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Zhang C.-Y.,South China University of Technology | Li L.-L.,South China University of Technology | Chai X.-S.,South China University of Technology | Barnes D.G.,National Paper Products Quality Supervision Inspection Center
Journal of Chromatography A | Year: 2014

This study reports on a rapid method for the determination of methanol in paper-based materials by alkaline extraction, coupled with headspace analysis. Methanol partition equilibria between solid-liquid phases and vapor-liquid phases were conducted in two separate containers, from which an equation for calculating the total methanol content in the original paper sample was derived. It was found that the extraction equilibrium of methanol from solid sample could be achieved within 5. min at room temperature using a high-speed disintegrator, and a subsequent neutralization step is an effective way to prevent methanol from being regenerated at high temperature during headspace equilibration. The results showed that the relative standard deviations for reproducibility tests were in the range of 1.86-6.03%, and the recoveries were in the range of 92.3-107%. The present method is simple and practical; it can be an efficient tool for quantifying the methanol content in paper-based materials and thus play an important role in the investigation of methanol migration behavior in food and beverage packaging. © 2014 Elsevier B.V.


Hu H.-C.,South China University of Technology | Tian Y.-X.,South China University of Technology | Chai X.-S.,South China University of Technology | Chai X.-S.,National Paper Products Quality Supervision Inspection Center
Analytical Sciences | Year: 2012

This study reports on a headspace gas chromatographic method (HS-GC) for the determination of formaldehyde in sanitary napkin samples. The method is based on the reaction of formaldehyde and sodium borohydride in a concentrated potassium carbonate solution (824 g/L), in which formaldehyde is quantitatively converted to methanol at 105 oC in 45 min. The methanol from the conversion is determined by HS-GC. The repeatability of the method had a relative standard deviation of less than 4.5%; the limit of quantification (LOQ) was 1.17 μg, and the recovery ranged from 96.8-106%. The present method is simple, rapid, and accurate. It is suitable for use in the batch testing for product quality control of tissue papers during the manufacturing process and in analysis of point-of-sale samples from commercial markets. © The Japan Society for Analytical Chemistry.


Xin L.-P.,South China University of Technology | Chai X.-S.,South China University of Technology | Chai X.-S.,National Paper Products Quality Supervision Inspection Center | Barnes D.,South China University of Technology | And 2 more authors.
Journal of Near Infrared Spectroscopy | Year: 2014

This paper presents a Fourier transform near infrared spectroscopic method, coupled with principal-component analysis (PCA) and partial least-squares discriminate analysis (PLS-DA) techniques, for discriminating between paper products made of virgin fibre only and those made of virgin fibres blended with recycled fibres. The PLS-DA method was used to construct the discrimination models based on PCA. The study showed that the effects of the number of layers of samples, texture and moisture content can be reduced to acceptable levels by using >72 layers of papers, pressing them against a glass plate and subjecting the spectral data to preprocessing algorithms using standard normal variate analysis, multiplicative scattering correction and first-derivative calculations (FDC). The PLS-DA model based on an FDC transformation provided the best discrimination between the virgin-fibre samples and the samples blended with recycled fibre. The present method is non-destructive and enables a particularly fast classification response, without sample pretreatment. Above all, it does not consume chemicals and reagents or require a qualified laboratory technician and laboratory-grade facilities. Therefore, it appears to be suitable for use in identifying blended recycled-fibre tissue paper samples both at the manufacturer stage and in point-of-sale samples from commercial markets. © IM Publications LLP 2014 All rights reserved.


Hu H.-C.,South China University of Technology | Tian Y.-X.,South China University of Technology | Jin H.-J.,South China University of Technology | Chai X.-S.,South China University of Technology | And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2013

This study reports on a method for determination of methanol in paper products by headspace gas chromatography (HS-GC). The method is based on the hydrolysis of the pulp or paper matrix, using a phosphoric acid solution (42.5%) as the medium at 120 °C in 5 h (excluding air contact) in order to release matrix-entrapped methanol, which is then determined by HS-GC. Data show that, under the given conditions of hydrolysis, no methanol was formed from the methoxyl groups in the material. Reproducibility tests of the method generated a relative standard deviation of <3.5%, with recovery in the range of 93.4-102%. The present method is reliable, accurate, and suitable for use in batch testing of the methanol content in paper-related materials. The method can play an important role in addressing food safety concerns that may be raised regarding the use of paper materials in food and beverage packaging. © 2013 American Chemical Society.


Hu H.-C.,South China University of Technology | Hu H.-C.,National Paper Products Quality Supervision Inspection Center | Jin H.-J.,South China University of Technology | Jin H.-J.,National Paper Products Quality Supervision Inspection Center | And 2 more authors.
Journal of Industrial and Engineering Chemistry | Year: 2014

This paper reports an improved headspace gas chromatographic (HS-GC) technique for the determination of oxalate content in bleaching effluents. The method is based on the redox reaction between potassium iodate and oxalate, from which the carbon dioxide is generated and measured by HS-GC. The results showed that the reaction in a sulfuric acid solution (0.05. mol/L) was complete in 35. min at 95 °C. The RSD of the method in the repeatability testing was less than 4.5%, the LOQ was 0.35 μg, and the recovery ranged from 95 to 103%. The present method is simpler, more reliable, and more practical compared to the methods reported previously. © 2013 The Korean Society of Industrial and Engineering Chemistry.


He L.,South China University of Technology | Hu H.-C.,Fujian Agriculture and forestry University | Chai X.-S.,South China University of Technology | Chai X.-S.,National Paper Products Quality Supervision Inspection Center
Industrial and Engineering Chemistry Research | Year: 2016

This paper reports an attenuated total reflection-ultraviolet-visible spectroscopy technique assisted with multivariate data analysis for real-time determination of the content of dissolved cellulose during pulp xanthation. During xanthation, the dissolved cellulose fractions in the viscose dope were directly measured by this spectroscopy technique without any extra sample pretreatment. The results showed that by using orthogonal signal correction and partial least-squares regression (PLSR) techniques, a robust and accurate calibration model has been developed in which the R2, root mean squared error cross validation, and relative prediction errors are 0.9985, 0.2203, and 0.34%, respectively. The results of the dissolved cellulose content in viscose determined by this PLSR method were in good agreement with results of the iodometric titration method; that is, the relative difference is less than 3.00%. The present method is robust and suitable for the application of real-time monitoring of the content of dissolved cellulose in viscose in laboratory or industrial applications. © 2016 American Chemical Society.


Zhang S.-X.,South China University of Technology | Chai X.-S.,South China University of Technology | Chai X.-S.,National Paper Products Quality Supervision Inspection Center | He L.,South China University of Technology
Journal of Chromatography A | Year: 2016

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. © 2016 Elsevier B.V.


He L.,South China University of Technology | Chai X.-S.,South China University of Technology | Chai X.-S.,National Paper Products Quality Supervision Inspection Center
Journal of Wood Chemistry and Technology | Year: 2016

This article reports on a headspace gas chromatographic (HS-GC) technique for determining the content of α-, β-, and γ-cellulose in fully delignified pulps. In this method, the pulp sample was extracted by 17.5% and 9.45% NaOH solutions (25°C), respectively, to obtain two soluble fractions; i.e., the sum of β- and γ-cellulose and γ-cellulose. By reacting with potassium dichromate in a strong-acidic medium at 100°C for 60 min in a sealed headspace sample vial, these soluble celluloses in the filtrates were quantitatively converted to carbon dioxide. With the headspace equilibration at 60°C for 7 min, the formed carbon dioxide was measured by HS-GC and thus the content of β- and γ-cellulose in the pulp samples can be determined, from which the content of α-cellulose can also be calculated. The results showed that the present method had a good measurement precision (a relative standard deviation <2.1%) and accuracy (relative differences of <10% compared to the reference); the limit of quantification (LOQ) was 1.71%. In summary, the present method is simple, practical, and is particularly suitable for use in the batch sample analysis for determining α-, β-, and γ-cellulose content in fully delignified pulps. 2016 Copyright © Taylor & Francis Group, LLC


Zhang C.-Y.,South China University of Technology | Chai X.-S.,South China University of Technology | Chai X.-S.,National Paper Products Quality Supervision Inspection Center | Barnes D.G.,South China University of Technology
Fluid Phase Equilibria | Year: 2015

A novel method has been developed for the determination of the diffusion (D) and solid-air partition (Kd) coefficients of methanol in paper materials. The method used a solvent-assisted vapor absorption based headspace analysis technique to increase the driving force of the mass transfer process in the solid phase. Equations based on the established physical models described the process allowed the calculation of D and Kd of methanol in paper materials from the GC signals and experimental settings. The results showed that the amount of methanol transferred from the paper sheet can be significantly increased by the presence of the assisting triacetin. The solvent-assisted vapor absorption equilibrium can be obtained in 20min. The method also generated equations allowing for the calculation of D and Kd of methanol in paper materials at any temperature. The present method is simpler and quicker than the chamber methods that are in widespread use today and should be of special interest to those concerned about the impact of food and beverage packaging on human health. © 2015.


He L.,South China University of Technology | Chai X.-S.,South China University of Technology | Chai X.-S.,National Paper Products Quality Supervision Inspection Center
Industrial Crops and Products | Year: 2016

This paper reports on a headspace gas chromatographic (HS-GC) method for rapid determining the reactivity of dissolving pulps. After xanthation process, the viscose solution was acidified and degassed, and the dissolved cellulose in the viscose solution was regenerated and then oxidized by potassium dichromate in a strong-acidic solution in a sealed headspace vial. It showed that the cellulose can be completely converted to CO2 at the given reaction conditions (temperature = 100 °C, time = 60 min, K2Cr2O7 = 33.5 μmol, H2SO4 = 9000 μmol). By quantifying CO2 using HS-GC, the pulp reactivity of the sample can be indirectly determined. The result showed that the present method has a good repeatability (with a relative standard deviation (RSD) less than 3.7%) and a good accuracy (the differences were less than 5.0% compared to the reference method). The limit of quantitation (LOQ) of the method was 8.78%. In summary, the present method is rapid, simple, and suitable for determining the reactivity of dissolving pulps in both laboratory or industrial applications. © 2016 Elsevier B.V.

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