521 research outputs found
Validation of Nuclear Magnetic Resonance Experiments Used in Food Certification
No full textNonostante i vantaggi derivanti dall'utilizzo della risonanza magnetica nucleare e nono-stante la pletora di processi di validazione ben documentati (precisione, accuratezza, li-nearità, riproducibilità, robustezza, selettività e specificità), pochissimi metodi ufficiali ba-sati su questa tecnica sono noti. Con l'obiettivo di estendere l'uso dell’ NMR nei metodi ufficiali, è stato organizzato il primo confronto interlaboratorio (ILC) internazionale per il fingerprinting del grano e della farina, secondo la normativa ISO/IEC 17043:2010 e altri ri-ferimenti normativi in vigore. ILC fornisce standard oggettivi per laboratori individuali, permettere loro di confrontare i risultati analitici provenienti da diversi laboratori e rappre-senta un modo per controllare la qualità e la precisione del lavoro analitico. La validazione mediante ILC è il punto di partenza per il riconoscimento ufficiale di metodi analitici. 39 NMR data set sono stati prodotti da 37 partecipanti, provenienti da tutto il mondo, con un totale di 46 spettrometri. Al fine di rendere il metodo NMR ufficialmente riconosciuto, i da-ti NMR devono essere elaborati statisticamente secondo le normative europee di riferi-mento. Le prestazioni di ogni laboratorio sono state valutate mediante z-score, parametro relativo alla deviazione standard. I laboratori con uno z-score all’ interno del range di ac-cettabilità sono in grado di garantire prestazioni soddisfacenti. I risultati indicano che l'e-sperimento NMR (1H 1D NOESY) proposto in questo ILC è robusto. Infatti, la maggior parte degli spettri NMR prodotti nel confronto può essere considerata "statisticamente equivalente". Dal momento che nessun precedente rapporto è disponibile per una valuta-zione comparativa dei risultati, in questa fase è opportuno mettere in evidenza alcune possibili criticità, tenendo conto dei valori% CV raccolti in questo ILC. Il passo successi-vo in questa direzione è stata la validazione della procedura di elaborazione degli spettri. Tutti gli spettri ottenuti da questo ILC sono stati elaborati mediante software Mnova con 2 modi differenti di calcolo e con Top Spin, ancora una volta.Despite the advantages deriving from the use of NMR and despite the plethora of well documented validation processes (e.g., precision, accuracy, linearity, reproducibility, ro-bustness, selectivity, and specificity), very few official NMR based quantification meth-ods are known. With the aim to extend the use of NMR in official methods, NMR inter-laboratory comparison (ILC) for fingerprinting of on wheat and flour, was organized ac-cording to ISO/IEC 17043:2010 and reference normative therein. ILC provide objective standards for individual laboratories, permit them to compare analytical results from dif-ferent laboratories and represent a way to check the quality and the accuracy of the ana-lytical job. Validation by ILCs is the starting point for official recognition of the analytical methods. The aim of this inter-laboratory comparison was the validation of a fingerprinting NMR method for classification of wheat and flours. 39 NMR data sets were produced by 37 participants, from all over the world, using 46 spectrometer. In order to make a NMR method officially recognized, NMR data should be statistically processed according to European reference normative. The performance of each laboratory was assessed by means of a z-score which is related to the standard deviation. Laboratories endowed with z-score falling within the suitable acceptability range are able to guarantee a satisfactory performance. Results indicate that the NMR experiment (1D 1H NOESY) proposed for the fingerprinting of wheat and flour aqueous extracts is a robust experiment. In fact, the ma-jority of the participants produced NMR spectra that can be considered “statistically equivalent”. Thus, the main goal of this inter-laboratory comparison, the validation of the 1D 1H NOESY experiment, was achieved along with the indication of the participants able to produce NMR spectra with the highest possible performances. Since no previous report is available for a comparative evaluation of the results, at this stage it is advisable to highlight some possible critical points taking into account the CV% values collected in this ILC. The ulterior step in this direction was the validation of spectra processing proce-dures. All spectra obtained from this ILC were processed with Mnova Software with 2 dif-ferent ways of calculation and with Top Spin once again
Must fermentation progress monitoring by polymer coated capacitive vapour sensor arrays
No full textThe present work deals with the task of monitoring the fermentation progress of grape must with a gas sensor array, without the use of pre-concentrator steps. The sensor array consists of eighrt interdigitated capacitors, coated with different polymeric materials through a well, formatted around the capacitor. The fermentation process of a particular must was duplicated under laboratory conditions and monitored in terms of (a) standard chemical analysis and (b) the response of the sensor array to the headspace of must samples, on a daily basis. PCA analysis revealed that a successful fermentation follows a distinct curve not related to that obtained from a series of equivalent pure ethanol solutions ©2009 IEEE
Electrolyte-gated organic transistors for biosensing applications
No full textThe interfacing of biomaterials to electronic devices is one of the most challenging research fields that has relevance to both fundamental studies and the development of highly performing biosensors. Important aspects connected to the field of biosensors based on electrolyte-gated organic transistors are discussed. The main features of biomolecules used as recognition elements along with the strategies reported so far for their deposition on the biosensors transducer surface are presented. An introduction of the involving surface interactions such as covalent binding, physical adsorption, self-assembly and bio-affinity binding strategy is given. Besides, the most relevant surface materials for electronic biosensors development are analysed. In the last part, different electronic biosensors based on electrolyte-gated organic transistors are presented. Particular attention is paid to the biosensors operation mechanism and to the analytical figure of merits. Specific applications such as DNA and proteins detection are also discussed
Expression and tissue-specific localization of nitrate-responsive miRNAs in roots of maize seedlings
No full textAbstract
Nitrogen availability seriously affects crops productivity and environment. The knowledge of post-transcriptional regulation of plant response to nutrients is important to improve nitrogen use efficiency of crop. This research was aimed at understanding the role of miRNAs in the molecular control of plant response to nitrate.
A maize miRNAs-microarray platform was used to discover previously unknown nitrate-responsive miRNAs. Six mature miRNA were identified and their expression profiles were deeply studied by qPCR and in situ hybridization (ISH). To this aim a novel optimized protocol was set up for the use of DIG labelled ZNA (Zip Nucleic Acid)-modified oligonucleotides as probes for ISH. Significant differences in miRNAs’ transcripts accumulation were evidenced between nitrate-supplied and nitrate-depleted roots. Real time PCR analyses and in situ detection of miRNA, confirmed the arrays data and allowed us to evidence distinct miRNAs spatio-temporal expression patterns in maize roots. Our results suggest that a prolonged nitrate depletion may induce post-transcriptionally the expression of target genes by repressing the transcription of specific miRNAs. In particular, the repression of the transcription of miR528a/b, miR528a*/b*, miR169i/j/k, miR169i*/j*/k*, miR166j/k/n and miR408/b upon nitrate shortage could represent a crucial step integrating nitrate signals into developmental changes in maize roots
Characterization of polymer layers for silicon micromachined bilayer chemical sensors using white light interferometry
No full textThe swelling behavior of polymer layers used in silicon micromachined bilayer structures is studied using white light interferometry. The study focuses on poly-hydroxy-ethyl-methacrylate (PHEMA) films and their behavior in terms of film expansion, response time and sensitivity upon exposure to methanol and ethanol vapors. Thin films of PHEMA exhibit higher relative swelling than thicker films, in the presence of methanol, as well as lower diffusion coefficients corresponding to higher response times. © 2005 Published by Elsevier B.V
Polymer/BaTiO3 nanocomposites based chemocapacitive sensors
No full textThe performance of novel capacitive sensors, based on PHEMA-BaTiO3 composite films, is presented. The changes in capacitance response upon exposure to various levels of humidity and ethanol vapor are studied in order to evaluate the effect of incorporated BaTiO3 on the sensitivity-selectivity of the sensors. © 2008 Elsevier B.V. All rights reserved
Comparison between different architectures of an electrolyte-gated organic thin-film transistor fabricated on flexible Kapton substrates
No full textEvaluation of a chemocapacitive sensor array for the detection of vapor analytes and their mixtures
No full textElectrical and optical evaluation of polymer composites for chemical sensing applications
No full textIn this work we focus on poly(hydroxy ethyl methacrylate)/carbon black composites for the electrical and optical sensing of humidity and alcohols. The sensitivity is a non-monotonous function of carbon load, while processing with and without ultrasonic agitation can lead to substantially different sensitivity levels. In the case of a carbon-loaded film, optical sensing is limited by the transparency of the carbon-loaded film, which, nevertheless, can be manipulated within limits through the choice of casting solvent. Electrical sensitivity of the composites is compared to the optical (thickness-based) and capacitance sensitivities of the carbon-free poly(hydroxy ethyl methacrylate) version. Composites offer a clear sensitivity advantage when their optimized, on the basis or electrical response, version is employed. © 2008 Elsevier B.V. All rights reserved
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