Showing papers by "Sandro Navickiene published in 2015"

Dual emission tunable in the near-infrared (NIR) and visible (VIS) spectral range by mix-LnMOF.

Abstract: In this study, we describe the synthetic approach, crystallographic structure, luminescent behavior and elucidation of the channels of the energy conversion in heteronuclear coordination polymers with emission in the visible (Eu(3+) and organic ligand) and near-infrared (Nd(3+)) range. The [(Nd0.9Eu0.1)2(dipc)3(H2O)3]n·nH2O, [(Nd0.7Eu0.3)2(dipc)3(H2O)3]n·nH2O, [(Nd0.5Eu0.5)2(dipc)3(H2O)3]n·nH2O, [(Nd0.3Eu0.7)2(dipc)3(H2O)3]n·nH2O, [(Nd0.1Eu0.9)2(dipc)3(H2O)3]n·nH2O, [Eu2(dipc)3(H2O)3]n·nH2O and [Nd2(dipc)3(H2O)3]n·nH2O materials are obtained by hydrothermal conditions from pyridine-2,6-dicarboxylic acid (H2dipc) and Ln2O3 oxide (Ln = Eu and Nd). The fine structures in the emission spectrum and spectral profile are used to investigate the ion responsible for the emission characteristics of a material (6), based on coordination polyhedron. The heteronuclear systems show emission in the dual spectral range (NIR-VIS) tuned for blue or red. The tuning of emission on the red (Eu(3+)) or blue (organic ligand) range may be performed by controlling the stoichiometric ratio of the lanthanide ions and by controlling the excitation wavelength. Nd(3+) ions display self-absorption of emission to dipc ligand, resulting in interference on the emission band profile ranging from 400 to 600 nm. The energetic process of energy transfer is operated by a cascade of energy transfer, from dipc ligand mainly to Eu(3+) ions and finishing on the Nd(3+) ion. The efficient sensitization to Nd(3+) by Eu(3+) ions is due to the presence of many resonant energy levels and the short distance between these ions.

Determination of pesticide residues in coconut tree trunks by modified QuEChERS method and ultra-high-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry

Abstract: A rapid and reliable method for the determination of 10 pesticide residues in coconut (Cocos nucifera L.) tree trunks after endotherapy treatments has been established. A modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method, using an homogeneous sample slurry and acetate buffer, followed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed and validated. Under the best extraction conditions, the average recoveries for all pesticides spiked at 40, 80 and 200 μg kg−1 ranged from 70 to 93%, with RSD <10%. Intermediate precision expressed as RSD, ranged between 3 and 6% for all compounds. Calibration curves showed a wide linear range between 10.0 and 1000.0 μg kg−1 for all compounds studied. Limit of quantification was established as 40.0 μg kg−1. The developed procedure was employed in the analysis of real coconut tree trunk samples obtained 45 h after pesticides application using endotherapy treatment. Concentrations of pesticides were between 44.7 ± 5 and 938.3 ± 20 μg kg−1. These results prove the translocation of pesticides in different heights, in the coconut tree trunk, from the application point. Imidacloprid presented the highest acropetal translocation and was found near the leaves at 61 ± 6 μg kg−1.

Evaluation of Metal-Organic Framework as Low-Cost Adsorbent Material in the Determination of Pesticide Residues in Soursop Exotic Fruit ( Annona muricata ) by Liquid Chromatography

Abstract: The metal-organic framework ∞[(Nd0.9Eu0.1)2(DPA)3(H2O)3] was tested for extraction of thiamethoxam, thiacloprid, thiophanate-methyl, teflubenzuron, and bifenthrin from soursop exotic fruit (Annona muricata), with analysis using liquid chromatography with UV diode array detector (DAD). Experiments were carried out at one fortification level (0.5 mg kg−1, n = 5) and resulted in recoveries in the range 78 to 88 %, with relative standard deviation (RSD) values between 2.2 and 8.0 % for ∞[(Nd0.9Eu0.1)2(DPA)3(H2O)3] sorbent. Detection and quantification limits were in the ranges 0.03–0.05 and 0.1–0.2 mg kg−1, respectively, for the different pesticides studied. The method developed was linear over the range tested (0.08–100 mg kg−1), with correlation coefficients ranging from 0.9995 to 0.9999. Comparison between ∞[(Nd0.9Eu0.1)2(DPA)3(H2O)3] and conventional sorbent (Florisil) showed similar performance of ∞[(Nd0.9Eu0.1)2(DPA)3(H2O)3] polymeric sorbent for all pesticides tested.