Determination of aflatoxins in olive oil by liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometric with electrospray ionization (LC/ESI-MS/MS) method for determining the four naturally occurring aflatoxins (AFs) B1, B2, G1, and G2 in olive oil is proposed. AFs were extracted from oil sample by means of matrix solid phase dispersion (MSPDE), utilizing C18 as dispersing material. No further purification step, such as lipid removal, was performed. Aflatoxin M1, the hepatic metabolite of AFB1, was employed as internal standard. Olive oil extract was analyzed by LC/ESI-MS/MS in positive ionization mode, with multireaction monitoring acquisition. Due to a signal suppression ranging between 4 and 23%, quantitation was performed by matrix-matched calibration curves. The regression line coefficients of determination were above 0.9991. Sample recoveries ranged from 92 to 107%, with relative standard deviations below 13% for spiking levels between 0.5 and 5 ng g⁻¹; method quantification limits ranged between 0.04 and 0.12 ng g⁻¹. The developed LC/ESI-MS/MS method, although not as sensitive as LC coupled to fluorescence detection, is rapid, selective, accurate and precise, thus it can be used as confirmatory assay. The MSPDE appears suitable for application to other oleaginous matrices and for multiresidue investigation.     

On the intrinsic population of the lowest triplet state of thymine

The population of the lowest triplet state of thymine after near-UV irradiation has been established, on the basis of CASPT2//CASSCF quantum chemical calculations, to take place via three distinct intersystem crossing mechanisms from the initially populated singlet bright 1pipi* state. Two singlet-triplet crossings have been found along the minimum-energy path for ultrafast decay of the singlet state at 4.8 and 4.0 eV, involving the lowest 3npi* and 3pipi* states, respectively. Large spin-orbit coupling elements predict efficient intersystem crossing processes in both cases. Another mechanism involving energy transfer from the lowest 1npi* state with much larger spin-orbit coupling terms can also be proposed. The wavelength dependence measured for the triplet quantum yield of pyrimidine nucleobases is explained by the location and accessibility of the singlet-triplet crossing regions.     

UPLC-UV-MSE analysis for quantification and identification of major carotenoid and chlorophyll species in algae

A fast method for quantification and identification of carotenoid and chlorophyll species utilizing liquid chromatography coupled with UV detection and mass spectrometry has been demonstrated and validated for the analysis of algae samples. This method allows quantification of targeted pigments and identification of unexpected compounds, providing isomers separation, UV detection, accurate mass measurements, and study of fragment ions for structural elucidation in a single run. This is possible using parallel alternating low- and high-energy collision spectral acquisition modes, which provide accurate mass full scan chromatograms and accurate mass high-energy chromatograms. Here, it is shown how this approach can be used to confirm carotenoid and chlorophyll species by identification of key diagnostic fragmentations during high-energy mode. The developed method was successfully applied for the analysis of Dunaliella salina samples during defined red LED lighting growth conditions, identifying 37 pigments including 19 carotenoid species and 18 chlorophyll species, and providing quantification of 7 targeted compounds. Limit of detections for targeted pigments ranged from 0.01?ng/mL for lutein to 0.24?ng/mL for chlorophyll a. Inter-run precision ranged for of 3 to 24 (RSD%) while inter-run inaccuracy ranged from ?17 to 11.

Solvent-free,microwave-assisted synthesis of thiophene oligomers via Suzuki coupling

The purpose of this study was to obtain a rapid, efficient, and environmentally friendly methodology for the synthesis of highly pure thiophene oligomers. The solvent-free, microwave-assisted coupling of thienyl boronic acids and esters with thienyl bromides, using aluminum oxide as the solid support, allowed us to rapidly check the reaction trends on changing times, temperature, catalyst, and base and easily optimize the experimental conditions to obtain the targeted product in fair amounts. This procedure offers a novel, general, and very rapid route to the preparation of soluble thiophene oligomers. Thus, for example, quaterthiophene was obtained in 6 min by reaction of 2-bromo-2,2'-bithiophene with bis(pinacolato)diboron (isolated yield 65%), whereas quinquethiophene was obtained in 11 min by reaction of dibromoterthiophene with thienylboronic acid (isolated yield 74%). The synthesis of new chiral 2,2'-bithiophenes is reported. The detailed analysis of the byproducts of some reactions allowed us to elucidate a few aspects of reaction mechanisms. While the use of microwaves proved to be very convenient for the coupling between conventional thienyl moieties, the same was not true for the coupling of thienyl rings to thienyl-S,S-dioxide moieties. Indeed, in this case, the targeted product was obtained in low yields because of the competitive, accelerated, Diels-Alder reaction that affords a variety of condensation products.     

A New Cells‐Compatible Microfluidic Device for Single Channel Recordings

We report the fabrication of a microfluidic apparatus and the realization of a sensors based on PEDOT : PSS, a biocompatible semiconductor polymer used in substitution of standard electrodes for electrophysiological studies and for detection of nanopores in membrane. This gives the possibility to study the mechanisms of ions balance and molecular transport though cell membranes. In particular the apparatus is based on two chambers connected through an aperture in a PTFE sheet where lipid bilayer are formed using Montal‐Mueller method, and the pore‐forming proteins activity is detected by polymeric electrodes. This methodology could be applied to examine different membrane proteins for the purpose of biosensing, drug screening and nanopore technologies.     

L‐lysine and EDTA polymer mimics as resins for the quantitative and reversible removal of heavy metal ion water pollutants

Traditional precipitation methods for inorganic micropollutant removal from waters are increasingly being replaced by sorption methods based on both natural and synthetic materials. In this context, two novel effective heavy metal ions absorbers are presented. These resins, LYMA and LMT85, were crosslinked poly(amidoamine)s carrying amine and carboxyl groups in their repeating units. In particular, the LYMA‐repeating unit contains one carboxyl and two amine groups and is a mimic of L ‐lysine, whereas LMT85 contains two amine and five carboxyl groups and is a mimic of EDTA. Both resins were prepared at moderate cost by simple eco‐friendly procedures. The heavy metal ion set adopted as benchmark was Cu²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Ni²⁺, and Co²⁺. LYMA proved selective for Cu²⁺ and Ni²⁺, the other ions tested being negligibly absorbed, whereas LMT85 proved capable of rapidly and quantitatively absorbing all the ions tested either singly or in mixed solution. The absorption process was reversible, and the resins were easily regenerated by acidification. The absorption of several metal ions imparted intense coloring to the resins, a feature possibly exploitable for analytical purposes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

1-ethynylpyrene-modified guanine and cytosine as optical labels for DNA hybridization

1-ethynylpyrene shows remarkable absorption changes upon DNA hybridization when it is covalently attached to the 8-position of guanine. An absorption band at approximately 420 nm is only present in the duplex, exhibits thermal melting behaviour and provides the basis for a molecular beacon together with 1-ethynylpyrene-modified cytosine.     

Quantification of arecoline (areca nut alkaloid) in neonatal biological matrices by high-performance liquid chromatography/electrospray quadrupole mass spectrometry

A high-performance liquid chromatography (HPLC) method with mass spectrometric detection is described for determination of arecoline in newborn meconium, urine and cord serum, using pilocarpine as internal standard. The analytes were extracted from neonatal biological matrices with chloroform/isopropanol (95:5, v/v) at alkaline pH. Extracts were analyzed by HPLC coupled to an electrospray (ESI) interface and a quadrupole mass spectrometer. Chromatography was performed on a C(8) reversed-phase column using 10 mM ammonium acetate (pH 4.3)/acetonitrile (90:10, v/v) as mobile phase. The mass spectrometer was operated in selected ion monitoring mode. The method was validated over the concentration range 0.005-1.00 micro g/g meconium, 0.004-1.00 micro g/mL cord serum and 0.001-1.00 micro /mL urine. Mean recoveries ranged between 86.5 and 90.7% for arecoline in the different biological matrices, with precision always better than 10%. The quantification limits of arecoline were 0.005 micro g/g meconium, 0.004 micro g/mL cord serum, and 0.001 micro g/mL urine. The method was applied to the analysis of neonatal biological matrices to assess eventual fetal exposition to arecoline. Two newborns from Asian mothers who declared areca nut consumption presented arecoline in meconium with concentrations in the range 0.006-0.008 micro g/g; also the urine from one neonate tested positive for the drug.