E. Visi

Bio: E. Visi is an academic researcher. The author has contributed to research in topics: Gas chromatography & Electron capture detector. The author has an hindex of 1, co-authored 1 publications receiving 102 citations.

Molecularly Imprinted Silica Nanospheres Embedded CdSe Quantum Dots for Highly Selective and Sensitive Optosensing of Pyrethroids

Abstract: This paper reports the molecularly imprinted polymer (MIP)-based fluorescence nanosensor which is developed by anchoring the MIP layer on the surface of silica nanospheres embedded CdSe quantum dots (QDs) via a surface molecular imprinting process. The molecularly imprinted silica nanospheres (CdSe@SiO2@MIP) were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), IR spectroscopy, and so forth, which demonstrated the formation of uniform core−shell lambda-cyhalothrin(LC)-imprinted silica nanospheres. The synthesized CdSe@SiO2@MIP shows higher photostability, and allows a highly selective and sensitive determination of LC via FL intensity decreasing when removal of the original templates. The CdSe@SiO2@MIP was applied to detect trace LC in water without the interference of other pyrethroids and ions. Under optimal conditions, the relative FL intensity of CdSe@SiO2@MIP decreased linearly with the increasing LC in the concentration in the range of 0.1−1000 μM with a d...

Extension of the QuEChERS Method for Pesticide Residues in Cereals to Flaxseeds, Peanuts, and Doughs†

Abstract: A simple method was evaluated for the determination of pesticide residues in flaxseeds, doughs, and peanuts using gas chromatography−time-of-flight mass spectrometry (GC-TOF) for analysis. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, which was previously optimized for cereal grain samples, was evaluated in these fatty matrices. This extraction method involves first mixing the sample with 1:1 water/acetonitrile for an hour to swell the matrix and permit the salt-out liquid−liquid partitioning step using anhydrous MgSO4 and NaCl. After shaking and centrifugation, cleanup is done by dispersive solid-phase extraction (d-SPE) using 150 mg of anhydrous MgSO4, 150 mg of PSA, and 50 mg of C-18 per milliliter of extract. This method gave efficient separation of pesticides from fat and removal of coextracted substances better than gel permeation chromatography or use of a freeze-out step, which involved excessive use of solvent and/or time. The optimized analytical conditions were e...

Determination of pesticide residues in olive oil and olives

Abstract: Pesticide-residue determination in olive oil is becoming a very important and challenging issue. The present article provides a review of the most significant methods for determining pesticides in olive oil. The discussion of sample-treatment procedures is focused on not only the final product (olive oil), but also the direct analysis of the raw material (olive fruits). We outline extraction and clean-up procedures (e.g., liquid-liquid partition, gel-permeation chromatography (GPC), solid-phase extraction (SPE), matrix solid-phase dispersion (MSPD) and Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS). However, we pay specially attention to the clean-up stage, which plays an important role in the whole process. In addition, identification and quantitation of pesticides have been carried out by gas chromatography (GC) coupled to different detectors (flame-ionization (FID), nitrogen-phosphorus (NPD) and electron-capture (ECD), although either GC-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode or GC-tandem MS (GC-MS2) are becoming the combination of choice, because of higher selectivity and confirmation capabilities. In recent years, the appearance of new, more polar pesticides has prompted the use of liquid chromatography-MS (LC-MS) instead of GC-MS, and we outline its advantageous features for the analyses of polar pesticides in olive oil.