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Analytica Chimica Acta (v.588, #2)
Determination of aluminium in natural water samples by Juliette Tria; Edward C.V. Butler; Paul R. Haddad; Andrew R. Bowie (pp. 153-165).
The atmospheric deposition of terrestrial dust into the ocean is an important factor in controlling Earth's climate. Aluminium can be used as a tracer for the magnitude and location of dust transported from the land to surface ocean. The element is ideal for this purpose since its primary input is via aeolian dust deposition and it has a short surface water residence time. The accurate determination of dissolved aluminium in seawater is difficult due to the complexity of the matrix and the trace (nanomolar) concentrations at which the metal exists. This paper presents a critical review of the different sampling and analytical methods for the determination of the concentration of aluminium in natural waters, with particular focus on techniques successfully applied to shipboard analysis of seawater.
Keywords: Aluminium; Natural waters; Seawater; Fluorescence; Review
Determination of aluminium in natural water samples by Juliette Tria; Edward C.V. Butler; Paul R. Haddad; Andrew R. Bowie (pp. 153-165).
The atmospheric deposition of terrestrial dust into the ocean is an important factor in controlling Earth's climate. Aluminium can be used as a tracer for the magnitude and location of dust transported from the land to surface ocean. The element is ideal for this purpose since its primary input is via aeolian dust deposition and it has a short surface water residence time. The accurate determination of dissolved aluminium in seawater is difficult due to the complexity of the matrix and the trace (nanomolar) concentrations at which the metal exists. This paper presents a critical review of the different sampling and analytical methods for the determination of the concentration of aluminium in natural waters, with particular focus on techniques successfully applied to shipboard analysis of seawater.
Keywords: Aluminium; Natural waters; Seawater; Fluorescence; Review
Validation of an inductively coupled plasma mass spectrometry (ICP-MS) method for the determination of cerium, strontium, and titanium in ceramic materials used in radiological dispersal devices (RDDs) by Ana Paula Packer; Dominic Larivière; Chunsheng Li; Michael Chen; Amanda Fawcett; Kathy Nielsen; Kristine Mattson; Amares Chatt; Christine Scriver; Lorne S. Erhardt (pp. 166-172).
In radiological dispersal device (RDD) studies, sintered ceramics made of CeO2 and SrTiO3 were used to simulate actinide oxides and90SrTiO3, respectively. Instrumental neutron activation analysis (INAA), inductively coupled plasma optical emission spectroscopy (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS) were investigated as possible analytical techniques for the measurement of SrTiO3 and CeO2 constituents in powder forms, sintered ceramics, and air particulates collected following a detonation. For ICP-OES and ICP-MS analysis, new digestion procedures were developed using a closed-vessel microwave apparatus. Acid mixtures (HNO3:H2O2:HF (16:2:1) and HNO3:H2O2 (1:4)) were found to be effective for the digestion of SrTiO3 and CeO2, respectively. The intercomparison study confirmed that the results obtained by ICP-OES/MS are in good agreement with INAA results. This also confirms the efficiency of the digestion procedures for these refractory materials and the inter-exchangeability of the instrumentation tested. Comparison between the ICP-OES and the ICP-MS instrumentation for the determination of air particulates shows, that although the two methods are equivalent, ICP-MS provides better detection limits (0.11, 0.02, and 0.04μg per filter for Ti, Sr, and Ce, respectively) and the possibility to determine isotopic fractionation as the result of an explosion.
Keywords: Inductively coupled plasma mass spectrometry (ICP-MS); Inductively coupled plasma optical emission spectroscopy (ICP-OES); Instrumental neutron activation analysis (INAA); Aerosolized ceramic material; Radiological dispersal device (RDD)
Validation of an inductively coupled plasma mass spectrometry (ICP-MS) method for the determination of cerium, strontium, and titanium in ceramic materials used in radiological dispersal devices (RDDs) by Ana Paula Packer; Dominic Larivière; Chunsheng Li; Michael Chen; Amanda Fawcett; Kathy Nielsen; Kristine Mattson; Amares Chatt; Christine Scriver; Lorne S. Erhardt (pp. 166-172).
In radiological dispersal device (RDD) studies, sintered ceramics made of CeO2 and SrTiO3 were used to simulate actinide oxides and90SrTiO3, respectively. Instrumental neutron activation analysis (INAA), inductively coupled plasma optical emission spectroscopy (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS) were investigated as possible analytical techniques for the measurement of SrTiO3 and CeO2 constituents in powder forms, sintered ceramics, and air particulates collected following a detonation. For ICP-OES and ICP-MS analysis, new digestion procedures were developed using a closed-vessel microwave apparatus. Acid mixtures (HNO3:H2O2:HF (16:2:1) and HNO3:H2O2 (1:4)) were found to be effective for the digestion of SrTiO3 and CeO2, respectively. The intercomparison study confirmed that the results obtained by ICP-OES/MS are in good agreement with INAA results. This also confirms the efficiency of the digestion procedures for these refractory materials and the inter-exchangeability of the instrumentation tested. Comparison between the ICP-OES and the ICP-MS instrumentation for the determination of air particulates shows, that although the two methods are equivalent, ICP-MS provides better detection limits (0.11, 0.02, and 0.04μg per filter for Ti, Sr, and Ce, respectively) and the possibility to determine isotopic fractionation as the result of an explosion.
Keywords: Inductively coupled plasma mass spectrometry (ICP-MS); Inductively coupled plasma optical emission spectroscopy (ICP-OES); Instrumental neutron activation analysis (INAA); Aerosolized ceramic material; Radiological dispersal device (RDD)
Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of As and Se in soil and sludge by Yen-Jia Tseng; Chung-Chang Liu; Shiuh-Jen Jiang (pp. 173-178).
Slurry sampling electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to determine As and Se in soil and sludge samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as mixed modifiers to enhance the ion signals. The effectiveness of ETV sample introduction technique for alleviating various spectral interferences in ICP-MS analysis has been demonstrated. This method has been applied to determine As and Se in NIST SRM 2709 San Joaquin soil reference material and NIST SRM 2781 domestic sludge reference material and a farmland soil sample collected locally. Since the sensitivities of As and Se in slurry solution and aqueous solution were different, analyte addition technique was used to determine As and Se in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The precision between sample replicates was better than 5% for all determinations. The method detection limit estimated from analyte addition curves was about 0.03 and 0.02μgg−1 for As and Se, respectively, in original soil and sludge samples.
Keywords: Dynamic reaction cell inductively coupled plasma mass spectrometry; Slurry sampling; Electrothermal vaporization; Soil and sludge; As and Se
Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of As and Se in soil and sludge by Yen-Jia Tseng; Chung-Chang Liu; Shiuh-Jen Jiang (pp. 173-178).
Slurry sampling electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to determine As and Se in soil and sludge samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as mixed modifiers to enhance the ion signals. The effectiveness of ETV sample introduction technique for alleviating various spectral interferences in ICP-MS analysis has been demonstrated. This method has been applied to determine As and Se in NIST SRM 2709 San Joaquin soil reference material and NIST SRM 2781 domestic sludge reference material and a farmland soil sample collected locally. Since the sensitivities of As and Se in slurry solution and aqueous solution were different, analyte addition technique was used to determine As and Se in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The precision between sample replicates was better than 5% for all determinations. The method detection limit estimated from analyte addition curves was about 0.03 and 0.02μgg−1 for As and Se, respectively, in original soil and sludge samples.
Keywords: Dynamic reaction cell inductively coupled plasma mass spectrometry; Slurry sampling; Electrothermal vaporization; Soil and sludge; As and Se
Determination of mercury by intermittent flow electrochemical cold vapor generation coupled to atomic fluorescence spectrometry by Xun Li; Zhenghao Wang (pp. 179-183).
A novel method for determination of mercury was developed using an intermittent flow electrochemical cold vapor generation coupled to atomic fluorescence spectrometry (IF-ECVG-AFS). The mercury vapor was generated on the surface of glassy carbon cathode in the flow cell. The operating conditions for the electrochemical generation of mercury vapor were investigated in detail, and the interferences from various ions were evaluated. Under the optimized conditions, no evident memory effects of mercury were observed. The calibration curve was linear up to 5μgL−1Hg at 0.54Acm−2. A detection limit of 1.2ngL−1 Hg and a relative standard deviation of 1.8% for 1μgL−1 Hg were obtained. The accuracy of method was verified by the determination of mercury in the certified reference human hair. The ECVG avoided the use of reductants, thereby greatly reducing the contamination sources. In addition, the manifold of IF-ECVG-AFS was simple and amenable to automation.
Keywords: Electrochemical cold vapor generation; Atomic fluorescence spectrometry; Intermittent flow; Mercury
Determination of mercury by intermittent flow electrochemical cold vapor generation coupled to atomic fluorescence spectrometry by Xun Li; Zhenghao Wang (pp. 179-183).
A novel method for determination of mercury was developed using an intermittent flow electrochemical cold vapor generation coupled to atomic fluorescence spectrometry (IF-ECVG-AFS). The mercury vapor was generated on the surface of glassy carbon cathode in the flow cell. The operating conditions for the electrochemical generation of mercury vapor were investigated in detail, and the interferences from various ions were evaluated. Under the optimized conditions, no evident memory effects of mercury were observed. The calibration curve was linear up to 5μgL−1Hg at 0.54Acm−2. A detection limit of 1.2ngL−1 Hg and a relative standard deviation of 1.8% for 1μgL−1 Hg were obtained. The accuracy of method was verified by the determination of mercury in the certified reference human hair. The ECVG avoided the use of reductants, thereby greatly reducing the contamination sources. In addition, the manifold of IF-ECVG-AFS was simple and amenable to automation.
Keywords: Electrochemical cold vapor generation; Atomic fluorescence spectrometry; Intermittent flow; Mercury
Image evaluation with chemometric strategies for quality control of paints by Fabíola Manhas Verbi Pereira; Maria Izabel Maretti Silveira Bueno (pp. 184-191).
In this study a complementary analytical methodology for quality of paints evaluation was developed. Four different primers applied to steel substrates and submitted to accelerated laboratory and outdoor exposure tests were taken into account. After this, digitalized images were obtained from these samples using a conventional scanner. The images were converted in gray color scale histograms, the resulting data were organized into a matrix form and analyzed with the help of principal component analysis (PCA) and hierarchical cluster analysis (HCA). It was possible to identify the best primers performance avoiding subjective interpretation.
Keywords: Paint; Image histograms; Quality control; Exploratory analysis; Digital image analysis
Image evaluation with chemometric strategies for quality control of paints by Fabíola Manhas Verbi Pereira; Maria Izabel Maretti Silveira Bueno (pp. 184-191).
In this study a complementary analytical methodology for quality of paints evaluation was developed. Four different primers applied to steel substrates and submitted to accelerated laboratory and outdoor exposure tests were taken into account. After this, digitalized images were obtained from these samples using a conventional scanner. The images were converted in gray color scale histograms, the resulting data were organized into a matrix form and analyzed with the help of principal component analysis (PCA) and hierarchical cluster analysis (HCA). It was possible to identify the best primers performance avoiding subjective interpretation.
Keywords: Paint; Image histograms; Quality control; Exploratory analysis; Digital image analysis
Analysis of amoxicillin in human urine by photo-activated generation of fluorescence excitation–emission matrices and artificial neural networks combined with residual bilinearization by Alejandro García-Reiriz; Patricia C. Damiani; Alejandro C. Olivieri (pp. 192-199).
Fluorescence excitation–emission data recorded for amoxicillin after photo-activated reaction with periodate have been processed by a novel second-order multivariate method based on the combination of artificial neural networks and residual bilinearization (ANN/RBL), since the signals bear a strong non-linear relation with the analyte concentration. The selected chemometric methodology is employed for the first time to evaluate experimental non-linear second-order spectral information. Due to severe overlapping between the emission profiles for the analyte reaction product and for the urine background, calibration was done using different spiked urine samples. This allowed for the determination of amoxicillin in test spiked urines, other than those employed for calibration. When new urine samples containing a fluorescent anti-inflammatory were analyzed, accurate prediction in the presence of unexpected components required the achievement of the second-order advantage, which is provided by the post-training RBL procedure. Amoxicillin was also determined by ANN/RBL in a series of real urine samples, which allowed one to perform a comparison study with the reference high-performance liquid chromatographic technique.
Keywords: Second-order calibration; Fluorescence excitation–emission; Artificial neural networks; Residual bilinearization; Amoxicillin; Human urine
Analysis of amoxicillin in human urine by photo-activated generation of fluorescence excitation–emission matrices and artificial neural networks combined with residual bilinearization by Alejandro García-Reiriz; Patricia C. Damiani; Alejandro C. Olivieri (pp. 192-199).
Fluorescence excitation–emission data recorded for amoxicillin after photo-activated reaction with periodate have been processed by a novel second-order multivariate method based on the combination of artificial neural networks and residual bilinearization (ANN/RBL), since the signals bear a strong non-linear relation with the analyte concentration. The selected chemometric methodology is employed for the first time to evaluate experimental non-linear second-order spectral information. Due to severe overlapping between the emission profiles for the analyte reaction product and for the urine background, calibration was done using different spiked urine samples. This allowed for the determination of amoxicillin in test spiked urines, other than those employed for calibration. When new urine samples containing a fluorescent anti-inflammatory were analyzed, accurate prediction in the presence of unexpected components required the achievement of the second-order advantage, which is provided by the post-training RBL procedure. Amoxicillin was also determined by ANN/RBL in a series of real urine samples, which allowed one to perform a comparison study with the reference high-performance liquid chromatographic technique.
Keywords: Second-order calibration; Fluorescence excitation–emission; Artificial neural networks; Residual bilinearization; Amoxicillin; Human urine
Prediction of gas chromatography/electron capture detector retention times of chlorinated pesticides, herbicides, and organohalides by multivariate chemometrics methods by Jahanbakhsh Ghasemi; Saeid Asadpour; Azizeh Abdolmaleki (pp. 200-206).
A quantitative structure–retention relationship (QSRR) study, has been carried out on the gas chromatograph/electron capture detector (GC/ECD) system retention times ( tRs) of 38 diverse chlorinated pesticides, herbicides, and organohalides by using molecular structural descriptors. Modeling of retention times of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR) and partial least squares (PLS) regression. The stepwise regression using SPSS was used for the selection of the variables that resulted in the best-fitted models. Appropriate models with low standard errors and high correlation coefficients were obtained. Three types of molecular descriptors including electronic, steric and thermodynamic were used to develop a quantitative relationship between the retention times and structural properties. MLR and PLS analysis has been carried out to derive the best QSRR models. After variables selection, MLR and PLS methods used with leave-one-out cross validation for building the regression models. The predictive quality of the QSRR models were tested for an external prediction set of 12 compounds randomly chosen from 38 compounds. The PLS regression method was used to model the structure-retention relationships, more accurately. However, the results surprisingly showed more or less the same quality for MLR and PLS modeling according to squared regression coefficients R2 which were 0.951 and 0.948 for MLR and PLS, respectively.
Keywords: Molecular descriptors; Retention times; Quantitative structure–retention relationship; Multiple linear regression and partial least squares; Chlorinated pesticides; Herbicides; Organohalides
Prediction of gas chromatography/electron capture detector retention times of chlorinated pesticides, herbicides, and organohalides by multivariate chemometrics methods by Jahanbakhsh Ghasemi; Saeid Asadpour; Azizeh Abdolmaleki (pp. 200-206).
A quantitative structure–retention relationship (QSRR) study, has been carried out on the gas chromatograph/electron capture detector (GC/ECD) system retention times ( tRs) of 38 diverse chlorinated pesticides, herbicides, and organohalides by using molecular structural descriptors. Modeling of retention times of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR) and partial least squares (PLS) regression. The stepwise regression using SPSS was used for the selection of the variables that resulted in the best-fitted models. Appropriate models with low standard errors and high correlation coefficients were obtained. Three types of molecular descriptors including electronic, steric and thermodynamic were used to develop a quantitative relationship between the retention times and structural properties. MLR and PLS analysis has been carried out to derive the best QSRR models. After variables selection, MLR and PLS methods used with leave-one-out cross validation for building the regression models. The predictive quality of the QSRR models were tested for an external prediction set of 12 compounds randomly chosen from 38 compounds. The PLS regression method was used to model the structure-retention relationships, more accurately. However, the results surprisingly showed more or less the same quality for MLR and PLS modeling according to squared regression coefficients R2 which were 0.951 and 0.948 for MLR and PLS, respectively.
Keywords: Molecular descriptors; Retention times; Quantitative structure–retention relationship; Multiple linear regression and partial least squares; Chlorinated pesticides; Herbicides; Organohalides
Quality control and discrimination of Pericarpium Citri Reticulatae and Pericarpium Citri Reticulatae Viride based on high-performance liquid chromatographic fingerprints and multivariate statistical analysis by Lun-zhao Yi; Da-lin Yuan; Yi-zeng Liang; Pei-shan Xie; Yu Zhao (pp. 207-215).
High-performance liquid chromatographic (HPLC) fingerprints of Pericarpium Citri Reticulatae (PCR) and Pericarpium Citri Reticulatae Viride (PCRV) were firstly measured for deliberately collected 39 authentic samples and 21 commercial samples. Both correlation coefficients of similarity for chromatograms and absolute peak areas of characteristic compounds were calculated for quantitative expression of the HPLC fingerprints. After principal component analysis (PCA) successfully distinguished the ‘mixed peels’ samples from authentic samples, partial least squares-linear discrimination analysis (PLS-LDA) was then effectively applied to class separation between authentic PCR and PCRV. Furthermore, the unequivocally determined compounds, hesperidin, nobiletin and tangeretin, were screened out by loadings plots of PCA and PLS-LDA. The results indicated that they could be used as chemical markers for discrimination among different groups of samples. The proposed method shows an efficient strategy for quality control of PCR and PCRV, which cannot only distinguish the ‘mixed peels’ but also discriminate authentic PCR and PCRV. This method has potential perspective for quality control of traditional Chinese medicine (TCM).
Keywords: Pericarpium Citri Reticulatae; Pericarpium Citri Reticulatae Viride; High-performance liquid chromatography–diode array detection; Partial least squares-linear discrimination analysis; Principal component analysis; Fingerprint
Quality control and discrimination of Pericarpium Citri Reticulatae and Pericarpium Citri Reticulatae Viride based on high-performance liquid chromatographic fingerprints and multivariate statistical analysis by Lun-zhao Yi; Da-lin Yuan; Yi-zeng Liang; Pei-shan Xie; Yu Zhao (pp. 207-215).
High-performance liquid chromatographic (HPLC) fingerprints of Pericarpium Citri Reticulatae (PCR) and Pericarpium Citri Reticulatae Viride (PCRV) were firstly measured for deliberately collected 39 authentic samples and 21 commercial samples. Both correlation coefficients of similarity for chromatograms and absolute peak areas of characteristic compounds were calculated for quantitative expression of the HPLC fingerprints. After principal component analysis (PCA) successfully distinguished the ‘mixed peels’ samples from authentic samples, partial least squares-linear discrimination analysis (PLS-LDA) was then effectively applied to class separation between authentic PCR and PCRV. Furthermore, the unequivocally determined compounds, hesperidin, nobiletin and tangeretin, were screened out by loadings plots of PCA and PLS-LDA. The results indicated that they could be used as chemical markers for discrimination among different groups of samples. The proposed method shows an efficient strategy for quality control of PCR and PCRV, which cannot only distinguish the ‘mixed peels’ but also discriminate authentic PCR and PCRV. This method has potential perspective for quality control of traditional Chinese medicine (TCM).
Keywords: Pericarpium Citri Reticulatae; Pericarpium Citri Reticulatae Viride; High-performance liquid chromatography–diode array detection; Partial least squares-linear discrimination analysis; Principal component analysis; Fingerprint
Fingerprint developing of coffee flavor by gas chromatography–mass spectrometry and combined chemometrics methods by Lan-Fang Huang; Ming-Jian Wu; Ke-Jun Zhong; Xian-Jun Sun; Yi-Zeng Liang; Yun-Hui Dai; Ke-Long Huang; Fang-Qiu Guo (pp. 216-223).
In this paper, chromatographic fingerprint was firstly used for quality control of tobacco flavors. Based on gas chromatography–mass spectrometry (GC–MS) and combined chemometrics methods, a simple, reliable and reproducible method for developing chromatographic fingerprint of coffee flavor, one of tobacco flavors, was described. Six coffee flavor samples obtained from different locations were used to establish the fingerprint. The qualitative and quantitative analysis of coffee flavor sample from Shenzhen was completed with the help of subwindow factor analysis (SFA). Fifty-two components of 68 separated constituents in coffee flavor sample from Shenzhen, accounting for 88.42% of the total content, were identified and quantified. Then, spectral correlative chromatography (SCC) was used to extract the common peaks from other five studied coffee flavor samples. Thirty-eight components were found to exist in all six samples. Finally, the method validation of fingerprint analysis was performed based on the relative retention time and the relative peak area of common peaks, sample stability and similarity analysis. The similarities of six coffee flavor samples were more than 0.9104 and showed that samples from different locations were consistent to some extent. The developed chromatographic fingerprint was successfully used to differentiate coffee flavor from coco flavor and some little difference sample prepared with coffee flavor and coco flavor by both similarity comparison and principal component projection analysis. The developed method can be used for quality control of coffee flavor.
Keywords: Coffee flavor; Gas chromatography–mass spectrometry (GC–MS); Fingerprint; Subwindow factor analysis (SFA); Spectral correlative chromatography (SCC); Similarity
Fingerprint developing of coffee flavor by gas chromatography–mass spectrometry and combined chemometrics methods by Lan-Fang Huang; Ming-Jian Wu; Ke-Jun Zhong; Xian-Jun Sun; Yi-Zeng Liang; Yun-Hui Dai; Ke-Long Huang; Fang-Qiu Guo (pp. 216-223).
In this paper, chromatographic fingerprint was firstly used for quality control of tobacco flavors. Based on gas chromatography–mass spectrometry (GC–MS) and combined chemometrics methods, a simple, reliable and reproducible method for developing chromatographic fingerprint of coffee flavor, one of tobacco flavors, was described. Six coffee flavor samples obtained from different locations were used to establish the fingerprint. The qualitative and quantitative analysis of coffee flavor sample from Shenzhen was completed with the help of subwindow factor analysis (SFA). Fifty-two components of 68 separated constituents in coffee flavor sample from Shenzhen, accounting for 88.42% of the total content, were identified and quantified. Then, spectral correlative chromatography (SCC) was used to extract the common peaks from other five studied coffee flavor samples. Thirty-eight components were found to exist in all six samples. Finally, the method validation of fingerprint analysis was performed based on the relative retention time and the relative peak area of common peaks, sample stability and similarity analysis. The similarities of six coffee flavor samples were more than 0.9104 and showed that samples from different locations were consistent to some extent. The developed chromatographic fingerprint was successfully used to differentiate coffee flavor from coco flavor and some little difference sample prepared with coffee flavor and coco flavor by both similarity comparison and principal component projection analysis. The developed method can be used for quality control of coffee flavor.
Keywords: Coffee flavor; Gas chromatography–mass spectrometry (GC–MS); Fingerprint; Subwindow factor analysis (SFA); Spectral correlative chromatography (SCC); Similarity
Effect of temperature variation on the visible and near infrared spectra of wine and the consequences on the partial least square calibrations developed to measure chemical composition by D. Cozzolino; L. Liu; W.U. Cynkar; R.G. Dambergs; L. Janik; C.B. Colby; M. Gishen (pp. 224-230).
Many studies have reported the use of near infrared (NIR) spectroscopy to characterize wines or to predict wine chemical composition. However, little is known about the effect of variation in temperature on the NIR spectrum of wine and the subsequent effect on the performance of calibrations used to measure chemical composition. Several parameters influence the spectra of organic molecules in the NIR region, with temperature being one of the most important factors affecting the vibration intensity and frequency of molecular bonds. Wine is a complex mixture of chemical components (e.g. water, sugars, organic acids, and ethanol), and a simple ethanol and water model solution cannot be used to study the possible effects of temperature variations in the NIR spectrum of wine. Ten red and 10 white wines were scanned in triplicate at six different temperatures (25°C, 30°C, 35°C, 40°C, 45°C and 50°C) in the visible (vis) and NIR regions (400–2500nm) in a monochromator instrument in transmission mode (1mm path length). Principal component analysis (PCA) and partial least squares (PLS) regression models were developed using full cross validation (leave-one-out). These models were used to interpret the spectra and to develop calibrations for alcohol, sugars (glucose+fructose) and pH at different temperatures. The results showed that differences in the spectra around 970nm and 1400nm, related to OH bonding were observed for both varieties. Additionally an effect of temperature on the vis region of red wine spectra was observed. The standard error of cross validation (SECV) achieved for the PLS calibration models tended to inverse as the temperature increased. The practical implication of this study it is recommended that the temperature of scanning for wine analysis using a 1mm path length cuvette should be between 30°C and 35°C.
Keywords: Near infrared spectra; Temperature; Wine; Principal components; Partial least squares; Spectral changes; Hydrogen bonding
Effect of temperature variation on the visible and near infrared spectra of wine and the consequences on the partial least square calibrations developed to measure chemical composition by D. Cozzolino; L. Liu; W.U. Cynkar; R.G. Dambergs; L. Janik; C.B. Colby; M. Gishen (pp. 224-230).
Many studies have reported the use of near infrared (NIR) spectroscopy to characterize wines or to predict wine chemical composition. However, little is known about the effect of variation in temperature on the NIR spectrum of wine and the subsequent effect on the performance of calibrations used to measure chemical composition. Several parameters influence the spectra of organic molecules in the NIR region, with temperature being one of the most important factors affecting the vibration intensity and frequency of molecular bonds. Wine is a complex mixture of chemical components (e.g. water, sugars, organic acids, and ethanol), and a simple ethanol and water model solution cannot be used to study the possible effects of temperature variations in the NIR spectrum of wine. Ten red and 10 white wines were scanned in triplicate at six different temperatures (25°C, 30°C, 35°C, 40°C, 45°C and 50°C) in the visible (vis) and NIR regions (400–2500nm) in a monochromator instrument in transmission mode (1mm path length). Principal component analysis (PCA) and partial least squares (PLS) regression models were developed using full cross validation (leave-one-out). These models were used to interpret the spectra and to develop calibrations for alcohol, sugars (glucose+fructose) and pH at different temperatures. The results showed that differences in the spectra around 970nm and 1400nm, related to OH bonding were observed for both varieties. Additionally an effect of temperature on the vis region of red wine spectra was observed. The standard error of cross validation (SECV) achieved for the PLS calibration models tended to inverse as the temperature increased. The practical implication of this study it is recommended that the temperature of scanning for wine analysis using a 1mm path length cuvette should be between 30°C and 35°C.
Keywords: Near infrared spectra; Temperature; Wine; Principal components; Partial least squares; Spectral changes; Hydrogen bonding
A method for determination of COD in a domestic wastewater treatment plant by using near-infrared reflectance spectrometry of seston by Antonio C. Sousa; Maria Mônica L.M. Lucio; Ovídeo F. Bezerra Neto; Glauciene P.S. Marcone; Alessandra F.C. Pereira; Edilene O. Dantas; Wallace D. Fragoso; Mario Cesar U. Araujo; Roberto K.H. Galvão (pp. 231-236).
This paper proposes a method for determination of chemical oxygen demand (COD) in domestic wastewater. The proposed method is based on near-infrared reflectance (NIRR) measurements of seston collected from wastewater samples by filtration. The analysis does not require any special reagent, catalyst or solvent. Inherent baseline and noise features present in NIRR spectra are removed by a Savitzky–Golay derivative procedure followed by wavelet denoising. The resulting wavelet approximation coefficients are used for partial-least-squares modelling and subsequent prediction of COD values in new samples. The model is calibrated by using COD values obtained according to the American Public Health Association (APHA) reference method. The proposed method is applied to effluent samples from the anaerobic ponds of the Mangabeira municipal wastewater treatment plant in the city of João Pessoa (Paraíba, Brazil). By comparing the NIRR prediction results with the APHA reference values, a root-mean-square error of prediction (RMSEP) of 19mgO2L−1 and a correlation of 0.97 were obtained. Such results are deemed adequate in view of the joint estimate of the standard error of the reference method, which was calculated as 21mgO2L−1.
Keywords: Chemical oxygen demand; Domestic wastewater analysis; Seston; Near-infrared reflectance spectrometry; Partial-least-squares; Wavelet transform
A method for determination of COD in a domestic wastewater treatment plant by using near-infrared reflectance spectrometry of seston by Antonio C. Sousa; Maria Mônica L.M. Lucio; Ovídeo F. Bezerra Neto; Glauciene P.S. Marcone; Alessandra F.C. Pereira; Edilene O. Dantas; Wallace D. Fragoso; Mario Cesar U. Araujo; Roberto K.H. Galvão (pp. 231-236).
This paper proposes a method for determination of chemical oxygen demand (COD) in domestic wastewater. The proposed method is based on near-infrared reflectance (NIRR) measurements of seston collected from wastewater samples by filtration. The analysis does not require any special reagent, catalyst or solvent. Inherent baseline and noise features present in NIRR spectra are removed by a Savitzky–Golay derivative procedure followed by wavelet denoising. The resulting wavelet approximation coefficients are used for partial-least-squares modelling and subsequent prediction of COD values in new samples. The model is calibrated by using COD values obtained according to the American Public Health Association (APHA) reference method. The proposed method is applied to effluent samples from the anaerobic ponds of the Mangabeira municipal wastewater treatment plant in the city of João Pessoa (Paraíba, Brazil). By comparing the NIRR prediction results with the APHA reference values, a root-mean-square error of prediction (RMSEP) of 19mgO2L−1 and a correlation of 0.97 were obtained. Such results are deemed adequate in view of the joint estimate of the standard error of the reference method, which was calculated as 21mgO2L−1.
Keywords: Chemical oxygen demand; Domestic wastewater analysis; Seston; Near-infrared reflectance spectrometry; Partial-least-squares; Wavelet transform
Determination of iron–porphyrin-like complexes at nanomolar levels in seawater by Lilita Vong; Agathe Laës; Stéphane Blain (pp. 237-244).
A new method for the non-specific determination of iron–porphyrin-like complexes in natural waters has been developed. It is based on the chemiluminescent oxidation of the luminol in the presence of dioxygen (O2) at pH 13. The method has been implemented in a FIA manifold that allowed the direct injection of seawater. The limit of detection is 0.11nM of equivalent hemin (Fe–protoporphyrin IX). Fe2+, Fe3+, H2O2, siderophore (deferoxamin mesylate), humic acid and phytic acid did not interfere when they were present at the concentrations expected in seawater. Metal free porphyrin and Mg, Cu, Co porphyrin complexes did not induce a significant chemiluminescent signal. Poisoned unfiltered samples could be stored for several weeks before analyses. The new method was successfully applied to the determination of the Fe–porphyrin complexes contained in cultured phytoplankton and in natural samples.
Keywords: Iron; Porphyrin; Seawater; Flow injection; Complexation; Chemiluminescence
Determination of iron–porphyrin-like complexes at nanomolar levels in seawater by Lilita Vong; Agathe Laës; Stéphane Blain (pp. 237-244).
A new method for the non-specific determination of iron–porphyrin-like complexes in natural waters has been developed. It is based on the chemiluminescent oxidation of the luminol in the presence of dioxygen (O2) at pH 13. The method has been implemented in a FIA manifold that allowed the direct injection of seawater. The limit of detection is 0.11nM of equivalent hemin (Fe–protoporphyrin IX). Fe2+, Fe3+, H2O2, siderophore (deferoxamin mesylate), humic acid and phytic acid did not interfere when they were present at the concentrations expected in seawater. Metal free porphyrin and Mg, Cu, Co porphyrin complexes did not induce a significant chemiluminescent signal. Poisoned unfiltered samples could be stored for several weeks before analyses. The new method was successfully applied to the determination of the Fe–porphyrin complexes contained in cultured phytoplankton and in natural samples.
Keywords: Iron; Porphyrin; Seawater; Flow injection; Complexation; Chemiluminescence
Highly sensitive and rapid tandem bioluminescent immunoassay using aequorin labeled Fab fragment and biotinylated firefly luciferase by Katsutoshi Ito; Waka Nishimura; Masako Maeda; Keiko Gomi; Satoshi Inouye; Hidetoshi Arakawa (pp. 245-251).
We established a simultaneous bioluminescent assay utilizing aequorin (Aq) and biotinylated firefly luciferase (b-Luc); furthermore, we developed a highly sensitive and rapid tandem bioluminescent immunoassay (BLIA) involving the Aq-labeled Fab fragment and b-Luc–streptavidin complex. Minimum detection limits of Aq and b-Luc were 9.4×10−21mol assay−1 (blank+3S.D.) and 3.6×10−19mol assay−1 (blank+3S.D.), respectively. Measurements of two luminescent proteins were completed in 4s with a single assay medium. In this study, prostatic acid phosphatase (PAP) and prostate specific antigen (PSA), which served as analytes, were measured in the tandem BLIA. PAP and PSA were detected by the Aq-labeled anti-Dig Fab fragment and b-Luc–streptavidin complex, respectively. The measurable ranges of PAP and PSA were 0.04–100 and 0.2–200ngmL−1, respectively. This technique was also applied to the simultaneous measurement of PSA and α-fetoprotein (AFP). Measurable ranges of PSA and AFP were 0.2–200 and 1.95–1000ngmL−1, respectively. Levels of PAP and PSA or PSA and AFP in human serum could be accurately determined with the proposed BLIA. Satisfactory correlations were observed between results obtained from the proposed BLIA and those derived from commercial kits.
Keywords: Simultaneous bioluminescent assay; Aequorin; Biotinylated firefly luciferase; Tandem bioluminescent immunoassay; Prostate specific antigen; Prostatic acid phosphatase; α-Fetoprotein
Highly sensitive and rapid tandem bioluminescent immunoassay using aequorin labeled Fab fragment and biotinylated firefly luciferase by Katsutoshi Ito; Waka Nishimura; Masako Maeda; Keiko Gomi; Satoshi Inouye; Hidetoshi Arakawa (pp. 245-251).
We established a simultaneous bioluminescent assay utilizing aequorin (Aq) and biotinylated firefly luciferase (b-Luc); furthermore, we developed a highly sensitive and rapid tandem bioluminescent immunoassay (BLIA) involving the Aq-labeled Fab fragment and b-Luc–streptavidin complex. Minimum detection limits of Aq and b-Luc were 9.4×10−21mol assay−1 (blank+3S.D.) and 3.6×10−19mol assay−1 (blank+3S.D.), respectively. Measurements of two luminescent proteins were completed in 4s with a single assay medium. In this study, prostatic acid phosphatase (PAP) and prostate specific antigen (PSA), which served as analytes, were measured in the tandem BLIA. PAP and PSA were detected by the Aq-labeled anti-Dig Fab fragment and b-Luc–streptavidin complex, respectively. The measurable ranges of PAP and PSA were 0.04–100 and 0.2–200ngmL−1, respectively. This technique was also applied to the simultaneous measurement of PSA and α-fetoprotein (AFP). Measurable ranges of PSA and AFP were 0.2–200 and 1.95–1000ngmL−1, respectively. Levels of PAP and PSA or PSA and AFP in human serum could be accurately determined with the proposed BLIA. Satisfactory correlations were observed between results obtained from the proposed BLIA and those derived from commercial kits.
Keywords: Simultaneous bioluminescent assay; Aequorin; Biotinylated firefly luciferase; Tandem bioluminescent immunoassay; Prostate specific antigen; Prostatic acid phosphatase; α-Fetoprotein
Assessment of the surfactant-dye binding degree method as an alternative to the methylene blue method for the determination of anionic surfactants in aqueous environmental samples by Ana Pedraza; María Dolores Sicilia; Soledad Rubio; Dolores Pérez-Bendito (pp. 252-260).
The surfactant to dye binding degree (SDBD) method is proposed for the routine monitoring of anionic surfactants in aqueous environmental samples and their analytical features compared with those provided by the standard methylene blue (MB) method. This new analytical approach is based on the effect that anionic surfactants exert on the binding degree of the cationic surfactant didodecyldimethylammonium bromide (DDABr) to the anionic dye Coomassie Brilliant Blue G (CBBG). The formation of DDABr-CBBG aggregates is monitored photometrically. The analytical applicability of the proposed method was demonstrated by determining anionic surfactants in tap, river and swamp water, and raw and treated sewage. The mean recoveries obtained ranged between 99 and 101%. The SDBD method offers important advantages over the classical MB method: it is more sensitive, selective, precise, simple and rapid; the analytical response is independent of the molecular structure of the anionic surfactants, and the volume of sample required for analysis and the consumption of organic solvents are significantly reduced.
Keywords: Anionic surfactants; Aqueous environmental samples; Dye-surfactant aggregates; Competitive aggregation
Assessment of the surfactant-dye binding degree method as an alternative to the methylene blue method for the determination of anionic surfactants in aqueous environmental samples by Ana Pedraza; María Dolores Sicilia; Soledad Rubio; Dolores Pérez-Bendito (pp. 252-260).
The surfactant to dye binding degree (SDBD) method is proposed for the routine monitoring of anionic surfactants in aqueous environmental samples and their analytical features compared with those provided by the standard methylene blue (MB) method. This new analytical approach is based on the effect that anionic surfactants exert on the binding degree of the cationic surfactant didodecyldimethylammonium bromide (DDABr) to the anionic dye Coomassie Brilliant Blue G (CBBG). The formation of DDABr-CBBG aggregates is monitored photometrically. The analytical applicability of the proposed method was demonstrated by determining anionic surfactants in tap, river and swamp water, and raw and treated sewage. The mean recoveries obtained ranged between 99 and 101%. The SDBD method offers important advantages over the classical MB method: it is more sensitive, selective, precise, simple and rapid; the analytical response is independent of the molecular structure of the anionic surfactants, and the volume of sample required for analysis and the consumption of organic solvents are significantly reduced.
Keywords: Anionic surfactants; Aqueous environmental samples; Dye-surfactant aggregates; Competitive aggregation
Humic acid-bonded silica as a novel sorbent for solid-phase extraction of benzo[a]pyrene in edible oils by Dan Luo; Qiong-Wei Yu; Hong-Rui Yin; Yu-Qi Feng (pp. 261-267).
A novel solid-phase extraction (SPE) sorbent, humic acid-bonded silica (HAS), was prepared. Humic acids (HAs) were grafted onto silica matrices via an amide linkage between humyl chloride and the amido terminus of 3-aminopropyltrimethoxysilane (APTS)-silica gel. The resulting material was characterized by Fourier transform infrared spectrometer, elemental analysis, and nitrogen adsorption analysis. This sorbent exhibits an excellent adsorption capacity for some electron-abundant analytes owing to its peculiar structure. In this paper, we choose benzo[a]pyrene (BaP) in oil as a probe to validate the adsorption capacity of the material. Thus a fast, cheap and simple SPE method with humic acid-bonded silica cartridge for edible oil clean-up, followed by high-performance liquid chromatography (HPLC) with fluorescence detection was established. The effects of experimental variables, such as washing and elution solvents, and the amount of sorbents have been studied. The recoveries of BaP in edible oils spiked at 0.2–100μgkg−1 were in the range of 78.8–102.7% with relative standard deviations ranging between 1.3 and 9.3%; the limit of detection was –0.06μgkg−1.
Keywords: Solid-phase extraction; Benzo[a]pyrene; Humic acid-bonded silica; Edible oils
Humic acid-bonded silica as a novel sorbent for solid-phase extraction of benzo[a]pyrene in edible oils by Dan Luo; Qiong-Wei Yu; Hong-Rui Yin; Yu-Qi Feng (pp. 261-267).
A novel solid-phase extraction (SPE) sorbent, humic acid-bonded silica (HAS), was prepared. Humic acids (HAs) were grafted onto silica matrices via an amide linkage between humyl chloride and the amido terminus of 3-aminopropyltrimethoxysilane (APTS)-silica gel. The resulting material was characterized by Fourier transform infrared spectrometer, elemental analysis, and nitrogen adsorption analysis. This sorbent exhibits an excellent adsorption capacity for some electron-abundant analytes owing to its peculiar structure. In this paper, we choose benzo[a]pyrene (BaP) in oil as a probe to validate the adsorption capacity of the material. Thus a fast, cheap and simple SPE method with humic acid-bonded silica cartridge for edible oil clean-up, followed by high-performance liquid chromatography (HPLC) with fluorescence detection was established. The effects of experimental variables, such as washing and elution solvents, and the amount of sorbents have been studied. The recoveries of BaP in edible oils spiked at 0.2–100μgkg−1 were in the range of 78.8–102.7% with relative standard deviations ranging between 1.3 and 9.3%; the limit of detection was –0.06μgkg−1.
Keywords: Solid-phase extraction; Benzo[a]pyrene; Humic acid-bonded silica; Edible oils
A humic acid stationary phase for the high performance liquid chromatography separation of buckminsterfullerenes: Theoretical and practical aspects by Nicolas Casadei; Mireille Thomassin; Yves-Claude Guillaume; Claire André (pp. 268-273).
The influence of the mobile phase composition and column temperature on the chromatographic separation of five buckminsterfullerenes (C60, C70, C76, C78, C84) on a stationary phase based on silica gel with chemically bonded humic acid (Bonded humic acid column (BHAC)) was studied. The retention behavior of the fullerenes was measured under isocratic conditions with different mobile phase compositions, ranging from 0.05–0.70 (v/v) of toluene in cyclohexane. The column temperature was analysed in the range 35–75°C. The retention factors of the five fullerenes do not depend linearly on the toluene fraction but follow a quadratic relationship. The best chromatographic conditions for baseline separation of the five fullerenes were selected. The retention of the fullerenes on the HA stationary phase was strongly affected by temperature. Positive values of thermodynamic parameters (changes of enthalpy and entropy) were due to the abnormal solubility behaviour of fullerenes in toluene in the temperature range 35–75°C. The information obtained in this work makes this BHAC very simple to prepare and low cost, useful for fullerene research applications.
Keywords: Fullerenes; Humic acid; Stationary phase; Separation; Retention
A humic acid stationary phase for the high performance liquid chromatography separation of buckminsterfullerenes: Theoretical and practical aspects by Nicolas Casadei; Mireille Thomassin; Yves-Claude Guillaume; Claire André (pp. 268-273).
The influence of the mobile phase composition and column temperature on the chromatographic separation of five buckminsterfullerenes (C60, C70, C76, C78, C84) on a stationary phase based on silica gel with chemically bonded humic acid (Bonded humic acid column (BHAC)) was studied. The retention behavior of the fullerenes was measured under isocratic conditions with different mobile phase compositions, ranging from 0.05–0.70 (v/v) of toluene in cyclohexane. The column temperature was analysed in the range 35–75°C. The retention factors of the five fullerenes do not depend linearly on the toluene fraction but follow a quadratic relationship. The best chromatographic conditions for baseline separation of the five fullerenes were selected. The retention of the fullerenes on the HA stationary phase was strongly affected by temperature. Positive values of thermodynamic parameters (changes of enthalpy and entropy) were due to the abnormal solubility behaviour of fullerenes in toluene in the temperature range 35–75°C. The information obtained in this work makes this BHAC very simple to prepare and low cost, useful for fullerene research applications.
Keywords: Fullerenes; Humic acid; Stationary phase; Separation; Retention
Microwave assisted extraction of soy isoflavones by Mauricio A. Rostagno; Miguel Palma; Carmelo G. Barroso (pp. 274-282).
A fast and reliable analytical method using microwave assisted extraction has been developed. Several extraction solvents (methanol (MeOH) and ethanol (EtOH), 30–70% in water and water), temperatures (50–150°C), extraction solvent volume, as well as the sample size (1.0–0.1g) and extraction time (5–30min) were studied for the optimization of the extraction protocol. The optimized extraction conditions for quantitative recoveries were: 0.5g of sample, 50°C, 20min and 50% ethanol as extracting solvent. No degradation of the isoflavones was observed using the developed extraction protocol and a high reproducibility was achieved (>95%).
Keywords: Microwave assisted extraction; Soybeans; Isoflavones
Microwave assisted extraction of soy isoflavones by Mauricio A. Rostagno; Miguel Palma; Carmelo G. Barroso (pp. 274-282).
A fast and reliable analytical method using microwave assisted extraction has been developed. Several extraction solvents (methanol (MeOH) and ethanol (EtOH), 30–70% in water and water), temperatures (50–150°C), extraction solvent volume, as well as the sample size (1.0–0.1g) and extraction time (5–30min) were studied for the optimization of the extraction protocol. The optimized extraction conditions for quantitative recoveries were: 0.5g of sample, 50°C, 20min and 50% ethanol as extracting solvent. No degradation of the isoflavones was observed using the developed extraction protocol and a high reproducibility was achieved (>95%).
Keywords: Microwave assisted extraction; Soybeans; Isoflavones
Electrochemical oxidation of ochratoxin A at a glassy carbon electrode and in situ evaluation of the interaction with deoxyribonucleic acid using an electrochemical deoxyribonucleic acid-biosensor by S.C.B. Oliveira; V.C. Diculescu; G. Palleschi; D. Compagnone; A.M. Oliveira-Brett (pp. 283-291).
Ochratoxin A (OTA) is a fungal metabolite that occurs in foods, beverages, animal tissues, human blood and presents carcinogenic, teratogenic and nephrotoxic properties. This study concerns the redox properties of OTA using electrochemical techniques which have the potential for providing insights into the biological redox reactions of this molecule. The in situ evaluation of the OTA interaction with DNA using a DNA-electrochemical biosensor is also reported.The oxidation of OTA is an irreversible process proceeds with the transfer of one electron and one proton in a diffusion-controlled mechanism. The diffusion coefficient of OTA was calculated in pH 7 phosphate buffer to be DO=3.65×10−6cm2s−1. The oxidation of OTA is also pH dependent for electrolytes with pH<7 and involves the formation of a main oxidation product which adsorbs strongly at the GCE surface undergoing reversible oxidation. In alkaline electrolytes OTA undergoes chemical deprotonation, the oxidation involving only the transfer of one electron.The electrochemical dsDNA-biosensor was also used to evaluate the possible interaction between OTA and DNA. The experiments have clearly proven that OTA interacts and binds to dsDNA strands immobilized onto a GCE surface, but no evidence of DNA-damage caused by OTA was obtained.
Keywords: Ochratoxin A; Deoxyribonucleic acid; Oxidative damage; Oxidation; Voltammetry; Electroanalytical determination; Interferences
Electrochemical oxidation of ochratoxin A at a glassy carbon electrode and in situ evaluation of the interaction with deoxyribonucleic acid using an electrochemical deoxyribonucleic acid-biosensor by S.C.B. Oliveira; V.C. Diculescu; G. Palleschi; D. Compagnone; A.M. Oliveira-Brett (pp. 283-291).
Ochratoxin A (OTA) is a fungal metabolite that occurs in foods, beverages, animal tissues, human blood and presents carcinogenic, teratogenic and nephrotoxic properties. This study concerns the redox properties of OTA using electrochemical techniques which have the potential for providing insights into the biological redox reactions of this molecule. The in situ evaluation of the OTA interaction with DNA using a DNA-electrochemical biosensor is also reported.The oxidation of OTA is an irreversible process proceeds with the transfer of one electron and one proton in a diffusion-controlled mechanism. The diffusion coefficient of OTA was calculated in pH 7 phosphate buffer to be DO=3.65×10−6cm2s−1. The oxidation of OTA is also pH dependent for electrolytes with pH<7 and involves the formation of a main oxidation product which adsorbs strongly at the GCE surface undergoing reversible oxidation. In alkaline electrolytes OTA undergoes chemical deprotonation, the oxidation involving only the transfer of one electron.The electrochemical dsDNA-biosensor was also used to evaluate the possible interaction between OTA and DNA. The experiments have clearly proven that OTA interacts and binds to dsDNA strands immobilized onto a GCE surface, but no evidence of DNA-damage caused by OTA was obtained.
Keywords: Ochratoxin A; Deoxyribonucleic acid; Oxidative damage; Oxidation; Voltammetry; Electroanalytical determination; Interferences
Electrochemical biosensors for monitoring the recognition of glycoprotein–lectin interactions by Omowunmi A. Sadik; Fei Yan (pp. 292-296).
Despite the wide applicability and specificity of lectins to carbohydrate moieties, there are few lectin specific biosensors. This is attributed to the difficulty in defining the relevant experimental parameters to measure for sensing. We hereby describe the development of direct and indirect electrochemical sensors to determine the exact trace amounts of probarley lectin (ProBL) and its conversion product wheat germ agglutinin (WGA). In addition to WGA, the antigens (ProBL) employed in this study were over expressed in bacteria, isolated from protein bodies, and purified using immobilized N-acetylglusamine in order to obtain correctly folded active lectins. The amperometric immunosensor uses cell lines producing monoclonal antibody (mAB) to the pro-region of ProBL over expressed from Escherichia coli. The efficacy and sensing characteristics of the lectin were optimized using monoclonal antibody to WGA and the resulting sensor was found to detect only ProBL in the linear range 10−3–102μgmL−1 and a detection limit of 10−3μgmL−1.
Keywords: Lectins; Probarley lectin; Electrochemical sensors; Affinity
Electrochemical biosensors for monitoring the recognition of glycoprotein–lectin interactions by Omowunmi A. Sadik; Fei Yan (pp. 292-296).
Despite the wide applicability and specificity of lectins to carbohydrate moieties, there are few lectin specific biosensors. This is attributed to the difficulty in defining the relevant experimental parameters to measure for sensing. We hereby describe the development of direct and indirect electrochemical sensors to determine the exact trace amounts of probarley lectin (ProBL) and its conversion product wheat germ agglutinin (WGA). In addition to WGA, the antigens (ProBL) employed in this study were over expressed in bacteria, isolated from protein bodies, and purified using immobilized N-acetylglusamine in order to obtain correctly folded active lectins. The amperometric immunosensor uses cell lines producing monoclonal antibody (mAB) to the pro-region of ProBL over expressed from Escherichia coli. The efficacy and sensing characteristics of the lectin were optimized using monoclonal antibody to WGA and the resulting sensor was found to detect only ProBL in the linear range 10−3–102μgmL−1 and a detection limit of 10−3μgmL−1.
Keywords: Lectins; Probarley lectin; Electrochemical sensors; Affinity
Enhanced electrochemical performance at screen-printed carbon electrodes by a new pretreating procedure by Hang Wei; Jian-Jun Sun; Yu Xie; Cong-Gui Lin; Yan-Min Wang; Wen-Hui Yin; Guo-Nan Chen (pp. 297-303).
A new method for the pretreatment of screen-printed carbon electrodes (SPCEs) by two successive steps was proposed. In step one, fresh SPCEs were soaked into NaOH with high concentration (e.g. 3M) for tens to hundreds of minutes, and the resulted electrodes were called as SPCE-I. In step two, SPCE-I were pre-anodized in low concentration of NaOH, which were designated as SPCE-II. The pretreated electrodes showed remarkable enhancement in heterogeneous electron transfer rate constant ( k0) increased from 1.6×10−4cms−1 at the fresh SPCE to 1.1×10−2cms−1 at SPCE-I for Fe(CN)63−/4− couple. The peak to peak separation (Δ Ep) in cyclic voltammetry was reduced from ca. 480 to 84mV, indicating that the electrochemical reversibility was greatly promoted, possibly due to the removing of polymers/oil binder from the electrode surfaces. The electroactive area ( Aea) of the electrode was increased by a factor of 17 after pretreatment in step one. Further analysis by the electrochemical impedance method showed that the electron transfer resistance ( Rct) decreased from ca. 2100 to 1.4Ω. These pretreated electrodes, especially SPCE-II, exhibited excellent electrocatalytic behavior for the redox of dopamine (DA). Interference from ascorbic acid (AA) in the detection of DA at SPCE-II could be effectively eliminated due to the anodic peak separation (190mV) between DA and AA, which resulted from the functionalization of the electrode surface in the pretreatment of step two. Under optimum conditions, current responses to DA were linearly changed in two concentration intervals, one was from 3.0×10−7 to 9.8×10−6M, and the other was from 9.8×10−6 to 3.3×10−4M. The detection limit for DA was down to 1.0×10−7M.
Keywords: Screen-printed carbon electrodes; Pretreatment; Heterogeneous electron transfer rate constant; Electrochemical impedance; Dopamine
Enhanced electrochemical performance at screen-printed carbon electrodes by a new pretreating procedure by Hang Wei; Jian-Jun Sun; Yu Xie; Cong-Gui Lin; Yan-Min Wang; Wen-Hui Yin; Guo-Nan Chen (pp. 297-303).
A new method for the pretreatment of screen-printed carbon electrodes (SPCEs) by two successive steps was proposed. In step one, fresh SPCEs were soaked into NaOH with high concentration (e.g. 3M) for tens to hundreds of minutes, and the resulted electrodes were called as SPCE-I. In step two, SPCE-I were pre-anodized in low concentration of NaOH, which were designated as SPCE-II. The pretreated electrodes showed remarkable enhancement in heterogeneous electron transfer rate constant ( k0) increased from 1.6×10−4cms−1 at the fresh SPCE to 1.1×10−2cms−1 at SPCE-I for Fe(CN)63−/4− couple. The peak to peak separation (Δ Ep) in cyclic voltammetry was reduced from ca. 480 to 84mV, indicating that the electrochemical reversibility was greatly promoted, possibly due to the removing of polymers/oil binder from the electrode surfaces. The electroactive area ( Aea) of the electrode was increased by a factor of 17 after pretreatment in step one. Further analysis by the electrochemical impedance method showed that the electron transfer resistance ( Rct) decreased from ca. 2100 to 1.4Ω. These pretreated electrodes, especially SPCE-II, exhibited excellent electrocatalytic behavior for the redox of dopamine (DA). Interference from ascorbic acid (AA) in the detection of DA at SPCE-II could be effectively eliminated due to the anodic peak separation (190mV) between DA and AA, which resulted from the functionalization of the electrode surface in the pretreatment of step two. Under optimum conditions, current responses to DA were linearly changed in two concentration intervals, one was from 3.0×10−7 to 9.8×10−6M, and the other was from 9.8×10−6 to 3.3×10−4M. The detection limit for DA was down to 1.0×10−7M.
Keywords: Screen-printed carbon electrodes; Pretreatment; Heterogeneous electron transfer rate constant; Electrochemical impedance; Dopamine
High performance liquid chromatography/ion-trap mass spectrometry for separation and simultaneous determination of ethynylestradiol, gestodene, levonorgestrel, cyproterone acetate and desogestrel by David Matějíček; Vlastimil Kubáň (pp. 304-315).
A fast and highly sensitive high performance liquid chromatographic/ion-trap mass spectrometric method (LC/MS) has been developed for simultaneous determination of ethynylestradiol (EE2), gestodene (GES), levonorgestrel (LNG), cyproterone acetate (CPA) and desogestrel (DES). Among three types of sorbents tested (C8, C18 and phenyl) from two suppliers, the best separation was achieved on reverse phase Zorbax SB-Phenyl column using aqueous methanol as a mobile phase. A linear gradient profile from 70 up to 100% (v/v) in 7th min, kept constant at 100% up to 10th min and followed by a negative gradient to 70% of methanol up to 12th min was used for elution. Applicability of electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) and influence of the mobile phase composition, its flow rate, capillary/vaporizer temperature of API source and in-source fragmentor voltage ionization are discussed. The on-column limits of quantification (10S/N) were 300pg of EE2, 14pg of GES and LNG, 4pg of CPA and 960pg of DES per injection (1μL) using APCI with data collection in selected ion monitoring (SIM) mode. The analytical performance of the method was evaluated using the determination of EE2, GES, LNG, CPA and DES in contraceptives and river water samples.
Keywords: Liquid chromatography; Ion-trap mass spectrometry; Electrospray ionization; Atmospheric pressure chemical ionization; Ethynylestradiol; Gestodene; Levonorgestrel; Cyproterone acetate; Desogestrel
High performance liquid chromatography/ion-trap mass spectrometry for separation and simultaneous determination of ethynylestradiol, gestodene, levonorgestrel, cyproterone acetate and desogestrel by David Matějíček; Vlastimil Kubáň (pp. 304-315).
A fast and highly sensitive high performance liquid chromatographic/ion-trap mass spectrometric method (LC/MS) has been developed for simultaneous determination of ethynylestradiol (EE2), gestodene (GES), levonorgestrel (LNG), cyproterone acetate (CPA) and desogestrel (DES). Among three types of sorbents tested (C8, C18 and phenyl) from two suppliers, the best separation was achieved on reverse phase Zorbax SB-Phenyl column using aqueous methanol as a mobile phase. A linear gradient profile from 70 up to 100% (v/v) in 7th min, kept constant at 100% up to 10th min and followed by a negative gradient to 70% of methanol up to 12th min was used for elution. Applicability of electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) and influence of the mobile phase composition, its flow rate, capillary/vaporizer temperature of API source and in-source fragmentor voltage ionization are discussed. The on-column limits of quantification (10S/N) were 300pg of EE2, 14pg of GES and LNG, 4pg of CPA and 960pg of DES per injection (1μL) using APCI with data collection in selected ion monitoring (SIM) mode. The analytical performance of the method was evaluated using the determination of EE2, GES, LNG, CPA and DES in contraceptives and river water samples.
Keywords: Liquid chromatography; Ion-trap mass spectrometry; Electrospray ionization; Atmospheric pressure chemical ionization; Ethynylestradiol; Gestodene; Levonorgestrel; Cyproterone acetate; Desogestrel
Determination of dye precursors in hair coloring products by liquid chromatography with electrochemical detection by Motoko Narita; Kazuo Murakami; Jean-Michel Kauffmann (pp. 316-320).
The simultaneous determination of seven aminophenols, resorcinol and p-phenylenediamine in hair coloring products was performed by liquid chromatography (HPLC) with amperometric detection (ED). The aminophenols were separated on a ODS C18 reversed-phase column by isocratic elution with a mobile phase based on 0.1M acetate buffer pH 4.5–methanol (90:10%, v/v) at a flow rate 0.8mLmin−1. The limit of detection (S/N=3) for the aminophenols was in the 15–40pg (injected mass) range at an applied potential of 0.950V versus Ag/AgCl. Peak heights for the aminophenols and the two others compounds were found to be linearly related to the amount injected, from 0.3 to 300ng ( r>0.994–0.999).The relative standard deviation (R.S.D., n=10) for 1ng injected was comprised in the range from 2.5 to 6.2%, depending on the aminophenol tested. The present method minimizes troublesome and time-consuming pretreatment procedures and it was applied to the determination of aminophenols, resorcinol and phenylenediamine in hair coloring formulations.
Keywords: Aminophenol; Hair; Dye; Analysis; Liquid chromatography
Determination of dye precursors in hair coloring products by liquid chromatography with electrochemical detection by Motoko Narita; Kazuo Murakami; Jean-Michel Kauffmann (pp. 316-320).
The simultaneous determination of seven aminophenols, resorcinol and p-phenylenediamine in hair coloring products was performed by liquid chromatography (HPLC) with amperometric detection (ED). The aminophenols were separated on a ODS C18 reversed-phase column by isocratic elution with a mobile phase based on 0.1M acetate buffer pH 4.5–methanol (90:10%, v/v) at a flow rate 0.8mLmin−1. The limit of detection (S/N=3) for the aminophenols was in the 15–40pg (injected mass) range at an applied potential of 0.950V versus Ag/AgCl. Peak heights for the aminophenols and the two others compounds were found to be linearly related to the amount injected, from 0.3 to 300ng ( r>0.994–0.999).The relative standard deviation (R.S.D., n=10) for 1ng injected was comprised in the range from 2.5 to 6.2%, depending on the aminophenol tested. The present method minimizes troublesome and time-consuming pretreatment procedures and it was applied to the determination of aminophenols, resorcinol and phenylenediamine in hair coloring formulations.
Keywords: Aminophenol; Hair; Dye; Analysis; Liquid chromatography