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Analytica Chimica Acta (v.589, #2)
Solubilisation and binding characteristics of a recombinant β2-adrenergic receptor expressed in the membrane of Escherichia coli for the multianalyte detection of β-agonists and antagonists residues in food-producing animals by Sophie Danyi; Guy Degand; Colette Duez; Benoît Granier; Guy Maghuin-Rogister; Marie-Louise Scippo (pp. 159-165).
The number of substances with β-agonistic activity, illegally introduced in meat production or in sports doping as anabolic or β-blocking agents is increasing. Analytical methods suited for their multianalyte detection are thus necessary. In this perspective, receptor assays were developed. The research activities undertaken in this study describe the solubilisation of a recombinant human β2-adrenergic receptor produced in the inner membrane of genetically modified Escherichia coli, using the detergent n-dodecyl-β-d-maltoside. Its potential to detect the presence of β-agonists or β-blockers in biological samples was evaluated. The solubilised β2-adrenergic receptor retained its binding affinity in a radio-receptor assay based on the competition for the binding to receptors between a ligand (β-agonist or antagonist) and the radioligand [125I]iodocyanopindolol. The IC50 values ranged from 5±1×10−8M (clenbuterol) to 8±2×10−6M (isoxsuprine) for the β-agonists tested and from 1.5±0.2×10−10M (carazolol) to 1.2±0.2×10−5M (metoprolol) for the β-blockers tested. It was shown to have a lower limit of detection than a radio-receptor assay using the solubilised β2-adrenoceptor expressed in a mammalian cell line. The solubilised recombinant human β2-adrenoreceptor expressed in E. coli would be a useful tool to develop non radioactive multianalyte screening methods.
Keywords: β-Adrenergic receptors; β-Agonists; β-Blockers; Receptor-based assays; Membrane protein solubilisation
Solubilisation and binding characteristics of a recombinant β2-adrenergic receptor expressed in the membrane of Escherichia coli for the multianalyte detection of β-agonists and antagonists residues in food-producing animals by Sophie Danyi; Guy Degand; Colette Duez; Benoît Granier; Guy Maghuin-Rogister; Marie-Louise Scippo (pp. 159-165).
The number of substances with β-agonistic activity, illegally introduced in meat production or in sports doping as anabolic or β-blocking agents is increasing. Analytical methods suited for their multianalyte detection are thus necessary. In this perspective, receptor assays were developed. The research activities undertaken in this study describe the solubilisation of a recombinant human β2-adrenergic receptor produced in the inner membrane of genetically modified Escherichia coli, using the detergent n-dodecyl-β-d-maltoside. Its potential to detect the presence of β-agonists or β-blockers in biological samples was evaluated. The solubilised β2-adrenergic receptor retained its binding affinity in a radio-receptor assay based on the competition for the binding to receptors between a ligand (β-agonist or antagonist) and the radioligand [125I]iodocyanopindolol. The IC50 values ranged from 5±1×10−8M (clenbuterol) to 8±2×10−6M (isoxsuprine) for the β-agonists tested and from 1.5±0.2×10−10M (carazolol) to 1.2±0.2×10−5M (metoprolol) for the β-blockers tested. It was shown to have a lower limit of detection than a radio-receptor assay using the solubilised β2-adrenoceptor expressed in a mammalian cell line. The solubilised recombinant human β2-adrenoreceptor expressed in E. coli would be a useful tool to develop non radioactive multianalyte screening methods.
Keywords: β-Adrenergic receptors; β-Agonists; β-Blockers; Receptor-based assays; Membrane protein solubilisation
Highly sensitive phage-based biosensor for the detection of β-galactosidase by Viswaprakash Nanduri; Shankar Balasubramanian; Srinivas Sista; Vitaly J. Vodyanoy; Aleksandr L. Simonian (pp. 166-172).
Development of real-time sensor based on the target-specific probe that make possible sensitive, rapid and selective detection and monitoring of the particular antigen molecules could be of substantial importance to the many applications. Because of its high specificity to the target molecules, excellent temperature stability, and easy production, bacterial phage might serve as a powerful biorecognition probe in biosensor applications. Here, we report extremely sensitive and specific label-free direct detection of model antigen, β-galactosidase (β-gal), based on surface plasmon resonance (SPR) spectroscopy. The β-gal specific landscape phage 1G40 has been immobilized on the gold surface of SPR SPREETA™ sensor chip through physical adsorption [V. Nanduri, A.M. Samoylova, V.Petrenko, V. Vodyanoy and A.L.Simonian, Comparison of optical and acoustic wave phage biosensors, 206th Meeting of The Electrochemical Society, Honolulu, Hawaii, October 3–8, (2004)]. Another non-specific to the β-gal phage, a wild-type phage F8-5, was used in the reference channel. The concentration-dependent binding of β-gal in both channels were assessed by monitoring the sensor optical response as a function of time under different experimental conditions, and the concentration of β-gal was computed in differential mode. Concentrations of β-gal between 10−12M and 10−7M could be readily detected, with linear part of calibration curve between 10−9M and 10−6M. When β-gal was pre-incubated with different concentrations of free 1G40 phage prior to exposure to the biosensor, concentration-dependent inhibition was observed, indicating on biosensor high specificity toward β-gal. Apart from a flow through mode used to deliver the samples to the surface for the SPR sensor, batch mode sensing was also employed to study the binding of β-gal to immobilized phage on the SPR sensor surface. Experiments using a flow through mode provided more consistent results in the full dose range and showed higher sensitivity as opposed to the batch mode studies. The mean Kd and binding valences for the flow through mode studies was 1.3±0.001nM and 1.5±0.03, in comparison to 26±0.003nM and 2.4±0.01 for the batch mode studies. The average thickness of phage 1G40 adlayer deposited through flow through and batch mode was 3±0.002 and 0.66±0.001nm, respectively.
Keywords: Surface plasmon resonance; Sensor; β-Galactosidase; Filamentous bacteriophage; Biosensor
Highly sensitive phage-based biosensor for the detection of β-galactosidase by Viswaprakash Nanduri; Shankar Balasubramanian; Srinivas Sista; Vitaly J. Vodyanoy; Aleksandr L. Simonian (pp. 166-172).
Development of real-time sensor based on the target-specific probe that make possible sensitive, rapid and selective detection and monitoring of the particular antigen molecules could be of substantial importance to the many applications. Because of its high specificity to the target molecules, excellent temperature stability, and easy production, bacterial phage might serve as a powerful biorecognition probe in biosensor applications. Here, we report extremely sensitive and specific label-free direct detection of model antigen, β-galactosidase (β-gal), based on surface plasmon resonance (SPR) spectroscopy. The β-gal specific landscape phage 1G40 has been immobilized on the gold surface of SPR SPREETA™ sensor chip through physical adsorption [V. Nanduri, A.M. Samoylova, V.Petrenko, V. Vodyanoy and A.L.Simonian, Comparison of optical and acoustic wave phage biosensors, 206th Meeting of The Electrochemical Society, Honolulu, Hawaii, October 3–8, (2004)]. Another non-specific to the β-gal phage, a wild-type phage F8-5, was used in the reference channel. The concentration-dependent binding of β-gal in both channels were assessed by monitoring the sensor optical response as a function of time under different experimental conditions, and the concentration of β-gal was computed in differential mode. Concentrations of β-gal between 10−12M and 10−7M could be readily detected, with linear part of calibration curve between 10−9M and 10−6M. When β-gal was pre-incubated with different concentrations of free 1G40 phage prior to exposure to the biosensor, concentration-dependent inhibition was observed, indicating on biosensor high specificity toward β-gal. Apart from a flow through mode used to deliver the samples to the surface for the SPR sensor, batch mode sensing was also employed to study the binding of β-gal to immobilized phage on the SPR sensor surface. Experiments using a flow through mode provided more consistent results in the full dose range and showed higher sensitivity as opposed to the batch mode studies. The mean Kd and binding valences for the flow through mode studies was 1.3±0.001nM and 1.5±0.03, in comparison to 26±0.003nM and 2.4±0.01 for the batch mode studies. The average thickness of phage 1G40 adlayer deposited through flow through and batch mode was 3±0.002 and 0.66±0.001nm, respectively.
Keywords: Surface plasmon resonance; Sensor; β-Galactosidase; Filamentous bacteriophage; Biosensor
Multiple enzyme linked immunosorbent assay system on a capillary-assembled microchip integrating valving and immuno-reaction functions by Terence G. Henares; Shun-ichi Funano; Shigeru Terabe; Fumio Mizutani; Ryuichi Sekizawa; Hideaki Hisamoto (pp. 173-179).
Multiple enzyme linked immunosorbent assay (ELISA) chip is developed by using capillary-assembled microchip (CAs-CHIP) technique, which involves simple embedding of 2–3mm length of square capillaries possessing valving and immuno-reaction functions into the microchannels fabricated on a PDMS substrate. In contrast to the previously reported ELISA chips, our system enables not only the flexible design of the multi-ELISA chip required for many different diagnostic purposes, but also the valving operation required for a reliable analysis. Here, a thermo-responsive polymer-immobilized capillary was used together with a small Peltier device, as a valving part, and different antibody-immobilized capillaries were used as immuno-reaction part. Sample solution and detecting reagent solutions were sequentially introduced through the valving capillary, and the valve is closed to completely stop the solution flow inside the immuno-reaction capillaries and detected using thermal lens microscope (TLM). Different anti-IgGs (human, goat, chicken) were immobilized and used as ELISA parts of CAs-CHIP. Sequential introductions of the mixed IgG solution, mixed enzyme–antibody solution and substrate solution facilitated the multiple determinations of 0.1ngmL−1 IgGs (human, goat, chicken) with total analysis time of about 30min. The valve-integrated multi-ELISA chip developed here can be applied for many different diagnostic purposes by using different immuno-reaction capillaries necessary for a specific clinical diagnostic application.
Keywords: Capillary-assembled microchip; Microfluidic immunoassay; Microvalve; Multiple enzyme linked immunosorbent assay; Square capillary
Multiple enzyme linked immunosorbent assay system on a capillary-assembled microchip integrating valving and immuno-reaction functions by Terence G. Henares; Shun-ichi Funano; Shigeru Terabe; Fumio Mizutani; Ryuichi Sekizawa; Hideaki Hisamoto (pp. 173-179).
Multiple enzyme linked immunosorbent assay (ELISA) chip is developed by using capillary-assembled microchip (CAs-CHIP) technique, which involves simple embedding of 2–3mm length of square capillaries possessing valving and immuno-reaction functions into the microchannels fabricated on a PDMS substrate. In contrast to the previously reported ELISA chips, our system enables not only the flexible design of the multi-ELISA chip required for many different diagnostic purposes, but also the valving operation required for a reliable analysis. Here, a thermo-responsive polymer-immobilized capillary was used together with a small Peltier device, as a valving part, and different antibody-immobilized capillaries were used as immuno-reaction part. Sample solution and detecting reagent solutions were sequentially introduced through the valving capillary, and the valve is closed to completely stop the solution flow inside the immuno-reaction capillaries and detected using thermal lens microscope (TLM). Different anti-IgGs (human, goat, chicken) were immobilized and used as ELISA parts of CAs-CHIP. Sequential introductions of the mixed IgG solution, mixed enzyme–antibody solution and substrate solution facilitated the multiple determinations of 0.1ngmL−1 IgGs (human, goat, chicken) with total analysis time of about 30min. The valve-integrated multi-ELISA chip developed here can be applied for many different diagnostic purposes by using different immuno-reaction capillaries necessary for a specific clinical diagnostic application.
Keywords: Capillary-assembled microchip; Microfluidic immunoassay; Microvalve; Multiple enzyme linked immunosorbent assay; Square capillary
Selective separation of hydroxy polychlorinated biphenyls (HO-PCBs) by the structural recognition on the molecularly imprinted polymers: Direct separation of the thyroid hormone active analogues from mixtures by Takuya Kubo; Hideyuki Matsumoto; Fujio Shiraishi; Makoto Nomachi; Koji Nemoto; Ken Hosoya; Kunimitsu Kaya (pp. 180-185).
We developed novel separation media for hydroxy polychlorinated biphenyls (HO-PCBs) using the molecular imprinting techniques. The results of evaluation for the molecularly imprinted polymers (MIPs) by the liquid chromatography (LC) suggested that MIPs had selective separation ability for certain HO-PCB analogues. The results of the LC evaluations and molecular modeling indicated that the molecular volumes and pKa values of template molecules were related with the retention factor of HO-PCBs. Additionally, according to the detail evaluation toward the selective separation behaviors of MIPs, these HO-PCB analogues have low pKa values dependent on their chemical structures. In other words, the prepared MIPs had selective recognition ability against the analogues, which have an OH group on a phenyl carbon and two chlorine atoms on the both neighboring carbons of the carbon attached with the OH group. Moreover, these analogues may have a potential for thyroid hormone activities so that we attempted to separate these analogues directly from mixtures of HO-PCBs using a prepared MIP.
Keywords: Hydroxy polychlorinated biphenyl (HO-PCB); Molecular imprinting; Selective separation; p; K; a; Thyroid hormone activity
Selective separation of hydroxy polychlorinated biphenyls (HO-PCBs) by the structural recognition on the molecularly imprinted polymers: Direct separation of the thyroid hormone active analogues from mixtures by Takuya Kubo; Hideyuki Matsumoto; Fujio Shiraishi; Makoto Nomachi; Koji Nemoto; Ken Hosoya; Kunimitsu Kaya (pp. 180-185).
We developed novel separation media for hydroxy polychlorinated biphenyls (HO-PCBs) using the molecular imprinting techniques. The results of evaluation for the molecularly imprinted polymers (MIPs) by the liquid chromatography (LC) suggested that MIPs had selective separation ability for certain HO-PCB analogues. The results of the LC evaluations and molecular modeling indicated that the molecular volumes and pKa values of template molecules were related with the retention factor of HO-PCBs. Additionally, according to the detail evaluation toward the selective separation behaviors of MIPs, these HO-PCB analogues have low pKa values dependent on their chemical structures. In other words, the prepared MIPs had selective recognition ability against the analogues, which have an OH group on a phenyl carbon and two chlorine atoms on the both neighboring carbons of the carbon attached with the OH group. Moreover, these analogues may have a potential for thyroid hormone activities so that we attempted to separate these analogues directly from mixtures of HO-PCBs using a prepared MIP.
Keywords: Hydroxy polychlorinated biphenyl (HO-PCB); Molecular imprinting; Selective separation; p; K; a; Thyroid hormone activity
Use of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide for rapid detection of methicillin-resistant Staphylococcus aureus by resonance light scattering by Jian Bo Xiao; Jing Wen Chen; Feng Lian Ren; Chun Sheng Yang; Ming Xu (pp. 186-191).
A rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) using resonance light scattering (RLS) on an ordinary fluorescence spectrometer was developed. The viable MRSA reduced 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to produce insoluble particles which displayed intense resonance scattering light. It showed a linear relationship between the number of viable MRSA and the RLS intensity. Dead MRSA were unable to reduce MTT. MRSA exposed to flavonoids extracted from Marchantia convoluta (MCF) showed a MCF concentration-dependent inhibition of the ability to reduce MTT. The RLS could, in combination with the MTT assay, be a rapid and sensitive detection method for vitro-cultured MRSA.
Keywords: Methicillin-resistant; Staphylococcus aureus; Resonance light scattering; Detection
Use of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide for rapid detection of methicillin-resistant Staphylococcus aureus by resonance light scattering by Jian Bo Xiao; Jing Wen Chen; Feng Lian Ren; Chun Sheng Yang; Ming Xu (pp. 186-191).
A rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) using resonance light scattering (RLS) on an ordinary fluorescence spectrometer was developed. The viable MRSA reduced 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to produce insoluble particles which displayed intense resonance scattering light. It showed a linear relationship between the number of viable MRSA and the RLS intensity. Dead MRSA were unable to reduce MTT. MRSA exposed to flavonoids extracted from Marchantia convoluta (MCF) showed a MCF concentration-dependent inhibition of the ability to reduce MTT. The RLS could, in combination with the MTT assay, be a rapid and sensitive detection method for vitro-cultured MRSA.
Keywords: Methicillin-resistant; Staphylococcus aureus; Resonance light scattering; Detection
Raman spectroscopic method for the determination of medroxyprogesterone acetate in a pharmaceutical suspension: validation of quantifying abilities, uncertainty assessment and comparison with the high performance liquid chromatography reference method by T.R.M. De Beer; W.R.G. Baeyens; A. Vermeire; D. Broes; J.P. Remon; C. Vervaet (pp. 192-199).
An alternative fast and non-destructive validated Raman spectroscopic analytical procedure, requiring no sample preparation, was compared with the industrially applied HPLC reference method (Pfizer Manufacturing Belgium) for the quantitative determination of medroxyprogesterone acetate (MPA) in DepoProvera® suspensions (150mgmL−1, Pfizer). The Raman calibration model was developed by plotting the peak intensity of the baseline-corrected and normalized spectral band (corrected by external standard measurements) between 1595 and 1620cm−1 against known MPA concentrations in standards. At this band, no spectral interferences from the suspension medium are observed. The most suitable model for the calibration data (straight line or higher order polynomial) was determined by evaluating the fit and predictive properties of the models. In a second step, the developed Raman spectroscopic analytical method was validated by calculating the accuracy profile on the basis of the analysis results of validation samples. Furthermore, based on the data of the accuracy profile, the measurement uncertainty was determined. Finally, as the aim of the alternative method is to replace the destructive, time-consuming HPLC method, requiring sample preparation, it needs to be demonstrated that the new Raman method performs at least as good as the HPLC method. Therefore, the performance (precision and bias) of both methods was compared.A second order polynomial calibration curve through the calibration data supplies the best predictive properties and gives an acceptable fit. From the accuracy profile, it was concluded that at the target concentration (150mgmL−1), 95 out 100 future routine measurements will be included within the acceptance limits (5%). Comparison of the alternative method with the reference method at the target concentration indicates that the Raman method performs at least as good as the HPLC method for precision (repeatability and intermediate precision) and bias. The fast and non-destructive Raman method hence provides an alternative for the destructive and time-consuming HPLC procedure.
Keywords: Raman spectroscopy; Medroxyprogesterone acetate; Pharmaceutical suspension; Accuracy profile; Uncertainty measurement; Comparison; Alternative measurement method; Polynomial curve
Raman spectroscopic method for the determination of medroxyprogesterone acetate in a pharmaceutical suspension: validation of quantifying abilities, uncertainty assessment and comparison with the high performance liquid chromatography reference method by T.R.M. De Beer; W.R.G. Baeyens; A. Vermeire; D. Broes; J.P. Remon; C. Vervaet (pp. 192-199).
An alternative fast and non-destructive validated Raman spectroscopic analytical procedure, requiring no sample preparation, was compared with the industrially applied HPLC reference method (Pfizer Manufacturing Belgium) for the quantitative determination of medroxyprogesterone acetate (MPA) in DepoProvera® suspensions (150mgmL−1, Pfizer). The Raman calibration model was developed by plotting the peak intensity of the baseline-corrected and normalized spectral band (corrected by external standard measurements) between 1595 and 1620cm−1 against known MPA concentrations in standards. At this band, no spectral interferences from the suspension medium are observed. The most suitable model for the calibration data (straight line or higher order polynomial) was determined by evaluating the fit and predictive properties of the models. In a second step, the developed Raman spectroscopic analytical method was validated by calculating the accuracy profile on the basis of the analysis results of validation samples. Furthermore, based on the data of the accuracy profile, the measurement uncertainty was determined. Finally, as the aim of the alternative method is to replace the destructive, time-consuming HPLC method, requiring sample preparation, it needs to be demonstrated that the new Raman method performs at least as good as the HPLC method. Therefore, the performance (precision and bias) of both methods was compared.A second order polynomial calibration curve through the calibration data supplies the best predictive properties and gives an acceptable fit. From the accuracy profile, it was concluded that at the target concentration (150mgmL−1), 95 out 100 future routine measurements will be included within the acceptance limits (5%). Comparison of the alternative method with the reference method at the target concentration indicates that the Raman method performs at least as good as the HPLC method for precision (repeatability and intermediate precision) and bias. The fast and non-destructive Raman method hence provides an alternative for the destructive and time-consuming HPLC procedure.
Keywords: Raman spectroscopy; Medroxyprogesterone acetate; Pharmaceutical suspension; Accuracy profile; Uncertainty measurement; Comparison; Alternative measurement method; Polynomial curve
A new method for testing synthetic drugs adulterated in herbal medicines based on infrared spectroscopy by Lu Feng; Li Shu; Le Jian; Chen Guiliang; Cao Yan; Qi Yunpeng; Chai Yifeng; Wu Yutian (pp. 200-207).
Developing a simple and fast method to analyze possibly adulterated synthetic drugs in suspected herbal medicines (HM) is both methodologically and commercially significant. This paper constructs a new approach named local straight-line screening (LSLS), to the solution of the problem, after carefully observing the characteristics of the spectral line shapes. LSLS can be applied to both the qualitative and quantitative analysis of suspected HM, based solely on infrared spectrum of the possible synthetic drug and the suspected HM without any sample pretreatment. The concept and the application of the method are exemplified by analysis of sibutramine hydrochloride (SH), an anti-obesity medicine, adulterated in some commercially available HM-based diet pills, and compared with MSFDSS, and SNICA methods. The results show that, despite highly overlapping spectra and unresolved data, it is possible with LSLS to obtain an accurate discrimination and determination of SH in the HM-based diet pills. This allows the method to be potentially used in the primary screening of other synthetic drugs suspiciously adulterated in HM, with high rapidity, accuracy and cost-effectiveness.
Keywords: Local straight-line screening method; Adulteration; Infrared spectroscopy; Synthetic drugs; Herbal medicines
A new method for testing synthetic drugs adulterated in herbal medicines based on infrared spectroscopy by Lu Feng; Li Shu; Le Jian; Chen Guiliang; Cao Yan; Qi Yunpeng; Chai Yifeng; Wu Yutian (pp. 200-207).
Developing a simple and fast method to analyze possibly adulterated synthetic drugs in suspected herbal medicines (HM) is both methodologically and commercially significant. This paper constructs a new approach named local straight-line screening (LSLS), to the solution of the problem, after carefully observing the characteristics of the spectral line shapes. LSLS can be applied to both the qualitative and quantitative analysis of suspected HM, based solely on infrared spectrum of the possible synthetic drug and the suspected HM without any sample pretreatment. The concept and the application of the method are exemplified by analysis of sibutramine hydrochloride (SH), an anti-obesity medicine, adulterated in some commercially available HM-based diet pills, and compared with MSFDSS, and SNICA methods. The results show that, despite highly overlapping spectra and unresolved data, it is possible with LSLS to obtain an accurate discrimination and determination of SH in the HM-based diet pills. This allows the method to be potentially used in the primary screening of other synthetic drugs suspiciously adulterated in HM, with high rapidity, accuracy and cost-effectiveness.
Keywords: Local straight-line screening method; Adulteration; Infrared spectroscopy; Synthetic drugs; Herbal medicines
Use of linear discriminant analysis applied to vibrational spectroscopy data to characterize commercial varnishes employed for art purposes by J. Peris-Vicente; M.J. Lerma-García; E. Simó-Alfonso; J.V. Gimeno-Adelantado; M.T. Doménech-Carbó (pp. 208-215).
An improvement of methodologies for characterising synthetic resins used in varnishes employed for art purposes has been suggested. Several kinds of standard of the most common polymeric resins (acrylic, vinyl, poly(vinyl alcohol), alkyd, cellulose nitrate, latex, polyester, polyurethane, epoxy, organosilicic, and ketonic) were analyzed by Fourier transform infrared (FTIR) spectroscopy. Synthetic resins characterization is based on the mathematical treatment of their whole spectrum, dividing it in 13 sections, avoiding the one-by-one interpretation of the absorption bands. The mathematical model takes as variables the maximal absorbance of each section, and each synthetic standard resin as categories. Two exploratory analysis methods, Hierarchical Clustering and Principal Component Analysis (PCA), and a classificatory chemometric tool, linear discriminant analysis (LDA), are tested, validating the models by leave-one-out method. LDA is proved to be a powerful tool for grouping objects in categories, providing a satisfactory distinction of polymeric resin standards. The described analytical procedure has successfully been applied to characterization of synthetic resins contained in commercial varnishes.
Keywords: Polymer; Synthetic resins; Varnishes; Fourier transform infrared spectroscopy; Linear discriminant analysis
Use of linear discriminant analysis applied to vibrational spectroscopy data to characterize commercial varnishes employed for art purposes by J. Peris-Vicente; M.J. Lerma-García; E. Simó-Alfonso; J.V. Gimeno-Adelantado; M.T. Doménech-Carbó (pp. 208-215).
An improvement of methodologies for characterising synthetic resins used in varnishes employed for art purposes has been suggested. Several kinds of standard of the most common polymeric resins (acrylic, vinyl, poly(vinyl alcohol), alkyd, cellulose nitrate, latex, polyester, polyurethane, epoxy, organosilicic, and ketonic) were analyzed by Fourier transform infrared (FTIR) spectroscopy. Synthetic resins characterization is based on the mathematical treatment of their whole spectrum, dividing it in 13 sections, avoiding the one-by-one interpretation of the absorption bands. The mathematical model takes as variables the maximal absorbance of each section, and each synthetic standard resin as categories. Two exploratory analysis methods, Hierarchical Clustering and Principal Component Analysis (PCA), and a classificatory chemometric tool, linear discriminant analysis (LDA), are tested, validating the models by leave-one-out method. LDA is proved to be a powerful tool for grouping objects in categories, providing a satisfactory distinction of polymeric resin standards. The described analytical procedure has successfully been applied to characterization of synthetic resins contained in commercial varnishes.
Keywords: Polymer; Synthetic resins; Varnishes; Fourier transform infrared spectroscopy; Linear discriminant analysis
Independent component analysis as a pretreatment method for parallel factor analysis to eliminate artefacts from multiway data by Delphine Jouan-Rimbaud Bouveresse; Hamida Benabid; Douglas N. Rutledge (pp. 216-224).
Parallel factor analysis (PARAFAC) has successfully been used in many applications for the analysis of excitation–emission fluorescence data. However, some measurement “artefacts”, such as Rayleigh or Raman scattering, can pose a problem for the extraction of the PARAFAC components and their interpretation. Replacing the spectral zones corresponding to these signals by missing values in the data is not necessarily a method of choice in the cases where informative signals lie in the same wavelength regions. In this article, independent component analysis (ICA) is used on the unfolded cubic array, and the independent components related to the Rayleigh and Raman scattering are identified and removed prior to the reconstruction of the excitation–emission fluorescence data cube. PARAFAC is then applied on these data reconstructed after selective artefact removal, and satisfactory models can be obtained. This procedure, although particularly useful for 3D fluorescence data, may be applied to other types of data as well.
Keywords: Independent component analysis; 3D-Fluorescence; Excitation–emission matrix; Parallel factor analysis; Rayleigh and Raman scattering
Independent component analysis as a pretreatment method for parallel factor analysis to eliminate artefacts from multiway data by Delphine Jouan-Rimbaud Bouveresse; Hamida Benabid; Douglas N. Rutledge (pp. 216-224).
Parallel factor analysis (PARAFAC) has successfully been used in many applications for the analysis of excitation–emission fluorescence data. However, some measurement “artefacts”, such as Rayleigh or Raman scattering, can pose a problem for the extraction of the PARAFAC components and their interpretation. Replacing the spectral zones corresponding to these signals by missing values in the data is not necessarily a method of choice in the cases where informative signals lie in the same wavelength regions. In this article, independent component analysis (ICA) is used on the unfolded cubic array, and the independent components related to the Rayleigh and Raman scattering are identified and removed prior to the reconstruction of the excitation–emission fluorescence data cube. PARAFAC is then applied on these data reconstructed after selective artefact removal, and satisfactory models can be obtained. This procedure, although particularly useful for 3D fluorescence data, may be applied to other types of data as well.
Keywords: Independent component analysis; 3D-Fluorescence; Excitation–emission matrix; Parallel factor analysis; Rayleigh and Raman scattering
Headspace liquid-phase microextraction of methamphetamine and amphetamine in urine by an aqueous drop by Yi He; Angelica Vargas; Youn-Jung Kang (pp. 225-230).
This study developed a headspace liquid-phase microextraction (LPME) method by using a single aqueous drop in combination with high performance liquid chromatography (HPLC)-UV detection for the determination of methamphetamine (MAP) and amphetamine (AP) in urine samples. The analytes, volatile and basic, were released from sample matrix into the headspace first, and then protonated and dissolved in an aqueous H3PO4 drop hanging in the headspace by a HPLC syringe. After extraction, this drop was directly injected into HPLC. Parameters affecting extraction efficiency were investigated and optimized. This method showed good linearity in the investigated concentration range of 1.0–1500μgL−1, repeatability of the extraction (R.S.D.<5%, n=6), and low detection limits (0.3μgL−1 for both analytes). Enrichment factors of about 400-fold and 220-fold were achieved for MAP and AP, respectively, at optimum conditions. The feasibility of the method was demonstrated by analyzing human urine samples.
Keywords: Headspace liquid-phase microextraction; Aqueous drop; Methamphetamine; Amphetamine; Urine
Headspace liquid-phase microextraction of methamphetamine and amphetamine in urine by an aqueous drop by Yi He; Angelica Vargas; Youn-Jung Kang (pp. 225-230).
This study developed a headspace liquid-phase microextraction (LPME) method by using a single aqueous drop in combination with high performance liquid chromatography (HPLC)-UV detection for the determination of methamphetamine (MAP) and amphetamine (AP) in urine samples. The analytes, volatile and basic, were released from sample matrix into the headspace first, and then protonated and dissolved in an aqueous H3PO4 drop hanging in the headspace by a HPLC syringe. After extraction, this drop was directly injected into HPLC. Parameters affecting extraction efficiency were investigated and optimized. This method showed good linearity in the investigated concentration range of 1.0–1500μgL−1, repeatability of the extraction (R.S.D.<5%, n=6), and low detection limits (0.3μgL−1 for both analytes). Enrichment factors of about 400-fold and 220-fold were achieved for MAP and AP, respectively, at optimum conditions. The feasibility of the method was demonstrated by analyzing human urine samples.
Keywords: Headspace liquid-phase microextraction; Aqueous drop; Methamphetamine; Amphetamine; Urine
Coupling continuous ultrasound-assisted extraction with ultrasonic probe, solid-phase extraction and high-performance liquid chromatography for the determination of sodium Danshensu and four tanshinones in Salvia miltiorrhiza bunge by Qiao Yang; Xiao-ling Zhang; Xi-yin Li; Wei-kun Tang; Jun-xiang Zhang; Cheng-xiang Fang; Cong-yi Zheng (pp. 231-238).
A dynamic continuous ultrasound-assisted extraction with high intensity ultrasonic probe (CUAE-HIUP) combined with solid-phase extraction (SPE) for preconcentration and clean-up of the extract prior to high-performance liquid chromatography (HPLC) determination of the main biological active ingredients, sodium Danshensu and four tanshinones (dihydrotanshione I, tanshinone I, cryptotanshinone and tanshinone IIA) from root of Salvia miltiorrhiza bunge has been developed. An experimental design (Plackett–Burman design, 26×3/16) was used to optimize the CUAE-HIUP procedure and the SPE step. Detection limits of 1.2–4.2×10−6mgmL−1 were achieved with the preconcentration efficiency of more than 10-folds by the SPE procedure. The repeatability and within-laboratory reproducibility of the whole process, expressed as relative standard deviations (RSDs), were 1.5–3.6%, 1.6–3.1%, respectively. As compared with the conventional extraction techniques such as room temperature extraction (24h), Soxhlet (4h) and even microwave-assisted extraction (2min), CUAE-HIUP achieved the highest extraction yield (98.9%) and the least amount (10mL) of solvent compared with the other techniques (16mL) in only 3min. The method was successfully applied to the determination of the five biological active ingredients in root of S. miltiorrhiza bunge and Danshen-containing pharmaceutical formulations.
Keywords: Tanshinone; Salvia miltiorrhiza bunge; High-performance liquid chromatography; Solid-phase extraction; Continuous ultrasound-assisted extraction; Ultrasonic probe
Coupling continuous ultrasound-assisted extraction with ultrasonic probe, solid-phase extraction and high-performance liquid chromatography for the determination of sodium Danshensu and four tanshinones in Salvia miltiorrhiza bunge by Qiao Yang; Xiao-ling Zhang; Xi-yin Li; Wei-kun Tang; Jun-xiang Zhang; Cheng-xiang Fang; Cong-yi Zheng (pp. 231-238).
A dynamic continuous ultrasound-assisted extraction with high intensity ultrasonic probe (CUAE-HIUP) combined with solid-phase extraction (SPE) for preconcentration and clean-up of the extract prior to high-performance liquid chromatography (HPLC) determination of the main biological active ingredients, sodium Danshensu and four tanshinones (dihydrotanshione I, tanshinone I, cryptotanshinone and tanshinone IIA) from root of Salvia miltiorrhiza bunge has been developed. An experimental design (Plackett–Burman design, 26×3/16) was used to optimize the CUAE-HIUP procedure and the SPE step. Detection limits of 1.2–4.2×10−6mgmL−1 were achieved with the preconcentration efficiency of more than 10-folds by the SPE procedure. The repeatability and within-laboratory reproducibility of the whole process, expressed as relative standard deviations (RSDs), were 1.5–3.6%, 1.6–3.1%, respectively. As compared with the conventional extraction techniques such as room temperature extraction (24h), Soxhlet (4h) and even microwave-assisted extraction (2min), CUAE-HIUP achieved the highest extraction yield (98.9%) and the least amount (10mL) of solvent compared with the other techniques (16mL) in only 3min. The method was successfully applied to the determination of the five biological active ingredients in root of S. miltiorrhiza bunge and Danshen-containing pharmaceutical formulations.
Keywords: Tanshinone; Salvia miltiorrhiza bunge; High-performance liquid chromatography; Solid-phase extraction; Continuous ultrasound-assisted extraction; Ultrasonic probe
The determination of organochlorine pesticides based on dynamic microwave-assisted extraction coupled with on-line solid-phase extraction of high-performance liquid chromatography by Ligang Chen; Lan Ding; Haiyan Jin; Daqian Song; Huarong Zhang; Jiantao Li; Kun Zhang; Yutang Wang; Hanqi Zhang (pp. 239-246).
A rapid technique based on dynamic microwave-assisted extraction coupled with on-line solid-phase extraction of high-performance liquid chromatography (DMAE–SPE–HPLC) has been developed. A TM010 microwave resonance cavity built in the laboratory was applied to concentrate the microwave energy. The sample placed in the zone of microwave irradiation was extracted with 95% acetonitrile (ACN) aqueous solution which was driven by a peristaltic pump at a flow rate of 1.0mLmin−1. The extraction can be completed in a recirculating system in 10min. When a number of extraction cycles were completed, the extract (1mL) was diluted on-line with water. Then the extract was loaded into an SPE column where the analytes were retained while the unretained matrix components were washed away. Subsequently, the analytes were automatically transferred from the SPE column to the analytical column and determined by UV detector at 238nm. The technique was used for determination of organochlorine pesticides (OCPs) in grains, including wheat, rice, corn and bean. The limits of detection of OCPs are in the range of 19–37ngg−1. The recoveries obtained by analyzing the four spiked grain samples are in the range of 86–105%, whereas the relative standard deviation (R.S.D.) values are <8.7% ranging from 1.2 to 8.7%. Our method was demonstrated to be fast, accurate, and precise. In addition, only small quantities of solvent and sample were required.
Keywords: Dynamic microwave-assisted extraction; Solid-phase extraction; High-performance liquid chromatography (HPLC); On-line determination; Organochlorine pesticides; Grain
The determination of organochlorine pesticides based on dynamic microwave-assisted extraction coupled with on-line solid-phase extraction of high-performance liquid chromatography by Ligang Chen; Lan Ding; Haiyan Jin; Daqian Song; Huarong Zhang; Jiantao Li; Kun Zhang; Yutang Wang; Hanqi Zhang (pp. 239-246).
A rapid technique based on dynamic microwave-assisted extraction coupled with on-line solid-phase extraction of high-performance liquid chromatography (DMAE–SPE–HPLC) has been developed. A TM010 microwave resonance cavity built in the laboratory was applied to concentrate the microwave energy. The sample placed in the zone of microwave irradiation was extracted with 95% acetonitrile (ACN) aqueous solution which was driven by a peristaltic pump at a flow rate of 1.0mLmin−1. The extraction can be completed in a recirculating system in 10min. When a number of extraction cycles were completed, the extract (1mL) was diluted on-line with water. Then the extract was loaded into an SPE column where the analytes were retained while the unretained matrix components were washed away. Subsequently, the analytes were automatically transferred from the SPE column to the analytical column and determined by UV detector at 238nm. The technique was used for determination of organochlorine pesticides (OCPs) in grains, including wheat, rice, corn and bean. The limits of detection of OCPs are in the range of 19–37ngg−1. The recoveries obtained by analyzing the four spiked grain samples are in the range of 86–105%, whereas the relative standard deviation (R.S.D.) values are <8.7% ranging from 1.2 to 8.7%. Our method was demonstrated to be fast, accurate, and precise. In addition, only small quantities of solvent and sample were required.
Keywords: Dynamic microwave-assisted extraction; Solid-phase extraction; High-performance liquid chromatography (HPLC); On-line determination; Organochlorine pesticides; Grain
Multivariate pattern recognition of petroleum-based accelerants by solid-phase microextraction gas chromatography with flame ionization detection by Eric S. Bodle; James K. Hardy (pp. 247-254).
A novel method has been developed for the extraction, analysis and identification of petroleum-based fuels using solid-phase microextraction with analysis by GC–FID. Multivariate data analysis is employed to simplify these data allowing for more accurate classification. Principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) are explored for their effectiveness in establishing accelerant groupings based on the current and previous ASTM International guidelines. The SIMCA models developed for the previous and current ASTM system were 98.5% and 97.2% accurate in unknown sample class prediction. SPME in conjunction with multivariate data analysis is a new approach in accelerant sampling and classification.
Keywords: Solid-phase microextraction; Accelerant; Gas chromatography–flame ionization detector; Pattern recognition; Principal component analysis; Soft independent modeling of class analogy
Multivariate pattern recognition of petroleum-based accelerants by solid-phase microextraction gas chromatography with flame ionization detection by Eric S. Bodle; James K. Hardy (pp. 247-254).
A novel method has been developed for the extraction, analysis and identification of petroleum-based fuels using solid-phase microextraction with analysis by GC–FID. Multivariate data analysis is employed to simplify these data allowing for more accurate classification. Principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) are explored for their effectiveness in establishing accelerant groupings based on the current and previous ASTM International guidelines. The SIMCA models developed for the previous and current ASTM system were 98.5% and 97.2% accurate in unknown sample class prediction. SPME in conjunction with multivariate data analysis is a new approach in accelerant sampling and classification.
Keywords: Solid-phase microextraction; Accelerant; Gas chromatography–flame ionization detector; Pattern recognition; Principal component analysis; Soft independent modeling of class analogy
Anodic stripping voltammetry of antimony using gold nanoparticle-modified carbon screen-printed electrodes by Olga Domínguez Renedo; M. Julia Arcos Martínez (pp. 255-260).
Carbon screen-printed electrodes (CSPE) modified with gold nanoparticles present an interesting alternative in the determination of antimony using differential pulse anodic stripping voltammetry. Metallic gold nanoparticles deposits have been obtained by direct electrochemical deposition. Scanning electron microscopy measurements show that the electrochemically synthesized gold nanoparticles are deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analyzed to ensure that common interferents in the determination of antimony by ASV. The detection limit for Sb(III) obtained was 9.44×10−10M. In terms of reproducibility, the precision of the above mentioned method in %R.S.D. values was calculated at 2.69% ( n=10). The method was applied to determine levels of antimony in seawater samples and pharmaceutical preparations.
Keywords: Gold nanoparticles; Screen-printed electrodes; Antimony; Anodic stripping voltammetry
Anodic stripping voltammetry of antimony using gold nanoparticle-modified carbon screen-printed electrodes by Olga Domínguez Renedo; M. Julia Arcos Martínez (pp. 255-260).
Carbon screen-printed electrodes (CSPE) modified with gold nanoparticles present an interesting alternative in the determination of antimony using differential pulse anodic stripping voltammetry. Metallic gold nanoparticles deposits have been obtained by direct electrochemical deposition. Scanning electron microscopy measurements show that the electrochemically synthesized gold nanoparticles are deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analyzed to ensure that common interferents in the determination of antimony by ASV. The detection limit for Sb(III) obtained was 9.44×10−10M. In terms of reproducibility, the precision of the above mentioned method in %R.S.D. values was calculated at 2.69% ( n=10). The method was applied to determine levels of antimony in seawater samples and pharmaceutical preparations.
Keywords: Gold nanoparticles; Screen-printed electrodes; Antimony; Anodic stripping voltammetry
Application of permeation liquid membrane and scanned stripping chronopotentiometry to metal speciation analysis of colloidal complexes by Rute F. Domingos; Marc F. Benedetti; J.P. Pinheiro (pp. 261-268).
The potential of permeation liquid membrane (PLM) to obtain dynamic metal speciation information for colloidal complexes is evaluated by measurements of lead(II) and copper(II) complexation by carboxyl modified latex nanospheres of different radii (15, 35, 40 and 65nm). The results are compared with those obtained by a well characterized technique: stripping chronopotentiometry at scanned deposition potential (SSCP). Under the PLM conditions employed, and for large particles or macromolecular ligands, membrane diffusion is the rate-limiting step. That is, the flux is proportional to the free metal ion concentration with only a small contribution from labile complexes. In the absence of ligand aggregation in the PLM channels, good agreement was obtained between the stability constants determined by PLM and SSCP for both metals.
Keywords: Colloidal dispersions; Dynamic speciation; Lability; Permeable liquid membrane; Stripping chronopotentiometry at scanned deposition potential
Application of permeation liquid membrane and scanned stripping chronopotentiometry to metal speciation analysis of colloidal complexes by Rute F. Domingos; Marc F. Benedetti; J.P. Pinheiro (pp. 261-268).
The potential of permeation liquid membrane (PLM) to obtain dynamic metal speciation information for colloidal complexes is evaluated by measurements of lead(II) and copper(II) complexation by carboxyl modified latex nanospheres of different radii (15, 35, 40 and 65nm). The results are compared with those obtained by a well characterized technique: stripping chronopotentiometry at scanned deposition potential (SSCP). Under the PLM conditions employed, and for large particles or macromolecular ligands, membrane diffusion is the rate-limiting step. That is, the flux is proportional to the free metal ion concentration with only a small contribution from labile complexes. In the absence of ligand aggregation in the PLM channels, good agreement was obtained between the stability constants determined by PLM and SSCP for both metals.
Keywords: Colloidal dispersions; Dynamic speciation; Lability; Permeable liquid membrane; Stripping chronopotentiometry at scanned deposition potential
Excretion profile of boldenone and its metabolites after oral administration to veal calves by G. Ferretti; L. Palleschi; C. Marchiafava; F. delli Quadri; L. Fantozzi; C. Ferranti; P. Cammarata; A. Macrì; C. Montesissa; R. Draisci (pp. 269-274).
The residue profiles of boldenone (17β-Bol), its epimer (17α-Bol) and the related compound androsta-1,4-diene-3,17-dione (ADD), were investigated by liquid chromatography–tandem mass spectrometry (LC–MS/MS) in urine of male calves orally treated with boldenone, boldenone esters, and/or ADD. In all the experiments with the administered steroids residues of 17α-Bol decreased rapidly after end of treatment; detectable amounts of 17α-Bol were however noticed along the withdrawal observation period after end of treatment. Differently, residues of 17β-Bol were detectable only shortly after administration. This in vivo research concerning oral treatments of cattle with boldenone related substances proves ADD to be a very active boldenone precursor in bovine animals.
Keywords: Anabolic hormones; Boldenone; in vivo; Veal calves; Urine; Liquid chromatography–tandem mass spectrometry
Excretion profile of boldenone and its metabolites after oral administration to veal calves by G. Ferretti; L. Palleschi; C. Marchiafava; F. delli Quadri; L. Fantozzi; C. Ferranti; P. Cammarata; A. Macrì; C. Montesissa; R. Draisci (pp. 269-274).
The residue profiles of boldenone (17β-Bol), its epimer (17α-Bol) and the related compound androsta-1,4-diene-3,17-dione (ADD), were investigated by liquid chromatography–tandem mass spectrometry (LC–MS/MS) in urine of male calves orally treated with boldenone, boldenone esters, and/or ADD. In all the experiments with the administered steroids residues of 17α-Bol decreased rapidly after end of treatment; detectable amounts of 17α-Bol were however noticed along the withdrawal observation period after end of treatment. Differently, residues of 17β-Bol were detectable only shortly after administration. This in vivo research concerning oral treatments of cattle with boldenone related substances proves ADD to be a very active boldenone precursor in bovine animals.
Keywords: Anabolic hormones; Boldenone; in vivo; Veal calves; Urine; Liquid chromatography–tandem mass spectrometry