Bernardo Moreno Cordero - Academia.edu (original) (raw)

Papers by Bernardo Moreno Cordero

The Analyst, 1989

... Jose Luis Perez Pavon, Bernard0 Moreno Cordero,&quot; Jesus Hernandez Mendez and Jorg... more ... Jose Luis Perez Pavon, Bernard0 Moreno Cordero,&quot; Jesus Hernandez Mendez and Jorge Cerda Miralles Department of Analytical Chemistry, Bromatolog y and Food Sciences, Faculty of ... M (0.15 g of Triton X-100 plus 1 mg of PAN); V,, 143 pi: and pH, 9.2 (HBO;, + NaBO?) 3 ...

Analytical Chemistry, 1994

In chromatographic analysis of polycyclic aromatic hydrocarbons (PAH), three important aspects mu... more In chromatographic analysis of polycyclic aromatic hydrocarbons (PAH), three important aspects must be taken into account: losses by sorption onto the containers, association with dissolved organic material, and the need for high preconcentration factors. In this work, fluorescence detection was used for liquid chromatographic analysis of polycyclic aromatic hydrocarbons after cloud point preconcentration with the nonionic surfactant Triton X-114. Negligible sorption of PAH onto the containers and high recoveries, even in the presence of considerable levels of humic acids, are additional advantages of the proposed micelle-mediated methodology. Bottled and river water samples afforded almost complete recoveries when the procedure described was applied. Furthermore, micellar solutions of Triton X-114 effectively extracted PAH from solid samples.

Analytical Chemistry, 1989

reduction to I&on gold in 0.1 M TBAP in dry acetonitrile. The UV-visible absorption spectrum of I... more reduction to I&on gold in 0.1 M TBAP in dry acetonitrile. The UV-visible absorption spectrum of IA'was not observed with the 560-pm cell, but was observed with the 160-pm cell. When stationary IA solution was reduced in the 100-Mm cell, the 1A'-spectrum grew to a maximum over 10 s and disappeared over a t o t a l period of 35 s. Decreasing the cell thickness (I) from 560 to 160 pm produced a 12-fold decrease in the time taken (t) to achieve exhaustive electrolysis for electroactive species with similar diffusion coefficients (D). This agrees with the approximate relation t a 12/D The compound under observation must have a molar extinction coefficient above a certain limit, with the minimum requirements being c > 200 M-' cm-' for the 560-pm cell and e > 600 M-' cm-' for the 160-rm cell. The flow operation of this system permits cleaning and O2 removal so that the cell need not be removed from the spectrometer between experiments on different solutions. Thus the cell has an application for photoelectrochemical detection in high-performance liquid chromatography and for flow injection analysis (10, 11). To conclude, we have shown that a well controlled spectroelectrochemical system may be constructed without instrument workshop facilities, thus making the technique much more widely available. ACKNOWLEDGMENT We thank D. Bethel1 for providing samples of l-bromo

Analytica Chimica Acta, 2002

Cloud point methodology has been successfully used for the preconcentration of trace amounts of C... more Cloud point methodology has been successfully used for the preconcentration of trace amounts of Cd and Pb as a prior step to their determination by flame atomic absorption spectrometry. O,O-Diethyldithiophosphate and Triton X-114 are used as hydrophobic ligand and non-ionic surfactant, respectively. After phase separation at 40°C based on cloud point of the mixture, the surfactant-rich phase is diluted with methanol. The enriched analyte in the final solution is determined by flame atomic absorption spectrometry using conventional nebulization. After optimization of the complexation and extraction conditions, enhancement factors of 22 and 43 were obtained for Cd and Pb, respectively. Under the experimental conditions used, preconcentration of only 10ml of sample in the presence of 0.05% (v/v) Triton X-114 permitted the detection of 0.62μgl−1 of Cd and 2.86μgl−1of Pb. The proposed method was applied to the determination of Cd and Pb in human hair samples.

Talanta, 2017

Profile signals of urine samples corresponding to patients with lung cancer and controls were obt... more Profile signals of urine samples corresponding to patients with lung cancer and controls were obtained using a non-separative methodology. The method is based on the coupling of a headspace sampler, a programed temperature vaporizer and a mass spectrometer (HS-PTV-MS). With only a centrifugation step as prior sample treatment, the samples were subjected to the headspace generation process and the volatiles generated were introduced into the PTV where they were trapped in the Tenax® packed liner while the solvent was purged. Finally, the analytes were introduced directly, without separation, into the mass spectrometer which allows obtaining the fingerprint of the analyzed sample. The mass spectrum corresponding to the mass/charge ratios (m/z) ranging between 35 and 120amu (amu) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization of the samples. Samples of 14 patients with some type of cancer and 24 healthy...

Journal of chromatography. A, Jan 29, 2016

A novel methodology for the determination of ornithine, putrescine, cadaverine, spermidine and ga... more A novel methodology for the determination of ornithine, putrescine, cadaverine, spermidine and gamma-amino butyric acid in urine samples has been developed. The method uses in situ aqueous derivatization followed by automated microextraction by packed sorbent coupled to a gas chromatography-mass spectrometry system equipped with a programmed temperature vaporizer. This instrumental configuration minimizes sample manipulation due to from the mixing of the reagents, the process is completely automated. The analytes were derivatized using ethyl chloroformate as derivatization reagent. The reaction occurred in aqueous medium and was carried out in 1min in the vial of an autosampler used to perform microextraction by packed sorbent. The parameters affecting derivatization, extraction and separation were optimized in order to obtain maximum sensitivity. Calibration curves were obtained for five calibration levels in three different matrices. All the calibration models displayed good linea...

Journal of Chromatography A, 2014

A methodology for the determination of five aldehydes in urine has been developed based on the co... more A methodology for the determination of five aldehydes in urine has been developed based on the coupling of a headspace generation sampler with a gas chromatography-mass spectrometry system equipped with a programmed temperature vaporizer. This instrumental configuration minimizes sample manipulation and allows the determination of these compounds without the need for a derivatization step so that the methodology is largely shortened and simplified. An experimental design was carried out in order to optimize the headspace sampling. Sample matrix effect was eliminated by means of dilution of urine samples. The calibration models displayed good linearity (0.1-10 g/L) and their validity was checked using ANOVA, and it was observed that they did not exhibit any lack of fit. The LODs obtained ranged between 0.04 and 0.08 g/L and the LOQs between 0.12 and 0.24 g/L. The accuracy of the method was evaluated in terms of apparent recoveries which were between 86 and 120%. The method developed was applied to the analysis of 17 samples of urine from different subjects in order to quantify these endogenous compounds.

TrAC Trends in Analytical Chemistry, 2006

The question of the temporal stability of the signal is still important in the case of MS-based s... more The question of the temporal stability of the signal is still important in the case of MS-based systems, although the problem is less pronounced than with conventional electronic noses. We compare and contrast four strategies to correct signal drift: internal normalization; internal ...

Talanta, 2007

A high-speed determination of naphthalene and total methylnaphthalenes using a non-separative met... more A high-speed determination of naphthalene and total methylnaphthalenes using a non-separative method based on direct injection into the mass spectrometer was performed. The results obtained for total methylnaphthalenes were very similar to those provided with fast gas chromatography-mass spectrometry (GC-MS). However, the non-separative method afforded higher concentrations in the determination of naphthalene than those found when fast GC-MS was used. We propose a correction that removes this error very satisfactorily and allows the same results to be obtained with both methodologies. The non-separative method is rapid, simple and-in view of the results-highly suitable for the determination of naphthalene and total methylnaphthalenes in gasoline samples.

Journal of Separation Science, 2014

The present research focuses on the evaluation of different ionic liquid (IL) stationary phases i... more The present research focuses on the evaluation of different ionic liquid (IL) stationary phases in gas chromatography. The different IL columns were evaluated in terms of peak resolution (Rs) and peak symmetry for the separation of the chlorobenzenes. The determination of chlorobenzenes in soil samples by means of the optimal IL stationary phase (SLB-IL82) is proposed as an application. Soil pretreatment was based on a simplified quick, easy, cheap, effective, rugged, and safe extraction procedure and a large injection volume via a programed temperature vaporizer working in solvent vent mode. The retention time of the chlorobenzenes increased as the polarity of the IL column decreased. SLB-IL82 is the stationary phase that provides the best values as regards Rs and asymmetry factor. Soil sample blanks were spiked with the analytes before subjecting the sample to the extraction process. The existence of a matrix effect was checked and the analytical characteristics of the method were determined in a fortified garden soil sample. The method provided good linearity, good repeatability and reproducibility values, and the LODs were in the 0.1-4.7 μg/kg range. Two fortified soil samples were applied to validate the proposed methodology.

Journal of Separation Science, 2001

Comparative study of silicone and microporous membranes for the separation of some phenols prior ... more Comparative study of silicone and microporous membranes for the separation of some phenols prior to high performance liquid chromatography analysis A membrane separation module has been coupled on-line to a high-resolution liquid chromatographic system. A microcomputer controls the set of operations required in the overall automatic process. Two types of membranes, homogeneous (silicone) and microporous with air-filled pores, have been investigated and the results obtained for five chlorophenols, of different polarities and volatilities, have been compared. The most important variables affecting the process are the composition of the donor and acceptor phases and the enrichment time. The method using the silicone membrane, was applied to the determination of the analytes in real water samples.

Journal of Chromatography A, 2000

The potential of the cloud point methodology for the preconcentration of relatively polar compoun... more The potential of the cloud point methodology for the preconcentration of relatively polar compounds was studied using the non-ionic surfactant Triton X-114 and five EPA chlorophenols as test analytes. Analyte determination was performed using reversed-phase gradient LC with electrochemical and spectrophotometric detection. The amount of surfactant used is a critical variable in the preconcentration factor because it determines the extraction yield and the volume of surfactant-rich phase obtained. These values were determined as a function of the Triton X-114 concentration, together with the phase ratio, which allows prediction of the maximum preconcentration factor under given conditions.

Journal of Chromatography A, 2010

A method based on QuEChERS extraction is proposed for the determination of trihalomethanes (chlor... more A method based on QuEChERS extraction is proposed for the determination of trihalomethanes (chloroform, bromodichloromethane, dibromocloromethane and bromoform) in soil samples. The new version of QuEChERS adapted to soil samples consists of liquid extraction with ethyl acetate, the addition of water to moisten the samples, salting-out partitioning of the water with anhydrous MgSO4, and direct injection of the organic extract, obtained after the centrifugation step, into the gas chromatograph. This simplified extraction procedure maintains the advantages of the original method and avoids some steps, making the final procedure simpler, faster, and cheaper, with the consequent reduction in errors associated with sample manipulation. The experimental conditions of the analytical method, based on fast gas chromatography (FGC) and micro-electron capture detection (microECD), were optimized. The column and oven program used allowed fast separation of the compounds in less than 4 min and the total analysis cycle time was as short as 10 min. The existence of a matrix effect was checked and the analytical conditions of the method were studied in a fortified garden soil sample. The highly sensitive and selective detector used afforded to detection limits in the order of ng/kg for the target compounds. To validate the proposed method two certified reference materials (CRMs) were analyzed.

Journal of Chromatography A, 2008

A sensitive method is presented for the fast analysis of three aromatic and six polycyclic aromat... more A sensitive method is presented for the fast analysis of three aromatic and six polycyclic aromatic hydrocarbons (biphenyl, 3-methylbiphenyl, 4-methylbiphenyl, fluorene, phenanthrene, fluoranthene, pyrene, 1,2-benz(a)anthracene and chrysene) in gasoline samples. The applicability of a GC device equipped with a programmable temperature vaporizer (PTV) and an MS detector is explored. Additionally, a modular accelerated column heater (MACH TM) was used to control the temperature of the capillary gas chromatography column. This module can be heated and cooled very rapidly, making total analysis cycle times very short. The proposed method does not require any previous analyte extraction and preconcentration step, as in most methods described to date. Sample preparation is reduced to simply diluting the gasoline samples in methanol. This reduces the experimental errors associated with this step of the analytical process. By using sampling injection in the solvent vent mode, and through choice of a suitable temperature, the lightest major components of the gasoline were removed. Moreover, use of a liner packed with Tenax-TA allowed the compounds of interest to be retained during the process. This working strategy could be extended to other groups of compounds through the choice of different venting temperatures. In this way, a large part of the gasoline components are eliminated, the life of the liner is prolonged, and it is possible to inject sample volumes that will not saturate the chromatographic column. The limits of detection ranged from 0.61 g/L (pyrene) to 6.1 g/L (biphenyl), and precision (measured as the relative standard deviation) was equal to or lower than 7.3%. The method was applied to the determination of analytes in gasoline samples and the results obtained can be considered highly satisfactory.

Journal of Chromatography A, 1998

On-line coupling of devices for nonchromatographic separation to chromatographic analysis systems... more On-line coupling of devices for nonchromatographic separation to chromatographic analysis systems affords a substantial improvement in sample processing and facilitates the automation of the procedure, considerably decreasing the error of the analytical methods used. In this work, a silicone membrane device has been coupled to a high-performance liquid chromatograph with electrochemical and ultraviolet detection and the system has been used to determine phenols in complex organic matrices (gasolines and kerosene) with minimum sample handling. A microcomputer controls the set of operations required in the overall automatic process. Several quantification methods, internal standard, calibration in phenol-free matrices and standard addition, have been used, all of them providing similar results.

Journal of Chromatography A, 2006

The coupling of a headspace sampler to a fast gas chromatography system with mass spectrometry de... more The coupling of a headspace sampler to a fast gas chromatography system with mass spectrometry detection is proposed as a method for the identification of the sources of contamination in soils due to the presence of hydrocarbons derived from petroleum. The samples are subjected to the headspace generation process, with no prior treatment, and the volatiles generated are separated by fast gas chromatography. The total time of the chromatogram per sample is less than six minutes. Chemometric treatments, such as hierarchical cluster analysis (HCA), principal component analysis (PCA), and soft independent modelling of class analogy (SIMCA) were applied to the signals obtained for the different samples. The variables used for the chemometric treatments include m/z ratios characteristic of linear and branched saturated hydrocarbons, alkyl cyclohexanes, benzene, toluene, xylenes, C3-benzenes, naphthalene and methyl-naphthalenes. The results obtained show clear differentiated clusters for the different crude oils and correct predictions when SIMCA is applied, thus allowing the differentiation of types of crude oils contaminating soils in a rapid and reliable manner.

Journal of Chromatography A, 2011

A method using headspace generation and in situ derivatization with water soluble EDC (1-[3-(dime... more A method using headspace generation and in situ derivatization with water soluble EDC (1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide) and TFEA (2,2,2-trifluoroethylamine) has been optimized for the determination of ibuprofen (2-(p-isobutylphenyl)propionic acid), one of the most common nonsteroid anti-inflammatory drug (NSAIDs) residues in surface and wastewater samples. Derivatization was carried out in the vial of the headspace sampler (HS) in only 15 min, after which instrumental measurements were made with gas chromatography-mass spectrometry (GC-MS). As the injection system, a programmed temperature vaporizer (PTV) in the solvent-vent injection mode is proposed in order to increase the sensitivity of the measurements. The effects of the variables affecting HS generation, the derivatization reaction, and the instrumental PTV conditions were studied. A limit of quantification as low as 32 ng/L was achieved, and repeatability values were below 10%. Accuracy of the method was evaluated using spiked ultrapure water at three concentration levels, obtaining apparent recoveries between 96% and 104%. The proposed method was applied to the quantification of ibuprofen in sea water and urban wastewater samples.

Journal of Chromatography A, 2002

In the present work, we propose the use of direct coupling of a headspace sampler to a mass spect... more In the present work, we propose the use of direct coupling of a headspace sampler to a mass spectrometer for the detection of adulterants in olive oil. Samples of olive oils were mixed with different proportions of sunflower oil and olive-pomace oil, respectively, and patterns of the volatile compounds in the original and mixed samples were generated. Application of the linear discriminant analysis technique to the data from the signals was sufficient to differentiate the adulterated from the non-adulterated oils and to discriminate the type of adulteration. The results obtained revealed 100% success in classification and close to 100% in prediction. The main advantages of the proposed methodology are the speed of analysis (since no prior sample preparation steps are required), low cost, and the simplicity of the measuring process.

Laboratory Automation & Information Management, 1999

An overview about the analytical applications of membrane-based systems is presented. The differe... more An overview about the analytical applications of membrane-based systems is presented. The different types of Ž. membranes microporous, homogenous, ion-exchange and asymmetric and the main forces related to the transport through Ž. them differences in concentration, pressure or electrical potential are briefly discussed.