A new headspace gas chromatographic method for the determination of methanol content in paper materials used for food and drink packaging

Liquid-Metal-Assisted Synthesis of Patterned GaN Thin Films for High-Performance UV Photodetectors Array

GaN's outstanding physical characteristics allow for a wide range of applications in numerous industries. Although individual GaN-based ultraviolet (UV) photodetectors are the subject of in-depth research in recent decades, the demand for photodetectors array is rising as a result of advances in optoelectronic integration technology. However, as a prerequisite for constructing GaN-based photodetectors array, large-area, patterned synthesis of GaN thin films remains a certain challenge. This work presents a facile technique for pattern growing high-quality GaN thin films for the assembly of an array of high-performance UV photodetectors. This technique uses UV lithography, which is not only very compatible with common semiconductor manufacturing techniques, but also enables precise patterning modification. A typical detector has impressive photo-response performance under 365 nm irradiation, with an extremely low dark current of 40 pA, a high Ilight /Idark ratio over 105 , a high responsivity of 4.23 AW-1 , and a decent specific detectivity of 1.76 × 1012 Jones. Additional optoelectronic studies demonstrate the strong homogeneity and repeatability of the photodetectors array, enabling it to serve as a reliable UV image sensor with enough spatial resolution. These outcomes highlight the proposed patterning technique's enormous potential.

Accurate Determination of Moisture Content in Flavor Microcapsules Using Headspace Gas Chromatography

This study demonstrates an accurate method for determining the moisture content in flavor microcapsules using headspace gas chromatography. The method involves measuring the gas chromatography signals of water from vapor in a headspace vial containing flavor microcapsules at a temperature of 125 °C. The measurements were recorded over four headspace extractions, from which the moisture content in the microcapsule samples was extrapolated via simple vapor-phase calibration. The results revealed that the proposed method demonstrated good precision (a relative standard deviation of <3.11%) and accuracy. The proposed method is accurate, highly sensitive, automated, and suitable for testing the moisture content of flavor microcapsules and related products.

Modeling and prediction of methanol air release from bleached chemi-thermo mechanical pulp board

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.

This paper reports on the modeling, prediction and evaluation approaches of methanol release from bleached chemi-thermo mechanical pulp (BCTMP) board during storage.

Solvent-saturated solid matrix technique for increasing the efficiency of headspace extraction of volatiles

Due to the slow mass transfer rate of substance in solid media, very limited amount of volatiles can be released from the solid matrix to the headspace in the static headspace analysis. Thus, low sensitivity is often the main problem of static headspace analysis of the volatiles contained in a solid sample. Here, we reported on a solvent-saturated solid matrix (SSSM) technique which successfully enhanced the headspace extraction efficiency, and improved the sensitivity of the headspace analysis of the volatiles in solid sample. By adding a small amount of high-boiling-point solvent (e.g. glycerin) onto the solid sample to form a surface-covered solvent layer, the headspace extraction efficiency can be significantly increased by up to 2.5 times higher than that of the conventional one. Based on the experimental investigation of the performance of different amounts of solvent used for the headspace extraction of volatiles in air-dried lotus flower samples, the possible mechanism for the SSSM assisted headspace extraction has been proposed and validated, which showed that a saturation point of solvent existed for a given amount of solid sample, and the maximum extraction efficiency could be obtained at this saturation point. Moreover, positive results were also achieved when applying this new technique in the headspace extraction of the volatiles to the other two solid samples, which means this newly developed technique may open up a new avenue, and also serve as a general strategy for improving the sensitivity of headspace analysis of the volatiles entrapped in solid matrices.

Mathematical equations combined with the MHE-GC method to study desorption kinetics of contaminants from food-package paper to air

Online sample incubation techniques are convenient, sensitive and safe, additionally, mathematical equations are applicative for other similar contaminants in paper.