Maurizio Quinto

Determination of aflatoxins in cereal flours by solid-phase microextraction coupled with liquid chromatography and post-column photochemical derivatization-fluorescence detection.

A new method for the determination of aflatoxins B(1), B(2), G(1), and G(2) (AFB(1), AFB(2), AFG(1), AFG(2)) in cereal flours based on solid-phase microextraction (SPME) coupled with high performance liquid chromatography with post-column photochemical derivatization and fluorescence detection (SPME-HPLC-PD-FD) has been developed. Aflatoxins were extracted from cereal flour samples by a methanol:phosphate buffer (pH 5.8, I=0.1) (80:20, v/v) solution, followed by a SPME step. Different SPME and HPLC-PD-FD parameters (fiber polarity, temperature, pH, ionic strength, adsorption and desorption time, mobile phase) have been investigated and optimized. This method, which was assessed for the analysis of different cereal flours, showed interesting results in terms of LOD (from 0.035 to 0.2 ng g(-1)), LOQ (from 0.1 to 0.63 ng g(-1), respectively), within and inter-day repeatability (2.27% and 5.38%, respectively) linear ranges (up to 20 ng g(-1) for AFB(1) and AFG(1) and 6 ng g(-1) for AFB(2) and AFG(2)), and total raw extraction efficiency (in the range 55-59% at concentrations in the range 0.3-1 ng g(-1) and 49-52% at concentrations in the range 1-10 ng g(-1)). The results were also compared with the purification step carried out by conventional immunoaffinity columns.

CHAPTER 16:Determination of Dietary Sugars by Ion Chromatography and Electrochemical Detection: a Focus on Galactose, Glucose, Fructose and Sucrose

In the last three decades, the elevated capabilities of high-performance anion-exchange chromatography (HPAEC) in the separation of carbohydrates was well established. HPAEC allows high resolution of closely related carbohydrates, and in conjunction with the electrochemical detection represents the technique of choice for sugars determination. Pulsed amperometric detection at a gold electrode is the most commonly used detection mode for analysis of carbohydrates. Otherwise, the electrochemical detection is performed by the application of a constant positive potential at chemically modified electrodes. nIn this paper, a comprehensive review of analytical methods based on ion chromatography and electrochemical detection, and applications to sugars determination is given, with a particular focus on the separation and detection of galactose, glucose, fructose and sucrose.

Fast on-fiber derivatization and GC/MS analysis of phytohormones in wheat based on pencil-type coated carbon fibers

New coated carbon fibers (CCFs) have been synthesized, characterized and used as solid phase microextraction (SPME) matrix for the analysis of phytohormones (jasmonic acid, indole-3-acetic acid, and abscisic acid) in wheat samples. The SPME device, realized inserting CCFs in a pencil-type device, when coupled with gas chromatography-mass spectrometry, provides in few steps high recovery values (79-112%), fast on-fiber derivatization (30u202fs), good method reproducibility (RSDu202f<u202f20%), low detection limits (0.5-2.1u202fngu202fg-1). The pencil-type CCFs-SPME device was successfully employed for the determination of phytohormone in wheat samples, allowing simple and quick extraction/derivatization/injection processes. The proposed device can be then considered as a promising and functional tool for fast and reliable extraction and preconcentration of analytes from real samples, allowing a simple derivatization procedure and direct injection in the chromatographic instrumentation.

Sensitive Screening Method for Determination of Pyrethroids in Chicken Eggs and Various Meat Samples by Gas Chromatography and Electron Capture Detection

A sensitive and reproducible screening analytical method is described for the determination of six pyrethroids (phenothrin, permethrin, cyfluthrin, cypermethrin, deltamethrin, fenvalerate) in egg and meat samples by gas chromatography and electron capture detection (GC-ECD). A fast cleanup procedure, based on solid-phase extraction has been used, ensuring reduced solvent consumption and time and allowing the simultaneous preparation of multiple sample extracts. Under the optimal chromatographic conditions, an efficient separation was obtained with a total analysis time of less than 60 min, including the extraction-purification steps. Good responses for the six pyrethroids were obtained in a range of 50-500 μg L-1, with linear coefficients higher than 0.9992. Instrumental limits of detection were between 0.22 and 0.63 μg L-1, corresponding to 0.04 and 0.13 μg kg-1 in the matrix. Detection limits in chicken eggs and various meat samples, calculated on spiked samples, were in the range 0.05-0.25 μg kg-1 and 0.07-0.23 μg kg-1, respectively. The validation results confirmed that the proposed GC-ECD method can be used as a reliable screening tool for the determination of pyrethroids in official check analyses. The method was extensively validated following the European directives, demonstrating its conformity in terms of selectivity, sensitivity, recovery, precision, and measurement uncertainty.

A high throughput mass spectrometry screening analysis based on two-dimensional carbon microfiber fractionation system

A novel high-throughput, solvent saving and versatile integrated two-dimensional microscale carbon fiber/active carbon fiber system (2DμCFs) that allows a simply and rapid separation of compounds in low-polar, medium-polar and high-polar fractions, has been coupled with ambient ionization-mass spectrometry (ESI-Q-TOF-MS and ESI-QqQ-MS) for screening and quantitative analyses of real samples. 2DμCFs led to a substantial interference reduction and minimization of ionization suppression effects, thus increasing the sensitivity and the screening capabilities of the subsequent MS analysis. The method has been applied to the analysis of Schisandra Chinensis extracts, obtaining with a single injection a simultaneous determination of 33 compounds presenting different polarities, such as organic acids, lignans, and flavonoids in less than 7min, at low pressures and using small solvent amounts. The method was also validated using 10 model compounds, giving limit of detections (LODs) ranging from 0.3 to 30ngmL-1, satisfactory recoveries (from 75.8 to 93.2%) and reproducibilities (relative standard deviations, RSDs, from 1.40 to 8.06%).