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Analytica Chimica Acta (v.575, #2)
An absorbance-based micro-fluidic sensor for diffusion coefficient and molar mass determinations by Adam D. McBrady; Rattikan Chantiwas; Ana Kristine Torgerson; Kate Grudpan; Robert E. Synovec (pp. 151-158).
The H-Sensor reported herein is a micro-fluidic device compatible with flow injection analysis (FIA) and high performance liquid chromatography (HPLC). The device detects analytes at two separate off-chip absorbance flow cells, providing two simultaneous absorbance measurements. The ratio of these two absorbance signals contains analyte diffusion coefficient information. A theoretical model for the sensing mechanism is presented. The model relates the signal Ratio to analyte diffusion coefficient. The model is qualitatively evaluated by comparing theoretical and experimental signal Ratio values. Experimental signal Ratios were collected via FIA for a variety of analytes, including sodium azide, benzoic acid, amino acids, peptides, and proteins. Measuring absorbance at multiple wavelengths provides higher order data allowing the analyte signals from mixtures to be deconvolved via classical least squares (CLS). As a result of the H-Sensor providing two simultaneous signals as a function of time for each sample injection, two simulated second-order HPLC chromatograms were generated using experimental H-Sensor data. The chemometric deconvolution method referred to as the generalized rank annihilation method (GRAM) was used to demonstrate chromatographic and spectroscopic deconvolution. GRAM also provides the signal Ratio value, therefore simultaneously obtaining the analyte diffusion coefficient information during deconvolution. The two chromatograms successfully serve as the standard and unknown for the GRAM deconvolution. GRAM was evaluated on chromatograms at various chromatographic resolutions. GRAM was found to function to a chromatographic resolution at and above 0.25 with a percent quantitative error of less then 10%.
Keywords: Absorbance; Chemometrics; Flow injection; Liquid chromatography; Sensor; Molar mass; Diffusion coefficient
An absorbance-based micro-fluidic sensor for diffusion coefficient and molar mass determinations by Adam D. McBrady; Rattikan Chantiwas; Ana Kristine Torgerson; Kate Grudpan; Robert E. Synovec (pp. 151-158).
The H-Sensor reported herein is a micro-fluidic device compatible with flow injection analysis (FIA) and high performance liquid chromatography (HPLC). The device detects analytes at two separate off-chip absorbance flow cells, providing two simultaneous absorbance measurements. The ratio of these two absorbance signals contains analyte diffusion coefficient information. A theoretical model for the sensing mechanism is presented. The model relates the signal Ratio to analyte diffusion coefficient. The model is qualitatively evaluated by comparing theoretical and experimental signal Ratio values. Experimental signal Ratios were collected via FIA for a variety of analytes, including sodium azide, benzoic acid, amino acids, peptides, and proteins. Measuring absorbance at multiple wavelengths provides higher order data allowing the analyte signals from mixtures to be deconvolved via classical least squares (CLS). As a result of the H-Sensor providing two simultaneous signals as a function of time for each sample injection, two simulated second-order HPLC chromatograms were generated using experimental H-Sensor data. The chemometric deconvolution method referred to as the generalized rank annihilation method (GRAM) was used to demonstrate chromatographic and spectroscopic deconvolution. GRAM also provides the signal Ratio value, therefore simultaneously obtaining the analyte diffusion coefficient information during deconvolution. The two chromatograms successfully serve as the standard and unknown for the GRAM deconvolution. GRAM was evaluated on chromatograms at various chromatographic resolutions. GRAM was found to function to a chromatographic resolution at and above 0.25 with a percent quantitative error of less then 10%.
Keywords: Absorbance; Chemometrics; Flow injection; Liquid chromatography; Sensor; Molar mass; Diffusion coefficient
Highly selective determination of methylmercury with methylmercury-imprinted polymers by Yongwen Liu; Yunhui Zai; Xijun Chang; Yong Guo; Shuangming Meng; Feng Feng (pp. 159-165).
Methylmercury-imprinted and non-imprinted polymers were prepared by formation monomer complex of methylmercury with (4-ethenylphenyl)-4-formate-6-phenyl-2,2′-bipyridine and thermally polymerizing with divinylbenzene (crosslinker) in the presence of 2,2′-azobisisobutyronitrile as initiator and subsequently leached with the acidic thiourea solution (1.0molL−1 of thiourea and 4.0molL−1 of HCl). In the same way, non-imprinted copolymers were prepared without methylmercury chloride added. The separation and preconcentration characteristics of the polymers for methylmercury were investigated by batch and column procedures. The results demonstrated that the methylmercury-imprinted polymers had higher adsorption capacity (170μmolg−1 of dry microbeads) and good selectivity for methylmercury compared to non-imprinted polymers. The distribution ratio ( D) values of the methylmercury-imprinted polymers increased for methylmercury with respect to both D values of Hg(II), Cu(II), Zn(II), Cd(II) and non-imprinted polymers. The relatively selective factor ( αr) values of CH3Hg+/Hg(II), CH3Hg+/Cu(II), CH3Hg+/Zn(II), and CH3Hg+/Cd(II) are 24.0, 46.7, 50.7, and 40.2, which are greater than 1. The methylmercury-imprinted polymers can be used at least twenty times with recoveries no less than 95%. Based on the packed columns with methylmercury-imprinted polymers, a highly selective solid-phase extraction (SPE) and preconcentration method for methylmercury was developed. The metal ion imprinted polymer solid-phase extraction (MIIP-SPE) preconcentration procedure showed a linear calibration curve within concentration range from 0.093 to 22μgL−1. The detection limit and quantification limit were 0.041 and 0.093μgL−1 (3 σ) for cold vapor atomic absorption spectrometry (CVAAS). The relative standard deviation of the 10 replicate determinations was 3.5% for the determination of methylmercury in human hair sample. Determination of methylmercury in certified human hair sample (IAEA-086) and soil certified reference material (CRM 580) demonstrated that the interfering substances in matrix had been almost removed during preconcentration. The methylmercury-imprinted polymers were good enough for methylmercury determination in matrixes containing components with similar chemical property such as Hg(II), Cu(II), Zn(II), and Cd(II).
Keywords: Solid-phase extraction; Metal ion imprinted polymer; Preconcentration; Methylmercury; Cold vapor atomic absorption spectrometry; Human hair; Soil
Highly selective determination of methylmercury with methylmercury-imprinted polymers by Yongwen Liu; Yunhui Zai; Xijun Chang; Yong Guo; Shuangming Meng; Feng Feng (pp. 159-165).
Methylmercury-imprinted and non-imprinted polymers were prepared by formation monomer complex of methylmercury with (4-ethenylphenyl)-4-formate-6-phenyl-2,2′-bipyridine and thermally polymerizing with divinylbenzene (crosslinker) in the presence of 2,2′-azobisisobutyronitrile as initiator and subsequently leached with the acidic thiourea solution (1.0molL−1 of thiourea and 4.0molL−1 of HCl). In the same way, non-imprinted copolymers were prepared without methylmercury chloride added. The separation and preconcentration characteristics of the polymers for methylmercury were investigated by batch and column procedures. The results demonstrated that the methylmercury-imprinted polymers had higher adsorption capacity (170μmolg−1 of dry microbeads) and good selectivity for methylmercury compared to non-imprinted polymers. The distribution ratio ( D) values of the methylmercury-imprinted polymers increased for methylmercury with respect to both D values of Hg(II), Cu(II), Zn(II), Cd(II) and non-imprinted polymers. The relatively selective factor ( αr) values of CH3Hg+/Hg(II), CH3Hg+/Cu(II), CH3Hg+/Zn(II), and CH3Hg+/Cd(II) are 24.0, 46.7, 50.7, and 40.2, which are greater than 1. The methylmercury-imprinted polymers can be used at least twenty times with recoveries no less than 95%. Based on the packed columns with methylmercury-imprinted polymers, a highly selective solid-phase extraction (SPE) and preconcentration method for methylmercury was developed. The metal ion imprinted polymer solid-phase extraction (MIIP-SPE) preconcentration procedure showed a linear calibration curve within concentration range from 0.093 to 22μgL−1. The detection limit and quantification limit were 0.041 and 0.093μgL−1 (3 σ) for cold vapor atomic absorption spectrometry (CVAAS). The relative standard deviation of the 10 replicate determinations was 3.5% for the determination of methylmercury in human hair sample. Determination of methylmercury in certified human hair sample (IAEA-086) and soil certified reference material (CRM 580) demonstrated that the interfering substances in matrix had been almost removed during preconcentration. The methylmercury-imprinted polymers were good enough for methylmercury determination in matrixes containing components with similar chemical property such as Hg(II), Cu(II), Zn(II), and Cd(II).
Keywords: Solid-phase extraction; Metal ion imprinted polymer; Preconcentration; Methylmercury; Cold vapor atomic absorption spectrometry; Human hair; Soil
Column preconcentration of lead in aqueous solution with macroporous epoxy resin-based polymer monolithic matrix by Sui Wang; Ruifeng Zhang (pp. 166-171).
The objective of this article was to investigate the feasibility of epoxy resin-based monoliths prepared by stepwise polymerization and column preconcentration of metal ions using large-scale monolithic matrix. A novel macroporous polymer monolith matrix was prepared from epoxy resin (EP) and ethylenediamine (EDA) and pore-forming reagent (polyethylene glycol, PEG-1000) by in situ step-addition polymerization. The morphology of the resulting polymer monolith was characterized by scanning electron microscopy (SEM). A solid-phase extraction (SPE) cartridge prepared from a simple glass-tube was used for the preconcentration and determination of Pb(II) combined with flame atomic absorption spectroscopy (FAAS). The characteristics of the monoliths for the extraction of Pb(II) in aqueous solution were investigated. The experimental results showed that trace Pb(II) ions could be quantitatively preconcentrated in the pH range of 4.0–9.0 with recoveries of >95%. The maximum static adsorption capacity of the monolith adsorbent was 106.8mgg−1. The column was eluted by 1.0molL−1 HNO3 and recovery of Pb(II) was more than 97%. Moreover, the polymer monolith adsorbent shows superior reusability and stability. The precision and the accuracy of the proposed procedure were satisfactory by analyzing a standard reference material and three natural water samples. It was shown that the EP–EDA monolith was suitable for the preconcentration of environmental Pb(II) as an ion-selective SPE adsorbent.
Keywords: Monolithic column; Step-addition polymerization; Epoxy resin; Preconcentration; Lead; Flame atomic absorption spectroscopy
Column preconcentration of lead in aqueous solution with macroporous epoxy resin-based polymer monolithic matrix by Sui Wang; Ruifeng Zhang (pp. 166-171).
The objective of this article was to investigate the feasibility of epoxy resin-based monoliths prepared by stepwise polymerization and column preconcentration of metal ions using large-scale monolithic matrix. A novel macroporous polymer monolith matrix was prepared from epoxy resin (EP) and ethylenediamine (EDA) and pore-forming reagent (polyethylene glycol, PEG-1000) by in situ step-addition polymerization. The morphology of the resulting polymer monolith was characterized by scanning electron microscopy (SEM). A solid-phase extraction (SPE) cartridge prepared from a simple glass-tube was used for the preconcentration and determination of Pb(II) combined with flame atomic absorption spectroscopy (FAAS). The characteristics of the monoliths for the extraction of Pb(II) in aqueous solution were investigated. The experimental results showed that trace Pb(II) ions could be quantitatively preconcentrated in the pH range of 4.0–9.0 with recoveries of >95%. The maximum static adsorption capacity of the monolith adsorbent was 106.8mgg−1. The column was eluted by 1.0molL−1 HNO3 and recovery of Pb(II) was more than 97%. Moreover, the polymer monolith adsorbent shows superior reusability and stability. The precision and the accuracy of the proposed procedure were satisfactory by analyzing a standard reference material and three natural water samples. It was shown that the EP–EDA monolith was suitable for the preconcentration of environmental Pb(II) as an ion-selective SPE adsorbent.
Keywords: Monolithic column; Step-addition polymerization; Epoxy resin; Preconcentration; Lead; Flame atomic absorption spectroscopy
Electrochemical detection of cysteine in a flow system based on reductive desorption of thiols from gold by Rodrigo Possari; Rafaela Fernanda Carvalhal; Renata Kelly Mendes; Lauro Tatsuo Kubota (pp. 172-179).
A simple strategy for cysteine determination using flow-injection analysis with electrochemical detection is described. The approach is based on the chemisorptions reactions of the sulfur moiety of cysteine upon polycrystalline gold electrodes and its subsequent reductive desorption. The electrochemical measurements were accomplished by the application of differential pulse voltammetry (DPV) for the operational optimization and pulsed electrochemical detection (PED) in combination with flow-injection analysis for the electrochemical detection as time function. The electroactive species could be adsorbed in a potential level (0.1V versus SCE), at other (−0.6V versus SCE) occurs their reductive desorption from the electrode, while the analytical current is recorded simultaneously, and a third potential step is applied to the complete regeneration of the gold electrode surface (−1.3V versus SCE). The linear response range was observed between 1.0×10−6 and 6.0×10−6molL−1 with a good reproducibility (R.S.D.<3.2%) and sensitivity (1.1μA/μM). The repeatability (a series of 27 continuous FIA peaks of 5.0μmolL−1 of cysteine) was 3.8 % and the limit of detection was 5.0×10−7molL−1. The sample throughput was 23 samples per hour with a very high stability in its voltammetric response. The developed methodology was successfully used for the determination of cysteine in commercial supplementary food sample.
Keywords: Self-assembled monolayer; Electrochemical desorption; l; -Cysteine determination; Cathodic stripping pulsed amperometry; Flow analysis
Electrochemical detection of cysteine in a flow system based on reductive desorption of thiols from gold by Rodrigo Possari; Rafaela Fernanda Carvalhal; Renata Kelly Mendes; Lauro Tatsuo Kubota (pp. 172-179).
A simple strategy for cysteine determination using flow-injection analysis with electrochemical detection is described. The approach is based on the chemisorptions reactions of the sulfur moiety of cysteine upon polycrystalline gold electrodes and its subsequent reductive desorption. The electrochemical measurements were accomplished by the application of differential pulse voltammetry (DPV) for the operational optimization and pulsed electrochemical detection (PED) in combination with flow-injection analysis for the electrochemical detection as time function. The electroactive species could be adsorbed in a potential level (0.1V versus SCE), at other (−0.6V versus SCE) occurs their reductive desorption from the electrode, while the analytical current is recorded simultaneously, and a third potential step is applied to the complete regeneration of the gold electrode surface (−1.3V versus SCE). The linear response range was observed between 1.0×10−6 and 6.0×10−6molL−1 with a good reproducibility (R.S.D.<3.2%) and sensitivity (1.1μA/μM). The repeatability (a series of 27 continuous FIA peaks of 5.0μmolL−1 of cysteine) was 3.8 % and the limit of detection was 5.0×10−7molL−1. The sample throughput was 23 samples per hour with a very high stability in its voltammetric response. The developed methodology was successfully used for the determination of cysteine in commercial supplementary food sample.
Keywords: Self-assembled monolayer; Electrochemical desorption; l; -Cysteine determination; Cathodic stripping pulsed amperometry; Flow analysis
A comparison of boron-doped diamond thin-film and Hg-coated glassy carbon electrodes for anodic stripping voltammetric determination of heavy metal ions in aqueous media by Elizabeth A. McGaw; Greg M. Swain (pp. 180-189).
The performance of boron-doped diamond (BDD) for the anodic stripping voltammetric (ASV) determination of heavy metal ions (Zn2+, Cd2+, Pb2+, Cu2+, Ag+) was compared with that of Hg-coated glassy carbon (Hg-GC). Hg has historically been the electrode of choice for ASV but there is an ongoing search for alternate electrodes and diamond is one of these. Despite the fundamentally different nature of the metal reduction and oxidation reactions on these two electrodes, BDD provides as good or superior analytical detection figures of merit when compared to Hg. The stripping peak potentials for all the metals studied were similar at both electrodes indicating that BDD is as active as Hg for metal phase formation and oxidation. Due to the more heterogeneous chemical and electrical properties across the BDD surface, the stripping peaks were broader and more asymmetric than they were for Hg-GC. The linear dynamic range for BDD was three to four orders of magnitude ( r2>0.995), similar to Hg-GC, but the sensitivity for BDD was three to five times lower. However, the lower background current and noise for BDD enabled detection limits as low as those seen for Hg-GC. The minimum concentration of each metal ion detectable (S/N≥3) with BDD was in the mid to low ppb range (e.g., 50ppb Zn2+, 1.0ppb Cd2+, 5.0ppb Pb2+, 10ppb Cu2+ and 1.0ppb Ag+). BDD exhibited an electrode-to-electrode and run-to-run variability of less than 5%, which is comparable to that for Hg-GC. The possibility of incomplete metal oxidation and metal phase detachment from BDD was investigated using double step chronoamperometry. Neither of these processes was found to occur to any appreciable extent. The results demonstrate that BDD is a viable alternate electrode to Hg for ASV.
Keywords: Diamond electrodes; Anodic stripping voltammetry; Mercury-coated glassy carbon; Trace metal ion analysis
A comparison of boron-doped diamond thin-film and Hg-coated glassy carbon electrodes for anodic stripping voltammetric determination of heavy metal ions in aqueous media by Elizabeth A. McGaw; Greg M. Swain (pp. 180-189).
The performance of boron-doped diamond (BDD) for the anodic stripping voltammetric (ASV) determination of heavy metal ions (Zn2+, Cd2+, Pb2+, Cu2+, Ag+) was compared with that of Hg-coated glassy carbon (Hg-GC). Hg has historically been the electrode of choice for ASV but there is an ongoing search for alternate electrodes and diamond is one of these. Despite the fundamentally different nature of the metal reduction and oxidation reactions on these two electrodes, BDD provides as good or superior analytical detection figures of merit when compared to Hg. The stripping peak potentials for all the metals studied were similar at both electrodes indicating that BDD is as active as Hg for metal phase formation and oxidation. Due to the more heterogeneous chemical and electrical properties across the BDD surface, the stripping peaks were broader and more asymmetric than they were for Hg-GC. The linear dynamic range for BDD was three to four orders of magnitude ( r2>0.995), similar to Hg-GC, but the sensitivity for BDD was three to five times lower. However, the lower background current and noise for BDD enabled detection limits as low as those seen for Hg-GC. The minimum concentration of each metal ion detectable (S/N≥3) with BDD was in the mid to low ppb range (e.g., 50ppb Zn2+, 1.0ppb Cd2+, 5.0ppb Pb2+, 10ppb Cu2+ and 1.0ppb Ag+). BDD exhibited an electrode-to-electrode and run-to-run variability of less than 5%, which is comparable to that for Hg-GC. The possibility of incomplete metal oxidation and metal phase detachment from BDD was investigated using double step chronoamperometry. Neither of these processes was found to occur to any appreciable extent. The results demonstrate that BDD is a viable alternate electrode to Hg for ASV.
Keywords: Diamond electrodes; Anodic stripping voltammetry; Mercury-coated glassy carbon; Trace metal ion analysis
Electrochemical behaviour of isatin at a glassy carbon electrode by Victor C. Diculescu; Sunita Kumbhat; Ana Maria Oliveira-Brett (pp. 190-197).
The electrochemical behavior of isatin – a molecule with a broad range of applications in synthetic, biological and clinical activity – has been investigated over a wide pH range at a glassy carbon electrode (GCE) using cyclic, square wave and differential pulse voltammetry. The oxidation of isatin is an irreversible process, pH dependent and occurs with the formation of a main oxidation product that strongly adsorbs on the electrode surface. The reduction of isatin is also a pH dependent irreversible process. Cyclic voltammograms show two consecutive charge transfer reactions. The diffusion coefficient of isatin was calculated in pH 7.0 phosphate buffer to be D0=4.9×10−7cm2s−1. The limit of detection obtained in a solution of pH 7.0 phosphate buffer was LOD=0.194μM, based on three times the noise level.
Keywords: Isatin; Indole; Oxidation; Reduction; Voltammetry
Electrochemical behaviour of isatin at a glassy carbon electrode by Victor C. Diculescu; Sunita Kumbhat; Ana Maria Oliveira-Brett (pp. 190-197).
The electrochemical behavior of isatin – a molecule with a broad range of applications in synthetic, biological and clinical activity – has been investigated over a wide pH range at a glassy carbon electrode (GCE) using cyclic, square wave and differential pulse voltammetry. The oxidation of isatin is an irreversible process, pH dependent and occurs with the formation of a main oxidation product that strongly adsorbs on the electrode surface. The reduction of isatin is also a pH dependent irreversible process. Cyclic voltammograms show two consecutive charge transfer reactions. The diffusion coefficient of isatin was calculated in pH 7.0 phosphate buffer to be D0=4.9×10−7cm2s−1. The limit of detection obtained in a solution of pH 7.0 phosphate buffer was LOD=0.194μM, based on three times the noise level.
Keywords: Isatin; Indole; Oxidation; Reduction; Voltammetry
A cerium(III) selective polyvinyl chloride membrane sensor based on a Schiff base complex of N, N′-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine by Vinod Kumar Gupta; A.K. Singh; Barkha Gupta (pp. 198-204).
A polyvinyl chloride (PVC) based membrane sensor for cerium ions was prepared by employing N, N′-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine as an ionophore, oleic acid (OA) as anion excluder and o-nitrophenyloctyl ether ( o-NPOE) as plasticizer. The plasticized membrane sensor exhibits a Nernstian response for Ce(III) ions over a wide concentration range (1.41×10−7 to 1.0×10−2M) with a limit of detection as low as 8.91×10−8M. It has a fast response time (<10s) and can be used for 4 months. The sensor revealed a very good selectivity with respect to common alkali, alkaline earth and heavy metal ions. The response of the proposed sensor is independent of pH between 3.0 and 8.0. It was used as an indicator electrode in potentiometric titration of fluoride, carbonate and oxalate anions and determination of cerium in simulated mixtures.
Keywords: Cerium selective electrode; Polyvinyl chloride; Membrane electrodes; Schiff base; Potentiometric sensors
A cerium(III) selective polyvinyl chloride membrane sensor based on a Schiff base complex of N, N′-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine by Vinod Kumar Gupta; A.K. Singh; Barkha Gupta (pp. 198-204).
A polyvinyl chloride (PVC) based membrane sensor for cerium ions was prepared by employing N, N′-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine as an ionophore, oleic acid (OA) as anion excluder and o-nitrophenyloctyl ether ( o-NPOE) as plasticizer. The plasticized membrane sensor exhibits a Nernstian response for Ce(III) ions over a wide concentration range (1.41×10−7 to 1.0×10−2M) with a limit of detection as low as 8.91×10−8M. It has a fast response time (<10s) and can be used for 4 months. The sensor revealed a very good selectivity with respect to common alkali, alkaline earth and heavy metal ions. The response of the proposed sensor is independent of pH between 3.0 and 8.0. It was used as an indicator electrode in potentiometric titration of fluoride, carbonate and oxalate anions and determination of cerium in simulated mixtures.
Keywords: Cerium selective electrode; Polyvinyl chloride; Membrane electrodes; Schiff base; Potentiometric sensors
Electrogenerated chemiluminescence detection for deoxyribonucleic acid hybridization based on gold nanoparticles carrying multiple probes by Hui Wang; Chengxiao Zhang; Yan Li; Honglan Qi (pp. 205-211).
A novel sensitive electrogenerated chemiluminescence (ECL) method for the detection deoxyribonucleic acid (DNA) hybridization based on gold nanoparticles carrying multiple probes was developed. Ruthenium bis(2,2′-bipyridine)(2,2′-bipyridine-4,4′-dicarboxylic acid)- N-hydroxysuccinimide ester (Ru(bpy)2(dcbpy)NHS) was used as a ECL label and gold nanoparticle as a carrier. Probe single strand DNA (ss-DNA) was self-assembled at the 3′-terminal with a thiol group to the surface of gold nanoparticle and covalently labeled at the 5′-terminal of a phosphate group with Ru(bpy)2(dcbpy)NHS and the resulting conjugate, (Ru(bpy)2(dcbpy)NHS)-ss-DNA-Au, was taken as a ECL probe. When target analyte ss-DNA was immobilized on a gold electrode by self-assembled monolayer technique and then hybridized with the ECL probe to form a double-stranded DNA (ds-DNA), a strong ECL response was electrochemically generated. The ECL intensity was linearly related to the concentration of the complementary sequence (target ss-DNA) in the range from 1.0×10−11 to 1.0×10−8molL−1, and the linear regression equation was S=57301+4579.6lg C (unit of C is molL−1). A detection limit of 5.0×10−12molL−1 for target ss-DNA was achieved. The ECL signal generated from many reporters of ECL probe prepared is greatly amplified, compared to the convention scheme which is based on one reporter per hybridization event.
Keywords: DNA; Electrogenerated chemiluminescence; Gold nanoparticles; Ruthenium bis(2,2′-bipyridine)(2,2′-bipyridine-4,4′-dicarboxylic acid)-; N; -hydroxysuccinimide ester
Electrogenerated chemiluminescence detection for deoxyribonucleic acid hybridization based on gold nanoparticles carrying multiple probes by Hui Wang; Chengxiao Zhang; Yan Li; Honglan Qi (pp. 205-211).
A novel sensitive electrogenerated chemiluminescence (ECL) method for the detection deoxyribonucleic acid (DNA) hybridization based on gold nanoparticles carrying multiple probes was developed. Ruthenium bis(2,2′-bipyridine)(2,2′-bipyridine-4,4′-dicarboxylic acid)- N-hydroxysuccinimide ester (Ru(bpy)2(dcbpy)NHS) was used as a ECL label and gold nanoparticle as a carrier. Probe single strand DNA (ss-DNA) was self-assembled at the 3′-terminal with a thiol group to the surface of gold nanoparticle and covalently labeled at the 5′-terminal of a phosphate group with Ru(bpy)2(dcbpy)NHS and the resulting conjugate, (Ru(bpy)2(dcbpy)NHS)-ss-DNA-Au, was taken as a ECL probe. When target analyte ss-DNA was immobilized on a gold electrode by self-assembled monolayer technique and then hybridized with the ECL probe to form a double-stranded DNA (ds-DNA), a strong ECL response was electrochemically generated. The ECL intensity was linearly related to the concentration of the complementary sequence (target ss-DNA) in the range from 1.0×10−11 to 1.0×10−8molL−1, and the linear regression equation was S=57301+4579.6lg C (unit of C is molL−1). A detection limit of 5.0×10−12molL−1 for target ss-DNA was achieved. The ECL signal generated from many reporters of ECL probe prepared is greatly amplified, compared to the convention scheme which is based on one reporter per hybridization event.
Keywords: DNA; Electrogenerated chemiluminescence; Gold nanoparticles; Ruthenium bis(2,2′-bipyridine)(2,2′-bipyridine-4,4′-dicarboxylic acid)-; N; -hydroxysuccinimide ester
The second chemiluminescence emission of luminol–periodate–menadione sodium bisulfite system and its analytical application by Baoxin Li; Xiaoyan Zhang; Chengxiao Zhang (pp. 212-216).
In this paper, a new chemiluminescence phenomenon described as the second chemiluminescence emission was observed when menadione sodium bisulfite was injected into a reaction mixture of luminol and potassium periodate, in which luminol was oxidized by excess amount of potassium periodate for about 24h. The mechanism of the second chemiluminescence emission was proposed based a series of experiments. Moreover, our experiment discovered that the second chemiluminescence intensity was a linear function of the concentration of menadione sodium bisulfite in the range of 2×10−9 to 4×10−5gL−1. Based on this phenomenon, a new flow-injection method for the determination of menadione sodium bisulfite has been established.
Keywords: Second chemiluminescence emission; Luminol–periodate; Menadione sodium bisulfite; Flow-injection analysis
The second chemiluminescence emission of luminol–periodate–menadione sodium bisulfite system and its analytical application by Baoxin Li; Xiaoyan Zhang; Chengxiao Zhang (pp. 212-216).
In this paper, a new chemiluminescence phenomenon described as the second chemiluminescence emission was observed when menadione sodium bisulfite was injected into a reaction mixture of luminol and potassium periodate, in which luminol was oxidized by excess amount of potassium periodate for about 24h. The mechanism of the second chemiluminescence emission was proposed based a series of experiments. Moreover, our experiment discovered that the second chemiluminescence intensity was a linear function of the concentration of menadione sodium bisulfite in the range of 2×10−9 to 4×10−5gL−1. Based on this phenomenon, a new flow-injection method for the determination of menadione sodium bisulfite has been established.
Keywords: Second chemiluminescence emission; Luminol–periodate; Menadione sodium bisulfite; Flow-injection analysis
A selective fluorescence-on reaction of spiro form fluorescein hydrazide with Cu(II) by Xinqi Chen; Huimin Ma (pp. 217-222).
The spiro form fluorescein hydrazide (1) bearing a cleavable active bond is characterized as a highly selective and sensitive fluorescence probe for Cu2+. In 0.01M Tris–HCl buffer (pH 7.2), the probe displays a highly selective fluorescence-on response to Cu2+ only, instead of other common metal ions. The reaction mechanism has been explored and proposed as that the hydrazide group of1 recognizes and binds Cu2+, and the subsequent complexation of Cu2+ promotes hydrolytic cleavage of the amide bond, causing the release of fluorophore (fluorescein) and thereby the retrievement of fluorescence. Conditions for fluorescence measurement were optimized, generating a calibration curve that is linear over the concentration range of 0.1–10μM Cu2+. The detection limit for Cu2+ is 64nM based on 11 blank determinations ( k=3), also showing a highly sensitive feature. The fluorescence-on reaction described here has been used for the determination of trace Cu2+ in real biological fluids with satisfactory results.
Keywords: Spiro form fluorescein hydrazide; Fluorescence-on reaction; Copper; Selective detection
A selective fluorescence-on reaction of spiro form fluorescein hydrazide with Cu(II) by Xinqi Chen; Huimin Ma (pp. 217-222).
The spiro form fluorescein hydrazide (1) bearing a cleavable active bond is characterized as a highly selective and sensitive fluorescence probe for Cu2+. In 0.01M Tris–HCl buffer (pH 7.2), the probe displays a highly selective fluorescence-on response to Cu2+ only, instead of other common metal ions. The reaction mechanism has been explored and proposed as that the hydrazide group of1 recognizes and binds Cu2+, and the subsequent complexation of Cu2+ promotes hydrolytic cleavage of the amide bond, causing the release of fluorophore (fluorescein) and thereby the retrievement of fluorescence. Conditions for fluorescence measurement were optimized, generating a calibration curve that is linear over the concentration range of 0.1–10μM Cu2+. The detection limit for Cu2+ is 64nM based on 11 blank determinations ( k=3), also showing a highly sensitive feature. The fluorescence-on reaction described here has been used for the determination of trace Cu2+ in real biological fluids with satisfactory results.
Keywords: Spiro form fluorescein hydrazide; Fluorescence-on reaction; Copper; Selective detection
Calibration of Phen Green™ for use as a Cu(I)-selective fluorescent indicator by Hyun-su Kim; Beth A. Ahner (pp. 223-229).
Conditional stability constants for the Cu-sensitive fluorescent dye Phen Green™ SK (PGSK) were determined for complexes containing both Cu(I) and Cu(II). Experimental conditions were optimized to minimize oxidation of Cu(I) to Cu(II). A binding constant of 1011.38 for PGSK and Cu(I) was determined using chloride as the competing ligand and an iterative procedure involving equilibrium calculations to fit experimental data. The new constant was tested by evaluating PGSK fluorescence in the presence of the strong Cu(I)–ligand neocuproine and thiourea. There was good agreement between experimental data and changes in fluorescence predicted by calculations using the new constant and published constants for the competing ligands. Using EDTA to buffer the free ion concentration of Cu2+, the conditional stability constant of PGSK with Cu(II) was measured to be 109.8. Both of these new constants are significantly higher than previously published values. Finally PGSK was used to examine the kinetics of Cu(I) dissociation from the biologically important ligand glutathione.
Keywords: Fluorescence; Copper; Indicator; Glutathione; Phen Green; Chemosensor
Calibration of Phen Green™ for use as a Cu(I)-selective fluorescent indicator by Hyun-su Kim; Beth A. Ahner (pp. 223-229).
Conditional stability constants for the Cu-sensitive fluorescent dye Phen Green™ SK (PGSK) were determined for complexes containing both Cu(I) and Cu(II). Experimental conditions were optimized to minimize oxidation of Cu(I) to Cu(II). A binding constant of 1011.38 for PGSK and Cu(I) was determined using chloride as the competing ligand and an iterative procedure involving equilibrium calculations to fit experimental data. The new constant was tested by evaluating PGSK fluorescence in the presence of the strong Cu(I)–ligand neocuproine and thiourea. There was good agreement between experimental data and changes in fluorescence predicted by calculations using the new constant and published constants for the competing ligands. Using EDTA to buffer the free ion concentration of Cu2+, the conditional stability constant of PGSK with Cu(II) was measured to be 109.8. Both of these new constants are significantly higher than previously published values. Finally PGSK was used to examine the kinetics of Cu(I) dissociation from the biologically important ligand glutathione.
Keywords: Fluorescence; Copper; Indicator; Glutathione; Phen Green; Chemosensor
Laser-induced breakdown spectroscopy for quantitative spectrochemical analysis of geological materials: Effects of the matrix and simultaneous determination by Jesús M. Anzano; Mark A. Villoria; Antonio Ruíz-Medina; Roberto J. Lasheras (pp. 230-235).
A microscopic laser-induced breakdown spectrometer was used to evaluate the analytical matrix effect commonly observed in the analysis of geological materials. Samples were analyzed in either the powder or pressed pellet forms. Calibration curves of a number of iron and aluminum compounds showed a linear relationship between the elemental concentration and peak intensity. A direct determination of elemental content can thus be made from extrapolation on these calibration curves. To investigate matrix effects, synthetic model samples were prepared from various iron and aluminum compounds spiked with SiO2 and CaCO3. The addition of these matrices had a pronounced analytical effect on those compounds prepared as pressed pellets. However, results indicated the absence of matrix effects when the samples were presented to the laser as loose powders on tape and results were compared to certified values, indicating the reliability of this approach for accurate analysis, provided the sample particle diameters are greater than ≈100μm. Finally, the simultaneous analysis of two different elements was demonstrated using powders on tape.
Keywords: Laser-induced breakdown spectroscopy; Iron; Aluminum; Powders; Pellets; Matrix effect; Geological materials
Laser-induced breakdown spectroscopy for quantitative spectrochemical analysis of geological materials: Effects of the matrix and simultaneous determination by Jesús M. Anzano; Mark A. Villoria; Antonio Ruíz-Medina; Roberto J. Lasheras (pp. 230-235).
A microscopic laser-induced breakdown spectrometer was used to evaluate the analytical matrix effect commonly observed in the analysis of geological materials. Samples were analyzed in either the powder or pressed pellet forms. Calibration curves of a number of iron and aluminum compounds showed a linear relationship between the elemental concentration and peak intensity. A direct determination of elemental content can thus be made from extrapolation on these calibration curves. To investigate matrix effects, synthetic model samples were prepared from various iron and aluminum compounds spiked with SiO2 and CaCO3. The addition of these matrices had a pronounced analytical effect on those compounds prepared as pressed pellets. However, results indicated the absence of matrix effects when the samples were presented to the laser as loose powders on tape and results were compared to certified values, indicating the reliability of this approach for accurate analysis, provided the sample particle diameters are greater than ≈100μm. Finally, the simultaneous analysis of two different elements was demonstrated using powders on tape.
Keywords: Laser-induced breakdown spectroscopy; Iron; Aluminum; Powders; Pellets; Matrix effect; Geological materials
Comparative analysis of the volatile components in cut tobacco from different locations with gas chromatography–mass spectrometry (GC–MS) and combined chemometric methods by Lan-Fang Huang; Ke-Jun Zhong; Xian-Jun Sun; Ming-Jian Wu; Ke-Long Huang; Yi-Zeng Liang; Fang-Qiu Guo; Ya-Wen Li (pp. 236-245).
A combined approach of subwindow factor analysis and orthogonal projection resolution was used to analyze the volatile components of cut tobacco samples from different sources. After extracted with simultaneous distillation and extraction method, the volatile components in cut tobacco from five different locations were detected by GC–MS. Then, the qualitative and quantitative analysis of the volatile components of cut tobacco from Changde area was completed with the help of subwindow factor analysis resolving two-dimensional original data into pure mass spectra and chromatograms. One hundred and two volatile components among 138 separated peaks were identified and quantified, accounting for about 88.90% of the total content. Finally, orthogonal projection method was used to extract the common peaks from different locations. Among the identified components, there were 74 components coexisting in five studied samples although the relative content of each component showed difference to some extent. The results showed a fair consistency in their GC–MS fingerprints. It was the first time to apply orthogonal projection method to compare different cut tobacco samples, and it reduced the burden of qualitative analysis as well as the subjectivity. The obtained results proved the combined approach powerful for the analysis of complex cut tobacco samples. The developed method can be used to compare the sameness and differences of cut tobacco from different sources and for quality control of cigarette production and materials.
Keywords: Cut tobacco; Chemometrics; Gas chromatography–mass spectrometry; Subwindow factor analysis; Orthogonal projection resolution; Common component
Comparative analysis of the volatile components in cut tobacco from different locations with gas chromatography–mass spectrometry (GC–MS) and combined chemometric methods by Lan-Fang Huang; Ke-Jun Zhong; Xian-Jun Sun; Ming-Jian Wu; Ke-Long Huang; Yi-Zeng Liang; Fang-Qiu Guo; Ya-Wen Li (pp. 236-245).
A combined approach of subwindow factor analysis and orthogonal projection resolution was used to analyze the volatile components of cut tobacco samples from different sources. After extracted with simultaneous distillation and extraction method, the volatile components in cut tobacco from five different locations were detected by GC–MS. Then, the qualitative and quantitative analysis of the volatile components of cut tobacco from Changde area was completed with the help of subwindow factor analysis resolving two-dimensional original data into pure mass spectra and chromatograms. One hundred and two volatile components among 138 separated peaks were identified and quantified, accounting for about 88.90% of the total content. Finally, orthogonal projection method was used to extract the common peaks from different locations. Among the identified components, there were 74 components coexisting in five studied samples although the relative content of each component showed difference to some extent. The results showed a fair consistency in their GC–MS fingerprints. It was the first time to apply orthogonal projection method to compare different cut tobacco samples, and it reduced the burden of qualitative analysis as well as the subjectivity. The obtained results proved the combined approach powerful for the analysis of complex cut tobacco samples. The developed method can be used to compare the sameness and differences of cut tobacco from different sources and for quality control of cigarette production and materials.
Keywords: Cut tobacco; Chemometrics; Gas chromatography–mass spectrometry; Subwindow factor analysis; Orthogonal projection resolution; Common component
Establishment of a knowledge base for identification of residual solvents in pharmaceuticals by Ying Liu; Chang-Qin Hu (pp. 246-254).
A knowledge base for identification of residual solvents in pharmaceuticals has been established using gas chromatograph–mass spectrometry (GC–MS) and gas chromatograph–Fourier transform infrared spectrometry (GC–FTIR). Sixty solvents were studied according to the guideline for residual solvents regulated by the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). The standard mass spectra library, the limit of detection (LOD) mass spectra library, the standard vapor-phase infrared spectra library, and the limit of detection (LOD) vapor-phase infrared spectra library were established and constituted the knowledge base. Using the knowledge base, the problem of qualitation, which was the difficulty of determining residual solvents, can be resolved.
Keywords: Identification; Gas chromatograph–mass spectrometry; Gas chromatograph–Fourier transform infrared spectrometry; Knowledge base; Spectra library; Residual solvents in pharmaceuticals
Establishment of a knowledge base for identification of residual solvents in pharmaceuticals by Ying Liu; Chang-Qin Hu (pp. 246-254).
A knowledge base for identification of residual solvents in pharmaceuticals has been established using gas chromatograph–mass spectrometry (GC–MS) and gas chromatograph–Fourier transform infrared spectrometry (GC–FTIR). Sixty solvents were studied according to the guideline for residual solvents regulated by the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). The standard mass spectra library, the limit of detection (LOD) mass spectra library, the standard vapor-phase infrared spectra library, and the limit of detection (LOD) vapor-phase infrared spectra library were established and constituted the knowledge base. Using the knowledge base, the problem of qualitation, which was the difficulty of determining residual solvents, can be resolved.
Keywords: Identification; Gas chromatograph–mass spectrometry; Gas chromatograph–Fourier transform infrared spectrometry; Knowledge base; Spectra library; Residual solvents in pharmaceuticals
Determination of biogenic amines in apples and wine with 8-phenyl-(4-oxy-acetic acid N-hydroxysuccinimide ester)-4, 4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza- s-indacene by high performance liquid chromatography by Jin-Shu Li; Hong Wang; Ke-Jing Huang; Hua-Shan Zhang (pp. 255-261).
A precolumn-derivatization high performance liquid chromatographic method for biogenic amine analysis has been developed. Derivatization of biogenic amines was performed with a new fluorescent reagent, 8-phenyl-(4-oxy-acetic acid N-hydroxysuccinimide ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza- s-indacene (TMPAB-OSu), which was synthesized in our lab. The derivatization conditions and the influence of elution composition on the separation were investigated. In pH 8.5 H3BO3–Na2B4O7 media, the reaction of biogenic amines with TMPAB-OSu completed at 45°C for 5min. The labeled biogenic amines were separated on an ZORBAX Eclipse XDB-C8 column (150mm×4.6mm, 5μm) and detected with fluorescence at excitation and emission wavelengths of 497 and 509nm, respectively. Detection limits of biogenic amines were 0.1–4nmolL−1, at a signal-to-noise ratio of 3. The proposed method has been applied to the quantitative determination of spermine, phenethylamine, spermidine, cadaverine and putrescine in pericarp and pulp of mature and immature apples and wine with recoveries of 95–102% and R.S.D. of 0.7–3.9.
Keywords: Biogenic amines; 8-Phenyl-(4-oxy-acetic acid; N; -hydroxysuccinimide ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-; s; -indacene; High performance liquid chromatography; Fluorescence detection
Determination of biogenic amines in apples and wine with 8-phenyl-(4-oxy-acetic acid N-hydroxysuccinimide ester)-4, 4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza- s-indacene by high performance liquid chromatography by Jin-Shu Li; Hong Wang; Ke-Jing Huang; Hua-Shan Zhang (pp. 255-261).
A precolumn-derivatization high performance liquid chromatographic method for biogenic amine analysis has been developed. Derivatization of biogenic amines was performed with a new fluorescent reagent, 8-phenyl-(4-oxy-acetic acid N-hydroxysuccinimide ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza- s-indacene (TMPAB-OSu), which was synthesized in our lab. The derivatization conditions and the influence of elution composition on the separation were investigated. In pH 8.5 H3BO3–Na2B4O7 media, the reaction of biogenic amines with TMPAB-OSu completed at 45°C for 5min. The labeled biogenic amines were separated on an ZORBAX Eclipse XDB-C8 column (150mm×4.6mm, 5μm) and detected with fluorescence at excitation and emission wavelengths of 497 and 509nm, respectively. Detection limits of biogenic amines were 0.1–4nmolL−1, at a signal-to-noise ratio of 3. The proposed method has been applied to the quantitative determination of spermine, phenethylamine, spermidine, cadaverine and putrescine in pericarp and pulp of mature and immature apples and wine with recoveries of 95–102% and R.S.D. of 0.7–3.9.
Keywords: Biogenic amines; 8-Phenyl-(4-oxy-acetic acid; N; -hydroxysuccinimide ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-; s; -indacene; High performance liquid chromatography; Fluorescence detection
A monoclonal antibody-based time-resolved fluoroimmunoassay for chloramphenicol in shrimp and chicken muscle by Jianzhong Shen; Zhen Zhang; Yan Yao; Weimin Shi; Yibing Liu; Suxia Zhang (pp. 262-266).
A time-resolved fluoroimmunoassay (TR-FIA) for determination of chloramphenicol (CAP) in shrimp and chicken muscle was developed. The method was based on a direct competitive immunoassay using europium-labeled anti-CAP monoclonal antibody (MAb) and CAP-ovalbumin as coated antigen. The limit of detection was 0.05ngg−1 and limit of quantification was 0.1ngg−1. Recoveries ranged from 101.2 to 112.5% for shrimp and 104.9 to 115.3% for chicken muscle at spiked levels of 0.1–5ngg−1, with intra-assay and inter-assay variations 8.7–14.6 and 9.6–17.8%, respectively. The results obtained by the TR-FIA and ELISA correlated well. The established TR-FIA was validated for the determination of incurred shrimp samples and confirmed by gas chromatography with microcell electron capture detector (GC-μECD).
Keywords: Time-resolved fluoroimmunoassay; Chloramphenicol; Shrimp; Chicken muscle
A monoclonal antibody-based time-resolved fluoroimmunoassay for chloramphenicol in shrimp and chicken muscle by Jianzhong Shen; Zhen Zhang; Yan Yao; Weimin Shi; Yibing Liu; Suxia Zhang (pp. 262-266).
A time-resolved fluoroimmunoassay (TR-FIA) for determination of chloramphenicol (CAP) in shrimp and chicken muscle was developed. The method was based on a direct competitive immunoassay using europium-labeled anti-CAP monoclonal antibody (MAb) and CAP-ovalbumin as coated antigen. The limit of detection was 0.05ngg−1 and limit of quantification was 0.1ngg−1. Recoveries ranged from 101.2 to 112.5% for shrimp and 104.9 to 115.3% for chicken muscle at spiked levels of 0.1–5ngg−1, with intra-assay and inter-assay variations 8.7–14.6 and 9.6–17.8%, respectively. The results obtained by the TR-FIA and ELISA correlated well. The established TR-FIA was validated for the determination of incurred shrimp samples and confirmed by gas chromatography with microcell electron capture detector (GC-μECD).
Keywords: Time-resolved fluoroimmunoassay; Chloramphenicol; Shrimp; Chicken muscle
Cadmium bioavailability and speciation using the permeation liquid membrane by Stéphane Bayen; Isabelle Worms; Nalini Parthasarathy; Kevin Wilkinson; Jacques Buffle (pp. 267-273).
The permeation liquid membrane (PLM) technique was used to evaluate cadmium speciation in media resembling natural freshwaters. A planar sheet PLM system was characterized by measuring Cd fluxes in the absence and presence of complexing agents such as citrate, malonate, nitrilotriacetate and the Suwannee River standard humic acid. Comparison with theoretical speciation calculations and the results of a Cd2+ selective electrode, showed that free Cd was correctly measured using the planar sheet PLM within the studied concentration range, i.e. 10−8 to 10−4M. The effect of pH and potentially co-transported ions on Cd transport through the PLM was also studied. An example of the ability of the hollow-fiber PLM (HFPLM) to measure free Cd in the nM range is also presented. In order to evaluate the usefulness of the technique as a predictor of bioavailability, Cd PLM measurements (fluxes) were compared to Cd biouptake (internalization flux) for a freshwater alga, Chlorella kesslerii, in the absence and presence of SRHA. The use of PLM measurements is shown to be an attractive tool to better understand Cd biouptake.
Keywords: Cadmium speciation; Permeation liquid membrane; Bioaccumulation; Free ion activity model; Natural organic matter; Stability constant
Cadmium bioavailability and speciation using the permeation liquid membrane by Stéphane Bayen; Isabelle Worms; Nalini Parthasarathy; Kevin Wilkinson; Jacques Buffle (pp. 267-273).
The permeation liquid membrane (PLM) technique was used to evaluate cadmium speciation in media resembling natural freshwaters. A planar sheet PLM system was characterized by measuring Cd fluxes in the absence and presence of complexing agents such as citrate, malonate, nitrilotriacetate and the Suwannee River standard humic acid. Comparison with theoretical speciation calculations and the results of a Cd2+ selective electrode, showed that free Cd was correctly measured using the planar sheet PLM within the studied concentration range, i.e. 10−8 to 10−4M. The effect of pH and potentially co-transported ions on Cd transport through the PLM was also studied. An example of the ability of the hollow-fiber PLM (HFPLM) to measure free Cd in the nM range is also presented. In order to evaluate the usefulness of the technique as a predictor of bioavailability, Cd PLM measurements (fluxes) were compared to Cd biouptake (internalization flux) for a freshwater alga, Chlorella kesslerii, in the absence and presence of SRHA. The use of PLM measurements is shown to be an attractive tool to better understand Cd biouptake.
Keywords: Cadmium speciation; Permeation liquid membrane; Bioaccumulation; Free ion activity model; Natural organic matter; Stability constant
Speciation measurements of uranium in alkaline waters using diffusive gradients in thin films technique by Weijia Li; Jiujiang Zhao; Chunsheng Li; Stephen Kiser; R. Jack Cornett (pp. 274-280).
This work investigated the application of diffusive gradients in thin films technique (DGT) to uranium speciation measurements in natural water. Two binding phases were examined, a commercially available affinity membrane, Whatman DE 81 (DE 81), with amino binding functional groups and the conventionally used Chelex 100 beads imbedded polyacrylamide hydrogel (Chelex) with iminodiacetate functional groups. The DGT devices assembled with the binding phases of DE 81 (DE 81 DGT) and Chelex gel (Chelex DGT) were tested both in synthetic river water solutions and in local river water. DE 81 DGT and Chelex DGT measured 80% and 75% of the total uranium in synthetic river water solution, respectively, and measured 73% and 60% of the total uranium in St. Lawrence River, Canada, respectively. The binding properties of the DE 81 membrane and Chelex gel for uranium, and the diffusion of uranyl complexes in the polyacrylamide gel (PAM) were also studied.
Keywords: Diffusive gradients in thin films (DGT); Uranium; River water
Speciation measurements of uranium in alkaline waters using diffusive gradients in thin films technique by Weijia Li; Jiujiang Zhao; Chunsheng Li; Stephen Kiser; R. Jack Cornett (pp. 274-280).
This work investigated the application of diffusive gradients in thin films technique (DGT) to uranium speciation measurements in natural water. Two binding phases were examined, a commercially available affinity membrane, Whatman DE 81 (DE 81), with amino binding functional groups and the conventionally used Chelex 100 beads imbedded polyacrylamide hydrogel (Chelex) with iminodiacetate functional groups. The DGT devices assembled with the binding phases of DE 81 (DE 81 DGT) and Chelex gel (Chelex DGT) were tested both in synthetic river water solutions and in local river water. DE 81 DGT and Chelex DGT measured 80% and 75% of the total uranium in synthetic river water solution, respectively, and measured 73% and 60% of the total uranium in St. Lawrence River, Canada, respectively. The binding properties of the DE 81 membrane and Chelex gel for uranium, and the diffusion of uranyl complexes in the polyacrylamide gel (PAM) were also studied.
Keywords: Diffusive gradients in thin films (DGT); Uranium; River water
Patterning chemical stimulation of reconstructed neuronal networks by Yulia Mourzina; Dmitry Kaliaguine; Petra Schulte; Andreas Offenhäusser (pp. 281-289).
A spatially resolved delivery of substances integrated with cell culture substrates shows promise for application in pharmacological assays, bioanalytical studies on cell signaling pathways and cell-based biosensors, where control over the extracellular biochemical environment with a cellular resolution is desirable. In this work, we studied a biohybrid system where rat embryonic cortical neuronal networks are reconstructed on microstructured silicon chips and interfaced to microfluidics. The design of cell–cell and cell–medium interactions in confined geometries is presented. We developed an aligned microcontact printing technique (AμCP) for poly(lysine)-extracellular matrix proteins on microstructured chips, which allows a high degree of geometrical control over the network architecture and alignment of the neuronal network with the microfluidic features of a substrate. Spatially resolved on-chip delivery of compounds with a cellular resolution is demonstrated by chemical stimulation of patterned rat cortical neurons within a network with a number of solutions of excitatory neurotransmitter glutamate delivered via microfluidics. The combination of the system described with a patch-clamp technique allowed both modulation of the biochemical environment on a cellular level and the monitoring of electrophysiological properties in the reconstructed rat embryonic cortical networks changed by this microenvironment.
Keywords: Microfluidic system; Reconstructed neuronal networks; Pharmacological assays; Aligned microcontact printing (AμCP)
Patterning chemical stimulation of reconstructed neuronal networks by Yulia Mourzina; Dmitry Kaliaguine; Petra Schulte; Andreas Offenhäusser (pp. 281-289).
A spatially resolved delivery of substances integrated with cell culture substrates shows promise for application in pharmacological assays, bioanalytical studies on cell signaling pathways and cell-based biosensors, where control over the extracellular biochemical environment with a cellular resolution is desirable. In this work, we studied a biohybrid system where rat embryonic cortical neuronal networks are reconstructed on microstructured silicon chips and interfaced to microfluidics. The design of cell–cell and cell–medium interactions in confined geometries is presented. We developed an aligned microcontact printing technique (AμCP) for poly(lysine)-extracellular matrix proteins on microstructured chips, which allows a high degree of geometrical control over the network architecture and alignment of the neuronal network with the microfluidic features of a substrate. Spatially resolved on-chip delivery of compounds with a cellular resolution is demonstrated by chemical stimulation of patterned rat cortical neurons within a network with a number of solutions of excitatory neurotransmitter glutamate delivered via microfluidics. The combination of the system described with a patch-clamp technique allowed both modulation of the biochemical environment on a cellular level and the monitoring of electrophysiological properties in the reconstructed rat embryonic cortical networks changed by this microenvironment.
Keywords: Microfluidic system; Reconstructed neuronal networks; Pharmacological assays; Aligned microcontact printing (AμCP)
Partial least squares-based multivariate spectral calibration method for simultaneous determination of beta-carboline derivatives in Peganum harmala seed extracts by Bahram Hemmateenejad; Abdolkarim Abbaspour; Homeyra Maghami; Ramin Miri; Mohhamad Reza Panjehshahin (pp. 290-299).
The partial least squares regression method has been applied for simultaneous spectrophotometric determination of harmine, harmane, harmalol and harmaline in Peganum harmala L. (Zygophyllaceae) seeds. The effect of pH was optimized employing multivariate definition of selectivity and sensitivity and best results were obtained in basic media (pH>9). The calibration models were optimized for number of latent variables by the cross-validation procedure. Determinations were made over the concentration range of 0.15–10μgmL−1. The proposed method was validated by applying it to the analysis of the β-carbolines in synthetic quaternary mixtures of media at pH 9 and 11. The relative standard errors of prediction were less than 4% in most cases. Analysis of P. harmala seeds by the proposed models for contents of the β-carboline derivatives resulted in 1.84%, 0.16%, 0.25% and 3.90% for harmine, harmane, harmaline and harmalol, respectively. The results were validated against an existing HPLC method and it no significant differences were observed between the results of two methods.
Keywords: Harmine; Harmane; Harmaline; Harmalol; Multivariate calibration; Partial least squares
Partial least squares-based multivariate spectral calibration method for simultaneous determination of beta-carboline derivatives in Peganum harmala seed extracts by Bahram Hemmateenejad; Abdolkarim Abbaspour; Homeyra Maghami; Ramin Miri; Mohhamad Reza Panjehshahin (pp. 290-299).
The partial least squares regression method has been applied for simultaneous spectrophotometric determination of harmine, harmane, harmalol and harmaline in Peganum harmala L. (Zygophyllaceae) seeds. The effect of pH was optimized employing multivariate definition of selectivity and sensitivity and best results were obtained in basic media (pH>9). The calibration models were optimized for number of latent variables by the cross-validation procedure. Determinations were made over the concentration range of 0.15–10μgmL−1. The proposed method was validated by applying it to the analysis of the β-carbolines in synthetic quaternary mixtures of media at pH 9 and 11. The relative standard errors of prediction were less than 4% in most cases. Analysis of P. harmala seeds by the proposed models for contents of the β-carboline derivatives resulted in 1.84%, 0.16%, 0.25% and 3.90% for harmine, harmane, harmaline and harmalol, respectively. The results were validated against an existing HPLC method and it no significant differences were observed between the results of two methods.
Keywords: Harmine; Harmane; Harmaline; Harmalol; Multivariate calibration; Partial least squares