Δημοσιεύσεις σε Περιοδικά

Μόνιμο URI για αυτήν τη συλλογήhttps://dspace.library.tuc.gr/handle/123456789/135

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Fast screening of perfluorooctane sulfonate in water using vortex-assisted liquid-liquid microextraction coupled to liquid chromatography-mass spectrometry
(Elsevier, 2011) Elefteria Psillakis; Antonio Canals; Konstantina Tyrovola; Iván P. Román; Aikaterini Papadopoulou
Fast screening of trace amounts of the perfluorooctane sulfonate anion (PFOS) in water samples was performed following a simple, fast and efficient sample preparation procedure based on vortex-assisted liquid–liquid microextraction (VALLME) prior to liquid chromatography–mass spectrometry. VALLME initially uses vortex agitation, a mild emulsification procedure to disperse microvolumes of octanol, a low density extractant solvent, in the aqueous sample. Microextraction under equilibrium conditions is thus achieved within few minutes. Subsequently, centrifugation separates the two phases and restores the initial microdrop shape of the octanol acceptor phase, which can be collected and used for liquid chromatography–single quadrupole mass spectrometry analysis. Several experimental parameters were controlled and the optimum conditions found were: 50L of octanol as the extractant phase; 20mL aqueous donor samples (pH = 2); a 2 min vortex extraction time with the vortex agitator set at a 2500rpm rotational speed; no ionic strength adjustment. Centrifugation for 2 min at 3500rpm yielded separation of the two phases throughout this study. Enhanced extraction efficiencies were observed at low pH which was likely due to enhanced electrostatic interaction between the negatively PFOS molecules and the positively charged octanol/water interface. The effect of pH was reduced in the presence of sodium chloride, likely due to electrical double layer compression. The linear response range for PFOS was from 5 to 500 ng L−1 (coefficient of determination, r2, 0.997) and the relative standard deviation for aqueous solutions containing 10 and 500 ng L−1 PFOS were 7.4% and 6.5%, respectively. The limit of detection was 1.6 ng L−1 with an enrichment factor of approximately 250. Analysis of spiked tap, river and well water samples revealed that matrix did not affect extraction
An ionic liquid as a solvent for headspace single drop microextraction of chlorobenzenes from water samples
(Elsevier, 2007) Elefteria Psillakis; Lorena Vidal; Nuria Grané; Frank Marken; Antonio Canals
A headspace single-drop microextraction (HS-SDME) procedure using room temperature ionic liquid and coupled to high-performance liquid chromatography capable of quantifying trace amounts of chlorobenzenes in environmental water samples is proposed. A Plackett–Burman design for screening was carried out in order to determine the significant experimental conditions affecting the HS-SDME process (namely drop volume, aqueous sample volume, stirring speed, ionic strength, extraction time and temperature), and then a central composite design was used to optimize the significant conditions. The optimum experimental conditions found from this statistical evaluation were: a 5 L microdrop of 1-butyl-3- methylimidazolium hexafluorophosphate, exposed for 37 min to the headspace of a 10mL aqueous sample placed in a 15mL vial, stirred at 1580 rpm at room temperature and containing 30% (w/v) NaCl. The calculated calibration curves gave a high level of linearity for all target analytes with correlation coefficients ranging between 0.9981 and 0.9997. The repeatability of the proposed method, expressed as relative standard deviation, varied between 1.6 and 5.1% (n = 5). The limits of detection ranged between 0.102 and 0.203 gL−1. Matrix effects upon extraction were evaluated by analysing spiked tap and river water as well as effluent water samples originating from a municipal wastewater treatment plant.
Microwave assisted headspace single-drop microextration of chlorobenzenes from water samples
(Elsevier, 2007) Elefteria Psillakis; Claudia E. Domini; Lorena Vidal; Antonio Canals; Nuria Gran
Aone-step and in-situ sample preparation method used for quantifying chlorobenzene compounds inwater samples has been developed, coupling microwave and headspace single-drop microextraction (MW-HS-SDME). The chlorobenzenes in water samples were extracted directly onto an ionic liquid single-drop in headspace mode under the aid of microwave radiation. For optimization, a Plackett–Burman screening design was initially used, followed by a mixed-level factorial design. The factors considered were: drop volume, aqueous sample volume, stirring speed, ionic strength, extraction time, ionic liquid type, microwave power and length of the Y-shaped glass-tube. The optimum experimental conditions found from this statistical evaluation were: a 5 L microdrop of 1-hexyl-3-methylimidazolium hexafluorophosphate exposed for 20 min to the headspace of a 30mL aqueous sample, irradiated by microwaves at 200W and placed in a 50mL spherical flask connected to a 25 cm Y-shaped glass-tube. Under the optimised experimental conditions, the response of a high performance liquid chromatographic system was found to be linear over the range studied and with correlation coefficients ranging between 0.9995 and 0.9999. The method showed a good level of repeatability, with relative standard deviations varying between 2.3 and 8.3% (n = 5). Detection limits were found in the low gL−1 range varying between 0.016 and 0.039gL−1. Overall, the performance of the proposed method demonstrated the favourable effect of microwave sample irradiation upon HS-SDME. Finally, recovery studies from different types of environmental water samples revealed that matrix had little effect upon extraction
Rapid determination of octanol-water partition coefficient using vortex-sssisted liquid-liquid microextraction
(Elsevier, 2014) Elefteria Psillakis; Antonio Canals; Konstantina Tyrovola; Anna Mastromichali; Iván P Román
Abstract Vortex-assisted liquid–liquid microextraction (VALLME) coupled with high- performance liquid chromatography (HPLC) is proposed here for the rapid determination of octanol–water partitioning coefficients (K ow). VALLME uses vortex agitation, a mild emulsification procedure, to disperse microvolumes of octanol in the aqueous phase thus increasing the interfacial contact area and ensuring faster partitioning rates. With VALLME, 2 min were enough to achieve equilibrium conditions between the octanolic and aqueous .

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Πλοήγηση Δημοσιεύσεις σε Περιοδικά ανά Συγγραφέα "Antonio Canals"