experiment, a 500 mL pyrex UV reactor and a 125-W high-pressure mercury lamp, surrounded by pyrex filter blocking wavelengths below 290 nm were used. The approach has been applied for the treatment of effluents produced from a papermaking industry.

An automated flow method for the determination of hydrazine based on the concept of zone-fluidics has been developed. The analyte reacts under flow conditions with p-dimethylamino benzaldehyde (25 mmol L⁻¹) in micellar medium (100 mmol L⁻¹ SDS) to form a stable derivative (460 nm). Micelles mediated catalysis excludes the use of highly acidic environment typical for this kind of reaction. Following careful examination of chemical and instrumental variables, the method allows the determination of hydrazine at the low micromolar level (0.3–10 μmol L⁻¹) in water samples. Real sample analyses (drinking and boiler feed water) resulted in satisfactory results in terms of accuracy with the percent recoveries being in the range of 82–114%.

Residues of organophosphorus insecticides (diazinon, methyl parathion, fenitrothion, malathion, and parathion) were determined in 13 different vegetable matrixes by headspace solid- phase microextraction performed with a polydimethyl-siloxane fiber (100 m). Determination was carried out by gas chromatography with a nitrogen-phosphorus detector. Limits of detection and quantification were <0.005 and 0.017 mg/kg, respectively; thus, the limits of maximum residue levels (MRLs) required by European regulations can be verified without difficulty. Pesticide residues were found in 38% of the 125 fresh commercial samples (imported and domestic) that were analyzed. Residues of methyl parathion and parathion, which were withdrawn in Greece in 2003, were detected in 36.8 and 4% of all samples, respectively. The MRLs were exceeded overall by 1%.

Laboratory studies were conducted to determine the effect of pH and redox conditions, as well as the effect of Fe, Mn, Ca, Al, and organic matter, on the release of ortho‐phosphates in lake sediments taken from Lakes Koronia and Volvi (Northern Greece). Results were evaluated in combination with experiments to determine P fractionation in the sediment. The study revealed the major effect of redox potential and pH on the release of P from lake sediments. Both lakes showed increased release rates under reductive conditions and high pH values. The fractionation experiments revealed increased mobility of the reductive P fraction as well as of the NaOH‐P fraction, indicating participation of both fractions in the overall release of sediment‐bound P, depending on the prevailing environmental conditions. The results were assessed in combination with the release patterns of Fe, Mn, Ca, Al, and organic matter, enabling the identification of more specific processes of P release for each lake. The basic release patterns included the redox induced reductive dissolution of P‐bearing metal oxides and the competitive exchange of phosphate anions with OH⁻ at high pH values. The formation of an oxidized surface microlayer under oxic conditions acted as a protective film, preventing further P release from the sediments of Lake Volvi, while sediments from Lake Koronia exhibited a continuous and increased tendency to release P under various physicochemical conditions, acting as a constant source of internal P loading.