José Pavón - Academia.edu (original) (raw)

Papers by José Pavón

Aldehydes and ketones are compounds of interest in environmental analysis, food analysis, and bio... more Aldehydes and ketones are compounds of interest in environmental analysis, food analysis, and bioanalysis. Gas chromatography is among the preferred choices for their determination in many different samples. Usually, a derivatization process is used before the chromatographic separation; the reagents most used for this have been extensively reviewed in the characteristics and possibilities of five derivatization reactions (2,4-dinitrophenylhydrazone, benzyloxime, pentafluorophenyl hydrazone, pentafluorobenzyloxime, and thiazolidine derivatization). In this update the focus is on the determination of aldehydes and ketones by gas chromatography–mass spectrometry with different sample treatment strategies.

Talanta, Feb 1, 2020

Amino acids have been of great interest in clinical studies since variation in their concentratio... more Amino acids have been of great interest in clinical studies since variation in their concentration may provide information about different disorders. For the first time, a non-separative method based on single quadrupole mass spectrometry (qMS) for the simultaneous semiquantitative determination of sixteen amino acids in saliva samples has been developed. The method includes derivatisation of amino acids with ethyl chloroformatepyridine-ethanol to obtain volatile products, liquid-liquid extraction (LLE) and further analysis using a programmed temperature vaporizer (PTV) coupled to qMS. This method could be applied to the analysis of a great number of saliva samples, limiting the use of separative methods only when abnormal concentrations of amino acids were found, reducing analysis time and cost. The results obtained in the determination of amino acids using the non-separative method were compared to those obtained when a separative method based on gas chromatography (GC) was used, providing values of average relative predictive error (E %) ranging between 2 and 48%. Repeatability and reproducibility were tested, obtaining relative standard deviation (RSD) values equal to or lower than 11% and 16%, respectively. Detection limits were in the range of 0.076-8.747 mg L −1 for the non-separative method.

Journal of Chromatography A, Sep 1, 2004

A high-speed quantitative analysis of methyl tert-butyl ether (MTBE) using three different method... more A high-speed quantitative analysis of methyl tert-butyl ether (MTBE) using three different methods with mass spectrometry detection has been performed. The first method is based on fast chromatography and required an analysis time of 5.23 min per sample, although a certain period (6 min) was necessary for the initial measurement conditions to be regained prior to analysing the next sample. The other two are non-separative methods and are based on direct injection and headspace generation. The analysis times were 1.5 and 3.5 min, respectively, although in the latter case an additional period of time was required to extract volatiles from the sample. The analytical characteristics of all three methods are highly satisfactory in terms of linearity, lack of fit, precision and accuracy. The methods were applied to the determination of MTBE in different gasoline samples. The non-separative methods afforded slightly higher concentrations than those found when fast chromatography was used; this is due to the presence of other minor components that contribute to the abundance of the ion at m/z 73, characteristic of MTBE. We propose a correction that removes this error very satisfactorily and allows the same results to be obtained with all three methodologies proposed.

Analytical and Bioanalytical Chemistry, Jul 17, 2017

In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate... more In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate, 2-pentanone, 4-methyl-2-pentanone, 2-hexanone, 3-heptanone, 2heptanone, 3-octanone, and 2-nonanone) have been analyzed to evaluate their different concentration levels in urine samples from lung cancer patients (n = 12) and healthy controls (n = 12). The volatile compounds were generated with a headspace autosampler and analyzed with a gas chromatograph equipped with a programmed temperature vaporizer and mass spectrometry detector (HS-PTV-GC-MS). With the aim of evaluating the aforementioned differences, a Mann-Whitney U test and box-plots were obtained. Very good discrimination between cancer and control groups was achieved for three (ethyl acetate, 3-heptanone, and 3-octanone) of the ten analytes studied. With a view to assigning samples to the group of healthy or ill individuals, the Wilcoxon signed-rank test has been used. In spite of the small number of urine samples assayed, the results may suggest that the studied compounds could be considered useful tools in order to discern samples and they could be employed as a complementary test in a diagnosis.

Talanta, 2019

Liquidliquid extraction-programmed temperature vaporizer-gas chromatography-mass spectrometry for... more Liquidliquid extraction-programmed temperature vaporizer-gas chromatography-mass spectrometry for the determination of polycyclic aromatic hydrocarbons in saliva samples. Application to the occupational exposure of firefighters, Talanta,

Talanta, Nov 1, 2016

A rapid method for the analysis of volatiles in saliva samples is proposed. The method is based o... more A rapid method for the analysis of volatiles in saliva samples is proposed. The method is based on direct coupling of three components: a headspace sampler (HS), a programmable temperature vaporizer (PTV) and a quadrupole mass spectrometer (qMS). Several applications in the biomedical field have been proposed with electronic noses based on different sensors. However, few contributions have been developed using a mass spectrometry-based electronic nose in this field up to date. Samples of 23 patients with some type of cancer and 32 healthy volunteers were analyzed with HS-PTV-MS and the profile signals obtained were subjected to pattern recognition techniques with the aim of studying the possibilities of the methodology to differentiate patients with cancer from healthy controls. An initial inspection of the contained information in the data by means of principal components analysis (PCA) revealed a complex situation were an overlapped distribution of samples in the score plot was visualized instead of two groups of separated samples. Models using K-nearest neighbors (KNN) and Soft Independent Modeling of Class Analogy (SIMCA) showed poor discrimination, specially using SIMCA where a small distance between classes was obtained and no satisfactory results in the classification of the external validation samples were achieved. Good results were obtained when Mahalanobis discriminant analysis (DA) and support vector machines (SVM) were used obtaining 2 (false positives) and 0 samples misclassified in the external validation set, respectively. No false negatives were found using these techniques.

Microchemical Journal, 2020

A sensitive method for the quantification of polycyclic aromatic hydrocarbons (PAHs) in saliva sa... more A sensitive method for the quantification of polycyclic aromatic hydrocarbons (PAHs) in saliva samples is proposed. The method is based on the use of microextraction by packed sorbents (MEPS), injection with programmed temperature vaporizer (PTV), gas chromatography (GC) and mass spectrometry with a single quadrupole (MS). As far as we know, the MEPS technique has not been used to date for the analysis of PAHs in saliva samples. Sample treatment carried out only involves centrifugation and filtration of the saliva sample, which is subjected to the MEPS process without dilution. Standard addition was used as a calibration strategy, due to the matrix effect found using ultrapure water and among the different saliva samples. Nine saliva samples were analysed and phenanthrene was found (15 ± 6 ng L −1) in one of them. To confirm the accuracy of the method, the concentrations added in the standard additions were compared with the value predicted by the calibration model. The values ranged between 78 and 123%. The limits of detection (LOD) found in the saliva samples ranged between 4.6 and 79 ng L −1 and the repeatability and reproducibility were always equal to or lower than 10 and 17%, respectively. The main advantage of the proposed methodology over the existing ones is the complete automation of the analysis process (extraction, separation and detection). Once the saliva sample is placed in the vial, the entire process occurs on-line.

Social Science Research Network, 2022

Journal of Chromatography B, Oct 1, 2019

Here we show the determination of different polyamines (putrescine, cadaverine, spermidine) and r... more Here we show the determination of different polyamines (putrescine, cadaverine, spermidine) and related compounds (gamma-aminobutyric acid and L-ornithine) in saliva samples. These compounds are known to be biomarkers for several diseases. We have optimised an in situ derivatization process using ethyl chloroformate, an automated microextraction by packed sorbent and the determination of the corresponding products using a programmed temperature vaporizer coupled to a gas chromatograph-mass spectrometer. After finding that saliva matrix has an effect on the analysis, quantitation was performed using the one-point standard additions method and normalization to IS. This allows the detection of the analytes in the range of µg/L within a matrix obtained by a non-invasive procedure. The method has been successfully validated and it has been used in the determination of these compounds in six saliva samples finding that putrescine and cadaverine present the highest concentrations in the subject diagnosed with rheumatoid arthritis. For ornithine and spermidine, the highest concentrations were found for male subjects, especially heavy smokers. All concentrations found for the compounds were in good agreement with data found in bibliography.

Journal of Chromatography B, Feb 1, 2017

Use of microextraction by packed sorbent directly coupled to an electron ionization single quadru... more Use of microextraction by packed sorbent directly coupled to an electron ionization single quadrupole mass spectrometer as an alternative for non-separative determinations, Journal of Chromatography B

Talanta, May 1, 2018

In this work, a method for the quantitative and qualitative analysis of 11 polycyclic aromatic hy... more In this work, a method for the quantitative and qualitative analysis of 11 polycyclic aromatic hydrocarbons (PAHs) in urine samples is reported. The method is based on the coupling of a programmed temperature vaporizer (PTV) with a quadrupole mass spectrometer (qMS), via a deactivated fused silica tubing. Before the PTV-qMS analysis, the samples were subjected to a liquid-liquid extraction (LLE). The method was rapid since no chromatographic separation was performed. The samples were introduced directly into the PTV, and the analytes were trapped in the Tenax-TA ® packed liner while the solvent was purged. After that, all the compounds reached the mass spectrometer, obtaining the fingerprint of the analysed samples. Urine samples free of PAHs and the same samples spiked with the compounds were analysed. The resulting profile signals were used to quantify the analytes using multivariate calibration, and to classify the samples according to the presence or absence of the PAHs. In the latter task, non-supervised and supervised pattern recognition techniques were employed. The calibration models worked satisfactorily and errors lower or equal to 15% were obtained, in most cases, when an external validation set was analysed. Regarding the classification of the samples, most of the supervised pattern recognition techniques provided excellent results (100% success), where all of the samples were classified correctly.

Microchemical Journal, 2020

Development of a fast and reliable methodology for the determination of polyamines in urine by us... more Development of a fast and reliable methodology for the determination of polyamines in urine by using a guard column as a low-resolution fractioning step prior to mass spectrometry. Comparison with flow injection-mass spectrometry analysis,

Analytical and bioanalytical chemistry, Jan 17, 2017

In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate... more In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate, 2-pentanone, 4-methyl-2-pentanone, 2-hexanone, 3-heptanone, 2-heptanone, 3-octanone, and 2-nonanone) have been analyzed to evaluate their different concentration levels in urine samples from lung cancer patients (n = 12) and healthy controls (n = 12). The volatile compounds were generated with a headspace autosampler and analyzed with a gas chromatograph equipped with a programmed temperature vaporizer and mass spectrometry detector (HS-PTV-GC-MS). With the aim of evaluating the aforementioned differences, a Mann-Whitney U test and box-plots were obtained. Very good discrimination between cancer and control groups was achieved for three (ethyl acetate, 3-heptanone, and 3-octanone) of the ten analytes studied. With a view to assigning samples to the group of healthy or ill individuals, the Wilcoxon signed-rank test has been used. In spite of the small number of urine samples assayed, th...

Encyclopedia of Analytical Chemistry, 2017

The process used to solve many analytical problems involves obtaining information on isolated com... more The process used to solve many analytical problems involves obtaining information on isolated compounds. Sample treatment is the costliest and most time-consuming part of the process and a frequent source of errors. However, sometimes it is not necessary to obtain information on individual compounds and profile signals are enough to make decisions. Here, electronic noses (e-noses) are considered within the possibilities of non-separative methods and specifically, electronic nose based on mass spectrometry (MS) in the bioanalysis field are discussed. These instrumental configurations are very attractive since sample treatment is eliminated or reduced and no chromatographic steps are required. Chemometric techniques are needed to extract the information from the signals. Endogenous volatile compounds provide important information about the state of the health of an individual and they can be analyzed with a MS-based electronic nose. Their use in disease detection is, basically, the adaptation of an ancient practice in medicine. In this work the main instrumental configurations based on this approach and some applications in the bioanalysis field considering noninvasive biological fluids are described. Keywords: MS-electronic nose; Chemometrics; mass spectrometry; bioanalysis; breath; saliva; urine

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 ...

Analytical and Bioanalytical Chemistry, 2009

A sensitive method for the fast analysis of filbertone in spiked olive oil samples is presented. ... more A sensitive method for the fast analysis of filbertone in spiked olive oil samples is presented. The applicability of a headspace (HS) autosampler in combination with a gas chromatograph (GC) equipped with a programmable temperature vaporizer (PTV) and a mass spectrometric (MS) detector is explored. 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, shortening total analysis cycle times to a considerable extent. The proposed method does not require any previous analyte extraction, filtration and preconcentration step, as in most methods described to date. Sample preparation is reduced to placing the olive oil sample in the vial. This reduces the analysis time and the experimental errors associated with this step of the analytical process. By using headspace generation, the volatiles of the sample are analysed without interference by the non-volatile matrix, and by using injection in solvent-vent mode at the PTV inlet, most of the compounds that are more volatile than filbertone are purged and the matrix effect is minimised. Use of a liner packed with Tenax-TA® allowed the compound of interest to be retained during the venting process. The limits of detection and quantification were as low as 0.27 and 0.83 µg/L, respectively, and precision (measured as the relative standard deviation) was 5.7%. The method was applied to the determination of filbertone in spiked olive oil samples and the results revealed the good accuracy obtained with the method.

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.

Microchemical Journal, 2021

Abstract Nowadays there is a great interest in the development of fast and reliable methods for t... more Abstract Nowadays there is a great interest in the development of fast and reliable methods for the determination of amino acids (AAs) in biological samples due to their biological importance. In the present work, a method based on the use of a guard column (gC) prior to tandem mass spectrometry (gC-MS/MS) is proposed for the determination of proteinogenic AAs in urine. Heptafluorobutyric acid (HFBA) is used as ion pairing reagent. Comparison of the gC-MS/MS method versus tandem mass spectrometry (MS/MS) in stand-alone mode showed improved sensitivity and peak shape, and solved some problems related to interfering compounds, with a total analysis time of 2.8 min. All the proteinogenic AAs were adequately determined using the gC-MS/MS method, except glutamic acid (Glu). To confirm quantitative results obtained with gC-MS/MS for individual AAs, an ion-pair liquid chromatography tandem mass spectrometry method (LC-MS/MS) has also been developed. Both methods (gC-MS/MS and LC-MS/MS) were validated using synthetic urine. For the gC-MS/MS method, LODs and LOQs values were found to be between 0.004 and 0.425 mg/L and 0.01 and 1.40 mg/L, respectively. Aspartic acid (Asp) showed the highest LOD and LOQ values (3 mg/L and 9 mg/L, respectively). A one-point standard addition method and internal standard normalization were used for the quantification because matrix effects were observed. L-alanine-1-13C (Ala-13C) and L-leucine-1-13C (Leu-13C) were used as isotopically labeled internal standards. To demonstrate the applicability of the gC-MS/MS method in the reliable determination of AAs in real samples, urine from eighteen healthy volunteers were analyzed using both gC-MS/MS and LC-MS/MS methods. Similar quantitative results were obtained for individual AAs with both of them. In addition, possible differences in AAs concentrations related to sex were checked, but the results did not show significant differences for the evaluated compounds.

Aldehydes and ketones are compounds of interest in environmental analysis, food analysis, and bio... more Aldehydes and ketones are compounds of interest in environmental analysis, food analysis, and bioanalysis. Gas chromatography is among the preferred choices for their determination in many different samples. Usually, a derivatization process is used before the chromatographic separation; the reagents most used for this have been extensively reviewed in the characteristics and possibilities of five derivatization reactions (2,4-dinitrophenylhydrazone, benzyloxime, pentafluorophenyl hydrazone, pentafluorobenzyloxime, and thiazolidine derivatization). In this update the focus is on the determination of aldehydes and ketones by gas chromatography–mass spectrometry with different sample treatment strategies.

Talanta, Feb 1, 2020

Amino acids have been of great interest in clinical studies since variation in their concentratio... more Amino acids have been of great interest in clinical studies since variation in their concentration may provide information about different disorders. For the first time, a non-separative method based on single quadrupole mass spectrometry (qMS) for the simultaneous semiquantitative determination of sixteen amino acids in saliva samples has been developed. The method includes derivatisation of amino acids with ethyl chloroformatepyridine-ethanol to obtain volatile products, liquid-liquid extraction (LLE) and further analysis using a programmed temperature vaporizer (PTV) coupled to qMS. This method could be applied to the analysis of a great number of saliva samples, limiting the use of separative methods only when abnormal concentrations of amino acids were found, reducing analysis time and cost. The results obtained in the determination of amino acids using the non-separative method were compared to those obtained when a separative method based on gas chromatography (GC) was used, providing values of average relative predictive error (E %) ranging between 2 and 48%. Repeatability and reproducibility were tested, obtaining relative standard deviation (RSD) values equal to or lower than 11% and 16%, respectively. Detection limits were in the range of 0.076-8.747 mg L −1 for the non-separative method.

Journal of Chromatography A, Sep 1, 2004

A high-speed quantitative analysis of methyl tert-butyl ether (MTBE) using three different method... more A high-speed quantitative analysis of methyl tert-butyl ether (MTBE) using three different methods with mass spectrometry detection has been performed. The first method is based on fast chromatography and required an analysis time of 5.23 min per sample, although a certain period (6 min) was necessary for the initial measurement conditions to be regained prior to analysing the next sample. The other two are non-separative methods and are based on direct injection and headspace generation. The analysis times were 1.5 and 3.5 min, respectively, although in the latter case an additional period of time was required to extract volatiles from the sample. The analytical characteristics of all three methods are highly satisfactory in terms of linearity, lack of fit, precision and accuracy. The methods were applied to the determination of MTBE in different gasoline samples. The non-separative methods afforded slightly higher concentrations than those found when fast chromatography was used; this is due to the presence of other minor components that contribute to the abundance of the ion at m/z 73, characteristic of MTBE. We propose a correction that removes this error very satisfactorily and allows the same results to be obtained with all three methodologies proposed.

Analytical and Bioanalytical Chemistry, Jul 17, 2017

In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate... more In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate, 2-pentanone, 4-methyl-2-pentanone, 2-hexanone, 3-heptanone, 2heptanone, 3-octanone, and 2-nonanone) have been analyzed to evaluate their different concentration levels in urine samples from lung cancer patients (n = 12) and healthy controls (n = 12). The volatile compounds were generated with a headspace autosampler and analyzed with a gas chromatograph equipped with a programmed temperature vaporizer and mass spectrometry detector (HS-PTV-GC-MS). With the aim of evaluating the aforementioned differences, a Mann-Whitney U test and box-plots were obtained. Very good discrimination between cancer and control groups was achieved for three (ethyl acetate, 3-heptanone, and 3-octanone) of the ten analytes studied. With a view to assigning samples to the group of healthy or ill individuals, the Wilcoxon signed-rank test has been used. In spite of the small number of urine samples assayed, the results may suggest that the studied compounds could be considered useful tools in order to discern samples and they could be employed as a complementary test in a diagnosis.

Talanta, 2019

Liquidliquid extraction-programmed temperature vaporizer-gas chromatography-mass spectrometry for... more Liquidliquid extraction-programmed temperature vaporizer-gas chromatography-mass spectrometry for the determination of polycyclic aromatic hydrocarbons in saliva samples. Application to the occupational exposure of firefighters, Talanta,

Talanta, Nov 1, 2016

A rapid method for the analysis of volatiles in saliva samples is proposed. The method is based o... more A rapid method for the analysis of volatiles in saliva samples is proposed. The method is based on direct coupling of three components: a headspace sampler (HS), a programmable temperature vaporizer (PTV) and a quadrupole mass spectrometer (qMS). Several applications in the biomedical field have been proposed with electronic noses based on different sensors. However, few contributions have been developed using a mass spectrometry-based electronic nose in this field up to date. Samples of 23 patients with some type of cancer and 32 healthy volunteers were analyzed with HS-PTV-MS and the profile signals obtained were subjected to pattern recognition techniques with the aim of studying the possibilities of the methodology to differentiate patients with cancer from healthy controls. An initial inspection of the contained information in the data by means of principal components analysis (PCA) revealed a complex situation were an overlapped distribution of samples in the score plot was visualized instead of two groups of separated samples. Models using K-nearest neighbors (KNN) and Soft Independent Modeling of Class Analogy (SIMCA) showed poor discrimination, specially using SIMCA where a small distance between classes was obtained and no satisfactory results in the classification of the external validation samples were achieved. Good results were obtained when Mahalanobis discriminant analysis (DA) and support vector machines (SVM) were used obtaining 2 (false positives) and 0 samples misclassified in the external validation set, respectively. No false negatives were found using these techniques.

Microchemical Journal, 2020

A sensitive method for the quantification of polycyclic aromatic hydrocarbons (PAHs) in saliva sa... more A sensitive method for the quantification of polycyclic aromatic hydrocarbons (PAHs) in saliva samples is proposed. The method is based on the use of microextraction by packed sorbents (MEPS), injection with programmed temperature vaporizer (PTV), gas chromatography (GC) and mass spectrometry with a single quadrupole (MS). As far as we know, the MEPS technique has not been used to date for the analysis of PAHs in saliva samples. Sample treatment carried out only involves centrifugation and filtration of the saliva sample, which is subjected to the MEPS process without dilution. Standard addition was used as a calibration strategy, due to the matrix effect found using ultrapure water and among the different saliva samples. Nine saliva samples were analysed and phenanthrene was found (15 ± 6 ng L −1) in one of them. To confirm the accuracy of the method, the concentrations added in the standard additions were compared with the value predicted by the calibration model. The values ranged between 78 and 123%. The limits of detection (LOD) found in the saliva samples ranged between 4.6 and 79 ng L −1 and the repeatability and reproducibility were always equal to or lower than 10 and 17%, respectively. The main advantage of the proposed methodology over the existing ones is the complete automation of the analysis process (extraction, separation and detection). Once the saliva sample is placed in the vial, the entire process occurs on-line.

Social Science Research Network, 2022

Journal of Chromatography B, Oct 1, 2019

Here we show the determination of different polyamines (putrescine, cadaverine, spermidine) and r... more Here we show the determination of different polyamines (putrescine, cadaverine, spermidine) and related compounds (gamma-aminobutyric acid and L-ornithine) in saliva samples. These compounds are known to be biomarkers for several diseases. We have optimised an in situ derivatization process using ethyl chloroformate, an automated microextraction by packed sorbent and the determination of the corresponding products using a programmed temperature vaporizer coupled to a gas chromatograph-mass spectrometer. After finding that saliva matrix has an effect on the analysis, quantitation was performed using the one-point standard additions method and normalization to IS. This allows the detection of the analytes in the range of µg/L within a matrix obtained by a non-invasive procedure. The method has been successfully validated and it has been used in the determination of these compounds in six saliva samples finding that putrescine and cadaverine present the highest concentrations in the subject diagnosed with rheumatoid arthritis. For ornithine and spermidine, the highest concentrations were found for male subjects, especially heavy smokers. All concentrations found for the compounds were in good agreement with data found in bibliography.

Journal of Chromatography B, Feb 1, 2017

Use of microextraction by packed sorbent directly coupled to an electron ionization single quadru... more Use of microextraction by packed sorbent directly coupled to an electron ionization single quadrupole mass spectrometer as an alternative for non-separative determinations, Journal of Chromatography B

Talanta, May 1, 2018

In this work, a method for the quantitative and qualitative analysis of 11 polycyclic aromatic hy... more In this work, a method for the quantitative and qualitative analysis of 11 polycyclic aromatic hydrocarbons (PAHs) in urine samples is reported. The method is based on the coupling of a programmed temperature vaporizer (PTV) with a quadrupole mass spectrometer (qMS), via a deactivated fused silica tubing. Before the PTV-qMS analysis, the samples were subjected to a liquid-liquid extraction (LLE). The method was rapid since no chromatographic separation was performed. The samples were introduced directly into the PTV, and the analytes were trapped in the Tenax-TA ® packed liner while the solvent was purged. After that, all the compounds reached the mass spectrometer, obtaining the fingerprint of the analysed samples. Urine samples free of PAHs and the same samples spiked with the compounds were analysed. The resulting profile signals were used to quantify the analytes using multivariate calibration, and to classify the samples according to the presence or absence of the PAHs. In the latter task, non-supervised and supervised pattern recognition techniques were employed. The calibration models worked satisfactorily and errors lower or equal to 15% were obtained, in most cases, when an external validation set was analysed. Regarding the classification of the samples, most of the supervised pattern recognition techniques provided excellent results (100% success), where all of the samples were classified correctly.

Microchemical Journal, 2020

Development of a fast and reliable methodology for the determination of polyamines in urine by us... more Development of a fast and reliable methodology for the determination of polyamines in urine by using a guard column as a low-resolution fractioning step prior to mass spectrometry. Comparison with flow injection-mass spectrometry analysis,

Analytical and bioanalytical chemistry, Jan 17, 2017

In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate... more In this work, ten possible volatile biomarkers of lung cancer (acetone, 2-butanone, ethyl acetate, 2-pentanone, 4-methyl-2-pentanone, 2-hexanone, 3-heptanone, 2-heptanone, 3-octanone, and 2-nonanone) have been analyzed to evaluate their different concentration levels in urine samples from lung cancer patients (n = 12) and healthy controls (n = 12). The volatile compounds were generated with a headspace autosampler and analyzed with a gas chromatograph equipped with a programmed temperature vaporizer and mass spectrometry detector (HS-PTV-GC-MS). With the aim of evaluating the aforementioned differences, a Mann-Whitney U test and box-plots were obtained. Very good discrimination between cancer and control groups was achieved for three (ethyl acetate, 3-heptanone, and 3-octanone) of the ten analytes studied. With a view to assigning samples to the group of healthy or ill individuals, the Wilcoxon signed-rank test has been used. In spite of the small number of urine samples assayed, th...

Encyclopedia of Analytical Chemistry, 2017

The process used to solve many analytical problems involves obtaining information on isolated com... more The process used to solve many analytical problems involves obtaining information on isolated compounds. Sample treatment is the costliest and most time-consuming part of the process and a frequent source of errors. However, sometimes it is not necessary to obtain information on individual compounds and profile signals are enough to make decisions. Here, electronic noses (e-noses) are considered within the possibilities of non-separative methods and specifically, electronic nose based on mass spectrometry (MS) in the bioanalysis field are discussed. These instrumental configurations are very attractive since sample treatment is eliminated or reduced and no chromatographic steps are required. Chemometric techniques are needed to extract the information from the signals. Endogenous volatile compounds provide important information about the state of the health of an individual and they can be analyzed with a MS-based electronic nose. Their use in disease detection is, basically, the adaptation of an ancient practice in medicine. In this work the main instrumental configurations based on this approach and some applications in the bioanalysis field considering noninvasive biological fluids are described. Keywords: MS-electronic nose; Chemometrics; mass spectrometry; bioanalysis; breath; saliva; urine

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 ...

Analytical and Bioanalytical Chemistry, 2009

A sensitive method for the fast analysis of filbertone in spiked olive oil samples is presented. ... more A sensitive method for the fast analysis of filbertone in spiked olive oil samples is presented. The applicability of a headspace (HS) autosampler in combination with a gas chromatograph (GC) equipped with a programmable temperature vaporizer (PTV) and a mass spectrometric (MS) detector is explored. 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, shortening total analysis cycle times to a considerable extent. The proposed method does not require any previous analyte extraction, filtration and preconcentration step, as in most methods described to date. Sample preparation is reduced to placing the olive oil sample in the vial. This reduces the analysis time and the experimental errors associated with this step of the analytical process. By using headspace generation, the volatiles of the sample are analysed without interference by the non-volatile matrix, and by using injection in solvent-vent mode at the PTV inlet, most of the compounds that are more volatile than filbertone are purged and the matrix effect is minimised. Use of a liner packed with Tenax-TA® allowed the compound of interest to be retained during the venting process. The limits of detection and quantification were as low as 0.27 and 0.83 µg/L, respectively, and precision (measured as the relative standard deviation) was 5.7%. The method was applied to the determination of filbertone in spiked olive oil samples and the results revealed the good accuracy obtained with the method.

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.

Microchemical Journal, 2021

Abstract Nowadays there is a great interest in the development of fast and reliable methods for t... more Abstract Nowadays there is a great interest in the development of fast and reliable methods for the determination of amino acids (AAs) in biological samples due to their biological importance. In the present work, a method based on the use of a guard column (gC) prior to tandem mass spectrometry (gC-MS/MS) is proposed for the determination of proteinogenic AAs in urine. Heptafluorobutyric acid (HFBA) is used as ion pairing reagent. Comparison of the gC-MS/MS method versus tandem mass spectrometry (MS/MS) in stand-alone mode showed improved sensitivity and peak shape, and solved some problems related to interfering compounds, with a total analysis time of 2.8 min. All the proteinogenic AAs were adequately determined using the gC-MS/MS method, except glutamic acid (Glu). To confirm quantitative results obtained with gC-MS/MS for individual AAs, an ion-pair liquid chromatography tandem mass spectrometry method (LC-MS/MS) has also been developed. Both methods (gC-MS/MS and LC-MS/MS) were validated using synthetic urine. For the gC-MS/MS method, LODs and LOQs values were found to be between 0.004 and 0.425 mg/L and 0.01 and 1.40 mg/L, respectively. Aspartic acid (Asp) showed the highest LOD and LOQ values (3 mg/L and 9 mg/L, respectively). A one-point standard addition method and internal standard normalization were used for the quantification because matrix effects were observed. L-alanine-1-13C (Ala-13C) and L-leucine-1-13C (Leu-13C) were used as isotopically labeled internal standards. To demonstrate the applicability of the gC-MS/MS method in the reliable determination of AAs in real samples, urine from eighteen healthy volunteers were analyzed using both gC-MS/MS and LC-MS/MS methods. Similar quantitative results were obtained for individual AAs with both of them. In addition, possible differences in AAs concentrations related to sex were checked, but the results did not show significant differences for the evaluated compounds.