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Quality control of natural gas frequently relies on off-line slow standardized chromatographic techniques. Previous implementations of new measurement approaches focused of synthetic mixtures without extensive industrial validation. Here, a fast alternative based on infrared spectra is presented to predict the gas constituents and a physical parameter, the Wobbe index. Commercial samples instead of synthetic mixtures were used to develop predictive models. Method performance parameters were calculated and ca. 100 % of the sample-specific confidence intervals for the predictions overlapped with those of the reference values and the approach was unbiased and precise. The limits of detection and quantification (classical and considering errors of type I and II) outperformed other approaches. Validation included commercial samples and primary mixtures. Furthermore, prediction models considering reduced sets of variables were sought for using Markov-chain Monte Carlo guided searches (uninformative variable elimination and random frog) and common (iPLS, UVE and SR) approaches. The prediction errors and limits of detection of these ‘reduced’ models outperformed those from other approaches. The methodology takes only minutes to analyse a sample, requires few sample and no reagents (only some argon), making this approach cost-effective and environmentally-friendly.
Borja Ferreiro; José Andrade; Purificación López-Mahía; Soledad Muniategui; Cristina Vázquez; Andrés Pérez; María Rey; Carlos Vales. Fast quality control of natural gas for commercial supply and transport utilities. Fuel 2021, 305, 121500 .
AMA StyleBorja Ferreiro, José Andrade, Purificación López-Mahía, Soledad Muniategui, Cristina Vázquez, Andrés Pérez, María Rey, Carlos Vales. Fast quality control of natural gas for commercial supply and transport utilities. Fuel. 2021; 305 ():121500.
Chicago/Turabian StyleBorja Ferreiro; José Andrade; Purificación López-Mahía; Soledad Muniategui; Cristina Vázquez; Andrés Pérez; María Rey; Carlos Vales. 2021. "Fast quality control of natural gas for commercial supply and transport utilities." Fuel 305, no. : 121500.
The EU goal to reduce marine plastic litter by ca. 30% by 2020 stressed the need to deploy analytical methods to ascertain the polymeric nature of a residue. Furthermore, as plastics age under natural conditions and usual databases do not include their weathered spectra, (micro)plastics in environmental samples may be unidentified. In this paper, polyamide (nylon) microplastics weathering was monitored because of its ubiquity in household commodities, clothes, fishery items and industry, whose residues end up frequently in the environment. Infrared spectra (ATR and microreflectance) and Scanning Electron Microscopy (SEM) images were collected periodically while exposing nylon to controlled weathering. It was seen that ATR was more sensitive than microreflectance to monitor the structural evolution of polyamide and that the spectra and the surface of weathered microplastics showed remarkable differences with the pristine material, which stresses the need for considering its evolution when identifying microplastics in environmental studies. The evolution of six band ratios related to the chemical evolution of this polymer are presented. SEM images revealed the formation of secondary microplastics at the most advanced weathering stages of polyamide.
Verónica Fernández-González; Jose Manuel Andrade; Borja Ferreiro; Purificación López-Mahía; Soledad Muniategui-Lorenzo. Monitorization of polyamide microplastics weathering using attenuated total reflectance and microreflectance infrared spectrometry. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2021, 263, 120162 .
AMA StyleVerónica Fernández-González, Jose Manuel Andrade, Borja Ferreiro, Purificación López-Mahía, Soledad Muniategui-Lorenzo. Monitorization of polyamide microplastics weathering using attenuated total reflectance and microreflectance infrared spectrometry. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2021; 263 ():120162.
Chicago/Turabian StyleVerónica Fernández-González; Jose Manuel Andrade; Borja Ferreiro; Purificación López-Mahía; Soledad Muniategui-Lorenzo. 2021. "Monitorization of polyamide microplastics weathering using attenuated total reflectance and microreflectance infrared spectrometry." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 263, no. : 120162.
To assess the knocking properties of natural gas (NG) when it is used as fuel for vehicles is vital to optimize the design and functioning of their motors. Analytical efforts in this field are needed as the engines used to define it empirically are not available anymore, and existent mathematical algorithms yield different accuracy. The hybridization of gas-phase infrared spectrometry and partial least squares multivariate regression is presented first time to address the determination of the methane number (MN) of NG samples. It circumvents the need for the previous knowledge of the NG composition required to apply dedicated equations. The use of true NG samples to develop the models is also quite new in the field. Proof-of-concept studies were made with synthetic spectra and, then, a collection of liquefied NG samples for which MN values were computed by the National Physics Laboratory algorithm (NPL) from their sample composition were used to develop operative models. Additional validation was made with a collection of synthetic standard mixtures prepared for two European projects (EMRP LNG II and EMPIR LNG III) whose service methane numbers (SMN) were measured with an engine. The FTIR-PLS approach yielded statistically unbiased predictions with average standard errors around 0.4% MN when compared to the NPL-MN and SMN values, and standard deviations of the means ca. 1% MN. The approach is fast, cost effective as it involves standard instrumentation, and can be considered compliant with the green chemistry principles.
Santiago Ponte; Jose Manuel Andrade; Cristina Vázquez; Borja Ferreiro; Carlos Cobas; Andrés Pérez; María Rey; Carlos Vales; Jose Pellitero; Blanca Santacruz; Soledad Muniategui; Purificación López-Mahía; Bo Shu; Helga Bettin; Daniela Klaus; Bert Anders; Marius Betz; Ulf Kühne; Christian Meier; Peter Eilts. Modeling the natural gas knocking behaviour using gas-phase infrared spectra and multivariate calibration. Journal of Natural Gas Science and Engineering 2021, 90, 103944 .
AMA StyleSantiago Ponte, Jose Manuel Andrade, Cristina Vázquez, Borja Ferreiro, Carlos Cobas, Andrés Pérez, María Rey, Carlos Vales, Jose Pellitero, Blanca Santacruz, Soledad Muniategui, Purificación López-Mahía, Bo Shu, Helga Bettin, Daniela Klaus, Bert Anders, Marius Betz, Ulf Kühne, Christian Meier, Peter Eilts. Modeling the natural gas knocking behaviour using gas-phase infrared spectra and multivariate calibration. Journal of Natural Gas Science and Engineering. 2021; 90 ():103944.
Chicago/Turabian StyleSantiago Ponte; Jose Manuel Andrade; Cristina Vázquez; Borja Ferreiro; Carlos Cobas; Andrés Pérez; María Rey; Carlos Vales; Jose Pellitero; Blanca Santacruz; Soledad Muniategui; Purificación López-Mahía; Bo Shu; Helga Bettin; Daniela Klaus; Bert Anders; Marius Betz; Ulf Kühne; Christian Meier; Peter Eilts. 2021. "Modeling the natural gas knocking behaviour using gas-phase infrared spectra and multivariate calibration." Journal of Natural Gas Science and Engineering 90, no. : 103944.
Mexican Tequila is one of the most demanded import spirits in Europe. Its fast-raising worldwide request makes counterfeiting a profitable activity affecting both consumers and legal distillers. In this paper, a sensor-based methodology based on a combination of infrared measurements (IR) and multivariate data analysis (MVA) is presented. The case study is about differentiating two categories of white Tequila: pure Tequila (or ‘100% agave’) and mixed Tequila (or simply, Tequila). The IR spectra were treated and fused with a low-level approach. Exploratory data analysis was performed using PCA and partial least squares (PLS), whilst the authentication analyses were carried out with PLS-discriminant analysis (DA) and soft independent modeling for class analogy (SIMCA) models. Results demonstrated that data fusion of IR spectra enhanced the outcomes of the authentication models capable of differentiating pure from mixed Tequilas. In fact, PLS-DA presented the best results which correctly classified all fifteen commercial validation samples. The methodology thus presented is fast, cheap, and of simple application in the Tequila industry.
Christian Pérez-Beltrán; Víctor Zúñiga-Arroyo; José Andrade; Luis Cuadros-Rodríguez; Guadalupe Pérez-Caballero; Ana Jiménez-Carvelo. A Sensor-Based Methodology to Differentiate Pure and Mixed White Tequilas Based on Fused Infrared Spectra and Multivariate Data Treatment. Chemosensors 2021, 9, 47 .
AMA StyleChristian Pérez-Beltrán, Víctor Zúñiga-Arroyo, José Andrade, Luis Cuadros-Rodríguez, Guadalupe Pérez-Caballero, Ana Jiménez-Carvelo. A Sensor-Based Methodology to Differentiate Pure and Mixed White Tequilas Based on Fused Infrared Spectra and Multivariate Data Treatment. Chemosensors. 2021; 9 (3):47.
Chicago/Turabian StyleChristian Pérez-Beltrán; Víctor Zúñiga-Arroyo; José Andrade; Luis Cuadros-Rodríguez; Guadalupe Pérez-Caballero; Ana Jiménez-Carvelo. 2021. "A Sensor-Based Methodology to Differentiate Pure and Mixed White Tequilas Based on Fused Infrared Spectra and Multivariate Data Treatment." Chemosensors 9, no. 3: 47.
Infrared spectrometry (IR) became a workhorse to characterize microplastics (MPs) worldwide. However, reports on the experimental conditions to measure them decreased alarmingly. As complete, relevant information on the instrumental setup determining IR spectra is crucial for scientific reproducibility, ca. 50% of the papers that reported FTIR to measure MPs were evaluated and it was found that most studies cannot be replicated due to missing experimental details. To ameliorate this, the most critical parameters influencing IR spectra are depicted, their impact when matching a spectrum against databases exemplified, and, following efforts from other scientific fields, a minimum information for publication of IR-related data on MPs characterization (MIPIR-MP) is proposed, along with a brief, simple paragraph to resume the most critical information to be reported. This can be used to improve the worrying figures that point out to a reproducibility crisis in the field, as disclosed by the survey.
Jose M. Andrade; Borja Ferreiro; Purificación López-Mahía; Soledad Muniategui. Standardization of the minimum information for publication of infrared-related data when microplastics are characterized. Marine Pollution Bulletin 2020, 154, 111035 .
AMA StyleJose M. Andrade, Borja Ferreiro, Purificación López-Mahía, Soledad Muniategui. Standardization of the minimum information for publication of infrared-related data when microplastics are characterized. Marine Pollution Bulletin. 2020; 154 ():111035.
Chicago/Turabian StyleJose M. Andrade; Borja Ferreiro; Purificación López-Mahía; Soledad Muniategui. 2020. "Standardization of the minimum information for publication of infrared-related data when microplastics are characterized." Marine Pollution Bulletin 154, no. : 111035.
Society concerns about the potential thread of microplastics into the environment call for detailed laboratory and field studies to assess their fate, in particular, their weathering. This can hardly be done in natural conditions and, so, a low-cost system (
J. Andrade; V. Fernández-González; P. López-Mahía; S. Muniategui. A low-cost system to simulate environmental microplastic weathering. Marine Pollution Bulletin 2019, 149, 110663 .
AMA StyleJ. Andrade, V. Fernández-González, P. López-Mahía, S. Muniategui. A low-cost system to simulate environmental microplastic weathering. Marine Pollution Bulletin. 2019; 149 ():110663.
Chicago/Turabian StyleJ. Andrade; V. Fernández-González; P. López-Mahía; S. Muniategui. 2019. "A low-cost system to simulate environmental microplastic weathering." Marine Pollution Bulletin 149, no. : 110663.
European trends to get greener cities and to protect the environment imply substituting traditional diesel/gasoline engines for gas (gas-hybrid) powered engines. To accomplish this, straightforward quality control of liquefied and/or compressed natural gas is needed. This communication shows that the broadening effect of an auxiliary inert gas (Ar) enhances their infrared (IR) gaseous spectra and improves usual analytical performance parameters by 50%, which paves the way to use IR routinely to assess the composition of natural gas samples.
Borja Ferreiro; Jose M. Andrade; Carlota Paz-Quintáns; Purificación López-Mahia; Soledad Muniategui; Maria Rey-Garrote; Cristina Vázquez-Padín; Carlos Vales. Improved Sensitivity of Natural Gas Infrared Measurements Using a Filling Gas. Energy & Fuels 2019, 33, 6929 -6933.
AMA StyleBorja Ferreiro, Jose M. Andrade, Carlota Paz-Quintáns, Purificación López-Mahia, Soledad Muniategui, Maria Rey-Garrote, Cristina Vázquez-Padín, Carlos Vales. Improved Sensitivity of Natural Gas Infrared Measurements Using a Filling Gas. Energy & Fuels. 2019; 33 (8):6929-6933.
Chicago/Turabian StyleBorja Ferreiro; Jose M. Andrade; Carlota Paz-Quintáns; Purificación López-Mahia; Soledad Muniategui; Maria Rey-Garrote; Cristina Vázquez-Padín; Carlos Vales. 2019. "Improved Sensitivity of Natural Gas Infrared Measurements Using a Filling Gas." Energy & Fuels 33, no. 8: 6929-6933.
A fast (16min) procedure to assess the bioaccessible metallic fraction of Cd, Cr, Cu, Ni, Pb and Zn simultaneously extracted (SEM) from marine sediments plus an indirect approach to determine acid volatile sulfides (AVS) are presented. For the extraction process magnetic agitation was compared with ultrasonic stirring (using a bath and a probe), and several stirring times were assayed. The proposed SEM procedure uses an ultrasonic probe and 1mL of HCl. It dramatically minimizes the turnaround time and the residues. AVS were evaluated as the difference between the amounts of sulphur in the solid residue after the extraction and total sulphur in the original sample. These procedures are fast, easy to implement and cost-effective to assess the potential risk posed by metals in marine sediments. They were tested using several CRMs and applied to sediments from two Galician Rias (NW Spain); their SEM-AVS differences indicated no biological risk.
J. Terán-Baamonde; Alatzne Carlosena; R.M. Soto-Ferreiro; J.M. Andrade; D. Prada. Fast assessment of bioaccessible metallic contamination in marine sediments. Marine Pollution Bulletin 2017, 125, 310 -317.
AMA StyleJ. Terán-Baamonde, Alatzne Carlosena, R.M. Soto-Ferreiro, J.M. Andrade, D. Prada. Fast assessment of bioaccessible metallic contamination in marine sediments. Marine Pollution Bulletin. 2017; 125 (1):310-317.
Chicago/Turabian StyleJ. Terán-Baamonde; Alatzne Carlosena; R.M. Soto-Ferreiro; J.M. Andrade; D. Prada. 2017. "Fast assessment of bioaccessible metallic contamination in marine sediments." Marine Pollution Bulletin 125, no. 1: 310-317.
Discriminant partial least squares (PLS-DA)—a de facto standard classification method—was found to behave poorly when 3 classes of tequilas were modeled to study a collection of 170 commercial Mexican spirits measured by UV-Vis spectroscopy. This result was compared with other linear and nonlinear supervised classification methods (PLS with variable selection by SRI index and genetic algorithms; kernel-PLS—modified in this paper to handle simultaneously several classes, quadratic discriminant analysis (QDA), support vectors machines, and counter-propagation artificial neural networks). All linear models performed worse than nonlinear ones, and this was attributed to the quite different inner dispersion of the classes and the intermediate position of 1 class. Considering the overall classification results and parsimony, QDA was selected for routine assessments thanks to its simplicity and broad availability.
Jose Manuel Andrade; Davide Ballabio; Maria Paz Gómez-Carracedo; Guadalupe Perez-Caballero. Nonlinear classification of commercial Mexican tequilas. Journal of Chemometrics 2017, 31, e2939 .
AMA StyleJose Manuel Andrade, Davide Ballabio, Maria Paz Gómez-Carracedo, Guadalupe Perez-Caballero. Nonlinear classification of commercial Mexican tequilas. Journal of Chemometrics. 2017; 31 (12):e2939.
Chicago/Turabian StyleJose Manuel Andrade; Davide Ballabio; Maria Paz Gómez-Carracedo; Guadalupe Perez-Caballero. 2017. "Nonlinear classification of commercial Mexican tequilas." Journal of Chemometrics 31, no. 12: e2939.
G. Pérez-Caballero; J.M. Andrade; P. Olmos; Y. Molina; I. Jiménez; J.J. Durán; Carlos Fernandez-Lozano; F. Miguel-Cruz. Authentication of tequilas using pattern recognition and supervised classification. TrAC Trends in Analytical Chemistry 2017, 94, 117 -129.
AMA StyleG. Pérez-Caballero, J.M. Andrade, P. Olmos, Y. Molina, I. Jiménez, J.J. Durán, Carlos Fernandez-Lozano, F. Miguel-Cruz. Authentication of tequilas using pattern recognition and supervised classification. TrAC Trends in Analytical Chemistry. 2017; 94 ():117-129.
Chicago/Turabian StyleG. Pérez-Caballero; J.M. Andrade; P. Olmos; Y. Molina; I. Jiménez; J.J. Durán; Carlos Fernandez-Lozano; F. Miguel-Cruz. 2017. "Authentication of tequilas using pattern recognition and supervised classification." TrAC Trends in Analytical Chemistry 94, no. : 117-129.
Oil spill identification relies usually on a wealth of chromatographic data which requires advanced data treatment (chemometrics). A simple approach based on Kohonen neural networks to handle three-dimensional arrays is presented. A suite of 28 diagnostic ratios was considered to monitor six oils along four months. It was found that some traditional diagnostic ratios were not stable enough. In particular, alkylated PAHs (e.g. 1-methyldibenzothiophene, 4-methylpyrene, 27bbSTER and the TA21 and TA26 triaromatic steroids) seemed less resistant to medium-weathering than biomarkers. One (or two) ratios were found to differentiate each product: 30O, 28ab (and 25nor30ab), C3-dbt/C3-phe, 27Ts, TA26 and 29Ts characterized Ashtart, Brent, Maya, Sahara, IFO and Prestige oils, respectively.
R. Fernández-Varela; M.P. Gómez-Carracedo; Davide Ballabio; J.M. Andrade. The use of diagnostic ratios, biomarkers and 3-way Kohonen neural networks to monitor the temporal evolution of oil spills. Marine Pollution Bulletin 2015, 96, 313 -320.
AMA StyleR. Fernández-Varela, M.P. Gómez-Carracedo, Davide Ballabio, J.M. Andrade. The use of diagnostic ratios, biomarkers and 3-way Kohonen neural networks to monitor the temporal evolution of oil spills. Marine Pollution Bulletin. 2015; 96 (1-2):313-320.
Chicago/Turabian StyleR. Fernández-Varela; M.P. Gómez-Carracedo; Davide Ballabio; J.M. Andrade. 2015. "The use of diagnostic ratios, biomarkers and 3-way Kohonen neural networks to monitor the temporal evolution of oil spills." Marine Pollution Bulletin 96, no. 1-2: 313-320.
This work studies airborne quality in a geographical area that has not been investigated broadly: a suburban site nearby A Coruña (Galicia, NW Iberian Peninsula). In contrast to major Spanish cities, the site has Atlantic characteristics: rainy, scarce calm weather and infrequent prolonged sunny periods. The relationships between several gaseous pollutants (NO, NO2, NOx, CO, O3, PM10, PM2.5 and PM1) and their temporal trends (daily, monthly and seasonal) were evaluated. The aim was to unravel whether medium- and long-distance sources were impacting upon the site. Univariate studies focused on factorizing the pollutants according to a codifying factor (wind direction, hour of the day, season and month). Multivariate studies (Varimax-rotated factorial analysis) were done separately on both weekdays and weekends. The intensity of the daily maxima for NO, NO2, NOx and CO was lower during the weekends, with O3 behaving opposite. PM average values agreed with previous historical reports for a rural background station relatively close to the site and they decreased daily between 11:00 and 19:00 h, likely because of the marine breeze. With moderate wind speeds the pollutants were associated to medium-distance pollution sources, mainly the city of A Coruña and a combination of industrial pollution sources (a power plant, a solid waste incinerator and a regional airport).
M.P. Gómez-Carracedo; J.M. Andrade; Davide Ballabio; D. Prada-Rodríguez; S. Muniategui-Lorenzo; Viviana Consonni; M. Piñeiro-Iglesias; P. López-Mahía. Impact of medium-distance pollution sources in a Galician suburban site (NW Iberian peninsula). Science of The Total Environment 2015, 512-513, 114 -124.
AMA StyleM.P. Gómez-Carracedo, J.M. Andrade, Davide Ballabio, D. Prada-Rodríguez, S. Muniategui-Lorenzo, Viviana Consonni, M. Piñeiro-Iglesias, P. López-Mahía. Impact of medium-distance pollution sources in a Galician suburban site (NW Iberian peninsula). Science of The Total Environment. 2015; 512-513 ():114-124.
Chicago/Turabian StyleM.P. Gómez-Carracedo; J.M. Andrade; Davide Ballabio; D. Prada-Rodríguez; S. Muniategui-Lorenzo; Viviana Consonni; M. Piñeiro-Iglesias; P. López-Mahía. 2015. "Impact of medium-distance pollution sources in a Galician suburban site (NW Iberian peninsula)." Science of The Total Environment 512-513, no. : 114-124.
A fast, simple and straightforward procedure to decide on the best model to calculate the mass discrimination factor in Isotope Dilution Inductively Coupled Plasma Mass Spectrometry (ID-ICP-MS) is proposed.
Javier Terán Baamonde; J. M. Andrade; Rosa-María Soto-Ferreiro; Alatzne Carlosena; Dario Prada-Rodríguez. A simple procedure to select a model for mass discrimination correction in isotope dilution inductively coupled plasma mass spectrometry. Journal of Analytical Atomic Spectrometry 2015, 30, 1197 -1206.
AMA StyleJavier Terán Baamonde, J. M. Andrade, Rosa-María Soto-Ferreiro, Alatzne Carlosena, Dario Prada-Rodríguez. A simple procedure to select a model for mass discrimination correction in isotope dilution inductively coupled plasma mass spectrometry. Journal of Analytical Atomic Spectrometry. 2015; 30 (5):1197-1206.
Chicago/Turabian StyleJavier Terán Baamonde; J. M. Andrade; Rosa-María Soto-Ferreiro; Alatzne Carlosena; Dario Prada-Rodríguez. 2015. "A simple procedure to select a model for mass discrimination correction in isotope dilution inductively coupled plasma mass spectrometry." Journal of Analytical Atomic Spectrometry 30, no. 5: 1197-1206.
Comparing the slopes of two regression lines is an almost daily task in analytical laboratories. The usual procedure is based on a Student's t-test although literature differs in whether the standard errors of the slopes or the standard errors of the regressions should be employed to get a pooled standard error. In this work fundamental concepts on the use of the Student's test were reviewed and Monte Carlo simulations were done to ascertain whether relevant differences arise when the two options are considered. It was concluded that for small sample sets (as it is usual in analytical laboratories) the Student's t-test based on the standard error of regression models must be used and special attention must be paid on the equality of the models variances. Finally, alternative approaches were reviewed, with emphasis on a simple one based on the analysis of the covariance (ANCOVA).
J.M. Andrade; M.G. Estévez-Pérez. Statistical comparison of the slopes of two regression lines: A tutorial. Analytica Chimica Acta 2014, 838, 1 -12.
AMA StyleJ.M. Andrade, M.G. Estévez-Pérez. Statistical comparison of the slopes of two regression lines: A tutorial. Analytica Chimica Acta. 2014; 838 ():1-12.
Chicago/Turabian StyleJ.M. Andrade; M.G. Estévez-Pérez. 2014. "Statistical comparison of the slopes of two regression lines: A tutorial." Analytica Chimica Acta 838, no. : 1-12.
M.P. Gómez-Carracedo; J.M. Andrade; P. López-Mahía; S. Muniategui; D. Prada. A practical comparison of single and multiple imputation methods to handle complex missing data in air quality datasets. Chemometrics and Intelligent Laboratory Systems 2014, 134, 23 -33.
AMA StyleM.P. Gómez-Carracedo, J.M. Andrade, P. López-Mahía, S. Muniategui, D. Prada. A practical comparison of single and multiple imputation methods to handle complex missing data in air quality datasets. Chemometrics and Intelligent Laboratory Systems. 2014; 134 ():23-33.
Chicago/Turabian StyleM.P. Gómez-Carracedo; J.M. Andrade; P. López-Mahía; S. Muniategui; D. Prada. 2014. "A practical comparison of single and multiple imputation methods to handle complex missing data in air quality datasets." Chemometrics and Intelligent Laboratory Systems 134, no. : 23-33.
Self‐organizing maps (SOMs) (in particular, Matrix reOrganization Layout to Map Analytical Patterns (MOLMAP)) were used to unravel the main patterns in a three‐way dataset after a preliminary unfolding of the cube. Eleven sites of the ría of Vigo (NW of Spain) were monitored during the last decade (from 2000 to 2010) to assess pollution trends in this area. Twelve trace metals (Hg, Pb, Cd, Cu, Zn, Cr, As, Li, Fe, Al, Ni and Mn), the total organic carbon and the percentage of fine particles were measured. Results from MOLMAP, the SOM‐based approach, were compared to those of three established alternatives: parallel factor analysis, matrix‐augmented principal component analysis and generalized Procrustes rotation, the latter two employing unfolding as well. MOLMAP showed the best capabilities to differentiate groups of samples. The spatial and temporal trends, as well as the analytical variables causing them, were almost the same for all methods, which confirms MOLMAP as a simple and reliable methodology to treat three‐way environmental datasets. Copyright © 2014 John Wiley & Sons, Ltd.
Victoria Besada; Cristina Quelle; José Manuel Andrade; Noemí Gutiérrez; Fernando Schultze; María Paz Gómez-Carracedo. A 10-year survey of trace metals in sediments using self-organizing maps. Journal of Chemometrics 2014, 28, 558 -566.
AMA StyleVictoria Besada, Cristina Quelle, José Manuel Andrade, Noemí Gutiérrez, Fernando Schultze, María Paz Gómez-Carracedo. A 10-year survey of trace metals in sediments using self-organizing maps. Journal of Chemometrics. 2014; 28 (7):558-566.
Chicago/Turabian StyleVictoria Besada; Cristina Quelle; José Manuel Andrade; Noemí Gutiérrez; Fernando Schultze; María Paz Gómez-Carracedo. 2014. "A 10-year survey of trace metals in sediments using self-organizing maps." Journal of Chemometrics 28, no. 7: 558-566.
T. Caramés-Alfaya; M.P. Gómez-Carracedo; J.M. Andrade. Fast and cheap screening of oil spillages by thermogravimetry and pattern recognition. Microchemical Journal 2013, 110, 379 -385.
AMA StyleT. Caramés-Alfaya, M.P. Gómez-Carracedo, J.M. Andrade. Fast and cheap screening of oil spillages by thermogravimetry and pattern recognition. Microchemical Journal. 2013; 110 ():379-385.
Chicago/Turabian StyleT. Caramés-Alfaya; M.P. Gómez-Carracedo; J.M. Andrade. 2013. "Fast and cheap screening of oil spillages by thermogravimetry and pattern recognition." Microchemical Journal 110, no. : 379-385.
S. Carballo; J. Teran; R.M. Soto; Alatzne Carlosena; J.M. Andrade; D. Prada; Rosa-María Soto-Ferreiro. Green approaches to determine metals in lubricating oils by electrothermal atomic absorption spectrometry (ETAAS). Microchemical Journal 2013, 108, 74 -80.
AMA StyleS. Carballo, J. Teran, R.M. Soto, Alatzne Carlosena, J.M. Andrade, D. Prada, Rosa-María Soto-Ferreiro. Green approaches to determine metals in lubricating oils by electrothermal atomic absorption spectrometry (ETAAS). Microchemical Journal. 2013; 108 ():74-80.
Chicago/Turabian StyleS. Carballo; J. Teran; R.M. Soto; Alatzne Carlosena; J.M. Andrade; D. Prada; Rosa-María Soto-Ferreiro. 2013. "Green approaches to determine metals in lubricating oils by electrothermal atomic absorption spectrometry (ETAAS)." Microchemical Journal 108, no. : 74-80.
The standard additions method (SAM) has traditionally been performed by using extrapolation. This practice is suboptimal because predictions are affected by even slight departures of calibration points from a straight line. Despite this, most textbooks and papers in analytical chemistry still refer exclusively to extrapolation. In contrast, the use of interpolation is recommended in this paper as a way to get predictions on the central part of the regression line and thus minimize the bias in the prediction and the variance associated with the analytical result. Several scenarios were studied, with concentration errors simulated in different calibration solutions. It was found that translational effects due to variations at the central part of the calibration caused the lowest disturbances on the predicted concentrations. The differences between the interpolated and extrapolated predictions can be as large as ±30%. The confidence interval associated with the extrapolation result is wider than that due to interpolation by as much as 100%. It is shown that commonly used equations underestimate the correct confidence intervals. Both, absence of bias and improved precision, are of relevance in quality assurance, method validation and error propagation.
J.M. Andrade; J. Terán-Baamonde; R.M. Soto-Ferreiro; A. Carlosena. Interpolation in the standard additions method. Analytica Chimica Acta 2013, 780, 13 -19.
AMA StyleJ.M. Andrade, J. Terán-Baamonde, R.M. Soto-Ferreiro, A. Carlosena. Interpolation in the standard additions method. Analytica Chimica Acta. 2013; 780 ():13-19.
Chicago/Turabian StyleJ.M. Andrade; J. Terán-Baamonde; R.M. Soto-Ferreiro; A. Carlosena. 2013. "Interpolation in the standard additions method." Analytica Chimica Acta 780, no. : 13-19.
The quantification of metals in lubricating oils is relevant to trace machinery wearing and to evaluate potential environmental effects related to their disposal. Electrothermal atomic absorption spectrometry (ETAAS) is a common choice to measure metal content and despite efforts being made to reduce the amount of organic materials in the measurement aliquot (e.g., using emulsions), potential interferents still remain there. Therefore, quantification of the analyte is a highly difficult task. In this work a general-purpose methodology based on multivariate partial least squares regression (PLS) is presented to address interferences when difficult organic materials are analysed by ETAAS. It is shown that such a methodology yields powerful quantification models and requires less staff dedication, shorter turnaround times and lower expenses than traditional approaches. Besides, it is totally compatible with green analytical chemistry principles. Further, figures of merit which consider the risk of false negatives and false positives were calculated following the latest ISO and European guidelines: critical level (decision limit), minimum detectable value (detection capability), trueness and precision, multivariate sensitivity and sample-specific confidence interval. They have not been used in the atomic spectrometry field. The case study is about quantifying Cu in lubricating oils as a tracer of machine weathering.
J. M. Andrade; S. Carballo-Paradelo; Javier Terán Baamonde; Alatzne Carlosena; Rosa-María Soto-Ferreiro; D. Prada-Rodríguez. Multivariate calibration to implement green ETAAS methods when analysing Cu in lubricating oils. Analytical Methods 2013, 5, 4039 -4046.
AMA StyleJ. M. Andrade, S. Carballo-Paradelo, Javier Terán Baamonde, Alatzne Carlosena, Rosa-María Soto-Ferreiro, D. Prada-Rodríguez. Multivariate calibration to implement green ETAAS methods when analysing Cu in lubricating oils. Analytical Methods. 2013; 5 (16):4039-4046.
Chicago/Turabian StyleJ. M. Andrade; S. Carballo-Paradelo; Javier Terán Baamonde; Alatzne Carlosena; Rosa-María Soto-Ferreiro; D. Prada-Rodríguez. 2013. "Multivariate calibration to implement green ETAAS methods when analysing Cu in lubricating oils." Analytical Methods 5, no. 16: 4039-4046.