[A Method for Determination of Migratable Fluorescent Whitening Agents in Paper Products by Dual-Wavelength UV Spectroscopy].

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.

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.

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

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.

A new method for the determination of biological oxygen demand in domestic wastewater by headspace gas chromatography.

A headspace gas chromatographic method (HS-GC) has been developed for the determination of biological oxygen demand (BOD) in the water samples from domestic wastewater treatment plants. The method is based on measuring the remaining oxygen in the headspace of the sample (that has been seeded with microorganisms) in a closed container after a period of incubation. The relative standard deviation of the method in replicate testing was <4.9%. Further, the results differed by less than 6% when compared with the widely used reference method (the ISO standard) for determining BOD5. The limit of quantification in BODn testing was about 1.8 mg/L. The new method is simple and suitable for use in the batch sample testing for BODn measurement.

Rapid determination of formaldehyde in sanitary paper napkins for product quality control by headspace gas chromatography.

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°C 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.