Manuel Algarra - Academia.edu (original) (raw)

Papers by Manuel Algarra

Chemosphere, 2005

The potential of removing nickel and copper from industrial electroplating wastewaters by using m... more The potential of removing nickel and copper from industrial electroplating wastewaters by using mesoporous materials with MCM-41 type structure functionalised with different ratios of aminopropyl groups, namely Na50, Na25 and Na5, were evaluated. The synthesised solids sorbents obtained were characterised by X-ray diffraction, elemental chemical analysis and IR spectroscopy. In preliminary experiments, studies were carried out to determine the optimal experimental conditions for the retention of heavy ions. Effects of concentration, optimal pH, interference with humic substances and other metals were studied for Na5, which showed the best capacity of absorption determined by the corresponding isotherm. This material has a greater selectivity against sodium, indicating that ionic strength does not affect the extraction. Results of an application of this material to remove nickel and copper in synthetic and real industrial wastewater samples from an electrochemical industry area are s...

This work reports two methods developed for the separation and determination of the enantiomers o... more This work reports two methods developed for the separation and determination of the enantiomers of the new alkaloid malacitanine (MLC) and the determination of the enantiomeric purity in mixtures. First, the isomers were separated using a Chirex 3020 (250 mm × 4.6 mm, 5 m) chiral column with a mobile phase of cyclohexane-1,2-dichloroethaneethanol-trifluoroacetic acid (64:30:6:0.6, v/v/v/v) at a flow rate of 1 mL/min and fluorimetric detection. Obtained retention times were 12.4 and 15.9 min (+ and −) with a resolution Rs of 1.13. Relative standard deviations (RSDs) were 2.5 and 2.4% at the 0.5-g level (four determinations). Second, a nonenantioselective procedure for the determination of enantiomeric purity of MLC using a Lichrospher R Si-60 (250 mm × 5 mm, 5 m) normal phase with a mobile phase of 100% ethanol at a flow rate of 0.9 mL/min coupled to two detectors in series, fluorimetric and polarimetric. RSD of 3.3% was obtained. Calculated enantiomeric purity by chiral chromatography gave 48.6% (−)-MLC in the near racemic product. Using polarimetric signal of the nonseparated enantiomers and comparing the slopes of the calibration curves (enantiomers) from the racemic product gave 47.8% (−)-MLC content. A study of accuracy of (−)-MLC gave recoveries from 98.3 to 100.7%.

Magnesium is an essential mineral in human metabolism, and is the second most abundant intracellu... more Magnesium is an essential mineral in human metabolism, and is the second most abundant intracellular cation and the fourth most abundant in the human body. Magnesium has a large variety of biological functions, including being a cofactor for over 300 enzymes, mainly involving phosphorylation of proteins and nucleic acids. Low levels of magnesium in the body can develop during different illnesses, such as diabetes (type 2), metabolic syndrome, cardiac arrhythmias, and muscular constriction. The present review shows the advances in analytical chemistry based on sensor systems to quantify the concentration of magnesium in different biological samples, plasma, serum, or urine, that are relevant to human health.

Fenton's reaction is often used to decompose stable substances in wastewater. In this study, expe... more Fenton's reaction is often used to decompose stable substances in wastewater. In this study, experiments based on the effect of porous phosphate heterostructures as catalyst sorbent of Fe 2+ synthesised by different procedures were planned. The examined PPH-Fe/H 2 O 2 as oxidant in a heterogeneous process under mild conditions at pH 5 was found to be very efficient for discoloration of a simulated wastewater containing 50 mg L −1 of a commercial azo dye (Reactive Black 5) reaching 95% of decolourization. Under the described conditions total visual decolourization was achieved after 360 min. This study can provide a simple, effective, and economic system ideal for the treatment of toxic and nonbiodegradable azo dyes.

The effects of cyclodextrins and TX-100 micelles on the fluorescent properties of 2-(dimethylamin... more The effects of cyclodextrins and TX-100 micelles on the fluorescent properties of 2-(dimethylamino)fluorene (DAF) were studied. The photophysical properties of DAF in the micelle aggregates and cyclodextrins were used to explain how the cavity might affect the dynamics of intramolecular charge transfer and the twisting of the molecule. Results obtained show that a-, band c-cyclodextrins interact in a different way with DAF and different values of quantum yield, lifetimes and absorption and emission wavelength were obtained. Because a small interior cavity size, a-cyclodextrin do not show interaction with DAF. Quenching studies demonstrated that in Triton X-100 micelles, DAF molecules migrated to the non polar region.

Adsorption of uranyl ions onto kaolinite, montmorillonite, humic acid and composite clay material... more Adsorption of uranyl ions onto kaolinite, montmorillonite, humic acid and composite clay material (both clays and humic acid) was studied by measuring the system response to clay suspensions (pre-equilibrated with or without uranyl) and to perturbations of the solution chemistry. Adsorption behavior of selected materials under the frame of batch experiments was tested at high uranyl concentrations (6-1170 μg/mL; 2.5 × 10 −2 to 4.9 μM), whereas that under flow through continuous stirred reactor experiments was tested at low concentrations (1.00 × 10 −4 to 1.18 × 10 −4 M). Both experiments were developed at pH 4.5 and ionic strength 0.2 mM. The adsorption experiments follow a Langmuir isotherm model with a good correlation coefficient (R 2 N 0.97). The calculated amount of adsorbed and desorbed uranyl was carried out by numeric integration of the experimental data, whereas the desorption rates were determined from the breakthrough curve experiments. Kaolinite with highly disordered structure adsorbed less uranyl (3.86 × 10 −6 mol/g) than well-ordered kaolinite (1.76 × 10 −5 mol/g). Higher amount of uranyl was adsorbed by montmorillonite (3.60 × 10 −5 mol/g) and only half of adsorbed amount was desorbed (1.85 × 10 −5 mol/g). The molecular interactions between kaolinite, montmorillonite, humic acid, composite material and saturated uranyl ion solutions were studied by molecular fluorescence, infrared and X-ray photoelectron spectroscopy. The Stern-Volmer constant obtained for montmorillonite (2.6 × 10 3 M −1 ) is higher than for kaolinite (0.3 × 10 3 M −1 ). Molecular vibrations of Si\O stretching and Al\OH bending related to hydroxylated groups (`SiOH or`AlOH) of kaolinite and montmorillonite show structural changes when uranyl ions are adsorbed. X-ray photoelectron spectroscopy shows that the U 4f 7/2 core level signals occur at 380.5 eV in either kaolinite or montmorillonite that resulted from the interaction of aluminol surface sites with the (UO 2 ) 3 (OH) 5 + .

A newly synthesized family of materials prepared with surfactant as organic template were tested ... more A newly synthesized family of materials prepared with surfactant as organic template were tested for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water, using pyrene (Pyr) and benzo[a]pyrene (B[a]P) as PAHs representatives. Particular attention was paid to the evaluation of the recovery factors with dichloromethane as eluent in order to estimate their potential as adsorbing solid phases for PAH remediation or analysis. Eleven lamellar MCM-50 type materials incorporating n-alkyl-(n ¼ 12, 16, 18) trimethylammonium bromide molecules with different concentrations and chain lengths and two hexagonal MCM-41 type materials incorporating octadecyl-trimethyl ammonium bromide were tested. Best results were obtained by preparing lamellar MCM-50 zirconium and titanium phosphates in the presence of n-dodecyl-trimethylammonium at a relative molar concentration (surfactant/phosphate) of 1.

Vapor pressures of some azides have been determined by the transpiration method. The molar enthal... more Vapor pressures of some azides have been determined by the transpiration method. The molar enthalpies of vaporization D g l H m of these compounds were derived from the temperature dependencies of vapor pressures. The measured data sets were successfully checked for internal consistency by comparison with vaporization enthalpies of similarly structured compounds.

An image based detection of chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA) for th... more An image based detection of chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA) for the quantification of triclopyr has been developed. The immunoassay was an indirect competitive immunoassay with an anti-rabbit secondary antibody conjugated to horseradish peroxidase (HRP). Chemiluminescence was produced by the luminol/H 2 O 2 /HRP reaction, detected by a monochrome video CCD camera and digitized with an Imagraph IC-PCI frame grabber using a custom program developed in C þþ (Microsoft Visual C þþ 6.0). Two main improvements are reported in the data processing software: the implementation of a circular mesh covering the perimeter of each well, eliminating diffuse light from the neighboring wells, and the use of volume (the integration of light intensity of all pixels that define a well) as an analytical signal instead of CL intensity or area (as usual in commercial plate readers) to improve precision for normalization of the total light output. The standard curve was produced for 0.01-10 ng/L triclopyr. The limit of detection was 0.8 ng/L and the variation coefficient was 3.07% (n ¼ 10, P ¼ 0.05).

The measurement of serum C-reactive protein (CRP) levels has been given particular interest as a ... more The measurement of serum C-reactive protein (CRP) levels has been given particular interest as a marker of inflammation associated with cardiovascular diseases. CRP belongs to the pentraxin family of proteins and the routine clinical analysis of CRP in blood samples is used as an important factor in primary prevention programmes together with causative and predisposing factors. This review focuses on the most representative methodologies and strategies for CRP detection and quantification that have been recently proposed, as well as reviewing those that are currently being developed for the specific, sensitive, inexpensive and high-throughput blood analysis of this protein.

The detection of nitroaromatic compounds, best known as raw materials in explosives preparations,... more The detection of nitroaromatic compounds, best known as raw materials in explosives preparations, is important in many fields including environmental science, public security and forensics. CdSe quantum dots capped with PAMAM-G 4 dendrimer were synthetized in water and used for the detection of trace amounts of three nitroaromatic compounds: 4-methoxy-2-nitrophenol (MNP), 2-amine-5chloro-1,3-dinitrobenzene (ACNB) and 3-methoxy-4-nitrobenzoic acid (MNB). To increase the apparent water solubility of these compounds ␣-cyclodextrin (␣-CD) was used to promote the formation of inclusion complexes. The studied nitroaromatic compounds (plus ␣-CD) significantly quenched the fluorescence intensity of the nanocomposite with linear Stern-Volmer plots. The Stern-Volmer constants (standard deviation in parenthesis) were: MNB, K SV = 65 × 10 4 M −1 ; ACNB, K SV = 19(2) × 10 4 M −1 ; and, MNP, K SV = 33(1) × 10 2 M −1 . These constants suggest the formation of a ground state complex between the nitroaromatric compounds and the sensor which confers a relatively high analytical sensitivity. The detection sensibilities are about 0.01 mg L −1 for MNB and ACNB and about 0.1 mg L −1 for MNP. No interferences or small interferences are observed for trinitrotoluene [K SV = 10(2) × 10 2 × M −1 ], 2,4-dinitrotoluene [K SV = 20(3) × 10 M −1 ], 2,6-dinitrotoluene [K SV = 11(4) × 10 M −1 ] and nitrobenzene [K SV = 2(1) × 10 3 × M −1 ].

A fluorescent hybrid cadmium sulfide quantum dots (QDs) nanocomposites assembled in a porous phos... more A fluorescent hybrid cadmium sulfide quantum dots (QDs) nanocomposites assembled in a porous phosphate heterostructures (PPH) functionalized with mercaptopropyl (PPH-SH) and propionitrile (PPH-CN) where synthesised in water and show high stability. Both materials, show fluorescence in the 450-700 nm wavelength range but the PPH-SH-CdS is about five times more fluorescent than PPH-CN-CdS. The maximum emission wavelengths of the resulting materials are 576 nm (PPH-SH-CdS) and 616 nm (PPH-CN-CdS) and show Stokes shifts higher than 300 nm. The nanocomposites were characterized by TEM, EDS, FT-IR, XRD and fluorescence. These materials are suitable for fingerprint analysis.

Chemosphere, 2005

The potential of removing nickel and copper from industrial electroplating wastewaters by using m... more The potential of removing nickel and copper from industrial electroplating wastewaters by using mesoporous materials with MCM-41 type structure functionalised with different ratios of aminopropyl groups, namely Na50, Na25 and Na5, were evaluated. The synthesised solids sorbents obtained were characterised by X-ray diffraction, elemental chemical analysis and IR spectroscopy. In preliminary experiments, studies were carried out to determine the optimal experimental conditions for the retention of heavy ions. Effects of concentration, optimal pH, interference with humic substances and other metals were studied for Na5, which showed the best capacity of absorption determined by the corresponding isotherm. This material has a greater selectivity against sodium, indicating that ionic strength does not affect the extraction. Results of an application of this material to remove nickel and copper in synthetic and real industrial wastewater samples from an electrochemical industry area are s...

This work reports two methods developed for the separation and determination of the enantiomers o... more This work reports two methods developed for the separation and determination of the enantiomers of the new alkaloid malacitanine (MLC) and the determination of the enantiomeric purity in mixtures. First, the isomers were separated using a Chirex 3020 (250 mm × 4.6 mm, 5 m) chiral column with a mobile phase of cyclohexane-1,2-dichloroethaneethanol-trifluoroacetic acid (64:30:6:0.6, v/v/v/v) at a flow rate of 1 mL/min and fluorimetric detection. Obtained retention times were 12.4 and 15.9 min (+ and −) with a resolution Rs of 1.13. Relative standard deviations (RSDs) were 2.5 and 2.4% at the 0.5-g level (four determinations). Second, a nonenantioselective procedure for the determination of enantiomeric purity of MLC using a Lichrospher R Si-60 (250 mm × 5 mm, 5 m) normal phase with a mobile phase of 100% ethanol at a flow rate of 0.9 mL/min coupled to two detectors in series, fluorimetric and polarimetric. RSD of 3.3% was obtained. Calculated enantiomeric purity by chiral chromatography gave 48.6% (−)-MLC in the near racemic product. Using polarimetric signal of the nonseparated enantiomers and comparing the slopes of the calibration curves (enantiomers) from the racemic product gave 47.8% (−)-MLC content. A study of accuracy of (−)-MLC gave recoveries from 98.3 to 100.7%.

Magnesium is an essential mineral in human metabolism, and is the second most abundant intracellu... more Magnesium is an essential mineral in human metabolism, and is the second most abundant intracellular cation and the fourth most abundant in the human body. Magnesium has a large variety of biological functions, including being a cofactor for over 300 enzymes, mainly involving phosphorylation of proteins and nucleic acids. Low levels of magnesium in the body can develop during different illnesses, such as diabetes (type 2), metabolic syndrome, cardiac arrhythmias, and muscular constriction. The present review shows the advances in analytical chemistry based on sensor systems to quantify the concentration of magnesium in different biological samples, plasma, serum, or urine, that are relevant to human health.

Fenton's reaction is often used to decompose stable substances in wastewater. In this study, expe... more Fenton's reaction is often used to decompose stable substances in wastewater. In this study, experiments based on the effect of porous phosphate heterostructures as catalyst sorbent of Fe 2+ synthesised by different procedures were planned. The examined PPH-Fe/H 2 O 2 as oxidant in a heterogeneous process under mild conditions at pH 5 was found to be very efficient for discoloration of a simulated wastewater containing 50 mg L −1 of a commercial azo dye (Reactive Black 5) reaching 95% of decolourization. Under the described conditions total visual decolourization was achieved after 360 min. This study can provide a simple, effective, and economic system ideal for the treatment of toxic and nonbiodegradable azo dyes.

The effects of cyclodextrins and TX-100 micelles on the fluorescent properties of 2-(dimethylamin... more The effects of cyclodextrins and TX-100 micelles on the fluorescent properties of 2-(dimethylamino)fluorene (DAF) were studied. The photophysical properties of DAF in the micelle aggregates and cyclodextrins were used to explain how the cavity might affect the dynamics of intramolecular charge transfer and the twisting of the molecule. Results obtained show that a-, band c-cyclodextrins interact in a different way with DAF and different values of quantum yield, lifetimes and absorption and emission wavelength were obtained. Because a small interior cavity size, a-cyclodextrin do not show interaction with DAF. Quenching studies demonstrated that in Triton X-100 micelles, DAF molecules migrated to the non polar region.

Adsorption of uranyl ions onto kaolinite, montmorillonite, humic acid and composite clay material... more Adsorption of uranyl ions onto kaolinite, montmorillonite, humic acid and composite clay material (both clays and humic acid) was studied by measuring the system response to clay suspensions (pre-equilibrated with or without uranyl) and to perturbations of the solution chemistry. Adsorption behavior of selected materials under the frame of batch experiments was tested at high uranyl concentrations (6-1170 μg/mL; 2.5 × 10 −2 to 4.9 μM), whereas that under flow through continuous stirred reactor experiments was tested at low concentrations (1.00 × 10 −4 to 1.18 × 10 −4 M). Both experiments were developed at pH 4.5 and ionic strength 0.2 mM. The adsorption experiments follow a Langmuir isotherm model with a good correlation coefficient (R 2 N 0.97). The calculated amount of adsorbed and desorbed uranyl was carried out by numeric integration of the experimental data, whereas the desorption rates were determined from the breakthrough curve experiments. Kaolinite with highly disordered structure adsorbed less uranyl (3.86 × 10 −6 mol/g) than well-ordered kaolinite (1.76 × 10 −5 mol/g). Higher amount of uranyl was adsorbed by montmorillonite (3.60 × 10 −5 mol/g) and only half of adsorbed amount was desorbed (1.85 × 10 −5 mol/g). The molecular interactions between kaolinite, montmorillonite, humic acid, composite material and saturated uranyl ion solutions were studied by molecular fluorescence, infrared and X-ray photoelectron spectroscopy. The Stern-Volmer constant obtained for montmorillonite (2.6 × 10 3 M −1 ) is higher than for kaolinite (0.3 × 10 3 M −1 ). Molecular vibrations of Si\O stretching and Al\OH bending related to hydroxylated groups (`SiOH or`AlOH) of kaolinite and montmorillonite show structural changes when uranyl ions are adsorbed. X-ray photoelectron spectroscopy shows that the U 4f 7/2 core level signals occur at 380.5 eV in either kaolinite or montmorillonite that resulted from the interaction of aluminol surface sites with the (UO 2 ) 3 (OH) 5 + .

A newly synthesized family of materials prepared with surfactant as organic template were tested ... more A newly synthesized family of materials prepared with surfactant as organic template were tested for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water, using pyrene (Pyr) and benzo[a]pyrene (B[a]P) as PAHs representatives. Particular attention was paid to the evaluation of the recovery factors with dichloromethane as eluent in order to estimate their potential as adsorbing solid phases for PAH remediation or analysis. Eleven lamellar MCM-50 type materials incorporating n-alkyl-(n ¼ 12, 16, 18) trimethylammonium bromide molecules with different concentrations and chain lengths and two hexagonal MCM-41 type materials incorporating octadecyl-trimethyl ammonium bromide were tested. Best results were obtained by preparing lamellar MCM-50 zirconium and titanium phosphates in the presence of n-dodecyl-trimethylammonium at a relative molar concentration (surfactant/phosphate) of 1.

Vapor pressures of some azides have been determined by the transpiration method. The molar enthal... more Vapor pressures of some azides have been determined by the transpiration method. The molar enthalpies of vaporization D g l H m of these compounds were derived from the temperature dependencies of vapor pressures. The measured data sets were successfully checked for internal consistency by comparison with vaporization enthalpies of similarly structured compounds.

An image based detection of chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA) for th... more An image based detection of chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA) for the quantification of triclopyr has been developed. The immunoassay was an indirect competitive immunoassay with an anti-rabbit secondary antibody conjugated to horseradish peroxidase (HRP). Chemiluminescence was produced by the luminol/H 2 O 2 /HRP reaction, detected by a monochrome video CCD camera and digitized with an Imagraph IC-PCI frame grabber using a custom program developed in C þþ (Microsoft Visual C þþ 6.0). Two main improvements are reported in the data processing software: the implementation of a circular mesh covering the perimeter of each well, eliminating diffuse light from the neighboring wells, and the use of volume (the integration of light intensity of all pixels that define a well) as an analytical signal instead of CL intensity or area (as usual in commercial plate readers) to improve precision for normalization of the total light output. The standard curve was produced for 0.01-10 ng/L triclopyr. The limit of detection was 0.8 ng/L and the variation coefficient was 3.07% (n ¼ 10, P ¼ 0.05).

The measurement of serum C-reactive protein (CRP) levels has been given particular interest as a ... more The measurement of serum C-reactive protein (CRP) levels has been given particular interest as a marker of inflammation associated with cardiovascular diseases. CRP belongs to the pentraxin family of proteins and the routine clinical analysis of CRP in blood samples is used as an important factor in primary prevention programmes together with causative and predisposing factors. This review focuses on the most representative methodologies and strategies for CRP detection and quantification that have been recently proposed, as well as reviewing those that are currently being developed for the specific, sensitive, inexpensive and high-throughput blood analysis of this protein.

The detection of nitroaromatic compounds, best known as raw materials in explosives preparations,... more The detection of nitroaromatic compounds, best known as raw materials in explosives preparations, is important in many fields including environmental science, public security and forensics. CdSe quantum dots capped with PAMAM-G 4 dendrimer were synthetized in water and used for the detection of trace amounts of three nitroaromatic compounds: 4-methoxy-2-nitrophenol (MNP), 2-amine-5chloro-1,3-dinitrobenzene (ACNB) and 3-methoxy-4-nitrobenzoic acid (MNB). To increase the apparent water solubility of these compounds ␣-cyclodextrin (␣-CD) was used to promote the formation of inclusion complexes. The studied nitroaromatic compounds (plus ␣-CD) significantly quenched the fluorescence intensity of the nanocomposite with linear Stern-Volmer plots. The Stern-Volmer constants (standard deviation in parenthesis) were: MNB, K SV = 65 × 10 4 M −1 ; ACNB, K SV = 19(2) × 10 4 M −1 ; and, MNP, K SV = 33(1) × 10 2 M −1 . These constants suggest the formation of a ground state complex between the nitroaromatric compounds and the sensor which confers a relatively high analytical sensitivity. The detection sensibilities are about 0.01 mg L −1 for MNB and ACNB and about 0.1 mg L −1 for MNP. No interferences or small interferences are observed for trinitrotoluene [K SV = 10(2) × 10 2 × M −1 ], 2,4-dinitrotoluene [K SV = 20(3) × 10 M −1 ], 2,6-dinitrotoluene [K SV = 11(4) × 10 M −1 ] and nitrobenzene [K SV = 2(1) × 10 3 × M −1 ].

A fluorescent hybrid cadmium sulfide quantum dots (QDs) nanocomposites assembled in a porous phos... more A fluorescent hybrid cadmium sulfide quantum dots (QDs) nanocomposites assembled in a porous phosphate heterostructures (PPH) functionalized with mercaptopropyl (PPH-SH) and propionitrile (PPH-CN) where synthesised in water and show high stability. Both materials, show fluorescence in the 450-700 nm wavelength range but the PPH-SH-CdS is about five times more fluorescent than PPH-CN-CdS. The maximum emission wavelengths of the resulting materials are 576 nm (PPH-SH-CdS) and 616 nm (PPH-CN-CdS) and show Stokes shifts higher than 300 nm. The nanocomposites were characterized by TEM, EDS, FT-IR, XRD and fluorescence. These materials are suitable for fingerprint analysis.