In this paper we are going to describe a data mining tool, whose aim is to help authors or teache... more In this paper we are going to describe a data mining tool, whose aim is to help authors or teachers to discovery interesting information from students' usage information. The teacher can use this information to improve and personalize adaptive hypermedia courses to theirs students. We propose to use sequential pattern mining algorithms to discover the most used path by the students and from this information can recommend links to the new students automatically meanwhile they browse in the course. We have developed a specific author ...
Marine echinoderms are filter-feeding invertebrates widely distributed along the coasts, and whic... more Marine echinoderms are filter-feeding invertebrates widely distributed along the coasts, and which are therefore extensively exposed to anthropogenic xenobiotics. They can serve as good sentinels for monitoring a large variety of contaminants in marine ecosystems. In this context, a multi-residue analytical method has been validated and applied to Holothuria tubulosa specimens and marine sediments for the determination of 36 organic compounds, which belong to some of the most problematic groups of emerging and priority pollutants (perfluoroalkyl compounds, estrogens, parabens, benzophenones, plasticizers, surfactants, brominated flame retardants and alkylphenols). Lyophilization of samples prior to solvent extraction and clean-up of extracts with C18, followed by liquid chromatography-tandem mass spectrometry analysis, is proposed. A Box-Behnken design was used for optimization of the most influential variables affecting the extraction and clean-up steps. For validation, matrix-matc...
An accurate and sensitive method for the determination of selected EDCs in soil and compost from ... more An accurate and sensitive method for the determination of selected EDCs in soil and compost from wastewater treatment plants is developed and validated. Five parabens, six benzophenone-UV filters and the antibacterials triclosan and triclocarban were selected as target analytes. The parameters for ultrasound-assisted extraction were thoroughly optimized. After extraction, the analytes were detected and quantified using ultra high performance liquid chromatography tandem mass spectrometry. Ethylparaben (ring-13 C 6 labelled) and deuterated benzophenone (BP-d 10) were used as internal standards. The method was validated using matrix-matched calibration and recovery assays with spiked samples. The limits of detection ranged from 0.03 to 0.40 ng g-1 and the limits of quantification from 0.1 to 1.0 ng g-1 , while precision in terms of relative standard deviation was between 9% and 21%. Recovery rates ranged from 83% to 107%. The validated method was applied for the study of the behavior of the selected compounds in agricultural soils treated and untreated with compost from WWTP. A lixiviation study was developed in both agricultural soil and treated soil and first order kinetic models of their disappearance at different depths are proposed. The application of organic composts in the soil leads to an increase of the disappearance rate of the studied compounds. The lixiviation study also shows the risk of pollution of groundwater aquifers after disposal or waste of these EDCs in agricultural soils is not high.
This work presents a comparison of three extraction techniques -ultrasound-assisted extraction (U... more This work presents a comparison of three extraction techniques -ultrasound-assisted extraction (USE), microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) - and evaluates their efficiency in the determination of quinolone antibiotics in sewage sludge samples. Extraction parameters for each technique were optimized using design of experiments, and the compounds were detected and quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS), operating in positive electrospray ionization (ESI) mode. The use of two selected reaction monitoring transitions for each compound allowed simultaneous quantification and identification in one run. Analytes were separated in less than 10 min. Marbofloxacin and cincophen were used as surrogates for amphoteric and acid quinolones, respectively. The limits of detection (LODs) were between 2 and 5 ng g(-1), and the limits of quantification (LOQs) were between 4 and 18 ng g(-1) for the various analytes. The inter- and intra-day variability was <7%. Due to the absence of certified reference materials (CRMs), the method was validated using matrix-matched calibration and a recovery assay with spiked samples. Recovery rates were between 97.9% and 104.8%. Statistical comparison demonstrated no significant differences between the three extraction techniques. The methods were successfully applied for the determination of quinolones in sewage sludge samples collected from different wastewater treatments plants (WWTPs) located in the province of Granada (Spain). The analytical methods developed here may be useful for the development of more in-depth studies on the occurrence and fate of these commonly used pharmaceuticals in WWTPs and in the environment.
An analytical method for the simultaneous determination of trace amounts of fourteen endocrine di... more An analytical method for the simultaneous determination of trace amounts of fourteen endocrine disrupter chemicals (EDCs) in urban wastewater samples has been developed. The studied compounds were: bisphenol A and its chlorinated derivatives (monochloro, dichloro, trichloro and tretrachlorobisphenol A), three alkylphenols (4-n-nonyl, 4-n-octyl and 4-(tert-octyl)phenol) and six well known phthalate esters (dimethyl, diethyl, di-n-butyl, butylbenzyl, bis(2-ethylhexyl) and di-n-octylphthalate). The method
Alcohol sulfates (AS) and alcohol ethoxysulfates (AES) are all High Production Volume and 'down-t... more Alcohol sulfates (AS) and alcohol ethoxysulfates (AES) are all High Production Volume and 'down-thedrain' chemicals used globally in detergent and personal care products, resulting in low levels ultimately released to the environment via wastewater treatment plant effluents. They have a strong affinity for sorption to sediments. Almost 50% of Tenerife Island surface area is environmentally protected. Therefore, determination of concentration levels of AS/AES in marine sediments near wastewater discharge points along the coast of the Island is of interest. These data were obtained after pressurized liquid extraction and liquid chromatography-tandem mass spectrometry analysis. Short chains of AES and especially of AS dominated the homologue distribution for AES. The Principal Components Analysis was used. The results showed that the sources of AS and AES were the same and that both compounds exhibit similar behavior. Three different patterns in the distribution for homologues and ethoxymers were found.
International Journal of Environmental Science and Technology, 2013
The effect of the injection of pure oxygen instead of air in a membrane bioreactor for the elimin... more The effect of the injection of pure oxygen instead of air in a membrane bioreactor for the elimination of bisphenol A is investigated. A dynamic experiment was developed in a pilot plant where the aerobic reactor was continuously spiked with 1 mg L-1 of bisphenol A. Air was injected for 10 days and then pure oxygen was injected for another 10 days. The bisphenol A concentration was determined in aqueous phases and activated sludge using simple and sensitive analytical methods based on different extraction procedures and liquid chromatography tandem mass spectrometry analysis. Enzymatic activity was also determined and toxicity tests were performed to discard that the spiked bisphenol A concentration could negatively affect the microorganisms in the bioreactor and, thus, the membrane bioreactor performance. The effluent bisphenol A concentration increased up to 0.26 mg L-1 after 4 days in the air injection treatment, and up to 0.48 mg L-1 after only 12 h in the oxygen injection treatment. In both cases, this was followed by a decrease in concentration despite the continuous spiking of bisphenol A into the bioreactor. In presence of pure oxygen, bisphenol A concentration reached background levels (below the limit of quantification) after 5 days. In contrast, when using air a total of 10 days were required to reach background levels. The injection of pure oxygen instead of air is an important innovation in wastewater treatment, allowing permanent elimination of organic contaminants, avoiding their return to the environment and ensuring the safety of water.
A new liquid chromatography-mass spectrometry (LC-MS) method has been developed and validated for... more A new liquid chromatography-mass spectrometry (LC-MS) method has been developed and validated for the simultaneous determination of eight quinolone antibacterials for veterinary use in processed bovine milk samples. The quinolones studied included marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid and flumequine. Also, a new sample-treatment procedure was used for extraction and preconcentration of these compounds. It involved defatting by centrifugation, protein precipitation by adding a mixture of glacial acetic acid-acetonitrile and removing acetonitrile with dichloromethane; finally, the acidified aqueous layer was evaporated to dryness in a speed vac system, resuspended in the mobile phase and filtered prior to LC injection. The mobile phase was composed of a formic acid aqueous solution 0.1% (v/v) and acetonitrile, with an initial composition of water-acetonitrile 95: 5 (v/v) and using linear gradient elution. Norfloxacin was used as internal standard. The limits of quantification found (2-7 ng g −1) were in all cases lower than the maximum residue limits tolerated by the European Union for these compounds in milk.
The present paper describes the calibration of selected passive samplers used in the quantitation... more The present paper describes the calibration of selected passive samplers used in the quantitation of trichlorophenol and trichloroanisole in wineries' ambient air, by calculating the corresponding sampling rates. The method is based on passive sampling with sorbent tubes and involves thermal desorption-gas chromatography-triple quadrupole mass spectrometry analysis. Three commercially available sorbents were tested using sampling cartridges with a radial design instead of axial ones. The best results were found for Tenax TA TM. Sampling rates (R-values) for the selected sorbents were determined. Passive sampling was also used for accurately determining the amount of compounds present in the air. Adequate correlation coefficients between the mass of the target analytes and exposure time were obtained. The proposed validated method is a useful tool for the early detection of trichloroanisole and its precursor trichlorophenol in wineries' ambient air while avoiding contamination of wine or winery facilities.
Abstract X-ray Powder Diffraction (XRPD) is one of the non-destructive techniques habitually used... more Abstract X-ray Powder Diffraction (XRPD) is one of the non-destructive techniques habitually used for the structural analysis of crystalline solids. This technique can therefore be used to differentiate between crystalline and vitreous or amorphous solids such as Smalt Cobalt Blue or the binders used in paints. The “final” pigments used in the artist's palette are frequently composed of a complex mixture of inorganic and organic compounds, causing different interferences and matrix effects, such as filtering and signal overlapping and background noise increase. These effects can make difficult pigment identification and quantification contributing to mischaracterization. Nevertheless, when the experimental difficulties can be overcome, the results obtained are precise, definitive and useful. In the present research, the limitations were avoided or minimized by using an algorithm for data analysis like the one used by the XPowder™ software. In addition, most of the natural pigments used in the painting The Little Madonna of Foligno are identified and quantified. The preparation layers are composed of white lead, along with a homogeneous mix of several arsenic sulfides and small amounts of roselite. The color layer contains lapis lazuli and minor azurite for the blue colors, and cinnabar for the red ones. Other pigments found were: lead‑tin yellow, iron(III) oxy-hydroxides (red and yellow ochers), celadonite (green earth), and possibly olivine, diopside and other ferromagnesian minerals in the form of pyroxenes and amphiboles, whose diffraction lines also appear in the diffractograms, although with weak intensities and precise quantifications are not allowed. Crystalline Thenard's blue was not found.
A method for the quantitative determination of 1,2,3-propanetrioltrinitrate (nitroglycerin) in hu... more A method for the quantitative determination of 1,2,3-propanetrioltrinitrate (nitroglycerin) in human plasma by gas chromatography mass spectrometry has been developed. After addition of 1,2,3propanetriol(I5N)trinitrate as internal standard, plasma (1 ml) is extracted by a mixture of pentane and methyl acetate (90: 10). The extracts are purified by partition between, first, the extraction solvent and a mixture of acetonitrile and water (60:40) and, secondly, the resultant aqueous phase and benzene. The solvent is evaporated to a small volume before injection. The fragment ions at m / z 46 and 47 are monitored for the measurement of the [NOz]+ and ['sNOz]' ions using electron impact ionization. The mean recovery (%) I S D in blind plasma samples spiked with amounts in the concentration range 0.35-3.52 nmol I-', was 97.4 f 9.0 (n = 58). Within a day, recovery experiments gave rise to coefficients of variation of 9.6,6.4 and 2.7% at the levels 0.44,0.88 and 11 nmol I-', respectively. Concentrations in plasma down to about 0.2 nmol I-' (50 pg ml-I) could be estimated. Percent recovery of duplicate determinations in the range 0.5-1.96 nmol I-' f SD was 99.4 f 6.0 (n = 80).
The group of compounds commonly called endocrine disruptors covers a wide range of synthetic and ... more The group of compounds commonly called endocrine disruptors covers a wide range of synthetic and natural substances able to alter the normal hormone function of wildlife and humans, consequently causing adverse health effects. Bisphenol A (BPA) and its chlorinated derivatives are some of these compounds. In this work, we propose a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine these compounds in human placental tissue samples. The method involves an extraction phase of the extracts from the samples using ethyl acetate, followed by a clean-up phase by centrifugation prior to their quantification by LC-MS/MS using an atmospheric pressure chemical ionization (APCI) interface in the negative mode. Deuterated Bisphenol A (BPA-d(16)) was used as internal standard. Found detection limits (DL) ranged from 0.2 to 0.6 ng g(-1) and quantification limits (QL) from 0.5 to 2.0 ng g(-1) for Bisphenol A and its chlorinated derivatives, while inter- and intra-day variability was under 8.1%. The method was validated using standard addition calibration and a spike recovery assay. Recovery rates for spiked samples ranged from 97% to 105%. This method was satisfactorily applied to the determination of BPA and its chlorinated derivatives in 49 placental tissue samples collected from women who live in the province of Granada (Spain).
This paper presents a comparison of three extraction techniques-ultrasound-assisted extraction, m... more This paper presents a comparison of three extraction techniques-ultrasound-assisted extraction, microwave-assisted extraction and pressurized liquid extraction-in order to evaluate their efficiency in the determination of bisphenol A and its chlorinated derivatives in sewage sludge samples. Extraction parameters for each technique were accurately optimized to achieve the highest recoveries. The selected compounds were detected and quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS), operating in negative atmospheric pressure chemical ionization (APCI) and in multiple reaction monitoring (MRM) mode. The analytes were separated in less than 6 min. BPA-d 16 was used as internal standard. Three selective, sensitive, robust and accurate analytical methods were developed. The limits of detection (LODs) of the methods ranged from 2 to 9 ng g −1 and the limits of quantification (LOQs) from 8 to 26 ng g −1 , while inter-and intra-day variability was under 6% in all cases. Given the absence of certified reference materials (CRMs), the methods were validated separately by using matrix-matched calibration and recovery assays with spiked samples. Recovery rates ranged from 97.7% to 103.1%. The sewage sludge samples used for experiments were collected from two different wastewater treatments plants (WWTPs) located in the province of Granada (South-East Spain). The statistical comparison of the methods demonstrated no statistically significant differences between the extraction techniques for the determination of BPA and chlorinated derivatives in sludge samples.
In this paper we are going to describe a data mining tool, whose aim is to help authors or teache... more In this paper we are going to describe a data mining tool, whose aim is to help authors or teachers to discovery interesting information from students' usage information. The teacher can use this information to improve and personalize adaptive hypermedia courses to theirs students. We propose to use sequential pattern mining algorithms to discover the most used path by the students and from this information can recommend links to the new students automatically meanwhile they browse in the course. We have developed a specific author ...
Marine echinoderms are filter-feeding invertebrates widely distributed along the coasts, and whic... more Marine echinoderms are filter-feeding invertebrates widely distributed along the coasts, and which are therefore extensively exposed to anthropogenic xenobiotics. They can serve as good sentinels for monitoring a large variety of contaminants in marine ecosystems. In this context, a multi-residue analytical method has been validated and applied to Holothuria tubulosa specimens and marine sediments for the determination of 36 organic compounds, which belong to some of the most problematic groups of emerging and priority pollutants (perfluoroalkyl compounds, estrogens, parabens, benzophenones, plasticizers, surfactants, brominated flame retardants and alkylphenols). Lyophilization of samples prior to solvent extraction and clean-up of extracts with C18, followed by liquid chromatography-tandem mass spectrometry analysis, is proposed. A Box-Behnken design was used for optimization of the most influential variables affecting the extraction and clean-up steps. For validation, matrix-matc...
An accurate and sensitive method for the determination of selected EDCs in soil and compost from ... more An accurate and sensitive method for the determination of selected EDCs in soil and compost from wastewater treatment plants is developed and validated. Five parabens, six benzophenone-UV filters and the antibacterials triclosan and triclocarban were selected as target analytes. The parameters for ultrasound-assisted extraction were thoroughly optimized. After extraction, the analytes were detected and quantified using ultra high performance liquid chromatography tandem mass spectrometry. Ethylparaben (ring-13 C 6 labelled) and deuterated benzophenone (BP-d 10) were used as internal standards. The method was validated using matrix-matched calibration and recovery assays with spiked samples. The limits of detection ranged from 0.03 to 0.40 ng g-1 and the limits of quantification from 0.1 to 1.0 ng g-1 , while precision in terms of relative standard deviation was between 9% and 21%. Recovery rates ranged from 83% to 107%. The validated method was applied for the study of the behavior of the selected compounds in agricultural soils treated and untreated with compost from WWTP. A lixiviation study was developed in both agricultural soil and treated soil and first order kinetic models of their disappearance at different depths are proposed. The application of organic composts in the soil leads to an increase of the disappearance rate of the studied compounds. The lixiviation study also shows the risk of pollution of groundwater aquifers after disposal or waste of these EDCs in agricultural soils is not high.
This work presents a comparison of three extraction techniques -ultrasound-assisted extraction (U... more This work presents a comparison of three extraction techniques -ultrasound-assisted extraction (USE), microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) - and evaluates their efficiency in the determination of quinolone antibiotics in sewage sludge samples. Extraction parameters for each technique were optimized using design of experiments, and the compounds were detected and quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS), operating in positive electrospray ionization (ESI) mode. The use of two selected reaction monitoring transitions for each compound allowed simultaneous quantification and identification in one run. Analytes were separated in less than 10 min. Marbofloxacin and cincophen were used as surrogates for amphoteric and acid quinolones, respectively. The limits of detection (LODs) were between 2 and 5 ng g(-1), and the limits of quantification (LOQs) were between 4 and 18 ng g(-1) for the various analytes. The inter- and intra-day variability was <7%. Due to the absence of certified reference materials (CRMs), the method was validated using matrix-matched calibration and a recovery assay with spiked samples. Recovery rates were between 97.9% and 104.8%. Statistical comparison demonstrated no significant differences between the three extraction techniques. The methods were successfully applied for the determination of quinolones in sewage sludge samples collected from different wastewater treatments plants (WWTPs) located in the province of Granada (Spain). The analytical methods developed here may be useful for the development of more in-depth studies on the occurrence and fate of these commonly used pharmaceuticals in WWTPs and in the environment.
An analytical method for the simultaneous determination of trace amounts of fourteen endocrine di... more An analytical method for the simultaneous determination of trace amounts of fourteen endocrine disrupter chemicals (EDCs) in urban wastewater samples has been developed. The studied compounds were: bisphenol A and its chlorinated derivatives (monochloro, dichloro, trichloro and tretrachlorobisphenol A), three alkylphenols (4-n-nonyl, 4-n-octyl and 4-(tert-octyl)phenol) and six well known phthalate esters (dimethyl, diethyl, di-n-butyl, butylbenzyl, bis(2-ethylhexyl) and di-n-octylphthalate). The method
Alcohol sulfates (AS) and alcohol ethoxysulfates (AES) are all High Production Volume and 'down-t... more Alcohol sulfates (AS) and alcohol ethoxysulfates (AES) are all High Production Volume and 'down-thedrain' chemicals used globally in detergent and personal care products, resulting in low levels ultimately released to the environment via wastewater treatment plant effluents. They have a strong affinity for sorption to sediments. Almost 50% of Tenerife Island surface area is environmentally protected. Therefore, determination of concentration levels of AS/AES in marine sediments near wastewater discharge points along the coast of the Island is of interest. These data were obtained after pressurized liquid extraction and liquid chromatography-tandem mass spectrometry analysis. Short chains of AES and especially of AS dominated the homologue distribution for AES. The Principal Components Analysis was used. The results showed that the sources of AS and AES were the same and that both compounds exhibit similar behavior. Three different patterns in the distribution for homologues and ethoxymers were found.
International Journal of Environmental Science and Technology, 2013
The effect of the injection of pure oxygen instead of air in a membrane bioreactor for the elimin... more The effect of the injection of pure oxygen instead of air in a membrane bioreactor for the elimination of bisphenol A is investigated. A dynamic experiment was developed in a pilot plant where the aerobic reactor was continuously spiked with 1 mg L-1 of bisphenol A. Air was injected for 10 days and then pure oxygen was injected for another 10 days. The bisphenol A concentration was determined in aqueous phases and activated sludge using simple and sensitive analytical methods based on different extraction procedures and liquid chromatography tandem mass spectrometry analysis. Enzymatic activity was also determined and toxicity tests were performed to discard that the spiked bisphenol A concentration could negatively affect the microorganisms in the bioreactor and, thus, the membrane bioreactor performance. The effluent bisphenol A concentration increased up to 0.26 mg L-1 after 4 days in the air injection treatment, and up to 0.48 mg L-1 after only 12 h in the oxygen injection treatment. In both cases, this was followed by a decrease in concentration despite the continuous spiking of bisphenol A into the bioreactor. In presence of pure oxygen, bisphenol A concentration reached background levels (below the limit of quantification) after 5 days. In contrast, when using air a total of 10 days were required to reach background levels. The injection of pure oxygen instead of air is an important innovation in wastewater treatment, allowing permanent elimination of organic contaminants, avoiding their return to the environment and ensuring the safety of water.
A new liquid chromatography-mass spectrometry (LC-MS) method has been developed and validated for... more A new liquid chromatography-mass spectrometry (LC-MS) method has been developed and validated for the simultaneous determination of eight quinolone antibacterials for veterinary use in processed bovine milk samples. The quinolones studied included marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid and flumequine. Also, a new sample-treatment procedure was used for extraction and preconcentration of these compounds. It involved defatting by centrifugation, protein precipitation by adding a mixture of glacial acetic acid-acetonitrile and removing acetonitrile with dichloromethane; finally, the acidified aqueous layer was evaporated to dryness in a speed vac system, resuspended in the mobile phase and filtered prior to LC injection. The mobile phase was composed of a formic acid aqueous solution 0.1% (v/v) and acetonitrile, with an initial composition of water-acetonitrile 95: 5 (v/v) and using linear gradient elution. Norfloxacin was used as internal standard. The limits of quantification found (2-7 ng g −1) were in all cases lower than the maximum residue limits tolerated by the European Union for these compounds in milk.
The present paper describes the calibration of selected passive samplers used in the quantitation... more The present paper describes the calibration of selected passive samplers used in the quantitation of trichlorophenol and trichloroanisole in wineries' ambient air, by calculating the corresponding sampling rates. The method is based on passive sampling with sorbent tubes and involves thermal desorption-gas chromatography-triple quadrupole mass spectrometry analysis. Three commercially available sorbents were tested using sampling cartridges with a radial design instead of axial ones. The best results were found for Tenax TA TM. Sampling rates (R-values) for the selected sorbents were determined. Passive sampling was also used for accurately determining the amount of compounds present in the air. Adequate correlation coefficients between the mass of the target analytes and exposure time were obtained. The proposed validated method is a useful tool for the early detection of trichloroanisole and its precursor trichlorophenol in wineries' ambient air while avoiding contamination of wine or winery facilities.
Abstract X-ray Powder Diffraction (XRPD) is one of the non-destructive techniques habitually used... more Abstract X-ray Powder Diffraction (XRPD) is one of the non-destructive techniques habitually used for the structural analysis of crystalline solids. This technique can therefore be used to differentiate between crystalline and vitreous or amorphous solids such as Smalt Cobalt Blue or the binders used in paints. The “final” pigments used in the artist's palette are frequently composed of a complex mixture of inorganic and organic compounds, causing different interferences and matrix effects, such as filtering and signal overlapping and background noise increase. These effects can make difficult pigment identification and quantification contributing to mischaracterization. Nevertheless, when the experimental difficulties can be overcome, the results obtained are precise, definitive and useful. In the present research, the limitations were avoided or minimized by using an algorithm for data analysis like the one used by the XPowder™ software. In addition, most of the natural pigments used in the painting The Little Madonna of Foligno are identified and quantified. The preparation layers are composed of white lead, along with a homogeneous mix of several arsenic sulfides and small amounts of roselite. The color layer contains lapis lazuli and minor azurite for the blue colors, and cinnabar for the red ones. Other pigments found were: lead‑tin yellow, iron(III) oxy-hydroxides (red and yellow ochers), celadonite (green earth), and possibly olivine, diopside and other ferromagnesian minerals in the form of pyroxenes and amphiboles, whose diffraction lines also appear in the diffractograms, although with weak intensities and precise quantifications are not allowed. Crystalline Thenard's blue was not found.
A method for the quantitative determination of 1,2,3-propanetrioltrinitrate (nitroglycerin) in hu... more A method for the quantitative determination of 1,2,3-propanetrioltrinitrate (nitroglycerin) in human plasma by gas chromatography mass spectrometry has been developed. After addition of 1,2,3propanetriol(I5N)trinitrate as internal standard, plasma (1 ml) is extracted by a mixture of pentane and methyl acetate (90: 10). The extracts are purified by partition between, first, the extraction solvent and a mixture of acetonitrile and water (60:40) and, secondly, the resultant aqueous phase and benzene. The solvent is evaporated to a small volume before injection. The fragment ions at m / z 46 and 47 are monitored for the measurement of the [NOz]+ and ['sNOz]' ions using electron impact ionization. The mean recovery (%) I S D in blind plasma samples spiked with amounts in the concentration range 0.35-3.52 nmol I-', was 97.4 f 9.0 (n = 58). Within a day, recovery experiments gave rise to coefficients of variation of 9.6,6.4 and 2.7% at the levels 0.44,0.88 and 11 nmol I-', respectively. Concentrations in plasma down to about 0.2 nmol I-' (50 pg ml-I) could be estimated. Percent recovery of duplicate determinations in the range 0.5-1.96 nmol I-' f SD was 99.4 f 6.0 (n = 80).
The group of compounds commonly called endocrine disruptors covers a wide range of synthetic and ... more The group of compounds commonly called endocrine disruptors covers a wide range of synthetic and natural substances able to alter the normal hormone function of wildlife and humans, consequently causing adverse health effects. Bisphenol A (BPA) and its chlorinated derivatives are some of these compounds. In this work, we propose a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine these compounds in human placental tissue samples. The method involves an extraction phase of the extracts from the samples using ethyl acetate, followed by a clean-up phase by centrifugation prior to their quantification by LC-MS/MS using an atmospheric pressure chemical ionization (APCI) interface in the negative mode. Deuterated Bisphenol A (BPA-d(16)) was used as internal standard. Found detection limits (DL) ranged from 0.2 to 0.6 ng g(-1) and quantification limits (QL) from 0.5 to 2.0 ng g(-1) for Bisphenol A and its chlorinated derivatives, while inter- and intra-day variability was under 8.1%. The method was validated using standard addition calibration and a spike recovery assay. Recovery rates for spiked samples ranged from 97% to 105%. This method was satisfactorily applied to the determination of BPA and its chlorinated derivatives in 49 placental tissue samples collected from women who live in the province of Granada (Spain).
This paper presents a comparison of three extraction techniques-ultrasound-assisted extraction, m... more This paper presents a comparison of three extraction techniques-ultrasound-assisted extraction, microwave-assisted extraction and pressurized liquid extraction-in order to evaluate their efficiency in the determination of bisphenol A and its chlorinated derivatives in sewage sludge samples. Extraction parameters for each technique were accurately optimized to achieve the highest recoveries. The selected compounds were detected and quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS), operating in negative atmospheric pressure chemical ionization (APCI) and in multiple reaction monitoring (MRM) mode. The analytes were separated in less than 6 min. BPA-d 16 was used as internal standard. Three selective, sensitive, robust and accurate analytical methods were developed. The limits of detection (LODs) of the methods ranged from 2 to 9 ng g −1 and the limits of quantification (LOQs) from 8 to 26 ng g −1 , while inter-and intra-day variability was under 6% in all cases. Given the absence of certified reference materials (CRMs), the methods were validated separately by using matrix-matched calibration and recovery assays with spiked samples. Recovery rates ranged from 97.7% to 103.1%. The sewage sludge samples used for experiments were collected from two different wastewater treatments plants (WWTPs) located in the province of Granada (South-East Spain). The statistical comparison of the methods demonstrated no statistically significant differences between the extraction techniques for the determination of BPA and chlorinated derivatives in sludge samples.
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