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Analytica Chimica Acta (v.577, #2)
Development of enzyme-linked immunosorbent assays for the detection of deacetoxycephalosporin C and isopenicillin N synthase activity by Jeanette E. Stok; Jack E. Baldwin (pp. 153-162).
Although there are a number of existing assays for monitoring the activity of both isopenicillin N synthase (IPNS) and deacetoxycephalosporin C synthase (DAOCS), none have demonstrated the qualities required for screening a mutant library. Hence, enzyme-linked immunosorbent assays (ELISAs) for IPNS and DAOCS were developed based on the detection of the catalytic turnover products isopenicillin N and cephalexin/phenylacetyl-7-aminodeacetoxycephalosporanic acid (G-7-ADCA), respectively. These assays are relatively fast compared to existing assays, such as the hole-plate bioassay, and are amenable with high-throughput screening. Both the IPNS and DAOCS-ELISAs were optimised for use with crude protein extracts rather than purified protein, thereby eliminating any additional time required for purification. The ELISA developed for the detection of cephalexin had an IC50 value of 154±9ngmL−1 and LOD of 7.2±2.2ngmL−1 under conditions required for the assay. Good recoveries and correlation was observed for spiked samples when the concentration of crude protein was kept below 1mgmL−1. The DAOCS-ELISA was found to have increased sensitivity compared to the hole-plate bioassay (10.3μgmL−1). The IPNS-ELISA did not significantly increase the sensitivity (approximately 5μgmL−1) compared to that of the hole-plate bioassay (16μgmL−1) for isopenicillin N. The minimum amount of crude protein extract required for producing detectable amounts of product for both assays was below 0.5% of the maximum amount of protein that the assay could contain without any effect on the ELISA. This suggests that when screening a mutant library, mutants producing low amounts of the product could still be detected using these assays.
Keywords: Enzyme-linked immunosorbent assay; Deacetoxycephalosporin C synthase; Isopenicillin N synthase; Cephalexin; Ampicillin; Isopenicillin N; Penicillin G; High-throughputAbbreviations; IPNS; isopenicillin N synthase; ACV; l; -δ-(α-aminoadipoyl)-; l; -cysteinyl-; d; -valine; DAOCS; deacetoxycephalosporin C synthase; G-7-ADCA; phenylacetyl-7-aminodeacetoxycephalosporanic acid; BSA; bovine serum albumin; OVA; ovalbumin; 6-APA; 6-aminopenicillanic acid; EDC hydrochloride; N; -(3-dimethylaminopropyl)-; N; ′-ethylcarbodiimide hydrochloride; DCM; dichloromethane; PBS; phosphate buffered saline; 2-OG; 2-oxoglutarate; ELISA; enzyme-linked immunosorbent assay; HPLC; high-pressure liquid chromatography; IC; 50; concentration of antigen required to inhibit 50% of the antisera; LOD; limit of detection
Development of enzyme-linked immunosorbent assays for the detection of deacetoxycephalosporin C and isopenicillin N synthase activity by Jeanette E. Stok; Jack E. Baldwin (pp. 153-162).
Although there are a number of existing assays for monitoring the activity of both isopenicillin N synthase (IPNS) and deacetoxycephalosporin C synthase (DAOCS), none have demonstrated the qualities required for screening a mutant library. Hence, enzyme-linked immunosorbent assays (ELISAs) for IPNS and DAOCS were developed based on the detection of the catalytic turnover products isopenicillin N and cephalexin/phenylacetyl-7-aminodeacetoxycephalosporanic acid (G-7-ADCA), respectively. These assays are relatively fast compared to existing assays, such as the hole-plate bioassay, and are amenable with high-throughput screening. Both the IPNS and DAOCS-ELISAs were optimised for use with crude protein extracts rather than purified protein, thereby eliminating any additional time required for purification. The ELISA developed for the detection of cephalexin had an IC50 value of 154±9ngmL−1 and LOD of 7.2±2.2ngmL−1 under conditions required for the assay. Good recoveries and correlation was observed for spiked samples when the concentration of crude protein was kept below 1mgmL−1. The DAOCS-ELISA was found to have increased sensitivity compared to the hole-plate bioassay (10.3μgmL−1). The IPNS-ELISA did not significantly increase the sensitivity (approximately 5μgmL−1) compared to that of the hole-plate bioassay (16μgmL−1) for isopenicillin N. The minimum amount of crude protein extract required for producing detectable amounts of product for both assays was below 0.5% of the maximum amount of protein that the assay could contain without any effect on the ELISA. This suggests that when screening a mutant library, mutants producing low amounts of the product could still be detected using these assays.
Keywords: Enzyme-linked immunosorbent assay; Deacetoxycephalosporin C synthase; Isopenicillin N synthase; Cephalexin; Ampicillin; Isopenicillin N; Penicillin G; High-throughputAbbreviations; IPNS; isopenicillin N synthase; ACV; l; -δ-(α-aminoadipoyl)-; l; -cysteinyl-; d; -valine; DAOCS; deacetoxycephalosporin C synthase; G-7-ADCA; phenylacetyl-7-aminodeacetoxycephalosporanic acid; BSA; bovine serum albumin; OVA; ovalbumin; 6-APA; 6-aminopenicillanic acid; EDC hydrochloride; N; -(3-dimethylaminopropyl)-; N; ′-ethylcarbodiimide hydrochloride; DCM; dichloromethane; PBS; phosphate buffered saline; 2-OG; 2-oxoglutarate; ELISA; enzyme-linked immunosorbent assay; HPLC; high-pressure liquid chromatography; IC; 50; concentration of antigen required to inhibit 50% of the antisera; LOD; limit of detection
Real-time observation of temperature-dependent protein–protein interactions using real-time dual-color detection system by Daekwang Kim; Yong-Geun Kwak; Seong Ho Kang (pp. 163-170).
This study examined the ability of a real-time dual-color detection system to allow direct observations of the kinetics of temperature-dependent protein–protein interaction at a single-molecule level. The primary target protein was an Alexa Fluor® 488-labeled actin conjugate, which had been pre-incubated with an unlabeled rabbit anti-actin antibody (IgG). The complementary fluorescent protein was Alexa Fluor® 633-labeled goat anti-rabbit IgG antibody, which interacts with the rabbit anti-actin antibody (IgG) bound to the Alexa Fluor® 488-labeled actin conjugate. The individual protein molecules labeled with different fluorescent dyes in solution were effectively focused, interacted with the other protein molecules at 500aM, and detected directly in real-time using the dual-wavelength ( λex=488 and 635nm) laser-induced fluorescence detection system. The kinetics of the protein–protein interactions were examined at different temperatures (12–32°C). At concentrations in the aM range, the number of bound complex molecules through the protein–protein interaction decreased gradually with time at a given temperature, and increased with decreasing temperature at a set time. A high concentration (above 500pM) of the protein sample caused aggregation and nonspecific binding of the protein molecules, even though the protein molecules were not an example of complementary binding. The results demonstrated that the real-time kinetics of a protein–protein interaction could be analyzed effectively at the single-molecule level without any time delay using the real-time dual-color detection system.
Keywords: Kinetics; Protein–protein interaction; Real-time dual-color detection; Single-molecule detection
Real-time observation of temperature-dependent protein–protein interactions using real-time dual-color detection system by Daekwang Kim; Yong-Geun Kwak; Seong Ho Kang (pp. 163-170).
This study examined the ability of a real-time dual-color detection system to allow direct observations of the kinetics of temperature-dependent protein–protein interaction at a single-molecule level. The primary target protein was an Alexa Fluor® 488-labeled actin conjugate, which had been pre-incubated with an unlabeled rabbit anti-actin antibody (IgG). The complementary fluorescent protein was Alexa Fluor® 633-labeled goat anti-rabbit IgG antibody, which interacts with the rabbit anti-actin antibody (IgG) bound to the Alexa Fluor® 488-labeled actin conjugate. The individual protein molecules labeled with different fluorescent dyes in solution were effectively focused, interacted with the other protein molecules at 500aM, and detected directly in real-time using the dual-wavelength ( λex=488 and 635nm) laser-induced fluorescence detection system. The kinetics of the protein–protein interactions were examined at different temperatures (12–32°C). At concentrations in the aM range, the number of bound complex molecules through the protein–protein interaction decreased gradually with time at a given temperature, and increased with decreasing temperature at a set time. A high concentration (above 500pM) of the protein sample caused aggregation and nonspecific binding of the protein molecules, even though the protein molecules were not an example of complementary binding. The results demonstrated that the real-time kinetics of a protein–protein interaction could be analyzed effectively at the single-molecule level without any time delay using the real-time dual-color detection system.
Keywords: Kinetics; Protein–protein interaction; Real-time dual-color detection; Single-molecule detection
A microfluidic protease activity assay based on the detection of fluorescence polarization by Jung Hwan Kim; Hyun Joon Shin; Hyunju Cho; Seung Min Kwak; Hansang Cho; Tae Song Kim; Ji Yoon Kang; Eun Gyeong Yang (pp. 171-177).
This article describes a fluorescence polarization (FP)-based protease assay on a microfluidic device that is compatible with fast and reproducible analyses of protease activities. The optical systems were arranged for simultaneously measuring fluorescence intensities of vertical and horizontal polarization planes, and the binding of tetramethylrhodamine (TMR) labeled-biotin with streptavidin was utilized for optimizing FP detection in continuously flowing solutions within 74-μm wide, 12-μm deep microchannels of a glass chip. In developing off-chip FP-based assays for proteinase K, trypsin, papain and elastase, TMR conjugated-casein protein (TMR-α-casein) was employed as a universal substrate. After optimization of the hydrodynamic flow control to allow complete mixing of TMR-α-casein and short proteolysis time as possible, and of buffer composition to minimize protein sticking problems, the developed assay was transferred to the microfluidic chip by monitoring FP changes of TMR-α-casein in the main microchannel. The results indicate that the proposed device would serve as an integrated microfluidic platform with automated injection of reacting species, diffusion-controlled mixing, reaction and detection for protease activities without the need to separate the products.
Keywords: Protease assay; Interaction analyses; Fluorescence polarization; Microfluidic device; Activity screening system
A microfluidic protease activity assay based on the detection of fluorescence polarization by Jung Hwan Kim; Hyun Joon Shin; Hyunju Cho; Seung Min Kwak; Hansang Cho; Tae Song Kim; Ji Yoon Kang; Eun Gyeong Yang (pp. 171-177).
This article describes a fluorescence polarization (FP)-based protease assay on a microfluidic device that is compatible with fast and reproducible analyses of protease activities. The optical systems were arranged for simultaneously measuring fluorescence intensities of vertical and horizontal polarization planes, and the binding of tetramethylrhodamine (TMR) labeled-biotin with streptavidin was utilized for optimizing FP detection in continuously flowing solutions within 74-μm wide, 12-μm deep microchannels of a glass chip. In developing off-chip FP-based assays for proteinase K, trypsin, papain and elastase, TMR conjugated-casein protein (TMR-α-casein) was employed as a universal substrate. After optimization of the hydrodynamic flow control to allow complete mixing of TMR-α-casein and short proteolysis time as possible, and of buffer composition to minimize protein sticking problems, the developed assay was transferred to the microfluidic chip by monitoring FP changes of TMR-α-casein in the main microchannel. The results indicate that the proposed device would serve as an integrated microfluidic platform with automated injection of reacting species, diffusion-controlled mixing, reaction and detection for protease activities without the need to separate the products.
Keywords: Protease assay; Interaction analyses; Fluorescence polarization; Microfluidic device; Activity screening system
Square wave anodic stripping voltammetric determination of Pb2+ using acetylene black paste electrode based on the inducing adsorption ability of I− by Gang Li; Zhiming Ji; Kangbing Wu (pp. 178-182).
Herein, a sensitive and simplified electrochemical method was proposed for the determination of trace levels of Pb2+ by anodic stripping voltammetry (ASV) based on the inducing adsorption ability of I− toward Pb2+. In the presence of low concentration of I−, Pb2+ was induced to accumulate onto the acetylene black (AB) paste electrode surface, and then reduced at −0.90V. During the following square wave sweep from −0.90 to −0.30V, the reduced Pb was oxidized, resulting in a sensitive and well-shaped stripping peak at −0.56V. Further studies indicate that low concentration of I− significantly enhances the sensitivity of determination of Pb2+. After all the experimental parameters were optimized, a novel and sensitive method was developed for the electrochemical determination of Pb2+. The linear range is found to be from 2.0×10−8 to 4.0×10−6molL−1, and the lowest detectable concentration is estimated to be 6.0×10−9molL−1. This newly proposed method was finally demonstrated with water samples. Otherwise, the anodic stripping responses of Pb2+ on AB paste electrode and graphite paste electrode were compared.
Keywords: Lead; Electrochemical determination; Anodic stripping voltammetry; Acetylene black; Inducing adsorption
Square wave anodic stripping voltammetric determination of Pb2+ using acetylene black paste electrode based on the inducing adsorption ability of I− by Gang Li; Zhiming Ji; Kangbing Wu (pp. 178-182).
Herein, a sensitive and simplified electrochemical method was proposed for the determination of trace levels of Pb2+ by anodic stripping voltammetry (ASV) based on the inducing adsorption ability of I− toward Pb2+. In the presence of low concentration of I−, Pb2+ was induced to accumulate onto the acetylene black (AB) paste electrode surface, and then reduced at −0.90V. During the following square wave sweep from −0.90 to −0.30V, the reduced Pb was oxidized, resulting in a sensitive and well-shaped stripping peak at −0.56V. Further studies indicate that low concentration of I− significantly enhances the sensitivity of determination of Pb2+. After all the experimental parameters were optimized, a novel and sensitive method was developed for the electrochemical determination of Pb2+. The linear range is found to be from 2.0×10−8 to 4.0×10−6molL−1, and the lowest detectable concentration is estimated to be 6.0×10−9molL−1. This newly proposed method was finally demonstrated with water samples. Otherwise, the anodic stripping responses of Pb2+ on AB paste electrode and graphite paste electrode were compared.
Keywords: Lead; Electrochemical determination; Anodic stripping voltammetry; Acetylene black; Inducing adsorption
Analytical applications of a carbon nanotubes composite modified with copper microparticles as detector in flow systems by Alberto Sánchez Arribas; Esperanza Bermejo; Manuel Chicharro; Antonio Zapardiel; Guillermina L. Luque; Nancy F. Ferreyra; Gustavo A. Rivas (pp. 183-189).
In this work we report on the successful use of a composite prepared by dispersion of multi-wall carbon nanotubes (1–5μm length, 20–50nm diameter) and copper microparticles within mineral oil as detector for amino acids quantification in flow injection analysis and capillary electrophoresis. The resulting electrode displays a highly sensitive amperometric detection of amino acids, based on the copper dissolution facilitated by the strong activity of amino acids as ligands of Cu(II). The sensor makes possible the detection of amino acids, electroactive or not, at very low potentials (0.000V) and physiological pH. A correlation between the sensitivity for the amino acids and the amount of copper within the composite is observed, demonstrating the importance of the metal in the sensor response. The best analytical performance is obtained for the electrode containing 12.0% (w/w) copper. The excellent results obtained with the carbon nanotube paste electrodes containing copper (CNTPE-Cu) as detector in flow systems makes them an interesting alternative for further analytical applications involving different bioanalytes.
Keywords: Carbon nanotubes; Composite; Copper; Amino acids; Flow Injection; Capillary zone electrophoresis
Analytical applications of a carbon nanotubes composite modified with copper microparticles as detector in flow systems by Alberto Sánchez Arribas; Esperanza Bermejo; Manuel Chicharro; Antonio Zapardiel; Guillermina L. Luque; Nancy F. Ferreyra; Gustavo A. Rivas (pp. 183-189).
In this work we report on the successful use of a composite prepared by dispersion of multi-wall carbon nanotubes (1–5μm length, 20–50nm diameter) and copper microparticles within mineral oil as detector for amino acids quantification in flow injection analysis and capillary electrophoresis. The resulting electrode displays a highly sensitive amperometric detection of amino acids, based on the copper dissolution facilitated by the strong activity of amino acids as ligands of Cu(II). The sensor makes possible the detection of amino acids, electroactive or not, at very low potentials (0.000V) and physiological pH. A correlation between the sensitivity for the amino acids and the amount of copper within the composite is observed, demonstrating the importance of the metal in the sensor response. The best analytical performance is obtained for the electrode containing 12.0% (w/w) copper. The excellent results obtained with the carbon nanotube paste electrodes containing copper (CNTPE-Cu) as detector in flow systems makes them an interesting alternative for further analytical applications involving different bioanalytes.
Keywords: Carbon nanotubes; Composite; Copper; Amino acids; Flow Injection; Capillary zone electrophoresis
Screening and identification of multi-component in Qingkailing injection using combination of liquid chromatography/time-of-flight mass spectrometry and liquid chromatography/ion trap mass spectrometry by Hong-Yang Zhang; Ping Hu; Guo-An Luo; Qiong-Lin Liang; Yu-Li Wang; Shi-Kai Yan; Yi-Ming Wang (pp. 190-200).
An approach for screening and identification of multi-component in complex traditional Chinese medicine systems with a combinative LC/MS (MS n) technique was described in this paper. The chemical profile of Qingkailing injection, a well-known traditional Chinese formula in China, was studied using the established method as for an application. Benefit from combining the accurate mass measurement of LC/TOF-MS to generate elemental compositions and the complementary multilevel structural information provided by LC/ion trap MS n, 33 components in Qingkailing injection were identified in all. The three isomers of chlorogenic acid, isochlorogenic acid and neochlorogenic acid which are derived from Flos Lonicerae, one of the medicinal materials in Qingkailing, were differentiated by verifying their MS3 fragmentation data. All the components identified were surveyed and classified according to their medicinal materials derivation. This study is expected to provide an effective and reliable pattern for comprehensive and systematic characterization of the complex traditional Chinese medicine systems.
Keywords: Qingkailing; injection; Identification; Mass spectrometry; Electrospray; Time-of-flight; Ion trap
Screening and identification of multi-component in Qingkailing injection using combination of liquid chromatography/time-of-flight mass spectrometry and liquid chromatography/ion trap mass spectrometry by Hong-Yang Zhang; Ping Hu; Guo-An Luo; Qiong-Lin Liang; Yu-Li Wang; Shi-Kai Yan; Yi-Ming Wang (pp. 190-200).
An approach for screening and identification of multi-component in complex traditional Chinese medicine systems with a combinative LC/MS (MS n) technique was described in this paper. The chemical profile of Qingkailing injection, a well-known traditional Chinese formula in China, was studied using the established method as for an application. Benefit from combining the accurate mass measurement of LC/TOF-MS to generate elemental compositions and the complementary multilevel structural information provided by LC/ion trap MS n, 33 components in Qingkailing injection were identified in all. The three isomers of chlorogenic acid, isochlorogenic acid and neochlorogenic acid which are derived from Flos Lonicerae, one of the medicinal materials in Qingkailing, were differentiated by verifying their MS3 fragmentation data. All the components identified were surveyed and classified according to their medicinal materials derivation. This study is expected to provide an effective and reliable pattern for comprehensive and systematic characterization of the complex traditional Chinese medicine systems.
Keywords: Qingkailing; injection; Identification; Mass spectrometry; Electrospray; Time-of-flight; Ion trap
Simple and sensitive liquid chromatographic method with fluorimetric detection for the analysis of γ-amino- n-butyric acid in human urine by Chun-Yu Hsieh; Eing-Mei Tsai; Hsin-Lung Wu (pp. 201-206).
A simple and sensitive liquid chromatographic method is described for the analysis of γ-amino- n-butyric acid (GABA) in human urine. GABA is increased in the urine of cancer patients and could be used as a biomarker in the diagnosis and treatment of related patients. The method is based on derivatizing GABA with a fluorescent reagent (naproxen acyl chloride) for transforming the non-chromophoric GABA to a derivative with chromophoric and fluorophoric properties. The resulting derivative is highly responsive to a fluorimetric detector ( λex=230nm, λem=350nm). The lower quantitation of the method is attainable at 100nM GABA with a detection limit about 10nM (S/N=3 with 20μL injected). Application of the method to the analysis of GABA in the urine of patients with ovarian and uterine cancer was demonstrated.
Keywords: γ-Amino-; n; -butyric acid; Biomarker; Human urine; Liquid chromatography
Simple and sensitive liquid chromatographic method with fluorimetric detection for the analysis of γ-amino- n-butyric acid in human urine by Chun-Yu Hsieh; Eing-Mei Tsai; Hsin-Lung Wu (pp. 201-206).
A simple and sensitive liquid chromatographic method is described for the analysis of γ-amino- n-butyric acid (GABA) in human urine. GABA is increased in the urine of cancer patients and could be used as a biomarker in the diagnosis and treatment of related patients. The method is based on derivatizing GABA with a fluorescent reagent (naproxen acyl chloride) for transforming the non-chromophoric GABA to a derivative with chromophoric and fluorophoric properties. The resulting derivative is highly responsive to a fluorimetric detector ( λex=230nm, λem=350nm). The lower quantitation of the method is attainable at 100nM GABA with a detection limit about 10nM (S/N=3 with 20μL injected). Application of the method to the analysis of GABA in the urine of patients with ovarian and uterine cancer was demonstrated.
Keywords: γ-Amino-; n; -butyric acid; Biomarker; Human urine; Liquid chromatography
Determination of isatin and monoamine neurotransmitters in rat brain with liquid chromatography using palladium hexacyanoferrate modified electrode by Haihong Xu; Dan Wang; Wen Zhang; Wei Zhu; Katsunobu Yamamoto; Litong Jin (pp. 207-213).
The fabrication and application of a novel electrochemical detector (ED) with palladium hexacyanoferrate (PdHCF) chemically modified electrode (CME) for liquid chromatography (LC) were described. The electrochemical behaviors of isatin, monoamine neurotransmitters and their metabolites at this CME were investigated by cyclic voltammetry. It was found that the CME exhibited efficiently electrocatalytic of isatin and showed high sensitivity and stability for determination of monoamine neurotransmitters. The linear ranges were over three orders of magnitude and the detection limits were 2.5×10−8molL−1 for isatin, 2.5×10−10molL−1 for norepinephrine (NE), 2.5×10−10molL−1 for 5-hydroxyindoleacetic acid (5-HIAA), 5.0×10−10molL−1 for dopamine (DA), 1.0×10−9molL−1 for 3,4-dihydroxyphenylacetic acid (DOPAC), 1.2×10−10molL−1 for 5-hydroxytryptamine (5-HT) and 2.5×10−9molL−1 for homovanillic acid (HVA). Combined with microdialysis, the method was successfully applied to study the effect of isatin on the levels of monoamine neurotransmitters in experimental Parkinsonian rats. The results showed that isatin could significantly increase striatal monoamine neurotransmitters release to the basal level.
Keywords: Isatin; Palladium hexacyanoferrate; Monoamine neurotransmitters; Parkinson's disease; High performance liquid chromatography-electrochemical detection
Determination of isatin and monoamine neurotransmitters in rat brain with liquid chromatography using palladium hexacyanoferrate modified electrode by Haihong Xu; Dan Wang; Wen Zhang; Wei Zhu; Katsunobu Yamamoto; Litong Jin (pp. 207-213).
The fabrication and application of a novel electrochemical detector (ED) with palladium hexacyanoferrate (PdHCF) chemically modified electrode (CME) for liquid chromatography (LC) were described. The electrochemical behaviors of isatin, monoamine neurotransmitters and their metabolites at this CME were investigated by cyclic voltammetry. It was found that the CME exhibited efficiently electrocatalytic of isatin and showed high sensitivity and stability for determination of monoamine neurotransmitters. The linear ranges were over three orders of magnitude and the detection limits were 2.5×10−8molL−1 for isatin, 2.5×10−10molL−1 for norepinephrine (NE), 2.5×10−10molL−1 for 5-hydroxyindoleacetic acid (5-HIAA), 5.0×10−10molL−1 for dopamine (DA), 1.0×10−9molL−1 for 3,4-dihydroxyphenylacetic acid (DOPAC), 1.2×10−10molL−1 for 5-hydroxytryptamine (5-HT) and 2.5×10−9molL−1 for homovanillic acid (HVA). Combined with microdialysis, the method was successfully applied to study the effect of isatin on the levels of monoamine neurotransmitters in experimental Parkinsonian rats. The results showed that isatin could significantly increase striatal monoamine neurotransmitters release to the basal level.
Keywords: Isatin; Palladium hexacyanoferrate; Monoamine neurotransmitters; Parkinson's disease; High performance liquid chromatography-electrochemical detection
Determination of atrazine and simazine in water samples by high-performance liquid chromatography after preconcentration with heat-treated diatomaceous earth by Hideyuki Katsumata; Satoshi Kaneco; Tohru Suzuki; Kiyohisa Ohta (pp. 214-219).
A sensitive and selective column adsorption method is proposed for the preconcentration and determination of atrazine and simazine. Atrazine and simazine were preconcentrated on heat-treated diatomaceous earth as an adsorbent and then determined by high-performance liquid chromatography (HPLC). Several parameters on the recoveries of the analytes were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 2 using 100mL of validation solution containing 1.5μg of triazines and 5mL of ethanol as an eluent. Recoveries of atrazine and simazine were 95.7±4.2% and 75.0±1.9% with a relative standard deviation for seven determinations of 4.7% and 2.7% under optimum conditions. The maximum preconcentration factor was 100 for triazines when 500mL of sample solution volume was used. The linear ranges of calibration curves for atrazine and simazine were 1–150ngmL−1 and 1–300ngmL−1, respectively, with correlation coefficients of 0.999 and the detection limits (3Signal-to-Noise) were 0.24ngmL−1 and 0.21ngmL−1 for atrazine and simazine. The capacity of the adsorbent was also examined and found to be 0.8mgg−1 and 1.3mgg−1 for atrazine and simazine, respectively. The proposed method was successfully applied to the determination of triazines in river water and tap water samples with high precision and accuracy.
Keywords: Atrazine; Simazine; Preconcentration; Adsorption; Heat-treated diatomaceous earth
Determination of atrazine and simazine in water samples by high-performance liquid chromatography after preconcentration with heat-treated diatomaceous earth by Hideyuki Katsumata; Satoshi Kaneco; Tohru Suzuki; Kiyohisa Ohta (pp. 214-219).
A sensitive and selective column adsorption method is proposed for the preconcentration and determination of atrazine and simazine. Atrazine and simazine were preconcentrated on heat-treated diatomaceous earth as an adsorbent and then determined by high-performance liquid chromatography (HPLC). Several parameters on the recoveries of the analytes were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 2 using 100mL of validation solution containing 1.5μg of triazines and 5mL of ethanol as an eluent. Recoveries of atrazine and simazine were 95.7±4.2% and 75.0±1.9% with a relative standard deviation for seven determinations of 4.7% and 2.7% under optimum conditions. The maximum preconcentration factor was 100 for triazines when 500mL of sample solution volume was used. The linear ranges of calibration curves for atrazine and simazine were 1–150ngmL−1 and 1–300ngmL−1, respectively, with correlation coefficients of 0.999 and the detection limits (3Signal-to-Noise) were 0.24ngmL−1 and 0.21ngmL−1 for atrazine and simazine. The capacity of the adsorbent was also examined and found to be 0.8mgg−1 and 1.3mgg−1 for atrazine and simazine, respectively. The proposed method was successfully applied to the determination of triazines in river water and tap water samples with high precision and accuracy.
Keywords: Atrazine; Simazine; Preconcentration; Adsorption; Heat-treated diatomaceous earth
A new tool for inorganic nitrogen speciation study: Simultaneous determination of ammonium ion, nitrite and nitrate by ion chromatography with post-column ammonium derivatization by Nessler reagent and diode-array detection in rain water samples by Przemysław Niedzielski; Iwona Kurzyca; Jerzy Siepak (pp. 220-224).
The paper presents a new method for a simultaneous determination of inorganic nitrogen species in the oxidized (NO2−, NO3−) and reduced (NH4+) form in rain water samples. The method is based on a system of nitrogen species separation employing ion exchange and diode-array detection. The ions are separated in a strong ion-exchanger, nitrites and nitrates are determined directly at 208 and 205nm, respectively, while the ammonium ions are determined in the column hold-up time after a post-column derivatization by the Nessler reagent, at 425nm. The use of a diode-array detector permits a simultaneous identification of the inorganic nitrogen species in 8min. The detection limits obtained are: NO2−, 0.1mgL−1; NO3−, 0.05mgL−1; NH4+, 1mgL−1. The method proposed has been successfully used for speciation analysis of inorganic nitrogen in precipitation.
Keywords: Ion chromatography; Speciation analysis; Ammonium ion; Nitrite; Nitrate
A new tool for inorganic nitrogen speciation study: Simultaneous determination of ammonium ion, nitrite and nitrate by ion chromatography with post-column ammonium derivatization by Nessler reagent and diode-array detection in rain water samples by Przemysław Niedzielski; Iwona Kurzyca; Jerzy Siepak (pp. 220-224).
The paper presents a new method for a simultaneous determination of inorganic nitrogen species in the oxidized (NO2−, NO3−) and reduced (NH4+) form in rain water samples. The method is based on a system of nitrogen species separation employing ion exchange and diode-array detection. The ions are separated in a strong ion-exchanger, nitrites and nitrates are determined directly at 208 and 205nm, respectively, while the ammonium ions are determined in the column hold-up time after a post-column derivatization by the Nessler reagent, at 425nm. The use of a diode-array detector permits a simultaneous identification of the inorganic nitrogen species in 8min. The detection limits obtained are: NO2−, 0.1mgL−1; NO3−, 0.05mgL−1; NH4+, 1mgL−1. The method proposed has been successfully used for speciation analysis of inorganic nitrogen in precipitation.
Keywords: Ion chromatography; Speciation analysis; Ammonium ion; Nitrite; Nitrate
Selective solid-phase extraction of nickel(II) using a surface-imprinted silica gel sorbent by Na Jiang; Xijun Chang; Hong Zheng; Qun He; Zheng Hu (pp. 225-231).
A new Ni(II)-imprinted amino-functionalized silica gel sorbent with excellent selectivity for nickel(II) was prepared by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction (SPE) of trace Ni(II) in water samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Ni(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Ni(II) was 12.61 and 4.25mgg−1, respectively. The relatively selective factor ( αr) values of Ni(II)/Cu(II), Ni(II)/Co(II), Ni(II)/Zn(II) and Ni(II)/Pd(II) were 45.99, 32.83, 43.79 and 28.36, which were greater than 1. The distribution ratio ( D) values of Ni(II)-imprinted polymers for Ni(II) were greatly larger than that for Cu(II), Co(II), Zn(II) and Pd(II). The detection limit (3 σ) was 0.16ngmL−1. The relative standard deviation of the method was 1.48% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08618 and GBW 08402), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace nickel in plants and water samples with satisfactory results.
Keywords: Nickel(II)-imprinted amino-functionalized silica gel sorbent; Preparation; Solid-phase extraction (SPE); Inductively coupled plasma atomic emission spectrometry (ICP-AES); Surface imprinting technique
Selective solid-phase extraction of nickel(II) using a surface-imprinted silica gel sorbent by Na Jiang; Xijun Chang; Hong Zheng; Qun He; Zheng Hu (pp. 225-231).
A new Ni(II)-imprinted amino-functionalized silica gel sorbent with excellent selectivity for nickel(II) was prepared by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction (SPE) of trace Ni(II) in water samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Ni(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Ni(II) was 12.61 and 4.25mgg−1, respectively. The relatively selective factor ( αr) values of Ni(II)/Cu(II), Ni(II)/Co(II), Ni(II)/Zn(II) and Ni(II)/Pd(II) were 45.99, 32.83, 43.79 and 28.36, which were greater than 1. The distribution ratio ( D) values of Ni(II)-imprinted polymers for Ni(II) were greatly larger than that for Cu(II), Co(II), Zn(II) and Pd(II). The detection limit (3 σ) was 0.16ngmL−1. The relative standard deviation of the method was 1.48% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08618 and GBW 08402), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace nickel in plants and water samples with satisfactory results.
Keywords: Nickel(II)-imprinted amino-functionalized silica gel sorbent; Preparation; Solid-phase extraction (SPE); Inductively coupled plasma atomic emission spectrometry (ICP-AES); Surface imprinting technique
Determination of selected polychlorinated biphenyls in soil by miniaturised ultrasonic solvent extraction and gas chromatography-mass-selective detection by Mehmet Emin Aydin; Ali Tor; Senar Özcan (pp. 232-237).
Miniaturised ultrasonic solvent extraction procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in soil samples by gas chromatography-mass-selective detection by using 23 factorial experimental design. Recoveries of PCBs from fortified soil samples are over 90% for three different fortification levels between 40 and 120μgkg−1, and relative standard deviations of the recoveries are below 7%. The limits of detection (LODs) ranged from 0.003 to 0.006μgkg−1. The performance of the proposed method was compared to traditional shake flask extraction method on the spiked real soil sample and extraction methods showed comparable efficiencies. Proposed miniaturised ultrasonic solvent extraction offers several advantages, i.e., reducing sample requirement for measurement of target compound, less solvent consumption and reducing the costs associated with solvent purchase and waste disposal.
Keywords: Micro-scale extraction; Ultrasonic solvent extraction; Polychlorinated biphenyls; Soil; Factorial design
Determination of selected polychlorinated biphenyls in soil by miniaturised ultrasonic solvent extraction and gas chromatography-mass-selective detection by Mehmet Emin Aydin; Ali Tor; Senar Özcan (pp. 232-237).
Miniaturised ultrasonic solvent extraction procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in soil samples by gas chromatography-mass-selective detection by using 23 factorial experimental design. Recoveries of PCBs from fortified soil samples are over 90% for three different fortification levels between 40 and 120μgkg−1, and relative standard deviations of the recoveries are below 7%. The limits of detection (LODs) ranged from 0.003 to 0.006μgkg−1. The performance of the proposed method was compared to traditional shake flask extraction method on the spiked real soil sample and extraction methods showed comparable efficiencies. Proposed miniaturised ultrasonic solvent extraction offers several advantages, i.e., reducing sample requirement for measurement of target compound, less solvent consumption and reducing the costs associated with solvent purchase and waste disposal.
Keywords: Micro-scale extraction; Ultrasonic solvent extraction; Polychlorinated biphenyls; Soil; Factorial design
Laser induced thermal lens spectrometry for cobalt determination after cloud point extraction by Farzaneh Shemirani; Nader Shokoufi (pp. 238-243).
A new approach, employing cloud point extraction (CPE) in combination with thermal lens spectrometry (TLS), has been developed for the determination of cobalt. The CPE and TLS methods have good matching conditions for combination because TLS is suitable for low volume samples obtained after CPE and for organic solvents, which are used for dissolving the remaining analyte phase.1-(2-Pyridylazo)-2-naphthol (PAN) was used as a complexing agent and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant; then the pH of solution was adjusted. After phase separation at 50°C based on the cloud point extraction of the mixture, the surfactant-rich phase was dried and the remaining phase was dissolved using 20μL of carbon tetrachloride. The obtained solution was introduced into the quartz micro cell and the analyte was determined by thermal lens spectrometry. The He–Ne laser (632.8nm) was used as both the probe and the excite source.Under optimum conditions, the analytical curve was linear for the concentration range of 0.2–40ngmL−1 and the detection limit was 0.03ngmL−1. The enhancement factor of 470 was achieved for a 10mL sample. Relative standard deviations were lower than 5%.The method was successfully applied to the extraction and determination of cobalt in tap, river and sea water.
Keywords: Thermal lens spectrometry; Cloud point extraction; Cobalt
Laser induced thermal lens spectrometry for cobalt determination after cloud point extraction by Farzaneh Shemirani; Nader Shokoufi (pp. 238-243).
A new approach, employing cloud point extraction (CPE) in combination with thermal lens spectrometry (TLS), has been developed for the determination of cobalt. The CPE and TLS methods have good matching conditions for combination because TLS is suitable for low volume samples obtained after CPE and for organic solvents, which are used for dissolving the remaining analyte phase.1-(2-Pyridylazo)-2-naphthol (PAN) was used as a complexing agent and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant; then the pH of solution was adjusted. After phase separation at 50°C based on the cloud point extraction of the mixture, the surfactant-rich phase was dried and the remaining phase was dissolved using 20μL of carbon tetrachloride. The obtained solution was introduced into the quartz micro cell and the analyte was determined by thermal lens spectrometry. The He–Ne laser (632.8nm) was used as both the probe and the excite source.Under optimum conditions, the analytical curve was linear for the concentration range of 0.2–40ngmL−1 and the detection limit was 0.03ngmL−1. The enhancement factor of 470 was achieved for a 10mL sample. Relative standard deviations were lower than 5%.The method was successfully applied to the extraction and determination of cobalt in tap, river and sea water.
Keywords: Thermal lens spectrometry; Cloud point extraction; Cobalt
Enhanced plasmon resonance light scattering signals of colloidal gold resulted from its interactions with organic small molecules using captopril as an example by Zhong De Liu; Cheng Zhi Huang; Yuan Fang Li; Yun Fei Long (pp. 244-249).
Gold nanoparticles are known for their plasmon resonance absorption (PRA) depending on their size. Our this investigation shows that plasma resonance light scattering (PRLS) signals in the corresponding PRA region could be measured using a common spectrofluorometer, and be enhanced when aggregation of gold nanoparticles occurs due to their interaction with organic small molecules (OSMs). Using captopril (Cap) as an example, we investigated the interactions of gold nanoparticles with OSMs in order to propose a general method of OSMs such as typical clinic organic drugs. In aqueous medium of pH 2.09, there are about 2.2×103 Cap molecules covalently binding to the surface of a 10-nm diameter gold nanoparticle through the thiol functional group of Cap, and thus forms a core-shell assembly of [(Au)31000]@[(Cap)2200], displaying strong enhanced PRLS signals in the PRA region of gold colloid. The PRLS intensities characterized at 553.0nm were found to be proportional to the concentration of Cap over the range of 0.1–1.7mgL−1 with the determination limit (3 σ) of 32.0μgL−1. With that, Cap in pharmaceutical preparations could be determined with the recovery of 97.0–104.5% and R.S.D. of less than 2.4%.
Keywords: Gold colloid; Organic small molecules (OSMs); Captopril (Cap); Plasmon resonance absorption (PRA); Resonance light scattering (RLS); Plasma resonance light scattering (PRLS)
Enhanced plasmon resonance light scattering signals of colloidal gold resulted from its interactions with organic small molecules using captopril as an example by Zhong De Liu; Cheng Zhi Huang; Yuan Fang Li; Yun Fei Long (pp. 244-249).
Gold nanoparticles are known for their plasmon resonance absorption (PRA) depending on their size. Our this investigation shows that plasma resonance light scattering (PRLS) signals in the corresponding PRA region could be measured using a common spectrofluorometer, and be enhanced when aggregation of gold nanoparticles occurs due to their interaction with organic small molecules (OSMs). Using captopril (Cap) as an example, we investigated the interactions of gold nanoparticles with OSMs in order to propose a general method of OSMs such as typical clinic organic drugs. In aqueous medium of pH 2.09, there are about 2.2×103 Cap molecules covalently binding to the surface of a 10-nm diameter gold nanoparticle through the thiol functional group of Cap, and thus forms a core-shell assembly of [(Au)31000]@[(Cap)2200], displaying strong enhanced PRLS signals in the PRA region of gold colloid. The PRLS intensities characterized at 553.0nm were found to be proportional to the concentration of Cap over the range of 0.1–1.7mgL−1 with the determination limit (3 σ) of 32.0μgL−1. With that, Cap in pharmaceutical preparations could be determined with the recovery of 97.0–104.5% and R.S.D. of less than 2.4%.
Keywords: Gold colloid; Organic small molecules (OSMs); Captopril (Cap); Plasmon resonance absorption (PRA); Resonance light scattering (RLS); Plasma resonance light scattering (PRLS)
Baseline isotopic data of polyhalogenated compounds by Walter Vetter; Wolfgang Armbruster; Tatiana R. Betson; Jürgen Schleucher; Thomas Kapp; Katja Lehnert (pp. 250-256).
The δ2H- and δ13C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the compounds were related to the chloropesticides DDT and its metabolites, hexachlorocyclohexanes, and toxaphene, as well as several polybrominated compounds such as bromophenols and -anisoles. δ2H-values ranged between −235‰ and +75‰ whereas δ13C-values were found in the range −22‰ to −38‰. No correlation between δ2H- and δ13C-values could be identified. Comparative analysis clarified that bromophenols and the corresponding bromoanisoles may vary in their isotopic distribution.2H NMR was used to quantify abundances of2H isotopomers. Quantification of isotopomers of 2,4-dibromophenol and 2,4-dibromoanisole proved that both compounds from different suppliers do not originate from the same source. Differences in the δ2H-values of two toxaphene products were further investigated by the synthesis of products of different degree of chlorination from camphene. It was shown that the δ13C-values remained mostly unaltered as was expected since no carbon is lost in this procedure. However, the reaction products became enriched in2H with increasing degree of chlorination. Different δ2H-values of the starting material will also impact the δ2H-values of the chlorination products.
Keywords: Isotope ratio mass spectrometry; Deuterium nuclear magnetic resonance (; 2; H NMR); δ; 13; C-values; δ; 2; H-values; Quantification of isotopomers; Isotopomer distribution; Polyhalogenated pollutants; Chloropesticides; Source identification
Baseline isotopic data of polyhalogenated compounds by Walter Vetter; Wolfgang Armbruster; Tatiana R. Betson; Jürgen Schleucher; Thomas Kapp; Katja Lehnert (pp. 250-256).
The δ2H- and δ13C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the compounds were related to the chloropesticides DDT and its metabolites, hexachlorocyclohexanes, and toxaphene, as well as several polybrominated compounds such as bromophenols and -anisoles. δ2H-values ranged between −235‰ and +75‰ whereas δ13C-values were found in the range −22‰ to −38‰. No correlation between δ2H- and δ13C-values could be identified. Comparative analysis clarified that bromophenols and the corresponding bromoanisoles may vary in their isotopic distribution.2H NMR was used to quantify abundances of2H isotopomers. Quantification of isotopomers of 2,4-dibromophenol and 2,4-dibromoanisole proved that both compounds from different suppliers do not originate from the same source. Differences in the δ2H-values of two toxaphene products were further investigated by the synthesis of products of different degree of chlorination from camphene. It was shown that the δ13C-values remained mostly unaltered as was expected since no carbon is lost in this procedure. However, the reaction products became enriched in2H with increasing degree of chlorination. Different δ2H-values of the starting material will also impact the δ2H-values of the chlorination products.
Keywords: Isotope ratio mass spectrometry; Deuterium nuclear magnetic resonance (; 2; H NMR); δ; 13; C-values; δ; 2; H-values; Quantification of isotopomers; Isotopomer distribution; Polyhalogenated pollutants; Chloropesticides; Source identification
Determination of cationic surfactants in pharmaceuticals based on competitive aggregation in ternary amphiphile mixtures by Esther María Costi; María Dolores Sicilia; Soledad Rubio; Dolores Pérez-Bendito (pp. 257-263).
The surfactant to dye binding degree (SDBD) method was extended for the first time to the determination of cationic amphiphiles. For this purpose, Cresyl Violet (CV) and sodium dodecylsulphate (SDS) were selected as dye and reactant surfactant, respectively. This chemical system was used for the determination of cationic surfactants in pharmaceuticals. The approach was based on the competition established between the dye and cationic analytes to form mixed aggregates with the anionic surfactant (SDS–CV and SDS–analyte), which resulted in an increase of the amount of SDS required to reach a given SDS–CV binding degree. The feasibility of the proposed method to determine quaternary ammonium surfactants belonging to different structural groups (alkyldimethylbenzylammonium chlorides, alkyltrimethylammonium bromides and alkylpyridinium chlorides) in a wide variety of pharmaceutical formulations (solutions, creams and powders) was proved. The analytical features of the SDBD method (versatility, high precision and selectivity, ruggedness, rapidity, simplicity and low cost) made it an advantageous alternative to the conventional methods used in cationic surfactant quality control.
Keywords: Cationic surfactants; Competitive aggregation; Dye–surfactant aggregates; Surfactant–surfactant aggregates
Determination of cationic surfactants in pharmaceuticals based on competitive aggregation in ternary amphiphile mixtures by Esther María Costi; María Dolores Sicilia; Soledad Rubio; Dolores Pérez-Bendito (pp. 257-263).
The surfactant to dye binding degree (SDBD) method was extended for the first time to the determination of cationic amphiphiles. For this purpose, Cresyl Violet (CV) and sodium dodecylsulphate (SDS) were selected as dye and reactant surfactant, respectively. This chemical system was used for the determination of cationic surfactants in pharmaceuticals. The approach was based on the competition established between the dye and cationic analytes to form mixed aggregates with the anionic surfactant (SDS–CV and SDS–analyte), which resulted in an increase of the amount of SDS required to reach a given SDS–CV binding degree. The feasibility of the proposed method to determine quaternary ammonium surfactants belonging to different structural groups (alkyldimethylbenzylammonium chlorides, alkyltrimethylammonium bromides and alkylpyridinium chlorides) in a wide variety of pharmaceutical formulations (solutions, creams and powders) was proved. The analytical features of the SDBD method (versatility, high precision and selectivity, ruggedness, rapidity, simplicity and low cost) made it an advantageous alternative to the conventional methods used in cationic surfactant quality control.
Keywords: Cationic surfactants; Competitive aggregation; Dye–surfactant aggregates; Surfactant–surfactant aggregates
Fluorescence water sensor based on covalent immobilization of chalcone derivative by Cheng-Gang Niu; Ai-Ling Guan; Guang-Ming Zeng; Yun-Guo Liu; Zhong-Wu Li (pp. 264-270).
A new fluorescence sensor for determining water content in organic solvents has been successfully demonstrated based on a fluorescent dye. 4′- N, N-dimethylamino-4 methylacryloylamino chalcone (DMC), in which the charge donor and acceptor parts were both contained, was copolymerized with acrylamide, hydroxyethyl methacrylate and triethylene glycol dimethacrylate onto glass surface. The fluorescence intensity of DMC decreased with increasing of water content in organic solvents owing to the formation of solvate complexes. DMC fluorescence intensity changed as a linear function of water content in the range of 0–6% in the samples of acetone, ethanol, and acetonitrile solutions. Satisfactory reproducibility, reversibility and a short response time were realized. With the optimum membrane described, detection limits were of 0.006%, 0.008%, and 0.002% for acetone, ethanol, and acetonitrile, respectively. The sensing membrane was found to have a lifetime at least 2 months.
Keywords: Fluorescence sensor; Water; Covalent immobilization; Chalcone derivative
Fluorescence water sensor based on covalent immobilization of chalcone derivative by Cheng-Gang Niu; Ai-Ling Guan; Guang-Ming Zeng; Yun-Guo Liu; Zhong-Wu Li (pp. 264-270).
A new fluorescence sensor for determining water content in organic solvents has been successfully demonstrated based on a fluorescent dye. 4′- N, N-dimethylamino-4 methylacryloylamino chalcone (DMC), in which the charge donor and acceptor parts were both contained, was copolymerized with acrylamide, hydroxyethyl methacrylate and triethylene glycol dimethacrylate onto glass surface. The fluorescence intensity of DMC decreased with increasing of water content in organic solvents owing to the formation of solvate complexes. DMC fluorescence intensity changed as a linear function of water content in the range of 0–6% in the samples of acetone, ethanol, and acetonitrile solutions. Satisfactory reproducibility, reversibility and a short response time were realized. With the optimum membrane described, detection limits were of 0.006%, 0.008%, and 0.002% for acetone, ethanol, and acetonitrile, respectively. The sensing membrane was found to have a lifetime at least 2 months.
Keywords: Fluorescence sensor; Water; Covalent immobilization; Chalcone derivative
Improved surface-enhanced Raman scattering on optimum electrochemically roughened silver substrates by Yu-Chuan Liu; Chung-Chin Yu; Sen-Fu Sheu (pp. 271-275).
In this work, the effects of preparation conditions used in roughening silver substrates by electrochemical triangular-wave oxidation–reduction cycles (ORC) on surface-enhanced Raman scattering (SERS) were first investigated. The optimum roughening conditions for obtaining strongest SERS of Rhodamine 6G (R6G) are as follows. Ag electrodes were cycled in deoxygenated aqueous solutions containing 0.1M NaCl from −0.3 to +0.2V versus Ag/AgCl at 25mVs−1 for five scans. The SERS of R6G adsorbed on this optimum procedure-prepared roughened Ag substrate exhibits a higher intensity by one order of magnitude, as compared with that of R6G adsorbed on a normally roughened Ag substrate.
Keywords: Surface-enhanced Raman scattering; Oxidation–reduction cycles; Ag substrates
Improved surface-enhanced Raman scattering on optimum electrochemically roughened silver substrates by Yu-Chuan Liu; Chung-Chin Yu; Sen-Fu Sheu (pp. 271-275).
In this work, the effects of preparation conditions used in roughening silver substrates by electrochemical triangular-wave oxidation–reduction cycles (ORC) on surface-enhanced Raman scattering (SERS) were first investigated. The optimum roughening conditions for obtaining strongest SERS of Rhodamine 6G (R6G) are as follows. Ag electrodes were cycled in deoxygenated aqueous solutions containing 0.1M NaCl from −0.3 to +0.2V versus Ag/AgCl at 25mVs−1 for five scans. The SERS of R6G adsorbed on this optimum procedure-prepared roughened Ag substrate exhibits a higher intensity by one order of magnitude, as compared with that of R6G adsorbed on a normally roughened Ag substrate.
Keywords: Surface-enhanced Raman scattering; Oxidation–reduction cycles; Ag substrates
Analytical methods for the characterization of surface finishing in bricks by I. Nardini; E. Zendri; G. Biscontin; A. Brunetin (pp. 276-280).
The recent restoration works of Santo Stefano Church Façade (XV century) in Venice have shown traces variously saved of different kind of surface finishes. These finishes were found on the brick's surface both in the masonry and in the decorative elements.Different brick's surface and decorative tile samples were investigated using several techniques: optical microscopy, scanning electron-microscopy, thermal analysis, infrared spectroscopy and reflectance Fourier transform infrared microspectroscopy.The evaluation of the reached results was used to understand the decorative techniques and to recognize the material employed.
Keywords: Brick; Surface; Finishing; Fourier transform infrared spectroscopy; Thermal analysis
Analytical methods for the characterization of surface finishing in bricks by I. Nardini; E. Zendri; G. Biscontin; A. Brunetin (pp. 276-280).
The recent restoration works of Santo Stefano Church Façade (XV century) in Venice have shown traces variously saved of different kind of surface finishes. These finishes were found on the brick's surface both in the masonry and in the decorative elements.Different brick's surface and decorative tile samples were investigated using several techniques: optical microscopy, scanning electron-microscopy, thermal analysis, infrared spectroscopy and reflectance Fourier transform infrared microspectroscopy.The evaluation of the reached results was used to understand the decorative techniques and to recognize the material employed.
Keywords: Brick; Surface; Finishing; Fourier transform infrared spectroscopy; Thermal analysis
13C nuclear magnetic resonance spectroscopy to determine olive oil grades by Giovanna Vlahov (pp. 281-287).
13C nuclear magnetic resonance spectroscopy was used in a first attempt to differentiate olive oil samples by grades. High resolution13C NMR Distortionless Enhancement by Polarization Transfer (DEPT) spectra of 137 olive oil samples from the four grades, extra virgin olive oils, olive oils, olive pomace oils and lampante olive oils, were measured. The data relative to the resonance intensities (variables) of the unsaturated carbons of oleate (C-9 and C-10) and linoleate (L-9, L-10 and L-12) chains attached at the 1,3- and 2-positions of triacylglycerols were analyzed by linear discriminant analysis. The 1,3- and 2- carbons of the glycerol moiety of triacylglycerols along with the C-2, C-16 and C-18 resonance intensities of saturated, oleate and linoleate chains were also analyzed by linear discriminant analysis. The three discriminanting functions, which were calculated by using a stepwise variable selection algorithm, classified in the true group by cross-validation procedure, respectively, 76.9, 70.0, 94.4 and 100% of the extra virgin, olive oil, olive pomace oil and lampante olive oil grades.
Keywords: 13; C nuclear magnetic resonance; Grades; Olive oil
13C nuclear magnetic resonance spectroscopy to determine olive oil grades by Giovanna Vlahov (pp. 281-287).
13C nuclear magnetic resonance spectroscopy was used in a first attempt to differentiate olive oil samples by grades. High resolution13C NMR Distortionless Enhancement by Polarization Transfer (DEPT) spectra of 137 olive oil samples from the four grades, extra virgin olive oils, olive oils, olive pomace oils and lampante olive oils, were measured. The data relative to the resonance intensities (variables) of the unsaturated carbons of oleate (C-9 and C-10) and linoleate (L-9, L-10 and L-12) chains attached at the 1,3- and 2-positions of triacylglycerols were analyzed by linear discriminant analysis. The 1,3- and 2- carbons of the glycerol moiety of triacylglycerols along with the C-2, C-16 and C-18 resonance intensities of saturated, oleate and linoleate chains were also analyzed by linear discriminant analysis. The three discriminanting functions, which were calculated by using a stepwise variable selection algorithm, classified in the true group by cross-validation procedure, respectively, 76.9, 70.0, 94.4 and 100% of the extra virgin, olive oil, olive pomace oil and lampante olive oil grades.
Keywords: 13; C nuclear magnetic resonance; Grades; Olive oil
Direct determination of impurities in high purity silicon carbide by inductively coupled plasma optical emission spectrometry using slurry nebulization technique by Zheng Wang; Deren Qiu; Zheming Ni; Guangyi Tao; Pengyuan Yang (pp. 288-294).
A novel method for the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni and Ti in high purity silicon carbide (SiC) using slurry introduction axial viewed inductively coupled plasma optical emission spectrometry (ICP-OES) was described. The various sizes of SiC slurry were dispersed by adding dispersant polyethylene imine (PEI). The stability of slurry was characterized by zeta potential measurement, SEM observation and signal stability testing. The optimal concentration of PEI was found to be 0.5wt% for the SiC slurry. Analytical results of sub-μm size SiC by the slurry introduction were in good accordance with those by the alkaline fusion method which verified that determination could be calibrated by aqueous standards. For μm size SiC, results of most elements have a negative deviation and should be calibrated by the Certified Reference Material slurry. Owing to a rather low contamination in the sample preparation and stability of the slurry, the limits of detection (LODs), which are in the range of 40–2000ngg−1, superior to those of the conventional nebulization technique by ICP-OES or ICP-MS.
Keywords: Silicon carbide; Slurry introduction; Inductively coupled plasma optical emission spectrometry; Polyethylene imine
Direct determination of impurities in high purity silicon carbide by inductively coupled plasma optical emission spectrometry using slurry nebulization technique by Zheng Wang; Deren Qiu; Zheming Ni; Guangyi Tao; Pengyuan Yang (pp. 288-294).
A novel method for the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni and Ti in high purity silicon carbide (SiC) using slurry introduction axial viewed inductively coupled plasma optical emission spectrometry (ICP-OES) was described. The various sizes of SiC slurry were dispersed by adding dispersant polyethylene imine (PEI). The stability of slurry was characterized by zeta potential measurement, SEM observation and signal stability testing. The optimal concentration of PEI was found to be 0.5wt% for the SiC slurry. Analytical results of sub-μm size SiC by the slurry introduction were in good accordance with those by the alkaline fusion method which verified that determination could be calibrated by aqueous standards. For μm size SiC, results of most elements have a negative deviation and should be calibrated by the Certified Reference Material slurry. Owing to a rather low contamination in the sample preparation and stability of the slurry, the limits of detection (LODs), which are in the range of 40–2000ngg−1, superior to those of the conventional nebulization technique by ICP-OES or ICP-MS.
Keywords: Silicon carbide; Slurry introduction; Inductively coupled plasma optical emission spectrometry; Polyethylene imine