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Disposable screen-printed sensors modified with bismuth precursor compounds for the rapid voltammetric screening of trace Pb(II) and Cd(II)
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Nikolitsa Lezi, Anastasios Economou, Panagiotis A. Dimovasilis, Pantelis N. Trikalitis, Mamas I. Prodromidis
In this article, a study of novel screen-printed electrodes bulk-modified with five potential bismuth precursor compounds (bismuth citrate, bismuth titanate, bismuth oxide, bismuth aluminate and bismuth zirconate) is presented for the determination of Cd(II) and Pb(II) by anodic stripping voltammetry. During the electrolytic deposition step, the precursor was reduced and served as the source of bismuth. Different key parameters were investigated in detail such as the nature of the bismuth precursor compound, the precursor content in the carbon ink, the polarisation range of the sensors, the supporting electrolyte, the stripping waveform, the deposition time, the deposition potential and the long-term stability of the sensors under continuous use. Using bismuth citrate as the precursor, the limit of detection was 0.9μgL−1 for Pb(II) and 1.1μgL−1 for Cd(II). The reproducibility on the same sensor (expressed as % relative standard deviation, (n =8)) was 5.4% for Pb(II) and 7.2% for Cd(II) at the 20μgL−1 level. Finally, the sensors were applied to the determination of Cd(II) and Pb(II) in water samples.
Source:Analytica Chimica Acta, Volume 728
Nikolitsa Lezi, Anastasios Economou, Panagiotis A. Dimovasilis, Pantelis N. Trikalitis, Mamas I. Prodromidis
In this article, a study of novel screen-printed electrodes bulk-modified with five potential bismuth precursor compounds (bismuth citrate, bismuth titanate, bismuth oxide, bismuth aluminate and bismuth zirconate) is presented for the determination of Cd(II) and Pb(II) by anodic stripping voltammetry. During the electrolytic deposition step, the precursor was reduced and served as the source of bismuth. Different key parameters were investigated in detail such as the nature of the bismuth precursor compound, the precursor content in the carbon ink, the polarisation range of the sensors, the supporting electrolyte, the stripping waveform, the deposition time, the deposition potential and the long-term stability of the sensors under continuous use. Using bismuth citrate as the precursor, the limit of detection was 0.9μgL−1 for Pb(II) and 1.1μgL−1 for Cd(II). The reproducibility on the same sensor (expressed as % relative standard deviation, (n =8)) was 5.4% for Pb(II) and 7.2% for Cd(II) at the 20μgL−1 level. Finally, the sensors were applied to the determination of Cd(II) and Pb(II) in water samples.
Graphical Abstract
Graphical abstract Highlights
. ► Novel screen-printed sensors loaded with bismuth precursors have been fabricated. ► These are used for the rapid screening of Pb(II), Cd(II) by stripping voltammetry. ► During the accumulation step, the Bi(III) precursors are reduced to metallic bismuth. ► Bismuth citrate at a 6% (w/w) offered the highest sensitivity and reproducibility.A binderless, covalently bulk modified electrochemical sensor: Application to simultaneous determination of lead and cadmium at trace level
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Raghu Gunigollahalli Kempegowda, Pandurangappa Malingappa
A new type of covalent binderless bulk modified electrode has been fabricated and used in the simultaneous determination of lead and cadmium ions at nanomolar level. The modification of graphitic carbon with 4-amino salicylic acid was carried out under microwave irradiation through the amide bond formation. The electrochemical behavior of the fabricated electrode has been carried out to decipher the interacting ability of the functional moieties present on the modifier molecules toward the simultaneous determination of Pb2+ and Cd2+ ions using cyclic and differential pulse anodic stripping voltammetry. The possible mode of interaction of functional groups with metal ions is proposed based on the pKa values of the modifier functionalities present on the surface of graphitic carbon particles. The analytical utility of the proposed sensor has been validated by measuring the lead and cadmium content from pretreated waste water samples of lead acid batteries.
Source:Analytica Chimica Acta, Volume 728
Raghu Gunigollahalli Kempegowda, Pandurangappa Malingappa
A new type of covalent binderless bulk modified electrode has been fabricated and used in the simultaneous determination of lead and cadmium ions at nanomolar level. The modification of graphitic carbon with 4-amino salicylic acid was carried out under microwave irradiation through the amide bond formation. The electrochemical behavior of the fabricated electrode has been carried out to decipher the interacting ability of the functional moieties present on the modifier molecules toward the simultaneous determination of Pb2+ and Cd2+ ions using cyclic and differential pulse anodic stripping voltammetry. The possible mode of interaction of functional groups with metal ions is proposed based on the pKa values of the modifier functionalities present on the surface of graphitic carbon particles. The analytical utility of the proposed sensor has been validated by measuring the lead and cadmium content from pretreated waste water samples of lead acid batteries.
Graphical Abstract
Graphical abstract Highlights
► Proposed sensor is a new type of binderless covalent bulk modified electrode. ► Surface can be easily renewed by simple mechanical polishing using emery sheets. ► Free from modifier leaching during electrochemical measurements. ► Provides long term storage stability with good reproducibility. ► Nanomolar level detection limit achieved with selectivity.Poly(o-phenylenediamine)-carried nanogold particles as signal tags for sensitive electrochemical immunoassay of prolactin
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Huafeng Chen, Yuling Cui, Bing Zhang, Bingqian Liu, Guonan Chen, Dianping Tang
A novel class of redox-active molecular tags, poly(o-phenylenediamine)-carried nanogold particles (GPPDs), was first synthesized and functionalized with horseradish peroxidase-anti-prolactin conjugates (HRP-anti-PRL). Thereafter, a specific sandwich-type electrochemical immunoassay was designed for determination of prolactin (PRL) by using GPPD-labeled HRP-anti-PRL conjugates as molecular tags on anti-PRL antibody-modified glassy carbon electrode. Compared with pure gold nanoparticles and poly(o-phenylenediamine) microspheres, the as-prepared GPPDs increased the surface coverage of the nanostructures, and enhanced the immobilization amount of biomolecules. Several labeling protocols compromising GPPD-labeled HRP-anti-PRL, nanogold particles-labeled HRP-anti-PRL and poly(o-phenylenediamine) microspheres-labeled HRP-anti-PRL, were investigated for detection of PRL, and improved analytical features were obtained with the GPPD-based strategy. With the GPPD labeling method, dependence of the electrochemical signals on the incubation time and pH of the assay solution were also studied. The strong attachment of HRP-anti-PRL to the GPPDs resulted in a good repeatability and intermediate reproducibility down to 9.8%. The dynamic concentration range spanned from 0.5 to 180ngmL−1 PRL with a detection limit of 0.1ngmL−1 at the 3S blank level. No significant differences at the 95% confidence level were encountered in the analysis of 10 spiked blank cattle serum samples between the developed immunoassay and enzyme-linked immunosorbent assay method for determination of PRL.
Source:Analytica Chimica Acta, Volume 728
Huafeng Chen, Yuling Cui, Bing Zhang, Bingqian Liu, Guonan Chen, Dianping Tang
A novel class of redox-active molecular tags, poly(o-phenylenediamine)-carried nanogold particles (GPPDs), was first synthesized and functionalized with horseradish peroxidase-anti-prolactin conjugates (HRP-anti-PRL). Thereafter, a specific sandwich-type electrochemical immunoassay was designed for determination of prolactin (PRL) by using GPPD-labeled HRP-anti-PRL conjugates as molecular tags on anti-PRL antibody-modified glassy carbon electrode. Compared with pure gold nanoparticles and poly(o-phenylenediamine) microspheres, the as-prepared GPPDs increased the surface coverage of the nanostructures, and enhanced the immobilization amount of biomolecules. Several labeling protocols compromising GPPD-labeled HRP-anti-PRL, nanogold particles-labeled HRP-anti-PRL and poly(o-phenylenediamine) microspheres-labeled HRP-anti-PRL, were investigated for detection of PRL, and improved analytical features were obtained with the GPPD-based strategy. With the GPPD labeling method, dependence of the electrochemical signals on the incubation time and pH of the assay solution were also studied. The strong attachment of HRP-anti-PRL to the GPPDs resulted in a good repeatability and intermediate reproducibility down to 9.8%. The dynamic concentration range spanned from 0.5 to 180ngmL−1 PRL with a detection limit of 0.1ngmL−1 at the 3S blank level. No significant differences at the 95% confidence level were encountered in the analysis of 10 spiked blank cattle serum samples between the developed immunoassay and enzyme-linked immunosorbent assay method for determination of PRL.
Graphical Abstract
Graphical abstract Highlights
► This work designs a sensitive and feasible sandwich-type electrochemical immunoassay system for determination of prolactin. ► A novel class of redox-active molecular tags, poly(o-phenylenediamine)-carried nanogold particles. ► A lower detection limit of the electrochemical immunosensor than that of commercially available ELISAs.High-throughput quantification of palladium in water samples by ion pair based-surfactant assisted microextraction
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Yadollah Yamini, Morteza Moradi, Elham Tahmasebi
A novel method for the determination of palladium as a metal ion model was developed by ion pair based surfactant-assisted microextraction (IP-SAME) and inductively coupled plasma-optical detection (ICP-OES). In this methodology, a cationic surfactant was used in extraction process. It has two fundamental functions: (1) the formation of an emulsified phase and (2) the ion pair formation with Pd(II) in the presence of iodide ions and making Pd I 4 2 − extractable into organic phase (active microextraction). The effective parameters on the extraction recovery such as the types of extraction solvent and the surfactant, surfactant concentration, KI amount and HCl concentration of the sample were investigated and optimized. In the proposed approach, tetradecyl trimethyl ammonium bromide (TTAB) was used as emulsifier and ion pairing agent, and 1-octanol was selected as extraction solvent. Under the optimum conditions, the enhancement factor as large as 146 was obtained. The detection limit for palladium was 0.2μgL−1, and the relative standard deviation (RSD) was 4.1% (n =5, C =10.0μgL−1). The proposed method was applied for extraction and determination of palladium in different water samples.
Source:Analytica Chimica Acta, Volume 728
Yadollah Yamini, Morteza Moradi, Elham Tahmasebi
A novel method for the determination of palladium as a metal ion model was developed by ion pair based surfactant-assisted microextraction (IP-SAME) and inductively coupled plasma-optical detection (ICP-OES). In this methodology, a cationic surfactant was used in extraction process. It has two fundamental functions: (1) the formation of an emulsified phase and (2) the ion pair formation with Pd(II) in the presence of iodide ions and making Pd I 4 2 − extractable into organic phase (active microextraction). The effective parameters on the extraction recovery such as the types of extraction solvent and the surfactant, surfactant concentration, KI amount and HCl concentration of the sample were investigated and optimized. In the proposed approach, tetradecyl trimethyl ammonium bromide (TTAB) was used as emulsifier and ion pairing agent, and 1-octanol was selected as extraction solvent. Under the optimum conditions, the enhancement factor as large as 146 was obtained. The detection limit for palladium was 0.2μgL−1, and the relative standard deviation (RSD) was 4.1% (n =5, C =10.0μgL−1). The proposed method was applied for extraction and determination of palladium in different water samples.
Graphical Abstract
Graphical abstract Highlights
► A method named ion pair based surfactant assisted microextraction was developed. ► The method was applied for extraction of Pd(II) in presence of cationic surfactants. ► The extracted Pd(II) was determined by ICP-OES. ► Theoretical aspects of ion pair based surfactant assisted extraction was discussed.Air-assisted liquid–liquid microextraction method as a novel microextraction technique; Application in extraction and preconcentration of phthalate esters in aqueous sample followed by gas chromatography–flame ionization detection
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Mir Ali Farajzadeh, Mohammad Reza Afshar Mogaddam
A novel microextraction technique, air-assisted liquid–liquid microextraction (AALLME), which is a new version of dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction and preconcentration of phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DNBP), and di-2-ethylhexyl phthalate (DEHP), from aqueous samples prior to gas chromatography–flame ionization detection (GC–FID) analysis. In this method, much less volume of an organic solvent is used as extraction solvent in the absence of a disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GC–FID. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12–1.15 and 0.85–4ngmL−1, respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 889–1022 and 89–102%, respectively. The relative standard deviations (RSDs) for the extraction of 100ngmL−1 and 500ngmL−1 of each phthalate ester were less than 4% for intra-day (n =6) and inter-days (n =4) precision. Finally some aqueous samples were successfully analyzed using the proposed method and three analytes, DIBP, DNBP and DEHP, were determined in them at ngmL−1 level.
Source:Analytica Chimica Acta, Volume 728
Mir Ali Farajzadeh, Mohammad Reza Afshar Mogaddam
A novel microextraction technique, air-assisted liquid–liquid microextraction (AALLME), which is a new version of dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction and preconcentration of phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DNBP), and di-2-ethylhexyl phthalate (DEHP), from aqueous samples prior to gas chromatography–flame ionization detection (GC–FID) analysis. In this method, much less volume of an organic solvent is used as extraction solvent in the absence of a disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GC–FID. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12–1.15 and 0.85–4ngmL−1, respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 889–1022 and 89–102%, respectively. The relative standard deviations (RSDs) for the extraction of 100ngmL−1 and 500ngmL−1 of each phthalate ester were less than 4% for intra-day (n =6) and inter-days (n =4) precision. Finally some aqueous samples were successfully analyzed using the proposed method and three analytes, DIBP, DNBP and DEHP, were determined in them at ngmL−1 level.
Graphical Abstract
Graphical abstract Highlights
► A simple air-assisted liquid–liquid microextraction (AALLME) method has been developed for the first time. ► Enrichment factors of the proposed method were higher than those of conventional DLLME. ► The new method avoided using disperser solvent. ► Short extraction time of the present method relative to the other methods was another advantage of this method.Development of a dedicated peptide tandem mass spectral library for conservation science
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Wim Fremout, Maarten Dhaenens, Steven Saverwyns, Jana Sanyova, Peter Vandenabeele, Dieter Deforce, Luc Moens
In recent years, the use of liquid chromatography tandem mass spectrometry (LC–MS/MS) on tryptic digests of cultural heritage objects has attracted much attention. It allows for unambiguous identification of peptides and proteins, and even in complex mixtures species-specific identification becomes feasible with minimal sample consumption. Determination of the peptides is commonly based on theoretical cleavage of known protein sequences and on comparison of the expected peptide fragments with those found in the MS/MS spectra. In this approach, complex computer programs, such as Mascot, perform well identifying known proteins, but fail when protein sequences are unknown or incomplete. Often, when trying to distinguish evolutionarily well preserved collagens of different species, Mascot lacks the required specificity. Complementary and often more accurate information on the proteins can be obtained using a reference library of MS/MS spectra of species-specific peptides. Therefore, a library dedicated to various sources of proteins in works of art was set up, with an initial focus on collagen rich materials. This paper discusses the construction and the advantages of this spectral library for conservation science, and its application on a number of samples from historical works of art.
Source:Analytica Chimica Acta, Volume 728
Wim Fremout, Maarten Dhaenens, Steven Saverwyns, Jana Sanyova, Peter Vandenabeele, Dieter Deforce, Luc Moens
In recent years, the use of liquid chromatography tandem mass spectrometry (LC–MS/MS) on tryptic digests of cultural heritage objects has attracted much attention. It allows for unambiguous identification of peptides and proteins, and even in complex mixtures species-specific identification becomes feasible with minimal sample consumption. Determination of the peptides is commonly based on theoretical cleavage of known protein sequences and on comparison of the expected peptide fragments with those found in the MS/MS spectra. In this approach, complex computer programs, such as Mascot, perform well identifying known proteins, but fail when protein sequences are unknown or incomplete. Often, when trying to distinguish evolutionarily well preserved collagens of different species, Mascot lacks the required specificity. Complementary and often more accurate information on the proteins can be obtained using a reference library of MS/MS spectra of species-specific peptides. Therefore, a library dedicated to various sources of proteins in works of art was set up, with an initial focus on collagen rich materials. This paper discusses the construction and the advantages of this spectral library for conservation science, and its application on a number of samples from historical works of art.
Graphical Abstract
Graphical abstract Highlights
► Sequence library search is not working for species determination of animal glues. ► Spectral library matching is proposed as an alternative approach. ► A dedicated spectral library for conservation science is developed. ► This methodology was successfully applied on paint samples.A comparative study of glycoprotein concentration, glycoform profile and glycosylation site occupancy using isotope labeling and electrospray linear ion trap mass spectrometry
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Chih-Yu Lin, Yi-Chun Ma, Pei-Jing Pai, Guor-Rong Her
A strategy is presented for comparative analysis of glycoproteins in which the variation of protein concentration, variation of glycosylation site occupancy and variation of glycoform profile can be determined. A comparative study was performed using stable isotope labeling of glycopeptides and peptides by formaldehyde-H2 and formaldehyde-D2 and analysis by ESI-MS analysis. The relative intensity of the nonglycosylated peptide provided information about protein concentration variation. Variation of the glycoform profile was obtained by comparing the glycoform profile of d0- and d4-dimethyl labeled glycopeptides. By knowing the variation of protein concentration and the variation of glycoform profile, the variation of glycosylation site occupancy could be calculated. The utility of the proposed strategy was demonstrated with ribonuclease B with different protein concentrations, different levels of glycosylation site occupancy and different glycoform profiles.
Source:Analytica Chimica Acta, Volume 728
Chih-Yu Lin, Yi-Chun Ma, Pei-Jing Pai, Guor-Rong Her
A strategy is presented for comparative analysis of glycoproteins in which the variation of protein concentration, variation of glycosylation site occupancy and variation of glycoform profile can be determined. A comparative study was performed using stable isotope labeling of glycopeptides and peptides by formaldehyde-H2 and formaldehyde-D2 and analysis by ESI-MS analysis. The relative intensity of the nonglycosylated peptide provided information about protein concentration variation. Variation of the glycoform profile was obtained by comparing the glycoform profile of d0- and d4-dimethyl labeled glycopeptides. By knowing the variation of protein concentration and the variation of glycoform profile, the variation of glycosylation site occupancy could be calculated. The utility of the proposed strategy was demonstrated with ribonuclease B with different protein concentrations, different levels of glycosylation site occupancy and different glycoform profiles.
Graphical Abstract
Graphical abstract Highlights
► Concentration, site occupancy and glycoform variation can be differentiated. ► Glycopeptides and peptides were stable isotope labeled and analyzed by ESI-MS. ► Nonglycosylated peptide provided glycoprotein concentration variation. ► Glycoform variation was obtained by comparing d0 and d4 labeled glycopeptides. ► The variation of glycosylation site occupancy could be calculated.An infrared spectroscopic based method for mercury(II) detection in aqueous solutions
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Asela Chandrasoma, Amer Al Abdel Hamid, Alice E. Bruce, Mitchell R.M. Bruce, Carl. P. Tripp
A new method that uses solid phase extraction (SPE) coupled with FTIR spectroscopy to detect Hg(II) in aqueous samples is described. The technique is envisioned for on-site, field evaluation rather than lab-based techniques. This paper presents the “proof of principle” of this new approach toward measurements of Hg(II) in water and identifies mass transport issues that would need to be overcome in order to migrate from a lab based method to field operation. The SPE material supported on a Si wafer is derivatized with an acylthiosemicarbazide, which undergoes a reaction in the presence of aqueous Hg(II) to form an oxadiazole ring. The progress of the reaction is monitored by IR spectroscopy. Following EPA guidelines, the method of detection limit (MDL) for the SPE/IR was 5μg of Hg(II)cm−2. In a 1L sample and a 1cm2 Si wafer, this translates to a detection limit of 5ppb. This system shows a high selectivity toward aqueous Hg(II) over other thiophilic heavy metal ions such as Pb(II), Cd(II), Fe(III), and Zn(II) and other metal ions such as Ni(II), Mn(II), Co(II), Cu(II), In(III), Ru(III), Na(I), and Ag(I) in aqueous solutions.
Source:Analytica Chimica Acta, Volume 728
Asela Chandrasoma, Amer Al Abdel Hamid, Alice E. Bruce, Mitchell R.M. Bruce, Carl. P. Tripp
A new method that uses solid phase extraction (SPE) coupled with FTIR spectroscopy to detect Hg(II) in aqueous samples is described. The technique is envisioned for on-site, field evaluation rather than lab-based techniques. This paper presents the “proof of principle” of this new approach toward measurements of Hg(II) in water and identifies mass transport issues that would need to be overcome in order to migrate from a lab based method to field operation. The SPE material supported on a Si wafer is derivatized with an acylthiosemicarbazide, which undergoes a reaction in the presence of aqueous Hg(II) to form an oxadiazole ring. The progress of the reaction is monitored by IR spectroscopy. Following EPA guidelines, the method of detection limit (MDL) for the SPE/IR was 5μg of Hg(II)cm−2. In a 1L sample and a 1cm2 Si wafer, this translates to a detection limit of 5ppb. This system shows a high selectivity toward aqueous Hg(II) over other thiophilic heavy metal ions such as Pb(II), Cd(II), Fe(III), and Zn(II) and other metal ions such as Ni(II), Mn(II), Co(II), Cu(II), In(III), Ru(III), Na(I), and Ag(I) in aqueous solutions.
Graphical Abstract
Graphical abstract Highlights
► Solid phase extraction coupled with FTIR spectroscopy selectively detects Hg(II)(aq). ► The method is selective vs. thiophilic ions such as Pb(II), Cd(II), Fe(III), and Zn(II). ► The method is also selective vs. metals such as Ni(II), Mn(II), Co(II), and Cu(II). ► Method of detection limit (MDL) for the SPE/IR is 5μg of Hg(II)cm−2. ► The study identifies mass transport issues relevant for further development.Label-free detection of C-reactive protein using reflectometric interference spectroscopy-based sensing system
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Hyung Woo Choi, Yasuhiko Sakata, Yoshikazu Kurihara, Tooru Ooya, Toshifumi Takeuchi
Reflectometric interference spectroscopy (RIfS) is a label-free, time-resolved technique, and suitable for detecting antibody–antigen interaction. This work describes a continuous flow biosensor for C-reactive protein (CRP), involving an effective immobilization method of a monoclonal antibody against CRP (anti-CRP) to achieve highly sensitive RIfS-based detection of CRP. The silicon nitride-coated silicon chip (SiN chip) for the RIfS sensing was first treated with trimethylsilylchloride (TMS), followed by UV-light irradiation to in situ generation of homogeneous silanols on the surface. Following amination by 3-aminopropyltriethoxysilane, carboxymethyldextran (CMD) was grafted, and subsequently, protein A was immobilized to create the oriented anti-CRP surface. The immobilization process of protein A and anti-CRP was monitored with the RIfS system by consecutive injections of an amine coupling reagent, protein A and anti-CRP, respectively, to confirm the progress of each step in real time. The sensitivity was enhanced when all of the processes were adopted, suggesting that the oriented immobilization of anti-CRP via protein A that was coupled with the grafted CMD on the aminated surface of TMS-treated SiN chip. The feasibility of the present sensing system was demonstrated on the detection of CRP, where the silicon-based inexpensive chips and the simple optical setup were employed. It can be applied to other target molecules in various fields of life science as a substitute of surface plasmon resonance-based expensive sensors.
Source:Analytica Chimica Acta, Volume 728
Hyung Woo Choi, Yasuhiko Sakata, Yoshikazu Kurihara, Tooru Ooya, Toshifumi Takeuchi
Reflectometric interference spectroscopy (RIfS) is a label-free, time-resolved technique, and suitable for detecting antibody–antigen interaction. This work describes a continuous flow biosensor for C-reactive protein (CRP), involving an effective immobilization method of a monoclonal antibody against CRP (anti-CRP) to achieve highly sensitive RIfS-based detection of CRP. The silicon nitride-coated silicon chip (SiN chip) for the RIfS sensing was first treated with trimethylsilylchloride (TMS), followed by UV-light irradiation to in situ generation of homogeneous silanols on the surface. Following amination by 3-aminopropyltriethoxysilane, carboxymethyldextran (CMD) was grafted, and subsequently, protein A was immobilized to create the oriented anti-CRP surface. The immobilization process of protein A and anti-CRP was monitored with the RIfS system by consecutive injections of an amine coupling reagent, protein A and anti-CRP, respectively, to confirm the progress of each step in real time. The sensitivity was enhanced when all of the processes were adopted, suggesting that the oriented immobilization of anti-CRP via protein A that was coupled with the grafted CMD on the aminated surface of TMS-treated SiN chip. The feasibility of the present sensing system was demonstrated on the detection of CRP, where the silicon-based inexpensive chips and the simple optical setup were employed. It can be applied to other target molecules in various fields of life science as a substitute of surface plasmon resonance-based expensive sensors.
Graphical Abstract
Graphical abstract Highlights
► A new RIfS-based label-free biosensing system for C-reactive protein was developed. ► Silicon-based inexpensive chips and the simple optical setup were employed. ► Owing to the TMS treatment and the use of protein A, the sensitivity was enhanced. ► It can be applied to other target as a substitute of SPR-based expensive sensors.Comparative study of different alcohol sensors based on Screen-Printed Carbon Electrodes
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Estefanía Costa Rama, Julien Biscay, María Begoña González García, A. Julio Reviejo, José Manuel Pingarrón Carrazón, Agustín Costa García
Different very simple single-use alcohol enzyme sensors were developed using alcohol oxidase (AOX) from three different yeast, Hansenula sp., Pichia pastoris and Candida boidinii, and employing three different commercial mediator-based Screen-Printed Carbon Electrodes as transducers. The mediators tested, Prussian Blue, Ferrocyanide and Co-phthalocyanine were included into the ink of the working electrode. The procedure to obtain these sensors consists of the immobilization of the enzyme on the electrode surface by adsorption. For the immobilization, an AOX solution is deposited on the working electrode and left until dried (1h) at room temperature. The best results were obtained with the biosensor using Screen-Printed Co-phthalocyanine/Carbon Electrode and AOX from Hansenula sp. The reduced cobalt–phthalocyanine form is amperometrically detected at +0.4V (vs. Ag pseudo reference electrode). This sensor shows good sensitivity (1211nAmM−1), high precision (2.1% RSD value for the slope value of the calibration plot) and wide linear response (0.05–1.00mM) for ethanol determination. The sensor provides also accurate results for ethanol quantification in alcoholic drinks.
Source:Analytica Chimica Acta, Volume 728
Estefanía Costa Rama, Julien Biscay, María Begoña González García, A. Julio Reviejo, José Manuel Pingarrón Carrazón, Agustín Costa García
Different very simple single-use alcohol enzyme sensors were developed using alcohol oxidase (AOX) from three different yeast, Hansenula sp., Pichia pastoris and Candida boidinii, and employing three different commercial mediator-based Screen-Printed Carbon Electrodes as transducers. The mediators tested, Prussian Blue, Ferrocyanide and Co-phthalocyanine were included into the ink of the working electrode. The procedure to obtain these sensors consists of the immobilization of the enzyme on the electrode surface by adsorption. For the immobilization, an AOX solution is deposited on the working electrode and left until dried (1h) at room temperature. The best results were obtained with the biosensor using Screen-Printed Co-phthalocyanine/Carbon Electrode and AOX from Hansenula sp. The reduced cobalt–phthalocyanine form is amperometrically detected at +0.4V (vs. Ag pseudo reference electrode). This sensor shows good sensitivity (1211nAmM−1), high precision (2.1% RSD value for the slope value of the calibration plot) and wide linear response (0.05–1.00mM) for ethanol determination. The sensor provides also accurate results for ethanol quantification in alcoholic drinks.
Graphical Abstract
Graphical abstract Highlights
► We developed three alcohol sensors using screen-printed carbon/mediator electrodes. ► Better results were obtained with screen-printed carbon/Co-phthalocyanine electrodes. ► The sensor is fabricated in a simple way resulting in good sensitivity and stability. ► Results obtained in real samples have good accuracy and precision comparing with GC.A ratiometric fluorescence sensor for Be2+ based on Beryllon II/layered double hydroxide ultrathin films
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Xiaolan Ji, Wenying Shi, Shitong Zhang, Min Wei, David G. Evans, Xue Duan
A ratiometric fluorescence sensor for Be2+ has been fabricated via alternate assembly of 2-(3,6-disulfo-8-hydroxynaphthylazo)-1,8-dihydroxynaphthalene-3,6-disulfonate (Beryllon II) and MgAl-LDH nanosheets on quartz substrates using the layer-by-layer (LBL) deposition technique. UV–vis absorption and the fluorescence emission spectroscopy indicate a stepwise and regular growth of the Beryllon II/LDH UTFs upon increasing deposition cycle. The film of Beryllon II/LDH possesses a periodic layered structure perpendicular to the substrate revealed by X-ray diffraction and scanning electron microscopy. Atomic force microscopy images show that the film surface is continuous and uniform. The Beryllon II/LDH UTFs display ratiometric fluorescence response for Be2+ with a linear response range in 1.0×10−7–1.9×10−6 molL−1 and a detection limit of 4.2×10−9 molL−1. Furthermore, the ratiometric sensor exhibits good repeatability, high stability (thermal, storage and mechanical) as well as excellent selectivity toward Be2+. XPS and Raman measurements demonstrate that the specific response of the sensor is attributed to the coordination between Be2+ and Beryllon II in the UTF. The Beryllon II/LDH UTFs in this work can be potentially used as a chemosensor for the detection of Be2+ in the environmental and biomedical field.
Source:Analytica Chimica Acta, Volume 728
Xiaolan Ji, Wenying Shi, Shitong Zhang, Min Wei, David G. Evans, Xue Duan
A ratiometric fluorescence sensor for Be2+ has been fabricated via alternate assembly of 2-(3,6-disulfo-8-hydroxynaphthylazo)-1,8-dihydroxynaphthalene-3,6-disulfonate (Beryllon II) and MgAl-LDH nanosheets on quartz substrates using the layer-by-layer (LBL) deposition technique. UV–vis absorption and the fluorescence emission spectroscopy indicate a stepwise and regular growth of the Beryllon II/LDH UTFs upon increasing deposition cycle. The film of Beryllon II/LDH possesses a periodic layered structure perpendicular to the substrate revealed by X-ray diffraction and scanning electron microscopy. Atomic force microscopy images show that the film surface is continuous and uniform. The Beryllon II/LDH UTFs display ratiometric fluorescence response for Be2+ with a linear response range in 1.0×10−7–1.9×10−6 molL−1 and a detection limit of 4.2×10−9 molL−1. Furthermore, the ratiometric sensor exhibits good repeatability, high stability (thermal, storage and mechanical) as well as excellent selectivity toward Be2+. XPS and Raman measurements demonstrate that the specific response of the sensor is attributed to the coordination between Be2+ and Beryllon II in the UTF. The Beryllon II/LDH UTFs in this work can be potentially used as a chemosensor for the detection of Be2+ in the environmental and biomedical field.
Graphical Abstract
Graphical abstract Highlights
This paper reports the fabrication of Beryllon II/layered double hydroxide ultrathin films via the layer-by-layer assembly technique, which can be used as a ratiometric fluorescence chemosensor for Be2+ with good repeatability, high stability and excellent selectivity. ► A ratiometric fluorescence sensor for Be2+ was fabricated by LBL method. ► The chemosensor shows a broad linear response range and a low detection limit. ► The sensor exhibits a high stability and excellent selectivity toward Be2+. ► The chemosensor can be easily regenerated and reused.Dynamic labeling of diagnostically significant microbial cells in cerebrospinal fluid by red chromophoric non-ionogenic surfactant for capillary electrophoresis separations
08 May 2012,
09:28:44
Publication year:
2012
Source:Analytica Chimica Acta, Volume 728
Marie Horká, Filip Růžička, Anna Kubesová, Karel Šlais
During bacterial infections of the central nervous system the number of microorganisms in the cerebrospinal fluid is often ranging from few up to hundreds of cells per milliliter. The electrophoretic techniques with the UV-detection reach a detection limit for whole cells of approximately 107 cells per milliliter. The coupling of the filtration cartridge with capillary isoelectric focusing can improve the detection limit by four orders of magnitude. In order to improve the detection limit the red non-ionogenic surfactant 1-[[4-(phenylazo)phenyl]azo]-2-hydroxy-3-naphthoic acid polyethylene glycol ester, PAPAN 1000, has been prepared and used for the dynamic labeling of analytes before filtration of the sample with a concentration modulation in the analysis of proteins or microorganisms. Values of isoelectric points of labeled analytes have been calculated using pI markers detectable at 515nm and have been found comparable with pI of the native compounds. Minimum detectable amounts of proteins and microorganisms were lower than nanograms and a hundred labeled cells, respectively. The introduced method, coupling of the filtration cerebrospinal fluid spiked with microorganisms and labeled by PAPAN, facilitates their rapid CIEF separation in the pH gradient pH range of 2–5 at their clinically important level 101 to 102 cells per milliliter.
Source:Analytica Chimica Acta, Volume 728
Marie Horká, Filip Růžička, Anna Kubesová, Karel Šlais
During bacterial infections of the central nervous system the number of microorganisms in the cerebrospinal fluid is often ranging from few up to hundreds of cells per milliliter. The electrophoretic techniques with the UV-detection reach a detection limit for whole cells of approximately 107 cells per milliliter. The coupling of the filtration cartridge with capillary isoelectric focusing can improve the detection limit by four orders of magnitude. In order to improve the detection limit the red non-ionogenic surfactant 1-[[4-(phenylazo)phenyl]azo]-2-hydroxy-3-naphthoic acid polyethylene glycol ester, PAPAN 1000, has been prepared and used for the dynamic labeling of analytes before filtration of the sample with a concentration modulation in the analysis of proteins or microorganisms. Values of isoelectric points of labeled analytes have been calculated using pI markers detectable at 515nm and have been found comparable with pI of the native compounds. Minimum detectable amounts of proteins and microorganisms were lower than nanograms and a hundred labeled cells, respectively. The introduced method, coupling of the filtration cerebrospinal fluid spiked with microorganisms and labeled by PAPAN, facilitates their rapid CIEF separation in the pH gradient pH range of 2–5 at their clinically important level 101 to 102 cells per milliliter.
Graphical Abstract
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