Flavio Della Pelle

Determination of Pesticides in Wheat Flour Using Microextraction on Packed Sorbent Coupled to Ultra-High Performance Liquid Chromatography and Tandem Mass Spectrometry

An ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) method for multiclass analysis of pesticide and fungicide residues in wheat flour based is presented. An efficient and rapid cleanup based on microextraction by packed sorbent (MEPS) has been developed in order to have a good enrichment factor together with a low matrix effect. The target analytes were 25 pesticides widely used in wheat, with different physico-chemical characteristics and different mechanism of action: acetylcholinesterase inhibitors such as organophosphorus, carbamates, neonicotinoids, and inhibitors of ergosterol such as imidazoles and triazoles. MEPS was shown to be successful with reduction of the amount of solvent required and possibility of automation of the cleanup procedure. The whole method was then validated according to the SANCO/12571/2013 guidelines, proving its suitability as confirmation method for the selected analytes.

Micro-solid-phase extraction (µ-SPE) of organophosphorous pesticides from wheat followed by LC-MS/MS determination

ABSTRACT A rapid, selective and effective method of extraction, clean-up and concentration of organophosphorous pesticides from wheat followed by electrospray (ESI) LC-MS/MS analysis was developed. The μ-SPE (micro-solid-phase extraction) procedure resulted in good analytical performance and reduced at the same time matrix effects, analysis time and solvent consumption. Limits of detection (LODs) and quantification (LOQs) were in the range of 0.3–10 and 1–30 μg kg−1, respectively, with good reproducibility (RSD ≤ 13.8) and recoveries between 75% and 109%. Coefficients of determination (r2) were greater than 0.996 for the studied pesticides. Despite the reduced sorbent bed mass of μ-SPE tips (4.2 mg), the analytical data showed that no saturation phenomena occurs in the tested range of concentration both for single compounds and mixtures. Several real samples were analysed and the concentrations of the selected pesticides were found to be below the respective maximum residue limit (MRLs).

Nano carbon black-based screen printed sensor for carbofuran, isoprocarb, carbaryl and fenobucarb detection: application to grain samples

An electrochemical screening assay for the detection of phenyl carbamates (i.e. carbaryl, carbofuran, isoprocarb and fenobucarb) was developed and applied to grains samples (i.e. durum wheat, soft wheat and maize). Nano carbon black (CB) was strategically employed to realize an effective, reproducible, fouling resistant, low cost, delocalisable screen printed sensor (CB-SPE). CB-SPEs morphology (SEM and FEM) and electrochemical property (CV and EIS) were studied. The final pesticides analysis protocol consist of: (i) extraction of the analyte (just by mixing), (ii) alkaline hydrolysis (10 min R.T.), (iii) DPV detection directly of 100 µL of extract on the CB-SPE surface. Linear range between 1.0 × 10-7 and 1.0 × 10-4 mol L-1, good determination coefficients (R2 ≥ 0.9971) and satisfactory sensitivity (≥ 3.90 × 10-1 A M-1 cm-2) and LODs (≤ 8.0 × 10-8 mol L-1) were obtained for all the analytes. Excellent recoveries (78-102%) and accuracy (relative error vs. HPLC-MS/MS between 9.0% and -7.8%) resulted from the analysis of grains samples. The proposed CB-SPE based approach has demonstrated to be able to detect carbaryl at Maximum residue limits levels (MRLs), allowing class selective detection of commonly employed phenyl carbamates in food samples.

Simple and rapid silver nanoparticles based antioxidant capacity assays: Reactivity study for phenolic compounds

A single-step, rapid (10 min), sensitive silver nanoparticles (AgNPs) based spectrophotometric method for antioxidant capacity (AOC) assay has been developed. The assay is based on the ability of natural polyphenols to reduce Ag(I) and stabilize the produced AgNPs(0) at room temperature. Localized surface plasmon resonance (LSPR) of AgNPs at ≈420 nm is then measured. Using different conditions of pH (8.4) and temperature (45 °C) a further assay based on the production of AgNPs with selectivity for flavonols was also developed. The reactivity of the two AgNPs based assays vs. 15 polyphenols belonging to different chemical classes and 9 different samples has been studied and compared with ABTS, Folin and AuNPs based methods for AOC. The proposed assays had good reproducibility (RSD ≤ 13) and are simple, sensitive and cost effective. Moreover, used in conjunction with the classical AOC assays, can improve the information on the polyphenolic pool of food samples.

NADH Oxidation onto Different Carbon-Based Sensors: Effect of Structure and Surface-Oxygenated Groups

Different carbon-based materials have been compared for the development of NADH sensors: glassy carbon electrodes (GCE), multiwalled carbon nanotubes (MWCNT), and carbon black (CB). The GCE and MWCNT has been subjected to oxidative pretreatment to study the influence of oxidative groups for NADH oxidation. The materials had been characterized by FT-IR to identify the surface composition. The response of bare (GC) and GC/modified electrodes toward potassium ferricyanide have been employed to obtain information about the electroactive area and electron transfer rate. Studies of NAD+/NADH redox behavior showed that MWCNT and GCE exhibit high degree of passivation while CB shows no fouling effects. Catalytic effect of surface-oxygenated groups was also proved for GCE and MWCNT, and both, O-GCE and O-MWCNT, exhibited a lower oxidation overpotential compared to the respective untreated materials. Chronoamperometric quantification showed a linear dependence between 2–18 μmol·L−1 and a detection limits of 6.2 μmol·L−1 (GCE), 5.4 μmol·L−1 (O-GCE), 3.2 μmol·L−1 (GCE/CB), 9.6 μmol·L−1 (GCE/MWCNT), and 4.9 μmol·L−1 (GCE/O-MWCNT) were obtained. The analytical performances suggest that a careful choice of the material for NADH sensing is necessary depending on the sensor application.

Peptide Modified ZnO Nanoparticles as Gas Sensors Array for Volatile Organic Compounds (VOCs)

In this work a peptide based gas sensor array based of ZnO nanoparticles (ZnONPs) has been realized. Four different pentapeptides molecularly modeled for alcohols and esters having cysteine as a common spacer have been immobilized onto ZnONPs. ZnONPs have been morphologically and spectroscopically characterized. Modified nanoparticles have been then deposited onto quartz crystal microbalances (QCMs) and used as gas sensors with nitrogen as carrier gas. Analysis of the pure compounds modeled demonstrated a nice fitting of modeling with real data. The peptide based ZnONPs had very low sensitivity to water, compared to previously studied AuNPs peptide based gas sensors allowing the use of the array on samples with high water content. Real samples of fruit juices have been assayed; stability of the signal, good repeatability, and discrimination ability of the array was achieved.

Optical Detection of Antioxidant Capacity in Food Using Metal Nanoparticles Formation. Study on Saffron Constituents

A simple metal nanoparticles (MNPs) based colorimetric assay for the antioxidant capacity of Saffron polyphenolics is proposed. The proposed method has been compared with the commonly used classical assays (FC and ABTS); a significant similar response trend was found with the ABTS. Additionally, it was also found that the proposed approach was polyphenols selective versus other endogenous antioxidants as safranal and crocin.

Press-transferred carbon black electrodes coupled to microchip electrophoresis for food pesticides detection

In this work the assembling of novel carbon black (CB) press-transferred electrodes (CB-PTEs) is reported. The press-transferred nanomaterial based-approach presented may open new gates for electrochemical sensing since this technology does not require clean room facilities [1-2]. The electrodes have been designed to be coupled to microchip electrophoresis (ME) that gives excellent opportunities to carry out a quantitative multi-residual screening analysis characterized by rapidity, low sample and reagent consumption, and extremely low waste generation.

Development of an Optical Sensing Strategy Based on Gold Nanoparticles Formation Driven by Polyphenols. Application to Food Samples

In this work the basis for the development of two methods for evaluating the antioxidant capacity of food matrices were laid. One of the two methods involves the extraction of the phenolic fraction for the evaluation of the antioxidant capacity of polyphenols extract in aqueous solvent, while the other does not include a sample pre-treatment thus allowing an extraction free evaluation of the antioxidant capacity directly in the matrix. Both methods exploit the synthesis of gold nanoparticles (AuNPs), which present a diameter of a few tens of nm, via the reduction of chloroauric acid driven by the phenolic compounds. For the spectrophotometric reading, the absorption band of localized surface plasmon resonance (LSPR) that have produced AuNPs at 540 nm is used as analytical signal.