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The present work reports on a method for the determination of hydrophobic degree of paper packaging material by tracer-assisted headspace gas chromatography. The method was based on adding 40 μL of methanol-water drop on the paper surface for 20 s. After removing the excess water by turning the sample vertically, the sample is placed in a vial and the amount of residual tracer attached on the material surface was accurately quantified by full evaporation headspace gas chromatography. The results show that the present method has a good precision (less than 4.1 %). The present method is simple and accurate and it can be an efficient tool for testing the hydrophobic degree of paper packaging material in batch. [ABSTRACT FROM AUTHOR]

This work reports on a new method for the determination of epoxy groups in epoxy resins by reaction-based headspace gas chromatography (HS-GC). After epoxy resins reacted with hydrochloric acid (HCl) solution, the remaining HCl reacted with bicarbonate solution in a closed headspace vial to form carbon dioxide that was measured by HS-GC. It was found that the first reaction can be finished in 30 min at room temperature and the second reaction, together with headspace equilibration, can be achieved within 15 min at 60 °C. The results showed that the method has a good precision and accuracy, in which the relative standard deviation in the repeatability measurement was 4.20%, and the relative differences between the data obtained by the HS-GC method and the reference method were within 8.04%. The present method is simple, efficient, and suitable for the used in the epoxy resin related research and applications. [ABSTRACT FROM AUTHOR]

This paper reported a headspace gas chromatographic (HS-GC) method for the determination of ethoxyl in ethyl cellulose. A 0.5 mL sample of hydroiodic acid (57%) was added to ∼20 mg samples in a closed headspace test vial (20mL) for 30 min at 120°C, for the quantitative cleavage of ethoxyl with hydroiodic acid (HI) to form ethyl iodide. After the reaction, the excess amount of HI in the vial was neutralized by injecting a sodium hydroxide solution, and then the ethyl iodide in the vial was determined by headspace gas chromatography using a flame ionization detector. The results showed that the method has an excellent measurement precision (RSD <0.5%) and accuracy (recovery = 98.6 ± 0.5%) for the quantification of ethoxyl content in ethyl celluloses. The present method is simple and accurate, which can be used for the efficient determination of ethoxyl substitution in ethyl cellulose related research. [ABSTRACT FROM PUBLISHER]

Abstract: This paper reports on a desiccated full evaporation headspace gas chromatographic (FE HS-GC) technique for determination of the methanol content in dilute mill effluents. Anhydrous K2CO3 was selected as the preferred salt for eliminating the water in the sample in the headspace sample vial. The results showed that the addition of 12g K2CO3 made it possible to introduce a larger sample size (up to 1mL) into the FE HS-GC measurement, thereby increasing the sensitivity of the technique. At the given equilibration temperature (105°C), a near-complete mass transfer of methanol from the liquid phase to vapor phase (headspace) was achieved within 10min. Replicate samples showed that the relative standard deviation of the method was less than 1.5%. Further, the limit of quantification (LOQ) was 0.12μg and the recovery ranged from 95 to 104%. The present method greatly improves the methanol detection sensitivity in the FE HS-GC method and has the added advantage of being simple, rapid and accurate. [Copyright &y& Elsevier]

Abstract: This paper reports a full evaporation (FE) headspace gas chromatographic (HS-GC) method for rapid determination of furfural in the biomass hydrolysate. The data show that a near-complete mass transfer of furfural in the sample from biomass hydrolysate to the vapor phase (headspace) was achieved within 3min at 105°C when a very small (<40μL) sample was added to a 20mL headspace sample vial. The acid-catalyzed furfural decomposition under these conditions was negligible. The furfural in the vapor phase was then determined by HS-GC using a flame ionization detector. The results showed that the method has an excellent measurement precision (RSD<0.5%) and accuracy (recovery=100.2±1.7%) for furfural quantification in carbohydrate hydrolysate samples. The method requires no sample pretreatment, so it is simple, rapid and accurate, and suitable for applications in lignocellulosic biomass conversion to fuel ethanol or other high value-added products. [Copyright &y& Elsevier]

Abstract: This paper reports a full evaporation (FE) headspace gas chromatographic (GC) method for rapid determination of ethanol in fermentation liquor. The data show that ethanol in the fermentation liquor was transferred to the vapor phase (headspace) almost completely within 3min at a temperature of 105°C when a very small volume (<50μL) of sample was directly added to a sealed headspace sample vial (20mL). The ethanol in the vapor phase was then measured by headspace GC using a flame ionization detector. The results show that the present method has an excellent measurement precision (RSD=1.62%) and accuracy (recovery = 98.1 (±1.76%)) for the ethanol quantification in fermentation liquors. The method requires no sample pretreatment and is very simple and rapid. [Copyright &y& Elsevier]

Abstract: This study demonstrated a headspace gas chromatographic method (HS-GC) for the determination of oxalate content in black liquor (alkaline aqueous solution of inorganic chemicals and dissolved wood species from the alkaline pulping of wood). The method described in this paper is based on the reaction between oxalic and manganese dioxide in an acidic medium, in which oxalic acid is converted to carbon dioxide that is measured with a GC using a thermal conductivity detector. The challenge in developing this method was ensuring complete conversion of oxalic acid while minimizing the contribution of side reactions between carbohydrates, lignin and manganese dioxide to the carbon dioxide measured. It was found that a complete conversion of oxalate to carbon dioxide can be achieved within 3min at a temperature of 70°C; a MnO2:C oxalate (concentration of H2C2O4 +HC2O4 − +C2O4 2−) mole ratio of 60 and H2SO4 concentration of 0.005–0.01mol/L in the headspace vial. The method can detect concentrations as low as 0.39μg of oxalate. The standard deviation was found to be 7% while recovery experiments with black liquor showed recoveries of 93–108% which were deemed acceptable for analysis of oxalate in an industrial sample such as black liquor. [Copyright &y& Elsevier]

This paper reports on a novel method for rapid determination of the degree of deacetylation (DD) of chitosan samples by headspace gas chromatography (HS-GC). In this method, overdose of an acid is added to protonate the free amino groups in chitosan, which further reacts with bicarbonate (as an alkali titrant) in a close vial. Based on measuring the HS-GC signal for CO 2 vs. the volume of HCO 3 − added by a stepwise titration, two transition points can be obtained. The DD value is calculated by net volume of HCO 3 − consumed, i.e., by the R NH 3 + groups in chitosan. The results showed that the present method has a good measurement precision (RSD < 0.82%) and accuracy (relative differences < 6.46% when compared with the results measured by a reference method). 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. Image 1 • A novel HS-GC technique was developed to quantify the DD value of chitosan. • The resulting product CO 2 is used as the indicator. • The method was based on determining two transition points from CO 2 releasing curve. • This method is accurate and suitable to be used in the batch sample analysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] A headspace GC method for testing the maximal amount of adsorbed gas in shale. [•] Mathematical equations were derived for the calculation. [•] The method is efficient and practical in shale gas evaluation. [Copyright &y& Elsevier]

Highlights: [•] A novel headspace gas chromatographic method has been developed. [•] An equation was established for calculating the K d in a wide temperature range. [•] The present method can efficiently determine the K d of the minor gases in shale. [Copyright &y& Elsevier]

Highlights: [•] Developed a new headspace gas chromatographic technique for BOD n testing. [•] The method is simple, accurate, and practical. [•] The method can perform an automatic high-throughput batch sample testing for BOD n . [Copyright &y& Elsevier]

Abstract: A headspace gas chromatographic (HS-GC) method has been developed for the determination of residual hydrogen peroxide in pulp bleaching effluents. The method is based on the reaction of hydrogen peroxide and permanganate in an acidic medium (0.1mol/L), in which hydrogen peroxide is quantitatively converted to oxygen within 10min at 60°C in a sealed headspace sample vial. The released oxygen is then determined by GC equipped with a thermal conductivity detector. The method is robust, sensitive, and accurate, with reproducibility characterized by a relative standard deviation of <0.5%, a sensitivity whose limit of quantification (LOQ) is 0.96μmol, and a demonstrated recovery ranging from 98 to 103%. Further, the method is simple, rapid, and automated. [Copyright &y& Elsevier]

• Determination of starch gelatinization temperatures by a headspace GC technique. • Measuring the tracer release from liquid during an automated temperature ramping. • The present method is simple, accurate and suitable for the batch sample testing. 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. [ABSTRACT FROM AUTHOR]

Abstract: This paper reported a full evaporation headspace gas chromatographic (GC) technique for determination of methanol content in black liquors (pulping spent liquor). In this method, a very small volume (10–20μL) of liquor sample is introduced into a headspace sample vial (20mL) and heated up to a temperature of 105°C. A near-complete mass transfer of methanol from the liquid phase to vapor phase (headspace), i.e., a full evaporation, can be achieved within 3min. The methanol in the headspace of the vial is then measured by GC. The present method is simple, rapid and accurate. [Copyright &y& Elsevier]

This article reported a new headspace gas chromatography (HS-GC) for the determination of hexavalent chromium Cr(VI) in solid waste hypochlorite treated leachates. The method was based on the reaction between Cr(VI) and an excess potassium hydrogen oxalate in a pH buffer solution in the headspace vial at 60℃, followed by HS-GC measuring the carbon dioxide produced. To eliminate the interference from hypochlorite in the leachates, two reaction times, i.e., 6 and 7 min, were selected. At pH = 1.50, it was found that the reaction of oxalate with Cr(VI) was partly achieved in 6 min and fully achieved in 7 min, and the reaction of oxalate with hypochlorite was achieved in 6 min. Based on two separate HS-GC measurement on the CO 2 signals at 6 and 7, respectively, the amount of Cr(VI) in the sample can be calculated. The results showed that the present method has a good measurement precision (RSD<4.70%) and accuracy (the recoveries were in the range of 92.5% - 107% and the relative differences were within 8.66% when compared with the data measured by the reference method). The present method can become a valuable tool in the Cr(VI) containing solid waste treatment related applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Determination of observed yield coefficient (Y obs) by headspace gas chromatography. • By in-situ measurement of the O 2 decrease and CO 2 increase in the sample vials. • The new method is simple, practical, and highly efficient. 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. [ABSTRACT FROM AUTHOR]