[Show abstract][Hide abstract] ABSTRACT: Since it was proposed for the first time, desorption electrospray ionization-mass spectrometry (DESI-MS) has been evaluated for applicability in numerous areas. Elucidations of the ionization mechanisms and the subsequent formation of isolated gas-phase ions have been proposed so far. In this context, the role of both surface and pneumatic effects on ion-formation yield has recently been investigated. Nevertheless, the effect of the surface chemistry has not yet been completely understood. Functionalized glass surfaces have been prepared, in order to tailor surface performance for ion formation. Three substrates were functionalized by depositing three different silanes [3-mercaptopropyltriethoxysilane (MTES), octyltriethoxysilane (OTES), and 1H,1H,2H,2H-perfluorooctyltriethoxy-silane (FOTES)] from toluene solution onto standard glass slides. Surface characterization was carried out by contact-angle measurements, tapping-mode atomic force microscopy, and X-ray photoelectron spectroscopy. Morphologically homogeneous and thickness-controlled films in the nm range were obtained, with surface free energies lying between 15 and 70 mJ/m2. These results are discussed, together with those of DESI-MS on low-molecular-weight compounds such as melamine, tetracycline, and lincomycin, also taking into account the effects of the sprayer potential and its correlation with surface wettability. The results demonstrate that ion-formation efficiency is affected by surface wettability, and this was demonstrated operating above and below the onset of the electrospray.
Journal of the American Society for Mass Spectrometry 04/2015; 26(8). DOI:10.1007/s13361-015-1135-9 · 3.19 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new amperometric immunosensor based on the covalent immobilization of tissue transglutaminase enzyme in its open conformation (open-tTG) was developed and optimized for determination of anti-tissue transglutaminase antibodies (anti-tTG) in human serum. Experimental design allowed us to find the optimal conditions for quantification of both IgA and IgG isotypes of anti-tTG in order to assess suitability of the device for diagnostic purposes.
The glassy carbon electrodic substrate was electrochemically functionalized with gold nanoparticles and subsequently derivatized with a self-assembled monolayer of 11-mercaptoundecanoic acid for the covalent anchoring of the enzyme. This step was performed under carefully controlled conditions in order to keep the open conformation of the tTG.
The immunosensor showed good analytical performance with limit of detection levels (1.7 AU mL−1 for IgA and 2.7 AU mL−1 for IgG) below the diagnostic threshold value (3.0 AU mL−1) and inter-sensor reproducibility giving RSD lower than 10%. The developed sensor was validated in serum samples from pediatric patients for clinical applications, using two ELISA kits specific for the determination of anti-tTG IgA and IgG antibodies as reference methods; good recovery rates ranging from 74% to 117% were calculated.
[Show abstract][Hide abstract] ABSTRACT: A selective cavitand-based solid-phase microextraction coating was synthesized for the determination of nitroaromatic explosives and explosive taggants at trace levels in air and soil. A quinoxaline cavitand functionalized with a carboxylic group at the upper rim was used to enhance selectivity towards analytes containing nitro groups. The fibers were characterized in terms of film thickness, morphology, thermal stability and pH resistance. An average coating thickness of 50 (±4) µm, a thermal stability until 400°C and an excellent fiber-to-fiber and batch to batch repeatability with RSD lower than 4% were obtained. The capabilities of the developed coating for the selective sampling of nitroaromatic explosives were proved achieving LOD values in the low ppbv and ng kg-1 range, respectively for air and soil samples.
[Show abstract][Hide abstract] ABSTRACT: Home-made micro-solid-phase extraction (SPE) cartridges using different adsorbent materials were tested for the desorption electrospray ionization–high-resolution mass spectrometry (DESI-HRMS) determination of explosives like 2,4,6-trinitrotoluene, cyclotrimethylene-trinitramine, cyclotetramethylene-tetranitramine, pentaerythritol tetranitrate, and trinitrophenylmethylnitramine in soil samples. Quantitation limits in the low nanogram per kilogram range proved the reliability of the method for the detection of explosives at ultra-trace levels. The reduced sample preparation allowed for low costs and high-throughput analyses. Finally, the superior extraction capability of the method was proved by obtaining DESI-HRMS responses at least five times higher than those achieved by performing DESI-HRMS analyses of solid–liquid extracts spotted onto commercial polytetrafluoroethylene slides.
DESI-HRMS analysis of explosives from soil samples
[Show abstract][Hide abstract] ABSTRACT: A piezoelectric immunosensor was developed for the first time for direct detection of anti-tissue transglutaminase antibodies (anti-tTG), very specific biomarkers for reliable and early diagnosis of celiac disease. Since the inflammation processes associated to the pathology's occurrence involve tTG structural changes from closed to open conformation as well the extended structure has been demonstrated to have higher diagnostic accuracy if compared with closed conformation, the new strategy undertaken in this study was based on the immobilization of tTG enzyme in its open conformation as receptor on immunosensor surface. Ten nm-sized gold nanoparticles conjugated with secondary antibodies were exploited for signal amplification. Liquid phase detection conditions using a laminar flow cell were properly selected in order to have a good signal stability both in dynamic and in static modes. Optimization of the operating conditions, by experimental design on mouse anti-tTG antibodies in serum, allowed us to obtain a model for the realization of a reliable piezoelectric immunosensor with high potential as diagnostic device for the determination of human autoantibodies of celiac patients.
Sensors and Actuators B Chemical 10/2014; 201:300–307. DOI:10.1016/j.snb.2014.05.018 · 4.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Different sample treatment protocols for the liquid chromatography–electrospray-tandem mass spectrometry (LC–ESI-MS/MS) analysis of potential residuals of ovalbumin and caseins added to red wines were developed. In particular, attention was paid to the simultaneous detection and quantitation of fining agent residues, i.e. ovalbumin, α- and β-casein, in wine samples. The different sample treatment methods were compared in terms of protein recovery. The use of denaturing agents combined with size exclusion concentration and purification allowed to obtain a reproducible (RDS < 20%) analytical protocol with good recoveries (73(±2) – 109(±4)% range) for digested proteins from 12.5 mL of wine sample. Matrix-matched calibration from LC–ESI-MS/MS analysis indicated that the devised method allowed detection of target peptides in the 0.01–0.8 μg/mL range. Finally, method applicability and selectivity was demonstrated by using fining agents commonly exploited in winery industry and by analyzing 20 commercial red wine samples.
Food Control 04/2014; 38:82–87. DOI:10.1016/j.foodcont.2013.10.015 · 2.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Wearable solid phase microextraction (SPME) devices consisting in necklaces and pins were developed for the environmental monitoring of ketamine in recreational places using ionic liquid as coating. SPME fibers obtained using both monocationic and dicationic polymeric ionic liquids were characterized in terms of morphology, film thickness, thermal stability and pH resistance. An average thickness of 30±5μm, an excellent thermal stability until 350°C and a very good fiber-to-fiber and batch-to-batch repeatability with RSD lower than 4% were some of the features of the developed coatings. A quantitation limit (LOQ) of 0.05mg/m(3) with a sampling time of 1min proved the feasibility of the developed method for the quantitation of ketamine in air at low concentration levels. Finally, the capabilities of the fibers for the rapid SPME sampling of ketamine in recreational places were proved obtaining extraction efficiencies at least two-fold higher than those obtained using commercial devices and extraction recoveries ranging from 84.2±3.3% to 93.6±2.6% (n=3).
Journal of Chromatography A 01/2014; 1331. DOI:10.1016/j.chroma.2014.01.012 · 4.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new voltammetric competitive immunosensor selective for atrazine, based on the immobilization of a conjugate atrazine-bovine serum albumine on a nanostructured gold substrate previously functionalized with poliamidoaminic dendrimers, was realized, characterized, and validated in different real samples of environmental and food concern. Response of the sensor was reliable, highly selective and suitable for the detection and quantification of atrazine at trace levels in complex matrices such as territorial waters, corn-cultivated soils, corn-containing poultry and bovine feeds and corn flakes for human use. Selectivity studies were focused on desethylatrazine, the principal metabolite generated by long-term microbiological degradation of atrazine, terbutylazine-2-hydroxy and simazine as potential interferents. The response of the developed immunosensor for atrazine was explored over the 10(-2)-10(3)ngmL(-1) range. Good sensitivity was proved, as limit of detection and limit of quantitation of 1.2 and 5ngmL(-1), respectively, were estimated for atrazine. RSD values <5% over the entire explored range attested a good precision of the device.
[Show abstract][Hide abstract] ABSTRACT: European Union legislation has established that plastic food contact materials shall not release primary aromatic amines (PAAs), which are toxic compounds and suspected human carcinogens. As valid alternative to existing methods for PAA determination, which are based on spectrophotometric test or targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) approaches, in this study a LC-Orbitrap-full scan-high resolution mass spectrometry (HRMS) method was devised and validated for the determination of migration levels of 22 PAAs from food contact materials, thus exploiting the specificity of accurate mass measurement. Direct injection of the simulant (acetic acid 3%, w/v) into the LC-MS system after migration, without any pre-treatment step, makes the developed method of great value for rapid screening analysis of a large number of amines. A very fast and efficient separation (<11min) of PAAs was achieved. Detection limits in the 0.06-0.7μgkg(-1) range were calculated for 17 out of 22 of the investigated PAAs, however obtaining values within 5.3μgkg(-1) for the other 5 amines. Good dynamic linear ranges from two to four orders of magnitude (r(2)≥0.990) were obtained and satisfying results were achieved in terms of intra-day (RSDs<10%) and inter-day repeatability (RSDs<17%). Trueness values in the 70±1-131±5% range proved reliability of the developed method for PAAs quantification also at very low concentration levels. Finally, the method was successfully applied to a range of different real plastic multilayer food packaging materials, noticing in all cases levels below the established limits of detection.
Journal of Chromatography A 10/2013; 1320. DOI:10.1016/j.chroma.2013.10.063 · 4.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Migration of melamine into foods from melamine tableware has been object of recent Rapid Alert System for Food and Feed (RASFF) notifications. In this context, a rapid and sensitive desorption electrospray ionization-high resolution mass spectrometry (DESI-HRMS) method was developed and validated for the determination of melamine migration from plastic materials. The migration test was performed using acetic acid 3% (w/v) as food simulant. Evaluation of DESI parameters in terms of choice of support, motion profile, geometrical configuration and operating conditions coupled to the use of an orbitrap mass analyzer allowed to achieve significant improvements in terms of selectivity and accuracy obtaining detection and quantitation limits at low microgram per kilogram level. A LC-ESI-MS method was also developed for confirmatory purposes. Both methods were applied to 44 melamine tableware samples available on Italian market in order to assess their compliance with the law. Different concentration levels ranging from 0.00773±0.0006 to 3.0±0.1mg/kg were found after the third exposure to the simulant in new and used tableware with two samples out of 44 being characterized by a melamine release higher than the legal limit, i.e. 2.5mg/kg. A two tailed t-test allowed to assess the good agreement between the quantitative results obtained applying the DESI-MS method with those provided by LC-ESI-MS, thus proving reliability of DESI-HRMS as rapid technique for the study of melamine release from plastic materials.
[Show abstract][Hide abstract] ABSTRACT: Odorant binding protein (OBP) is a multi-functional scavenger for small hydrophobic molecules dissolved in the mucus lining the nasal epithelia of mammals, characterized by broad ligand binding specificity towards a large number of structurally unrelated natural and synthetic molecules of different chemical classes. Here, we demonstrate for the first time the application of OBP as the active element of an innovative filtering matrix for the removal of environmental pollutants such as triazine herbicides from water samples. The filtering device, obtained by coupling histidine-tagged bovine OBP to a nickel nitrilotriacetic acid (Ni-NTA) agarose resin, was characterized in terms of retention capacity for the herbicides atrazine, simazine, and propazine. Analysis of these herbicides at trace levels with solid-phase microextraction followed by gas chromatography-mass spectrometry using the selected ion monitoring mode proved the capabilities of the proposed device for the decontamination of surface and groundwater samples in the 0.2-2,300 μg/L concentration range, obtaining a reduction in the triazine content greater than 97 %, thus suggesting its possible use for the potabilization of water.
[Show abstract][Hide abstract] ABSTRACT: Enhanced sensitivity for the simultaneous determination of five nut allergens in biscuit and in dark chocolate complex matrices was obtained by introduction of a rapid size-exclusion solid-phase extraction-based step before liquid chromatography–electrospray ionization-tandem mass spectrometry (LC-ESI-MS2) analysis. A very fast and efficient separation (<12 min) of marker peptides with selected reaction monitoring detection was obtained. Limits of detection in the 0.1–1.3 mg nut/kg and 5–15 mg nut/kg ranges for biscuit and dark chocolate samples as well as high recoveries (84(±6)–106(±4)% for biscuits and 98(±5)–108(±6)% for dark chocolate) proved the excellent capabilities of the exploited sample treatment method combined with the LC-MS2 analysis. Good precision in terms of intra- and inter-day repeatability was calculated, being always lower than 19 % (n = 75). Linearity was demonstrated up to four and three orders of magnitude for biscuit and dark chocolate, respectively. Finally, the validated method was successfully applied to the investigation of hidden nut trace allergens in commercially available biscuits and chocolates of different brands aiming to ascertain possible discrepancies between allergen content and food allergen labelling.
[Show abstract][Hide abstract] ABSTRACT: A new amperometric immunosensor for 2,4,6-trinitrotoluene based on the working principle of competitive enzyme-linked immunosorbent assay was developed and characterised. An electrodeposited nanogold substrate was functionalised by deposition of self-assembled monolayers of 2-aminoethanethiol as linkers for the subsequent immobilisation of polyamidoaminic dendrimers. Our approach makes use of those dendrimers to anchor a trinitrobenzene-ovalbumin conjugate on the electrode surface. The immunosensor was tested and validated for the determination of 2,4,6-trinitrotoluene showing high selectivity with respect to other nitroaromatic compounds, a limit of detection of 4.8 ng/mL and a limit of quantitation of 6 ng/mL. The immunosensor was tested for the quantification of the analyte in spiked soils and in a real sample of post-blast soil, evidencing a good recovery rate (113 %).
[Show abstract][Hide abstract] ABSTRACT: Allergy to lupin is a growing food safety problem because this legume, increasingly exploited in the food industry, is one of the allergens that, according to law, must be declared on the labels of food products in the European Union. In this context, a rapid targeted proteomic approach based on liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis was proposed and aimed to unequivocal confirmation and reliable determination of the major lupin allergens, i.e., conglutins, in pasta and biscuits. Detected concentrations were around 1 mg of lupin/kg of pasta and biscuits, proving the capabilities of the MS-based method in terms of the sensitive allergen screening method. Good precision was observed in terms of both intra- and interday repeatability, with relative standard deviation (RSD) lower than 23%. Recoveries from 95 ± 10 to 118 ± 12% and from 103 ± 1 to 110 ± 12% ranges were calculated for biscuits and pasta, respectively. Finally, the applicability of the devised method was investigated by analyzing market samples containing lupin and samples that may possibly contain traces of lupin deriving from cross-contamination between products and production lines.
Journal of Agricultural and Food Chemistry 05/2012; 60(23). DOI:10.1021/jf302105r · 3.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Superparamagnetic Fe(3)O(4) diphenyl nanoparticles were prepared according to a solvothernal procedure and characterized by X-ray diffraction, infrared spectroscopy, surface area measurements, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The magnetic phases present in the nanoparticle samples were analyzed by thermomagnetic analysis and the samples' magnetic properties were studied by vibrating sample magnetometry. The resulting nanoparticles having an average diameter of 200 nm were then used as solid-phase extraction sorbent for the determination of polycyclic aromatic hydrocarbons in urine samples. Method validation proved the feasibility of the developed beads for the quantitation of the investigated analytes at trace levels obtaining lower limit of quantitation values in the ng/l range. A good precision with coefficients of variations always lower than 15% was obtained. Finally, the superior extraction performance of the synthesized nanoparticles with respect to commercially available beads was proved.
Journal of Chromatography A 03/2012; 1231:8-15. DOI:10.1016/j.chroma.2012.02.015 · 4.26 Impact Factor