Santiago Marco

Publications (126) View all

• Source

  Available from: Víctor Pomareda

  Article: A Novel Differential Mobility Analyzer as VOCs detector and multivariate techniques for identification and quantification

  Victor Pomareda, Silvia López-Vidal, Daniel Calvo, Antonio Pardo, Santiago Marco
  [show abstract] [hide abstract]
  ABSTRACT: A Differential Mobility Analyser (DMA) is a specific configuration of an Ion Mobility Spectrometer (IMS) where ions with different electrical mobilities are separated in space, instead of in time of drift, as in classical drift-time IMS. This work presents an instrument developed by the company Ioner, a parallel plate DMA instrument, but with crucial differences in the sheath flow and detection system when compared to other instruments in the market. These differences improve the resolving powers and sensitivities of the instrument. Additionally, datasets from IMS or DMA instruments are typically processed with univariate techniques when only qualitative detection is of interest. However, good performance in quantitative measurements can be achieved using multivariate data processing. This work presents for the first time, measurements with a stand alone DMA instrument and the multivariate data processing related for VOCs and environmental interesting samples.
  Analyst. 04/2013;
• Article: Comparison of the performance of three ion mobility spectrometers for measurement of biogenic amines.

  Zeev Karpas, Ana V Guamán, Antonio Pardo, Santiago Marco
  [show abstract] [hide abstract]
  ABSTRACT: The performance of three different types of ion mobility spectrometer (IMS) devices: GDA2 with a radioactive ion source (Airsense, Germany), UV-IMS with a photo-ionization source (G.A.S. Germany) and VG-Test with a corona discharge source (3QBD, Israel) was studied. The gas-phase ion chemistry in the IMS devices affected the species formed and their measured reduced mobility values. The sensitivity and limit of detection for trimethylamine (TMA), putrescine and cadaverine were compared by continuous monitoring of a stream of air with a given concentration of the analyte and by measurement of headspace vapors of TMA in a sealed vial. Preprocessing of the mobility spectra and the effectiveness of multivariate curve resolution techniques (MCR-LASSO) improved the accuracy of the measurements by correcting baseline effects and adjusting for variations in drift time as well as enhancing the signal to noise ratio and deconvolution of the complex data matrix to their pure components. The limit of detection for measurement of the biogenic amines by the three IMS devices was between 0.1 and 1.2ppm (for TMA with the VG-Test and GDA, respectively) and between 0.2 and 0.7ppm for putrescine and cadaverine with all three devices. Considering the uncertainty in the LOD determination there is almost no statistically significant difference between the three devices although they differ in their operating temperature, ionization method, drift tube design and dopant chemistry. This finding may have general implications on the achievable performance of classic IMS devices.
  Analytica chimica acta 01/2013; 758:122-9. · 4.31 Impact Factor
• Source

  Available from: Víctor Pomareda

  Article: Multivariate Curve Resolution of nonlinear Ion Mobility Spectra followed by Multivariate Nonlinear Calibration for Quantitative Prediction

  Víctor Pomareda, Ana Verónica Guamán, Masoumeh Mohammadnejad, Daniel Calvo, Antonio Pardo, Santiago Marco
  [show abstract] [hide abstract]
  ABSTRACT: In this work, a new methodology to analyze spectra time-series obtained from ion mobility spectrometry (IMS) has been investigated. The proposed method combines the advantages of multivariate curve resolution-alternating least squares (MCR-ALS) for an optimal physical and chemical interpretation of the system (qualitative information) and a multivariate calibration technique such as polynomial partial least squares (poly-PLS) for an improved quantification (quantitative information) of new samples. Ten different concentrations of 2-butanone and ethanol were generated using a volatile generator based on permeation tubes. The different concentrations were measured with IMS. These data present a non-linear behavior as substance concentration increases. Although MCR-ALS is based on a bilinear decomposition, non-linear behavior can be modeled by adding new components to the model. After spectral pre-processing, MCR-ALS was applied aiming to get information about the ionic species that appear in the drift tube and their evolution with the analyte concentration. By resolving the IMS data matrix, concentration profiles and pure spectra of the different ionic species have been obtained for both analytes. Finally, poly-PLS was used in order to build a calibration model using concentration profiles obtained from MCR-ALS for ethanol and 2-butanone. The results, with more than 99% of explained variance for both substances, show the feasibility of using MCR-ALS to resolve IMS datasets. Furthermore, similar or better prediction accuracy is achieved when concentration profiles from MCR-ALS are used to build a calibration model (using poly-PLS) compared to other standard univariate and multivariate calibration methodologies.
  Chemometrics and Intelligent Laboratory Systems 06/2012; 118:219. · 1.92 Impact Factor
• Article: The potential of ion mobility spectrometry (IMS) for detection of 2,4,6-trichloroanisole (2,4,6-TCA) in wine.

  Zeev Karpas, Ana V Guamán, Daniel Calvo, Antonio Pardo, Santiago Marco
  [show abstract] [hide abstract]
  ABSTRACT: The off-flavor of "tainted wine" is attributed mainly to the presence of 2,4,6-trichloroanisole (2,4,6-TCA) in the wine. In the present study the atmospheric pressure gas-phase ion chemistry, pertaining to ion mobility spectrometry, of 2,4,6-trichloroanisole was investigated. In positive ion mode the dominant species is a monomer ion with a lower intensity dimer species with reduced mobility values (K(0)) of 1.58 and 1.20 cm(2)V(-1) s(-1), respectively. In negative mode the ion with K(0) =1.64 cm(2)V(-1)s(-1) is ascribed to a trichlorophenoxide species while the ions with K(0) =1.48 and 1.13 cm(2)V(-1)s(-1) are attributed to chloride attachment adducts of a TCA monomer and dimer, respectively. The limit of detection of the system for 2,4,6-TCA dissolved in dichloromethane deposited on a filter paper was 2.1 μg and 1.7 ppm in the gas phase. In ethanol and in wine the limit of detection is higher implying that pre-concentration and pre-separation are required before IMS can be used to monitor the level of TCA in wine.
  Talanta 05/2012; 93:200-5. · 3.79 Impact Factor
• Article: Cluster analysis of rat olfactory bulb responses to diverse odorants.

  Matteo Falasconi, Agustin Gutierrez-Galvez, Michael Leon, Brett A Johnson, Santiago Marco
  [show abstract] [hide abstract]
  ABSTRACT: In an effort to deepen our understanding of mammalian olfactory coding, we have used an objective method to analyze a large set of odorant-evoked activity maps collected systematically across the rat olfactory bulb to determine whether such an approach could identify specific glomerular regions that are activated by related odorants. To that end, we combined fuzzy c-means clustering methods with a novel validity approach based on cluster stability to evaluate the significance of the fuzzy partitions on a data set of glomerular layer responses to a large diverse group of odorants. Our results confirm the existence of glomerular response clusters to similar odorants. They further indicate a partial hierarchical chemotopic organization wherein larger glomerular regions can be subdivided into smaller areas that are rather specific in their responses to particular functional groups of odorants. These clusters bear many similarities to, as well as some differences from, response domains previously proposed for the glomerular layer of the bulb. These data also provide additional support for the concept of an identity code in the mammalian olfactory system.
  Chemical Senses 03/2012; 37(7):639-53. · 2.60 Impact Factor