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Analytica Chimica Acta (v.580, #2)
Detection of trace organophosphorus vapor with a self-assembled bilayer functionalized SiO2 microcantilever piezoresistive sensor by Guomin Zuo; Xinxin Li; Peng Li; Tiantian Yang; Yuelin Wang; Zhenxing Cheng; Songlin Feng (pp. 123-127).
Using piezoresistive SiO2 microcantilever technology, we present an ultra-sensitive chemical sensor for trace organophosphorus vapor detection. A self-assembled composite layer of Cu2+/11-mercaptoundecanoic acid is modified on the surface of the sensing cantilever as a specific coating to capture PO containing compounds. Experimental results indicate that the sensor can be quite sensitive to DMMP vapor (well known as a simulant of nerve agent). The signal-noise-limited detection resolution of the sensor is experimentally obtained as low as several parts per billion. Besides that the sensor can yield reversible and repeatable response to DMMP vapor, adsorption of DMMP on the self-assembled composite layer is well fit to the Langmuir isotherm model.
Keywords: Microcantilever; Nerve agent; Trace chemical sensor; 11-Mercaptoundecanoic acid; Self-assembled monolayer
Detection of trace organophosphorus vapor with a self-assembled bilayer functionalized SiO2 microcantilever piezoresistive sensor by Guomin Zuo; Xinxin Li; Peng Li; Tiantian Yang; Yuelin Wang; Zhenxing Cheng; Songlin Feng (pp. 123-127).
Using piezoresistive SiO2 microcantilever technology, we present an ultra-sensitive chemical sensor for trace organophosphorus vapor detection. A self-assembled composite layer of Cu2+/11-mercaptoundecanoic acid is modified on the surface of the sensing cantilever as a specific coating to capture PO containing compounds. Experimental results indicate that the sensor can be quite sensitive to DMMP vapor (well known as a simulant of nerve agent). The signal-noise-limited detection resolution of the sensor is experimentally obtained as low as several parts per billion. Besides that the sensor can yield reversible and repeatable response to DMMP vapor, adsorption of DMMP on the self-assembled composite layer is well fit to the Langmuir isotherm model.
Keywords: Microcantilever; Nerve agent; Trace chemical sensor; 11-Mercaptoundecanoic acid; Self-assembled monolayer
Flow-injection immuno-bioassay for interleukin-6 in humans based on gold nanoparticles modified screen-printed graphite electrodes by Ke Zhong Liang; Wei Jun Mu (pp. 128-135).
A flow-injection electrochemical immunoassay system based on a disposable immunosensor for the determination of interleukin-6 (IL-6) was proposed. The immunosensor was prepared by entrapping horseradish peroxidase (HRP)-labeled IL-6 antibody into gold nanoparticles-modified composite membrane at a screen-printed graphite electrode. With a non-competitive immunoassay format, the immunosensor was inserted in the flow system with an injection of sample, and the injected sample containing IL-6 antigen was produced transparent immunoaffinity reaction with the immobilized HRP-labeled IL-6 antibody. The formed antigen–antibody complex inhibited partly the active center of HRP, and decreased the immobilized HRP to H2O2 reduction. The performance and factors influencing the performance of the immunosensor were investigated. Under optimal conditions, the current change obtained from the labeled HRP relative to thionine–H2O2 system was proportional to the IL-6 concentration in the range of 5–100ngL−1 with a detection limit of 1.0ngL−1 (at 3δ). The flow-injection immunoassay system could automatically control the incubation, washing and measurement steps with acceptable reproducibility and good stability. Moreover, the proposed immunosensors were used to analyze IL-6 in human serum specimens. Analytical results of clinical samples show the developed immunoassay has a promising alternative approach for detecting IL-6 in the clinical diagnosis.
Keywords: Electrochemical immunosensor; Flow-injection immunoassay; Interleukin-6; Physiological measurement
Flow-injection immuno-bioassay for interleukin-6 in humans based on gold nanoparticles modified screen-printed graphite electrodes by Ke Zhong Liang; Wei Jun Mu (pp. 128-135).
A flow-injection electrochemical immunoassay system based on a disposable immunosensor for the determination of interleukin-6 (IL-6) was proposed. The immunosensor was prepared by entrapping horseradish peroxidase (HRP)-labeled IL-6 antibody into gold nanoparticles-modified composite membrane at a screen-printed graphite electrode. With a non-competitive immunoassay format, the immunosensor was inserted in the flow system with an injection of sample, and the injected sample containing IL-6 antigen was produced transparent immunoaffinity reaction with the immobilized HRP-labeled IL-6 antibody. The formed antigen–antibody complex inhibited partly the active center of HRP, and decreased the immobilized HRP to H2O2 reduction. The performance and factors influencing the performance of the immunosensor were investigated. Under optimal conditions, the current change obtained from the labeled HRP relative to thionine–H2O2 system was proportional to the IL-6 concentration in the range of 5–100ngL−1 with a detection limit of 1.0ngL−1 (at 3δ). The flow-injection immunoassay system could automatically control the incubation, washing and measurement steps with acceptable reproducibility and good stability. Moreover, the proposed immunosensors were used to analyze IL-6 in human serum specimens. Analytical results of clinical samples show the developed immunoassay has a promising alternative approach for detecting IL-6 in the clinical diagnosis.
Keywords: Electrochemical immunosensor; Flow-injection immunoassay; Interleukin-6; Physiological measurement
Penicillamine determination using a tyrosinase micro-rotating biosensor by Angel A.J. Torriero; Eloy Salinas; Eduardo J. Marchevsky; Julio Raba; Juana J. Silber (pp. 136-142).
Tyrosinase [EC 1.14.18.1], immobilized on a rotating disk, catalyzed the oxidation of catechols to o-benzoquinone, whose back electrochemical reduction was detected on glassy carbon electrode surface at −150mV versus Ag/AgCl/NaCl 3M. Thus, when penicillamine (PA) was added to the solution, this thiol-containing compound participate in Michael type addition reactions with o-benzoquinone to form the corresponding thioquinone derivatives, decreasing the reduction current obtained proportionally to the increase of its concentration. This method could be used for sensitive determination of PA in drug and human synthetic serum samples. A linear range of 0.02–80μM ( r=0.999) was obtained for amperometric determination of PA in buffered pH 7.0 solutions (0.1M phosphate buffer). The biosensor has a reasonable reproducibility (R.S.D.<4.0%) and a very stable amperometric response toward this compound (more than 1 month).
Keywords: Penicillamine; Glassy carbon; Biosensor; Tyrosinase; 4-; tert; -Butylcatechol
Penicillamine determination using a tyrosinase micro-rotating biosensor by Angel A.J. Torriero; Eloy Salinas; Eduardo J. Marchevsky; Julio Raba; Juana J. Silber (pp. 136-142).
Tyrosinase [EC 1.14.18.1], immobilized on a rotating disk, catalyzed the oxidation of catechols to o-benzoquinone, whose back electrochemical reduction was detected on glassy carbon electrode surface at −150mV versus Ag/AgCl/NaCl 3M. Thus, when penicillamine (PA) was added to the solution, this thiol-containing compound participate in Michael type addition reactions with o-benzoquinone to form the corresponding thioquinone derivatives, decreasing the reduction current obtained proportionally to the increase of its concentration. This method could be used for sensitive determination of PA in drug and human synthetic serum samples. A linear range of 0.02–80μM ( r=0.999) was obtained for amperometric determination of PA in buffered pH 7.0 solutions (0.1M phosphate buffer). The biosensor has a reasonable reproducibility (R.S.D.<4.0%) and a very stable amperometric response toward this compound (more than 1 month).
Keywords: Penicillamine; Glassy carbon; Biosensor; Tyrosinase; 4-; tert; -Butylcatechol
A fluorescent chemosensor for cobalt ions based on a multi-substituted phenol-ruthenium(II) tris(bipyridine) complex by Chun-Yan Li; Xiao-Bing Zhang; Zhen Jin; Rui Han; Guo-Li Shen; Ru-Qin Yu (pp. 143-148).
An amide-linked 2,6-bis{[(2-hydroxy-5- tert-butylbenzyl)(pyridyl-2-methyl)-amino]-methyl}-4-methylphenol-ruthenium(II) tris(bipyridine) 2PF6− complex,1, was first used to recognize Co(II) in EtOH/H2O (1:1, v/v) solution, with the ruthenium(II) tris(bipyridine) moiety selected as a fluorophore and the multi-substituted phenol unit chosen as a receptor. The fluorescence quenching of1 was attributed to the formation of an inclusion complex between multi-substituted phenol unit and Co(II) by 1:1 complex ratio ( K=2.5×105), which has been utilized as the basis of the fabrication of the Co(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Co(II)-sensitive chemosensor were investigated. The sensor can be applied to the quantification of Co(II) with a linear range covering from 1.0×10−7 to 5.0×10−5M and a detection limit of 5×10−8M. The experiment results show that the response behavior of1 to Co(II) is pH-independent in medium condition (pH 4.5–9.5) and show excellent selectivity for Co(II) over transition metal cations except Cu(II). The chemosensor has been used for determination of Co(II) in water samples.
Keywords: Fluorescent chemosensor; Cobalt(II) ions; Ruthenium(II) tris(bipyridine); Multi-substituted phenol
A fluorescent chemosensor for cobalt ions based on a multi-substituted phenol-ruthenium(II) tris(bipyridine) complex by Chun-Yan Li; Xiao-Bing Zhang; Zhen Jin; Rui Han; Guo-Li Shen; Ru-Qin Yu (pp. 143-148).
An amide-linked 2,6-bis{[(2-hydroxy-5- tert-butylbenzyl)(pyridyl-2-methyl)-amino]-methyl}-4-methylphenol-ruthenium(II) tris(bipyridine) 2PF6− complex,1, was first used to recognize Co(II) in EtOH/H2O (1:1, v/v) solution, with the ruthenium(II) tris(bipyridine) moiety selected as a fluorophore and the multi-substituted phenol unit chosen as a receptor. The fluorescence quenching of1 was attributed to the formation of an inclusion complex between multi-substituted phenol unit and Co(II) by 1:1 complex ratio ( K=2.5×105), which has been utilized as the basis of the fabrication of the Co(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Co(II)-sensitive chemosensor were investigated. The sensor can be applied to the quantification of Co(II) with a linear range covering from 1.0×10−7 to 5.0×10−5M and a detection limit of 5×10−8M. The experiment results show that the response behavior of1 to Co(II) is pH-independent in medium condition (pH 4.5–9.5) and show excellent selectivity for Co(II) over transition metal cations except Cu(II). The chemosensor has been used for determination of Co(II) in water samples.
Keywords: Fluorescent chemosensor; Cobalt(II) ions; Ruthenium(II) tris(bipyridine); Multi-substituted phenol
Chemiluminescence optosensing implemented with multicommutation: Determination of salicylic acid by E.J. Llorent-Martínez; P. Ortega-Barrales; A. Molina-Díaz (pp. 149-154).
In this paper we have coupled, for the first time, chemiluminescent detection with multicommuted optosensing principles. This approach has been implemented with the use of a commercial flow cell of 1mm optical path length filled with an appropriate anionic exchanger gel as chemiluminescence sensing phase. The cell was placed in front of the window of the photosensor module of a home-made luminometer developed in our laboratory and a flat mirror was stuck on the back of the cell. The suitability of using chemiluminescence as detection technique in multicommuted flow-through optosensors has been demonstrated: the determination of salicylic acid by simple oxidation with permanganate on the sensing solid phase was chosen as model reaction. The proposed system allows the determination of salicylic acid in pharmaceuticals, with a sample frequency as high as even 60samplesh−1 and showing a detection limit of 0.30μgmL−1, the linear response range is 1–30μgmL−1 and the R.S.D. is 3.1%. Satisfactory results have been obtained when applying the sensor to pharmaceuticals. The accuracy of the proposed methodology has been tested by using a reference method.
Keywords: Multicommutation; Flow-through optosensor; Salicylic acid; Chemiluminescence
Chemiluminescence optosensing implemented with multicommutation: Determination of salicylic acid by E.J. Llorent-Martínez; P. Ortega-Barrales; A. Molina-Díaz (pp. 149-154).
In this paper we have coupled, for the first time, chemiluminescent detection with multicommuted optosensing principles. This approach has been implemented with the use of a commercial flow cell of 1mm optical path length filled with an appropriate anionic exchanger gel as chemiluminescence sensing phase. The cell was placed in front of the window of the photosensor module of a home-made luminometer developed in our laboratory and a flat mirror was stuck on the back of the cell. The suitability of using chemiluminescence as detection technique in multicommuted flow-through optosensors has been demonstrated: the determination of salicylic acid by simple oxidation with permanganate on the sensing solid phase was chosen as model reaction. The proposed system allows the determination of salicylic acid in pharmaceuticals, with a sample frequency as high as even 60samplesh−1 and showing a detection limit of 0.30μgmL−1, the linear response range is 1–30μgmL−1 and the R.S.D. is 3.1%. Satisfactory results have been obtained when applying the sensor to pharmaceuticals. The accuracy of the proposed methodology has been tested by using a reference method.
Keywords: Multicommutation; Flow-through optosensor; Salicylic acid; Chemiluminescence
Detection of carbamic and organophosphorous pesticides in water samples using a cholinesterase biosensor based on Prussian Blue-modified screen-printed electrode by Fabiana Arduini; Francesco Ricci; Catalin S. Tuta; Danila Moscone; Aziz Amine; Giuseppe Palleschi (pp. 155-162).
In the present paper, a comparative study using Co-phthalocyanine and Prussian Blue-modified screen-printed electrodes, has been performed. Both the electrodes have demonstrated an easiness of preparation together with high sensitivity towards thicoholine (LOD=5×10−7 and 5×10−6M for Co-phthalocyanine and Prussian Blue, respectively) with high potentialities for pesticide measurement. Prussian Blue-modified screen-printed electrodes were then selected for successive enzyme immobilization due to their higher operative stability demonstrated in previous works. AChE and BChE enzymes were used and inhibition effect of different pesticides was studied with both the enzymes. AChE-based biosensors have demonstrated a higher sensitivity towards aldicarb (50% inhibition with 50ppb) and carbaryl (50% inhibition with 85ppb) while BChE biosensors have shown a higher affinity towards paraoxon (50% inhibition with 4ppb) and chlorpyrifos-methyl oxon (50% inhibition with 1ppb). Real samples were also tested in order to evaluate the matrix effect and recovery values comprised between 79 and 123% were obtained.
Keywords: Pesticide; Acetylcholinesterase; Butyrylcholinesterase; Screen-printed electrodes
Detection of carbamic and organophosphorous pesticides in water samples using a cholinesterase biosensor based on Prussian Blue-modified screen-printed electrode by Fabiana Arduini; Francesco Ricci; Catalin S. Tuta; Danila Moscone; Aziz Amine; Giuseppe Palleschi (pp. 155-162).
In the present paper, a comparative study using Co-phthalocyanine and Prussian Blue-modified screen-printed electrodes, has been performed. Both the electrodes have demonstrated an easiness of preparation together with high sensitivity towards thicoholine (LOD=5×10−7 and 5×10−6M for Co-phthalocyanine and Prussian Blue, respectively) with high potentialities for pesticide measurement. Prussian Blue-modified screen-printed electrodes were then selected for successive enzyme immobilization due to their higher operative stability demonstrated in previous works. AChE and BChE enzymes were used and inhibition effect of different pesticides was studied with both the enzymes. AChE-based biosensors have demonstrated a higher sensitivity towards aldicarb (50% inhibition with 50ppb) and carbaryl (50% inhibition with 85ppb) while BChE biosensors have shown a higher affinity towards paraoxon (50% inhibition with 4ppb) and chlorpyrifos-methyl oxon (50% inhibition with 1ppb). Real samples were also tested in order to evaluate the matrix effect and recovery values comprised between 79 and 123% were obtained.
Keywords: Pesticide; Acetylcholinesterase; Butyrylcholinesterase; Screen-printed electrodes
New extraction procedure to improve the determination of quinolones in poultry muscle by liquid chromatography with ultraviolet and mass spectrometric detection by S. Bailac; D. Barrón; J. Barbosa (pp. 163-169).
The present article aims to develop a new extraction procedure to improve the determination of quinolones in chicken muscle. This new determination method was validated using liquid chromatography–ultraviolet detection (LC–UV) and liquid chromatography–mass spectrometry detection (LC–MS), which has special bearing on stability studies. The results obtained by using the method were compared with the results obtained with a previous methodology. The new extraction procedure presents a sensitivity low enough to determine concentration of these drugs below the permissible maximum residue limits (MRL) in chicken muscle and is less time consuming than the previous methodology.
Keywords: Liquid chromatography; Mass spectrometry; Ultraviolet detection; Chicken tissues and quinolones
New extraction procedure to improve the determination of quinolones in poultry muscle by liquid chromatography with ultraviolet and mass spectrometric detection by S. Bailac; D. Barrón; J. Barbosa (pp. 163-169).
The present article aims to develop a new extraction procedure to improve the determination of quinolones in chicken muscle. This new determination method was validated using liquid chromatography–ultraviolet detection (LC–UV) and liquid chromatography–mass spectrometry detection (LC–MS), which has special bearing on stability studies. The results obtained by using the method were compared with the results obtained with a previous methodology. The new extraction procedure presents a sensitivity low enough to determine concentration of these drugs below the permissible maximum residue limits (MRL) in chicken muscle and is less time consuming than the previous methodology.
Keywords: Liquid chromatography; Mass spectrometry; Ultraviolet detection; Chicken tissues and quinolones
A rapid ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometric method for the qualitative and quantitative analysis of the constituents of the flower of Trollius ledibouri Reichb. by Xiaoqin Li; Zhili Xiong; Xixiang Ying; Lanchong Cui; Wenliang Zhu; Famei Li (pp. 170-180).
A rapid ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometric (UPLC–ESI-MS/MS) method was developed for the qualitative and quantitative determination of the constituents of the flower of Trollius ledibouri Reichb. The analysis was performed on an AcQuity UPLC™ BEH C18 column using gradient elution with a mobile phase of 0.1% acetic acid and acetonitrile over 20min. A tandem quadrupole spectrometer operating in either full scan mode or in MS/MS mode for multiple reaction monitoring (MRM) was used for the qualitative and quantitative analysis of the constituents, respectively. According to the mass spectrometric fragmentation mechanism and UPLC–ESI-MS/MS data, the chemical structures of 15 constituents of the flower of T. ledibouri Reichb. were identified on-line without time-consuming isolation and four of them, 2″- O-β-l-galactopyranosylorientin, 2″- O-β-arabinopyranosylorientin, orientin and vitexin, were quantified. The limits of quantification of these four flavonoids were 540, 321, 515 and 220μgg−1 plant material, respectively. Four commercial samples from different sources were analyzed. The UPLC–ESI-MS/MS method for analyzing the constituents can be used to evaluate the quality of the flower of T. ledibouri Reichb.
Keywords: Ultra-performance liquid chromatography; Electrospray ionization tandem mass spectrometry; Qualitative and quantitative analysis; Flavonoids; Trollius ledibouri; Reichb.; Traditional Chinese medicine
A rapid ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometric method for the qualitative and quantitative analysis of the constituents of the flower of Trollius ledibouri Reichb. by Xiaoqin Li; Zhili Xiong; Xixiang Ying; Lanchong Cui; Wenliang Zhu; Famei Li (pp. 170-180).
A rapid ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometric (UPLC–ESI-MS/MS) method was developed for the qualitative and quantitative determination of the constituents of the flower of Trollius ledibouri Reichb. The analysis was performed on an AcQuity UPLC™ BEH C18 column using gradient elution with a mobile phase of 0.1% acetic acid and acetonitrile over 20min. A tandem quadrupole spectrometer operating in either full scan mode or in MS/MS mode for multiple reaction monitoring (MRM) was used for the qualitative and quantitative analysis of the constituents, respectively. According to the mass spectrometric fragmentation mechanism and UPLC–ESI-MS/MS data, the chemical structures of 15 constituents of the flower of T. ledibouri Reichb. were identified on-line without time-consuming isolation and four of them, 2″- O-β-l-galactopyranosylorientin, 2″- O-β-arabinopyranosylorientin, orientin and vitexin, were quantified. The limits of quantification of these four flavonoids were 540, 321, 515 and 220μgg−1 plant material, respectively. Four commercial samples from different sources were analyzed. The UPLC–ESI-MS/MS method for analyzing the constituents can be used to evaluate the quality of the flower of T. ledibouri Reichb.
Keywords: Ultra-performance liquid chromatography; Electrospray ionization tandem mass spectrometry; Qualitative and quantitative analysis; Flavonoids; Trollius ledibouri; Reichb.; Traditional Chinese medicine
Synthesis of silica-based benzeneboronic acid affinity materials and application as pre-column in coupled-column high-performance liquid chromatography by Fanglou Li; Xinjie Zhao; Wenzhao Wang; Guowang Xu (pp. 181-187).
Three silica-based benzeneboronic acid affinity materials were synthesized by using an m-aminobenzeneboronic acid as the ligand and using three different spacer arms. Under high-pressure, three affinity pre-columns were packed with these materials and the retention of every affinity pre-column with 11 urinary nucleosides was studied. With different spacer arms of boronic acid-substituted silica materials, the absorption to vicinal alcohols ( cis-diols) and stability under acidic elution conditions are of great difference. Coupled-column liquid chromatographic methods for the direct analysis of urinary nucleosides were respectively established. As a result, two of three affinity pre-columns showed good chromatographic property in the on-line analysis of urinary nucleosides. The coupled-column system including pre-column I is the best with excellent linearity ( R2>0.995), good recoveries (85.6–96.9%) and reproducibility (R.S.D.: 1.01–4.02%). The pre-column I could at least endure 150 repetitive injections of a 100μL urinary sample.
Keywords: Benzeneboronic acid-substituted silica; Coupled-column; High-performance affinity chromatography; High-performance liquid chromatography; Direct analysis; Urinary nucleosides
Synthesis of silica-based benzeneboronic acid affinity materials and application as pre-column in coupled-column high-performance liquid chromatography by Fanglou Li; Xinjie Zhao; Wenzhao Wang; Guowang Xu (pp. 181-187).
Three silica-based benzeneboronic acid affinity materials were synthesized by using an m-aminobenzeneboronic acid as the ligand and using three different spacer arms. Under high-pressure, three affinity pre-columns were packed with these materials and the retention of every affinity pre-column with 11 urinary nucleosides was studied. With different spacer arms of boronic acid-substituted silica materials, the absorption to vicinal alcohols ( cis-diols) and stability under acidic elution conditions are of great difference. Coupled-column liquid chromatographic methods for the direct analysis of urinary nucleosides were respectively established. As a result, two of three affinity pre-columns showed good chromatographic property in the on-line analysis of urinary nucleosides. The coupled-column system including pre-column I is the best with excellent linearity ( R2>0.995), good recoveries (85.6–96.9%) and reproducibility (R.S.D.: 1.01–4.02%). The pre-column I could at least endure 150 repetitive injections of a 100μL urinary sample.
Keywords: Benzeneboronic acid-substituted silica; Coupled-column; High-performance affinity chromatography; High-performance liquid chromatography; Direct analysis; Urinary nucleosides
Non-aqueous capillary electrophoresis with red light emitting diode absorbance detection for the analysis of basic dyes by Ali Reza Fakhari; Michael C. Breadmore; Miroslav Macka; Paul R. Haddad (pp. 188-193).
Non-aqueous capillary electrophoresis was evaluated for the separation of five hydrophobic basic blue dyes for application in forensic dye analysis. The use of a red light emitting diode as a high intensity, low-noise light source provided sensitive detection of the blue dyes while also allowing the evaluation of solvents that absorb strongly in the UV region. Excellent peak shapes and separation selectivity were obtained in methanol, ethanol, acetonitrile and dimethylsulfoxide, however water, tetrahydrofuran, dimethylformamide and acetone were unsuitable as solvents due to poor peak shapes and a lack of sensitivity, most likely due to adsorption onto the capillary wall. Due to the known compatibility of methanol with capillary electrophoresis–mass spectrometry, this solvent was examined further with the relative acidity/basicity of the electrolyte being optimised with an artificial neural network. The optimised method was examined for the separation of ink samples from 6 fibre tip and 2 ball point blue or black pens and showed that a unique migration time for the main dye component in seven of the eight pens could be obtained.
Keywords: Capillary electrophoresis; Non-aqueous capillary electrophoresis; Dyes; Light-emmiting diode; Forensics; Ink analysis
Non-aqueous capillary electrophoresis with red light emitting diode absorbance detection for the analysis of basic dyes by Ali Reza Fakhari; Michael C. Breadmore; Miroslav Macka; Paul R. Haddad (pp. 188-193).
Non-aqueous capillary electrophoresis was evaluated for the separation of five hydrophobic basic blue dyes for application in forensic dye analysis. The use of a red light emitting diode as a high intensity, low-noise light source provided sensitive detection of the blue dyes while also allowing the evaluation of solvents that absorb strongly in the UV region. Excellent peak shapes and separation selectivity were obtained in methanol, ethanol, acetonitrile and dimethylsulfoxide, however water, tetrahydrofuran, dimethylformamide and acetone were unsuitable as solvents due to poor peak shapes and a lack of sensitivity, most likely due to adsorption onto the capillary wall. Due to the known compatibility of methanol with capillary electrophoresis–mass spectrometry, this solvent was examined further with the relative acidity/basicity of the electrolyte being optimised with an artificial neural network. The optimised method was examined for the separation of ink samples from 6 fibre tip and 2 ball point blue or black pens and showed that a unique migration time for the main dye component in seven of the eight pens could be obtained.
Keywords: Capillary electrophoresis; Non-aqueous capillary electrophoresis; Dyes; Light-emmiting diode; Forensics; Ink analysis
Quantitative determination of oxidized carbon nanotube probes in yeast by capillary electrophoresis with laser-induced fluorescence detection by Hua Xiao; Hanfa Zou; Chensong Pan; Xiaogang Jiang; X. Chris Le; Ling Yang (pp. 194-199).
Short oxidized multi-walled carbon nanotubes were functionalized with fluorescein isothiocyanate to form carbon nanotube probes (CNTP). The distribution of CNTP in yeast was quantitatively determined by capillary electrophoresis coupled with laser-induced fluorescence detection. The detection sensitivity for CNTP was greatly improved comparing with UV absorbance and Raman detection. The time- and temperature-dependent influx patterns of CNTP into yeast were obtained. The apparent permeability coefficient for influx of CNTP into yeast was calculated, which suggested that CNTP might permeate into yeast through endocytosis. This study implies that CNTP could be a fine drug transporter and might be wildly used in multidrug resistance research and microorganism detection.
Keywords: Capillary electrophoresis; Laser-induced fluorescence detection; Carbon nanotube probes; Yeast; Apparent permeability coefficient
Quantitative determination of oxidized carbon nanotube probes in yeast by capillary electrophoresis with laser-induced fluorescence detection by Hua Xiao; Hanfa Zou; Chensong Pan; Xiaogang Jiang; X. Chris Le; Ling Yang (pp. 194-199).
Short oxidized multi-walled carbon nanotubes were functionalized with fluorescein isothiocyanate to form carbon nanotube probes (CNTP). The distribution of CNTP in yeast was quantitatively determined by capillary electrophoresis coupled with laser-induced fluorescence detection. The detection sensitivity for CNTP was greatly improved comparing with UV absorbance and Raman detection. The time- and temperature-dependent influx patterns of CNTP into yeast were obtained. The apparent permeability coefficient for influx of CNTP into yeast was calculated, which suggested that CNTP might permeate into yeast through endocytosis. This study implies that CNTP could be a fine drug transporter and might be wildly used in multidrug resistance research and microorganism detection.
Keywords: Capillary electrophoresis; Laser-induced fluorescence detection; Carbon nanotube probes; Yeast; Apparent permeability coefficient
Sensitive analysis of two barbiturates in human urine by capillary electrophoresis with sample stacking induced by moving reaction boundary by Qiu-Ling Wang; Liu-Yin Fan; Wei Zhang; Cheng-Xi Cao (pp. 200-205).
An on-line stacking method based on moving reaction boundary (MRB) was developed for the sensitive determination of barbital and phenobarbital in human urine via capillary electrophoresis (CE). The optimized conditions for the method are: 60mmolL−1 pH 11.0 Gly–NaOH as the background electrolyte, 10mmolL−1 pH 5.5 Gly–HCl as sample buffer, secobarbital as the internal standard (IS), 12.5kV, 1.4psi 10s sample injection, 75μm ID 60.2cm total length (50cm effective length) capillary and 214nm detect wavelength. Under the optimized conditions, the method can well stack and separate barbital and phenobarbital in urine samples and result in 20.5-fold and 22.6-fold improvement in concentration sensitivity for barbital and phenobarbital, respectively. Furthermore, the method holds: (1) good linear calibration functions for the two target compounds (correlation coefficients r>0.999), (2) low limits of detection (0.27μgmL−1 for barbital and 0.26μgmL−1 for phenobarbital), (3) low limits of quantification (0.92μgmL−1 for barbital and 0.87μgmL−1 for phenobarbital), (4) good precision (R.S.D. of intra-day and inter-day less than 5.38% for barbital and 1.67% for phenobarbital, respectively) and (5) high recoveries at three concentration levels (90.27–106.36% for barbital and 93.05–113.60% for phenobarbital in urine). The method is simple, sensitive and efficient, and can fit to the need of clinical and forensic toxicology.
Keywords: Capillary electrophoresis; Stacking; Moving reaction boundary; Barbital; Phenobarbital
Sensitive analysis of two barbiturates in human urine by capillary electrophoresis with sample stacking induced by moving reaction boundary by Qiu-Ling Wang; Liu-Yin Fan; Wei Zhang; Cheng-Xi Cao (pp. 200-205).
An on-line stacking method based on moving reaction boundary (MRB) was developed for the sensitive determination of barbital and phenobarbital in human urine via capillary electrophoresis (CE). The optimized conditions for the method are: 60mmolL−1 pH 11.0 Gly–NaOH as the background electrolyte, 10mmolL−1 pH 5.5 Gly–HCl as sample buffer, secobarbital as the internal standard (IS), 12.5kV, 1.4psi 10s sample injection, 75μm ID 60.2cm total length (50cm effective length) capillary and 214nm detect wavelength. Under the optimized conditions, the method can well stack and separate barbital and phenobarbital in urine samples and result in 20.5-fold and 22.6-fold improvement in concentration sensitivity for barbital and phenobarbital, respectively. Furthermore, the method holds: (1) good linear calibration functions for the two target compounds (correlation coefficients r>0.999), (2) low limits of detection (0.27μgmL−1 for barbital and 0.26μgmL−1 for phenobarbital), (3) low limits of quantification (0.92μgmL−1 for barbital and 0.87μgmL−1 for phenobarbital), (4) good precision (R.S.D. of intra-day and inter-day less than 5.38% for barbital and 1.67% for phenobarbital, respectively) and (5) high recoveries at three concentration levels (90.27–106.36% for barbital and 93.05–113.60% for phenobarbital in urine). The method is simple, sensitive and efficient, and can fit to the need of clinical and forensic toxicology.
Keywords: Capillary electrophoresis; Stacking; Moving reaction boundary; Barbital; Phenobarbital
Spectrofluorimetric studies on the binding of salicylic acid to bovine serum albumin using warfarin and ibuprofen as site markers with the aid of parallel factor analysis by Yongnian Ni; Shaojing Su; Serge Kokot (pp. 206-215).
The interactions of salicylic acid (SL) and two different site markers (warfarin for site I and ibuprofen for site II) with bovine serum albumin (BSA) in pH 7.4 Tris–HCl buffer have been investigated with the use of spectrofluorimetry. An equilibrium solution of BSA and SA was titrated separately with the two markers. This initial work showed that the binding of SL with BSA could be quite complex, and that there was probably a competitive interaction occurring between ibuprofen and SL. However, the spectral results were difficult to interpret clearly for the interaction of warfarin and SL in similar circumstances.To extract more information from the resolution of fluorescence excitation-emission spectra, the contour plots of the fluorescence spectra indicated that the optimal excitation wavelengths for BSA, SL, warfarin and ibuprofen were different, and were found to be at 278, 295, 306 and 218nm, respectively. The spectral information was arranged into three-way excitation-emission fluorescence matrix (EEM) stack arrays, and was submitted for analysis by the parallel factor analysis (PARAFAC) algorithm. Firstly, it was demonstrated that the estimated excitation and emission spectral responses for SL, BSA and the site markers, warfarin and ibuprofen, agreed well with the measured spectra. Then, the interpretation of the plots of simultaneously extracted (by PARAFAC) equilibrium concentrations for the above four reactants, showed that: (i) the SL primarily appears to bind in site I but at a different location from the high-affinity binding site (HAS) for warfarin, and the interaction partially overlaps with the low-affinity binding site (LAS) for warfarin. (ii) The SL may have two LAS—one in site II where the HAS for ibuprofen is located, and the other in site I at the LAS for ibuprofen. Thus, application of the PARAFAC method for the study of competitive interaction of SL and BSA with the aid of two different site markers has extracted information unobtainable by traditional methods such as the Scatchard plot, and provided useful means of data visualization.
Keywords: Bovine serum albumin; Salicylic acid; Warfarin; Ibuprofen; Spectrofluorimetry; Parallel factor analysis
Spectrofluorimetric studies on the binding of salicylic acid to bovine serum albumin using warfarin and ibuprofen as site markers with the aid of parallel factor analysis by Yongnian Ni; Shaojing Su; Serge Kokot (pp. 206-215).
The interactions of salicylic acid (SL) and two different site markers (warfarin for site I and ibuprofen for site II) with bovine serum albumin (BSA) in pH 7.4 Tris–HCl buffer have been investigated with the use of spectrofluorimetry. An equilibrium solution of BSA and SA was titrated separately with the two markers. This initial work showed that the binding of SL with BSA could be quite complex, and that there was probably a competitive interaction occurring between ibuprofen and SL. However, the spectral results were difficult to interpret clearly for the interaction of warfarin and SL in similar circumstances.To extract more information from the resolution of fluorescence excitation-emission spectra, the contour plots of the fluorescence spectra indicated that the optimal excitation wavelengths for BSA, SL, warfarin and ibuprofen were different, and were found to be at 278, 295, 306 and 218nm, respectively. The spectral information was arranged into three-way excitation-emission fluorescence matrix (EEM) stack arrays, and was submitted for analysis by the parallel factor analysis (PARAFAC) algorithm. Firstly, it was demonstrated that the estimated excitation and emission spectral responses for SL, BSA and the site markers, warfarin and ibuprofen, agreed well with the measured spectra. Then, the interpretation of the plots of simultaneously extracted (by PARAFAC) equilibrium concentrations for the above four reactants, showed that: (i) the SL primarily appears to bind in site I but at a different location from the high-affinity binding site (HAS) for warfarin, and the interaction partially overlaps with the low-affinity binding site (LAS) for warfarin. (ii) The SL may have two LAS—one in site II where the HAS for ibuprofen is located, and the other in site I at the LAS for ibuprofen. Thus, application of the PARAFAC method for the study of competitive interaction of SL and BSA with the aid of two different site markers has extracted information unobtainable by traditional methods such as the Scatchard plot, and provided useful means of data visualization.
Keywords: Bovine serum albumin; Salicylic acid; Warfarin; Ibuprofen; Spectrofluorimetry; Parallel factor analysis
Seafood freshness determination through vapour phase Fourier transform infrared spectroscopy by S. Armenta; N.M.M. Coelho; R. Roda; S. Garrigues; M. de la Guardia (pp. 216-222).
A new vapour-phase manifold has been developed to determine trimethylamine (TMA) in fish and cephalopod samples by Fourier transform infrared (FT-IR) spectroscopy. Samples were treated off-line for 1h with trichloroacetic acid (TCA), filtered and washed. The obtained extracts were aspirated and alkalinized with NaOH 2.0M, in an on-line system. TMA was separated from the solution in a gas phase separator and then transported by means of a nitrogen carrier into a home made 10cm pathlength IR gas cell, where the corresponding FT-IR spectra were acquired by accumulating 30 scans per spectrum with 2cm−1 nominal resolution. The method was applied to the determination of TMA in natural samples providing concentration values statistically comparables with those obtained by a head space gas chromatography (HS-GC) reference procedure. The sample throughput by FT-IR is increased by a factor of 6 as compared with HS-GC.
Keywords: Vapour phase; Fourier transform infrared spectroscopy; Trimethylamine; Fish and cephalopod samples
Seafood freshness determination through vapour phase Fourier transform infrared spectroscopy by S. Armenta; N.M.M. Coelho; R. Roda; S. Garrigues; M. de la Guardia (pp. 216-222).
A new vapour-phase manifold has been developed to determine trimethylamine (TMA) in fish and cephalopod samples by Fourier transform infrared (FT-IR) spectroscopy. Samples were treated off-line for 1h with trichloroacetic acid (TCA), filtered and washed. The obtained extracts were aspirated and alkalinized with NaOH 2.0M, in an on-line system. TMA was separated from the solution in a gas phase separator and then transported by means of a nitrogen carrier into a home made 10cm pathlength IR gas cell, where the corresponding FT-IR spectra were acquired by accumulating 30 scans per spectrum with 2cm−1 nominal resolution. The method was applied to the determination of TMA in natural samples providing concentration values statistically comparables with those obtained by a head space gas chromatography (HS-GC) reference procedure. The sample throughput by FT-IR is increased by a factor of 6 as compared with HS-GC.
Keywords: Vapour phase; Fourier transform infrared spectroscopy; Trimethylamine; Fish and cephalopod samples
Comparative analysis of naphthodianthrone and phloroglucine derivatives in St. John's Wort extracts by near infrared spectroscopy, high-performance liquid chromatography and capillary electrophoresis by C.W. Huck; G. Abel; M. Popp; G.K. Bonn (pp. 223-230).
A near infrared spectroscopic (NIRS) method is established for quantitative determination of naphthodianthrones and phloroglucine derivatives in St. John's Wort extracts. The validated NIRS method is compared with optimised liquid chromatography (LC) and capillary electrophoresis (CE), applying UV as a detection tool. Optimisation of stationary and mobile phase conditions in reversed-phase liquid chromatography (RP-LC) allow separating the derivatives of interest with high peak symmetry and robustness. Elution takes 15 and 25min on non-porous or porous silica C18 with different porosities, respectively. Capillary electrophoresis (CE) is used for cross-validation of RP-LC. CE enables baseline separation of hypericine and pseudohypericine in less than 2min, but is ten times less sensitive. The validated RP-LC is chosen as a reference method for calibration of the NIRS-system. Analysis of 80 St. John's Wort extracts (320 NIR spectra) and the subsequent chemometric calculations of the best regression model show that NIRS is suitable for analysis of hypericine, pseudohypericine and hyperforine. RP-LC or CE must be employed for the other remaining lower concentrated naphthodianthrone and phloroglucine derivatives. Hypericine and hyperforine are analysed via NIRS with a standard error of estimation (SEE) of 0.52 and 0.50μgmL−1 and standard error of prediction (SEP) of 0.64 and 0.71μgmL−1 within few seconds. The current study demonstrates the suitability of NIRS as an alternative to LC and CE for St. John's Wort producing phytopharmaceutical industry. The short analysis time of few seconds’ assures high sample throughput in routine analysis.
Keywords: Hypericine; Hyperforine; Naphthodianthrone; Phloroglucine; Liquid chromatography; Capillary electrophoresis; Near infrared spectroscopy
Comparative analysis of naphthodianthrone and phloroglucine derivatives in St. John's Wort extracts by near infrared spectroscopy, high-performance liquid chromatography and capillary electrophoresis by C.W. Huck; G. Abel; M. Popp; G.K. Bonn (pp. 223-230).
A near infrared spectroscopic (NIRS) method is established for quantitative determination of naphthodianthrones and phloroglucine derivatives in St. John's Wort extracts. The validated NIRS method is compared with optimised liquid chromatography (LC) and capillary electrophoresis (CE), applying UV as a detection tool. Optimisation of stationary and mobile phase conditions in reversed-phase liquid chromatography (RP-LC) allow separating the derivatives of interest with high peak symmetry and robustness. Elution takes 15 and 25min on non-porous or porous silica C18 with different porosities, respectively. Capillary electrophoresis (CE) is used for cross-validation of RP-LC. CE enables baseline separation of hypericine and pseudohypericine in less than 2min, but is ten times less sensitive. The validated RP-LC is chosen as a reference method for calibration of the NIRS-system. Analysis of 80 St. John's Wort extracts (320 NIR spectra) and the subsequent chemometric calculations of the best regression model show that NIRS is suitable for analysis of hypericine, pseudohypericine and hyperforine. RP-LC or CE must be employed for the other remaining lower concentrated naphthodianthrone and phloroglucine derivatives. Hypericine and hyperforine are analysed via NIRS with a standard error of estimation (SEE) of 0.52 and 0.50μgmL−1 and standard error of prediction (SEP) of 0.64 and 0.71μgmL−1 within few seconds. The current study demonstrates the suitability of NIRS as an alternative to LC and CE for St. John's Wort producing phytopharmaceutical industry. The short analysis time of few seconds’ assures high sample throughput in routine analysis.
Keywords: Hypericine; Hyperforine; Naphthodianthrone; Phloroglucine; Liquid chromatography; Capillary electrophoresis; Near infrared spectroscopy
Application of lead film electrode for simultaneous adsorptive stripping voltammetric determination of Ni(II) and Co(II) as their nioxime complexes by Mieczyslaw Korolczuk; Katarzyna Tyszczuk (pp. 231-235).
An adsorptive stripping voltammetric (AdSV) procedure for simultaneous determination of Ni(II) and Co(II) in the presence of nioxime as a complexing agent at an in situ plated lead film electrode was described. The Co(II) signal was enhanced by exploitation of the catalytic process in the presence of nitrite. Ni(II) and Co(II) signals are better separated than in the case of bismuth film electrodes. Calibration graphs for an accumulation time of 120s are linear from 1×10−9 to 1×10−7molL−1 and from 1×10−10 to 5×10−9molL−1 for Ni(II) and Co(II), respectively. The proposed procedure was applied for Ni(II) and Co(II) determination in water certified reference materials.
Keywords: Lead film electrode; Stripping analysis; Nickel; Cobalt
Application of lead film electrode for simultaneous adsorptive stripping voltammetric determination of Ni(II) and Co(II) as their nioxime complexes by Mieczyslaw Korolczuk; Katarzyna Tyszczuk (pp. 231-235).
An adsorptive stripping voltammetric (AdSV) procedure for simultaneous determination of Ni(II) and Co(II) in the presence of nioxime as a complexing agent at an in situ plated lead film electrode was described. The Co(II) signal was enhanced by exploitation of the catalytic process in the presence of nitrite. Ni(II) and Co(II) signals are better separated than in the case of bismuth film electrodes. Calibration graphs for an accumulation time of 120s are linear from 1×10−9 to 1×10−7molL−1 and from 1×10−10 to 5×10−9molL−1 for Ni(II) and Co(II), respectively. The proposed procedure was applied for Ni(II) and Co(II) determination in water certified reference materials.
Keywords: Lead film electrode; Stripping analysis; Nickel; Cobalt
Determination of tryptophan and histidine by adsorptive cathodic stripping voltammetry using H-point standard addition method by Ali A. Ensafi; R. Hajian (pp. 236-243).
A sequential method is proposed for the determination of tryptophane and histidine by adsorptive cathodic stripping voltammetry using standard addition and H-point standard addition method (HPSAM). The complexes of copper(II) with the amino acids were accumulated onto the surface of a hanging mercury drop electrode for 60s. Then the preconcentrated complexes were reduced by square wave voltammetry and the peak currents were measured. The effect of various parameters such as pH, concentration of copper, accumulation potential, accumulation time and scan rate on the sensitivity were studied by one-at-a time and artificial neural network. Under the optimized conditions, the peak currents at about +0.05 to −0.30V is proportional to the concentration of tryptophan and histidine over the concentration ranges of 5–220 and 100–1200nM, respectively. Optimization of the parameters by one-at-a time showed that at accumulation potential of 0.10V (versus Ag/AgCl reference electrode) the peak current is proportional only to the concentration of tryptophan and histidine does not have any contribution to the current. The optimization results by artificial neural network showed that at accumulation potential of −0.06V (versus Ag/AgCl) the peak current is proportional to the both concentrations of tryptophan and histidine. Therefore, the method of H-point standard addition has been used for resolving overlap voltamograms for determination of histidine in the present of tryptophane. The method was successfully applied to the determination of tryptophan and histidine in synthetic and real samples.
Keywords: Tryptophan; Histidine; H-Point standard addition method; Adsorptive cathodic stripping voltammetry
Determination of tryptophan and histidine by adsorptive cathodic stripping voltammetry using H-point standard addition method by Ali A. Ensafi; R. Hajian (pp. 236-243).
A sequential method is proposed for the determination of tryptophane and histidine by adsorptive cathodic stripping voltammetry using standard addition and H-point standard addition method (HPSAM). The complexes of copper(II) with the amino acids were accumulated onto the surface of a hanging mercury drop electrode for 60s. Then the preconcentrated complexes were reduced by square wave voltammetry and the peak currents were measured. The effect of various parameters such as pH, concentration of copper, accumulation potential, accumulation time and scan rate on the sensitivity were studied by one-at-a time and artificial neural network. Under the optimized conditions, the peak currents at about +0.05 to −0.30V is proportional to the concentration of tryptophan and histidine over the concentration ranges of 5–220 and 100–1200nM, respectively. Optimization of the parameters by one-at-a time showed that at accumulation potential of 0.10V (versus Ag/AgCl reference electrode) the peak current is proportional only to the concentration of tryptophan and histidine does not have any contribution to the current. The optimization results by artificial neural network showed that at accumulation potential of −0.06V (versus Ag/AgCl) the peak current is proportional to the both concentrations of tryptophan and histidine. Therefore, the method of H-point standard addition has been used for resolving overlap voltamograms for determination of histidine in the present of tryptophane. The method was successfully applied to the determination of tryptophan and histidine in synthetic and real samples.
Keywords: Tryptophan; Histidine; H-Point standard addition method; Adsorptive cathodic stripping voltammetry
Bismuth film electrode for anodic stripping voltammetric determination of tin by Emily A. Hutton; Samo B. Ho?evar; Lea Mauko; Božidar Ogorevc (pp. 244-250).
The bismuth film electrode (BiFE), in combination with anodic stripping voltammetry, offers convenient measurement of low concentrations of tin. The procedure involves simultaneous in situ formation of the bismuth film electrode on a glassy carbon substrate electrode, together with electrochemical deposition of tin, in a non-deaerated model solution containing bismuth ions, catechol as complexing agent and the metal analyte, followed by an anodic stripping scan. The BiFE is characterized by an attractive electroanalytical performance, with two distinct voltammetric stripping signals corresponding to tin, accompanied with low background contributions. Several experimental parameters were optimized, such as concentration of bismuth ions and catechol, deposition potential, deposition time and pH of the model solution. In addition, a critical comparison is given with bare glassy carbon and mercury film electrodes, revealing the superior characteristics of BiFE for measurement of tin. BiFE exhibited highly linear behavior in the examined concentration range from 1 to 100μgL−1 of tin ( R2=0.997), an LoD of 0.26μgL−1 tin, and good reproducibility with a calculated R.S.D. of 7.3% for 10μgL−1 tin ( n=10). As an example, the practical applicability of BiFE was tested with the measurement of tin in a real sample of seawater.
Keywords: Bismuth film electrode; Anodic stripping voltammetry; Catechol; Tin
Bismuth film electrode for anodic stripping voltammetric determination of tin by Emily A. Hutton; Samo B. Hočevar; Lea Mauko; Božidar Ogorevc (pp. 244-250).
The bismuth film electrode (BiFE), in combination with anodic stripping voltammetry, offers convenient measurement of low concentrations of tin. The procedure involves simultaneous in situ formation of the bismuth film electrode on a glassy carbon substrate electrode, together with electrochemical deposition of tin, in a non-deaerated model solution containing bismuth ions, catechol as complexing agent and the metal analyte, followed by an anodic stripping scan. The BiFE is characterized by an attractive electroanalytical performance, with two distinct voltammetric stripping signals corresponding to tin, accompanied with low background contributions. Several experimental parameters were optimized, such as concentration of bismuth ions and catechol, deposition potential, deposition time and pH of the model solution. In addition, a critical comparison is given with bare glassy carbon and mercury film electrodes, revealing the superior characteristics of BiFE for measurement of tin. BiFE exhibited highly linear behavior in the examined concentration range from 1 to 100μgL−1 of tin ( R2=0.997), an LoD of 0.26μgL−1 tin, and good reproducibility with a calculated R.S.D. of 7.3% for 10μgL−1 tin ( n=10). As an example, the practical applicability of BiFE was tested with the measurement of tin in a real sample of seawater.
Keywords: Bismuth film electrode; Anodic stripping voltammetry; Catechol; Tin
Statistical design-principal component analysis optimization of a multiple response procedure using cloud point extraction and simultaneous determination of metals by ICP OES by Marcos A. Bezerra; Roy E. Bruns; Sergio L.C. Ferreira (pp. 251-257).
A procedure has been developed for the simultaneous determination of traces amounts of Cd, Cr, Cu, Mn, Ni and Pb from saline oil-refinery effluents and digested vegetable samples using inductively coupled plasma optical emission spectrometry (ICP OES). The procedure is based on cloud point extraction (CPE) of these metals as 2-(bromo-2-pyridylazo)-5-diethyl-amino-phenol (Br-PADAP) complexes into a micellar phase of octylphenoxypolyethoxyethanol (Triton X-114). Optimization of the procedure was performed by response surface methodology (RSM) using a Doehlert design. Principal components (PC) were used to simplify the multiple response analysis. A response surface for the first PC score is useful in determining the optimum conditions for the Cd, Cr, Cu, Mn and Pb determinations whereas the second PC is highly correlated with the Ni response. Improvement factors of 22, 36, 46, 25, 65 and 39, along with limits of detection (3 σB) of 0.081, 0.79, 0.38, 0.83, 0.28 and 0.69μgL−1, and precision expressed as relative standard deviation (%R.S.D., n=8, 20.0μgL−1) of 1.5, 2.2, 3.5, 2.6, 2.5 and 2.5 were achieved for Cd, Cr, Cu, Mn, Ni and Pb, respectively. The accuracy was evaluated by spike tests in oil-refinery effluent samples and analysis of a vegetable certified reference material (NIST 1571, orchard leaves). Results found were in agreement with certified values.
Keywords: Cloud point extraction; Doehlert design; Simultaneous determination in inductively coupled plasma optical emission spectrometry (ICP OES); Principal component analysis; Response surface analysis
Statistical design-principal component analysis optimization of a multiple response procedure using cloud point extraction and simultaneous determination of metals by ICP OES by Marcos A. Bezerra; Roy E. Bruns; Sergio L.C. Ferreira (pp. 251-257).
A procedure has been developed for the simultaneous determination of traces amounts of Cd, Cr, Cu, Mn, Ni and Pb from saline oil-refinery effluents and digested vegetable samples using inductively coupled plasma optical emission spectrometry (ICP OES). The procedure is based on cloud point extraction (CPE) of these metals as 2-(bromo-2-pyridylazo)-5-diethyl-amino-phenol (Br-PADAP) complexes into a micellar phase of octylphenoxypolyethoxyethanol (Triton X-114). Optimization of the procedure was performed by response surface methodology (RSM) using a Doehlert design. Principal components (PC) were used to simplify the multiple response analysis. A response surface for the first PC score is useful in determining the optimum conditions for the Cd, Cr, Cu, Mn and Pb determinations whereas the second PC is highly correlated with the Ni response. Improvement factors of 22, 36, 46, 25, 65 and 39, along with limits of detection (3 σB) of 0.081, 0.79, 0.38, 0.83, 0.28 and 0.69μgL−1, and precision expressed as relative standard deviation (%R.S.D., n=8, 20.0μgL−1) of 1.5, 2.2, 3.5, 2.6, 2.5 and 2.5 were achieved for Cd, Cr, Cu, Mn, Ni and Pb, respectively. The accuracy was evaluated by spike tests in oil-refinery effluent samples and analysis of a vegetable certified reference material (NIST 1571, orchard leaves). Results found were in agreement with certified values.
Keywords: Cloud point extraction; Doehlert design; Simultaneous determination in inductively coupled plasma optical emission spectrometry (ICP OES); Principal component analysis; Response surface analysis
Validation and application of an analytical method for monomethylmercury quantification in aquatic plant tissues by João Canário; Miguel Caetano; Carlos Vale (pp. 258-262).
An analytical methodology for monomethylmercury (MMHg) determination in aquatic plant tissues with low detection limit (346pgg−1) is proposed. It consists of acid digestion (HBr/CuSO4), cleanup step with a Na2S solution, pre-concentration procedure using a dithizone solution in toluene and quantification by GC–ECD. The performance of the methodology has been tested by determining the MMHg concentrations in the certified reference material Fucus Sea Plant Homogenate—IAEA-140/TM (CRM) and in leaves, stems and roots of the salt marsh plants Sarcocornia fruticosa and Halimione portulacoides. The results obtained for CRM were not statistically different ( α=0.056) from the certified value and repeatability was lower than 2.5% for the plant samples analyzed. This coefficient of variation was similar to those obtained in the externally quality control using within-batch and between-batch (<1.4%).
Keywords: Monomethylmercury; Aquatic plant tissues; Gas chromatography–electron capture detection
Validation and application of an analytical method for monomethylmercury quantification in aquatic plant tissues by João Canário; Miguel Caetano; Carlos Vale (pp. 258-262).
An analytical methodology for monomethylmercury (MMHg) determination in aquatic plant tissues with low detection limit (346pgg−1) is proposed. It consists of acid digestion (HBr/CuSO4), cleanup step with a Na2S solution, pre-concentration procedure using a dithizone solution in toluene and quantification by GC–ECD. The performance of the methodology has been tested by determining the MMHg concentrations in the certified reference material Fucus Sea Plant Homogenate—IAEA-140/TM (CRM) and in leaves, stems and roots of the salt marsh plants Sarcocornia fruticosa and Halimione portulacoides. The results obtained for CRM were not statistically different ( α=0.056) from the certified value and repeatability was lower than 2.5% for the plant samples analyzed. This coefficient of variation was similar to those obtained in the externally quality control using within-batch and between-batch (<1.4%).
Keywords: Monomethylmercury; Aquatic plant tissues; Gas chromatography–electron capture detection
Preparation of novel ion exchange polyurethane foam and its application for separation and determination of palladium in environmental samples by E.A. Moawed (pp. 263-270).
The new strong anion exchanger (PUFIX) from polyurethane foam was prepared by coupling of the primary amine of the foam matrix with ethyl iodide. PUFIX was characterized using different tools (IR spectra, elemental analysis, density and thermal analysis). The sorption properties of the new anion exchanger (PUFIX) and chromatographic behaviour for separation and determination of palladium(II) ions at low concentrations from aqueous iodide or thiocyanate media were investigated by a batch and dynamic processes. The maximum sorption of Pd(II) was in the pH range of 0.3–2. The kinetics of sorption of the Pd(II) by the PUFIX was found to be fast with average values of half-life of sorption ( t1/2) of 3.32min. The variation of the sorption of Pd(II) with temperature gives average values of Δ H, Δ S, Δ G and Δ E to be −38.3kJmol−1, −100.7JK−1mol−1, −8.3 and 11.8kJmol−1, respectively. The sorption capacity of PUFIX was 1.69mmolg−1 for Pd(II), preconcentration factors of values ≈250 and the recovery 99–100% were achieved (R.S.D.≈1.24%). The lower detection limit, 1.28ngmL−1 was evaluated using spectrophotometric method (R.S.D.≈2.46%).
Keywords: Polyurethane foam; Sorption; Chromatography; Anion exchange; Palladium(II)
Preparation of novel ion exchange polyurethane foam and its application for separation and determination of palladium in environmental samples by E.A. Moawed (pp. 263-270).
The new strong anion exchanger (PUFIX) from polyurethane foam was prepared by coupling of the primary amine of the foam matrix with ethyl iodide. PUFIX was characterized using different tools (IR spectra, elemental analysis, density and thermal analysis). The sorption properties of the new anion exchanger (PUFIX) and chromatographic behaviour for separation and determination of palladium(II) ions at low concentrations from aqueous iodide or thiocyanate media were investigated by a batch and dynamic processes. The maximum sorption of Pd(II) was in the pH range of 0.3–2. The kinetics of sorption of the Pd(II) by the PUFIX was found to be fast with average values of half-life of sorption ( t1/2) of 3.32min. The variation of the sorption of Pd(II) with temperature gives average values of Δ H, Δ S, Δ G and Δ E to be −38.3kJmol−1, −100.7JK−1mol−1, −8.3 and 11.8kJmol−1, respectively. The sorption capacity of PUFIX was 1.69mmolg−1 for Pd(II), preconcentration factors of values ≈250 and the recovery 99–100% were achieved (R.S.D.≈1.24%). The lower detection limit, 1.28ngmL−1 was evaluated using spectrophotometric method (R.S.D.≈2.46%).
Keywords: Polyurethane foam; Sorption; Chromatography; Anion exchange; Palladium(II)
Phenols removal by immobilized tyrosinase reactor in on-line high performance liquid chromatography by Anna Maria Girelli; Enrico Mattei; Antonella Messina (pp. 271-277).
The development of an immobilized enzyme reactor (IMER) based on tyrosinase immobilized on aminopropyl-controlled pore glass (AP-CPG) for the removal of phenols from model aqueous solutions was reported. To elucidate the influence of the substrate nature, the apparent (V′max,K′m) and the inherent ( Vmax, Km) Michaelis–Menten constants were determined by Lineweaver–Burk method and the external diffusional contributions on measured enzyme activities were removed by a graphical method. The dephenolization process was realized by recycling the phenol solutions through the bioreactor connected to a chitosan trap in order to remove the colored quinone-type products of the tyrosinase reactions. The results indicated that a complete removal of phenol derivatives in the range of 150–300min, with the exception of 60% removal for phenol reached in 400min, was obtained. The observed sequence: cresol>4-methylcathecol>catechol>4-Cl-phenol≫phenol was in accordance to theV′max/K′m values.
Keywords: Phenols removal; Tyrosinase immobilized; Bioreactor
Phenols removal by immobilized tyrosinase reactor in on-line high performance liquid chromatography by Anna Maria Girelli; Enrico Mattei; Antonella Messina (pp. 271-277).
The development of an immobilized enzyme reactor (IMER) based on tyrosinase immobilized on aminopropyl-controlled pore glass (AP-CPG) for the removal of phenols from model aqueous solutions was reported. To elucidate the influence of the substrate nature, the apparent (V′max,K′m) and the inherent ( Vmax, Km) Michaelis–Menten constants were determined by Lineweaver–Burk method and the external diffusional contributions on measured enzyme activities were removed by a graphical method. The dephenolization process was realized by recycling the phenol solutions through the bioreactor connected to a chitosan trap in order to remove the colored quinone-type products of the tyrosinase reactions. The results indicated that a complete removal of phenol derivatives in the range of 150–300min, with the exception of 60% removal for phenol reached in 400min, was obtained. The observed sequence: cresol>4-methylcathecol>catechol>4-Cl-phenol≫phenol was in accordance to theV′max/K′m values.
Keywords: Phenols removal; Tyrosinase immobilized; Bioreactor