Search results for: Dimosthenis L. Giokas

Items from 1 to 20 out of 57 results

article

Intrinsic peroxidase-like activity of rhodium nanoparticles, and their application to the colorimetric determination of hydrogen peroxide and glucose

Tatiana G. Choleva, Vasiliki A. Gatselou, George Z. Tsogas, Dimosthenis L. Giokas

Microchimica Acta > 2018 > 185 > 1 > 1-9

The intrinsic peroxidase-like activity of rhodium nanoparticles (RhNPs) and their use as catalytic labels for sensitive colorimetric assays is presented. RhNPs catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H₂O₂ to produce a blue reaction product with a maximum absorbance at 652 nm. Kinetic studies show catalysis to follow Michaelis-Menten...

article

Calibrant-loaded paper-based analytical devices for standard addition quantitative assays

Foteini A. Kappi, George Z. Tsogas, Dionysios C. Christodouleas, Dimosthenis L. Giokas

Sensors and Actuators B: Chemical > 2017 > 253 > C > 860-867

This article describes a new approach for performing analytical assays on paper-based analytical devices that relies on the principles of multiple standard additions calibration, and uses calibrant-loaded paper devices. Calibrant-loaded devices have multiple sensing areas pre-loaded with an excess amount of the necessary colorimetric reagents and known amounts (standard solutions) of the tested analyte;...

article

Low-cost colorimetric assay of biothiols based on the photochemical reduction of silver halides and consumer electronic imaging devices

Foteini A. Kappi, George A. Papadopoulos, George Z. Tsogas, Dimosthenis L. Giokas

Talanta > 2017 > 172 > C > 15-22

This work describes a new approach for the determination of free biothiols in biological fluids that exploits some of the basic principles of early photographic chemistry — that was based on silver-halide recording materials — and uses broadly-available imaging devices (i.e. flatbed scanners) as detectors. Specifically, the proposed approach relies on the ability of biothiols to bind to silver ions...

article

Determination of gold nanoparticles in environmental water samples by second-order optical scattering using dithiotreitol-functionalized CdS quantum dots after cloud point extraction

Spyridoula P. Mandyla, George Z. Tsogas, Athanasios G. Vlessidis, Dimosthenis L. Giokas

Journal of Hazardous Materials > 2017 > 323 > PA > 67-74

This work presents a new method for the sensitive and selective determination of gold nanoparticles in water samples. The method combines a sample preparation and enrichment step based on cloud point extraction with a new detection motif that relies on the optical incoherent light scattering of a nano-hybrid assembly that is formed by hydrogen bond interactions between gold nanoparticles and dithiotreitol-functionalized...

article

Determination of phenolic compounds using spectral and color transitions of rhodium nanoparticles

Vasiliki Gatselou, Dionysios C. Christodouleas, Antonios Kouloumpis, Dimitrios Gournis, more

Analytica Chimica Acta > 2016 > 932 > C > 80-87

This work reports a new approach for the determination of phenolic compounds based on their interaction with citrate-capped rhodium nanoparticles. Phenolic compounds (i.e., catechins, gallates, cinnamates, and dihydroxybenzoic acids) were found to cause changes in the size and localized surface plasmon resonance of rhodium nanoparticles, and therefore, give rise to analyte-specific spectral and color...

article

Stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles–nylon 6 composite for the extraction of hydrophilic organic compounds in aqueous media

Juan L. Benedé, Alberto Chisvert, Dimosthenis L. Giokas, Amparo Salvador

Analytica Chimica Acta > 2016 > 926 > C > 63-71

A new and sensitive analytical method based on the recently developed approach termed stir bar-sorptive dispersive microextraction (SBSDME) using a magnetic CoFe₂O₄@SiO₂–nylon 6 composite as sorbent material is presented for the extraction of hydrophilic organic compounds. The simultaneous determination of four hydrophilic UV filters in environmental water samples has been chosen as a model analytical...

article

In-situ suspended aggregate microextraction of gold nanoparticles from water samples and determination by electrothermal atomic absorption spectrometry

Tatiana G. Choleva, Foteini A. Kappi, George Z. Tsogas, Athanasios G. Vlessidis, more

Talanta > 2016 > 151 > C > 91-99

This work describes a new method for the extraction and determination of gold nanoparticles in environmental samples by means of in-situ suspended aggregate microextraction and electrothermal atomic absorption spectrometry. The method relies on the in-situ formation of a supramolecular aggregate phase through ion-association between a cationic surfactant and a benzene sulfonic acid derivative. Gold...

article

Determination of ultraviolet filters in bathing waters by stir bar sorptive–dispersive microextraction coupled to thermal desorption–gas chromatography–mass spectrometry

Juan L. Benedé, Alberto Chisvert, Dimosthenis L. Giokas, Amparo Salvador

Talanta > 2016 > 147 > C > 246-252

In this work, a new approach that combines the advantages of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE), i.e. stir bar sorptive–dispersive microextraction (SBSDµE), is employed as enrichment and clean-up technique for the sensitive determination of eight lipophilic UV filters in water samples. The extraction is accomplished using a neodymium stir bar magnetically...

article

In-situ suspended aggregate microextraction: A sample preparation approach for the enrichment of organic compounds in aqueous solutions

Juan L. Benedé, Dimosthenis L. Giokas, Alberto Chisvert, Amparo Salvador

Journal of Chromatography A > 2015 > 1408 > Complete > 63-71

This work presents in-situ suspended aggregate microextraction (iSAME) as a new and expedient sample preparation method. This new concept capitalizes on the general principles of in-situ solvent formation microextraction, in the sense that extraction is carried out in a supramolecular aggregate phase, which is formed in-situ in the sample through one-step process involving ion-association between...

article

Paper-based assay of antioxidant activity using analyte-mediated on-paper nucleation of gold nanoparticles as colorimetric probes

Tatiana G. Choleva, Foteini A. Kappi, Dimosthenis L. Giokas, Athanasios G. Vlessidis

Analytica Chimica Acta > 2015 > 860 > Complete > 61-69

With the increasing interest in the health benefits arising from the consumption of dietary products rich in antioxidants, there exists a clear demand for easy-to-use and cost-effective tests that can be used for the identification of the antioxidant power of food products. Paper-based analytical devices constitute a remarkable platform for such expedient and low-cost assays with minimal external...

article

An automatic FIA-CL method for the determination of antioxidant activity of edible oils based on peroxyoxalate chemiluminescence

Dionysios C. Christodouleas, Dimosthenis L. Giokas, Vasiliki Garyfali, Kyriakos Papadopoulos, more

Microchemical Journal > 2015 > 118 > Complete > 73-79

The antioxidant activity of oils is an important parameter that determines oils' nutritional value and quality. To date, the methods for the determination of the antioxidant activity of oils are performed under batch conditions, therefore, they have large turnaround times and are labor-intensive. In this work, we describe the first automated method for the determination of the antioxidant activity...

article

Development of stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles and its analytical application to the determination of hydrophobic organic compounds in aqueous media

Juan L. Benedé, Alberto Chisvert, Dimosthenis L. Giokas, Amparo Salvador

Journal of Chromatography A > 2014 > 1362 > C > 25-33

A novel microextraction technique combining the principles of stir bar sorptive extraction (SBSE) and dispersive micro-solid phase extraction (DμSPE) is presented. The main feature of the method is the use of a neodymium-core stirring bar physically coated with a hydrophobic magnetic nanosorbent. Depending on stirring speed, the magnetic sorbent either acts as a coating material to the stir bar, thus...

article

Speciation of Fe(II) and Fe(III) by the modified ferrozine method, FIA–spectrophotometry, and flame AAS after cloud-point extraction

Dimosthenis L. Giokas, Evangelos K. Paleologos, Miltiades I. Karayannis

Analytical and Bioanalytical Chemistry > 2002 > 373 > 4-5 > 237-243

A method has been developed for the simultaneous determination of traces of Fe(III) and Fe(II) in water by on-line coupling of spectrophotometry with flame atomic absorption spectrometry (FAAS). The method involves cloud-point extraction (CPE) of both species with ammonium pyrrolidinecarbodithioate (APDC) under standard conditions, which facilitates the in situ complexation and extraction of both...

article

Ligand-free gold nanoparticles as colorimetric probes for the non-destructive determination of total dithiocarbamate pesticides after solid phase extraction

Kyriakos M. Giannoulis, Dimosthenis L. Giokas, George Z. Tsogas, Athanasios G. Vlessidis

Talanta > 2014 > 119 > Complete > 276-283

In this work, we describe a simple and sensitive non-destructive method for the determination of the total concentration of dithiocarbamate fungicides (DTCs) in real samples. The proposed method combines for the first time the benefits of an extraction method for sample clean-up and preconcentration with a sensitive colorimetric assay based on gold nanoparticle probes. In this two-step procedure,...

article

Colorimetric and visual read-out determination of cyanuric acid exploiting the interaction between melamine and silver nanoparticles

Foteini A. Kappi, George Z. Tsogas, Dimosthenis L. Giokas, Dionysios C. Christodouleas, more

Microchimica Acta > 2014 > 181 > 5-6 > 623-629

We present two colorimetric procedures for the determination of cyanuric acid, using silver nanoparticle-based (AgNPs) probes. The first is making use of melamine-modified AgNPs which bind to cyanuric acid through hydrogen bonding to form a large conjugate network that enhances the aggregation of AgNPs to produce an absorbance peak at 640 nm and a green coloration. In the second assay, melamine is...

article

A Family of Ru^II Photosensitizers with High Singlet Oxygen Quantum Yield: Synthesis, Characterization, and Evaluation

Eleftherios K. Pefkianakis, Dionysios Christodouleas, Dimosthenis L. Giokas, Kyriakos Papadopoulos, more

European Journal of Inorganic Chemistry > 2013 > 26 > 4628 - 4635

A series of Ru^II‐based photosensitizers were synthesized and extensively characterized. The ligand utilized to coordinate ruthenium was a pyridine–quinoline hybrid bearing an anthracene moiety, and it was combined with commercially available 2,2′‐bipyridine (bpy) for the heteroleptic complexes. The produced bichromophoric complexes show very strong and wide UV/Vis absorption bands. The ability of...

article

Development of a generic assay for the determination of total trihydroxybenzoate derivatives based on gold-luminol chemiluminescence

Dimosthenis L. Giokas, Dionysios C. Christodouleas, Ioanna Vlachou, Athanasios G. Vlessidis, more

Analytica Chimica Acta > 2013 > 764 > Complete > 70-77

A selective assay for the determination of one of the most important class of phenolic compounds, namely trihydroxybenzoates (monomeric and polymeric compounds having at least one gallate moiety) based on their enhancing effect on the chemiluminogenic reaction between gold ions and luminol is described for the first time. In the presence of trihydroxybenzoate derivatives, the light emission generated...

article

Surfactant-enhanced liquid-liquid microextraction coupled to micro-solid phase extraction onto highly hydrophobic magnetic nanoparticles

Kiriakos M. Giannoulis, Dimosthenis L. Giokas, Qing Zhu, George Z. Tsogas, more

Microchimica Acta > 2013 > 180 > 9-10 > 775-782

We are presenting a simplified alternative method for dispersive liquid-liquid microextraction (DLLME) by resorting to the use of surfactants as emulsifiers and micro solid-phase extraction (μ-SPE). In this combined procedure, DLLME of hydrophobic components is initially accomplished in a mixed micellar/microemulsion extractant phase that is prepared by rapidly mixing a non-ionic surfactant and 1-octanol...

article

Dispersive micro-solid phase extraction of ortho-phosphate ions onto magnetite nanoparticles and determination as its molybdenum blue complex

Kiriakos M. Giannoulis, George Z. Tsogas, Dimosthenis L. Giokas, Athanasios G. Vlessidis

Talanta > 2012 > 99 > Complete > 62-68

A direct microextraction method, employing dispersive micro-solid phase extraction (μ-SPE) of ortho-phosphate (o-PO ₄ ³⁻ ) anions onto ferromagnetic nanoparticles (MNPs) is described in this work for the first time. The method exploits the complexation of phosphate ions on the surface of positively charged magnetite nanoparticles through the formation of an inner sphere complex, which...

article

Cloud point–dispersive μ-solid phase extraction of hydrophobic organic compounds onto highly hydrophobic core–shell Fe2O3@C magnetic nanoparticles

Dimosthenis L. Giokas, Qing Zhu, Qinmin Pan, Alberto Chisvert

Journal of Chromatography A > 2012 > 1251 > C > 33-39

A novel two-step extraction technique combining cloud point extraction (CPE) with dispersive micro-solid phase extraction (D-μ-SPE) is presented in this work for the first time. The method involves initial extraction of the target analytes by CPE in the micelles of a non-ionic surfactant medium; then highly hydrophobic polysiloxane-coated core–shell Fe₂O₃@C magnetic nanoparticles (MNPs) are used to...

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Search results for: Dimosthenis L. Giokas

Intrinsic peroxidase-like activity of rhodium nanoparticles, and their application to the colorimetric determination of hydrogen peroxide and glucose

Calibrant-loaded paper-based analytical devices for standard addition quantitative assays

Low-cost colorimetric assay of biothiols based on the photochemical reduction of silver halides and consumer electronic imaging devices

Determination of gold nanoparticles in environmental water samples by second-order optical scattering using dithiotreitol-functionalized CdS quantum dots after cloud point extraction

Determination of phenolic compounds using spectral and color transitions of rhodium nanoparticles

Stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles–nylon 6 composite for the extraction of hydrophilic organic compounds in aqueous media

In-situ suspended aggregate microextraction of gold nanoparticles from water samples and determination by electrothermal atomic absorption spectrometry

Determination of ultraviolet filters in bathing waters by stir bar sorptive–dispersive microextraction coupled to thermal desorption–gas chromatography–mass spectrometry

In-situ suspended aggregate microextraction: A sample preparation approach for the enrichment of organic compounds in aqueous solutions

Paper-based assay of antioxidant activity using analyte-mediated on-paper nucleation of gold nanoparticles as colorimetric probes

An automatic FIA-CL method for the determination of antioxidant activity of edible oils based on peroxyoxalate chemiluminescence

Development of stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles and its analytical application to the determination of hydrophobic organic compounds in aqueous media

Speciation of Fe(II) and Fe(III) by the modified ferrozine method, FIA–spectrophotometry, and flame AAS after cloud-point extraction

Ligand-free gold nanoparticles as colorimetric probes for the non-destructive determination of total dithiocarbamate pesticides after solid phase extraction

Colorimetric and visual read-out determination of cyanuric acid exploiting the interaction between melamine and silver nanoparticles

A Family of Ru^II Photosensitizers with High Singlet Oxygen Quantum Yield: Synthesis, Characterization, and Evaluation

Development of a generic assay for the determination of total trihydroxybenzoate derivatives based on gold-luminol chemiluminescence

Surfactant-enhanced liquid-liquid microextraction coupled to micro-solid phase extraction onto highly hydrophobic magnetic nanoparticles

Dispersive micro-solid phase extraction of ortho-phosphate ions onto magnetite nanoparticles and determination as its molybdenum blue complex

Cloud point–dispersive μ-solid phase extraction of hydrophobic organic compounds onto highly hydrophobic core–shell Fe2O3@C magnetic nanoparticles

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