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Determining the methanol partition coefficient (K ow ) in octanol/water system is important to assess the risk of its impact to humans and the environment. In this paper, we report a novel method for the determination of the K ow of methanol with headspace gas chromatography (HS-GC), using a three-phase equilibrium-based phase ratio variation approach. Three headspace vials with different phase ratios [(1) 0.2 mL of water plus 3 mL of octanol, (2) 1 mL of water plus 3 mL of octanol and (3) 1 mL of water plus 10 mL of octanol] were used in the experiment. After pre-standing at 25 °C for > 10 h and equilibrating in the headspace oven at a temperature of interest for additional 25 min, the methanol signals of the vapor phase (i.e., the headspace) in these vials were measured by HS-GC, from which the K ow of methanol can be calculated based on the established equations. The results showed that the method has good precision (within 0.06 log unit in standard deviation) and acceptable accuracy (with method error within 0.5 log unit). A correlation between the K ow of methanol and temperature extrapolated the K ow values in a temperature range of interest. The present method represents a simple and in-situ approach for the determination of the K ow of methanol and is also suitable to be applied to other volatile compounds., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

This paper reports on a new method for simultaneously determining the amphiphobicities of material surface by a dual-indicator assisted headspace gas chromatography. After adding 40 μL of both methanol-water and toluene-oil droplets on the sample surface for 20 s, the sample was turned vertically (to remove water and oil) and then placed in a headspace vial. The amount of methanol and toluene in the residual water and oil adhered to material surface was quantified using headspace gas chromatography. The results showed that the method has good measurement precision (RSD < 4.58%). It can be an effective tool for simultaneously determining the amphiphobicities of material surface., Competing Interests: Declaration of Competing Interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled., (Copyright © 2021. Published by Elsevier B.V.)

This paper reports a new method for the determination of sludge water content by a multiple headspace extraction gas chromatographic (MHE-GC) method. It is based on measuring the GC signals for the water vapor in a sample vial from the first five headspace extractions, from which the water content in the sludge sample can be extrapolated according to the established calculation equation. The results show that the method has a good repeatability (the relative standard deviation is less than 1%) and accuracy. The maximum relative difference is less than 16% compared to the reference method. The present method is very simple and efficient, and suitable for rapid sample testing in related applications.

This paper reported a headspace gas chromatography (HS-GC) for the determination of denitrifying enzyme activity in soil samples. It was based on measuring the NO 2 signal in a set of closed/air-free vials containing soil samples that incubated at the designated conditions. The results showed that the method has a good measurement precision (RSD < 5.0%) and reasonable accuracy for determining the denitrifying enzyme activity in soil samples. It is simple and efficient, and very suitable to be used in batch sample analysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This paper reported a new method for the determination of the water distribution in sludge. It was based on a multiple headspace extraction (MHE) procedure to step-wise remove the water vapor from a closed vial containing a sludge sample, followed by a gas chromatographic measurement (GC). By plotting the GC signal of water vapor vs. the headspace extraction number, three different trend lines from the profile can be observed. From which two transition points can be determined and thus the stages for the free water, capillary water, and adsorption water release can be divided. Based on the sum of GC peak areas ate each stage, the content of these water types in the sludge can be calculated through a method calibration. The results showed that the MHE-GC method has a better measurement repeatability (RSD < 18.6%) and sensitivity (limit of quantitation = 0.028%) than the thermal drying method (used as a reference method). There was also a good agreement between the MHE-GC and the reference method on the free water and capillary water analysis. Moreover, the results on the adsorption water and bound water testing by the present method is more justifiable than the reference method., Competing Interests: Declaration of Competing Interest No conflict of interest exists in the submission of this manuscript, and the manuscript is approved by all authors for publication. I would like to declare on behalf of my co-authors that the work described was original research that has not been published previously, and not under consideration for publication elsewhere. All the authors listed have approved the manuscript that is enclosed., (Copyright © 2020. Published by Elsevier B.V.)

This paper describes a headspace gas chromatographic (HS-GC) method for the in-situ determination of the observed yield coefficient (Y obs ) of aerobic activated sludge from domestic wastewater treatment plants. It is based on the measurement of oxygen and carbon dioxide in samples that have been incubated in headspace vials for relatively short periods of time. The method has good precision (the relative standard deviation < 5.46%) and accuracy (the relative differences < 9.23% when compared with the data from the reference method). The new method is much simpler and more efficient than the reference methods and should greatly facilitate the testing in aerobic activated sludge related applications, such as system design, operation and management., (Copyright © 2019. Published by Elsevier B.V.)

This paper reports on a headspace gas chromatographic method (HS-GC) for the accurate determination of dissolved oxygen (DO) in domestic and industrial wastewater. It was based on GC measurement of oxygen in the headspace gas that is released from the dissolved oxygen in a liquid sample in a closed vial. The results show that the relative standard deviation of the method in quintuplicate testing was < 2.0% and the relative differences of results were less than 4.0% for the real river water samples when compared with the widely used reference method (the electrode method); The linear range of the method is about 0-9.0 mg/L with the limit of detection of 0.30 mg/L. The present method is simple in both sample preparation and method calibration. It is particularly efficient in the batch testing mode. Overall, the method is more reliable than the current reference method when used with samples from a wide range of sources., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This paper reported a novel method for the determination of total phosphorus (TP) content in soil and sludge by a headspace gas chromatography (HS-GC) method. It was based on a reaction between the soluble phosphate in the digestion solution and calcium oxalate solid to form a calcium phosphate precipitate and release oxalate ions, which can react with permanganate to form carbon dioxide, which was then measured by HS-GC. The results showed the complete conversion of phosphate (meanwhile to free oxalate ions in calcium oxalate) in 15 min at 60 °C. The present method has good repeatability (RSD < 2.6%) and good accuracy (RD < 7.3%) compared to the reference method. Therefore, the present HS-GC method can become a more effective method for determining the TP content in soil and sludge samples., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A full-cellulose derived hydrogel, composed of carboxymethyl cellulose (CMC) and nanofibrillated cellulose (NFC), was successfully manufactured and immobilized with Pd/Fe bimetallic nanoparticles for the dechlorination of 2,4,6-trichlorophenol. The NFC-reinforced CMC hydrogels with or without loading of bimetallic nanoparticles were characterized by Fourier transform infrared spectroscopy, Transmission electron microscopy, Scanning electron microscopy-energy dispersive X-ray, and X-ray diffraction analyses. The effect of amounts of NFC on the loading capacity of Pd/Fe, mechanical properties and specific Brunauer-Emmett-Teller surface areas of NFC-reinforced CMC hydrogel was also investigated. The experimental results showed that Pd/Fe bimetallic nanoparticles were dispersed and fixed in the hydrogel matrix with the nanosize spherical shape. The hydrogel would protect the Pd/Fe nanoparticles from oxidation, and thus providing long-term stability in comparison with only NFC-coated Pd/Fe nanoparticles. The hydrogel loaded with Pd/Fe nanoparticles, as a soft material catalytic system, was investigated to dechlorinate 2,4,6-trichlorophenol and was found to be very effective.

This paper reports on an automated temperature-programmed headspace GC technique for the determination of gelatinization temperature of starch. 1-butanol was used as a tracer and added to the starch-solution for the test. Based on measuring the GC signal of 1-butanol in the headspace with the temperature increasing, two transition points (corresponding to the onset temperature and the ending temperature of starch gelatinization) were observed by plotting the GC signal of 1-butanol vs. the temperature. The results showed that the method has a good measurement precision (the standard deviation < 1 °C) and accuracy (the average relative differences = 3.9%, compared to a standard reference method). The present method is simple and suitable for the gelatinization temperature testing for starch samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This study reported a new headspace gas chromatography (HS-GC) for simultaneously determining the degree of deacetylation (DD) and the degree of substitution (DS) in carboxymethyl chitosan (CMCS), which were based on HS-GC measuring the amounts of CO 2 released from both the bicarbonate decomposition suppressed by -NH 2 and the reaction between the bicarbonate and the acidified carboxymethyl and amino groups in CMCS. The results showed that the present method has a good measurement precision (RSD < 2.55%) and accuracy (relative differences <5.90%). Compared with the current titration-based method, the present HS-GC techniques provide a more reliable testing in the quantification of amino and carboxymethyl contents in CMCS. Moreover, since the HS-GC can perform an automated sample reaction equilibration and measurement, it could be much more efficient than the existing methods in the batch sample analysis.

In this study, a dual-wavelength spectroscopic method for rapid determination of organic matter in sludge was developed. The contents of the organic matter were calculated by determining the consumption of potassium dichromate (K 2 Cr 2 O 7 ) based on the production of trivalent chromium ions (Cr 3+ ). Cr 3+ could be determined by subtracting the absorption at 800 nm (spectral interference) from the absorption at 650 nm (only contributed by Cr 3+ ). The results showed that the relative standard deviation in the test was less than 5%. The same set of samples was used and when the content of organic matter was more than 150 g kg -1 , the relative difference between the spectroscopic method and titration method was within 1%. Furthermore, the method does not require calibration based on the standard samples. In conclusion, the present method is simple, reliable, accurate and suitable for application in mass testing for sludge samples., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Herein, we report a rapid screening method for evaluating the hydrocarbon contamination in paper samples by headspace gas chromatography (HS-GC). This method was based on conducting the near-complete migratable release of hydrocarbons from a paper matrix to the headspace in 35 min at 98 °C. By programming the GC column temperature, other co-existing volatile organic compounds in the sample can be effectively separated from the migratable hydrocarbons. To simplify the method calibration, the concept of total migratable hydrocarbons was introduced and n -pentadecane was used as the standard hydrocarbon compound in the calibration. The results indicate that the present method offers good precision (the relative standard deviation < 9.8%) and accuracy (recovery between 94.3 and 101%). The present method can be a valuable tool for the quality assessment of total migratable hydrocarbons of paper products, aiming at providing a good guidance for safely using the recycled paper-based materials in various applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This study demonstrated a novel method for determining the melting point (MP) of industrial grade alkyl ketene dimer (AKD) wax by an automated headspace gas chromatographic (HS-GC) technique, in which methanol was used as the tracer. It was based on measuring the GC signal of methanol released from an aqueous solution during the temperature increasing. When the temperature of AKD MP reached, the AKD granules floated on the surface aqueous solution was liquidized and completely isolated the methanol transfer from the solution to the headspace. Thus, a transition point, corresponding to the MP of AKD wax, was observed when plotting the GC signal of methanol vs. the temperature. The results showed that the method has a good measurement precision (RSD < 0.68%) and accuracy (the relative differences were < 7.16%, compared to a reference method). The present method is simple, accurate and particularly suitable to be used in the batch sample testing. This new measurement concept can be also adopted to many related applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: To evaluate the effect of Fuzheng Kang'ai Formula (, FZKA) plus gefitinib in patients with advanced non-small cell lung cancer with epidermal growth factor receptor (EGFR) mutations., Methods: A randomized controlled trial was conducted from 2009 to 2012 in South China. Seventy chemotherapynaive patients diagnosed with stage IIIB/IV non-small cell lung cancer with EGFR mutations were randomly assigned to GF group [gefitinib (250 mg/day orally) plus FZKA (250 mL, twice per day, orally); 35 cases] or G group (gefitinib 250 mg/day orally; 35 cases) according to the random number table and received treatment until progression of the disease, or development of unacceptable toxicities. The primary endpoint [progression-free survival (PFS)] and secondary endpoints [median survival time (MST), objective response rate (ORR), disease control rate (DCR) and safety] were observed., Results: No patient was excluded after randomization. GF group had significantly longer PFS and MST compared with the G group, with median PFS of 12.5 months (95% CI 3.30-21.69) vs. 8.4 months (95% CI 6.30-10.50; log-rank P<0.01), MST of 21.5 months (95% CI 17.28-25.73) vs. 18.3 months (95% CI 17.97-18.63; log-rank P<0.01). ORR and DCR in GF group and G group were 65.7% vs. 57.1%, 94.3% vs. 80.0%, respectively (P>0.05). The most common toxic effects in the GF group and G group were rash or acne (42.8% vs. 57.1%, P>0.05), diarrhea (11.5% vs. 31.4%, P<0.05), and stomatitis (2.9% vs. 8.7%, P>0.05)., Conclusion: Patients with advanced non-small cell lung cancer selected by EGFR mutations have longer PFS, MST with less toxicity treated with gefitinib plus FZKA than gefitinib alone.

We report a simple and automated headspace gas chromatographic technique for the determination of the softening point of rosin. A lumpy solid of rosin is added into a headspace vial, then an automated stepwise temperature ramping and headspace sampling was performed at each temperature stage and gas chromatography measurement. By plotting the gas chromatography signal for an impurity in rosin versus the temperature, a transition point (corresponding to the rosin softening point) was determined. The results show that the present method has a good precision (<0.76%), and good accuracy (the relative differences compared to the ring and ball method was <4.0%). The present method is simple, accurate, and automated. It is practical and suitable for testing the softening of rosin and derivatives in mills., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This paper reports on the modeling, prediction and evaluation approaches of methanol release from bleached chemi-thermo mechanical pulp (BCTMP) board during storage. A pseudo-first order desorption kinetics model of methanol release was established for describing the desorption behavior of methanol from BCTMP, i.e. , , in which the desorption constant ( K ) and rate constant ( k des ) were well described by van't Hoff and Arrhenius equations. Based on the simulation experiments at various temperatures, the desorption activation energy of methanol and its adsorption enthalpy is calculated and is 53.7 and -86.2 kJ mol -1 K -1 , respectively. With the developed model, the risk of methanol release for the storage of BCTMP board can be examined by either the time-dependent kinetics model or a two-step thermodynamic approach using the equilibrium concentration of methanol in indoor air. This paper provides a valuable tool to assess the risk of methanol release for the paper industry and related warehouse departments., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

This work reports on a simple method for the determination of lysine content by an in situ sample pretreatment and headspace gas chromatographic measurement (HS-GC) technique, based on carbon dioxide (CO 2 ) formation from the pretreatment reaction (between lysine and ninhydrin solution) in a closed vial. It was observed that complete lysine conversion to CO 2 could be achieved within 60 min at 60 °C in a phosphate buffer medium (pH = 4.0), with a minimum molar ratio of ninhydrin/lysine of 16. The results showed that the method had a good precision (RSD < 5.23%) and accuracy (within 6.80%), compared to the results measured by a reference method (ninhydrin spectroscopic method). Due to the feature of in situ sample pretreatment and headspace measurement, the present method becomes very simple and particularly suitable to be used for batch sample analysis in lysine-related research and applications. Graphical abstract The flow path of the reaction and HS-GC measurement for the lysine analysis.

We report on a headspace gas chromatographic method for determining the content of 3-chloro-1,2-propanediol in polyamideamine epichlorohydrin resin solution. It was based on quantitatively converting 3-chloro-1,2-propanediol to formaldehyde by periodate oxidation in a closed headspace sample vial at a room temperature for 10 min, and then to methanol by borohydride reduction at 90°C for 40 min followed by the headspace gas chromatographic measurement. The results showed that the present method has an excellent measurement precision (relative standard deviation < 2.60%) and accuracy (recoveries from 96.4-102%) in 3-chloro-1,2-propanediol analysis. The limit of quantitation was 0.031 mg/mL. It is simple and suitable for determining the 3-chloro-1,2-propanediol content in polyamideamine epichlorohydrin resin solution., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This work investigated the biological activities and nitrogen and phosphorus removal during the anabaena flos-aquae biofilm growth on the polyvinyl chloride (PVC) carriers, in different nutrient form mediums. The study showed that the production of dehydrogenase activity (DHA) and extracellular polymeric substances (EPS) can reach 40.4 g/(h·m 2 ) and 115 × 10 -2  g/m 2 in an 11-day period, respectively, indicating that the anabaena flos-aquae biofilm had high biological activities. The results showed that the nitrogen and phosphorus removal reached 94.9 and 96.8%, respectively, in the ammonium form nitrogen group; while 97.7% of phosphorus were removed in the orthophosphate form phosphorous group. A comparison study was conducted and results showed that the present anabaena flos-aquae based biofilm provided a better removal of nitrogen and phosphorus than the other microalgae biofilms., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In this study, we reported on the nano-scale nickel/iron particles loaded in carboxymethyl/nanofibrillated cellulose (CMC/NFC) hydrogel for the dechlorination of o-dichlorobenzene (DCB) in aqueous solution. The biodegradable hydrogel may provide an ideal supporting material for fastening the bimetallic nano-scale particles, which was examined and characterized by TEM, SEM-EDX, FT-IR and BET. The performance of the selected bimetallic particles was evaluated by conducting the dechlorination of DCB in the solution under different reaction conditions (e.g., pH, dosage of nickel/iron nanoparticles and temperature). The results showed that about 70% of DCB could be dechlorinated at 20 °C in 8 h, which indicated that the immobilized reactive material had a high reduction activity when Ni/Fe loading dosage in the hydrogel (18 wt%) was considered. Moreover, the reduction behavior agreed to the pseudo-first order reaction, in which the dechlorination rate was irrelative to the pH aqueous solution. A kinetic model for predicting the concentration of DCB during the reduction reaction was established based on the experimental data., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This paper reports on a high-throughput headspace gas chromatographic method (HS-GC) for the determination of nitrite content in water sample, based on GC measurement of cyclohexene produced from the reaction between nitrite and cyclamate in a closed vial. The method has a relative standard deviation of <3.5%; The differences between the results of the nitrite measurements obtained by this method and those of a reference method were less than 5.8% and the recoveries of the method were in the range of 94.8-102% (for a spiked nitrite content range from 0.002 to 0.03 mg/L). The limit of detection of the method was 0.46 μg L -1 . Due to an overlapping mode in the headspace auto-sampler system, the method can provide an automated and high-throughput nitrite analysis for the surface water samples. In short, the present HS-GC method is simple, accurate, and sensitive, and it is very suitable to be used in the batch sample testing., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This paper reports on an ionic-liquid assisted headspace gas chromatographic (HS-GC) for the determination of the content of alkyl ketene dimer (AKD) in its latex samples, in which the GC system was equipped with a thermal conductivity detector (TCD). The method was based on the AKD hydrolysis conducted in 1-butyl-3-methylimidazolium chloride (ionic-liquid) added medium at 100°C for 10min in a closed headspace sample vial, and the measured CO 2 (the resulting product of the hydrolysis) by HS-GC. The results showed that the present method has a good measurement precision (RSD <2.3%) and accuracy (recoveries from 96 - 105%), and the limit of quantitation (LOQ) is 0.9%. The present method is very suitable to be used for the routine check of AKD content in its latex sample in mill applications. The study also showed that the content of AKD in the tested commercial latex samples were in the range of 3.5-12%., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this study, a reutilization of caustic lye during cold caustic extraction (i.e., CCE) process to produce high-purity dissolving pulp and high-concentrated hemicellulose solution was proposed. The results showed that the lye can be reused about 12 times for producing high-purity dissolving pulps. With the number of CCE stages of 12, the hemicellulose in the lye can be auto-concentrated to about 37g/L. The alkali efficiency of the modified CCE process was about 6 (or 3) times better than the traditional CCE process with low- (or middle-) consistency of pulps. Therefore, the present process is feasible to be used for the purification of dissolving pulps with a cost-effective manner., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Five levels (180 m, 175 m, 165 m, 155 m, and 140 m) in a typical drawdown area in Wangjiagou in the Three Gorges Reservoir were selected to study CH 4 emissions from subtropical reservoirs. The experimental period lasted two years from September 2010 to August 2012. The methods of static opaque chambers during the drainage period and floating chambers during flooding period were used in this study. The elevations of 175 m, 165 m, and 155 m were all located in the drawdown area, whereas the 180 m elevation was located in the land and never flooded. The 140 m elevation was permanently flooded and used as a control area. The results showed that the CH 4 fluxes showed no significant trends at 175 m and 165 m in the first year of the experiment, while the fluxes showed a single peak pattern with the climax in the summer at 155 m and 140 m. At 175 m, the CH 4 emissions showed a single peak pattern with the climax during its flooding period, and then showed not regular CH 4 emission sources or sinks alternately in the second year, whereas the CH 4 fluxes at 165 m, 155 m, and 140 m presented a single-peak shape with winter climax. During the entire observation period, the CH 4 emission fluxes at 180 m were stable and showed no obvious peaks. In addition, CH 4 fluxes were higher during the flooding period than in the drainage period at 175 m, 165 m, and 155 m.The order of the annual CH 4 cumulative emissions at the five elevations was 140 m (99.58 kg·hm -2 ) > 155 m (82.98 kg·hm -2 ) > 165 m (65.38 kg·hm -2 ) > 180 m (6.32 kg·hm -2 ) > 175 m (4.27kg·hm -2 ), suggesting that the soil was more conducive to CH 4 production when the flooding period was longer. Correlation analysis indicated that there were no significant correlations between CH 4 fluxes and the soil carbon component and pH on land and during the drainage period but CH 4 fluxes increased with the increase in soil water content. There was a significant linear negative correlation between CH 4 emissions from the gas-water interface at 140 m and in water. The soil moisture content was one of the key factors affecting the CH 4 fluxes during the drainage period, while during flooding period, the CH 4 fluxes were regulated by flooding depth.

This paper reports on a new method for the determination of swelling capacity of superabsorbent polymers by a volatile tracer-assisted headspace gas chromatography (HS-GC). Toluene was used as a tracer and added to the solution for polymers swelling test. Based on the differences of the tracer partitioned between the vapor and hydrogel phase before and after the polymer's swelling capacity, a transition point (corresponding to the material swelling capacity) can be observed when plotting the GC signal of toluene vs. the ratio of solution added to polymers. The present method has good precision (RSD<2.1%) and good accuracy, in which the relative deference between the data measured by the HS-GC method and the reference method were within 8.0%. The present method is very suitable to be used for testing the swelling capacity of polymers at the elevated temperatures., (Copyright © 2017 Elsevier B.V. All rights reserved.)

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 CO 2 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.

The present work reports on the development of a pressure-affected based headspace (HS) analytical technique for the determination of calcium carbonate content in paper samples. By the acidification, the carbonate in the sample was converted to CO 2 and released into the headspace of a closed vial and then measured by gas chromatography (GC). When the amount of carbonate in the sample is significant, the pressure created by the CO 2 affects the accuracy of the method. However, the pressure also causes a change in the O 2 signal in the HS-GC measurement, which is a change that can be used as an indirect measure of the carbonate in the sample. The results show that the present method has a good precision (the relative standard deviation<2.32%), and good accuracy (the relative differences compared to a reference method was<5.76%). Coupled with the fact that the method is simple, rapid, and accurate, it is suitable for a variety of applications that call for the analysis of high carbonate content in paper samples., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A quint-wavelength UV spectroscopy for rapid determination of dichlorobenzene (DCB), chlorobenzene (CB) and benzene (B) was developed for the dechlorination process of DCB reduced by nanoscale zero-valent Fe/Ni bimetal. Based on the absorbance measurements at 260, 269, 277, 290 and 300nm, the equations for calculating the concentration of DCB and CB and B were established, in which the spectral interference from the nanoparticles could be effectively minimized. The results show that the present method has a good measurement precision (the relative standard deviations are within 2.0%) and accuracy (the recoveries are between 89 and 111%) in the DCB, CB and B's quantification. The present method is simple, rapid, and such a methodology is very suitable to be used for evaluating the dechlorination performance of chlorinated aromatic compounds in the presence of bimetal nanoparticle., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study demonstrated a headspace gas chromatographic (HS-GC) method for the determination of residual epichlorohydrin (ECH) and the by-product 1,3-dichloro-2-propanol (DCP) in polyamine epichlorohydrin (PAE) solution. It was based on the vapor-liquid phase equilibrium of these analytes at 60°C for 30min in a closed headspace sample vial before GC measurement. It was found that matrix of the PAE solution had the effect on the headspace equilibrium of these species and therefore a standard addition must be applied in the method validation. The results showed that the present method has a good measurement precision (RSD <2.90%) and accuracy (recoveries from 93.6 to 105%), and the limit of quantitation (LOQ) is 3.75mg/L for ECH and 0.8g/L for DCP. The present method is suitable to be used for analyzing the chlorinated volatile organic compounds in the commercial PAE resin solutions., (Copyright © 2017 Elsevier B.V. All rights reserved.)

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., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This work reports on a method for the determination of residual acrylic acid (AA) in the superabsorbent polymers for hygiene products by headspace analysis. It was based on water extraction for the polymer sample at a room temperature for 50min. Then, the AA in the extractant reacted with bicarbonate solution in a closed headspace sample vial, from which the carbon dioxide generated from the reaction (within 20min at 70°C) was detected by gas chromatography (GC). It was found that there is adsorption partition equilibrium of AA between solid-liquid phases. Therefore, an equation for calculating the total AA content in the original polymers sample was derived based on the above phase equilibrium. The results show that the HS-GC method has good precision (RSD<2.51%) and good accuracy (recoveries from 93 to 105%); the limit of quantification (LOQ) was 373mg/kg. The present method is rapid, accurate, and suitable for determining total residual acrylic acid in a wide variety of applications from processing of superabsorbent polymer to commercial products quality control., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In order to understand the changes of dissolved carbon and dissolved nitrogen in the water of Three Gorges Reservoir,this research was carried out once a week by the bank of Yangtze River in Fuling beach from March 2011 to August 2012,and the variation characteristics of dissolved C,N composition and their source were analyzed.The results showed that the concentration of DOC ranged from 0.64 mg·L -1 to 9.07 mg·L -1 ,and had obvious seasonal change:summer >spring and autumn >winter.Annual total input of DOC was 1.78×10 9 kg,the seasonal change trend of the total input of DOC was similar to that of the concentration of DOC;The concentration of DTN ranged from 2.59 mg·L -1 to 4.35 mg·L -1 :spring >winter >summer >autumn,annual total input was 1.32×10 9 kg,the seasonal input changed in the order of summer >autumn >spring >winter,among them DON,NO 3 - -N accounted for 30.35%-63.45% and 35.87%-67.72%,respectively.DOC was affected by precipitation and air temperature,and mainly came from the exogenous input,in the spring and summer its exogenous input increased with the increase of rainfall runoff,but in the autumn and winter the endogenous contribution increased;DTN was relatively affected by human emissions and water dilution.Correlation analysis showed that there was a significant negative correlation between DOC and DON ( P <0.05),DOC/DON ratio usually reflects the source of the DOM,the DOC/DON in the water of three gorges reservoir ranged from 0.35 to 7.28,the source of DOM had obvious seasonal characteristics.DOC/DON was the highest in summer,and the DOM mainly came from watershed erosion;DOC/DON was the lowest in winter,and the DOM mainly came from living sewage and endogenous field;the DOC/DON ratios in spring and autumn were higher than those in winter and lower than those in summer,and the DOM sources included watershed erosion,living sewage and endogenous field.

This paper reports on a novel method for determining the specific surface area (SSA) of shale via headspace gas chromatography (HS-GC). The method is based on the water adsorption on the surface of shale sample after achieving phase equilibrium at an elevated temperature (i.e., heating at 125 °C for 48 h). A mathematical model shows that the SSA can be determined from the signal of the vapor water released during HS-GC analysis. The results obtained by this method correlated well (R 2 = 0.992) with data obtained by the reference BET method. Because the phase equilibrium step for multiple samples can be conducted simultaneously, and because the phase re-equilibrium step is much faster in the HS-GC measurement, the present method is more efficient for batch sample testing.

This work reports on a novel method for the determination of isocyanate groups in the related organic intermediates by a reaction-based headspace gas chromatography. The method is based on measuring the CO 2 formed from the reaction between the isocyanate groups in the organic intermediates and water in a closed headspace sample vial at 45°C for 20min. The results showed that the method has a good precision and accuracy, in which the relative standard deviation in the repeatability measurement was 5.26%, and the relative differences between the data obtained by the HS-GC method and the reference back-titration method were within 9.42%. The present method is simple and efficient and is particularly suitable to be used for determining the isocyanate groups in the batch sample analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This work reports on a method for the accurate determination of fiber water-retaining capability at process conditions by headspace gas chromatography (HS-GC) method. The method was based the HS-GC measurement of water vapor on a set closed vials containing in a given amount pulp with different amounts of water addition, from under-saturation to over-saturation. By plotting the equilibrated water vapor signal vs. the amount of water added in pulp, two different trend lines can be observed, in which the transition of the lines corresponds to fiber water-retaining capability. The results showed that the HS-GC method has good measurement precision (much better than the reference method) and good accuracy. The present method can be also used for determining pulp fiber water-retaining capability at the process temperatures in both laboratory research and mill applications., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Taking a typical drawdown area located in Wangjiagou of the Three Gorges Reservoir as the study object, four elevations 180,175,165 and 155 m were selected to explore the effect of water level change on soil microbial biomass carbon (SMBC) and microbial biomass nitrogen (SMBN). Wherein, 175,165 and 155 m elevations located in the fluctuating zone, manifested as short, medium and long-term flooding, respectively; 180 m was used as the control, located on the land and never flooded. Sampling depth in soil samples was 0-20 cm, collected once a week. The results indicated that, soil organic carbon (SOC) and total nitrogen (TN) contents at 180 m had no obvious seasonal changes, while they showed remarkable seasonal trends at 175m, which in spring and summer were significantly higher than in autumn and winter; SMBC and SMBN contents and their allocation ratio at four elevations were similar and had significant seasonal fluctuation, which were highest in autumn and lowest in summer at each elevation, indicating that in drawdown area the microbial activity and turnover rate of soil organic carbon and nitrogen were limited by the high-temperature and low-humidity soil environment in summer. Data analysis showed that, compared with the 180 m elevation, contents of SOC, TN, SMBC and microbial quotient, SMBN and its allocation proportion showed varying degrees of increase, while contents of these indexes were significantly lower than control except SMBN and its allocation proportion, meaning that compared with 180 m short and medium-term flooding was conducive to improve soil carbon, nitrogen and their turnover rate and microbial biomass, however, contents of soil carbon and nitrogen and microbial biomass carbon were significantly restricted at 155 m as soil was subjected to flooding stress, meanwhile the turnover rate of SOC was reduced. Correlation analysis implied that SMBC and SMBN had very significant negative correlation with temperature at 5 cm soil depth and pH, meaning that the two environmental factors had a strong effect on soil microbial biomass.

Three heights (180 m, 175 m and 155 m) located in a typical drawdown area in Wangjiagou of the Three Gorges Reservoir were selected for studying the N 2 O emissions from subtropical reservoirs. The experimental period lasted two years from August 2010 to August 2012. The methods of static opaque chambers during the drainage period and floating chambers during flooding period were adopted in this study. The heights of 175 m and 155 m were both located in the drawdown area, whereas the 180 m height was located in the land as a control to 175 m and 155 m. N 2 O fluxes showed clear seasonal trends at each height and remarkable differences were observed between the two years at the 180 m height. N 2 O fluxes were lowest in spring at the 180 m height. N 2 O fluxes showed a single-peak pattern with climax in summer in the first year, whereas a double-peak pattern with climax in summer and after dry-wet alternating in the next year after the highest water level of 175 m was succeeded in the Three Gorges Reservoir. N 2 O fluxes presented a single-peak shape with summer climax at the 155 m height. Additionally, N 2 O fluxes were higher during the drainage period than in the flooding period at both the 175 m and 155 m heights. The order of the annual N 2 O cumulative emissions at the three heights was 175 m (853.92 mg·m -2 ) > 180 m (336.69 mg·m -2 ) > 155 m (324.69 mg·m -2 ), and there was a notable difference between 175 m and 155 m, indicating that short-term flooding could increase N 2 O emissions but long-term flooding could restrain N 2 O emissions. Correlation analysis showed that there were no obvious relativities between N 2 O fluxes and environmental factors in the land and during the drainage period. However, N 2 O fluxes were significantly negatively correlated with water temperature and wind speed during the flooding period. Principal component analysis found that soil nutrient conditions and physicochemical properties were the most important factors for N 2 O emissions in the land, the nitrogen distribution in water was a main determinant for N 2 O emissions during the flooding period, and soil physicochemical properties and microbial activity importantly affected N 2 O emissions during the drainage period in the drawdown area.

This paper describes a new method for the rapid determination of the moisture content in paper materials. The method is based on multiple headspace extraction gas chromatography (MHE-GC) at a temperature above the boiling point of water, from which an integrated water loss from the tested sample due to evaporation can be measured and from which the moisture content in the sample can be determined. The results show that the new method has a good precision (with the relative standard deviation <0.96%), high sensitivity (the limit of quantitation=0.005%) and good accuracy (the relative differences <1.4%). Therefore, the method is quite suitable for many uses in research and industrial applications., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This study reports a new headspace gas chromatographic method (HS-GC) for the determination of water solubility of low volatility liquid organic compounds (LVLOs). The HS-GC analysis was performed on a set of aqueous solutions containing a range of concentrations of toluene-spiked (as a tracer) LVLOs, from under-saturation to over-saturation. A plot of the toluene tracer GC signal vs. the concentration of the LVLO results in two lines of different slopes that intersect at the concentration corresponding to the compound's solubility in water. The results showed that the HS-GC method has good precision (RSD <6.3%) and good accuracy, in which the relative deference between the data measured by the HS-GC method and the reference method were within 6.0%. The HS-GC method is simple and particularly suitable for measuring the solubility of LVLOs at elevated temperatures. This approach should be of special interest to those concerned about the impact of the presence of low-volatility organic liquids in waters of environmental and biological systems., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The aim of this work was to study the impact of shortening kraft pulping (KP) process integrated with extended oxygen delignification (OD) on the biorefinery process performance of eucalyptus. Data showed that using kraft pulps with high kappa number could improve the delignification efficiency of OD, reduce hexenuronic acid formation in kraft pulps. Pulp viscosity for a target kappa number of ∼10 was comparable to that obtained from conventional KP and OD process. The energy and alkali consumption in the integrated biorefinery process could be optimized when using a KP pulp with kappa number of ∼27. The process could minimize the overall methanol formation, but greater amounts of carbonate and oxalate were formed. The information from this study will be helpful to the future implementation of short-time KP integrated with extended OD process in actual pulp mill applications for biorefinery, aiming at further improvement in the biorefinery effectiveness of hardwood., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This paper reports on a novel method for the rapid determination of the shale porosity by double headspace extraction gas chromatography (DHE-GC). Ground core samples of shale were placed into headspace vials and DHE-GC measurements of released methane gas were performed at a given time interval. A linear correlation between shale porosity and the ratio of consecutive GC signals was established both theoretically and experimentally by comparing with the results from the standard helium pycnometry method. The results showed that (a) the porosity of ground core samples of shale can be measured within 30 min; (b) the new method is not significantly affected by particle size of the sample; (c) the uncertainties of measured porosities of nine shale samples by the present method range from 0.31 to 0.46 p.u.; and (d) the results obtained by the DHE-GC method are in a good agreement with those from the standard helium pycnometry method. In short, the new DHE-GC method is simple, rapid, and accurate, making it a valuable tool for shale gas-related research and applications.

This work reports on a full evaporation headspace gas chromatographic (FE HS-GC) method for simultaneously determining the ethanol (EtOH) and methanol (MeOH) content in wines. A small sample (10μL) was placed in a headspace sample vial, and a near-complete mass transfer of ethanol and methanol from the liquid sample to the vapor phase was obtained within three minutes at a temperature of 105°C, which allowed the measurement of the EtOH and MeOH content in the sample by GC. The results showed excellent precision and accuracy, as shown by the reproducibilities of 1.02% and 2.11% for EtOH and MeOH, respectively, and recoveries that ranged from 96.1% to 104% for both alcohols. The method is efficient, accurate and suitable for the determination of EtOH and MeOH in wine production and quality control., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Alkylphenol polyethoxylates (APEO), surfactants used in the production of textiles, have the potential to move from the fabric to the skin of the person wearing the clothes, posing an inherent risk of adverse health consequences. Therefore, the textile industry needs a fast, robust method for determining aqueous extractable APEO in fabrics. The currently-favored HPLC methods are limited by the presence of a mixture of analytes (due to the molecular weight distribution) and a lack of analytical standards for quantifying results. As a result, it has not been possible to reach consensus on a standard method for the determination of APEO in textiles. This paper addresses these limitations through the use of reaction-based head space-gas chromatography (HS-GC). Specifically, water is used to simulate body sweat and extract APEO. HI is then used to react the ethoxylate chains to depolymerize the chains into iodoethane that is quantified through HS-GC, providing an estimate of the average amount of APEO in the clothing. Data are presented to justify the optimal operating conditions; i.e., water extraction at 60°C for 1h and reaction with a specified amount of HI in the headspace vial at 135°C for 4h. The results show that the HS-GC method has good precision (RSD<10%) and good accuracy (recoveries from 95 to 106%) for the quantification of APEO content in textile and related materials. As such, the method should be a strong candidate to become a standard method for such determinations., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The paper reports on a novel method for rapid determination of carbonyl in lignins by headspace gas chromatography (HS-GC). The method involves the quantitative carbonyl reduction for aldehydes in 2min at room temperature or for acetones in 30min at 80°C by sodium borohydride solution in a closed headspace sample vial. After the reaction, the solution was acidified by injecting sulfuric acid solution and the hydrogen released to the headspace was determined by GC using thermal-conductivity detector. The results showed that with the addition of SiO2 powder, the reduction reaction of carbonyl groups can be greatly facilitated. The method has a good measurement precision (RSD<7.74%) and accuracy (relative error <10% compared with a reference method) in the carbonyl quantification. It is suitable to be used for rapid determination of carbonyl content in lignin and related materials., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The current national standard method GB/T 27741-2011, i.e., "quantitative determination of migratable fluorescent whitening agents-UV spectroscopy", overestimates the migratable fluorescent whitening agents (FWA) in the paper based products because of the spectral interference of the leached lignin from the cellulose fibers. To minimize such interference, a spectroscopic method based on dual-wavelength (305 and 348 nm) measurement was proposed. It was observed that the dual-wavelength spectroscopy can effectively subtract the spectral absorption contributed by the leached lignin in the extraction medium, thus more accurately determination of migratable FWA can be performed. The results showed that the present method has a relative standard deviation of 2.17%, the quantitative detection limit of 16.9 mg x kg(-1), and recovery of 98%-103%. Compared with the current alternative standard-HPLC method, the present method possesses advantages of low operation and maintenance costs, simple, and practical in application. Therefore, it is more suitable for the rapid determination of migratable FWA in the product quality control in the production process and sample examination in the commercial market.

A novel method for the determination of the diffusion coefficient (D) of methanol in water and olive oil has been developed. Based on multiple headspace extraction gas chromatography (MHE-GC), the methanol released from the liquid sample of interest in a closed sample vial was determined in a stepwise fashion. A theoretical model was derived to establish the relationship between the diffusion coefficient and the GC signals from MHE-GC measurements. The results showed that the present method has an excellent precision (RSD<1%) in the linear fitting procedure and good accuracy for the diffusion coefficients of methanol in both water and olive oil, when compared with data reported in the literature. The present method is simple and practical and can be a valuable tool for the determination of the diffusion coefficient of volatile analyte(s) into food simulants from food and beverage packaging material, both in research studies and in actual applications., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This work demonstrates a novel method for rapid determination of total solid content in viscous liquid (polymer-enriched) samples. The method is based multiple headspace extraction gas chromatography (MHE-GC) on a headspace vial at a temperature above boiling point of water. Thus, the trend of water loss from the tested liquid due to evaporation can be followed. With the limited MHE-GC testing (e.g., 5 extractions) and a one-point calibration procedure (i.e., recording the weight difference before and after analysis), the total amount of water in the sample can be determined, from which the total solid contents in the liquid can be calculated. A number of black liquors were analyzed by the new method which yielded results that closely matched those of the reference method; i.e., the results of these two methods differed by no more than 2.3%. Compared with the reference method, the MHE-GC method is much simpler and more practical. Therefore, it is suitable for the rapid determination of the solid content in many polymer-containing liquid samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)