Y. Moliner-Martínez - Academia.edu (original) (raw)

Papers by Y. Moliner-Martínez

Research paper thumbnail of Trends for the Development of In Situ Analysis Devices

Encyclopedia of Analytical Chemistry, 2017

Research paper thumbnail of Evaluation of C18 adsorbent cartridges for sampling and derivatization of primary amines in air

Analytica Chimica Acta, 2004

Research paper thumbnail of Designing solid optical sensors for in situ passive discrimination of volatile amines based on a new one-step hydrophilic PDMS preparation

Sensors and Actuators B: Chemical, 2016

ABSTRACT

Research paper thumbnail of Adsorbent phases with nanomaterials for in-tube solid-phase microextraction coupled on-line to liquid nanochromatography

Journal of Chromatography A, 2016

Following the present trends in miniaturization, a methodology that combines on-line In-Tube Soli... more Following the present trends in miniaturization, a methodology that combines on-line In-Tube Solid-Phase Microextraction (IT-SPME) with Liquid Nanochromatography (nano-LC) and UV-vis diode array detection (DAD) was developed. This coupling was achieved by using two interconnected valves (i.e. conventional and micro-automatic valves) in the system of injection. As for IT-SPME, different materials, containing in some cases nanostructures or nanoparticles and in other cases polymeric adsorbent phases immobilized on capillary columns, were tested in order to improve extraction efficiencies of organic compounds; diclofenac was selected as the target analyte. Additionally, the transfer time of the sample between the two injection valves, as well as the lengths and the internal diameters of the capillary columns, was optimized. Under the selected conditions, the resulting IT-SPME-nano-LC-DAD method showed great potential to become a powerful analytical tool as it was successfully applied to the determination of diclofenac in pharmaceutical and water samples. For comparison purposes, IT-SPME coupled to Capillary Liquid Chromatography (Cap-LC) was used. The extraction yield of diclofenac reached near 80%, a high value for techniques that involve IT-SPME. Good accuracy (recoveries near 100%) and precision (4% RSD) were obtained.

Research paper thumbnail of Simplifying Iron Determination with o-Phenanthroline in Food Ashes Using 2-Nitrophenol as an Acid-Base Indicator

Food Analytical Methods, 2015

Research paper thumbnail of Recent advances of in-tube solid-phase microextraction

TrAC Trends in Analytical Chemistry, 2015

ABSTRACT

Research paper thumbnail of Evaluation of Superparamagnetic Silica Nanoparticles for Extraction of Triazines in Magnetic in-Tube Solid Phase Microextraction Coupled to Capillary Liquid Chromatography

Nanomaterials, 2014

ABSTRACT The use of magnetic nanomaterials for analytical applications has increased in the recen... more ABSTRACT The use of magnetic nanomaterials for analytical applications has increased in the recent years. In particular, magnetic nanomaterials have shown great potential as adsorbent phase in several extraction procedures due to the significant advantages over the conventional methods. In the present work, the influence of magnetic forces over the extraction efficiency of triazines using superparamagnetic silica nanoparticles (NPs) in magnetic in tube solid phase microextraction (Magnetic-IT-SPME) coupled to CapLC has been evaluated. Atrazine, terbutylazine and simazine has been selected as target analytes. The superparamagnetic silica nanomaterial (SiO 2 -Fe 3 O 4) deposited onto the surface of a capillary column gave rise to a magnetic extraction phase for IT-SPME that provided a enhancemment of the extraction efficiency for triazines. This improvement is based on two phenomena, the superparamegnetic behavior of Fe 3 O 4 NPs and the diamagnetic repulsions that take place in a microfluidic device such a capillary column. A systematic study of analytes adsorption and desorption was conducted as function of the magnetic field and the relationship with triazines magnetic susceptibility. The positive influence of magnetism on OPEN ACCESS Nanomaterials 2014, 4 243 the extraction procedure was demonstrated. The analytical characteristics of the optimized procedure were established and the method was applied to the determination of the target analytes in water samples with satisfactory results. When coupling Magnetic-IT-SPME with CapLC, improved adsorption efficiencies (60%–63%) were achieved compared with conventional adsorption materials (0.8%–3%).

Research paper thumbnail of Selective and sentivive method based on capillary liquid chromatography with in-tube solid phase microextraction for determination of monochloramine in water

Journal of chromatography. A, Jan 3, 2015

Due to the difficulties of working with chloramines, a critical examination of monochloramine sta... more Due to the difficulties of working with chloramines, a critical examination of monochloramine standard preparation has been performed in order to select the best synthesis conditions. The analyte has been determined by in-tube solid phase extraction coupled to capillary liquid chromatography with UV detection (IT-SPME Capillary LC DAD). Potential factors affecting the response of monochloramine such as the pH of mobile phase and the volume of sample processed by IT-SPME Capillary LC DAD have been investigated and optimized. According to the results of the study, 0.1mL or 4.0mL of sample at neutral pH were loaded in the chromatographic system. A sensitive and selective method has been developed for the determination of monochloramine in water. Validation of the method has been performed. The linear range was 0.09-5mg/L with linear regression coefficients (R(2)) greater than 0.995. Method reproducibility expressed as relative standard deviation (RSD, %), was lower than 15%. The limits...

Research paper thumbnail of Polydimethylsiloxane composites containing 1,2-naphtoquinone 4-sulphonate as unique dispositive for estimation of casein in effluents from dairy industries

Analytica Chimica Acta, 2015

A unique dispositive to determine casein which is the most abundant protein in dairy sewages has ... more A unique dispositive to determine casein which is the most abundant protein in dairy sewages has been proposed. In this sensing technology, the derivatization reagent 1,2-naphtoquininone 4-sulphonate (NQS) is embedded into a polydimethylsiloxane-tetraethylortosilicate-SiO2 nanoparticles composite (PDMS-TEOS-SiO2NPs). When the composite is immersed into the samples, casein is extracted from the solution and derivatized inside the PDMS matrix after 10min at 100°C. The sensing support changes its color from yellow to orange depending on the casein concentration. Quantitative analysis can be carried out by measuring the absorbance with a reflection probe or by image-processing tool (GIMP). This sensor provides good sensitivity and precision (RSD% <12%). The method validation has been done by applying the biocinchoninic acid method (BCA). Moreover, semiquatitative analysis of casein can be performed by visual observation. Taking into account the advantages of small size, rapidity, simplicity, good stability and high compatibility in aqueous solution, this sensor is expected to have potential practical applications for in-situ determination of casein. Finally the method has been applied to analyze effluents from dairy industries.

Research paper thumbnail of Development of a polydimethylsiloxane–thymol/nitroprusside composite based sensor involving thymol derivatization for ammonium monitoring in water samples

Science of The Total Environment, 2015

ABSTRACT This report describes a polydimethylsiloxane (PDMS)-thymol/nitroprusside delivery compos... more ABSTRACT This report describes a polydimethylsiloxane (PDMS)-thymol/nitroprusside delivery composite sensor for direct monitoring of ammonium in environmental water samples. The sensor is based on a PDMS support that contains the Berthelot's reaction reagents. To prepare the PDMS-thymol/nitroprusside composite discs, thymol and nitroprusside have been encapsulated in the PDMS matrix, forming a reagent release support which significantly simplifies the analytical measurements, since it avoids the need to prepare derivatizing reagents and sample handling is reduced to the sampling step. When, the PDMS-thymol/nitroprusside composite was introduced in water samples spontaneous release of the chromophore and catalyst was produced, and the derivatization reaction took place to form the indothymol blue. Thus, qualitative analysis of NH4(+) could be carried out by visual inspection, but also, it can be quantified by measuring the absorbance at 690nm. These portable devices provided good sensitivity (LOD<0.4mgL(-1)) and reproducibility (RSD <10%) for the rapid detection of ammonium. The PDMS-NH4(+) sensor has been successfully applied to determine ammonium in water samples and in the aqueous extracts of particulate matter PM10 samples. Moreover, the reliability of the method for qualitative analysis has been demonstrated. Finally, the advantages of the PDMS-NH4(+) sensor have been examined by comparing some analytical and complementary characteristics with the properties of well-established ammonium determination methods.

Research paper thumbnail of Combining poly (dimethyldiphenylsiloxane) and nitrile phases for improving the separation and quantitation of benzalkonium chloride homologues: In-tube solid phase microextraction–capillary liquid chromatography–diode array detection-mass spectrometry for analyzing industrial samples

Research paper thumbnail of Analysis of 18 perfluorinated compounds in river waters: Comparison of high performance liquid chromatography–tandem mass spectrometry, ultra-high-performance liquid chromatography–tandem mass spectrometry and capillary liquid chromatography–mass spectrometry

Research paper thumbnail of Determination of carbonyl compounds in particulate matter PM2.5 by in-tube solid-phase microextraction coupled to capillary liquid chromatography/mass spectrometry

Talanta, 2013

In this paper, a new procedure based on in-tube solid phase microextraction (IT-SPME)-capillary l... more In this paper, a new procedure based on in-tube solid phase microextraction (IT-SPME)-capillary liquid chromatography hyphenated to mass spectrometry detection by using microelectrospray ionisation (CapLC-MS), has been reported. The device was proposed to quantify 12 carbonyl compounds (10 aliphatic aldehydes, an unsaturated aldehyde and a ketone) derivatized with 2,4-dinitrophenylhidrazine (DNPH) reagent in aqueous extracts of PM2.5. This methodology involves the on-line preconcentration of DNPH-carbonyl compounds derivatives coupled to the CapLC-MS system, efficiently providing appropriate sensitivity for the determination of the target analytes. Detection limits for the analytes ranged between 0.9 and 8.2 ng L(-1). These values represent a remarkable improvement over the existing methods since PM2.5 analysis can be carried out avoiding off-line preconcentration steps. The procedure is also proved useful for analysing water samples. Under the optimised conditions, IT-SPME-CapLC-MS shows satisfactory recovery values (80-90%) for spiked samples.

Research paper thumbnail of Determination of Ammonia in Water Samples

Handbook of Water Analysis, Third Edition, 2013

Research paper thumbnail of Influence of water sample storage protocols in chemiluminescence detection of trace elements

Talanta, 2003

This paper shows the influence of different sample storage protocols, on the chemiluminescence si... more This paper shows the influence of different sample storage protocols, on the chemiluminescence signal of some metal ions. The storage protocols studied were: acid addition (HCl or HNO 3 ) and no reagent addition to filtered and refrigerated (T0/4 8C) samples. Light emission was produced for the chemiluminescence reaction between luminol and hydrogen peroxide in buffer carbonate conditions (pH 10.8) catalysed by Cr(III), Co(II) and Cu(II). Batch and/or flow modes in different conditions were tested. Fe(II), Fe(III), Ni(II) and Mn(II) did not give chemiluminescence in the studied conditions. A parallel study of sensitivity and selectivity was performed. Then the presence or absence of the masking agent EDTA, added to samples or used in the carrier stream, is assayed. If the samples are acidified with HNO 3 , a previous neutralisation is needed using batch mode. The determination of Cr(III) is independent of storage protocol by flow injection (FI) method; however, the determination of Co(II) or Cu(II) or total determination of three metals requires the conditioning of standards. Detection limits achieved are ranged between 0.5 and 2 mg l (1 . For batch mode, detection limits are better for unacidified samples and worse for carbonate-neutralised samples. The influence of storage protocols was validated using standard metal mixtures and calibration solutions. The use of standard reference material (SRM# 1640) (Trace elements in natural water) corroborates the previous statements and validates the accuracy of the different approaches underlined. This paper demonstrates that it is possible to determine Cr(III) selectively in natural waters. #

Research paper thumbnail of Analysis of polar triazines and degradation products in waters by in-tube solid-phase microextraction and capillary chromatography: an environmentally friendly method

Analytical and Bioanalytical Chemistry, 2014

This paper describes a new method for the determination of polar triazines, including some degrad... more This paper describes a new method for the determination of polar triazines, including some degradation products, which combines online in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography with UV-diode array detection (DAD). Different extractive coatings have been evaluated for IT-SPME, a capillary column with a polydimethylsiloxane (PDMS) coating, and the same coating modified with carboxylated single-wall carbon nanotubes (c-SWCNTs) and carboxylated multiwall carbon nanotubes (c-MWCNTs). On the basis of the results obtained, a new method is presented for the identification and determination of triazines in water samples. A careful selection of the eluent composition provides the required selectivity and sensitivity for the quantification of the target analytes, even those highly polar (log K ow ≤ 2.3). The proposed conditions have been successfully used for the quantitation of the analytes in the 0.25-50.0 μg L(-1) range. The limits of detection (LODs) are in the 0.02-0.1 μg L(-1) range, and the intraday and interday relative standard deviation (RSD) coefficients are ≤9 and ≤17 %, respectively. The reliability of the described method has been tested by analyzing several real water samples. The proposed method can be considered an environmentally friendly and cost-effective alternative for routine monitoring of triazines and their degradation products in waters.

Research paper thumbnail of Carbon nanostructures as sorbent materials in analytical processes

TrAC Trends in Analytical Chemistry, 2008

Over time, new materials have been used and incorporated in a wide variety of analytical processe... more Over time, new materials have been used and incorporated in a wide variety of analytical processes. This century, technology has produced novel nanomaterials with unique properties whose use has increased in analytical sciences. Carbon nanostructures are among these new nanomaterials. This overview reports on the use of carbon nanomaterials, mainly fullerenes and carbon nanotubes, as sorbents in the analytical process. After a brief description of their main characteristics, we present their use in the development of selective membranes. Next, we describe their role as sorbent materials and stationary phases in chromatography and provide relevant examples. We also comment on the presence of carbon nanoparticles as components of electrophoretic buffers to improve both resolution and sensitivity of separations. Finally, we briefly describe other applications in which the sorption capabilities of carbon nanostructures play a role.

Research paper thumbnail of Rapid analysis of effluents generated by the dairy industry for fat determination by preconcentration in nylon membranes and attenuated total reflectance infrared spectroscopy measurement

Talanta, 2014

This paper describes a new approach for the determination of fat in the effluents generated by th... more This paper describes a new approach for the determination of fat in the effluents generated by the dairy industry which is based on the retention of fat in nylon membranes and measurement of the absorbances on the membrane surface by ATR-IR spectroscopy. Different options have been evaluated for retaining fat in the membranes using milk samples of different origin and fat content. Based on the results obtained, a method is proposed for the determination of fat in effluents which involves the filtration of 1 mL of the samples through 0.45 µm nylon membranes of 13 mm diameter. The fat content is then determined by measuring the absorbance of band at 1745 cm(-1). The proposed method can be used for the direct estimation of fat at concentrations in the 2-12 mg/L interval with adequate reproducibility. The intraday precision, expressed as coefficients of variation CVs, were ≤ 11%, whereas the interday CVs were ≤ 20%. The method shows a good tolerance towards conditions typically found in the effluents generated by the dairy industry. The most relevant features of the proposed method are simplicity and speed as the samples can be characterized in a few minutes. Sample preparation does not involve either additional instrumentation (such as pumps or vacuum equipment) or organic solvents or other chemicals. Therefore, the proposed method can be considered a rapid, simple and cost-effective alternative to gravimetric methods for controlling fat content in these effluents during production or cleaning processes.

Research paper thumbnail of Detector supports: application to aliphatic amines in wastewater

Talanta, 2005

Solid support assisted derivatization coupled to diffuse reflectance spectroscopy (DRS) was propo... more Solid support assisted derivatization coupled to diffuse reflectance spectroscopy (DRS) was proposed and proved useful for the detection and quantification of aliphatic amines in water as an example. Dabsyl chloride (DBS), ninhydrin and sodium 1,2-naphtoquinone 4-sulphonate (NQS) were assayed as derivatization reagents. C 18 and SDB-XC disks and C 18 cartridges were tested for amine retention and after that derivatization. The decrease of the orange colour of dabsyl chloride on SBD-XC disks produced by the formation of its derivative with methylamine in the support (10 min at 100 • C) allowed the selective determination of the amine at concentration level equal or higher than 0.5 mg L −1 . Ninhydrin can be used for methylamine, ethylamine, propylamine, butylamine and pentylamine (between 5 and 15 mg L −1 ) by measuring the diffuse reflectance produced by the brown derivative formed in C 18 extraction disks after 15 min at 100 • C. NQS and C 18 SPE columns can be also employed to estimate amines, but the detection limits were higher than those provided by DBS and Ninhydrin, around 10 mg L −1 . As an example, found concentration of methylamine or total amines (expressed as -NH 2 -N mg L −1 ) in a wastewater sample is given employing dabsyl chloride or ninhydrin reagents, respectively with satisfactory results.

Research paper thumbnail of More about sampling and estimation of mercaptans in air samples

Talanta, 2013

Several strategies have been developed for sampling and determination of volatile thiols. The sel... more Several strategies have been developed for sampling and determination of volatile thiols. The selectivity and sensitivity of the proposed methodologies are achieved by using a specific derivatizing reagent. The different procedures assayed are based on air sampling followed by derivatization of the analytes with OPA and isoleucine in alkaline solution. The derivatization products are separated and determined by liquid chromatography and fluorescence detection. To start, the derivatization conditions and stability of the derivates have been studied in order to establish the storage conditions. In general, the strategies studied consisted on trapping and detivatization the thiol compound on different support; a solution (Impinger) or sorbent (C₁₈ cartridges or glass fiber filter). The analytical properties of the different strategies have been obtained and compared. Procedures are recommended upon specific situations.

Research paper thumbnail of Trends for the Development of In Situ Analysis Devices

Encyclopedia of Analytical Chemistry, 2017

Research paper thumbnail of Evaluation of C18 adsorbent cartridges for sampling and derivatization of primary amines in air

Analytica Chimica Acta, 2004

Research paper thumbnail of Designing solid optical sensors for in situ passive discrimination of volatile amines based on a new one-step hydrophilic PDMS preparation

Sensors and Actuators B: Chemical, 2016

ABSTRACT

Research paper thumbnail of Adsorbent phases with nanomaterials for in-tube solid-phase microextraction coupled on-line to liquid nanochromatography

Journal of Chromatography A, 2016

Following the present trends in miniaturization, a methodology that combines on-line In-Tube Soli... more Following the present trends in miniaturization, a methodology that combines on-line In-Tube Solid-Phase Microextraction (IT-SPME) with Liquid Nanochromatography (nano-LC) and UV-vis diode array detection (DAD) was developed. This coupling was achieved by using two interconnected valves (i.e. conventional and micro-automatic valves) in the system of injection. As for IT-SPME, different materials, containing in some cases nanostructures or nanoparticles and in other cases polymeric adsorbent phases immobilized on capillary columns, were tested in order to improve extraction efficiencies of organic compounds; diclofenac was selected as the target analyte. Additionally, the transfer time of the sample between the two injection valves, as well as the lengths and the internal diameters of the capillary columns, was optimized. Under the selected conditions, the resulting IT-SPME-nano-LC-DAD method showed great potential to become a powerful analytical tool as it was successfully applied to the determination of diclofenac in pharmaceutical and water samples. For comparison purposes, IT-SPME coupled to Capillary Liquid Chromatography (Cap-LC) was used. The extraction yield of diclofenac reached near 80%, a high value for techniques that involve IT-SPME. Good accuracy (recoveries near 100%) and precision (4% RSD) were obtained.

Research paper thumbnail of Simplifying Iron Determination with o-Phenanthroline in Food Ashes Using 2-Nitrophenol as an Acid-Base Indicator

Food Analytical Methods, 2015

Research paper thumbnail of Recent advances of in-tube solid-phase microextraction

TrAC Trends in Analytical Chemistry, 2015

ABSTRACT

Research paper thumbnail of Evaluation of Superparamagnetic Silica Nanoparticles for Extraction of Triazines in Magnetic in-Tube Solid Phase Microextraction Coupled to Capillary Liquid Chromatography

Nanomaterials, 2014

ABSTRACT The use of magnetic nanomaterials for analytical applications has increased in the recen... more ABSTRACT The use of magnetic nanomaterials for analytical applications has increased in the recent years. In particular, magnetic nanomaterials have shown great potential as adsorbent phase in several extraction procedures due to the significant advantages over the conventional methods. In the present work, the influence of magnetic forces over the extraction efficiency of triazines using superparamagnetic silica nanoparticles (NPs) in magnetic in tube solid phase microextraction (Magnetic-IT-SPME) coupled to CapLC has been evaluated. Atrazine, terbutylazine and simazine has been selected as target analytes. The superparamagnetic silica nanomaterial (SiO 2 -Fe 3 O 4) deposited onto the surface of a capillary column gave rise to a magnetic extraction phase for IT-SPME that provided a enhancemment of the extraction efficiency for triazines. This improvement is based on two phenomena, the superparamegnetic behavior of Fe 3 O 4 NPs and the diamagnetic repulsions that take place in a microfluidic device such a capillary column. A systematic study of analytes adsorption and desorption was conducted as function of the magnetic field and the relationship with triazines magnetic susceptibility. The positive influence of magnetism on OPEN ACCESS Nanomaterials 2014, 4 243 the extraction procedure was demonstrated. The analytical characteristics of the optimized procedure were established and the method was applied to the determination of the target analytes in water samples with satisfactory results. When coupling Magnetic-IT-SPME with CapLC, improved adsorption efficiencies (60%–63%) were achieved compared with conventional adsorption materials (0.8%–3%).

Research paper thumbnail of Selective and sentivive method based on capillary liquid chromatography with in-tube solid phase microextraction for determination of monochloramine in water

Journal of chromatography. A, Jan 3, 2015

Due to the difficulties of working with chloramines, a critical examination of monochloramine sta... more Due to the difficulties of working with chloramines, a critical examination of monochloramine standard preparation has been performed in order to select the best synthesis conditions. The analyte has been determined by in-tube solid phase extraction coupled to capillary liquid chromatography with UV detection (IT-SPME Capillary LC DAD). Potential factors affecting the response of monochloramine such as the pH of mobile phase and the volume of sample processed by IT-SPME Capillary LC DAD have been investigated and optimized. According to the results of the study, 0.1mL or 4.0mL of sample at neutral pH were loaded in the chromatographic system. A sensitive and selective method has been developed for the determination of monochloramine in water. Validation of the method has been performed. The linear range was 0.09-5mg/L with linear regression coefficients (R(2)) greater than 0.995. Method reproducibility expressed as relative standard deviation (RSD, %), was lower than 15%. The limits...

Research paper thumbnail of Polydimethylsiloxane composites containing 1,2-naphtoquinone 4-sulphonate as unique dispositive for estimation of casein in effluents from dairy industries

Analytica Chimica Acta, 2015

A unique dispositive to determine casein which is the most abundant protein in dairy sewages has ... more A unique dispositive to determine casein which is the most abundant protein in dairy sewages has been proposed. In this sensing technology, the derivatization reagent 1,2-naphtoquininone 4-sulphonate (NQS) is embedded into a polydimethylsiloxane-tetraethylortosilicate-SiO2 nanoparticles composite (PDMS-TEOS-SiO2NPs). When the composite is immersed into the samples, casein is extracted from the solution and derivatized inside the PDMS matrix after 10min at 100°C. The sensing support changes its color from yellow to orange depending on the casein concentration. Quantitative analysis can be carried out by measuring the absorbance with a reflection probe or by image-processing tool (GIMP). This sensor provides good sensitivity and precision (RSD% <12%). The method validation has been done by applying the biocinchoninic acid method (BCA). Moreover, semiquatitative analysis of casein can be performed by visual observation. Taking into account the advantages of small size, rapidity, simplicity, good stability and high compatibility in aqueous solution, this sensor is expected to have potential practical applications for in-situ determination of casein. Finally the method has been applied to analyze effluents from dairy industries.

Research paper thumbnail of Development of a polydimethylsiloxane–thymol/nitroprusside composite based sensor involving thymol derivatization for ammonium monitoring in water samples

Science of The Total Environment, 2015

ABSTRACT This report describes a polydimethylsiloxane (PDMS)-thymol/nitroprusside delivery compos... more ABSTRACT This report describes a polydimethylsiloxane (PDMS)-thymol/nitroprusside delivery composite sensor for direct monitoring of ammonium in environmental water samples. The sensor is based on a PDMS support that contains the Berthelot's reaction reagents. To prepare the PDMS-thymol/nitroprusside composite discs, thymol and nitroprusside have been encapsulated in the PDMS matrix, forming a reagent release support which significantly simplifies the analytical measurements, since it avoids the need to prepare derivatizing reagents and sample handling is reduced to the sampling step. When, the PDMS-thymol/nitroprusside composite was introduced in water samples spontaneous release of the chromophore and catalyst was produced, and the derivatization reaction took place to form the indothymol blue. Thus, qualitative analysis of NH4(+) could be carried out by visual inspection, but also, it can be quantified by measuring the absorbance at 690nm. These portable devices provided good sensitivity (LOD<0.4mgL(-1)) and reproducibility (RSD <10%) for the rapid detection of ammonium. The PDMS-NH4(+) sensor has been successfully applied to determine ammonium in water samples and in the aqueous extracts of particulate matter PM10 samples. Moreover, the reliability of the method for qualitative analysis has been demonstrated. Finally, the advantages of the PDMS-NH4(+) sensor have been examined by comparing some analytical and complementary characteristics with the properties of well-established ammonium determination methods.

Research paper thumbnail of Combining poly (dimethyldiphenylsiloxane) and nitrile phases for improving the separation and quantitation of benzalkonium chloride homologues: In-tube solid phase microextraction–capillary liquid chromatography–diode array detection-mass spectrometry for analyzing industrial samples

Research paper thumbnail of Analysis of 18 perfluorinated compounds in river waters: Comparison of high performance liquid chromatography–tandem mass spectrometry, ultra-high-performance liquid chromatography–tandem mass spectrometry and capillary liquid chromatography–mass spectrometry

Research paper thumbnail of Determination of carbonyl compounds in particulate matter PM2.5 by in-tube solid-phase microextraction coupled to capillary liquid chromatography/mass spectrometry

Talanta, 2013

In this paper, a new procedure based on in-tube solid phase microextraction (IT-SPME)-capillary l... more In this paper, a new procedure based on in-tube solid phase microextraction (IT-SPME)-capillary liquid chromatography hyphenated to mass spectrometry detection by using microelectrospray ionisation (CapLC-MS), has been reported. The device was proposed to quantify 12 carbonyl compounds (10 aliphatic aldehydes, an unsaturated aldehyde and a ketone) derivatized with 2,4-dinitrophenylhidrazine (DNPH) reagent in aqueous extracts of PM2.5. This methodology involves the on-line preconcentration of DNPH-carbonyl compounds derivatives coupled to the CapLC-MS system, efficiently providing appropriate sensitivity for the determination of the target analytes. Detection limits for the analytes ranged between 0.9 and 8.2 ng L(-1). These values represent a remarkable improvement over the existing methods since PM2.5 analysis can be carried out avoiding off-line preconcentration steps. The procedure is also proved useful for analysing water samples. Under the optimised conditions, IT-SPME-CapLC-MS shows satisfactory recovery values (80-90%) for spiked samples.

Research paper thumbnail of Determination of Ammonia in Water Samples

Handbook of Water Analysis, Third Edition, 2013

Research paper thumbnail of Influence of water sample storage protocols in chemiluminescence detection of trace elements

Talanta, 2003

This paper shows the influence of different sample storage protocols, on the chemiluminescence si... more This paper shows the influence of different sample storage protocols, on the chemiluminescence signal of some metal ions. The storage protocols studied were: acid addition (HCl or HNO 3 ) and no reagent addition to filtered and refrigerated (T0/4 8C) samples. Light emission was produced for the chemiluminescence reaction between luminol and hydrogen peroxide in buffer carbonate conditions (pH 10.8) catalysed by Cr(III), Co(II) and Cu(II). Batch and/or flow modes in different conditions were tested. Fe(II), Fe(III), Ni(II) and Mn(II) did not give chemiluminescence in the studied conditions. A parallel study of sensitivity and selectivity was performed. Then the presence or absence of the masking agent EDTA, added to samples or used in the carrier stream, is assayed. If the samples are acidified with HNO 3 , a previous neutralisation is needed using batch mode. The determination of Cr(III) is independent of storage protocol by flow injection (FI) method; however, the determination of Co(II) or Cu(II) or total determination of three metals requires the conditioning of standards. Detection limits achieved are ranged between 0.5 and 2 mg l (1 . For batch mode, detection limits are better for unacidified samples and worse for carbonate-neutralised samples. The influence of storage protocols was validated using standard metal mixtures and calibration solutions. The use of standard reference material (SRM# 1640) (Trace elements in natural water) corroborates the previous statements and validates the accuracy of the different approaches underlined. This paper demonstrates that it is possible to determine Cr(III) selectively in natural waters. #

Research paper thumbnail of Analysis of polar triazines and degradation products in waters by in-tube solid-phase microextraction and capillary chromatography: an environmentally friendly method

Analytical and Bioanalytical Chemistry, 2014

This paper describes a new method for the determination of polar triazines, including some degrad... more This paper describes a new method for the determination of polar triazines, including some degradation products, which combines online in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography with UV-diode array detection (DAD). Different extractive coatings have been evaluated for IT-SPME, a capillary column with a polydimethylsiloxane (PDMS) coating, and the same coating modified with carboxylated single-wall carbon nanotubes (c-SWCNTs) and carboxylated multiwall carbon nanotubes (c-MWCNTs). On the basis of the results obtained, a new method is presented for the identification and determination of triazines in water samples. A careful selection of the eluent composition provides the required selectivity and sensitivity for the quantification of the target analytes, even those highly polar (log K ow ≤ 2.3). The proposed conditions have been successfully used for the quantitation of the analytes in the 0.25-50.0 μg L(-1) range. The limits of detection (LODs) are in the 0.02-0.1 μg L(-1) range, and the intraday and interday relative standard deviation (RSD) coefficients are ≤9 and ≤17 %, respectively. The reliability of the described method has been tested by analyzing several real water samples. The proposed method can be considered an environmentally friendly and cost-effective alternative for routine monitoring of triazines and their degradation products in waters.

Research paper thumbnail of Carbon nanostructures as sorbent materials in analytical processes

TrAC Trends in Analytical Chemistry, 2008

Over time, new materials have been used and incorporated in a wide variety of analytical processe... more Over time, new materials have been used and incorporated in a wide variety of analytical processes. This century, technology has produced novel nanomaterials with unique properties whose use has increased in analytical sciences. Carbon nanostructures are among these new nanomaterials. This overview reports on the use of carbon nanomaterials, mainly fullerenes and carbon nanotubes, as sorbents in the analytical process. After a brief description of their main characteristics, we present their use in the development of selective membranes. Next, we describe their role as sorbent materials and stationary phases in chromatography and provide relevant examples. We also comment on the presence of carbon nanoparticles as components of electrophoretic buffers to improve both resolution and sensitivity of separations. Finally, we briefly describe other applications in which the sorption capabilities of carbon nanostructures play a role.

Research paper thumbnail of Rapid analysis of effluents generated by the dairy industry for fat determination by preconcentration in nylon membranes and attenuated total reflectance infrared spectroscopy measurement

Talanta, 2014

This paper describes a new approach for the determination of fat in the effluents generated by th... more This paper describes a new approach for the determination of fat in the effluents generated by the dairy industry which is based on the retention of fat in nylon membranes and measurement of the absorbances on the membrane surface by ATR-IR spectroscopy. Different options have been evaluated for retaining fat in the membranes using milk samples of different origin and fat content. Based on the results obtained, a method is proposed for the determination of fat in effluents which involves the filtration of 1 mL of the samples through 0.45 µm nylon membranes of 13 mm diameter. The fat content is then determined by measuring the absorbance of band at 1745 cm(-1). The proposed method can be used for the direct estimation of fat at concentrations in the 2-12 mg/L interval with adequate reproducibility. The intraday precision, expressed as coefficients of variation CVs, were ≤ 11%, whereas the interday CVs were ≤ 20%. The method shows a good tolerance towards conditions typically found in the effluents generated by the dairy industry. The most relevant features of the proposed method are simplicity and speed as the samples can be characterized in a few minutes. Sample preparation does not involve either additional instrumentation (such as pumps or vacuum equipment) or organic solvents or other chemicals. Therefore, the proposed method can be considered a rapid, simple and cost-effective alternative to gravimetric methods for controlling fat content in these effluents during production or cleaning processes.

Research paper thumbnail of Detector supports: application to aliphatic amines in wastewater

Talanta, 2005

Solid support assisted derivatization coupled to diffuse reflectance spectroscopy (DRS) was propo... more Solid support assisted derivatization coupled to diffuse reflectance spectroscopy (DRS) was proposed and proved useful for the detection and quantification of aliphatic amines in water as an example. Dabsyl chloride (DBS), ninhydrin and sodium 1,2-naphtoquinone 4-sulphonate (NQS) were assayed as derivatization reagents. C 18 and SDB-XC disks and C 18 cartridges were tested for amine retention and after that derivatization. The decrease of the orange colour of dabsyl chloride on SBD-XC disks produced by the formation of its derivative with methylamine in the support (10 min at 100 • C) allowed the selective determination of the amine at concentration level equal or higher than 0.5 mg L −1 . Ninhydrin can be used for methylamine, ethylamine, propylamine, butylamine and pentylamine (between 5 and 15 mg L −1 ) by measuring the diffuse reflectance produced by the brown derivative formed in C 18 extraction disks after 15 min at 100 • C. NQS and C 18 SPE columns can be also employed to estimate amines, but the detection limits were higher than those provided by DBS and Ninhydrin, around 10 mg L −1 . As an example, found concentration of methylamine or total amines (expressed as -NH 2 -N mg L −1 ) in a wastewater sample is given employing dabsyl chloride or ninhydrin reagents, respectively with satisfactory results.

Research paper thumbnail of More about sampling and estimation of mercaptans in air samples

Talanta, 2013

Several strategies have been developed for sampling and determination of volatile thiols. The sel... more Several strategies have been developed for sampling and determination of volatile thiols. The selectivity and sensitivity of the proposed methodologies are achieved by using a specific derivatizing reagent. The different procedures assayed are based on air sampling followed by derivatization of the analytes with OPA and isoleucine in alkaline solution. The derivatization products are separated and determined by liquid chromatography and fluorescence detection. To start, the derivatization conditions and stability of the derivates have been studied in order to establish the storage conditions. In general, the strategies studied consisted on trapping and detivatization the thiol compound on different support; a solution (Impinger) or sorbent (C₁₈ cartridges or glass fiber filter). The analytical properties of the different strategies have been obtained and compared. Procedures are recommended upon specific situations.