Diatom Frustules Decorated with Co Nanoparticles for the Advanced Anode of Li-Ion Batteries.

Silica is regarded as a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, large volume variation and poor electrical conductivity are limiting factors for the development of SiO2 anode materials. To solve this problem, combining SiO2 with a conductive phase and designing hollow porous structures are effective ways. In this work, The Co(II)-EDTA chelate on the surface of diatom biosilica (DBS) frustules and obtained DBS@C-Co composites decorated with Co nanoparticles by calcination without a reducing atmosphere is first precipitated. The unique three-dimensional structure of diatom frustules provides enough space for the volume change of silica during lithiation/delithiation. Co nanoparticles effectively improve the electrical conductivity and electrochemical activity of silica. Through the synergistic effect of the hollow porous structure, carbon layer and Co nanoparticles, the DBS@C-Co-60 composite delivers a high reversible capacity of >620 mAh g-1 at 100 mA g-1 after 270 cycles. This study provides a new method for the synthesis of metal/silica composites and an opportunity for the development of natural resources as advanced active materials for LIBs.

A fast and simple headspace gas chromatographic technique for quantitatively analyzing urea in human urine.

A fast and convenient headspace gas chromatographic (HS-GC) approach was described for the estimation of urea in human urine. The HS-GC could detect the generated carbon dioxide derived from the urease-catalyzed hydrolysis of urea. It was found that the hydrolysis of urea catalyzed by urease was completed within 40 min at 35 °C. The results proved the great accuracy (relative errors ≤ 8.48%) and precision (RSD ≤ 2.66%) of the HS-GC approach. Moreover, the recoveries ranged from 97.9% to 101.5%. The new approach is rapid and automated, which provides a new way to routinely analyze urea in urine for the control of metabolic disease.

Simple and accurate method for determining dissolved inorganic carbon in environmental water by reaction headspace gas chromatography.

We investigate a simple and accurate method for quantitatively analyzing dissolved inorganic carbon in environmental water by reaction headspace gas chromatography. The neutralization reaction between the inorganic carbon species (i.e. bicarbonate ions and carbonate ions) in environmental water and hydrochloric acid is carried out in a sealed headspace vial, and the carbon dioxide formed from the neutralization reaction, the self-decomposition of carbonic acid, and dissolved carbon dioxide in environmental water is then analyzed by headspace gas chromatography. The data show that the headspace gas chromatography method has good precision (relative standard deviation ≤ 1.63%) and accuracy (relative differences ≤ 5.81% compared with the coulometric titration technique). The headspace gas chromatography method is simple, reliable, and can be well applied in the dissolved inorganic carbon detection in environmental water.

Measurement of water absorption capacity in wheat flour by a headspace gas chromatographic technique.

The purpose of this work is to introduce a new method for quantitatively analyzing water absorption capacity in wheat flour by a headspace gas chromatographic technique. This headspace gas chromatographic technique was based on measuring the water vapor released from a series of wheat flour samples with different contents of water addition. According to the different trends between the vapor and wheat flour phase before and after the water absorption capacity in wheat flour, a turning point (corresponding to water absorption capacity in wheat flour) can be obtained by fitting the data of the water gas chromatography peak area from different wheat flour samples. The data showed that the phase equilibrium in the vial can be achieved in 25 min at desired temperature (35°C). The relative standard deviation of the reaction headspace gas chromatographic technique in water absorption capacity determination was within 3.48%, the relative differences has been determined by comparing the water absorption capacity obtained from this new analytical technique with the data from the reference technique (i.e., the filtration method), which are less than 8.92%. The new headspace gas chromatographic method is automated, accurate and be a reliable tool for quantifying water absorption capacity in wheat flour in both laboratory research and mill applications.

Utilizing two detectors in the measurement of trichloroacetic acid in human urine by reaction headspace gas chromatography.

A reaction headspace gas chromatography (HS-GC) technique was investigated for quantitatively analyzing trichloroacetic acid in human urine. This method is based on the decomposition reaction of trichloroacetic acid under high-temperature conditions. The carbon dioxide and chloroform formed from the decomposition reaction can be respectively detected by the thermal conductivity detection HS-GC and flame ionization detection HS-GC. The reaction can be completed in 60 min at 90°C. This method was used to quantify 25 different human urine samples, which had a range of trichloroacetic acid from 0.52 to 3.47 mg/L. It also utilized two different detectors, the thermal conductivity detector and the flame ionization detector. The present reaction HS-GC method is accurate, reliable and well suitable for batch detection of trichloroacetic acid in human urine.

Efficient quantification of water content in edible oils by headspace gas chromatography with vapour phase calibration.

BACKGROUND: An automated and accurate headspace gas chromatographic (HS-GC) technique was investigated for rapidly quantifying water content in edible oils. In this method, multiple headspace extraction (MHE) procedures were used to analyse the integrated water content from the edible oil sample. A simple vapour phase calibration technique with an external vapour standard was used to calibrate both the water content in the gas phase and the total weight of water in edible oil sample. After that the water in edible oils can be quantified. RESULTS: The data showed that the relative standard deviation of the present HS-GC method in the precision test was less than 1.13%, the relative differences between the new method and a reference method (i.e. the oven-drying method) were no more than 1.62%. CONCLUSION: The present HS-GC method is automated, accurate, efficient, and can be a reliable tool for quantifying water content in edible oil related products and research. © 2017 Society of Chemical Industry.

Quantitative analysis of total starch content in wheat flour by reaction headspace gas chromatography.

This paper proposed a new reaction headspace gas chromatographic (HS-GC) method for efficiently quantifying the total starch content in wheat flours. A certain weight of wheat flour was oxidized by potassium dichromate in an acidic condition in a sealed headspace vial. The results show that the starch in wheat flour can be completely transferred to carbon dioxide at the given conditions (at 100 °C for 40 min) and the total starch content in wheat flour sample can be indirectly quantified by detecting the CO2 formed from the oxidation reaction. The data showed that the relative standard deviation of the reaction HS-GC method in the precision test was less than 3.06%, and the relative differences between the new method and the reference method (titration method) were no more than 8.90%. The new reaction HS-GC method is automated, accurate, and can be a reliable tool for determining the total starch content in wheat flours in both laboratory and industrial applications. Graphical abstract The total starch content in wheat flour can be indirectly quantified by the GC detection of the CO2 formed from the oxidation reaction between wheat flour and potassium dichromate in an acidic condition.

Method for improving accuracy in full evaporation headspace analysis.

We report a new headspace analytical method in which multiple headspace extraction is incorporated with the full evaporation technique. The pressure uncertainty caused by the solid content change in the samples has a great impact to the measurement accuracy in the conventional full evaporation headspace analysis. The results (using ethanol solution as the model sample) showed that the present technique is effective to minimize such a problem. The proposed full evaporation multiple headspace extraction analysis technique is also automated and practical, and which could greatly broaden the applications of the full-evaporation-based headspace analysis.

Quantification of anhydride groups in anhydride-based epoxy hardeners by reaction headspace gas chromatography.

We demonstrate a reaction headspace gas chromatographic method for quantifying anhydride groups in anhydride-based epoxy hardeners. In this method, the conversion process of anhydride groups can be realized by two steps. In the first step, anhydride groups in anhydride-based epoxy hardeners completely reacted with water to form carboxyl groups. In the second step, the carboxyl groups reacted with sodium bicarbonate solution in a closed sample vial. After the complete reaction between the carboxyl groups and sodium bicarbonate, the CO2 formed from this reaction was then measured by headspace gas chromatography. The data showed that the reaction in the closed headspace vial can be completed in 15 min at 55°C, the relative standard deviation of the reaction headspace gas chromatography method in the precision test was less than 3.94%, the relative differences between the new method and a reference method were no more than 9.38%. The present reaction method is automated, efficient and can be a reliable tool for quantifying the anhydride groups in anhydride-based epoxy hardeners and related research.

Measurement of permanganate index in environmental water via indirect phase-conversion strategy.

In this work, we proposed an indirect phase-conversion strategy to construct a new approach for accurately and efficiently determining the permanganate index in water samples via headspace GC measurement. After the reducible substances in water reacted with excess potassium permanganate, the remaining potassium permanganate underwent a reaction with sodium oxalate under acidic conditions. The carbon dioxide generated from the gas-evolving reaction was then analyzed by headspace GC. Our findings showed that this new approach boasts high precision (relative standard deviation ≤ 2.18%) and accuracy for permanganate index analysis, thus validating the effectiveness of this new method in analyzing permanganate index. The introduction of the indirect phase-conversion strategy in this study is expected to set a precedent for further advancements in methodologies designed to indirectly evaluate substances capable of undergoing gas-producing reactions.

Quantifying sodium hypochlorite content in hypochlorite-based disinfectants via phase-conversion headspace technique.

In this work, a novel and efficient approach for sodium hypochlorite analysis is proposed via phase-conversion headspace technique, which is based on the gas chromatography (GC) detection of generated carbon dioxide (CO2) from the redox reaction of sodium hypochlorite with sodium oxalate. The data obtained by the proposed method suggest the high detecting precision and accuracy. In addition, the method has low detection limits (limit of quantification (LOQ) = 0.24 µg/mL), and the recoveries of added standard ranged from 98.33 to 101.27 %. The proposed phase-conversion headspace technique is efficient and automated, thereby offering an efficient strategy for highly efficient analysis of sodium hypochlorite and related products.

Establishing a new methodology for determining the water absorbability of cellulose-derived materials via a vapor-monitoring headspace strategy.

In this research, for the first time, we introduce a vapor-monitoring headspace strategy to establish a new methodology for determining the water absorbability of cellulose-derived materials. The method involves detecting the water in the gas phase from various cellulose-derived materials after achieving the equilibrium state. By utilizing the headspace technique to monitor the change in water vapor pressure from bound water to free water, a change point indicating the water absorbability can be identified through fitting procedures. The study showed that the newly-established method possesses high precision (relative standard deviation ≤2.92%) and accuracy (relative differences ≤5.74%) for water absorbability analysis. The present method emerges as a facile and reliable tool for measuring water absorbability, and the introduction of the vapor-monitoring headspace strategy is anticipated to inspire the development of a new type of analytical method.

MUC1 promotes glycolysis through inhibiting BRCA1 expression in pancreatic cancer.

Enhanced glucose metabolism is one of the hallmarks of pancreatic cancer. MUC1, a transmembrane protein, is a global regulator of glucose metabolism and essential for progression of pancreatic cancer. To clarify the role of MUC1 in glucose metabolism, we knocked out MUC1 in Capan-1 and CFPAC-1 cells. MUC1 knockout (KO) cells uptook less glucose and secreted less lactate with a much lower proliferating rate. The mRNA level of key enzymes in glycolysis also decreased significantly in MUC1 KO cells. We also observed increased expression of breast cancer type 1 susceptibility protein (BRCA1) in MUC1 KO cells. Since BRCA1 has a strong inhibitory effect on glycolysis, we want to know whether the decreased glucose metabolism in MUC1 KO cells is due to increased BRCA1 expression. We treated wild type (WT) and MUC1 KO cells with BRCA1 inhibitor. BRCA1 inhibition significantly enhanced glucose uptake and lactate secretion in both WT and MUC1 KO cells. Expression of key enzymes in glycolysis also elevated after BRCA1 inhibition. Elevated glucose metabolism is known to facilitate cancer cells to gain chemoresistance. We treated MUC1 KO cells with gemcitabine and FOLFIRINOX in vitro and in vivo. The results showed that MUC1 KO sensitized pancreatic cancer cells to chemotherapy both in vitro and in vivo. In conclusion, we demonstrated that MUC1 promotes glycolysis through inhibiting BRCA1 expression. MUC1 may be a therapeutic target in pancreatic cancer treatment.

A simple and rapid method for the determination of lead dioxide in minium by headspace gas chromatographic technique.

This paper demonstrated a simple and rapid approach for the determination of lead dioxide in minium using a headspace gas chromatographic (GC) technique. This new approach was based on the measurement of carbon dioxide from the redox reaction between lead dioxide and oxalic acid in a sealed headspace vial. The obtained results indicated that the new approach had good measurement accuracy (relative errors ≤8.71%) and precision (RSD ≤2.86%). Moreover, the limit of quantification (LOQ) and limit of detection (LOD) for this new approach were respectively 0.34% and 0.10%, and the recoveries ranged from 97.9 to 101.7%. The new approach is low-cost and reliable, which has potential for use in the analysis of lead dioxide in minium and related products.

An efficient headspace gas chromatographic technique for determining humic acid content in fertilizer.

A fast, convenient and commercially available approach for analyzing humic acid content in fertilizer using headspace gas chromatography (HS-GC) is presented in this paper. Humic acid is converted into carbon dioxide based on the oxidation of humic acid in strong acidic medium and can be measured via automatic HS-GC. Conditions for the alkaline extraction and the humic acid oxidation process are also optimized. The new technique proved to be precise (RSD ≤ 3.59%) and accurate (relative errors≤9.46% as compared with the spectrophotometric approach). The newly established technique presents a practical tool to routinely analyze humic acid content in fertilizer during the fertilizer production.

Determination of iodate in iodized edible salt based on a headspace gas chromatographic technique.

This paper introduces a convenient approach for determining iodate in iodized salt by headspace gas chromatography (HS-GC). The analytical technique can measure the generated carbon dioxide from the redox reaction between iodate and sodium oxalate in the presence of strong acid. The formed carbon dioxide from this reaction in a closed vial is measured by GC. It was observed that the redox reaction in the vial was completed in 40 min at 95 °C. The results indicated that this analytical technique is precise (RSD ≤ 2.69%) and accurate (relative errors ≤ 7.21%). The present approach is fast and simple, providing a robust avenue to the routine estimation of iodate in iodized salt in a wide variety of applications from processing to quality monitoring.

A double sealing technique for increasing the precision of headspace-gas chromatographic analysis.

This paper investigates a new double sealing technique for increasing the precision of the headspace gas chromatographic method. The air leakage problem caused by the high pressure in the headspace vial during the headspace sampling process has a great impact to the measurement precision in the conventional headspace analysis (i.e., single sealing technique). The results (using ethanol solution as the model sample) show that the present technique is effective to minimize such a problem. The double sealing technique has an excellent measurement precision (RSD < 0.15%) and accuracy (recovery = 99.1%-100.6%) for the ethanol quantification. The detection precision of the present method was 10-20 times higher than that in earlier HS-GC work that use conventional single sealing technique. The present double sealing technique may open up a new avenue, and also serve as a general strategy for improving the performance (i.e., accuracy and precision) of headspace analysis of various volatile compounds.

Rapid quantitative detection of glucose content in glucose injection by reaction headspace gas chromatography.

This work investigates an automated technique for rapid detecting the glucose content in glucose injection by reaction headspace gas chromatography (HS-GC). This method is based on the oxidation reaction of glucose in glucose injection with potassium dichromate. The carbon dioxide (CO2) formed from the oxidation reaction can be quantitatively detected by GC. The results show that the relative standard deviation (RSD) of the present method was within 2.91%, and the measured glucose contents in glucose injection closely match those quantified by the reference method (relative differences <6.45%). The new HS-GC technique is rapid, practical and can be used to the batch detection of the glucose content in glucose injection related applications.

Efficient determination of average valence of manganese in manganese oxides by reaction headspace gas chromatography.

This work investigates a new reaction headspace gas chromatographic (HS-GC) technique for efficient quantifying average valence of manganese (Mn) in manganese oxides. This method is on the basis of the oxidation reaction between manganese oxides and sodium oxalate under the acidic condition. The carbon dioxide (CO2) formed from the oxidation reaction can be quantitatively analyzed by headspace gas chromatography. The data showed that the reaction in the closed headspace vial can be completed in 20min at 80°C. The relative standard deviation of this reaction HS-GC method in the precision testing was within 1.08%, the relative differences between the new method and the reference method (titration method) were no more than 5.71%. The new HS-GC method is automated, efficient, and can be a reliable tool for the quantitative analysis of average valence of manganese in the manganese oxide related research and applications.

Determination of the Degree of Substitution of Cationic Guar Gum by Headspace-Based Gas Chromatography during Its Synthesis.

This study reports on a headspace-based gas chromatography (HS-GC) technique for determining the degree of substitution (DS) of cationic guar gum during the synthesis process. The method is based on the determination of 2,3-epoxypropyltrimethylammonium chloride in the process medium. After a modest pretreatment procedure, the sample was added to a headspace vial containing bicarbonate solution for measurement of evolved CO2 by HS-GC. The results showed that the method had a good precision (relative standard deviation of <3.60%) and accuracy for the 2,3-epoxypropyltrimethylammonium chloride measurement, with recoveries in the range of 96-102%, matching with the data obtained by a reference method, and were within 12% of the values obtained by the more arduous Kjeldahl method for the calculated DS of cationic guar gum. The HS-GC method requires only a small volume of sample and, thus, is suitable for determining the DS of cationic guar gum in laboratory-scale process-related applications.