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A potential tool for high-resolution monitoring of ocean acidification
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Aron Hakonen , Leif G. Anderson , Johan Engelbrektsson , Stefan Hulth , Bengt Karlson
Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acidification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and low oceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck for research on ocean acidification is long-term monitoring and the collection of consistent high-resolution pH measurements. This study presents a low-power (<1W) small sample volume (25μL) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatial resolution (approximately 15s and 100m between samples). A 405nm light emitting diode and the blue and green channels from a digital camera was used for swift detection of fluorescence from the pH sensitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated by automated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegat region with a large range in salinity (∼3–30) and temperature (∼0–25°C). Ship-board precision of salinity and temperature adjusted pH measurements were estimated as low as 0.0001 pH units.
Source:Analytica Chimica Acta, Volume 786
Author(s): Aron Hakonen , Leif G. Anderson , Johan Engelbrektsson , Stefan Hulth , Bengt Karlson
Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acidification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and low oceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck for research on ocean acidification is long-term monitoring and the collection of consistent high-resolution pH measurements. This study presents a low-power (<1W) small sample volume (25μL) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatial resolution (approximately 15s and 100m between samples). A 405nm light emitting diode and the blue and green channels from a digital camera was used for swift detection of fluorescence from the pH sensitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated by automated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegat region with a large range in salinity (∼3–30) and temperature (∼0–25°C). Ship-board precision of salinity and temperature adjusted pH measurements were estimated as low as 0.0001 pH units.
Graphical abstract
Liquid phase microextraction strategies combined with total reflection X-ray spectrometry for the determination of low amounts of inorganic antimony species in waters
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Eva Marguí , Marta Sagué , Ignasi Queralt , Manuela Hidalgo
In the present study, and taking into account the microanalytical capability of total reflection X-ray spectrometry (TXRF), we explored the possibilities of hollow fibre liquid-phase microextraction (HF-LPME) and dispersive liquid–liquid microextraction (DLLME) combined with TXRF for the determination of low amounts of inorganic Sb species in waters. For each of the LPME configurations aforementioned, experimental parameters affecting Sb extraction but specially the proper sample preparation process (deposition volume on the reflective carrier and drying mode) and measurement conditions for subsequent TXRF analysis have been carefully evaluated. The best analytical strategy for the determination of Sb(III) and Sb(V) in the low μgL−1 range was found to be the application of the DLLME mode before TXRF analysis. The developed methodology was successfully applied to the determination of inorganic Sb speciation in different types of spiked water samples.
Source:Analytica Chimica Acta, Volume 786
Author(s): Eva Marguí , Marta Sagué , Ignasi Queralt , Manuela Hidalgo
In the present study, and taking into account the microanalytical capability of total reflection X-ray spectrometry (TXRF), we explored the possibilities of hollow fibre liquid-phase microextraction (HF-LPME) and dispersive liquid–liquid microextraction (DLLME) combined with TXRF for the determination of low amounts of inorganic Sb species in waters. For each of the LPME configurations aforementioned, experimental parameters affecting Sb extraction but specially the proper sample preparation process (deposition volume on the reflective carrier and drying mode) and measurement conditions for subsequent TXRF analysis have been carefully evaluated. The best analytical strategy for the determination of Sb(III) and Sb(V) in the low μgL−1 range was found to be the application of the DLLME mode before TXRF analysis. The developed methodology was successfully applied to the determination of inorganic Sb speciation in different types of spiked water samples.
Graphical abstract
Electrochemical sensor based on chlorohemin modified molecularly imprinted microgel for determination of 2,4-dichlorophenol
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Jin Zhang , Jianping Lei , Huangxian Ju , Chaoying Wang
A newly designed molecularly imprinted polymer (MIP) was synthesized and successfully utilized as a recognition element of an amperometric sensor for 2,4-dichlorophenol (2,4-DCP) detection. The MIP with a well-defined structure could imitate the dehalogenative function of the natural enzyme chloroperoxidase for 2,4-DCP. Imprinted sensor was fabricated in situ on a glassy carbon electrode surface by drop-coating the 2,4-DCP imprinted microgel suspension and chitosan/Nafion mixture. Under optimized conditions, the sensor showed a linear response in the range of 5.0–100μmolL−1 with a detection limit of 1.6μmolL−1. Additionally, the imprinted sensor demonstrated higher affinity to target 2,4-DCP over competitive chlorophenolic compounds than non-imprinted sensor. It also exhibited good stability and acceptable repeatability. The proposed sensor could be used for the determination of 2,4-DCP in water samples with the recoveries of 96.2–111.8%, showing a promising potential in practical application.
Source:Analytica Chimica Acta, Volume 786
Author(s): Jin Zhang , Jianping Lei , Huangxian Ju , Chaoying Wang
A newly designed molecularly imprinted polymer (MIP) was synthesized and successfully utilized as a recognition element of an amperometric sensor for 2,4-dichlorophenol (2,4-DCP) detection. The MIP with a well-defined structure could imitate the dehalogenative function of the natural enzyme chloroperoxidase for 2,4-DCP. Imprinted sensor was fabricated in situ on a glassy carbon electrode surface by drop-coating the 2,4-DCP imprinted microgel suspension and chitosan/Nafion mixture. Under optimized conditions, the sensor showed a linear response in the range of 5.0–100μmolL−1 with a detection limit of 1.6μmolL−1. Additionally, the imprinted sensor demonstrated higher affinity to target 2,4-DCP over competitive chlorophenolic compounds than non-imprinted sensor. It also exhibited good stability and acceptable repeatability. The proposed sensor could be used for the determination of 2,4-DCP in water samples with the recoveries of 96.2–111.8%, showing a promising potential in practical application.
Graphical abstract
Determination of aminothiols by liquid chromatography with amperometric detection at a silver electrode: Application to white wines
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Ahmad Sarakbi , Zeynep Aydogmus , Angela Dago , Dominique Mertens , Jean-Yves Dewert , Jean-Michel Kauffmann
Liquid chromatography coupled to a silver electrode based flow-through amperometric detector (LC-EC-Ag) was developed for the determination of aminothiols in white wines. The C18 reversed phase LC system operated in the isocratic mode at 0.7mLmin−1 and used an acidic mobile phase composed of formic acid, EDTA, sodium nitrate, sodium hydroxide, and methanol 1% (v/v) at pH 4.5. The working electrode operated at 0.08V vs Ag/AgCl, 3M KCl and its manual cleaning was realized once a month by smoothing on a polishing cloth. The analyzed aminothiols were resolved and eluted within 4min, and all standard curves were linear in the range 2×10−7–2×10−5 M. The analyzed wine samples needed no preparation other than dilution with the mobile phase. The concentration of cysteine (CYS), homocysteine (HCYS), glutathione (GSH) and N-acetylcysteine (NAC) in bottled white wines, determined by the method of standard addition, was found to be in the low μM range (0.2–2mgL−1) depending on the wine type and its age.
Source:Analytica Chimica Acta, Volume 786
Author(s): Ahmad Sarakbi , Zeynep Aydogmus , Angela Dago , Dominique Mertens , Jean-Yves Dewert , Jean-Michel Kauffmann
Liquid chromatography coupled to a silver electrode based flow-through amperometric detector (LC-EC-Ag) was developed for the determination of aminothiols in white wines. The C18 reversed phase LC system operated in the isocratic mode at 0.7mLmin−1 and used an acidic mobile phase composed of formic acid, EDTA, sodium nitrate, sodium hydroxide, and methanol 1% (v/v) at pH 4.5. The working electrode operated at 0.08V vs Ag/AgCl, 3M KCl and its manual cleaning was realized once a month by smoothing on a polishing cloth. The analyzed aminothiols were resolved and eluted within 4min, and all standard curves were linear in the range 2×10−7–2×10−5 M. The analyzed wine samples needed no preparation other than dilution with the mobile phase. The concentration of cysteine (CYS), homocysteine (HCYS), glutathione (GSH) and N-acetylcysteine (NAC) in bottled white wines, determined by the method of standard addition, was found to be in the low μM range (0.2–2mgL−1) depending on the wine type and its age.
Graphical abstract
Comparative studies on zirconia and graphene composites obtained by one-step and stepwise electrodeposition for deoxyribonucleic acid sensing
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Tao Yang , Xiuhong Guo , Qianqian Kong , Ruirui Yang , Qianhe Li , Kui Jiao
In this paper, the comparison of two kinds of electrochemically reduced graphene oxide (ERGNO) and zirconia composites, obtained by one-step (ZrO2–ERGNO) and stepwise (ZrO2/ERGNO) electrodeposition for DNA sensing, is systematically studied. The resulting composites were characterized by scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. The results indicated that the ZrO2–ERGNO presented fine globular nanostructure. However, ZrO2/ERGNO presented agglomerate massive microstructure due to the absence of the oxygen-containing groups of graphene oxide, confirming the oxygen-containing groups provided a better affinity for the deposition of ZrO2. Due to the strong binding of the phosphate groups of DNA with the zirconia film, DNA probes were attached on the ZrO2-based composites. ZrO2–ERGNO/Au owning fine nanostructure presented larger surface area than microstructured ZrO2/ERGNO/Au. Moreover, compared with microstructured ZrO2/ERGNO, the nanostructured ZrO2–ERGNO provided more accessible space for immobilized DNA probe hybridization with target sequence, which consequently resulted in higher hybridization efficiency. Therefore, the ZrO2–ERGNO was chosen for fabricating DNA sensor with a limit of detection 1.21×10−14 molL−1.
Source:Analytica Chimica Acta, Volume 786
Author(s): Tao Yang , Xiuhong Guo , Qianqian Kong , Ruirui Yang , Qianhe Li , Kui Jiao
In this paper, the comparison of two kinds of electrochemically reduced graphene oxide (ERGNO) and zirconia composites, obtained by one-step (ZrO2–ERGNO) and stepwise (ZrO2/ERGNO) electrodeposition for DNA sensing, is systematically studied. The resulting composites were characterized by scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. The results indicated that the ZrO2–ERGNO presented fine globular nanostructure. However, ZrO2/ERGNO presented agglomerate massive microstructure due to the absence of the oxygen-containing groups of graphene oxide, confirming the oxygen-containing groups provided a better affinity for the deposition of ZrO2. Due to the strong binding of the phosphate groups of DNA with the zirconia film, DNA probes were attached on the ZrO2-based composites. ZrO2–ERGNO/Au owning fine nanostructure presented larger surface area than microstructured ZrO2/ERGNO/Au. Moreover, compared with microstructured ZrO2/ERGNO, the nanostructured ZrO2–ERGNO provided more accessible space for immobilized DNA probe hybridization with target sequence, which consequently resulted in higher hybridization efficiency. Therefore, the ZrO2–ERGNO was chosen for fabricating DNA sensor with a limit of detection 1.21×10−14 molL−1.
Graphical abstract
An ultrasensitive iron(III)-complex based hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Pan Li , Yu Ding , Zhaoyang Lu , Yu Chen , Yiming Zhou , Yawen Tang , Chenxin Cai , Tianhong Lu
In this communication, the first nonelectrocatalysis-type hydrogen peroxide electrochemical sensor is reported. The electroactive iron(III) diethylenetriaminepentaacetic acid (DTPA-FeIII) complex is immobilized on the cysteamine (cys) modified nanoporous gold (NPG) films by covalent method. The immobilized DTPA-FeIII complex quickly communicates an electron with the electrode. Upon addition of hydrogen peroxide, however, hydrogen peroxide inhibits the direct electron transfer of the DTPA-FeIII complex due to the generation of nonelectroactive DTPA-FeIII–H2O2 complex. Based on quenching mechanism, the first hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism is developed. The novel hydrogen peroxide electrochemical sensor has the ultralow detection limit (1.0×10–14 M) and wide linear range (1.0×10–13 to 1.0×10–8 M) with excellent reproducibility and stability.
Source:Analytica Chimica Acta, Volume 786
Author(s): Pan Li , Yu Ding , Zhaoyang Lu , Yu Chen , Yiming Zhou , Yawen Tang , Chenxin Cai , Tianhong Lu
In this communication, the first nonelectrocatalysis-type hydrogen peroxide electrochemical sensor is reported. The electroactive iron(III) diethylenetriaminepentaacetic acid (DTPA-FeIII) complex is immobilized on the cysteamine (cys) modified nanoporous gold (NPG) films by covalent method. The immobilized DTPA-FeIII complex quickly communicates an electron with the electrode. Upon addition of hydrogen peroxide, however, hydrogen peroxide inhibits the direct electron transfer of the DTPA-FeIII complex due to the generation of nonelectroactive DTPA-FeIII–H2O2 complex. Based on quenching mechanism, the first hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism is developed. The novel hydrogen peroxide electrochemical sensor has the ultralow detection limit (1.0×10–14 M) and wide linear range (1.0×10–13 to 1.0×10–8 M) with excellent reproducibility and stability.
Graphical abstract
Application of hot platinum microelectrodes for determination of flavonoids in flow injection analysis and capillary electrophoresis
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Jolanta Magnuszewska , Tadeusz Krogulec
The determination of quercetin and rutin by flow injection analysis (FIA) and capillary electrophoresis (CE) using electrochemical detection was described. These flavonoids were determined at normal (unheated) and hot platinum microelectrodes using cyclic voltammetry. When quercetin or rutin is reaching the platinum electrode, a change of the current in the region of the platinum oxide formation is observed. Integration of the current changes in this in this region creates analytical signals in the form of peaks. An increase of temperature to about 76̊C in a small zone adjacent to the microelectrode causes an increase of the analytical signal by more than 6 times under FIA conditions. This method enables the use of hot microelectrodes as detectors in HPLC or CE. In CE the improvement of the analytical signal at hot microelectrodes is smaller than in FIA and increase only 1.3–3.4 times. Heated microelectrodes were used for analysis of the flavonoids in natural samples of the plant (extract of sea buckthorn) and a pharmaceutical preparation (Cerutin).
Source:Analytica Chimica Acta, Volume 786
Author(s): Jolanta Magnuszewska , Tadeusz Krogulec
The determination of quercetin and rutin by flow injection analysis (FIA) and capillary electrophoresis (CE) using electrochemical detection was described. These flavonoids were determined at normal (unheated) and hot platinum microelectrodes using cyclic voltammetry. When quercetin or rutin is reaching the platinum electrode, a change of the current in the region of the platinum oxide formation is observed. Integration of the current changes in this in this region creates analytical signals in the form of peaks. An increase of temperature to about 76̊C in a small zone adjacent to the microelectrode causes an increase of the analytical signal by more than 6 times under FIA conditions. This method enables the use of hot microelectrodes as detectors in HPLC or CE. In CE the improvement of the analytical signal at hot microelectrodes is smaller than in FIA and increase only 1.3–3.4 times. Heated microelectrodes were used for analysis of the flavonoids in natural samples of the plant (extract of sea buckthorn) and a pharmaceutical preparation (Cerutin).
Graphical abstract
Microwave-assisted extraction combined with gel permeation chromatography and silica gel cleanup followed by gas chromatography–mass spectrometry for the determination of organophosphorus flame retardants and plasticizers in biological samples
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Yongqing Ma , Kunyan Cui , Feng Zeng , Jiaxin Wen , Hong Liu , Fang Zhu , Gangfeng Ouyang , Tiangang Luan , Zunxiang Zeng
An analytical method for the determination of 14 organophosphorus flame retardants (OPFRs), including halogenated OPFRs, non-halogenated OPFRs and triphenyl phosphine oxide (TPPO) in biological samples was developed using gas chromatography–mass spectrometry (GC/MS). Biological samples were extracted using microwave-assisted extraction (MAE) with hexane/acetone (1:1, v/v) as the solvent; then, a two-step clean-up technique, gel permeation chromatography (GPC) combined with solid phase extraction (SPE), was carried out before GC/MS analysis. Experimental results showed that the developed method efficiently removed the lipid compounds and co-extract interferences. Moreover, using the relatively “narrow” column (with an i.d. of 10mm) significantly decreased the elution volume and, therefore, prevented the loss of the most volatile OPFRs, especially trimethyl phosphate (TMP) and triethyl phosphate (TEP). The method detection limits (MDLs) for OPFRs in the biological samples ranged from 0.006 to 0.021ngg−1 lw, and the recoveries were in the range of 70.3–111%, except for TMP (38.9–55.6%), with relative standard deviations (RSDs) of less than 14.1%. The developed method was applied to determine the amount of the target OPFRs in biological samples (i.e., fish and domestic birds) that were collected from the Pearl River Delta (PRD) region in southern China. Of the 14 OPFRs, tri-n-butyl phosphate (TnBP), tris(2-chloroethyl) phosphate (TCEP), tris(chloropropyl) phosphate (TCPP) and tributoxyethyl phosphate (TBEP) were present in all of the biological samples that were analyzed, and dominated by TnBP, TCEP and TBEP. The concentrations of OPFRs in the biological samples that were collected from the PRD region were higher than those reported in other locations.
Source:Analytica Chimica Acta, Volume 786
Author(s): Yongqing Ma , Kunyan Cui , Feng Zeng , Jiaxin Wen , Hong Liu , Fang Zhu , Gangfeng Ouyang , Tiangang Luan , Zunxiang Zeng
An analytical method for the determination of 14 organophosphorus flame retardants (OPFRs), including halogenated OPFRs, non-halogenated OPFRs and triphenyl phosphine oxide (TPPO) in biological samples was developed using gas chromatography–mass spectrometry (GC/MS). Biological samples were extracted using microwave-assisted extraction (MAE) with hexane/acetone (1:1, v/v) as the solvent; then, a two-step clean-up technique, gel permeation chromatography (GPC) combined with solid phase extraction (SPE), was carried out before GC/MS analysis. Experimental results showed that the developed method efficiently removed the lipid compounds and co-extract interferences. Moreover, using the relatively “narrow” column (with an i.d. of 10mm) significantly decreased the elution volume and, therefore, prevented the loss of the most volatile OPFRs, especially trimethyl phosphate (TMP) and triethyl phosphate (TEP). The method detection limits (MDLs) for OPFRs in the biological samples ranged from 0.006 to 0.021ngg−1 lw, and the recoveries were in the range of 70.3–111%, except for TMP (38.9–55.6%), with relative standard deviations (RSDs) of less than 14.1%. The developed method was applied to determine the amount of the target OPFRs in biological samples (i.e., fish and domestic birds) that were collected from the Pearl River Delta (PRD) region in southern China. Of the 14 OPFRs, tri-n-butyl phosphate (TnBP), tris(2-chloroethyl) phosphate (TCEP), tris(chloropropyl) phosphate (TCPP) and tributoxyethyl phosphate (TBEP) were present in all of the biological samples that were analyzed, and dominated by TnBP, TCEP and TBEP. The concentrations of OPFRs in the biological samples that were collected from the PRD region were higher than those reported in other locations.
Graphical abstract
Analysis of heterocyclic amines in hair by on-line in-tube solid-phase microextraction coupled with liquid chromatography−tandem mass spectrometry
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Hiroyuki Kataoka , Tsutomu Inoue , Keita Saito , Hisato Kato , Kazufumi Masuda
Mutagenic and carcinogenic heterocyclic amines (HCAs) are formed during heating of various proteinaceous foods, but human exposure to HCAs has not yet been elucidated in detail. To assess long-term exposure to HCAs, we developed a simple and sensitive method for measuring HCAs in hair by automated on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). Using a Zorbax Eclipse XDB-C8 column, 16 HCAs were analyzed within 15min. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40μL sample at a flow rate of 200μLmin−1 using a Supel-Q PLOT capillary column as an extraction device. The extracted HCAs were easily desorbed from the column by passage of the mobile phase, with no carryover observed. This in-tube SPME LC–MS/MS method showed good linearity for HCAs in the range of 10–2000pgmL−1, with correlation coefficients above 0.9989 (n =18), using stable isotope-labeled HCA internal standards. The detection limits (S/N=3) of 14 HCAs except for MeAαC and Glu-P-1 were 0.10–0.79pgmL−1. This method was successfully utilized to analyze 14 HCAs in hair samples without any interference peaks, with quantitative limits (S/N=10) of about 0.17–1.32pgmg−1 hair. Using this method, we evaluated the exposure to HCAs in cigarette smoke and the suitability of using hair HCAs as exposure biomarkers.
Source:Analytica Chimica Acta, Volume 786
Author(s): Hiroyuki Kataoka , Tsutomu Inoue , Keita Saito , Hisato Kato , Kazufumi Masuda
Mutagenic and carcinogenic heterocyclic amines (HCAs) are formed during heating of various proteinaceous foods, but human exposure to HCAs has not yet been elucidated in detail. To assess long-term exposure to HCAs, we developed a simple and sensitive method for measuring HCAs in hair by automated on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). Using a Zorbax Eclipse XDB-C8 column, 16 HCAs were analyzed within 15min. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40μL sample at a flow rate of 200μLmin−1 using a Supel-Q PLOT capillary column as an extraction device. The extracted HCAs were easily desorbed from the column by passage of the mobile phase, with no carryover observed. This in-tube SPME LC–MS/MS method showed good linearity for HCAs in the range of 10–2000pgmL−1, with correlation coefficients above 0.9989 (n =18), using stable isotope-labeled HCA internal standards. The detection limits (S/N=3) of 14 HCAs except for MeAαC and Glu-P-1 were 0.10–0.79pgmL−1. This method was successfully utilized to analyze 14 HCAs in hair samples without any interference peaks, with quantitative limits (S/N=10) of about 0.17–1.32pgmg−1 hair. Using this method, we evaluated the exposure to HCAs in cigarette smoke and the suitability of using hair HCAs as exposure biomarkers.
Graphical abstract
Evaluation and optimization of solid adsorbents for the sampling of gaseous methylated mercury species
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Pascale A. Baya , Jenny Leigh Hollinsworth , Holger Hintelmann
This study evaluates the suitability of commercially available adsorbents for the measurement of gaseous organic mercury species namely monomethylmercury (MMHg) and dimethylmercury (DMHg). Bond Elut ENV (BE), a new generation of divinylbenzene (DVB), is evaluated the first time for simultaneous sampling and quantification of ultra-trace levels of MMHg and DMHg in air and its performance compared against Carbotrap® B (CB) and Tenax® TA (TA), two commonly used adsorbents for mercury solid phase adsorption. The suitability of TA as an absorbent for MMHg (recovery 100±8.1%) but less so for DMHg (recovery 64±17.3%) was confirmed while the reverse was observed for CB with an average recovery of 100±0.3% for DMHg but only 61±32.5% for MMHg. BE is the only adsorbent that showed excellent performance for trapping both Hg species with recoveries of 98±9.2% and 95±8.1% for MMHg and DMHg, respectively. Furthermore, BE exhibited much higher sampling capacities (>100L at 4°C) and preservation of sample integrity (>1 month at −20°C in the dark). Overall, BE proves to be the most suitable adsorbent for simultaneous trapping of organic Hg species with high sampling capacity and sample stability but also very good chromatographic properties which are desirable characteristics for both collection traps and analytical traps. Bond Elut ENV is proposed as an alternative to both Tenax® TA and Carbotrap® B with additional advantages of offering more versatility and sampling options.
Source:Analytica Chimica Acta, Volume 786
Author(s): Pascale A. Baya , Jenny Leigh Hollinsworth , Holger Hintelmann
This study evaluates the suitability of commercially available adsorbents for the measurement of gaseous organic mercury species namely monomethylmercury (MMHg) and dimethylmercury (DMHg). Bond Elut ENV (BE), a new generation of divinylbenzene (DVB), is evaluated the first time for simultaneous sampling and quantification of ultra-trace levels of MMHg and DMHg in air and its performance compared against Carbotrap® B (CB) and Tenax® TA (TA), two commonly used adsorbents for mercury solid phase adsorption. The suitability of TA as an absorbent for MMHg (recovery 100±8.1%) but less so for DMHg (recovery 64±17.3%) was confirmed while the reverse was observed for CB with an average recovery of 100±0.3% for DMHg but only 61±32.5% for MMHg. BE is the only adsorbent that showed excellent performance for trapping both Hg species with recoveries of 98±9.2% and 95±8.1% for MMHg and DMHg, respectively. Furthermore, BE exhibited much higher sampling capacities (>100L at 4°C) and preservation of sample integrity (>1 month at −20°C in the dark). Overall, BE proves to be the most suitable adsorbent for simultaneous trapping of organic Hg species with high sampling capacity and sample stability but also very good chromatographic properties which are desirable characteristics for both collection traps and analytical traps. Bond Elut ENV is proposed as an alternative to both Tenax® TA and Carbotrap® B with additional advantages of offering more versatility and sampling options.
Graphical abstract
Determination of acetaldehyde in saliva by gas-diffusion flow injection analysis
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Adlin N. Ramdzan , Patrick J. Mornane , Michael J. McCullough , Waldemar Mazurek , Spas D. Kolev
The consumption of ethanol is known to increase the likelihood of oral cancer. In addition, there has been a growing concern about possible association between long term use of ethanol-containing mouthwashes and oral cancer. Acetaldehyde, known to be a carcinogen, is the first metabolite of ethanol and it can be produced in the oral cavity after consumption or exposure to ethanol. This paper reports on the development of a gas-diffusion flow injection method for the online determination of salivary acetaldehyde by its colour reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH) and ferric chloride. Acetaldehyde samples and standards (80μL) were injected into the donor stream containing NaCl from which acetaldehyde diffused through the hydrophobic Teflon membrane of the gas-diffusion cell into the acceptor stream containing the two reagents mentioned above. The resultant intense green coloured dye was monitored spectrophotometrically at 600nm. Under the optimum working conditions the method is characterized by a sampling rate of 9h−1, a linear calibration range of 0.5–15mgL−1 (absorbance=5.40×10−2 [acetaldehyde, mgL−1], R 2 =0.998), a relative standard deviation (RSD) of 1.90% (n =10, acetaldehyde concentration of 2.5mgL−1), and a limit of detection (LOD) of 12.3μgL−1. The LOD and sampling rate of the proposed method are superior to those of the conventional gas chromatographic (GC) method (LOD=93.0μgL−1 and sampling rate=4h−1). The reliability of the proposed method was illustrated by the fact that spiked with acetaldehyde saliva samples yielded excellent recoveries (96.6–101.9%), comparable to those obtained by GC (96.4–102.3%) and there was no statistically significant difference at the 95% confidence level between the two methods when non-spiked saliva samples were analysed.
Source:Analytica Chimica Acta, Volume 786
Author(s): Adlin N. Ramdzan , Patrick J. Mornane , Michael J. McCullough , Waldemar Mazurek , Spas D. Kolev
The consumption of ethanol is known to increase the likelihood of oral cancer. In addition, there has been a growing concern about possible association between long term use of ethanol-containing mouthwashes and oral cancer. Acetaldehyde, known to be a carcinogen, is the first metabolite of ethanol and it can be produced in the oral cavity after consumption or exposure to ethanol. This paper reports on the development of a gas-diffusion flow injection method for the online determination of salivary acetaldehyde by its colour reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH) and ferric chloride. Acetaldehyde samples and standards (80μL) were injected into the donor stream containing NaCl from which acetaldehyde diffused through the hydrophobic Teflon membrane of the gas-diffusion cell into the acceptor stream containing the two reagents mentioned above. The resultant intense green coloured dye was monitored spectrophotometrically at 600nm. Under the optimum working conditions the method is characterized by a sampling rate of 9h−1, a linear calibration range of 0.5–15mgL−1 (absorbance=5.40×10−2 [acetaldehyde, mgL−1], R 2 =0.998), a relative standard deviation (RSD) of 1.90% (n =10, acetaldehyde concentration of 2.5mgL−1), and a limit of detection (LOD) of 12.3μgL−1. The LOD and sampling rate of the proposed method are superior to those of the conventional gas chromatographic (GC) method (LOD=93.0μgL−1 and sampling rate=4h−1). The reliability of the proposed method was illustrated by the fact that spiked with acetaldehyde saliva samples yielded excellent recoveries (96.6–101.9%), comparable to those obtained by GC (96.4–102.3%) and there was no statistically significant difference at the 95% confidence level between the two methods when non-spiked saliva samples were analysed.
Graphical abstract
Sequential injection immunoassay for human bone morphogenic protein-7 using an immunoreactor immobilized with anti-human bone morphogenic protein-7 antibody–CdSe/ZnS quantum dot conjugates
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Chun-Kwang Kim , Hong Dinh Duong , Jong Il Rhee
The detection of human bone morphogenic protein-7 (BMP-7) was achieved using a sequential injection immunoassay (SIIA) system. The SIIA system is based on the binding between BMP-7 and anti-human BMP-7 (AbBMP7)–CdSe/ZnS quantum dot (QD) conjugates immobilized onto a glass disk or an optical fiber, using fluorescence detection at excitation and emission wavelengths of 470nm and 580nm, respectively. The AbBMP7–QD conjugates were prepared by conjugating anti-human BMP-7 antibody (AbBMP7) to hydrophilic CdSe/ZnS core/shell quantum dots (QDs). The SIIA system was fully automated using software written in the LabVIEW™ development environment. The analytical performance of the SIIA system was characterized with a number of variables such as carrier flow rate and elution buffer. Under partially optimized operating conditions, the SIIA system had a linear calibration graph at up to 10.0ngmL−1 BMP-7 (R 2 ≥0.975) and a sample frequency of two samples per hour. The SIIA system with an optical fiber immunosensor was used to detect and quantify BMP-7 in spiked real samples obtained from a biological process with recoveries in the range of 95–102%.
Source:Analytica Chimica Acta, Volume 786
Author(s): Chun-Kwang Kim , Hong Dinh Duong , Jong Il Rhee
The detection of human bone morphogenic protein-7 (BMP-7) was achieved using a sequential injection immunoassay (SIIA) system. The SIIA system is based on the binding between BMP-7 and anti-human BMP-7 (AbBMP7)–CdSe/ZnS quantum dot (QD) conjugates immobilized onto a glass disk or an optical fiber, using fluorescence detection at excitation and emission wavelengths of 470nm and 580nm, respectively. The AbBMP7–QD conjugates were prepared by conjugating anti-human BMP-7 antibody (AbBMP7) to hydrophilic CdSe/ZnS core/shell quantum dots (QDs). The SIIA system was fully automated using software written in the LabVIEW™ development environment. The analytical performance of the SIIA system was characterized with a number of variables such as carrier flow rate and elution buffer. Under partially optimized operating conditions, the SIIA system had a linear calibration graph at up to 10.0ngmL−1 BMP-7 (R 2 ≥0.975) and a sample frequency of two samples per hour. The SIIA system with an optical fiber immunosensor was used to detect and quantify BMP-7 in spiked real samples obtained from a biological process with recoveries in the range of 95–102%.
Graphical abstract
Compressed matrix thin film (CMTF)-assisted laser desorption ionization mass spectrometric analysis
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Lulu Huang , Xiao Xiao , Yinping Xie , Hubert Kageruka , Youe Zhou , Fengjiao Deng , Hongying Zhong
The inhomogeneous re-crystallization process of matrix materials is the major concerns associated with matrix assisted laser desorption/ionization (MALDI) analysis. We describe here the approach termed compressed matrix thin film (CMTF) in order to make a uniform matrix deposition. In this approach, solid matrix particles are compressed under 10MPa of pressure by a compressor that is regularly used in infrared spectroscopic analysis. Then aqueous samples can be deposited on the surface of the matrix film. Major advantages of the CMTF approach are summarized as follows. (1) Reproducible sample preparation procedure. Size and thickness of matrix thin films can be controlled by using a fixed mold.force and known amount of matrix materials. (2) Significantly decreased shot-to-shot variations and enhanced reproducibility. (3) Tolerance for in situ salt washing. Because matrix materials are hydrophobic, salts can be washed away while proteins or peptides are retained on the surface of matrix thin films through hydrophobic interactions. (4) Improved sensitivity. The hydrophobic coating of MALDI sample plate by matrix thin films prevents the spreading of samples across the plate and confines analytes to a small area, leading to increased local concentration. (5) A new means for tissue analysis. Tissue sections can be directly transferred to the uniform surface of matrix materials for reproducible and quantitative comparison of different molecules in different localization. The proposed CMTF should be an enabling technique for mass spectrometric analysis with improved correlations between signal intensities and sample quantities.
Source:Analytica Chimica Acta, Volume 786
Author(s): Lulu Huang , Xiao Xiao , Yinping Xie , Hubert Kageruka , Youe Zhou , Fengjiao Deng , Hongying Zhong
The inhomogeneous re-crystallization process of matrix materials is the major concerns associated with matrix assisted laser desorption/ionization (MALDI) analysis. We describe here the approach termed compressed matrix thin film (CMTF) in order to make a uniform matrix deposition. In this approach, solid matrix particles are compressed under 10MPa of pressure by a compressor that is regularly used in infrared spectroscopic analysis. Then aqueous samples can be deposited on the surface of the matrix film. Major advantages of the CMTF approach are summarized as follows. (1) Reproducible sample preparation procedure. Size and thickness of matrix thin films can be controlled by using a fixed mold.force and known amount of matrix materials. (2) Significantly decreased shot-to-shot variations and enhanced reproducibility. (3) Tolerance for in situ salt washing. Because matrix materials are hydrophobic, salts can be washed away while proteins or peptides are retained on the surface of matrix thin films through hydrophobic interactions. (4) Improved sensitivity. The hydrophobic coating of MALDI sample plate by matrix thin films prevents the spreading of samples across the plate and confines analytes to a small area, leading to increased local concentration. (5) A new means for tissue analysis. Tissue sections can be directly transferred to the uniform surface of matrix materials for reproducible and quantitative comparison of different molecules in different localization. The proposed CMTF should be an enabling technique for mass spectrometric analysis with improved correlations between signal intensities and sample quantities.
Graphical abstract
Compound-specific stable carbon isotope ratios of phenols and nitrophenols derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Satoshi Irei , Jochen Rudolph , Lin Huang
We developed an analytical method for measuring compound-specific stable carbon isotope ratios (δ13C) of phenols and nitrophenols in filter samples of particulate organic matter. The method was tested on 13 phenols derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), together with four nonphenolic compounds. The data obtained by our method required two specific corrections for the determination of valid δ13C values: (1) for nitro compounds, the routine correction with use of m/z 46 for the contribution of 12C17O16O molecules) to m/z 45 was modified due to impact of NO2 on the m/z 46 trace, and (2) for the derivatized phenols, measured δ13C values were corrected for the shift in δ13C due to the addition of carbon atoms from the BSTFA moiety. Analysis of standard-spiked filters showed that overall there was a small compound-dependent bias in the δ13C values: the average bias±the standard error of the mean of −0.21±0.1‰ for the standard compounds tested, except 3-methylcatechol, methylhydroquinone, 4-methyl-2-nitrophenol, and 2,6-dimethyl-4-nitrophenol, whereas the average biases±the standard errors of the mean for those were +1.2±0.3‰, +1.2±0.2‰, −1.2±0.2‰, and −1.4±0.5‰, respectively, when the injected mass of a derivatized compound exceeded 15ngC. In situations where such small biases and uncertainties are acceptable, the method described here could be used to obtain valuable information about δ13C values. We also analyzed a real filter sample to demonstrate the practical applicability of the method.
Source:Analytica Chimica Acta, Volume 786
Author(s): Satoshi Irei , Jochen Rudolph , Lin Huang
We developed an analytical method for measuring compound-specific stable carbon isotope ratios (δ13C) of phenols and nitrophenols in filter samples of particulate organic matter. The method was tested on 13 phenols derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), together with four nonphenolic compounds. The data obtained by our method required two specific corrections for the determination of valid δ13C values: (1) for nitro compounds, the routine correction with use of m/z 46 for the contribution of 12C17O16O molecules) to m/z 45 was modified due to impact of NO2 on the m/z 46 trace, and (2) for the derivatized phenols, measured δ13C values were corrected for the shift in δ13C due to the addition of carbon atoms from the BSTFA moiety. Analysis of standard-spiked filters showed that overall there was a small compound-dependent bias in the δ13C values: the average bias±the standard error of the mean of −0.21±0.1‰ for the standard compounds tested, except 3-methylcatechol, methylhydroquinone, 4-methyl-2-nitrophenol, and 2,6-dimethyl-4-nitrophenol, whereas the average biases±the standard errors of the mean for those were +1.2±0.3‰, +1.2±0.2‰, −1.2±0.2‰, and −1.4±0.5‰, respectively, when the injected mass of a derivatized compound exceeded 15ngC. In situations where such small biases and uncertainties are acceptable, the method described here could be used to obtain valuable information about δ13C values. We also analyzed a real filter sample to demonstrate the practical applicability of the method.
Graphical abstract
A matrix-assisted laser desorption/ionization tandem mass spectrometry method for direct screening of small molecule mixtures against an aminoglycoside kinase
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Anne Marie E. Smith , Emelia Awuah , Alfredo Capretta , John D. Brennan
Aminoglycoside phosphotransferase 3′IIIa (APH3′IIIa) is a bacterial enzyme involved in antibiotic resistance through phosphorylation of aminoglycosides, which can potentially be overcome by co-administration of an APH3′IIIa inhibitor with the antibiotic. Current assay methods for discovery of APH3′IIIa inhibitors suffer from low specificity and high false positive/negative hit rates. Here, we describe a method for screening APH3′IIIa inhibitors based on direct detection of kanamycin A phosphorylation using MALDI-MS/MS, which is more rapid than conventional assays and does not require secondary assays or sample cleanup. The MALDI-MS/MS assay operates at an ionic strength of 45mM and co-factors can be utilized at near-physiological levels for optimal enzyme activity. Detection via MALDI-MS/MS allowed for improved reproducibility when compared to ESI-MS/MS. Furthermore, the use of MS/MS provided better signal-to-noise ratios relative to MS alone on the MALDI instrument. The assay was validated via generation of Z′-factors, with values of 0.78 and 0.56 in the absence and presence of 0.2% DMSO, respectively. The assay was used to screen a kinase directed library of >200 compounds, assayed as 21 mixtures of 10 compounds each. Five novel synthetic inhibitors were identified following mixture deconvolution. Inhibition constants were obtained for the aforementioned inhibitors using the MALDI-MS/MS assay, revealing several low to mid micromolar “hits”, and highlighting the quantitative nature of the assay.
Source:Analytica Chimica Acta, Volume 786
Author(s): Anne Marie E. Smith , Emelia Awuah , Alfredo Capretta , John D. Brennan
Aminoglycoside phosphotransferase 3′IIIa (APH3′IIIa) is a bacterial enzyme involved in antibiotic resistance through phosphorylation of aminoglycosides, which can potentially be overcome by co-administration of an APH3′IIIa inhibitor with the antibiotic. Current assay methods for discovery of APH3′IIIa inhibitors suffer from low specificity and high false positive/negative hit rates. Here, we describe a method for screening APH3′IIIa inhibitors based on direct detection of kanamycin A phosphorylation using MALDI-MS/MS, which is more rapid than conventional assays and does not require secondary assays or sample cleanup. The MALDI-MS/MS assay operates at an ionic strength of 45mM and co-factors can be utilized at near-physiological levels for optimal enzyme activity. Detection via MALDI-MS/MS allowed for improved reproducibility when compared to ESI-MS/MS. Furthermore, the use of MS/MS provided better signal-to-noise ratios relative to MS alone on the MALDI instrument. The assay was validated via generation of Z′-factors, with values of 0.78 and 0.56 in the absence and presence of 0.2% DMSO, respectively. The assay was used to screen a kinase directed library of >200 compounds, assayed as 21 mixtures of 10 compounds each. Five novel synthetic inhibitors were identified following mixture deconvolution. Inhibition constants were obtained for the aforementioned inhibitors using the MALDI-MS/MS assay, revealing several low to mid micromolar “hits”, and highlighting the quantitative nature of the assay.
Graphical abstract
Fluorescence detection of glutathione reductase activity based on deoxyribonucleic acid-templated silver nanoclusters
25 June 2013,
05:34:56
Publication date: 5 July
2013
Source:Analytica Chimica Acta, Volume 786
Author(s): Shuyun Zhu , Xian-en Zhao , Wei Zhang , Zhongyuan Liu , Wenjing Qi , Saima Anjum , Guobao Xu
Fluorescent silver nanoclusters stabilized by DNA (DNA-AgNCs) exhibit distinct response rates to thiol and disulfide. Glutathione reductase can catalyze the reduction of the oxidized glutathione (GSSG) quickly to reduced glutathione (GSH) in the presence of β-nicotinamide adenine dinucleotide 2′-phosphate reduced tetrasodium salt hydrate (NADPH). Consequently, DNA-AgNCs can serve as a new fluorescent platform for assaying the glutathione reductase (GR) activity. This newly proposed assay has a high sensitivity and a good selectivity toward GR. The GR activity can be detected in the range of 0.2–2.0mUmL−1 with a minimum detectable concentration of 0.2mUmL−1. Pepsin, lysozyme, trypsin, avidin, thrombin, myoglobin, and BSA have little effect on the fluorescence intensity of DNA-AgNCs. The GR activity assay is successfully used to monitor the inhibition of GR activity by a typical inhibitor 1,3-bis(2-chloroethyl)-1-nitrosourea.
Source:Analytica Chimica Acta, Volume 786
Author(s): Shuyun Zhu , Xian-en Zhao , Wei Zhang , Zhongyuan Liu , Wenjing Qi , Saima Anjum , Guobao Xu
Fluorescent silver nanoclusters stabilized by DNA (DNA-AgNCs) exhibit distinct response rates to thiol and disulfide. Glutathione reductase can catalyze the reduction of the oxidized glutathione (GSSG) quickly to reduced glutathione (GSH) in the presence of β-nicotinamide adenine dinucleotide 2′-phosphate reduced tetrasodium salt hydrate (NADPH). Consequently, DNA-AgNCs can serve as a new fluorescent platform for assaying the glutathione reductase (GR) activity. This newly proposed assay has a high sensitivity and a good selectivity toward GR. The GR activity can be detected in the range of 0.2–2.0mUmL−1 with a minimum detectable concentration of 0.2mUmL−1. Pepsin, lysozyme, trypsin, avidin, thrombin, myoglobin, and BSA have little effect on the fluorescence intensity of DNA-AgNCs. The GR activity assay is successfully used to monitor the inhibition of GR activity by a typical inhibitor 1,3-bis(2-chloroethyl)-1-nitrosourea.
Graphical abstract
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