Selected
papers from the latest issue:
Determination and speciation of mercury in environmental and biological samples by analytical atomic spectrometry
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Ying Gao, Zeming Shi, Zhou Long, Peng Wu, Chengbin Zheng, Xiandeng Hou
Mercury and its compounds are ubiquitous in the environment. Much concern has been attracted to the determination of mercury and its species due to their high toxicity and biomagnification. The state of the arts of mercury determination and speciation analysis and its applications in environmental and biological sciences since 2008 are reviewed with 133 references. The methodological innovations in sample preparation, preconcentration, instrumentation and speciation analysis are summarized, and the future perspectives are briefly discussed and speculated.
Source:Microchemical Journal, Volume 103
Ying Gao, Zeming Shi, Zhou Long, Peng Wu, Chengbin Zheng, Xiandeng Hou
Mercury and its compounds are ubiquitous in the environment. Much concern has been attracted to the determination of mercury and its species due to their high toxicity and biomagnification. The state of the arts of mercury determination and speciation analysis and its applications in environmental and biological sciences since 2008 are reviewed with 133 references. The methodological innovations in sample preparation, preconcentration, instrumentation and speciation analysis are summarized, and the future perspectives are briefly discussed and speculated.
Use of passive biomonitoring to evaluate the environmental impact of emissions from cement industries in Sergipe State, northeast Brazil
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Angélica B. Ferreira, José O. Santos, Sidnei O. Souza, Wilson N.S. Júnior, José do Patrocínio H. Alves
Measurements of trace elements in tree bark were used to investigate pollution caused by emissions from two cement production plants in the vicinity of the cities of Laranjeiras and Nossa Senhora do Socorro (Sergipe State, northeast Brazil). Samples of tree bark were collected across a wide area within the municipalities of Machado, Estivas, and Estivas II, as well as close to the two cement plants. Analyses were carried out by EDXRF to determine the concentrations of Al, Ca, Cu, Fe, K, Mg, S, Sr, and Zn in the tree barks. The resulting data were used to generate distribution maps of element concentrations, which enabled identification of pollution hotspots. The results indicated that emissions from the cement industry affect the region as a whole, as demonstrated by accumulation of trace elements in the tree barks.
Source:Microchemical Journal, Volume 103
Angélica B. Ferreira, José O. Santos, Sidnei O. Souza, Wilson N.S. Júnior, José do Patrocínio H. Alves
Measurements of trace elements in tree bark were used to investigate pollution caused by emissions from two cement production plants in the vicinity of the cities of Laranjeiras and Nossa Senhora do Socorro (Sergipe State, northeast Brazil). Samples of tree bark were collected across a wide area within the municipalities of Machado, Estivas, and Estivas II, as well as close to the two cement plants. Analyses were carried out by EDXRF to determine the concentrations of Al, Ca, Cu, Fe, K, Mg, S, Sr, and Zn in the tree barks. The resulting data were used to generate distribution maps of element concentrations, which enabled identification of pollution hotspots. The results indicated that emissions from the cement industry affect the region as a whole, as demonstrated by accumulation of trace elements in the tree barks.
Development of carboxylic acid search prefilters for spectral library matching
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Kadambari Nuguru, Nikhil Mirjankar, Jerome Workman
435 infrared (IR) absorbance spectra of 140 carboxylic acids and 295 noncarboxylic acids which included aldehydes, ketones, esters, amides as well as compounds containing both carbonyls and alcohols were preprocessed using the wavelet packet tree to enhance subtle but important features in the data. Wavelet coefficients that optimized the separation of the spectra by functional group in a plot of the two largest principal components of the data were identified using a genetic algorithm (GA) for pattern recognition analysis. Because principal components maximize variance, the bulk of the information encoded by the wavelet coefficients selected by the pattern recognition GA is characteristic of the carboxylic acid functional group. The carboxylic acid search prefilter developed as part of this study was successfully validated using two external validation sets. The first validation set consisted of 24 carboxylic acids and 61 noncarboxylic acids and the second validation set consisted of 264 carboxylic acids and 72 noncarboxylic acids.
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Kadambari Nuguru, Nikhil Mirjankar, Jerome Workman
435 infrared (IR) absorbance spectra of 140 carboxylic acids and 295 noncarboxylic acids which included aldehydes, ketones, esters, amides as well as compounds containing both carbonyls and alcohols were preprocessed using the wavelet packet tree to enhance subtle but important features in the data. Wavelet coefficients that optimized the separation of the spectra by functional group in a plot of the two largest principal components of the data were identified using a genetic algorithm (GA) for pattern recognition analysis. Because principal components maximize variance, the bulk of the information encoded by the wavelet coefficients selected by the pattern recognition GA is characteristic of the carboxylic acid functional group. The carboxylic acid search prefilter developed as part of this study was successfully validated using two external validation sets. The first validation set consisted of 24 carboxylic acids and 61 noncarboxylic acids and the second validation set consisted of 264 carboxylic acids and 72 noncarboxylic acids.
Prediction of mold contamination from microbial volatile organic compound profiles using solid phase microextraction and gas chromatography/mass spectrometry
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Nikhil Mirjankar, Ryan LeBouf, Alan Rossner
An integrated chemical and microbiological approach was used to develop a new sampling and analytical methodology to characterize the fungal load of a contaminated area or building. A set of microbial volatile organic compound (MVOC) profiles were developed with corresponding bioaerosol measurements as input–output pairs for a discriminant to predict the presence or absence of mold contamination in indoor environments. Spore collection to characterize the indoor air quality of the residences and buildings was performed using an Anderson N6 impactor. Simultaneously, solid phase microextraction was used as a passive sampling device to collect VOCs from the air for GC/MS analysis. The volatile organic signatures that molds emit as reflected by the gas chromatographic profiles were compared to the impactor data collected from each sampling site. By comparing the bioaerosol data to the volatile organic profiles, a discriminant could be trained to classify a residence with potential mold growth based on its MVOCs.
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Nikhil Mirjankar, Ryan LeBouf, Alan Rossner
An integrated chemical and microbiological approach was used to develop a new sampling and analytical methodology to characterize the fungal load of a contaminated area or building. A set of microbial volatile organic compound (MVOC) profiles were developed with corresponding bioaerosol measurements as input–output pairs for a discriminant to predict the presence or absence of mold contamination in indoor environments. Spore collection to characterize the indoor air quality of the residences and buildings was performed using an Anderson N6 impactor. Simultaneously, solid phase microextraction was used as a passive sampling device to collect VOCs from the air for GC/MS analysis. The volatile organic signatures that molds emit as reflected by the gas chromatographic profiles were compared to the impactor data collected from each sampling site. By comparing the bioaerosol data to the volatile organic profiles, a discriminant could be trained to classify a residence with potential mold growth based on its MVOCs.
Use of solid phase microextraction (SPME) in the analysis of the reduced sulfur compounds (RSC) and its experimental limitations
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Ehsanul Kabir, Ki-Hyun Kim
In this study, techniques based on solid-phase microextraction (SPME) with gas chromatography (GC)–pulsed flame photometric detection (PFPD) were evaluated for its application toward a list of reduced sulfur compounds (RSCs) such as hydrogen sulfide (H2S), methanethiol (CH3SH), dimethyl sulfide (DMS), carbon disulfide (CS2), and dimethyl disulfide (DMDS). Its performance was tested against direct injection (DI) and thermal desorber (TD) approaches. Although the SPME-based calibration of RSCs showed good linearity (r2 >0.9) like other methods, it was more prone to analytical bias for the lighter molecular weight (MW) RSCs (especially H2S) due to distinctively reduced sensitivity relative to the heavier MW compounds. As such, the detections limits (DL) of SPME vary by more than an order of magnitude for the lighter and heavier MW RSCs (DL=16.9ng for H2S and 1.46ng for DMS). Evidence collected from an extended reproducibility test further supports that the experimental reliability of SPME approach is fairly low, especially with respect to H2S. The quality of SPME-based analysis thus needs more cautious validation in the study of odor and air pollution, as the lighter RSCs like H2S (or CH3SH) are often identified as the key components under various settings.
Source:Microchemical Journal, Volume 103
Ehsanul Kabir, Ki-Hyun Kim
In this study, techniques based on solid-phase microextraction (SPME) with gas chromatography (GC)–pulsed flame photometric detection (PFPD) were evaluated for its application toward a list of reduced sulfur compounds (RSCs) such as hydrogen sulfide (H2S), methanethiol (CH3SH), dimethyl sulfide (DMS), carbon disulfide (CS2), and dimethyl disulfide (DMDS). Its performance was tested against direct injection (DI) and thermal desorber (TD) approaches. Although the SPME-based calibration of RSCs showed good linearity (r2 >0.9) like other methods, it was more prone to analytical bias for the lighter molecular weight (MW) RSCs (especially H2S) due to distinctively reduced sensitivity relative to the heavier MW compounds. As such, the detections limits (DL) of SPME vary by more than an order of magnitude for the lighter and heavier MW RSCs (DL=16.9ng for H2S and 1.46ng for DMS). Evidence collected from an extended reproducibility test further supports that the experimental reliability of SPME approach is fairly low, especially with respect to H2S. The quality of SPME-based analysis thus needs more cautious validation in the study of odor and air pollution, as the lighter RSCs like H2S (or CH3SH) are often identified as the key components under various settings.
Analysis of vanilla extract by reversed phase liquid chromatography using water rich mobile phases
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Desire T. Corona, Undugodage Don Nuwan Tharanga Perera
Vanillin is the major constituent of vanilla extract, a flavoring ingredient used in food and beverages. Natural vanilla extract prepared from the bean of the tropical orchid, Vanilla planifolia, is expensive due to the limited supply of the vanilla bean. For this reason, synthetic vanilla extracts are widely used. Synthetic vanilla extracts are less complex and usually contain vanillin, ethyl vanillin, and other related compounds that are prepared from inexpensive starting materials. Several liquid chromatographic methods have been developed to quantitate coumarin, vanillin, and ethyl vanillin in vanilla extract. The use of water rich mobile phases in reversed phase liquid chromatography (RPLC), e.g., 1% butanol in water with 0.2% acetic acid with C18, C8, and cyanopropyl columns, has been investigated as a potential method to characterize the composition of synthetic vanilla extracts. Better resolution is achieved in the separation of vanillin compounds when hydrophobic alcohols are used as organic modifiers. This can be attributed to butanol partitioning into the bonded phase, which provides a more extended ordered surface increasing the contact surface area of the stationary phase and thereby increasing the selectivity of the separation. Using water rich mobile phases, constituents of vanilla extract in 36 commercial products obtained from stores in the local area were identified demonstrating the efficacy of the proposed RPLC method.
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Desire T. Corona, Undugodage Don Nuwan Tharanga Perera
Vanillin is the major constituent of vanilla extract, a flavoring ingredient used in food and beverages. Natural vanilla extract prepared from the bean of the tropical orchid, Vanilla planifolia, is expensive due to the limited supply of the vanilla bean. For this reason, synthetic vanilla extracts are widely used. Synthetic vanilla extracts are less complex and usually contain vanillin, ethyl vanillin, and other related compounds that are prepared from inexpensive starting materials. Several liquid chromatographic methods have been developed to quantitate coumarin, vanillin, and ethyl vanillin in vanilla extract. The use of water rich mobile phases in reversed phase liquid chromatography (RPLC), e.g., 1% butanol in water with 0.2% acetic acid with C18, C8, and cyanopropyl columns, has been investigated as a potential method to characterize the composition of synthetic vanilla extracts. Better resolution is achieved in the separation of vanillin compounds when hydrophobic alcohols are used as organic modifiers. This can be attributed to butanol partitioning into the bonded phase, which provides a more extended ordered surface increasing the contact surface area of the stationary phase and thereby increasing the selectivity of the separation. Using water rich mobile phases, constituents of vanilla extract in 36 commercial products obtained from stores in the local area were identified demonstrating the efficacy of the proposed RPLC method.
A portable photometer based on LED for the determination of aromatic hydrocarbons in water
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Kássio Michell Gomes de Lima
The present work describes a portable photometer based on light-emitting-diodes (LED) for the determination of total aromatic hydrocarbons in water contaminated with gasoline. Two LED were employed as the light source with maximum emission at 1300nm and 1689nm. The radiation of each LED was collected with bundles of 24 silica optical fibers, which were assembled in a single bundle pointed toward the detection cell. An InGaAs photodiode was directly connected to the measuring cell. Software was written in VisualBasic.NET to control the photometer through a USB interface and for data acquisition. The determination of total aromatic hydrocarbons was performed using a silicone-sensing phase (length of 5mm and diameter of 3.2mm), which was employed to extract these compounds from the contaminated water. The extraction (60min under constant stirring) was performed in a 100-mL flask filled with the water sample diluted in 2.0molL−1 NaCl. A repeatability of 1.8% and 1.3% (expressed as the relative standard deviation of 10 measurements) was obtained at 1300nm and 1689nm, respectively. Absorbance values were calculated considering the signal at 1300nm as reference because hydrocarbons do not absorb at this wavelength. Analytical curves up to 200mgL−1 and 400mgL−1 were constructed for benzene and toluene, providing limits of detection of 1.2mgL−1 and 1.7mgL−1, respectively. The sensitivity was similar to those obtained with a FT-NIR Bomem MB 160 spectrophotometer at the same wavelength. The photometer was applied to the determination of total hydrocarbons in water contaminated by gasoline. An analytical curve (50–300mgL−1) was constructed from reference solutions containing benzene and toluene in the ratio of 3:7, which is a ratio commonly found in Brazilian gasoline. The results provided by the photometer were compared with those obtained with the commercial spectrophotometer and did not show significant differences at a confidence level of 95%.
Source:Microchemical Journal, Volume 103
Kássio Michell Gomes de Lima
The present work describes a portable photometer based on light-emitting-diodes (LED) for the determination of total aromatic hydrocarbons in water contaminated with gasoline. Two LED were employed as the light source with maximum emission at 1300nm and 1689nm. The radiation of each LED was collected with bundles of 24 silica optical fibers, which were assembled in a single bundle pointed toward the detection cell. An InGaAs photodiode was directly connected to the measuring cell. Software was written in VisualBasic.NET to control the photometer through a USB interface and for data acquisition. The determination of total aromatic hydrocarbons was performed using a silicone-sensing phase (length of 5mm and diameter of 3.2mm), which was employed to extract these compounds from the contaminated water. The extraction (60min under constant stirring) was performed in a 100-mL flask filled with the water sample diluted in 2.0molL−1 NaCl. A repeatability of 1.8% and 1.3% (expressed as the relative standard deviation of 10 measurements) was obtained at 1300nm and 1689nm, respectively. Absorbance values were calculated considering the signal at 1300nm as reference because hydrocarbons do not absorb at this wavelength. Analytical curves up to 200mgL−1 and 400mgL−1 were constructed for benzene and toluene, providing limits of detection of 1.2mgL−1 and 1.7mgL−1, respectively. The sensitivity was similar to those obtained with a FT-NIR Bomem MB 160 spectrophotometer at the same wavelength. The photometer was applied to the determination of total hydrocarbons in water contaminated by gasoline. An analytical curve (50–300mgL−1) was constructed from reference solutions containing benzene and toluene in the ratio of 3:7, which is a ratio commonly found in Brazilian gasoline. The results provided by the photometer were compared with those obtained with the commercial spectrophotometer and did not show significant differences at a confidence level of 95%.
Antimony coordination to humic acid: Nuclear magnetic resonance and X-ray absorption fine structure spectroscopy study
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Tserenpil Sh, Cong-Qiang Liu, Lihua Wang
This current study examined the fate of antimony (Sb) in the soil environment and its association with soil humic acid (HA). It is anticipated that a significant proportion of Sb is retained in soil organic layer; therefore, the oxidation state of Sb is controlled by the soil HA to some extent which influences Sb solubility and ecotoxicity. Parent HA material as well as prepared HA–Sb (III) composites was investigated by determining elemental composition and by performing nuclear magnetic resonance (NMR) and X-ray absorption fine structure (XAFS) spectroscopy study in order to study Sb coordination to natural macro organic ligand. The Sb (III) binding to soil derived HA mainly contributed to its open chains through carboxyl and hydroxyl moieties as revealed by the 1H and solid state 13C NMR spectroscopy. The protons in carboxylic and hydroxylic groups (those proton signals are characteristic of HAs with different origins) disappeared in the HA–Sb composite; and relative changes were observed in aliphatic proton distribution between the HA samples with and without Sb. The overall patterns of 13C NMR spectra for the investigated samples were analogous to each other; moreover, it was estimated that the cyclic structure of the HA nucleus remained unchanged during Sb (III) association. Based on the absorption edge energy and coordination numbers, Sb oxidation state in a native soil was interpreted as pentavalent, meanwhile the HA–Sb composite contained both Sb (III) and Sb (V). It was shown that HA catalyzes Sb (III) oxidation to Sb (V) but the process was relatively slow. However, XAFS spectra sensitivity was limited when studying the HA–Sb composite that was prepared from the isolated soil HA fraction, so only data on the first shell Sb–O coordination were interpreted.
Source:Microchemical Journal, Volume 103
Tserenpil Sh, Cong-Qiang Liu, Lihua Wang
This current study examined the fate of antimony (Sb) in the soil environment and its association with soil humic acid (HA). It is anticipated that a significant proportion of Sb is retained in soil organic layer; therefore, the oxidation state of Sb is controlled by the soil HA to some extent which influences Sb solubility and ecotoxicity. Parent HA material as well as prepared HA–Sb (III) composites was investigated by determining elemental composition and by performing nuclear magnetic resonance (NMR) and X-ray absorption fine structure (XAFS) spectroscopy study in order to study Sb coordination to natural macro organic ligand. The Sb (III) binding to soil derived HA mainly contributed to its open chains through carboxyl and hydroxyl moieties as revealed by the 1H and solid state 13C NMR spectroscopy. The protons in carboxylic and hydroxylic groups (those proton signals are characteristic of HAs with different origins) disappeared in the HA–Sb composite; and relative changes were observed in aliphatic proton distribution between the HA samples with and without Sb. The overall patterns of 13C NMR spectra for the investigated samples were analogous to each other; moreover, it was estimated that the cyclic structure of the HA nucleus remained unchanged during Sb (III) association. Based on the absorption edge energy and coordination numbers, Sb oxidation state in a native soil was interpreted as pentavalent, meanwhile the HA–Sb composite contained both Sb (III) and Sb (V). It was shown that HA catalyzes Sb (III) oxidation to Sb (V) but the process was relatively slow. However, XAFS spectra sensitivity was limited when studying the HA–Sb composite that was prepared from the isolated soil HA fraction, so only data on the first shell Sb–O coordination were interpreted.
Ligand exchange spectrophotometric method for the determination of mole ratio in metal complexes
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Fotouh R. Mansour, Neil D. Danielson
An innovative ligand exchange method involving the displacement of Fe(III) or Cu(II) ion by a ligand such as EDTA from the corresponding metal-salicylate complex has been developed to determine the mole ratio of the metal-ligand complex. The validity of the method is ascertained as the overlay of the plot showing the decrease in the absorbance of 1.0mM Fe(III)-salicylate upon the addition of serial concentrations of EDTA (0.1–0.6mM) with the absorbance calibration curve of Fe(III)-salicylate. At the intersection point of the two lines, the ratio of the two parts of the x-axis to the left and to the right of the intersection point is equal to 1:1, the mole ratio of Fe(III)-EDTA. Two other different concentrations (0.9 and 1.1mM) of Fe(III)-salicylate are used to confirm our method using the same concentration range of EDTA with each. The analysis of variance (ANOVA) is applied to compare the three slopes where no significant difference is observed with confidence limit of 95%. This method for the determination of metal complex mole ratios is compared with the reported methods known as Job, Mole Ratio, Bent-French, Asmus, and Nash. The mole ratios for Fe(III)-citrate, Cu(II)-citrate, and Cu(II)-EDTA complexes are also determined. Application to many transition metals which also complex with salicylate or related aromatic ligands is envisioned.
Source:Microchemical Journal, Volume 103
Fotouh R. Mansour, Neil D. Danielson
An innovative ligand exchange method involving the displacement of Fe(III) or Cu(II) ion by a ligand such as EDTA from the corresponding metal-salicylate complex has been developed to determine the mole ratio of the metal-ligand complex. The validity of the method is ascertained as the overlay of the plot showing the decrease in the absorbance of 1.0mM Fe(III)-salicylate upon the addition of serial concentrations of EDTA (0.1–0.6mM) with the absorbance calibration curve of Fe(III)-salicylate. At the intersection point of the two lines, the ratio of the two parts of the x-axis to the left and to the right of the intersection point is equal to 1:1, the mole ratio of Fe(III)-EDTA. Two other different concentrations (0.9 and 1.1mM) of Fe(III)-salicylate are used to confirm our method using the same concentration range of EDTA with each. The analysis of variance (ANOVA) is applied to compare the three slopes where no significant difference is observed with confidence limit of 95%. This method for the determination of metal complex mole ratios is compared with the reported methods known as Job, Mole Ratio, Bent-French, Asmus, and Nash. The mole ratios for Fe(III)-citrate, Cu(II)-citrate, and Cu(II)-EDTA complexes are also determined. Application to many transition metals which also complex with salicylate or related aromatic ligands is envisioned.
Evaluation of the effect of six different paint cross section preparation methods on the performances of Fourier Transformed Infrared microscopy in attenuated total reflection mode
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
S. Prati, F. Rosi, G. Sciutto, R. Mazzeo, D. Magrini, S. Sotiropoulou, M. Van Bos
The purpose of the present research was to compare the effect of different embedding and polishing procedures on the performances achievable with Fourier Transformed Infrared (FTIR) microscopy in Attenuated Total Reflection (ATR) mode. The attention was specifically focused on this technique since it is generally considered one of the most appropriate methods to analyze cross sections, thanks to the fact that the recorded spectra are similar to those collected in transmission mode. The research work was structured as a round robin among six different conservation and research laboratories. They were asked to embed fragments derived from the same area of a real sample following each one a different procedure. The performances of FTIR microscopy in ATR mode were evaluated on the different cross sections, considering the cross section morphology and the possible source of contamination. The cross sections were previously observed with optical microscopy, Environmental Scanning Electron Microscope (ESEM) and confocal microscopy. Three procedures were eventually selected, because they provided the best results in terms of both limiting the contamination of the embedding medium and achieving good contact with the ATR crystal. They were: a) embedding in KBr; b) cyclododecane pre-treatment before embedding in an organic resin and cutting of the sample; c) embedding in an organic resin and polishing with argon ion milling. These three procedures were finally compared and the weak points outlined, indicating where improvements could be made for further researches.
Source:Microchemical Journal, Volume 103
S. Prati, F. Rosi, G. Sciutto, R. Mazzeo, D. Magrini, S. Sotiropoulou, M. Van Bos
The purpose of the present research was to compare the effect of different embedding and polishing procedures on the performances achievable with Fourier Transformed Infrared (FTIR) microscopy in Attenuated Total Reflection (ATR) mode. The attention was specifically focused on this technique since it is generally considered one of the most appropriate methods to analyze cross sections, thanks to the fact that the recorded spectra are similar to those collected in transmission mode. The research work was structured as a round robin among six different conservation and research laboratories. They were asked to embed fragments derived from the same area of a real sample following each one a different procedure. The performances of FTIR microscopy in ATR mode were evaluated on the different cross sections, considering the cross section morphology and the possible source of contamination. The cross sections were previously observed with optical microscopy, Environmental Scanning Electron Microscope (ESEM) and confocal microscopy. Three procedures were eventually selected, because they provided the best results in terms of both limiting the contamination of the embedding medium and achieving good contact with the ATR crystal. They were: a) embedding in KBr; b) cyclododecane pre-treatment before embedding in an organic resin and cutting of the sample; c) embedding in an organic resin and polishing with argon ion milling. These three procedures were finally compared and the weak points outlined, indicating where improvements could be made for further researches.
A sensitive method for extraction and determination of endocrine-disrupting compounds from wastewater using 10-ethyl-acridone-2-sulfonyl chloride as pre-column labeling reagent by high-performance liquid chromatography with fluorescence detection
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Shijuan Zhang, Jinmao You, Zhiwei Sun, Cuihua Song, Shujing Ning, Changsheng Zhao, Yourui Suo
A sensitive pre-column derivatization method using 10-ethyl-acridone-2-sulfonyl chloride (EASC) as pre-column labeling reagent followed by high-performance liquid chromatography (HPLC) with fluorescence detection has been developed for the determination of eight endocrine-disrupting compounds: 4-octylphenol, 4-nonylphenol, bisphenol A, diethylstilbestrol, estrone, 17α-ethynylestradiol, 17β-estradiol and estriol in wastewater samples. Solid phase extraction (SPE) with ODS C18 cartridges was used for the extraction and purification. Derivatizing parameters including pH value, temperature and concentration of EASC, as well as types of SPE cartridges and eluents were investigated in detail. Under optimal conditions, the quantification limits for the desired compounds ranging from 1.0 to 2.0ngL−1 were obtained. The recoveries were higher than 80.4% with a noticeable improvement for 4-octylphenol and 4-nonylphenol, whose recoveries were usually lower than 50% during the SPE process. The proposed method was successfully applied to the determination of the target compounds in wastewater samples with a much higher sensitivity than traditional HPLC method.
Source:Microchemical Journal, Volume 103
Shijuan Zhang, Jinmao You, Zhiwei Sun, Cuihua Song, Shujing Ning, Changsheng Zhao, Yourui Suo
A sensitive pre-column derivatization method using 10-ethyl-acridone-2-sulfonyl chloride (EASC) as pre-column labeling reagent followed by high-performance liquid chromatography (HPLC) with fluorescence detection has been developed for the determination of eight endocrine-disrupting compounds: 4-octylphenol, 4-nonylphenol, bisphenol A, diethylstilbestrol, estrone, 17α-ethynylestradiol, 17β-estradiol and estriol in wastewater samples. Solid phase extraction (SPE) with ODS C18 cartridges was used for the extraction and purification. Derivatizing parameters including pH value, temperature and concentration of EASC, as well as types of SPE cartridges and eluents were investigated in detail. Under optimal conditions, the quantification limits for the desired compounds ranging from 1.0 to 2.0ngL−1 were obtained. The recoveries were higher than 80.4% with a noticeable improvement for 4-octylphenol and 4-nonylphenol, whose recoveries were usually lower than 50% during the SPE process. The proposed method was successfully applied to the determination of the target compounds in wastewater samples with a much higher sensitivity than traditional HPLC method.
Novel turbidimetric method to study polymer swelling
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Leah Oxenford, Mariya Kim, Necati Kaval, Marcus Benjamin, W.R. Seitz
The swelling behavior of pH sensitive polymer particles has been investigated by embedding the particles in a polyvinylalcohol (PVA) hydrogel membrane. Changes of one-half of an absorbance unit in the turbidity of the hydrogel membrane were observed as a result of the swelling and shrinking of the polymer particle in response to changes in the pH of the solution in contact with the membrane. The PVA membrane responded to multiple swelling and shrinking cycles without loss of functionality. This approach to studying polymer swelling is not subject to the mechanical problems of delamination and/or cracking associated with polymers immobilized on surfaces as the polymer particles embedded in the hydrogel membrane are free to swell in all directions. The membrane not only serves as a flexible medium to contain the polymer particles but also acts as a filter to protect the swellable polymer from sample components such as suspended particles that are too large to diffuse through the membrane. Because membrane turbidity can be measured at any wavelength, inexpensive instrumentation can be used to study polymer swelling.
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Leah Oxenford, Mariya Kim, Necati Kaval, Marcus Benjamin, W.R. Seitz
The swelling behavior of pH sensitive polymer particles has been investigated by embedding the particles in a polyvinylalcohol (PVA) hydrogel membrane. Changes of one-half of an absorbance unit in the turbidity of the hydrogel membrane were observed as a result of the swelling and shrinking of the polymer particle in response to changes in the pH of the solution in contact with the membrane. The PVA membrane responded to multiple swelling and shrinking cycles without loss of functionality. This approach to studying polymer swelling is not subject to the mechanical problems of delamination and/or cracking associated with polymers immobilized on surfaces as the polymer particles embedded in the hydrogel membrane are free to swell in all directions. The membrane not only serves as a flexible medium to contain the polymer particles but also acts as a filter to protect the swellable polymer from sample components such as suspended particles that are too large to diffuse through the membrane. Because membrane turbidity can be measured at any wavelength, inexpensive instrumentation can be used to study polymer swelling.
Simple mercury speciation analysis by CVG-ICP-MS following TMAH pre-treatment and microwave-assisted digestion
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Yi Wu, Yong-Ill Lee, Li Wu, Xiandeng Hou
A simple method was proposed for mercury cold vapor generation (CVG) in tetramethylammoniumhydroxide (TMAH) solution for speciation analysis of ultratrace inorganic mercury and total mercury in biological samples by inductively coupled plasma mass spectrometry (ICP-MS). Prior to analysis, 100–300mg of the biological sample was accurately weighed into a conical tube. Then, 2mL of 25% (m/v) TMAH solution was added to the sample, incubated at room temperature for several hours (hair, 3h), and diluted to 25mL with water. Finally, inorganic mercury was directly determined by CVG-ICP-MS, while microwave-assisted oxidation with H2O2 was needed for total mercury detection. The concentration of organic mercury, mainly methylmercury, was obtained by difference of total mercury and inorganic mercury. Only one calibration curve against mercury aqueous standards in 2% TMAH medium was needed for both procedures. Optimum conditions for mercury CVG, as well as sample preparation and microwave-assisted digestion were investigated in detail. A limit of detection (LOD, 3σ) of 3ngL−1 was obtained and the linear working range was 0.1–100μgL−1. Validation data were provided based on the analysis of water samples, as well as a CRM human hair sample (GBW 070601). This is a simple, rapid, ultrasensitive and relatively green method for the determination of mercury in water and biological samples.
Source:Microchemical Journal, Volume 103
Yi Wu, Yong-Ill Lee, Li Wu, Xiandeng Hou
A simple method was proposed for mercury cold vapor generation (CVG) in tetramethylammoniumhydroxide (TMAH) solution for speciation analysis of ultratrace inorganic mercury and total mercury in biological samples by inductively coupled plasma mass spectrometry (ICP-MS). Prior to analysis, 100–300mg of the biological sample was accurately weighed into a conical tube. Then, 2mL of 25% (m/v) TMAH solution was added to the sample, incubated at room temperature for several hours (hair, 3h), and diluted to 25mL with water. Finally, inorganic mercury was directly determined by CVG-ICP-MS, while microwave-assisted oxidation with H2O2 was needed for total mercury detection. The concentration of organic mercury, mainly methylmercury, was obtained by difference of total mercury and inorganic mercury. Only one calibration curve against mercury aqueous standards in 2% TMAH medium was needed for both procedures. Optimum conditions for mercury CVG, as well as sample preparation and microwave-assisted digestion were investigated in detail. A limit of detection (LOD, 3σ) of 3ngL−1 was obtained and the linear working range was 0.1–100μgL−1. Validation data were provided based on the analysis of water samples, as well as a CRM human hair sample (GBW 070601). This is a simple, rapid, ultrasensitive and relatively green method for the determination of mercury in water and biological samples.
An analytical approach based on X-ray diffraction, Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry to characterize Egyptian embalming materials
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Jeannette Jacqueline Łucejko, Anna Lluveras-Tenorio, Francesca Modugno, Erika Ribechini, Maria Perla Colombini
An analytical approach based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) was used to characterize Egyptian embalming materials from the University of Florence's (Italy) Natural History Museum. FTIR was used as a fast fingerprinting tool due to its ability to characterize inorganic compounds and to highlight different classes of organic materials. GC/MS following alkaline hydrolysis, solvent extraction, and trimethylsilylation was used to determine the molecular nature of organic materials and their degradation products. The results show that the embalming materials consisted of complex mixtures of natural products as well as transformation products due both to natural ageing and human interventions. FTIR analyses, along with evidence of organic materials, enabled us to identify the presence of calcium oxalates, phosphates and carbonates, while XRD patterns confirmed the crystalline nature of both phosphates and oxalates. On the basis of the GC/MS identification of specific profiles of long-chain fatty acids, long-chain alcohols and alkanes, polycyclic terpene hydrocarbons and diterpenes, and triterpenes, we found that the balms of the mummies mainly consisted of beeswax, pine pitch and mastic resin. Ricinoleic acid suggests that castor oil was used as an ingredient in the mummification balm in three of the samples. The combination of results allowed the identification of the organic and inorganic composition of the residue of embalming material sampled from the skulls to be achieved and also permitted us to exclude the presence of possible products used during past restoration cure.
Source:Microchemical Journal, Volume 103
Jeannette Jacqueline Łucejko, Anna Lluveras-Tenorio, Francesca Modugno, Erika Ribechini, Maria Perla Colombini
An analytical approach based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) was used to characterize Egyptian embalming materials from the University of Florence's (Italy) Natural History Museum. FTIR was used as a fast fingerprinting tool due to its ability to characterize inorganic compounds and to highlight different classes of organic materials. GC/MS following alkaline hydrolysis, solvent extraction, and trimethylsilylation was used to determine the molecular nature of organic materials and their degradation products. The results show that the embalming materials consisted of complex mixtures of natural products as well as transformation products due both to natural ageing and human interventions. FTIR analyses, along with evidence of organic materials, enabled us to identify the presence of calcium oxalates, phosphates and carbonates, while XRD patterns confirmed the crystalline nature of both phosphates and oxalates. On the basis of the GC/MS identification of specific profiles of long-chain fatty acids, long-chain alcohols and alkanes, polycyclic terpene hydrocarbons and diterpenes, and triterpenes, we found that the balms of the mummies mainly consisted of beeswax, pine pitch and mastic resin. Ricinoleic acid suggests that castor oil was used as an ingredient in the mummification balm in three of the samples. The combination of results allowed the identification of the organic and inorganic composition of the residue of embalming material sampled from the skulls to be achieved and also permitted us to exclude the presence of possible products used during past restoration cure.
Prediction of mold contamination from microbial volatile organic compound profiles using head space gas chromatography/mass spectrometry
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Nikhil Mirjankar, Ryan LeBouf, Alan Rossner
A set of volatile organic compound (VOC) profiles was developed with corresponding bioaerosol measurements as input–output pairs for a discriminant to predict mold exposure in indoor environments. Entech Bottle-Vacs were used to collect whole air grab samples while viable spores were collected concurrently using an Andersen impactor in conjunction with malt extract agar and dichloran glycerol 18. By comparing the bioaerosol data to VOC profiles that were obtained using a GC/MS equipped with a cold trap preconcentrator, a discriminant was developed to classify a residence as to potential mold growth based on its microbial volatile organic (MVOC) profile.
Source:Microchemical Journal, Volume 103
Barry K. Lavine, Nikhil Mirjankar, Ryan LeBouf, Alan Rossner
A set of volatile organic compound (VOC) profiles was developed with corresponding bioaerosol measurements as input–output pairs for a discriminant to predict mold exposure in indoor environments. Entech Bottle-Vacs were used to collect whole air grab samples while viable spores were collected concurrently using an Andersen impactor in conjunction with malt extract agar and dichloran glycerol 18. By comparing the bioaerosol data to VOC profiles that were obtained using a GC/MS equipped with a cold trap preconcentrator, a discriminant was developed to classify a residence as to potential mold growth based on its microbial volatile organic (MVOC) profile.
Electrochemical immunoassay based on gold nanoparticles and reduced graphene oxide functionalized carbon ionic liquid electrode
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Sheng Yu, Xiaoyu Cao, Meng Yu
In this paper, a gold nanoparticle, reduced graphene oxide (R-GO) and poly(l-Arginine) composite material modified carbon ionic liquid electrode (CILE) was used as the platform for the construction of a new electrochemical carcinoembryonic antigen (CEA) immunosensor. The poly(l-Arginine)/R-GO composite film was used to modify CILE to fabricate Arg/R-GO/CILE through electropolymerization of l-Arginine on R-GO/CILE. Gold nanoparticles (AuNPs) were adsorbed on the modified electrode to immobilize the CEA antibody and to construct the immunosensor. The stepwise assembly process of the immunosensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). By combining the specific properties such as the biocompatibility and big surface area of AuNPs, and the excellent electron transfer ability of R-GO and the high conductivity of CILE, the synergistic effects of composite increased the amounts of CEA antibody adsorbed on the electrode surface and then resulted in the great increase of the electrochemical responses. Under the optimal conditions, differential pulse voltammetric responses of [Fe(CN)6]3−/4− were proportional to CEA concentration in the range from 0.5 to 200ngmL−1 with the detection limit as 0.03ngmL−1 (S/N=3). The proposed immunosensor showed good reproducibility, selectivity, and acceptable stability.
Source:Microchemical Journal, Volume 103
Sheng Yu, Xiaoyu Cao, Meng Yu
In this paper, a gold nanoparticle, reduced graphene oxide (R-GO) and poly(l-Arginine) composite material modified carbon ionic liquid electrode (CILE) was used as the platform for the construction of a new electrochemical carcinoembryonic antigen (CEA) immunosensor. The poly(l-Arginine)/R-GO composite film was used to modify CILE to fabricate Arg/R-GO/CILE through electropolymerization of l-Arginine on R-GO/CILE. Gold nanoparticles (AuNPs) were adsorbed on the modified electrode to immobilize the CEA antibody and to construct the immunosensor. The stepwise assembly process of the immunosensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). By combining the specific properties such as the biocompatibility and big surface area of AuNPs, and the excellent electron transfer ability of R-GO and the high conductivity of CILE, the synergistic effects of composite increased the amounts of CEA antibody adsorbed on the electrode surface and then resulted in the great increase of the electrochemical responses. Under the optimal conditions, differential pulse voltammetric responses of [Fe(CN)6]3−/4− were proportional to CEA concentration in the range from 0.5 to 200ngmL−1 with the detection limit as 0.03ngmL−1 (S/N=3). The proposed immunosensor showed good reproducibility, selectivity, and acceptable stability.
Analytical methods for the determination of 137Cs and 90Sr in ash of fuel pellets used in Italy
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Donatella Desideri, Alba Rongoni, Carla Roselli, Daniela Saetta, Laura Feduzi
In this study the radiological characterization of ashes of 22 different brands of wood pellets coming from different countries and used in the regions of central Italy was carried out. 137Cs and 90Sr, were found in the samples taken into account, 134Cs resulted always below the detection limit. 137Cs activity concentration ranges from 30 to 3176Bqkg−1 (the arithmetic mean resulted to 571Bqkg−1); 90Sr activity concentration ranges from 154.75Bqkg−1 to 1443.70Bqkg−1 (the arithmetic mean resulted to 684.80Bqkg−1). The ratio of 90Sr and 137Cs activity concentration ranged from 0.22 to 40.79 showing a high variability. 77.2% of the samples show a 90Sr activity concentration higher than that of 137Cs. The concentration factors (activity concentration in ash/activity concentration in wood pellets) resulted to 222.8 and 230.0 for 137Cs and 90Sr respectively; both radionuclides are found completely in the ashes.
Source:Microchemical Journal, Volume 103
Donatella Desideri, Alba Rongoni, Carla Roselli, Daniela Saetta, Laura Feduzi
In this study the radiological characterization of ashes of 22 different brands of wood pellets coming from different countries and used in the regions of central Italy was carried out. 137Cs and 90Sr, were found in the samples taken into account, 134Cs resulted always below the detection limit. 137Cs activity concentration ranges from 30 to 3176Bqkg−1 (the arithmetic mean resulted to 571Bqkg−1); 90Sr activity concentration ranges from 154.75Bqkg−1 to 1443.70Bqkg−1 (the arithmetic mean resulted to 684.80Bqkg−1). The ratio of 90Sr and 137Cs activity concentration ranged from 0.22 to 40.79 showing a high variability. 77.2% of the samples show a 90Sr activity concentration higher than that of 137Cs. The concentration factors (activity concentration in ash/activity concentration in wood pellets) resulted to 222.8 and 230.0 for 137Cs and 90Sr respectively; both radionuclides are found completely in the ashes.
Rapid screening of poly(ethylene glycol) polymers by C18 column-flow injection with piezoelectric detection system
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
María R. Plata, Ana M. Contento, Ángel Ríos
A rapid and low cost analytical method for the screening and determination of poly(ethylene glycol)s polymers has been developed. Several initial studies were carried out in order to demonstrate the utility of a piezoelectric quartz crystal as a detection system for the quantification of poly(ethylene glycol)s. The method involves the use of a simple flow injection device connected to a piezoelectric quartz crystal detector. Several parameters associated with the simple flow injection manifold were optimized. Subsequently, this detector was coupled to a C18 column and the best experimental conditions were investigated in order to perform the screening and determination of poly(ethylene glycol)s. The applicability of this method, as an analytical screening tool, was demonstrated by the characterization of samples with different molecular mass polymers without using HPLC and CE techniques to carry out oligomer separations. A standard curve to determine the polymer content was obtained by relating the resonance frequency shift and polymer concentration, which showed good linearity and good regression coefficients. The working range, repeatability, limit of detection and recovery were all acceptable for the analysis of the poly(ethylene glycol)s. Finally, the proposed method was applied to determine these polymers in several samples, such as pharmaceutical products, washing powder, detergents and a body spray.
Source:Microchemical Journal, Volume 103
María R. Plata, Ana M. Contento, Ángel Ríos
A rapid and low cost analytical method for the screening and determination of poly(ethylene glycol)s polymers has been developed. Several initial studies were carried out in order to demonstrate the utility of a piezoelectric quartz crystal as a detection system for the quantification of poly(ethylene glycol)s. The method involves the use of a simple flow injection device connected to a piezoelectric quartz crystal detector. Several parameters associated with the simple flow injection manifold were optimized. Subsequently, this detector was coupled to a C18 column and the best experimental conditions were investigated in order to perform the screening and determination of poly(ethylene glycol)s. The applicability of this method, as an analytical screening tool, was demonstrated by the characterization of samples with different molecular mass polymers without using HPLC and CE techniques to carry out oligomer separations. A standard curve to determine the polymer content was obtained by relating the resonance frequency shift and polymer concentration, which showed good linearity and good regression coefficients. The working range, repeatability, limit of detection and recovery were all acceptable for the analysis of the poly(ethylene glycol)s. Finally, the proposed method was applied to determine these polymers in several samples, such as pharmaceutical products, washing powder, detergents and a body spray.
Instrumental neutron activation analysis of some fish species from Danube River in Romania
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Ana Pantelica, Antoaneta Ene, Iulia I. Georgescu
Instrumental neutron activation analysis (INAA) was applied to determine elemental concentrations in some fish species collected frome the Romanian sector of Danube River at km 1049, near the entrance in Romania (Carassius auratus gibelio, Ctenopharingodon idella, Rutilus rutilus and Silurus glanis) and km 630 (Acipenser ruthenus). Concentration values of 32 elements (Ag, As, Au, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, K, La, Lu, Na, Ni, Rb, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, U, W, Zn and Zr) in calcined fish samples were obtained based on long half-life radionuclides. Bioaccumulation factors (BAF) in fresh fish relative to Danube water (km 1049) were assessed and compared with literature data.
Source:Microchemical Journal, Volume 103
Ana Pantelica, Antoaneta Ene, Iulia I. Georgescu
Instrumental neutron activation analysis (INAA) was applied to determine elemental concentrations in some fish species collected frome the Romanian sector of Danube River at km 1049, near the entrance in Romania (Carassius auratus gibelio, Ctenopharingodon idella, Rutilus rutilus and Silurus glanis) and km 630 (Acipenser ruthenus). Concentration values of 32 elements (Ag, As, Au, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, K, La, Lu, Na, Ni, Rb, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, U, W, Zn and Zr) in calcined fish samples were obtained based on long half-life radionuclides. Bioaccumulation factors (BAF) in fresh fish relative to Danube water (km 1049) were assessed and compared with literature data.
Microchemistry and stable isotope systematics of gold mineralization in a gabbro–diorite complex, SE Egypt
11 April 2012,
09:16:24
Publication year:
2012
Source:Microchemical Journal, Volume 103
Basem Ahmed Zoheir
Electron probe micro-analysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data of ore minerals from the Um Eleiga deposit (SE Egypt) suggest that primary Au was sequestered within Ni–pyrrhotite and Co–Ni–Fe sulfarsenide, while refined, free-milling gold grains (~93wt.% Au) are associated with late pyrite, or occur along micro-fractures in quartz veins. A magmatic source of gold is most likely, yet endowment by circulating metasomatic fluid was crucial for Au concentration. Sulfur stable isotope values (δ34S) of sulfide minerals disseminated in the quartz veins (pyrite: −0.5 to 1.5‰, chalcopyrite: −0.3 to 0.6‰, and sphalerite: −0.1 to −0.4‰), indicate a generally light sulfur source. Similarly, measured δ13C of vein calcite (−3.1 to −1.8, n=9) and calculated fluid δ13CCO2 values (−0.6 to 0.6‰, for the temperature range 350–375°C of associated hydrothermal chlorite) cluster around 0‰, consistent with a magmatic source for carbon. Oxygen isotope data for vein calcite (10.3–13‰, n=9) and quartz (11.7–14.3‰, n=10) indicate average fluid δ18OH2O values of 7.4 and 7.8‰, respectively, which implicate fluids similar to those in intrusion-related systems.
Source:Microchemical Journal, Volume 103
Basem Ahmed Zoheir
Electron probe micro-analysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data of ore minerals from the Um Eleiga deposit (SE Egypt) suggest that primary Au was sequestered within Ni–pyrrhotite and Co–Ni–Fe sulfarsenide, while refined, free-milling gold grains (~93wt.% Au) are associated with late pyrite, or occur along micro-fractures in quartz veins. A magmatic source of gold is most likely, yet endowment by circulating metasomatic fluid was crucial for Au concentration. Sulfur stable isotope values (δ34S) of sulfide minerals disseminated in the quartz veins (pyrite: −0.5 to 1.5‰, chalcopyrite: −0.3 to 0.6‰, and sphalerite: −0.1 to −0.4‰), indicate a generally light sulfur source. Similarly, measured δ13C of vein calcite (−3.1 to −1.8, n=9) and calculated fluid δ13CCO2 values (−0.6 to 0.6‰, for the temperature range 350–375°C of associated hydrothermal chlorite) cluster around 0‰, consistent with a magmatic source for carbon. Oxygen isotope data for vein calcite (10.3–13‰, n=9) and quartz (11.7–14.3‰, n=10) indicate average fluid δ18OH2O values of 7.4 and 7.8‰, respectively, which implicate fluids similar to those in intrusion-related systems.
Sounds very interesting! I will check this out! l-arginine effects
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